# X-Spot X10 Tungsten Points?



## alithearcher (Sep 18, 2017)

First, thanks to all for the posts on the forum, I've learned a lot.

I wanted to check whether anyone has any info on the X-Spot X10 Tungsten Points. They are cheaper than Easton's and since its tungsten I thought it should be fine, but wanted to check before I pull the trigger. 
http://www.lancasterarchery.com/x-spot-x10-tungsten-points.html?cmp=cel&trigger=ac


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## dragonbn (Dec 17, 2017)

No difference honestly 


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## alithearcher (Sep 18, 2017)

Did you use them? I wonder whether it fits fine and the quality of course.


dragonbn said:


> No difference honestly
> 
> 
> Sent from my iPhone using Tapatalk


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## dragonbn (Dec 17, 2017)

Very good quality. Smacked it a couple times into a boulder and it was still alive 


Sent from my iPhone using Tapatalk


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## 10X Archer (Mar 7, 2016)

I would like to hear your opinion on them. If you haven't pulled the trigger yet, it is cheaper to buy them from the Decut Ebay store. Lancaster rebrands Decut as X-Spot.


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## airwolfipsc (Apr 2, 2008)

I have tried them..one arrow flew weird..checked and it was brittle as a shank broke. I may have hit a plywood on haybale at one time..tungsten just a waste of money.


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## driebergd (May 15, 2015)

Decut archery of China make tungsten points for x10s too. Even cheaper and just as good. Slightly more aerodynamic profile to the x10 ones. Checked all 12 on a grain scale and they were extremely accurate and consistent.


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## alithearcher (Sep 18, 2017)

Thanks all. I got them. Weights were very accurate in grains.
Fit was a bit loose (compared to Nano Pro Xtreme points) but I don't know about Easton's points, maybe they are loose too. The shape of the tungsten points worried me that they may get stuck in the targets but so far no issues.


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## alithearcher (Sep 18, 2017)

Update: Doesn't work. I lost 3 of them in foam targets. Bought Easton tungsten and no issues with them.


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## Bender (Dec 6, 2006)

Please excuse my ignorance here, but WHY use a tungsten point?

I seem to recall reading somewhere that the denser tungsten allows more leeway in playing with FOC, but I wouldn't bet on on that actually being accurate.


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## chrstphr (Nov 23, 2005)

Tungsten take more damage and bend less than a stainless steel point. Also more of the weight of the point and shank is more forward than stainless steel points.


Chris


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## Bender (Dec 6, 2006)

It must be the FOC thing then. 

Some research shows you can now get steel glue ins for up to 140 grains, while the tungsten hits 150 grains. So one the face of it you should be able to handle FOC issues with steel alone. But I imagine that the shank on the steel 140 grain point must be absurdly long. Perhaps long enough to finally affect an arrows dynamic spine behavior enough to become a shootable difference?

Did some research on the material properties tungsten vs steel as well. Tungsten is MUCH more brittle than steel. Although very hard, it will shatter and break up, under the same load that would merely bend or dent steel. 

Surely a non-issue when shooting a large target at a single known distance using a sight. VERY unlikely that one is going to damage the tungsten point. But I don't think that it would be a good choice for Field or 3D, especially unmarked 3D. One hard crash and the tungsten will shatter. Sure it will ruin the steel point as well, but that steel point didn't cost $20. Also since it will just blow up I wonder if you're more likely to wind up with a ruined shaft as well.

I think that it once again comes down to just stop and think about what EXACTLY you're building your arrow for. I've always felt that no one arrow configuration will deliver optimum performance at all venues.

Always use the proper tool for the job at hand. Right?


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## chrstphr (Nov 23, 2005)

The below is only regarding X10 arrows and the steel or tungsten points for those arrows. Not tungsten points vs steel in general.

The tungsten points have a much smaller head. The steel points are an inch long. Add to that the steel shanks being twice as long in the shaft, the weight is more forward. You get much better FOC with the tungsten without having to use higher point weight, which helps with sight marks when shooting lower poundage. 120gr tungsten will give better FOC than 120gr steel. The arrow nodes are in a different place with tunsgten as well with the much shorter shank. Long shank stiffens the front of the arrow moving the node back. 

Many archers poo poo FOC. Rightly so. Those archers dont shoot well enough to take advantage of better FOC results. No insult intended. There are many things in archery that archers dont shoot well enough to take advantage of the benefits. Many archers shooting X10s probably shouldnt shoot them. Too heavy and too expensive for the benefits. They shoot them because thats what everyone shoots, or all the top archers etc. 

X10s are great in the wind if you shoot high enough poundage to get the arrow to target with good sight marks.

While i have bent some tungsten points with hits into a rock or wood stand, i have never had one shatter. I have had steel points bend just hitting the aluminum pin of the back of an X10.

I find that you can shoot great with steel or tungsten, but its a better high end choice. The archers who question it, usually wouldnt see the difference anyway. No insult intended. 

Many are put off by the cost. That is a factor. But then again, X10s also arent for the budget conscious. 

When your shooting is refined enough that FOC matters, you will find tungsten beats steel every time. Again, no insult intended. 

Tungstens can certainly be a foolish expense for many archers. But there is a level where its an advantage, and matters. With a heavy arrow like the X10, i recommend it so the FOC is better for better cast and results in the wind. 

Is it right for you? Only you can say. But no harm or slight if you choose to shoot steel. Its affordable and will do the job. 

I recommend the Easton tungstens, not the Xspot or other brands. 



Chris


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## jmvargas (Oct 21, 2004)

am curious...do the South Koreans use tungsten...or steel??


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## archeryal (Apr 16, 2005)

While this is a non-factor for anyone not shooting in international competition, I understand some of the target butts used in Europe are rock-hard and will damage steel points (I think one material is called stramat?).


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## Bender (Dec 6, 2006)

chrstphr, well aware of the concept of the "shootable difference" so no insult taken. Usually that difference is about the shooter's abilities, but sometimes it can be about the equipment, or some combination of the two.

See? That is why I'm here. You've had hard crashes with tungsten and it didn't blow. That is good to know. 

At a guess then I would bet that the better tungsten points are made of some obscure tungsten alloy. Made up so as to make them less brittle.


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## PregnantGuppy (Jan 15, 2011)

Bender said:


> Tungsten is MUCH more brittle than steel.


That's why they don't use pure tungsten. They use tungsten carbide, which is about twice as strong as steel. It's the same material they use for many type of drill bits and other rotary tools, which definitely cannot be brittle.



> am curious...do the South Koreans use tungsten...or steel??


The guys with which I shoot use mostly tungsten. But I'm quite sure they get them for free. There's something like 10 boxes just lying around at the range, and I've seen them sweep up tungsten points with the garbage when cleaning up. Makes me want to ask if I can keep the ones they're throwing out, but I don't know how to ask for them


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## jmvargas (Oct 21, 2004)

PregnantGuppy said:


> That's why they don't use pure tungsten. They use tungsten carbide, which is about twice as strong as steel. It's the same material they use for many type of drill bits and other rotary tools, which definitely cannot be brittle.
> 
> 
> 
> The guys with which I shoot use mostly tungsten. But I'm quite sure they get them for free. There's something like 10 boxes just lying around at the range, and I've seen them sweep up tungsten points with the garbage when cleaning up. Makes me want to ask if I can keep the ones they're throwing out, but I don't know how to ask for them


i was referring to the top Koreans in the world but i guess it's a safe bet they'd be using them too if they're free..


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## chrstphr (Nov 23, 2005)

Looking at the team rounds in Shanghai and Antalya, The Korean men's team and women's team use the tungstens. In addition to Chinese Taipei and others. easy to see, the steel points are an inch long. The Tungstens about 3/8. 


Chris


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## Bender (Dec 6, 2006)

AHA! Tungsten carbide! I ran across it while looking into the material properties of tungsten, but discounted it as even I know it is an alloy. See? I thought the tungsten points were straight tungsten.


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## PregnantGuppy (Jan 15, 2011)

jmvargas said:


> i was referring to the top Koreans in the world but i guess it's a safe bet they'd be using them too if they're free..


That's what I was getting at. If the guys I know in Korea that don't even make the national team are treating tungsten points like that, you can bet that the top guys can probably fill a bathtub with the amount they have. Ultimately, between Easton wanting to make sure every medal is won with Easton arrows and Korean companies dumping money on them, there is almost no chance that they are not using tungsten points.


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## alithearcher (Sep 18, 2017)

I think the small diameter matters. Tungsten being denser is smaller on tip and inside the shaft making the arrow less likely to bend. I have broken steel points on Nanos and switching to tool steel helped a lot. I will post a picture of both points when I can. Xspot was consistent and if they make it right I'll buy them again.


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## dozy lizard (Mar 12, 2013)

PregnantGuppy said:


> That's why they don't use pure tungsten. They use tungsten carbide, which is about twice as strong as steel. It's the same material they use for many type of drill bits and other rotary tools, which definitely cannot be brittle.


Sorry to be picky, but this is wrong on almost all counts after "they don't use pure tungsten." Arrow points are usually tungsten alloy, likely tungsten/nickel. No one is saying exactly what their alloy is, but Tungsten Carbide is grey and Easton Aerojets are silvery color. Tungsten Carbide IS brittle. It is much easier to break or chip a tungsten carbide saw tooth than a high speed steel one (and saw teeth are not pure Tungsten Carbide either because pure Tungsten Carbide would be too brittle). The strength of steel varies hugely but Tungsten Carbide has less tensile strength (344 MPa) than even mild steel (370MPa yield) and much less that high tensile steel which can be over 1000MPa. The main property in which Tungsten Carbide excels is hardness, and it retains its hardness at high temperatures, which makes it excellent for the cutting edges of machine tools, but not much needed for arrow points.


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## PregnantGuppy (Jan 15, 2011)

dozy lizard said:


> Sorry to be picky, but this is wrong on almost all counts after "they don't use pure tungsten." Arrow points are usually tungsten alloy, likely tungsten/nickel. No one is saying exactly what their alloy is, but Tungsten Carbide is grey and Easton Aerojets are silvery color. Tungsten Carbide IS brittle. It is much easier to break or chip a tungsten carbide saw tooth than a high speed steel one (and saw teeth are not pure Tungsten Carbide either because pure Tungsten Carbide would be too brittle). The strength of steel varies hugely but Tungsten Carbide has less tensile strength (344 MPa) than even mild steel (370MPa yield) and much less that high tensile steel which can be over 1000MPa. The main property in which Tungsten Carbide excels is hardness, and it retains its hardness at high temperatures, which makes it excellent for the cutting edges of machine tools, but not much needed for arrow points.


No need to apologize, the correction is appreciated. I did know that pure tungsten is brittle, so it's definitely an alloy, but that's unfortunately most of the extent of my materials science knowledge. I do recall someone with more experience in the topic than me mentioned tungsten carbide, which is why I mentioned it, but apparently I either misremembered or they're not as knowledgeable as I thought they were. Thanks!


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## theminoritydude (Feb 11, 2013)

jmvargas said:


> i was referring to the top Koreans in the world but i guess it's a safe bet they'd be using them too if they're free..


If you’re referring to South Korean pro archers, a couple of them use SS points. It was told to me that the reason some of them use it, is the fact that they could feel the difference pulling the different points through the clicker and some prefer the feel of SS points.

Yeah. I’m not lying.


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## theminoritydude (Feb 11, 2013)

A few years ago, one of their coaches came for a visit and she asked me what I wanted.

I told her, “payment in tungsten.”

I was given 36 tungsten points. I rigged 140gr arrows with them and they worked flawlessly without an arrow rest.


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## MTrainer (Oct 11, 2013)

Decut made a very well made tungsten points for x-10 that I did get in SLC World Cup for less price.


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## alithearcher (Sep 18, 2017)

The package says there are actually two versions of tungsten points that they offer one with better quality (?). Funny thing is you don't know which one you got, because they didn't put any info about it on the package.


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## whiz-Oz (Jul 19, 2007)

chrstphr said:


> Many archers poo poo FOC. Rightly so. Those archers dont shoot well enough to take advantage of better FOC results. No insult intended.


Many archers also get caught up in FOC, despite there being no actual evidence that it provides any discernable advantage at regular competition distances, when researched with any scientific levels of rigour. 

But it's handy to trot out and mention if you want to impress people who don't know any better. There are a LOT of such people on this particular forum.


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## theminoritydude (Feb 11, 2013)

If indeed FOC does not provide any discernible difference, why have it at all?

Like it or not, FOC is instrumental in steering in atmosphere in partnership with fletching. An arrow that is not steered quickly enough into a a state of longitudinal streamlined airflow continues to be affected by lateral airflow and hence - drift. A high FOC provides added advantage in changing wind conditions, at the cost of a more parabolic trajectory, so the archer has to find the right balance.

A defense of tungsten. You may claim that it does not enhance significantly the FOC, but you do have to take into account the size of the exposed tip, instead of just the shaft, because when that is factored in, the difference may be more than 2 or 3 points at 70m for a single round. Plenty for elite archers.


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## whiz-Oz (Jul 19, 2007)

Really? 

So how exactly do you "factor" that in? Keeping in mind that you would have read any information about that from a link that I posted here once that research was actually published..


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## theminoritydude (Feb 11, 2013)

whiz-Oz said:


> Keeping in mind that you would have read any information about that from a link that I posted here once that research was actually published..


Well, there you go. I haven't read it. You assumed that I did.


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## theminoritydude (Feb 11, 2013)

Could we have that link here please?


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## whiz-Oz (Jul 19, 2007)

theminoritydude said:


> Well, there you go. I haven't read it. You assumed that I did.


No. I knew that you hadn't because you got it totally wrong.


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## theminoritydude (Feb 11, 2013)

Oh, whiz-oz.......


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## chrstphr (Nov 23, 2005)

whiz-Oz said:


> Many archers also get caught up in FOC, despite there being no actual evidence that it provides any discernable advantage at regular competition distances, when researched with any scientific levels of rigour.
> 
> But it's handy to trot out and mention if you want to impress people who don't know any better. There are a LOT of such people on this particular forum.


really? wow. I find it hard to believe that an arrow that has 6% FOC will do just as well at the FITA distances in the wind as an arrow with 16%. 

For that matter, why have a point weight at all. Why not just sharpen the end of the arrow tube since FOC gives no quantifiable advantage. I guess you do use a point weight in your arrow when you shoot? If so then Why? 

Why did anyone spend the time to work out FOC calculations and work out ranges? They must have been misguided due to the research you reference. 

Please show me the research that showed an arrow with very small to none FOC did just as well in arrow flight and resistance to wind as an arrow with a high FOC 12-16%. And all arrows flew equal. 

I am shocked to know i have been bamboozled into the myth of FOC. 

http://www.grizzlystik.com/PR/Ashby_EFOC.pdf

http://www.tap46home.plus.com/mechanics/

https://shootingtime.com/archery/high-foc-arrows/

http://arrowtrademagazine.com/assets/sept2010-traditionalfocusextremefrontofcenter.pdf

https://eastonhunting.com/what-is-f-o-c-and-how-does-it-affect-arrow-flight/

https://www.researchgate.net/publication/305321934_Development_and_analysis_of_arrow_for_archery

Even Easton knows what FOC is and how it works. Even they must have been bamboozled. 


Chris


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## julle (Mar 1, 2009)

A high FOC may pose as a benefit in a controlled environment, starting with being shot from a machine. However, to get a high FOC in x10's you need a pretty heavy point, resulting in a much heavier arrow. Increasing the overall weight of an arrow, generally does not improve the shot characteristics. Locktime increases, your release and bow arm becomes more finicky, etc., all eventually resulting in a lower score. I think this is where the theories collide. 
I have tested it myself, and have heard the same from top archers, a heavier point, such as the 140 grain easton tungstens lowers your score in a recurve setup shot at 70m.


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## PregnantGuppy (Jan 15, 2011)

chrstphr said:


> really? wow. I find it hard to believe that an arrow that has 6% FOC will do just as well at the FITA distances in the wind as an arrow with 16%.
> 
> For that matter, why have a point weight at all. Why not just sharpen the end of the arrow tube since FOC gives no quantifiable advantage. I guess you do use a point weight in your arrow when you shoot? If so then Why?
> 
> ...


To be fair to whiz, none of the links you posted actually answer his query. Most of them are just marketing material about defining FOC and how to change it, not research. The only research article you posted is also largely irrelevant; it is mostly about using differently shaped points, which affect FOC as a side effect. Moreover, the project didn't measure accuracy at all; it's a comparison of drag properties of the three points. So it really proves nothing in this discussion.

Once again, the only conclusion we can really draw is that we simply need more good data to be able to answer this kind of question. Obviously we know that some mass is required for stable arrow flight, but to what margin one benefits from more mass is still largely unknown.


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## tooold (Jul 26, 2015)

You want FOC - try the Black Eagle X-Impact with 140 gr points. Heavy point in an arrow 2gr per inch lighter than X10s. Nice arrow!


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## Seattlepop (Dec 8, 2003)

With FOC aren't we really talking about wind resistance, specifically cross wind resistance? A rock and feather fall at the same rate only in a vacuum. Add atmosphere and the rock prevails, i.e., mass overcomes wind resistance. You don't need heavy FOC, just heavier. In a cross wind my ACE's with 90gr points get pushed off course more than with 110gr points. It doesn't get more sciency than that.


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## theminoritydude (Feb 11, 2013)

Mass doesn’t reduce overall air resistance. What mass does, is it reduces speed. Speed is its own enemy; a fast projectile loses speed just as fast. What mass does here, is it retains its constant value in the kinetic energy quantification of 1/2M(Vsquared), where as you can see, V is not constant, and energy loss is squared. As I have mentioned before, what we are really targeting, is efficient transfer of energy from archer to target. Speed is not the entire picture.


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## Black46 (Oct 16, 2013)

Which arrows would you shoot and would you make a different choice for windy conditions?

1) 317gr, 18.1% FOC, 178fps
2) 272gr, 17.4% FOC, 187fps
3) something else...

Length and diameter are close enough to be negligable


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## chrstphr (Nov 23, 2005)

julle said:


> A high FOC may pose as a benefit in a controlled environment, starting with being shot from a machine. However, to get a high FOC in x10's you need a pretty heavy point, resulting in a much heavier arrow. Increasing the overall weight of an arrow, generally does not improve the shot characteristics. Locktime increases, your release and bow arm becomes more finicky, etc., all eventually resulting in a lower score. I think this is where the theories collide.
> I have tested it myself, and have heard the same from top archers, a heavier point, such as the 140 grain easton tungstens lowers your score in a recurve setup shot at 70m.


for some archers, using 100gr to 120gr will give high FOC. I didnt say you had to use 140gr. I currently use a 110gr point in my X10s. My FOC is above 16%. 

Chris


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## chrstphr (Nov 23, 2005)

PregnantGuppy said:


> To be fair to whiz, none of the links you posted actually answer his query. Most of them are just marketing material about defining FOC and how to change it, not research. The only research article you posted is also largely irrelevant; it is mostly about using differently shaped points, which affect FOC as a side effect. Moreover, the project didn't measure accuracy at all; it's a comparison of drag properties of the three points. So it really proves nothing in this discussion.
> 
> Once again, the only conclusion we can really draw is that we simply need more good data to be able to answer this kind of question. Obviously we know that some mass is required for stable arrow flight, but to what margin one benefits from more mass is still largely unknown.


to be fair, 

since cavemen stopped whittling and burning the end of a stick arrow, and started tying a rock point on to it, that has been the research for FOC. Putting a weight on the front end of the arrow creates FOC and better arrow flight. 

since that time, equipment has evolved, arrows have evolved, and results have shown that front weight aids in stabilization and arrow flight. They still have a point with weight on the end of an arrow. An arrow with FOC will fly better and more stable than an arrow with no FOC. An arrow with higher FOC will fly better in the wind than an arrow with lower FOC. 

There is a point where too much FOC will shorten the cast and ruin the flight. Too much of anything is not a good thing.

His post wasnt about high FOC. It was about FOC. My posts werent about high FOC. My post was about better FOC against another point on the same arrow. 

FOC is not a myth for people who dont know any better on this forum. 


Chris


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## Seattlepop (Dec 8, 2003)

theminoritydude said:


> Mass doesn’t reduce overall air resistance. *What mass does, is it reduces speed*. Speed is its own enemy; a fast projectile loses speed just as fast. What mass does here, is it retains its constant value in the kinetic energy quantification of 1/2M(Vsquared), where as you can see, V is not constant, and energy loss is squared. As I have mentioned before, what we are really targeting, is efficient transfer of energy from archer to target. Speed is not the entire picture.


Mass does not reduce speed, sorry. "An object in motion..." And my 110gr points still resist cross winds better than 90gr.


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## theminoritydude (Feb 11, 2013)

Mass does reduce the exit speed of the arrow, given the same bow, same archer. Imagine your arrow weighs a pound.........

Your 110gr resists crosswind because of its higher FOC, not mass. ----> https://www.archerytalk.com/vb/showthread.php?t=5430575&p=1108145399#post1108145399


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## theminoritydude (Feb 11, 2013)

Black46 said:


> Which arrows would you shoot and would you make a different choice for windy conditions?
> 
> 1) 317gr, 18.1% FOC, 178fps
> 2) 272gr, 17.4% FOC, 187fps
> ...


You'd have to observe the vertical spread of the groups. At the point where it equals that of the horizontal spread. That's where you want to be. Spread is subjected to the input error, and input error differ from archer to archer. In calm wind conditions.


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## Seattlepop (Dec 8, 2003)

theminoritydude said:


> *Mass does reduce the exit speed of the arrow*, given the same bow, same archer. Imagine your arrow weighs a pound.........
> 
> Your 110gr resists crosswind because of its higher FOC, not mass. ----> https://www.archerytalk.com/vb/showthread.php?t=5430575&p=1108145399#post1108145399


Mass does not reduce exit speed. Mass will exit at the speed at which it exits. Your reduction can only be compare to a lighter arrow. More mass increases FOC, but a heavier arrow with the same FOC as a lighter one will still resist cross wind deflection better.


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## theminoritydude (Feb 11, 2013)

Let me clear up the confusion.

"A higher mass arrow will exit the bow at a lower speed than a lower mass arrow." That's what I meant by "reduced speed".

Your argument for better crosswind deflection is only true because of inertia. But given the longer time spent in flight, exposed to lateral airflow, the advantages are greatly diminished.


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## Seattlepop (Dec 8, 2003)

theminoritydude said:


> Let me clear up the confusion.
> 
> "A higher mass arrow will exit the bow at a lower speed than a lower mass arrow." That's what I meant by "reduced speed".
> 
> Your argument for better crosswind deflection is only true because of inertia. But given the longer time spent in flight, exposed to lateral airflow, the advantages are greatly diminished.


And a diminished advantage is still an advantage. Sine die.


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## PregnantGuppy (Jan 15, 2011)

theminoritydude said:


> Mass doesn’t reduce overall air resistance. What mass does, is it reduces speed. Speed is its own enemy; a fast projectile loses speed just as fast. What mass does here, is it retains its constant value in the kinetic energy quantification of 1/2M(Vsquared), where as you can see, V is not constant, and energy loss is squared. As I have mentioned before, what we are really targeting, is efficient transfer of energy from archer to target. Speed is not the entire picture.


You're forgetting that mass also increases momentum. Increased momentum prevents the wind from moving the arrow as well. So you end up with a classic optimization problem: increases in mass reduce speed linearly, so time exposed to wind is increased roughly linearly, but momentum also increases linearly, which decreases the effect of wind. We'd have to run numbers to see at what point we get diminishing returns.



> His post wasnt about high FOC. It was about FOC. My posts werent about high FOC. My post was about better FOC against another point on the same arrow.
> 
> FOC is not a myth for people who dont know any better on this forum.


I mean, if you want to debate that point in particular, then yes, it's clearly true that adding some weight in front of an arrow yields a more stable arrow flight. I am certainly not arguing against that, as I mentioned in my post, and I'd be willing to give whiz the benefit of the doubt in that he wasn't arguing for that either.

But that's a boring argument, since we already know the results. Which is why I thought we were debating the more interesting topic of how much weight is good, and at what point do we not get any more significant gains. You yourself agree that too much FOC is not conducive to good shooting. But what is too much FOC? Where is the research to show that? And I don't mean air resistance research that comes as a side effect of looking at point shapes; I mean straight up FOC vs group size, or some other metric of accuracy.


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## whiz-Oz (Jul 19, 2007)

Other than one single instance about the investigation of FOC on arrow flight of any kind done by Clarence Hickman, nobody has moved the balance point of the arrow INDEPENDENTLY from the weight. 
Hickman at least used a shooting machine to investigate if FOC changed the distance potential of arrows. 

Every other time someone has investigated FOC, they've just changed the weight of the point and announced that they have changed FOC. 

Well, kiddies, that's two things that have been changed. Not one. 

If someone is SO dumb that they can't actually understand what they're testing, or use a proper testing methodology, or even be able to understand or reproduce their results, why do you continue to give them any credit? 

If I put 200 lb of pink paint on a white car and then saw it take another second to cover the standing quarter, would it be logical to insist that being pink slowed it down? 

THIS IS EXACTLY WHAT YOU GUYS ARE DOING, AFTER OVER A DECADE OF READING THIS FORUM.
This forum is an echo chamber on FOC importance where everyone likes to put their illogical, untested hopelessly biased opinions in, without being able to say anything else. No actual laboratory level research. Nobody even reads the research that has been done. People here argue about things which have ALREADY been proven to be incorrect. It's like watching preschoolers discuss that holding hands can make you pregnant.

And then you try and turn the burden of proof on me "Oh, show me the research" which is always followed by "now you need to explain it to me" and then need me to understand it for you. 

So, here's my open invitation. Go and look for any research done by Dr James Park on Google. Pay for access to it. Read it. If you can't understand it, then you shouldn't be talking about it. 

If ANY of you guys actually had a clue about this, you'd be able to relate standard terms used in other fields such as tail volume coefficients and margins of stability to FOC. 

But I've never seen anyone do that and that's because you like to stay in areas that you hope that nobody has any greater knowledge of. 

If anyone actually bothered to ask the reasons for tungsten points, you might have heard from the horses mouth that tungsten points were designed to stop X10 wear from stupid materials used for target butts. 

FOC figures are quoted by manufacturers so that acceptable stability margins for arrows are within limits of causing no issues. 

The most interesting thing about archers is that they equate ability to shoot an arrow accurately with the knowledge of the physics of archery. 
It breaks down to "I shoot better than you, so you must know nothing" or "He shoots the best, so he must know everything."

It's pretty safe to say that nobody here knows what the scientific method is, has ever used it, is a data analyst or has any background in aerodynamics or more than basic ballistics. 

What you do like to do is point at stories or articles by similarly unqualified people and say "This proves my point" and hope that you aren't actually forced into doing your own personal thinking or investigation that stands up to simple criticism. 

chrstphr - you can't personally explain what changing ONLY FOC does to the consistency potential of a arrow. 

If you can't do that, you don't know. 

This is a very simple way to separate the believers from the knowledgeable. Plenty of people are happy to believe their point of view. Most get very shirty when you ask them to back it up. 

I've been picking on FOC discussions for years. Nobody has ever come up with evidence because it doesn't yet exist. You might wonder why people believe in ghosts, but there is no proof. People believe in aliens, but they've never come to visit. 
People believe in bigfoot but everything seems to be a hoax. 

How about that? 

Anyone care to explain how FOC relates to accuracy? I'm talking FOC ONLY.


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## whiz-Oz (Jul 19, 2007)

PregnantGuppy said:


> I mean straight up FOC vs group size, or some other metric of accuracy.


Yes. 

About that extreme lack of evidence which would settle things once and forever. In a sport obsessed with accuracy, you'd think it would be cut and dried by now.


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## chrstphr (Nov 23, 2005)

whiz-Oz said:


> Other than one single instance about the investigation of FOC on arrow flight of any kind done by Clarence Hickman, nobody has moved the balance point of the arrow INDEPENDENTLY from the weight.
> Hickman at least used a shooting machine to investigate if FOC changed the distance potential of arrows.
> 
> How about that?
> ...


I can only test what i can test. 

I have a dozen easton X10 arrows. I put in 6 with the inch long stainless steel point 110gr. I put the tungsten 110gr in the other. I shoot all 12. In the wind the tungsten groups better and drifts less. FOC is better with the tungsten due to more weight forward, that is the main difference.

You being scientific would say, test invalid. You changed the point which changed the point shape. You changed where the clicker is to shoot both arrows because they now to not match in length. If i shot one arrow longer so they did match in length, you would say, test invalid. Now one shaft is longer than the other. Its easy to shoot down testing and invalidate results. I have shot X10s and McKinneys with point weights from 65gr to 150gr. I have shot X10s from 600 spine to 380 spine. I can only work with the results I get. 

How to do suppose to test to prove or disprove FOC and any benefit? 

what test is possible on a field with human archers other than what we are able to test. Its easy to sit in an armchair and postulate how there is no testing results that meet your satisfaction. You are so waiting for evidence for 10 years, where is your idea of how to test? You're so interested to pick on FOC conversations for 10 years, where is your testing to prove we are all imbeciles who shouldnt bother to try and figure FOC out? 

What is the point weight of your Easton X10 arrows? What have you found works best for shooting in the wind? How do you suggest the evidence be tested and researched since you seem to know everything about arrows and aerodynamics of archery. 

Yes, tungsten points were made by George to help with the tough UK bales. But the increased FOC from them was a win for us imbeciles who dont know chit about it. 

FOC relates to accuracy in that the better the FOC for that particular arrow and shot, the less drift in unpredictable winds. 

And i never said i shot better than anyone. On the contrary, i have found every way to shoot terribly in a tournament, I usually shoot worse than everyone. However, my students shoot great... that is the important part. 


Chris


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## whiz-Oz (Jul 19, 2007)

So, you didn't know that the standard profile Easton tungsten points increase the point at which the airflow along the arrow becomes turbulent, therefore increasing the arrows drag and INCREASING drift in unpredictable winds? 

Yes. Tested. Proven. Wind tunnel tests, scaled water flow tests with dye flow visualisation photos and all. Published. http://journals.sagepub.com/doi/abs/10.1177/1754337111430569?journalCode=pipa

And you haven't managed to explain the link between FOC and drift. You've just claimed it. 

You don't know. 

And I never said that you claimed you shot better than anyone else. 

And yes, your test is invalid. It suffers from small data size and lack of testing rigour. No record of results or ability to be duplicated due to the huge amount of variation.


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## Seattlepop (Dec 8, 2003)

"Having a high FOC for an arrow provides two principal benefits - better arrow groups and reduced wind sensitivity". Joe Tapely (http://www.tap46home.plus.com/mechanics/#)

And so ends the lesson.


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## theminoritydude (Feb 11, 2013)

I was pretty sure, the competition and medals are usually at the shooting line.


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## whiz-Oz (Jul 19, 2007)

Seattlepop said:


> "Having a high FOC for an arrow provides two principal benefits - better arrow groups and reduced wind sensitivity". Joe Tapely (http://www.tap46home.plus.com/mechanics/#)
> 
> And so ends the lesson.


And this is the Joe Tapley that argued that arrows don't have a node in flight. You should remember that. It's quite a disservice that his website stays up providing people with the wrong information. 

Pointing towards Joe as a source of reliable information is like recommending David Avocado Wolfe as a lifestyle guide. 

Go through his page and find the disclaimers.


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## Seattlepop (Dec 8, 2003)

whiz-Oz said:


> And this is the Joe Tapley that argued that arrows don't have a node in flight. You should remember that. It's quite a disservice that his website stays up providing people with the wrong information.
> 
> Pointing towards Joe as a source of reliable information is like recommending David Avocado Wolfe as a lifestyle guide.
> 
> Go through his page and find the disclaimers.


"The alignment of the arrow at launch is a line drawn through the arrow's two (hypothetical) vibrational nodes. This alignment does not have to be in the plane of the bow." - Joe Tapely. He calls them hypothetical while acknowledging the supposition of their existence useful in describing arrow flight. I don't have a problem with that. 

BTW, SafeSport training covers disrespectful, condescending, abusive behavior - you should look into it.


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## PregnantGuppy (Jan 15, 2011)

chrstphr said:


> FOC relates to accuracy in that the better the FOC for that particular arrow and shot, the less drift in unpredictable winds.


This is again stated without data. I understand that it might work well for you, and that's respectable. I personally believe that every archer should go with what works best for them, for sure. But if we're going to make sweeping statements like that, we need some sort of formal data and testing, not just a statement repeated over and over.



> "Having a high FOC for an arrow provides two principal benefits - better arrow groups and reduced wind sensitivity". Joe Tapely (http://www.tap46home.plus.com/mechanics/#)


That's the second time recently I've seen that site, but I cannot get it to work for me. None of the links seem to do anything. Am I doing something wrong here? I'd love to read what they have to say, but I just can't access anything interesting


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## waxyjaywalker (Apr 10, 2013)

PregnantGuppy said:


> That's the second time recently I've seen that site, but I cannot get it to work for me. None of the links seem to do anything. Am I doing something wrong here? I'd love to read what they have to say, but I just can't access anything interesting


I have the same problem, none of the tabs seem to do anything. I found a work-around: click on the italian flag under the home tab, it should go to the italian site. Then some of the tabs work, showing the english article most times. Sometimes it shows an italian article.


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## Seattlepop (Dec 8, 2003)

The link works fine for me. Try without the # sign: http://www.tap46home.plus.com/mechanics/


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## Seattlepop (Dec 8, 2003)

whiz-Oz said:


> So, you didn't know that the standard profile Easton tungsten points increase the point at which the airflow along the arrow becomes turbulent, therefore increasing the arrows drag and INCREASING drift in unpredictable winds?
> 
> Yes. Tested. Proven. Wind tunnel tests, scaled water flow tests with dye flow visualisation photos and all. Published. http://journals.sagepub.com/doi/abs/10.1177/1754337111430569?journalCode=pipa
> 
> ...


Perhaps you should look to your Mr. Park for the link since he recommends heavier points to increase over-all mass of an arrow:

"The total mass of the arrow also influences the wind drift, but not as strongly as the arrow’s diameter. Greater arrow mass extracts a little more energy from the bow, which then slightly reduces the drift. *Consequently it is best to use a heavier rather than a lighter arrow point"* (Emphasis added). - James Park, "Some observations from the Shanghai World Cup, 2018" (http://www.bow-international.com/features/shaft-selection-picking-the-right-arrow/)


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## nuts&bolts (Mar 25, 2005)

PregnantGuppy said:


> This is again stated without data. I understand that it might work well for you, and that's respectable. I personally believe that every archer should go with what works best for them, for sure. But if we're going to make sweeping statements like that, we need some sort of formal data and testing, not just a statement repeated over and over.
> 
> 
> 
> That's the second time recently I've seen that site, but I cannot get it to work for me. None of the links seem to do anything. Am I doing something wrong here? I'd love to read what they have to say, but I just can't access anything interesting


FOC by Joe Tapley. He is British, so a "pile" is what us Yanks call a target point of field point.

FORWARD OF CENTRE (F.O.C.)
*The FOC value for an arrow indicates how far forward of the centre of the shaft the centre of gravity (COG) is located, expressed as a percentage.

If 'L' is the length of the shaft and 'D' is the distance from the centre of the shaft to the COG then the FOC = 100 x D/L.

e.g if the arrow is 80 cm long and the FOC = 12% then the COG is 12*80/100 = 9.6 cm in front of the shaft centre.

The FOC relates to two different aspects of shooting arrows, how the arrow behaves on the bow when being shot and how the shot arrow flies through the air.

In order to hit what you are aiming at the arrow needs to come off the bow straight and with no rotation. One of the principal factors which affects how the arrow comes off the bow is how it bends when being shot ("weak/stiff arrow"). For a given draw weight, shaft weight, shaft stiffness and length of arrow shaft the main way the amount of bending is affected is by varying the pile and nock weights. The heavier the pile weight or the lighter the nock weight then the more the arrow will bend. The shaft stiffness and associated weight depend on the shaft construction e.g. carbon arrow shafts are stiffer for the same weight then aluminium shafts. For the way the arrow behaves on the bow then the FOC is a guide to what the pile weight should be for the arrow to 'match' the bow in terms of coming off straight i.e. have the right amount of arrow bending.

Manufacturers publish recommended values for the FOC e.g an FOC of 7-9% for aluminium shafts, 11-16% for ACE carbon shafts. These values are largely based on the standard pile weights available for the shaft. In practice recurve archers often use higher FOCs by e.g. using specially made heavier tungsten points.

The reason the recommended FOC values are higher for ACE then for aluminium shafts is because the carbon shaft is much lighter then the aluminium for the same shaft stiffness. As the shaft is lighter the COG is further forward & the FOC is larger.

While the FOC value is limited by how the arrow behaves on the bow it also affects how the arrow flies through the air. This is related to the arrow total drag and the fletching action. As covered in the section on drag, the drag force on an arrow is split between two separate forces; one which acts through the arrow centre of gravity which acts to move the arrow and one which acts somewhere else, roughly around where the fletchings are which acts to rotate the arrow.

If you don't want to plod through the section on drag then A Rough Guide to FOC tries to give an idea of why FOC is so important to the drag properties of an arrow. The ideal FOC value for arrow flight performance is 50% i.e. the arrow balance point is at the front of the arrow. In reality for OR archery the maximum practicable FOC is in the low 20's. The limiting factor is arrow speed. For a given arrow shaft/nock/fletching all up weight the only way to increase FOC is to increase the point weight. Problem is increasing point weight increases overall arrow weight and hence reduces arrrow speed. For best arrow performance you need the best combination of FOC and arrow speed. For example the reason for the low recommended FOC of 7-9% for aluminium arrows is not that this is a good FOC value in itself just that if you try to increase the FOC value to a higher value the arrow speed drops to an unacceptable level.Overall arrow performance is lower.

The principle drag effect on the arrow which makes you 'miss' with a bad shot or a gust of wind is the drag on the shaft. You can break the total drag force on the arrow shaft into two components, a component that acts through the arrow centre of gravity which acts only to move the arrow (no rotation) and a second component located to the rear of the COG cog which acts like a fletching to rotate the arrow. The relative size of these two forces depends on the arrow FOC. If 'L' is the length of the arrow shaft and 'A' its diameter then the total shaft drag area is LA. The shaft area Fa which relates to the shaft drag force acting through the cog is approximately given by:-

Fa = LA(1-FOC/50)

This is only an approximation because any rotation (fishtailing) of the arrow will affect arrow lateral movement and also the value of the shaft drag area.

e.g if the arrow is 80 cm long and has a 0.5 cm diameter then:-

with an FOC of 8% this shaft drag area is around 80 x 0.5(1-8/50) = 33.6 square cm

with an FOC of 16% this shaft drag area is around 80 x 0.5(1-16/50) = 27.2 square cm

or to put it another way each 1% increase in FOC reduces this shaft drag area by about 2%.

The overall fletching area with respect to how the arrow flies comprises three elements:

- the effective area of the fletchings 
- the shaft fletching area 
- vortex shedding torque (expressed as an area)

The shaft fletching area is determined by the position of the COG i.e. the value of the FOC for the arrow. The shaft fletching area = 2 x D x A = 2 x FOC x L x A / 100. ( A, D and L as defined above). In other words the higher the FOC value the higher the shaft fletching area.

For example suppose you have a 80 cm long arrow with 0.5 cm diameter.

with a 7% FOC the shaft fletching area = 5.6 square cms 
with a 11% FOC the shaft fletching area = 8.8 square cms

As what is important physically is the turning moment generated on the shaft from the fletching areas let's look at this from this viewpoint taking moments with respect the shaft centre of mass

The shaft fletching effect drag Fs = FOC x KLA/50 (where K is the area to drag force constant).

The turning moment on the arrow from the shaft drag is FOC x KL2A/100

Assume we have fletchings with the centre of pressure at distance P behind the shaft centre with a fletching effect drag of Ff. Then the turning moment on the arrow from the fletchings is Ff (P + FOC x L/100).

The total turning moment on the arrow T = FOC x KL2A/100 + Ff (P + FOC x L/100).The equation for T illustrates how the arrow length, area, FOC and fletching position affect the turning moment on the arrow. This combined with the arrow rotational moment of intertia determine the stability of the arrow.

In practice the higher the arrow FOC the smaller the diameter is likely to be and also the size of the fletchings will probably be smaller (compare the typical fletching size/diameter of aluminium arrows to carbon arrows).

The overall speed of response of the arrow to fletching torque (its angular acceleration), i.e. how fast it straightens up, depends not only on the area of the fletchings but on the fletching torque and the 'rotatability' of the arrow, its moment of inertia. The FOC value effects the torque on the arrow from the fletching area and defines the area of the shaft that acts like a fletching. As the FOC increases the effective fletching area increases and the 'lever arm' increases. At the same time the 'rotatibility' of the shaft decreases (higher moment of inertia). Overall the arrow fletching response increases with FOC.

Having a high FOC for an arrow provides two principal benefits - better arrow groups and reduced wind sensitivity. When you aim at the gold but the arrow ends up in the black something must have changed the direction of the arrow. An arrow mechanically has to leave a bow going in the direction it was pointed and with its axis very closely aligned with the direction it's going. The arrow changes direction after it leaves the bow and the cause is arrow rotational energy (cartwheeling). The arrow flies in a curved path until this kinetic energy is removed by fletching drag (the stabilisation distance). Having a higher FOC results in faster energy dissipation (more fletching action) and because the overall drag force (net momentum) moving the arrow sideways is smaller the amount the arrow direction is changed is reduced. The result is more forgiving arrow to bad tuning or a poor shot leading to reduced group sizes. In a wind the faster arrow rotation rate results in reduced wind drift.

The downside to a higher FOC is because the offset angle between the arrow axis and the direction it's going will in general be smaller, the drag on the pile will increase; lift from shaft drag will be reduced and probably the arrow will be heavier and hence going at a lower speed. All these factors result in 'loss of sight mark'.

A recent example of how FOC affects flight comes from throwing the javelin. Javelins don't have any fletchings and because of the tapered end don't have any vortex shedding torque. Javelin rotation relies solely on shaft drag. The problem was that there was insufficient 'fletching' and javelins were often landing flat and skidding. Also because of the low FOC a lot of drag lift was being generated. Competitors were throwing javelins over 100m which was too for far safety at most stadiums. A couple of years ago the regulations were changed increasing the required FOC value. Now javelins rotate and stick in the ground nicely. The increased rotation rate has reduced the vertical drag component and the distances being thrown have been reduced to within safety acceptable distances.

An FOC calculator is available if required.

FOC is a key consideration of the arrow selection process. The attached spreadsheet illustrates a an arrow selection process incorporating FOC. FOC for arrow selection

Fletchings Versus FOC
Shoot an arrow with no fletchings and a large enough FOC and the arrow will fly straight. Shoot an arrow with zero FOC and large enough fletchings and the arrow will fly straight. Both fletchings and FOC will create arrow flight stability. Both fletchings and FOC have pluses and minuses associated with their use. In practice we use both together. Which of the two is more useful and what limits are their on the two approaches.

Fletchings:

The larger the fletching area the larger the drag torque on the arrow. The first limit on fletching size is that the arrow must pass the riser cleanly so there is a height restriction. The second limit on fletching size is balance between the fletching torque and overall lateral drag. Too large a fletching area and the overall "wind drift" drag effect exceeds the benefit of the higher drag torque. This is particularly true shooting outdoors as you have the external wind lateral drag effect as well as the internal lateral drag effect from fishtailing/porpoising. Larger fletchings weigh more so increasing the area reduces the arrow speed and reduces the arrow FOC.

FOC

Increasing the FOC increases the drag torque on the arrow from both the fletchings and from the arrow shaft areas. It does this without any increase in the overall "wind drift" drag area. Increasing FOC is done by increasing the point weight and the increased mass reduces the overall arrow "wind drift" acceleration. The two practical limitations on FOC are the increase in point weight which reduces the arrow speed to the point where it impedes the use of a bow sight and, as there is a restriction on the diameter, the increase in point/insert length results in an unacceptable strength for the point as regards target impact.

Last Revision 8 April 2014*


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## nuts&bolts (Mar 25, 2005)

PregnantGuppy said:


> This is again stated without data. I understand that it might work well for you, and that's respectable. I personally believe that every archer should go with what works best for them, for sure. But if we're going to make sweeping statements like that, we need some sort of formal data and testing, not just a statement repeated over and over.
> 
> 
> 
> That's the second time recently I've seen that site, but I cannot get it to work for me. None of the links seem to do anything. Am I doing something wrong here? I'd love to read what they have to say, but I just can't access anything interesting


*Center of Pressure by Joe Tapley.

CALCULATION OF THE POSITION OF THE (ROTATIONAL)CENTRE OF PRESSURE

The following example of how to calculate an arrow (rotational drag force) centre of pressure makes two basic simplifications. Firstly the arrow is assumed to be initially stationary i.e.no linear motion, not rotating (fishtailing) and not vibrating. Secondly the shape of the fletchings is assumed to be a right angled triangle, the nearest simple shape that approximates to a fletching. The centre of pressure calculated is that relating to arrow rotation only. The drag force component acting through the centre of gravity which acts only to move the arrow (from part of the shaft) is ignored. Note that we get both linear and angular acceleration so the arrow centre of mass has to move.

The approach is first to calculate the total pressure and centre of pressure locations for the shaft drag, fletching drag and Munk moment individually and then calculate the arrow total pressure and centre of pressure location from the three components.

In the diagram the total rotational drag force (T) acts at the arrow centre of pressure at distance (Lt) behind the centre of gravity (C). The total drag is the sum of the fletching drag (Ff), the appropriate shaft drag (Fs) and the Munk moment (Fm). The distances from the centre of gravity to the fletching drag, shaft drag and Munk moment centres of pressure are Lf, Ls and Lm respectively. The resulting instantaneous axis of rotation of the arrow (R) is at a distance 'A' in front of the arrow centre of gravity.

If you equate the moments for the arrow total pressure/centre of pressure to the individual shaft/fletchings/Munk moment total pressures/centres of pressure you end up with the distance Lt being given by:-

Lt = (Fs Ls + Ff Lf - Fm Lm)/(Fs+Ff-Fm)


Example
Suppose the arrow is 80 cm long and 0.5 cm diameter. The arrow FOC is 13%. The fletchings are assumed to be 2.5 cm long with each fletching having a total area of 3.5 square cm. The front of the fletchings are fitted 73 cm from the front of the shaft. There are 3 fletchings fitted at 120 degrees to the shaft and they are assumed to be triangular in shape.

To make life simple it is assumed that the drag properties of the shaft and fletchings are identical so instead of drag forces we can use drag areas. (main difference is in the shaft and fletching drag coefficients).

With an FOC of 13% the centre of gravity is 10.4 cm in front of the centre of the shaft.

Munk Moment
The value of Fm is assumed at 1.5 square cms. (based on some rough measurements made some years ago).The centre of pressure is assumed to act at the back of the arrow so Lm = 80/2 + 10.4 = 54 cms.

Shaft Drag
The shaft area contributing to rotational drag Fs = 2 x 10.4 x 0.5 = 10.4 square cms. (see section on FOC). Because of symmetry the distance Ls is half the shaft length i.e. 40 cms

Fletchings
For a triangular fletching the centre of pressure horizontal position is 2/3 distance along the base from the front. (The vertical position doesn't matter as the fletchings are assumed not to be spinning the arrow)

i.e. Lf = 73 + 2.5 x 2 / 3 - (40-10.4) = 45.07 cms

The effective area Ff of the fletchings = 1.5 x 3.5 = 5.25 square cms.

(the multiplier 1.5 allows for the fletching angle = 2 x sin squared (alpha/2) where alpha is the angle between fletchings).

Lt is therefore (10.4 x 40 + 5.25 x 45.07 - 1.5 x 54)/(10.4 + 5.25 - 1.5) = 40.4 cms

i.e. the centre of pressure is 40.4 centimetres behind the arrow centre of gravity.

Any arrow rotation will have the effect of moving the centre of pressure further back so the 40.4 cms represents the minimum distance between the centre of gravity and the centre of pressure. (With e.g. fishtailing the influence of the shaft drag decreases and the influence of the fletching drag and Munk moment increases)

If 'Ig' is the arrow moment of inertia at the centre of gravity and 'M' is the total arrow mass then the distance of the instantaneous arrow axis of rotation in front of the centre of gravity 'A' is given by:-

A = Ig / (Lt x M)

e.g. if Ig was 5400 gm cm squ. and M was 18 gms then A = 5400/(40.4 x 18) = 7.4 cms

In reality over time the arrow spin angular momentum varies (as it fishtails/porpoises) and its linear speed (ignored above) varies. As such an arrow does not have an "axis of rotation" (for example it's traveling at around 200fps  ). Engineers will define the (spin) axis of rotation as being at the centre of mass but this is really a practical convenience as it decouples the linear and angular momentum. One could just as well define the axis of rotation in this sense as being at the tip of the archer's nose (not so useful though!). Some further comments on this topic here Arrow rotation

.
Archers from what I've heard/read assign a different meaning to "arrow axis of rotation" which is based on how they see the arrow behaving. So they describe the arrow as "rotating at the point", "rotating in front" or "rotating behind" the point. What they are describing is the combined effect of the arrow rotation and the arrow linear movement (sideways/up-down). In this case the centre of pressure position, as regards arrow response, is best regarded as being based on the total drag on the arrow combined with (the relatively small) existing spin angular momentum. If you balance an arrow on one finger and give an upward push at various points on the shaft behind the cog then this well illustrates the overall arrow behaviour in response to varying position of the overall centre of pressure.

Last Revision 1 July 2009*


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## Bender (Dec 6, 2006)

As I think about it, tungsten points came along not only to fight shaft end wear, but also heard that when they came along some organizations were lining out the scoring zones with steel wire. The hit was either inside the wire and in that scoring zone OR they were out, no BS. Tungsten, and how hard it is helped deal with jacked up point tips from square hits into the wire.

As I read through this thread, it struck me that ALL the blah blah blah maybe over looking an important point. Not only is the relationship between FOC and CG important, but perhaps even MORE important is it relationship to Center of Pressure. (CP) FOC must be forward of CP. Short of generating highly accurate 3D models of a particular arrow assembly and running them through sufficiently sophisticated aerodynamic simulators, CP is only found empirically.

By having a FOC above some certain number say 10% as a lower limit, we just simply and easily assure ourselves of having an FOC that is at out there somewhere forward of CP. For example I myself have found, the hard way, that for me a FOC down at or below 6% is effectively unshootable. Sure the arrow flies, but where it goes? Nobody knows. 

So given the near infinite possible combination of fletching, point, shaft, equipment, venue, having FOC at say 10%+ or whatever, we have a simple and easy "fix" That at least assures us of a good starting point. Beyond that is can of course be diddled with further, empirically, by the individual shooter to see if any actual measurable gains on their score card, can be realized. 

Yes, it's quick and dirty. It's an experimental kludge. But it does get the shooter down the road towards better scores.

FWIW, while looking into other aspects I have generated some data that as an aside, suggest that higher end FOC does begin to force a point down flight attitude. As it was NOT the effect I looking into, it is NOT anything I would bet my life on.

Anyway, if point down does begin to force earlier drop out from trajectory, as I suspect, then actually yes it would have an impact on accuracy, but really more relevant to the venue being shot. Non-sight finger release on unmarked yardage out to 50 or so yards? Early drop out, not good.


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## nuts&bolts (Mar 25, 2005)

Bender said:


> As I think about it, tungsten points came along not only to fight shaft end wear, but also heard that when they came along some organizations were lining out the scoring zones with steel wire. The hit was either inside the wire and in that scoring zone OR they were out, no BS. Tungsten, and how hard it is helped deal with jacked up point tips from square hits into the wire.
> 
> As I read through this thread, it struck me that ALL the blah blah blah maybe over looking an important point. Not only is the relationship between FOC and CG important, but perhaps even MORE important is it relationship to Center of Pressure. (CP) FOC must be forward of CP. Short of generating highly accurate 3D models of a particular arrow assembly and running them through sufficiently sophisticated aerodynamic simulators, CP is only found empirically.
> 
> ...


Calculation of Center of Pressure by Joe Tapley

*CALCULATION OF THE POSITION OF THE (ROTATIONAL)CENTRE OF PRESSURE

The following example of how to calculate an arrow (rotational drag force) centre of pressure makes two basic simplifications. Firstly the arrow is assumed to be initially stationary i.e.no linear motion, not rotating (fishtailing) and not vibrating. Secondly the shape of the fletchings is assumed to be a right angled triangle, the nearest simple shape that approximates to a fletching. The centre of pressure calculated is that relating to arrow rotation only. The drag force component acting through the centre of gravity which acts only to move the arrow (from part of the shaft) is ignored. Note that we get both linear and angular acceleration so the arrow centre of mass has to move.

The approach is first to calculate the total pressure and centre of pressure locations for the shaft drag, fletching drag and Munk moment individually and then calculate the arrow total pressure and centre of pressure location from the three components.

In the diagram the total rottional drag force (T) acts at the arrow centre of pressure at distance (Lt) behind the centre of gravity (C). The total drag is the sum of the fletching drag (Ff), the appropriate shaft drag (Fs) and the Munk moment (Fm). The distances from the centre of gravity to the fletching drag, shaft drag and Munk moment centres of pressure are Lf, Ls and Lm respectively. The resulting instantaneous axis of rotatation of the arrow (R) is at a distance 'A' in front of the arrow centre of gravity.

If you equate the moments for the arrow total pressure/centre of pressure to the indivual shaft/fletchings/Munk moment total pressures/centres of pressure you end up with the distance Lt being given by:-

Lt = (Fs Ls + Ff Lf - Fm Lm)/(Fs+Ff-Fm)


Example
Suppose the arrow is 80 cm long and 0.5 cm diameter. The arrow FOC is 13%. The fletchings are assumed to be 2.5 cm long with each fletching having a total area of 3.5 square cm. The front of the fletchings are fitted 73 cm from the front of the shaft. There are 3 fletchings fitted at 120 degrees to the shaft and they are assumed to be triangular in shape.

To make life simple it is assumed that the drag properties of the shaft and fletchings are identical so instead of drag forces we can use drag areas. (main difference is in the shaft and fletching drag coefficients).

With an FOC of 13% the centre of gravity is 10.4 cm in front of the centre of the shaft.

Munk Moment
The value of Fm is assumed at 1.5 square cms. (based on some rough measurements made some years ago).The centre of pressure is assumed to act at the back of the arrow so Lm = 80/2 + 10.4 = 54 cms.

Shaft Drag
The shaft area contributing to rotational drag Fs = 2 x 10.4 x 0.5 = 10.4 square cms. (see section on FOC). Because of symmetry the distance Ls is half the shaft length i.e. 40 cms

Flechings
For a triangular fletching the centre of pressure horizontal position is 2/3 distance along the base from the front. (The vertical position doesn't matter as the fletchings are assumed not to be spinning the arrow)

i.e. Lf = 73 + 2.5 x 2 / 3 - (40-10.4) = 45.07 cms

The effective area Ff of the fletchings = 1.5 x 3.5 = 5.25 square cms.

(the multiplier 1.5 allows for the fletching angle = 2 x sin squared (alpha/2) where alpha is the angle between fletchings).

Lt is therefore (10.4 x 40 + 5.25 x 45.07 - 1.5 x 54)/(10.4 + 5.25 - 1.5) = 40.4 cms

i.e. the centre of pressure is 40.4 centimetres behind the arrow centre of gravity.

Any arrow rotation will have the effect of moving the centre of pressure further back so the 40.4 cms represents the minimum distance between the centre of gravity and the centre of pressure. (With e.g. fishtailing the influence of the shaft drag decreases and the influence of the fletching drag and Munk moment increases)

If 'Ig' is the arrow moment of inertia at the centre of gravity and 'M' is the total arrow mass then the distance of the instantaneous arrow axis of rotation in front of the centre of gravity 'A' is given by:-

A = Ig / (Lt x M)

e.g. if Ig was 5400 gm cm squ. and M was 18 gms then A = 5400/(40.4 x 18) = 7.4 cms

In reality over time the arrow spin angular momentum varies (as it fishtails/porpoises) and its linear speed (ignored above) varies. As such an arrow does not have an "axis of rotation" (for example it's travelling at around 200fps  ). Engineers will define the (spin) axis of rotation as being at the centre of mass but this is really a practical convenience as it decouples the linear and angular momentum. One could just as well define the axis of rotation in this sense as being at the tip of the archer's nose (not so useful though!). Some further comments on this topic here Arrow rotation

.
Archers from what I've heard/read assign a different meaning to "arrow axis of rotation" which is based on how they see the arrow behaving. So they describe the arrow as "rotating at the point", "rotating in front" or "rotating behind" the point. What they are describing is the combined effect of the arrow rotation and the arrow linear movement (sideways/up-down). In this case the centre of pressure position, as regards arrow response, is best regarded as being based on the total drag on the arrow combined with (the relatively small) existing spin angular momentum. If you balance an arrow on one finger and give an upward push at various points on the shaft behind the cog then this well illustrates the overall arrow behaviour in response to varying position of the overall centre of pressure.

Last Revision 1 July 2009

*


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## nuts&bolts (Mar 25, 2005)

Center of Pressure figure from the Joe Tapley article.

Calculation of Center of Pressure by Joe Tapley

*CALCULATION OF THE POSITION OF THE (ROTATIONAL)CENTRE OF PRESSURE

The following example of how to calculate an arrow (rotational drag force) centre of pressure makes two basic simplifications. Firstly the arrow is assumed to be initially stationary i.e.no linear motion, not rotating (fishtailing) and not vibrating. Secondly the shape of the fletchings is assumed to be a right angled triangle, the nearest simple shape that approximates to a fletching. The centre of pressure calculated is that relating to arrow rotation only. The drag force component acting through the centre of gravity which acts only to move the arrow (from part of the shaft) is ignored. Note that we get both linear and angular acceleration so the arrow centre of mass has to move.

The approach is first to calculate the total pressure and centre of pressure locations for the shaft drag, fletching drag and Munk moment individually and then calculate the arrow total pressure and centre of pressure location from the three components.

In the diagram the total rottional drag force (T) acts at the arrow centre of pressure at distance (Lt) behind the centre of gravity (C). The total drag is the sum of the fletching drag (Ff), the appropriate shaft drag (Fs) and the Munk moment (Fm). The distances from the centre of gravity to the fletching drag, shaft drag and Munk moment centres of pressure are Lf, Ls and Lm respectively. The resulting instantaneous axis of rotatation of the arrow (R) is at a distance 'A' in front of the arrow centre of gravity.

If you equate the moments for the arrow total pressure/centre of pressure to the indivual shaft/fletchings/Munk moment total pressures/centres of pressure you end up with the distance Lt being given by:-

Lt = (Fs Ls + Ff Lf - Fm Lm)/(Fs+Ff-Fm)*


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## waxyjaywalker (Apr 10, 2013)

Just a quick followup on accessing the site; I've got NoScript running, so that may be what's preventing the javascript from running. Also, a lot of the info appears to be accessible on the link that's got all the pdf files. https://www.bio.vu.nl/thb/users/kooi/


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## nuts&bolts (Mar 25, 2005)

Bender said:


> As I think about it, tungsten points came along not only to fight shaft end wear, but also heard that when they came along some organizations were lining out the scoring zones with steel wire. The hit was either inside the wire and in that scoring zone OR they were out, no BS. Tungsten, and how hard it is helped deal with jacked up point tips from square hits into the wire.
> 
> As I read through this thread, it struck me that ALL the blah blah blah maybe over looking an important point. Not only is the relationship between FOC and CG important, but perhaps even MORE important is it relationship to Center of Pressure. (CP) FOC must be forward of CP. Short of generating highly accurate 3D models of a particular arrow assembly and running them through sufficiently sophisticated aerodynamic simulators, CP is only found empirically.
> 
> ...


Bender...your comments are the FIRST intelligent comments, about arrow flight. At longer shooting distances, an arrow has a ballistic trajectory. That means the arrow follows an arc, there is an upwards portion of flight, and there is level flight at the peak of the trajectory and there is a downwards portion of flight, on final approach to the target. As much as we like to think that our arrows fly like a laser beam, arrows do not fly in a "FLAT" trajectory. Now, most folks imagine a smooth parabola for the flight trajectory. But, we need to understand PITCH angle for the fuselage (arrow tube) and we need to understand ANGLE OF ATTACK. That means, the angle of the tube in mid flight, does not match the flight trajectory. Ever see a 747 at full flaps, on approach to the airstrip at the airport? Super slow air speed, flaps are on full, and the airplane is actually flying in a horizontal line, parallel to the ground, but the fuselage is at a positive pitch angle (propeller end of the airplane is pointing noticeably UPHILL, even though the plane is traveling in a horizontal line).


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## nuts&bolts (Mar 25, 2005)

Blah...blah...blah, pitch angle, angle of attack, flight path vector. Who cares. This is about metallurgy and tungsten carbide and elemental tungsten, and drag vortices and munk moments, and frontal area and drag coefficients and laminar versus turbulent airflow, you know, boundary effects and citing this paper and that paper. Not really. More intelligent writing by Joe Tapley.

Flight Instability by Joe Tapley.
*
FLIGHT INSTABILITY
Archers have often reported the observation that at longer distances the arrow group sizes seem to increase more than would be expected solely from the increased distance. Andrew Middleton on his web page on arrow flight ballistics refers to this effect as longer distance 'flight instability' and it's such an appropriate term that I have 'borrowed' it.

This long distance flight instability effect is I think complicated and I don't claim to understand it. What I think I can do is put forward some of the factors that contribute to generating it.

Arrow Distance
We tend to think of the target distance as being the horizontal distance but the flight path of the arrow through the air, because it travels in an arc is much longer. The proportional increase in arrow travel distance through the air in going from 70 to 90 metres is larger then the proportional increase between the horizontal 70 and 90 metres distances. The difference depends a lot on the initial arrow speed.

Arrow Speed
arrow speed At longer distances, with higher arrow trajectory, the arrow is more likely to be speeding up in the latter part of its flight. On the way down the arrow is losing speed to drag but gaining speed from gravitational acceleration. At longer distances (the arrow 'falls' further) the speed gain from gravity outweighs the speed loss from drag. This increased speed results in increased drag forces moving the arrow about and increased fletching action.

The graph illustrates how the total speed of an arrow varies with distance. With a typical target arrow at 90 metres target distance the arrow speed is increasing over around the last 20 metres of flight. The drag forces on the arrow are proportional to the square of the velocity.


Arrow Drag
This is the complicated bit. To keep it simple I am only going to consider the vertical component of the drag force on the arrow and assume that the arrow does not fishtail (horizontally) at all.

When you shoot an arrow at the instant of release the arrow is more or less pointing in the direction its travelling. Because gravity is accelerating the arrow downwards the (offset) angle between the direction the arrow is pointing and the direction the arrow is travelling steadily increases. The fletching action works to rotate the arrow to reduce the offset angle and as the rotation builds up the gap starts to close and eventually the offset angle reduces back to zero.

Offset Angle 45m

The graphs illustrate this behaviour at a 45 metre target distance. The offset angle increases to about 20 metres distance and then reduces to zero at around 37 metres. For most of the flight the air flow acts on the lower surface of the arrow.


Drag 45m

The associated vertical drag over 45 metres is illustrated in the second graph. For virtually all of the flight the drag provides a 'lift' force pushing the arrow upwards.


The following graphs illustrate what happens at 90 metres distance.

offset 90m

The arrow now has enough flight time for its direction to oscillate around its direction of travel. The air flow over the arrow oscillates between acting on the lower and upper surfaces of the arrow.


drag 90m

As a consequence the vertical drag force oscillates between pushing the arrow upwards and driving the arrow downwards. In addition the lift force on the arrow increases towards the latter part of the arrow flight because of the increased arrow speed.


offbad 90m

The preceding graphs relate to a perfectly shot arrow leaving the bow with zero rotation. If the arrow leaves the bow already rotating in some direction (a poor shot) then this can make a significant difference to how the offset angle varies during the flight as illustrated for a poor shot at 90 metres.


bad90

The poor shot can result in a marked change in how the lift force varies on the shaft over the flight and hence where the arrow ends up on the target. The way the offset angle oscillates and the consequent way the vertical component of the total drag force varies is very sensitive to the direction and the amount of rotation the arrow has when it leaves the bow. At short distances (less than 45 metres say) the flight time is short enough so that only a small amount (or even zero) offset angle oscillation occurs. The longer the distance the more oscillations you get and so the vertical drag effects on the arrow become increasingly sensitive to how the arrow is shot.

A one line explanation of arrow flight instability would run something like the following. "At longer distances the development of a natural arrow 'wobble' combined with the increased arrow speed towards the latter part of its flight amplify any variations in how the arrow leaves the bow resulting in a larger spread of arrow impacts on the target".

Last Revision 1 July 2009*


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## nuts&bolts (Mar 25, 2005)

Joe Tapley is British. So, he talks about "OFFSET ANGLE".

Arrow Drag
This is the complicated bit. To keep it simple I am only going to consider the vertical component of the drag force on the arrow and assume that the arrow does not fishtail (horizontally) at all.

When you shoot an arrow at the instant of release the arrow is more or less pointing in the direction its travelling. Because gravity is accelerating the arrow downwards the (offset) angle between the direction the arrow is pointing and the direction the arrow is travelling steadily increases. The fletching action works to rotate the arrow to reduce the offset angle and as the rotation builds up the gap starts to close and eventually the offset angle reduces back to zero.

Offset Angle 45m

The graphs illustrate this behaviour at a 45 metre target distance. The offset angle increases to about 20 metres distance and then reduces to zero at around 37 metres. For most of the flight the air flow acts on the lower surface of the arrow.

The graph is showing that from Zero to 20 meters (about 24 yards for us Yanks), the pitch angle for the arrow tube is positive (body of the arrow tube is pointing MORE uphill, than the flight path). Just like the airplane flying at super slow speed. By the time the arrow reaches a 45 meter target (49.5 yards), the arrow tube has rotated LESS and LESS uphill and the PITCH angle of the arrow tube has started to match the flight path angle. So, YES....arrows do not FLY FLAT like a laser. So, YES, the FOC matters, cuz the FOC will cause an airframe to rotate in flight, the pitch angle will reduce with enough distance, so that an uN-propelled projectile (arrow with no jet engines), will eventually go from a positive pitch angle to a zero pitch angle.


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## chrstphr (Nov 23, 2005)

His site may not work as well, Joe passed away in 2016. I had a number of enjoyable conversations with him during my testing of higher point weights in X10s for bareshafts and fletched shafts. 

His knowledge was way above mine. 


Chris


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## chrstphr (Nov 23, 2005)

whiz-Oz said:


> So, you didn't know that the standard profile Easton tungsten points increase the point at which the airflow along the arrow becomes turbulent, therefore increasing the arrows drag and INCREASING drift in unpredictable winds?


the oscillation of the arrow from the bow makes the boundary layer turbulent. Irrespective of point shape. It is actually found get better results to make the boundary layer turbulent intentionally by roughing up the arrow point. 

Hence some of the dimpled points you see on the market, and dimpled gold balls as an example.

Chris


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## PregnantGuppy (Jan 15, 2011)

Thanks, nuts&bolts. I finally got some of the site working by using the italian version as suggested, but seeing it here is more convenient.

However, I'm still not seeing any data. Tapley still just does the same thing you guys are doing and iterates over and over that it matters without giving any quantification. FOC definitely matters to some degree, or there's no way we would be able to get the results we get today. But to what degree it matters is not something for which we seem to have any good data. And clearly there;s a point at which it actually degrades performance; that's something that Tapley himself states, but again with no justification and no indication of which point that would be.

Let me phrase my concern in a different way. All of the models being proposed and analyzed here are theoretical. And theoretical is fine; I'm a very technically minded individual as well, so understanding the emchanics of the arrow just for the sake of understanding them is interesting. But when it comes to actually applying the theoretical models, we need to use actual pratical data to see how it actually affects performance, and if it's something that's worth pursuing for archers today. There's plenty of things that theoretical models fail to account, or they may show a difference that ends up being insiginificant in practice, so regardless of how well-founded the model is we need to see actual data to be able to make recommendations based on the model.



> the oscillation of the arrow from the bow makes the boundary layer turbulent. Irrespective of point shape. It is actually found get better results to make the boundary layer turbulent intentionally by roughing up the arrow point.
> 
> Hence some of the dimpled points you see on the market, and dimpled gold balls as an example.


In order to make this argument convincing, the next thing you'd have to say is something like "All the top archers noticed this, so now they all shoot dimpled points because it increases scores by X points". Because if that kind of advancement does help, you'd certainly see basically all top shooters using it already. The fact that it hasn't become a de facto standard suggests that it doesn't matter enough in practice for us to worry about it.


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## whiz-Oz (Jul 19, 2007)

chrstphr said:


> the oscillation of the arrow from the bow makes the boundary layer turbulent. Irrespective of point shape. It is actually found get better results to make the boundary layer turbulent intentionally by roughing up the arrow point.
> 
> Hence some of the dimpled points you see on the market, and dimpled gold balls as an example.
> 
> Chris


Dimples on golf balls enhance the magnus effect in order to gain lift by keeping the energy in the boundary layer to stop it separating. 
Dimpled arrow points are for selling to the clueless archers who have no idea, but will try to buy points based on joining dots that don't actually have anything to do with each other. 

So, you've actually seen data supporting your assertion regarding turbulent flow and oscillation, or you're just winging it again? 

Note that nutsandbolts just posted stuff from Joe's website without actually being able to explain it and still hasn't answered the question I asked him about his post almost 12 months ago. 

https://www.archerytalk.com/vb/showthread.php?t=5138425&p=1105364713#post1105364713


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## chrstphr (Nov 23, 2005)

yes, i read research and data supporting my assertion. Of course i'm too stupid to come up with it on my own. How else would i even know about boundary layer turbulence and other fancy scientific terms?

And you still havent said what your point weight is for your X10s and why. Do you even shoot archery, or do you just troll FOC conversations on the internet for the past 10 years?


Chris


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## whiz-Oz (Jul 19, 2007)

And, what research is that? 

I run 120 grain stainless and tungsten points. If I was super serious, I'd be having the tungsten's ground down to avoid tripping the laminar flow too early. 

So, when was asking for actual proof of assertions trolling? 

I'm just pointing out that none of you guys can actually explain what you're talking about without resorting to other people's opinions.


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## theminoritydude (Feb 11, 2013)

I stated my opinions without referring to other because I hate reading.......


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## RickBac (Sep 18, 2011)

Talk about a thread getting derailed.

As for the Tungsten, Stainless or Tool Steel, for each individual archer, does one shoot better for them than the other. Can they shoot well enough to truly see a difference? Is the difference significant enough to justify the increase in point cost.

The vast majority of athletes won't care about the science, just will it help them perform better.


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## chrstphr (Nov 23, 2005)

RickBac said:


> Talk about a thread getting derailed.
> 
> As for the Tungsten, Stainless or Tool Steel, for each individual archer, does one shoot better for them than the other. Can they shoot well enough to truly see a difference? Is the difference significant enough to justify the increase in point cost.
> 
> The vast majority of athletes won't care about the science, just will it help them perform better.


i get better performance from the tungsten points in the wind. Only you can say if its worth it for you. 


Chris


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## chrstphr (Nov 23, 2005)

whiz-Oz said:


> And, what research is that?
> 
> I run 120 grain stainless and tungsten points. If I was super serious, I'd be having the tungsten's ground down to avoid tripping the laminar flow too early.
> 
> ...


I was sent the research and data by another reading this thread. Normally i would give the link to it.

But honestly, you are so rude and condescending to posters on here, that i am not interested in helping you nor giving you researched data to help educate you. And thats a first for me on AT since i joined 13 years ago. 


Chris


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## whiz-Oz (Jul 19, 2007)

So, now you're hiding behind the old "I could tell you, but now you're not worth it" argument? This is like dealing with conspiracy theorists. 
I know that there isn't research that supports it. 
I'm continuing to ask you guys to explain your beliefs because I know that they're unsupportable. 
I really don't care if you think I'm rude and condescending. 
It's a handy thing for you to hide behind now because you've now worked yourself into a corner with your "I could provide links, but I'm not going to" attitude.

All you have are other people's opinions. Not one iota of actual, document scientific proof. However, you're full of biased belief in your own experiences where you ignore the results that disprove your theory. 

If people here continue to post links to stuff that you cannot personally explain to any depth, it illustrates perfectly that you're relying on other peoples opinions to support your own. 

This is a perfect example of why online forums continue to perpetuate myths. People are happy to let other people do the thinking. 

I'm sure nutsandbolts checked Joe's working out. I know he has no idea what it pertains to.


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## whiz-Oz (Jul 19, 2007)

RickBac said:


> Talk about a thread getting derailed.
> 
> As for the Tungsten, Stainless or Tool Steel, for each individual archer, does one shoot better for them than the other. Can they shoot well enough to truly see a difference? Is the difference significant enough to justify the increase in point cost.
> 
> The vast majority of athletes won't care about the science, just will it help them perform better.


Tungsten points were introduced to combat shaft wear. The profile is designed to alleviated wear by being bigger in diameter than the shaft behind it. This increase in diameter has been shown by actual scientific testing to bring the transition to turbulent flow along the shaft forward and increase the drag profile of the arrow. Drag profile is directly related to wind drift, which has also been established by actual scientific testing. 

In a sport were the top levels are separated by single points, common sense says that optimizing for wind drift will shrink the average group size. 

When the archer's average performance is far worse than the arrow's group potential, more points can be gained by working on the archer. (This is the situation that exists for everyone who isn't in the top one percent of archers.)

When the archer's technique is optimum and we're talking world cup performance level consistency, developing the equipment to minimize the effect of random atmospheric disturbances , ie drift, is the next avenue to concentrate on. 

At that point, you can start considering where the actual research has gone. It should be no surprise that archers at that level are experimenting with different point profiles. There are well respected archer machinists who have already done the work for national teams, years ago.


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## Vittorio (Jul 17, 2003)

whiz-Oz said:


> Tungsten points were introduced to combat shaft wear. The profile is designed to alleviated wear by being bigger in diameter than the shaft behind it. .....


They have been made for X10 first in 1999 to increase their FOC in comparison to ACE's , still used by a lot of shooters. 
And in 2015 140 grains points for Pro tour (and X10) have been introduced exactly for the same reason, considering that Pro tour by their design have less FOC that X10. And in 2016 150 gr points for Nano pro have been made under pressure from pro shooters that after 2015 World (windy) Championships felt disadvantge in comparison to their counterparts using Pro tour with 140 gr points
Today 140 gr tungsten are standard for majority of Pro tour shooters, and several recuve shooters are experimenting with them on X10 too 

Because they protect the shaft? Pls ....


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## Seattlepop (Dec 8, 2003)

whiz-Oz said:


> So, now you're hiding behind the old "I could tell you, but now you're not worth it" argument? This is like dealing with conspiracy theorists.
> I know that there isn't research that supports it.
> I'm continuing to ask you guys to explain your beliefs because I know that they're unsupportable.
> *I really don't care if you think I'm rude and condescending. *
> ...


You may not, but hopefully a moderator will.


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## whiz-Oz (Jul 19, 2007)

Vittorio said:


> Because they protect the shaft? Pls ....


Well, we have two competing theories now. 

One from the guy who designed them and can be heard describing exactly why they were made on the Easton podcast, and someone who isn't the guy who designed them. 

I'm going to give one of those sources a higher likelihood of being correct. 

We've still got the serious lack of evidence that arrows of identical physical properties other than FOC haven't been shown to perform better under varied conditions. 

All it would require would be someone with a shooting machine, actual testing methodology (not just sticking heavier points in and saying only FOC was altered) and several thousand shots to demonstrate a statistical advantage one way or the other. 

I'll be the first person to be swayed by proof if it ever appears, but it hasn't yet. Just a long list of opinions that haven't been proven and will continue to get trotted out continuously in an attempt to look authoritative. 

I just get people upset because I undermine that impression when I ask for facts to back it up. People start squirming and other people think it's rude and condescending.


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## theminoritydude (Feb 11, 2013)

So now it’s based on whose opinion matters, rather than experimental results?


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## Bender (Dec 6, 2006)

theminoritydude said:


> So now it’s based on whose opinion matters, rather than experimental results?




Yeah, gotta love it don't ya?


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## nuts&bolts (Mar 25, 2005)

whiz-Oz said:


> Note that nutsandbolts just posted stuff from Joe's website without actually being able to explain it and still hasn't answered the question I asked him about his post almost 12 months ago.
> 
> https://www.archerytalk.com/vb/showthread.php?t=5138425&p=1105364713#post1105364713


Reading compression is clearly not your strong point. Fellow was having trouble getting the Joe Tapley website link to work. Fellow was interested in reading some of Joe Tapley's writing. So, posted two selections of Joe Tapley's writing so the fellow could have a taste. James Park is not the only person who has researched arrow flight dynamics. Since you are so well read, I'm sure you have looked into research performed elsewhere. Hint. Hint.


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## nuts&bolts (Mar 25, 2005)

PregnantGuppy said:


> Thanks, nuts&bolts. I finally got some of the site working by using the italian version as suggested, but seeing it here is more convenient.
> 
> However, I'm still not seeing any data. Tapley still just does the same thing you guys are doing and iterates over and over that it matters without giving any quantification. FOC definitely matters to some degree, or there's no way we would be able to get the results we get today. But to what degree it matters is not something for which we seem to have any good data. And clearly there;s a point at which it actually degrades performance; that's something that Tapley himself states, but again with no justification and no indication of which point that would be.
> 
> ...


PregnantGuppy. Theoretical physics and then applied physics. Joe Tapley goes through the theoretical physics. So, you want empirical data. 










Is a wind tunnel adequate? No, the arrow is not in flight. Arrow is suspended in mid-air, in the wind tunnel.

So, instead of a "shooting machine", a custom designed air cannon was fabricated for arrow launching.


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## nuts&bolts (Mar 25, 2005)

PregnantGuppy said:


> Thanks, nuts&bolts. I finally got some of the site working by using the italian version as suggested, but seeing it here is more convenient.
> 
> However, I'm still not seeing any data. Tapley still just does the same thing you guys are doing and iterates over and over that it matters without giving any quantification. FOC definitely matters to some degree, or there's no way we would be able to get the results we get today. But to what degree it matters is not something for which we seem to have any good data. And clearly there;s a point at which it actually degrades performance; that's something that Tapley himself states, but again with no justification and no indication of which point that would be.
> 
> ...












Angle of attack matters. Blah. Blah. Blah. Laminar. Turbulent. Shooting machines. Air Cannons. Wind Tunnels. All theoretical. Well, these researchers also had a human shooter, to compare against the wind tunnel findings and the air cannon findings. If you shoot 9-inch groups at 20 yards, then, this research doesn't help you.


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## Seattlepop (Dec 8, 2003)

whiz-Oz said:


> Well, we have two competing theories now.
> 
> One from the guy who designed them and can be heard describing exactly why they were made on the Easton podcast, and someone who isn't the guy who designed them.
> 
> ...


In your *attempt* to look authoritative you have referred to Park's research. Mr. Park has contradicted your argument. Are you declaring James Park is incompetent? Either way you lose.


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## Seattlepop (Dec 8, 2003)

Guppy, You are seeing the data, you just refuse to accept it. The data here is the overwhelming consensus that FOC affects an arrow’s flight. Consensus does matter when it is based on the actual experience of the multitude of archer’s who have tested it. Chris’ links may not reflect the one official, scientific experiment you seek, but they reflect more than enough practical experience to be seriously considered. 

The alternative would be for you to make an argument that consensus is wrong and then you would have to support your position with equally convincing “data”. Foolishly, Whiz has been trying to disprove consensus by trying to prove a negative which is unsupported even by his guru, Mr. Park. 

I would suggest that since no one can disprove FOC matters, and the overwhelming consensus is that it does, then the FOC effect is a fact. Facts then, are explained by theoretical models to explain the mechanics, in this instance, of FOC. 

Conclusion? Never spit into the wind.


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## whiz-Oz (Jul 19, 2007)

Seattlepop said:


> In your *attempt* to look authoritative you have referred to Park's research. Mr. Park has contradicted your argument. Are you declaring James Park is incompetent? Either way you lose.


Really? 
So, you can point out where?


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## Seattlepop (Dec 8, 2003)

whiz-Oz said:


> Really?
> So, you can point out where?


See, you depend on others to do your thinking for you. Sad! 

Your posts have become little more than click bait. Imho, of course.


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## whiz-Oz (Jul 19, 2007)

I'm just seeing if you can actually justify your claim. Apparently not.


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## crocstar25 (Jun 12, 2018)

Not bad, china quality shows a little.


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## PregnantGuppy (Jan 15, 2011)

theminoritydude said:


> So now it’s based on whose opinion matters, rather than experimental results?


Big difference there. One opinion is on what the points were designed for. Clearly authority should be given to the person who actually designed them. The other is an opinion on what they actually do for shooting performance. That's a different matter altogether.



> Angle of attack matters. Blah. Blah. Blah. Laminar. Turbulent. Shooting machines. Air Cannons. Wind Tunnels. All theoretical. Well, these researchers also had a human shooter, to compare against the wind tunnel findings and the air cannon findings. If you shoot 9-inch groups at 20 yards, then, this research doesn't help you.


All you did here is post a graph with an unlabeled axis and no context and then post a bunch of scientific terms. I still see no data supporting the point that higher FOC leads to better performance. Could you link to the actual study you mention instead? It seems I might be able to get more interesting data from that.



> Guppy, You are seeing the data, you just refuse to accept it. The data here is the overwhelming consensus that FOC affects an arrow’s flight. Consensus does matter when it is based on the actual experience of the multitude of archer’s who have tested it. Chris’ links may not reflect the one official, scientific experiment you seek, but they reflect more than enough practical experience to be seriously considered.
> 
> The alternative would be for you to make an argument that consensus is wrong and then you would have to support your position with equally convincing “data”. Foolishly, Whiz has been trying to disprove consensus by trying to prove a negative which is unsupported even by his guru, Mr. Park.
> 
> I would suggest that since no one can disprove FOC matters, and the overwhelming consensus is that it does, then the FOC effect is a fact. Facts then, are explained by theoretical models to explain the mechanics, in this instance, of FOC.


I believe you are misinterpreting my posts. In all of my posts, I have never denied that FOC has no impact. That much is obvious, and I'm not about to start shooting arrows with no point weight on them. So I would very much appreciate it if all of you would stop claiming that this is what I say.

What I am saying is that there is no data to confirm up to what point it is beneficial to increase FOC. Everyone claims higher FOC leads to more stable flight and better groupings, but most of the sources you keep citing also state that there's clearly a trade-off if you go too high.

So the data I want to see is data that plots various FOC's, and sees how the accuracy is affected by this change. Then we can finally answer up to what point FOC matters.

And none of the data that has been posted actually shows this. It shows how point shape affects drag, how angle of attack affects turbulence, and so forth. But not a single one of them has kept track of the size of the groups or any other metric of accuracy, and none of them have focused on FOC as the single variable to change. So I feel quite justified in refusing to accept data that has nothing to do with the discussion at hand.


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## theminoritydude (Feb 11, 2013)

PregnantGuppy said:


> Big difference there. One opinion is on what the points were designed for. Clearly authority should be given to the person who actually designed them. The other is an opinion on what they actually do for shooting performance. That's a different matter altogether.
> .


They are both opinions. Here let me demonstrate.

Someone designs a car. When asked what reasons he had for designing this car, he says he designed it to save gas, because other cars burn too much fuel traveling X distance, through the use of a specific component. Does not specify how component actually saves fuel.

Car manufacturer X uses the new car because it is fun to drive. When hearing claims that it saves fuel (from the designer), calls it hogwash.

Who do you trust?


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## theminoritydude (Feb 11, 2013)

So can we start shooting arrows with 120gr nocks and plastic points now?


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## chrstphr (Nov 23, 2005)

PregnantGuppy said:


> All you did here is post a graph with an unlabeled axis and no context and then post a bunch of scientific terms. I still see no data supporting the point that higher FOC leads to better performance. Could you link to the actual study you mention instead? It seems I might be able to get more interesting data from that.


i sent you the link. 

angle of attack matters which is what FOC gives you. 


Chris


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## Seattlepop (Dec 8, 2003)

PregnantGuppy said:


> Big difference there. One opinion is on what the points were designed for. Clearly authority should be given to the person who actually designed them. The other is an opinion on what they actually do for shooting performance. That's a different matter altogether.
> 
> 
> 
> ...


And therein lies the problem. No one can tell you when your "trade-off" occurs. There are too many other variables in each archer's shot and kit. I know where my trade-off occurs by testing my set up and I suggest you will have to do the same. And the funny thing is, it isn't that difficult. But it will require you to go out and test it for yourself. If I had to make a rule for when the "trade-off" occurs, it would be when the extra point weight prevents you from effectively shooting a chosen distance. So how do you do that? I think you know.

You need to find the highest point weight you can effectively shoot for a given distance. First, decide the maximum distance you will be shooting in any given event. For instance, I had to test for 90m since that is the long distance I shoot in a 1440 Round. 37# otf, ACE 570, started with 120gr points. Whoa. Didn't take long to find out that wouldn't work. Those flew fairly nicely to 70m, meaning they group well and with reasonably low arc and time in flight both of which are purely subjective. However, after 70m they dropped like a wounded pigeon. That is not subjective. To reach 90m with 120gr I had to pull my sight extension in all the way, bottom out the aperture and aim for the top of the bale. I don't need a data chart to suggest I can do better with less point weight. 

See where I'm going with this? The charts Joe Tapely has or that software such as Archer's Advantage can produce will give you trajectory data per input sets. Perhaps you would find those useful. Perhaps. I just go by feel and what I like to see when I shoot. Bottom line for me is that I found 110gr point is the highest weight I can use and shoot all my tournament distances effectively. When I go to 100gr I gain no point advantage and when I go to 120gr I can't aim comfortably and the scores show it. It is really that simple. 

Having the ability to ask for the impossible doesn't mean that the impossible must therefore exist. I read that somewhere, just like saying it.


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## Vittorio (Jul 17, 2003)

I'm now close to 27 years from my first discussion about FOC, and content of the discussion is ever the same. FOC did mattter for all in the discussions, ever, only element with large discrepancy in conclusions has ever been if "too much FOC" existed. 
Joe T. has been the only one trying to find a scientific answer, to this and other matters related to arrow flight, including speed vs size vs. wind angle to flight, and we exchanged a lot of information in the years baout procatial findings that were many times confirming results from his Arrow flight simulator. 
Real problem in making tests was the fact that a given arrow only had a limited range of possible FOC as of no practical availbility of points and arrows shafts that could give large variations on it.
Easton in 1996 was the only company making real competition arrows, as Beman was already gone, and they introduced the X10 to non US archers during the Atlanata pre-olympic turnament. A bit late for many to experiment long enough before using them in Atlanta. In Atlanta, my son went with 4 bows, 2 of them tuned for X10 and 2 of them tuned for ACE's, but only used ACE's there, with 684 Olympic record in qualification and 170 Olympic record on 18 arrows match under strong rain and wind. 
The X10 got their 120 gr tungsten points in 1999. Before that time, all simulations and tests with standard steel points were still giving advantage to ACE's. Specifically at 90 mt X10 were suffering a lot from their mass weight and their low FOC. At World target championship 1999 my son again dominated the qualification round in a strong wind with ACE's. 
The full story up to London 2012 includes Rick Mc Kinney, Jim Easton, Don Rabska, George Teckmikoff, Mike Gerard, Jason McKittric, and many other friends to me, plus all development done for CX to sort out the Extremes . We have sometime shared experiencies, we have of course many times had disagreements about conclusions. My facts say that there is not such a thing like "too much foc" as clearly indoor fat arrows shooters are showing every winter. There is not too much FOC outdoor too, as I have several times tested using even McKinney II shafts and tungsten points. But of course you should be able to tune arrows with a lot of FOC, and this is a different art than the usual one. 

Many countries have made (sometime secret) studies about arrow flight to define best parameters of an arrow. Shooting machines (I have had one for a couple of years), wind tunnels, statistycal analisys, and so on. Nothing has simulated all real shooting conditions up to now, as there are too many parameters involved in each specific situation, and specific situations are unpredictable. So, you have to go by best compromise, and best compromise today is X10/Pro tour (or nano pro/extreeme ) with 120 to 140 gr point and medium short curled vanes. 
Still i have to see one top level archer (man) shooting steel points on those arrows (because steel points bend, this is another serious reason  ) . Full stop. 

whiz-Oz, after so many years of your strong opposition to the high FOC concept, don't you think is time to tell us who you are, and if you at least are an archer of what sort of personal experience you have got in archery ? As everyone knows, opinions are as important as those that tell them.


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## whiz-Oz (Jul 19, 2007)

Vittorio said:


> whiz-Oz, after so many years of your strong opposition to the high FOC concept, don't you think is time to tell us who you are, and if you at least are an archer of what sort of personal experience you have got in archery ? As everyone knows, opinions are as important as those that tell them.


I don't have a strong opposition to the high FOC concept. I fully endorse shooting the heaviest points you can fit in if you don't have to compromise anything else. I totally believe in maintaining an adequate margin of stability to get the job done. 

What I don't believe is that FOC determines accuracy potential in random atmospheric conditions. 

I have never seen one test other than Clarance Hickmans, where FOC ONLY was changed. Only points and thus weight and FOC, so people are arguing for one thing, while changing two. Weight is a legitimate factor for reducing wind drift if no compromise is made for speed loss, leaving a projectile with more time to be affected. 

My background is engineering, science, technology the military aerospace industry and high performance aeromodelling. I have shot either rifles, pistols or bows for the last 40 years. Competitive to a high standard with a pistol and rifle UIT and IPSC when I was doing that, but feeling no incentive to do more than state and Australian Open level with Archery. 

I know previous world champion and Olympic gold medal winning archers from several countries. I have friends currently competing at world cup level and at the last and previous Olympics for several countries. I've even sat in McDonalds and talked random crap with KiSik Lee.

I personally know people who personally know you.
Who I am is not important, because I don't ask for opinions.

I just like to see people actually know what they're talking about, so I like asking questions. 

I've seen an awful lot of high performance archers who know how to put an arrow in a target consistently, but have no idea about something so simple as relative airflow in a flying object, or at which position a bowstring has the highest stress. 

I like robust evidence, because as everyone who actually drives knowledge forward knows, opinions are as important as the facts that support them.


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## theminoritydude (Feb 11, 2013)

The function of high FOC is precisely to reduce the error from random air movement, given similar or comparable inputs.

To not understand this simple idea, is to claim to have fully claimed to understand a cookbook, but have never tried to prepare a single dish.


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## whiz-Oz (Jul 19, 2007)

theminoritydude said:


> The function of high FOC is precisely to reduce the error from random air movement, given similar or comparable inputs.
> 
> To not understand this simple idea, is to claim to have fully claimed to understand a cookbook, but have never tried to prepare a single dish.


So, you can explain it in your own words, covering exactly how it works, if it's so simple? I mean, you'll cover things such as the change in angular response to atmospheric disturbance with increased FOC, taking into account the greater lever arm and also lever arm mass and how that relates to time aligning to the relative airflow? 

Maybe you'll explain this contrasted to the effect of the loss or gain of complementary or antagonistic side area based on the direction of flight of the center of mass of the arrow, as compared to its angle of attack at that time to the relative airflow? 

I mean, in a dynamically changing environment, all these things add up. There are lots of traps to fall into. People who explain FOC by using aircraft which are designed to generate lift in opposition to gravity to achieve height stability fall into the trap all the time. 
You'll explain using actual figures of comparable conditions using standard internationally accepted units of measure?


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## chrstphr (Nov 23, 2005)

whiz-Oz said:


> So, you can explain it in your own words, covering exactly how it works, if it's so simple? I mean, you'll cover things such as the change in angular response to atmospheric disturbance with increased FOC, taking into account the greater lever arm and also lever arm mass and how that relates to time aligning to the relative airflow?
> 
> Maybe you'll explain this contrasted to the effect of the loss or gain of complementary or antagonistic side area based on the direction of flight of the center of mass of the arrow, as compared to its angle of attack at that time to the relative airflow?
> You'll explain using actual figures of comparable conditions using standard internationally accepted units of measure?


You didnt seem to cover any of that when you posted out this 



whiz-Oz said:


> I fully endorse shooting the heaviest points you can fit in if you don't have to compromise anything else. I totally believe in maintaining an adequate margin of stability to get the job done.


You will explain using actual figures of comparable conditions using standard internationally accepted units of measure for why you endorse using the heaviest points you can? 

Why give up sight marks? Why are you not using 90gr points? What is your proven published researched data to prove your endorsement? 

All i see is your opinion in that statement. 


Chris


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## whiz-Oz (Jul 19, 2007)

chrstphr said:


> You didnt seem to cover any of that when you posted out this
> 
> 
> 
> ...


So you totally missed that part about weight alone being a factor which inhibits wind drift? That's already covered in http://journals.sagepub.com/doi/abs/10.1177/1754337111418876

I mean, nice try, but I'm not expousing anything that isn't already known. I'm pointing out what isn't known. I also mentioned "If you don't have to compromise anything else". I have never had issues getting to 90 metres. 

You're not defeating my argument by attacking my questions. You're just providing evidence that you can't answer them.


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## MagneticLobster (Dec 24, 2012)

whiz-Oz said:


> I have never seen one test other than Clarance Hickmans, where FOC ONLY was changed. Only points and thus weight and FOC, so people are arguing for one thing, while changing two. Weight is a legitimate factor for reducing wind drift if no compromise is made for speed loss, leaving a projectile with more time to be affected.


I agree that it would be nice to conduct tests where FOC -- and nothing else -- is changed.

Now how would I do that?

If I have arrow A, I'd like to compare it to arrow B which has different (say, higher) FOC, but is otherwise identical to arrow A.

So how do I go about constructing arrow B?

To increase FOC, I'll need a heavier point. If arrow A has a steel point and arrow B uses a point that is the identical shape and size, but made of tungsten, that would work.

But now I need to somehow reduce mass in arrow B to compensate for the heavier point. Presumably I want to use the same nock and fletching, so the mass has to come from the shaft.

So I need a lighter shaft. But I have to keep the outer diameter the same -- surely we care a lot about diameter when we're shooting in the wind.

So I could change the inner diameter. But then arrows A and B won't have the same spine.

So maybe I use a different material. Perhaps an aluminum shaft for arrow A and carbon for B, selected so that the shafts have identical outer diameters and identical spine.

Now supposing that I have an arrow factory available to produce exactly these hypothetical shafts, is it the case that carbon and aluminum shafts having the same spine will flex in exactly the same way?

You seem to be upset that no one has conducted a test that seems to be quite difficult to do. Clarence Hickman must have had some clever trick to do this.


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## nuts&bolts (Mar 25, 2005)

MagneticLobster said:


> I agree that it would be nice to conduct tests where FOC -- and nothing else -- is changed.
> 
> Now how would I do that?
> 
> ...


Two Easton X10s. 120 grain steel point in Arrow A. 120 grain tungsten point in Arrow B. Same total mass, if you use the same nocks, same vanes (brand, model and even COLOR), same X10s (same weight code), same point weight. The tungsten point arrow has more FOC because the 120 grain tungsten point has a higher density, so even though a 120 grain tungsten point weighs exactly the same as a stainless steel 120 grain point, the tungsten point is shorter, so the tungsten tipped arrow has slightly more FOC. Since you use the same X10, same length of tube, same outside diameter, same spine rating, same weight code, same nocks, same pin nock bushing, same hot melt glue, and especially if you weigh the chips of hot melt glue, you can actually get two arrows to the same weight reading on the grain scale (accurate to 0.2 grains). Must level out the grain scale, and protect the scale from any air currents (measure the arrow weight indoors), on a dead level surface. Yes, the TYPICAL way to get more FOC is to use a heavier point weight. But, if you want to isolate to one factor, then, the point weight must be the same and you can only use material density to get same weight, but higher FOC. If you really want to go whole hog, you need a control group and a double blind experiment.


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## nuts&bolts (Mar 25, 2005)

MagneticLobster said:


> I agree that it would be nice to conduct tests where FOC -- and nothing else -- is changed.
> 
> Now how would I do that?
> 
> ...


Now if you want to be the REAL true expert in testing, machine some points from depleted uranium. Now we're talking some real density changes when compared to stainless steel. I'm not holding my breath to see if any "expert" machinists are going to machine anything like this. Now, an enterprising mad scientist could take a nibb point and fill it with lead, to try to get a 120 grain point, and compare to 120 grain stainless steel points versus 120 grain tungsten points. The challenge with a lead filled nibb point would be to get it to spin balance properly.


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## MagneticLobster (Dec 24, 2012)

nuts&bolts said:


> Two Easton X10s. 120 grain steel point in Arrow A. 120 grain tungsten point in Arrow B. Same total mass, if you use the same nocks, same vanes (brand, model and even COLOR), same X10s (same weight code), same point weight. The tungsten point arrow has more FOC because the 120 grain tungsten point has a higher density, so even though a 120 grain tungsten point weighs exactly the same as a stainless steel 120 grain point, the tungsten point is shorter, so the tungsten tipped arrow has slightly more FOC. Since you use the same X10, same length of tube, same outside diameter, same spine rating, same weight code, same nocks, same pin nock bushing, same hot melt glue, and especially if you weigh the chips of hot melt glue, you can actually get two arrows to the same weight reading on the grain scale (accurate to 0.2 grains). Must level out the grain scale, and protect the scale from any air currents (measure the arrow weight indoors), on a dead level surface. Yes, the TYPICAL way to get more FOC is to use a heavier point weight. But, if you want to isolate to one factor, then, the point weight must be the same and you can only use material density to get same weight, but higher FOC. If you really want to go whole hog, you need a control group and a double blind experiment.


OK, I think you've got it about as close as one might hope. Nice.

Some minor issues, if we're being nit-picky:

(1) You would want the shank length of the points to be the same, since this affects how much of the shaft will flex, and thus affects the effective spine.

(2) The tungsten points don't have the same shape, and so the airflow won't be the same for the two points (I haven't read Park's article on this subject, but based on the abstract this appears to be the case).


I think the use of a shooting machine would eliminate the need for a double-blind study.


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## whiz-Oz (Jul 19, 2007)

Actually, all you need is exactly what Hickman did. An arrow with a moveable internal mass. By fixing the mass at various positions within the arrow, you can change the FOC at will, without affecting any other properties which will cause any issues. Any spine variations will be countered for by only using one arrow tested against it's own performance.

You could have a range of known good arrows established by ensuring that they already shoot into their own holes at your testing distance with no atmospheric disturbances. This also calibrates the ability of the shooting machine operator.

You set the arrows up with varied internal weights to give a range of FOC and randomly number them.

Then you just remove as many variables as possible by shooting the same single arrows into the same targets under as similar conditions as possible. One constant target per constant arrow, as many times as is possible. 

With no knowledge of which FOC's are where and keeping the arrows identified by numbers, you achieve a blind test. With varied sequence of arrows across varied atmospheric conditions, you can reduce the effect of changing environmental conditions over the testing period. 
Statistical analysis of the results will reveal any specific tendencies for one arrow to do better than any other over hundreds of shots, or preferably a thousand.

Then the entire thing gets done again by someone else and the results compared for consistent results.

Then the actual FOC of the arrows is measured, and compared against both sets of results to see if they're consistent with the expectation that higher FOC achieves a lower impact variation.. 
Keeping the FOC unknown over two lots of seperate tests achieves a double blind. 

Most people have no idea that testing requires careful test design and requires typically thousands of data points. 

I'm in no way upset that this hasn't been done. I just know it hasn't, but people carry on like it's an established fact.


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## theminoritydude (Feb 11, 2013)

whiz-Oz said:


> So, you can explain it in your own words, covering exactly how it works, if it's so simple? I mean, you'll cover things such as the change in angular response to atmospheric disturbance with increased FOC, taking into account the greater lever arm and also lever arm mass and how that relates to time aligning to the relative airflow?
> 
> Maybe you'll explain this contrasted to the effect of the loss or gain of complementary or antagonistic side area based on the direction of flight of the center of mass of the arrow, as compared to its angle of attack at that time to the relative airflow?
> 
> ...


You haven’t been reading my previous comments on this thread, have you? But I guess I can’t blame you, you were too busy trotting out counter arguments to properly digest the implied meanings in the shorter, less tedious explanations.

Also, this thing about A.O.A., please don’t lump me in with the crowd you just mentioned. It’s a specific term that is used in relation to wing chord. Please don’t assume EVERYONE doesn’t understand this before you (again) betray your tendency to underestimate the technical competency of others.

Rifle shooter in AUS? HA! Which range(s) may I ask?


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## theminoritydude (Feb 11, 2013)

You chat with KSL at McD. I get wedding gifts from major Korean brands. I guess I win.

Come on.

Lots of people work in the aerospace industry. A janitor can work in a hangar in Boeing. Could you please be more specific?


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## theminoritydude (Feb 11, 2013)

You know whiz-oz, in my previous encounters with you, it appeared that you knew exactly what you were talking about. But when it came down to FOC, your dismissal of its advantages in reduction of overall drag baffles me. It seemed almost like you were trying very hard to disprove something that a person with your expertise should know like the back of your hand.


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## whiz-Oz (Jul 19, 2007)

theminoritydude said:


> Also, this thing about A.O.A., please don’t lump me in with the crowd you just mentioned. It’s a specific term that is used in relation to wing chord. Please don’t assume EVERYONE doesn’t understand this before you (again) betray your tendency to underestimate the technical competency of others.
> 
> Rifle shooter in AUS? HA! Which range(s) may I ask?


Essentially, I stopped relying on you for factual content years ago. I noticed that you didn't seem to have the basics and like to refer to things that can't be verified like "secret testing"

Angle of Attack is only specific to wing chords? Ah, no. Guess I haven't assumed wrong after all. 

You may wish to avail yourself of every Australian State's firearm legislation before and after 1996. The NRA would have you believe that Australia has no guns at all since then. 

I can't wait to see what you'd do with a list of most of the gun clubs in the QLD Wide Bay area, all the Pistol and Rifle Clubs in South Australia prior to 1996 and SA, NSW and QLD military ranges prior to 2002.


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## theminoritydude (Feb 11, 2013)

Your skill at shifting of goal posts deserves applause.









First, you argue that some people argue for use of FOC based on aircraft design for lift, implicitly suggesting that is where I’m coming from. Whether or not that was your intent, as a clarification, without ambiguity to our assumptions when dealing with the specifics of arrows, we are talking about drag reduction, not lift, although strictly speaking their equations are derived from similar variables, which is where the confusion starts.

Whiz-Oz, you’re reading too much into my question of which range you shoot at. I suggest that you sit down and have a warm glass of milk, relax, and not assume everyone has no access to documentaries on the internet about mass shootings.


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## theminoritydude (Feb 11, 2013)

Also, I don’t recall ever conversing with you “years ago”. Could you help jog my memory?


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## theminoritydude (Feb 11, 2013)

Perhaps, you were(are) using a .....pseudonym?


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## PregnantGuppy (Jan 15, 2011)

> They are both opinions. Here let me demonstrate.
> 
> Someone designs a car. When asked what reasons he had for designing this car, he says he designed it to save gas, because other cars burn too much fuel traveling X distance, through the use of a specific component. Does not specify how component actually saves fuel.
> 
> ...


I don't believe you understood my point. When discussing what the designer had in mind when making tungsten points (regardless of how the designer intended for them to work), there is no more definitive experiment than asking the designer himself. And that is literally the information provided by whiz. I don't see what further experiemental results you could want there. Meanwhile, on the question of how tungsten points actually affect archery performance, we can definitely produce various other numbers.



> i sent you the link.
> 
> angle of attack matters which is what FOC gives you.


I did see the link, thank you. However, it only further highlights the problems with your arguments. First of all, the article never mentions FOC at all, making your last claim unsubstantiated. I do believe one of Tapley's artciles talks about angle of attack (or offset angle in his terms), but he does not relate it to FOC either. Furthermore, even if we did establish a correlation between FOC and angle of attack, this graph doesn't agree with the idea that more FOC is always better, since the drag increases for both positive and negative angles, and we can presume that minimal drag is desired. And lastly, even if we did somehow figure all of that out, you would just be moving the goalposts to showing that drag is directly related to a significant improvement in scores or other metric of archery performance. So ultimately we still just need more data to be able to draw any such conclusions.



> And therein lies the problem. No one can tell you when your "trade-off" occurs. There are too many other variables in each archer's shot and kit. I know where my trade-off occurs by testing my set up and I suggest you will have to do the same. And the funny thing is, it isn't that difficult. But it will require you to go out and test it for yourself. If I had to make a rule for when the "trade-off" occurs, it would be when the extra point weight prevents you from effectively shooting a chosen distance. So how do you do that? I think you know.


All right, now we have something. We can agree that at a certain point, FOC is no longer beneficial, and that every archer needs to experiment and find what works best for them in this regard, since there are too many variables involved. I wholly believe in this philosophy, and I have never said anything to the contrary.

But it does beg the question, then, of why so many people keep offering blanket statements like "more FOC is always better" and then try to back it up with misread science articles. That is ultimately the problem that is present here. And without trying to seem vindictive, you yourself have posted things of this sort. In this thread, you posted the quotes


"Consequently it is best to use a heavier rather than a lighter arrow point"
"Having a high FOC for an arrow provides two principal benefits - better arrow groups and reduced wind sensitivity"
Indeed, there could be further qualifiers, and you may understand that yourself and assume it to be clear to any reader. But that's simply not always the case, and it ends up perpetuating pseudo-facts without any real backing.



> You seem to be upset that no one has conducted a test that seems to be quite difficult to do. Clarence Hickman must have had some clever trick to do this.


I can't speak for whiz, but I am personally not mad that such a test does not exist. What I do find upsetting is that even though such a test does not exist, people go around claiming results like it's the most obvious thing in the world. I'm all for using science in the sport, but let's use it correctly.



> You chat with KSL at McD. I get wedding gifts from major Korean brands. I guess I win.
> 
> Come on.
> 
> Lots of people work in the aerospace industry. A janitor can work in a hangar in Boeing. Could you please be more specific?


That's just a cheap attack, man. The guy was literally asked for credentials, and you berate him for providing them? And he has a right to provide as little information as he desires. In today's age, putting out too much personal information is simply not the ebst decision.


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## theminoritydude (Feb 11, 2013)

I don’t call referring to somebody having a meal with “someone” at a restaurant a “cheap attack”. Do you?


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## theminoritydude (Feb 11, 2013)

Of course you do.


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## theminoritydude (Feb 11, 2013)

"When discussing what the designer had in mind when making tungsten points (regardless of how the designer intended for them to work), there is no more definitive experiment than asking the designer himself."

Have you heard of these events called "failed designs"?

Just to be absolutely sure, are we referring to the design of Tungsten (I love tungsten) points, or the Gen 2 Barreled shaft?


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## theminoritydude (Feb 11, 2013)

Hello? Is everyone asleep?

God! What timezones are you guys in?!


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## whiz-Oz (Jul 19, 2007)

theminoritydude said:


> Your skill at shifting of goal posts deserves applause.
> 
> View attachment 6537959
> 
> ...


So, you realise that your graphic with the definition of Angle of Attack specifically disproves your assertion that it applies specifically to wing chords?

Why would you post that? I thought the idea was to support your point. 

Why is it that you assume that I still shoot rifles? 

You're also wrong about me implying anything. Maybe you need the warm milk yourself. 

You are however, correct about the drag reduction, but we're still talking about a lift component. That's what fletches generate when they're offset to the relative airflow.


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## theminoritydude (Feb 11, 2013)

I might ask you to specify which phrase disproves my assertion. But I’m guessing you’re going to talk about something else so I’ll leave that up to you.









Oh, so now we are going to debate about the specifics of when you stopped shooting rifles?
You really like shifting the debates around don’t you? 

Ok. My bad. I lost the whole argument because you may or may not still be shooting a bow now.


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## whiz-Oz (Jul 19, 2007)

Actually, I lost it because I bothered replying to you. I should know better. 
I think I'll just address logical commentary in future.


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## theminoritydude (Feb 11, 2013)

Oh, forget about that pseudonym. Don’t want to confuse postings between AT and AF, because if you were referring to the discussion about the low drag of a barrel shaft (which involved Jim), it’s going to be a giveaway but I want the others here to have their fun too.


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## tooold (Jul 26, 2015)

Can we cut to the chase here. Am I wasting my time shooting heavy points or am I not?


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## Bender (Dec 6, 2006)

tooold said:


> Can we cut to the chase here. Am I wasting my time shooting heavy points or am I not?


Yes. No. Maybe. Only you can decide that for yourself.

The only "waste" going on is the time spent reading through these posts. I'm off archery for a few weeks until my next Dr appointment so it's no matter to me.

Besides, the whole thread does have that "train wreck" quality to it, doesn't it? Its horrifying but you just can't look away.


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## PregnantGuppy (Jan 15, 2011)

tooold said:


> Can we cut to the chase here. Am I wasting my time shooting heavy points or am I not?


If your goal is to maximize your performance, then it is never a waste to try out different things, as long as it's within your means. I have never said anything to the contrary in this thread, and if heavier points work for you as they seem to work for most people, then that's great.


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## DarkLightStar (Apr 7, 2016)

Attacking someone's credibility simply because they are using an anonymous username is a bit of a low blow. There are plenty of reasons that people choose to do it, and not all of them are nefarious. Hello, it's the internet.

From my experience, a friend who purchased the x-spot x10 tungsten points was very pleased with them. I chose the easton points because that is what I've used for years and, frankly, this option was not available when I made my purchases.

As long as the fit is good, I don't see the drawbacks of choosing a cheaper point so long as it satisfies the weight requirements and FOC parameters that the archer seeks.

Perhaps Easton's tungsten is made from higher quality molecules or fairy dust...dunno. It's nice to have some options available. It keeps the market more honest.


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## theminoritydude (Feb 11, 2013)

Oh you wouldn’t say that if you knew exactly who it is.


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## DarkLightStar (Apr 7, 2016)

theminoritydude, 

Actually, I wasn't talking to you. I don't know why you've survived as long on this forum as you have, but that's just how things are. I think trollish behavior should be dealt with a little more effectively on this forum, but it is not my call to make. Only my opinion. And maybe your posts are not trollish...but to me, they seem like it. 

Back on topic:

I'm a fan of high FOC if your arrows have the cast to reach the distance you seek to shoot with plenty of juice left over. I've shot clout with my Olympic recurve setup and saw decent groups at 150 yards. So, really, whatever spines the arrow well seems to be something worth chasing rather than chasing FOC for FOC's sake. 

At least according to what I remember of Tapley's FOC findings, most benefits of a high FOC are realized much further than 70 meters, anyway. I think it's probably more worthwhile to chase a correct spine/poundage combination than chase the fractions of a point that tungsten might bring over stainless steel. 

Many archers, from what I've seen, would benefit more from a well-tuned bow/arrow system than anything else. I've seen so many archers recently who are preparing for Nationals and shooting at 70 meters whose bare shaft tuning at 30 is atrocious. 

I don't think you're going to find good results in either Easton or X-spot tungsten points if your bare shaft is landing over a foot stiff away from your arrows at 30 meters. But that's just me.


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## theminoritydude (Feb 11, 2013)

Dark, it is my understanding that you may or may not have been talking to me, but know a real troll when you see one. Hence the reply.

Very unfortunate that it had to come to this for characters like them, forced by circumstance to to speak against an idea they know to be true, and it comes off as clumsy, and ambiguous.

I don't troll. I speak my mind, it is my style of interaction where I seek some "back and forth", else you end up with one side pouring out material without good pacing for the reader(s), and in time lose their interest if they have any, like how this post is headed.

Again, for someone of self proclaimed technical superiority to say that FOC doesn't do anything for accuracy in atmosphere, that is appalling. And it is appalling precisely because of who he is.


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## nickle (Sep 25, 2017)

it has been stated that tungsten points have more f.o.c. than steel of the same weight. how do you measure that? what is the difference?


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## theminoritydude (Feb 11, 2013)

Slap on a tungsten point and compare the arrow with one that has an SS point. Balance them. Side by side.


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