# Let's talk physics



## montigre (Oct 13, 2008)

There was a very comprehensive discussion on this topic a few years back that you may find interesting. Here's the link: http://www.archerytalk.com/vb/showthread.php?t=1681136


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## tuckerjt07 (Dec 18, 2014)

The 7.75" will get the arrow off of the string quicker, in most instances anyway. What this means to you the shooter is that there is less time between your release and the arrow being separated from the bow for you to influence the shot.


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## aread (Dec 25, 2009)

Physics should not be the primary consideration in selecting a new bow. The main thing that you should look for is bow fit at your optimum form.

If the bow fits and your form is good, the difference between 7" & 7.75" brace height will be negligible. 

If the bow fits and your form is good, the "tightrope-walker's-pole" effect will be negligible.

JMHO,
Allen


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## GWFH (Jan 22, 2006)

Im short and prefer the steeper sting angle of a 38-40" bow.....so I wouldnt second guess that.
I dont think anyone can convince themselves that a longer bow doesnt stabilize better, if theyve given both a fair shot.

As for bh.....
By itself it means little to me.
It comes down to riser geometry, most importantly the relation/style of pockets and where they are in relation to grip.
Its not as simple as reflex/deflex like it was 25yrs ago.
Bows are drastically different designs from then, and even amoungst themselves today.
Cant consider a BH value by itself today, need to evaluate the system.


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## GWFH (Jan 22, 2006)

tuckerjt07 said:


> The 7.75" will get the arrow off of the string quicker, in most instances anyway. What this means to you the shooter is that there is less time between your release and the arrow being separated from the bow for you to influence the shot.


But still on the rest for same amount of time
.....and now more time with single point contact instead of string contact (2pt)

I dont agree with this logic from your post or my (rhetorical) reply.
I see it as the geometry difference is what determines how prone one is to "influence the shot"


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## tuckerjt07 (Dec 18, 2014)

GWFH said:


> But still on the rest for same amount of time
> .....and now more time with single point contact instead of string contact (2pt)
> 
> I dont agree with this logic from your post or my (rhetorical) reply.
> I see it as the geometry difference is what determines how prone one is to "influence the shot"


That's dependant on what sort of rest you are shooting first off. Second, your rest, if a tongue, is more forgiving than the string.


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## GWFH (Jan 22, 2006)

So its sounding like you are in agreement with evaluating the system as a whole, not just the BH number?

Because if we dig deeper on the time on string theory, speed plays in too. Since we know an arrow stays on string well past the brace position during the shot, most of todays bows even target bows have a ton of overtravel compared to years ago. Yet you dont see top shooters installing string stops to make their bows more forgiving.


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## fanio (Feb 1, 2011)

Indeed - because a string stop is "one more thing that can fail".


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## Padgett (Feb 5, 2010)

If you have money to burn then just get a top end target bow new offering from a major company and take a risk and you will probably end up with a great bow. 

If you are smart you will pay attention to some of the top shooters in the world and see what bows they are shooting and winning with and then pick one of them and find one in the classifieds and enjoy. This choice will have a little more confidence attached to it because the bow is a proven winner. For example last year you could have bought for probably 650 bucks a hoyt pro comp xl that won more than one asa known 50 tournament and shooter of the year from my buddy who used it to do so. Sure you can drop well over a thousand on a new one but a used one that is proven to win is a different way to look at it.

As far as your physics start to this thread, I have been paying attention for quite some time and from what I can see many of the old thoughts on brace height and ata are kind of a thing of the past. It is way more important to get something that fits properly and is proven to produce really solid and reliable results.


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## Lazarus (Sep 19, 2005)

JV NC said:


> I'd like to understand the physics behind why one "should" be better than the other. The old standby of "You'll have to see which one you like best" isn't very comforting, when you're spending $$.


I'm sorry, but I can't help with the physics behind it. I'm not an engineer, just a shooter. This I will say, if you want a longer AT bow get it, and enjoy the awesome string angle and hold. Then "move to the bow." So many people think you can buy a bow of "X" ata or "X" brace height and that automatically translates into accuracy. No. "Moving to the bow" that you are shooting at this precise moment is what produces accuracy (along with decent tuning and arrows of course.) 

.02


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## JV NC (Dec 9, 2005)

^^Never heard that term. Sorry.


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## montigre (Oct 13, 2008)

Yes, please explain "moving [to] the bow"--


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## Lazarus (Sep 19, 2005)

JV NC said:


> ^^Never heard that term. Sorry.


I make stuff up like that all the time.  It's worked for so many that have gone before me so why not?

"Move to the bow" very simply means; learn to shoot it. For the purposes of this discussion, a bow is a static machine. Your body is not, therefore, "move to the bow."


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## JV NC (Dec 9, 2005)

Let me ask a more broad question..........

From a physics standpoint, everything I've been led to believe tells me a 40" ATA bow is more forgiving than a 25" ATA bow.

Why?

Is it in riser length?


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## Lazarus (Sep 19, 2005)

^ Could be a lot of reasons. The first one that comes to my mind (strictly from a shooters standpoint,) is that it will aim better. Aims better, hits better. That's all my shooters mind really needs to know. But that's just me.


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## montigre (Oct 13, 2008)

Lazarus said:


> I make stuff up like that all the time.  It's worked for so many that have gone before me so why not?


Sadly, this is all too true..... 

Moving to the bow, I thought you were getting at some woo woo description of just shooting it, but wanted to verify it before saying anything....lol!!


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## EPLC (May 21, 2002)

JV NC said:


> Let me ask a more broad question..........
> 
> From a physics standpoint, everything I've been led to believe tells me a 40" ATA bow is more forgiving than a 25" ATA bow.
> 
> ...


For me it is a simple matter of string angle. Generally speaking, the longer the ATA the less severe the string angle. The shorter the string angle the more difficult it is to get the string to intersect the corner of the mouth while touching the nose. I like the fit better and I'm only 5'9"...


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## SonnyThomas (Sep 10, 2006)

JV NC said:


> I may be in the market for a new target bow, soon. I'm 6'1". I have no idea "why", but I have it in my head a 40" ATA bow would be better for me than a 37" ATA bow.
> 
> Truth or myth?
> 
> ...


Bow fit, just so paramount....

My top height was 5 foot 11 inches. My shortest target bow, a Bowtech Old Glory, had a 37 1/4" ata and it shot great. My longest, a Martin Shadowcat, had a 41 1/2" ata and it shot great.
I have two target bows right now, both Pearsons. A MarXman with 37 1/2" ata and a MX2 with 40 1/4" ata. Both shoot great. 

Here's a pic from 20 yards alternating back and forth ever so many shots with both the Pearson bows. Both bows had one arrow slip out more than I wanted. The same arrows were used with both bows and not what you would call Indoor arrows, not at 322 grs counting a light 80 gr field point. And I don't shoot spots, ask anybody...

Something over 40 shots, but called it 40 shots, 398/400.


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## bigHUN (Feb 5, 2006)

Last several years, I had a 40" ATA swap it for 38"ATA then I realized I like the longer ATA string angle better so me got to the 40" ATA back again. 
You will never know without trying it...
Through many years of swapping around and shooting bows we develop preferences, I know exactly what I am looking for (regardless of Brand) and that is in front of me whenever I start reading about some new technologies. 
I want my bow to be easy and quick tuneable; lightweight so I can manage the total weight as I want and where I want it to be; stable material from riser to string/cables; high precision fabrications to tightest tolerances; if I want to I can swap the limbs or cams or string/cables in less then an hour back to the scoring; I want to shoot lot of arrows every day (me a FITA guy) and not to get tired @ 57-58 lbs holding 24 lbs; blablabla
I like that I've read somewhere here @ AT : "what is a best beer" ?


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## JV NC (Dec 9, 2005)

What would make someone shoot a shorter or longer ATA bow for indoors v. outdoors? 

Unless there's a quirk (with the bow or the shooter), wouldn't a longer ATA bow always (inherently) be more stable?

I'm not trying to debate this. I'm looking for insights - before I make a major bow purchase. I've owned a Bowtech Constitution.  I shot it well. I currently own a Specialist. I like it a lot, also. I'm thinking of a new 3D bow....and I'm torn between 37" and 40" ATA. Both bows are the same IBO speeds. I'm going to need to shoot 65#'s (or so) to get to ASA speeds (at my DL). So, I'm also thinking the longer ATA would have (same bow, otherwise) a smoother draw cycle.

I appreciate your input.


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## SonnyThomas (Sep 10, 2006)

I'm unaware of Bowtech's cams, but cams make the draw cycle, not totally the ata. Two different cam systems, same 55 pound draw weight, my 40 1/4" bow draws harder than my 37 1/2" bow. The 37 has large cams with smaller modules. The 40 has small cams with larger modules.


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## JV NC (Dec 9, 2005)

New bow would not be a Bowtech, but would be the same cam system (between 37" and the 40" ATA's).

In other words..........same bow.......different ATA's.


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## Padgett (Feb 5, 2010)

The specialist is a 330 ibo bow and you are going to have trouble finding a target type bow that is faster than it is, I guess you could go to a more hunting specific bow that has a very high ibo but then you loose the target bow appeal. To me with the specialist you just need to do some work with your arrow selection and come up with a arrow setup that is light enough to produce the asa speed you want and also perform for you.


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## SonnyThomas (Sep 10, 2006)

JV NC said:


> New bow would not be a Bowtech, but would be the same cam system (between 37" and the 40" ATA's).
> 
> In other words..........same bow.......different ATA's.


Cam systems vary on different brands of bows....


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## JV NC (Dec 9, 2005)

Sonny......

I'm talking about the same bow company. Same bow (model). ONLY difference is ATA.


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## JV NC (Dec 9, 2005)

Padgett said:


> The specialist is a 330 ibo bow and you are going to have trouble finding a target type bow that is faster than it is, I guess you could go to a more hunting specific bow that has a very high ibo but then you loose the target bow appeal. To me with the specialist you just need to do some work with your arrow selection and come up with a arrow setup that is light enough to produce the asa speed you want and also perform for you.


So, if they made a 40" ATA Specialist.....would you shoot it (over the current design)? Why or why not? Same specs (IBO). ONLY difference would be the ATA.


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## SonnyThomas (Sep 10, 2006)

JV NC said:


> Sonny......
> 
> I'm talking about the same bow company. Same bow (model). ONLY difference is ATA.


Not a Bowtech, as you said. Okay. So not knowing the bow you might buy, bow companies make different cams for their bows. My Pearsons, Legend cams, LSM and LS3 cams. Hoyt makes different cams for their bows, Cam & 1/2 of large and small cams, Spirals and a couple of others I think.


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## JV NC (Dec 9, 2005)

I don't know any other way to describe this to you....other than to ask you NOT to read into it.

It's the EXACT SAME BOW.....(same cams....same IBO....same EVERYTHING).....except one is 37" ATA....and the other is 40" ATA.


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## Mahly (Dec 18, 2002)

Here is why I would pick the 40" over the 37" (and over the 25" in that scenario)

1) FIT. String angle and contact points. For me, Longer is better. (admittedly, my DL is longer than most)
2) Peep to eye distance. The closer the peep is to the eye the better IMO. I don't know of any benefit to moving the peep away from the eye.
3) Stability. All else being equal, the longer bow will be harder to rotate around the grip (think level). 

NOTE: cam design, and limb angle will play a large roll in this as well. A more parallel limb bow will have less ATA at full draw than a bow with less parallel limbs. The parallel limbs move the axles toward each other, the more perpendicular limbs move the axles front to back and less up and down. This makes ATA even more important on parallel limb bows (they need to start with more to end up with the same amount). Cams that move the string farther from the axles will have a larger effective ATA than cams that bring the string closer to the axles at full draw.

As for brace (not dependent on ATA) I think the longer brace makes for a bow that is more forgiving (however slight) of tuning errors. 
Imagine and arrow on a table with a straight line drawn under it. Now while holding the nock end of the arrow, push the arrow off line at the front of the arrow so your finger can touch the line. The arrow is now at a slight angle to the line. Now while still holding the nock in place , slide that finger to the direction of the nock. as you move, the arrow moves more out of line. At first it isn't a huge amount, but as you get closer to the nock, every inch makes a bigger change than the last. Basically, the shorter you go with BH, the more critical it gets, and not just on a linear scale. So the difference between a 5 and 6" brace is MUCH more than the difference between 7 and 8". Moving your rest 1/32" on a bow with a short BH will give you more of a change in tuning than the same adjustment would on a long BH bow. 
I think too much weight is given to "lock time", but there is something there as well.


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## Padgett (Feb 5, 2010)

You know, I got a bowtech cpxl in august and I just spent 8 months shooting with it waiting for it to perform anywhere near my specialist and it failed and I am no longer shooting it. It tuned perfect and I loved the grip and the draw cycle and the look of the bow but in the end when I shoot the specialist the arrow hits exactly behind the pin every time every day every year weather it is tuned or not. So if I got a 40 inch specialist I would shoot it and I would give it the same chance that I gave the cpxl and it has some huge shoes to fill but if it did fill them I would shoot it. 

I don't pick a bow because of some random numbers from ibo to ata or brace height, I choose a bow because the bow takes care of me by sending the arrow to the target right behind my pin.


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## JV NC (Dec 9, 2005)

Good stuff, Mahly. I can't (in MY mind) think of a scenario where (as long as we don't delve into the absurd) longer (ATA) wouldn't be "better" for a 6' archer......for target shooting. Hence this thread.

The two bows I'm considering are LITERALLY the same bows.........less the 3" ATA difference.


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## JV NC (Dec 9, 2005)

Padgett......if you don't want to answer my question, that's fine....lol.



> I don't pick a bow because of some random numbers from ibo to ata or brace height,


Neither do I. But, if there's something inherently "better" about one over the other, I'm also smart enough to not discount that. I asked you a pretty simple question in my mind.....but, to make it even simpler, I'll try one more time.....

If you'd never shot a Specialist, and you were going to buy one.......and they offered it in 37" or 40" (otherwise....THE SAME BOW), which one would you choose? (and why?) The fact that you're going to buy a Specialist is a foregone conclusion. Your only choice is which ATA bow you're going to buy.


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## Padgett (Feb 5, 2010)

I am a performance based shooter, I make my decisions on methods of shooting and equipment all based on me shooting that piece of equipment and once I have put enough time into it I make a decision weather or not it worked. I believe that is how I answered your question by telling you that I would shoot it and see how it performed. I don't read specs and make a performance decision for a product. 

Bowtech is a tough company to put a lot of stock into their target bows because they don't sponsor top end shooters at the pro level so you aren't going to see them winning any pro level tournaments anytime soon on a regular basis so you are picking one and shooting with it on blind faith that it could be shot at that level. I actually believe that a specialist could be shot at that level because I have shot it. That is what levi morgan has done for elite, last year he picked up a parallel limb slightly long hunting bow and shot it at the highest levels and given that company what matthews and hoyt and pse have had for a while. This year they got him into more of a target bow offering and he is doing the same with it now giving their target bow that faith that will make it easier for a guy to pick one.

Sooner or later you will learn to set a bow up to a solid draw length and get it to fit your body and then find out if it sends the arrow behind the pin or not, then you go win with it.


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## JV NC (Dec 9, 2005)

You could have just said....."I'm not going to answer your question".


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## GWFH (Jan 22, 2006)

JV NC said:


> So, if they made a 40" ATA Specialist.....would you shoot it (over the current design)? Why or why not? Same specs (IBO). ONLY difference would be the ATA.


I owned a 33" drenalin first and then bought a 37" drenalin ld....same bow other than 2" of riserabove and below the pockets
I owned a 36" dst first and then bought a 40" dst....same bow other than 2" of riserabove and below the pockets

I sold each of the shorter version within 6months of buying the longer.
Now I know just to stay longer.

Another example is my contender elite xt2000 (38.5")
I tried it with the longer (41"+) xt3000 limbs and went back to the 2000s.
But only because the 38.5 gave me enough string angle I needed, and it kept speed reasonable, since the longer limbs dogged out with my dl and weight......and I was using for 3d.

First, it needs some balance of application.....if I only shot paper, it would probably still have 3000s on it since I liked the string angle even better. But since I was fine with 2000s, I checked the "fit" box and moved to performance consideration.
At 27.625" draw, Ill take 40 over 36 all day (of the same bow).....at 6'1" Im thinking you would too.


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## cbrunson (Oct 25, 2010)

I'll take a stab at it.

I'm 5'10" and shoot a Pro comp XL 40". I shoot it very well but have wondered my self if I could shoot the 37" better because I like the feel of the string angle better. I didn't get a chance to shoot one before buying, so I went with the longer 40" based on the stability theories. I've since shot a shorter one and aside from needing a shorter DL to feel right, I think I will be getting the shorter one for my next bow. 

Of course the thoughts of whether I will be able to shoot it as well as my 40" bow have crossed my mind, but then I just remember that records have been set with both bows. The short pro comp set the record at Redding a couple years ago at one down, and the short podium X set the indoor world cup record with a perfect 600 this year, so as far as the bow being stable enough, I would say yes most definately. The only question would be what felt better in your hands.


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## JV NC (Dec 9, 2005)

Great responses guys. That's what I'm looking for.

I won't be able to shoot either (in my DL.....set up the way it needs to be). But, I do have experience with both ATA's. Like everyone else, I'd like to shoot with the outlier being ME.


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## cbrunson (Oct 25, 2010)

The one good thing about the new podiums is the mods on the spirals. A lot easier to experiment with the draw length rather than a cam change. I shoot 29" on the XL but like 28-1/2" better with the short one.


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## JV NC (Dec 9, 2005)

Are you calling the PXE 40" the XL? Just making sure I understand.

Thanks. That's great information. I didn't think about the shorter ATA meaning a "possible" DL difference, but I did shoot a longer DL on the Constitution than I do on the Specialist.


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## Mahly (Dec 18, 2002)

Another minor benefit to the longer DL, less can lean. Though I don't think that would be enough to make a decision, it is there on bows with 1 cable guard.


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## cbrunson (Oct 25, 2010)

JV NC said:


> Are you calling the PXE 40" the XL? Just making sure I understand.
> 
> Thanks. That's great information. I didn't think about the shorter ATA meaning a "possible" DL difference, but I did shoot a longer DL on the Constitution than I do on the Specialist.


Yes. Sorry they were XL with the pro comps.


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## montigre (Oct 13, 2008)

My preferred bow geometry through the experience of trial and error... I'm 5'5" with a 27.5" DL

I have shot Hoyts exclusively for the past 7 years; The bow I shot best (both indoors and outdoors) was a ProElite at 37 1/4" ATA and 7 5/8 BH. I then allowed myself to be sucked into the myth that longer is better and picked up a Vantage Elite 40 1/2" ATA and 7 3/4" BH which I could not shoot out of a paper bag...sold that bow as soon as I was able to handle another following my surgery. Picked up an Alpha Elite 36" ATA and 7 1/4" BH as an interim bow, but had to franken it with Z5 cams for it to shoot comfortably for me. I keep it for when I feel a need for some speed in a target rig. 

I am now setting up a Pro Comp Elite which has a very similar geometry to the ProElite at 37 1/4" and 7 5/8". Aside form having to do a few tuning tricks to overcome the lowered grip, it feels like I'm putting on a well-worn glove and I believe it just may shoot as well as or better than the old ProElite I had. 

I'm not really sure how this type of information would be of much help to someone else though.....


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