# Bow geometry - how does it effect in accuracy



## the.pabst (Nov 6, 2014)

Hello,
this is more or less a physical question about bow geometry and how it helps in accuracy.
I placed this question in competition archery, because I shoot serious target, 3D and field archery. No hunting!

Everybody knows or suppose that a 40" ATA bow (PSE PerformX, Mathews TRX40, Hoyt Invicta 40) with 7" BH is more accurate and has a better forgiveness than it´s own smaler brother (PSE PerformX 3D, Mathews TRX36, Hoyt Invicta 37) with 36-37" ATA and 6,5" BH.
Of course, If there is no stabilizer or just stabilizers with less weight on it, the geometry may effect in accuracy!?
What i´m wondering, if you put a lot of weights on the stabilizers (all in all 30-50oz), I have really no idea, if the advantage of a 40" bow is still there?? With this big amount of weight the bow is really inert in it´s complete movement.
The same thing is with the "hold on target". As long as archery is in full draw, in a nice firm back wall, approx. 20# holding weigt, bow(system) weight is preatty heavy (10 lbs), why could cause that the bigger bow holds better.

Any ideas or experiences?


----------



## 1/2 Bubble Off (Dec 29, 2016)

If you're looking for a scientific, geek math kind of explanation, you won't get that in my post. But here's my take on it.

1) I think the riser itself has a lot to do with it. Reflex vs Deflexed Risers. Not just in the difference in BH but the feel and stability. I wanted to like the Supra Focus XL (hated it), I kinda liked the Perform X but I loved the PerformX 3D. One of the best spot shooters I know, KILLs it with a Supra Focus XL, I shot it a few times at the shop and wouldn't even consider purchasing one.

2) In my experience, the greater the mass of the bare bow, the more stab weight it took for me to get it balanced. This greater mass, lead to fatigue towards the end of a round. For me, I haven't found a 40" bow that I liked regardless of the riser configuration.

3) For me, my happy place is 35-38" for spots and 32-35 for 3D/hunting. Could a 40" bow end up being a great option for me??? maybe.... I know that I struggled to put up consistent scores with bows that long. I put up some really great scores with a 36" PerformX 3D and even better scores with my Peak 38. I even won an IBO State Championship with long bars on a 32" bow.

4) So does a longer bow work better because it's longer? or because it's heavier? I can't possibly answer that question for anyone but me. What I can say is for me, there is a point of diminishing returns as far as ATA is concerned. I also believe the wider limbs/limb pockets help in the stability department too. (TRX/Peak 38)

5) As far as holding weight is concerned.... with cable stops I want to be in the 10-12# (PerformX 3D) area but with limb stops, I like to hold less... 8-10# (Peak 38)


----------



## *SWITCH (Nov 27, 2007)

The stability of a longer axle bow comes mainly from the string angle being steeper at full draw. IE the closer the string angle is to 90 degrees the more stable generally the bow will be. Obviously other things, such as riser geometry are also a factor.

My Conquest 4 is just under 41" axle, 43" if you include the cams. Riser is 28" long.

MY TRX36 is 36" axle, 41.5" including the cams. Riser is a whopping 30.5" long.

To me the 36" is just as stable if not more so. Both have reflexed risers, but the 36 is heavier and a completely different design in almost every way.

Its probable the trx 38 and 40 are more stable than the 36, but maybe not if it's windy on the line


----------



## Stash (Jun 1, 2002)

Agree that the string angle is a huge factor. Easy to show why in person, but tough in text, but basically, the flatter string angle is less susceptible to grip torque. Plus, a flatter string angle allows for a more comfortable and stable nose-on-the-string anchor, and it provides a longer sight radius (distance between peep and sight). Have a look the top pro shooters. You’ll very rarely find one shooting a bow with a string angle sharper than 90 degrees.

So yeah, you don’t want to go under 90 degrees string angle, and that means a longer ATA bow, especially for people with longer draw lengths.

Also a consideration - shorter bows need larger cams which directly relates to increased cam lean and associated issues.

And highly reflexed bows = lower brace height which, while giving increased speed, does keep the arrow on the string for a few milliseconds longer, which can lead to torque-related shooting errors. In addition, longer risers tend to be more stable in the vertical plane.

So, while “in theory” a long old-style deflexed bow would sound like it’s the most accurate choice, the modern shorter, target bows with straight or slightly reflexed risers tend to give the best balance between speed and stability.


----------



## Shogun1 (Jan 31, 2015)

Another factor of bow design that I noticed with a very short ATA bow.

At brace, the axles are almost even with limb pockets.

At full draw, the axles are below the limb pockets.

Impact: at full draw, the bow tends to “pull into line” and eliminate torque.

Applied: for a longer ATA bow, that requires a longer riser ... which results in more “mass weight.”

Too much mass weight = harder to handle


----------



## huteson2us2 (Jun 22, 2005)

I think DL is very important equation in the string angle. I have shot many compound bow since 1974. This means that I started off with 48" bows down to 32" bows and at 27" draw, I find my best length of A to A on a bow is 34 ti 35". 

I shot my 300 Vegas rounds with a 46" to 44" bow back in early 1990s, but I feel that I would have shot more Xs if a good 35" bow had existed at that time. An archer with a 29" draw would feel that a 40" bow would fit him better due to string angle and a 25" draw archers would feel better with a bow under 32".


----------



## Mahly (Dec 18, 2002)

I believe that there are several items to look at.
1) Stability. Putting weight away from your grip improves stability... or at least, slows you down.
With a long ATA bow. This is accomplished without affecting the balance of the bow. To match it with stabilizers, you would need a good bit of weight coming out of both sides, centered on the grip.
Of course, you could do the same to a long ATA bow and have even more stability.
2) Torque. As mentioned, less strong angle means less effect of grip torque.
3) Fit. Most people shoot bows today that are smaller than ideal, as bow companies continue to build most of their bows for hunters looking for a compact bow, and more speed. When I started shooting, target bows were normally 44”-48” ATA. I still shoot my best with something in the 40” range. It’s just easier to fit my form. (Note: at a 31.5” draw, mine is a touch longer than average).
4) Brace (not dependent on ATA so much). I don’t believe lock time plays a noticeable part when discussing brace height. What is more noticeable is the minimum distance between the string and rest (as the arrow leaves the string. The closer the string gets to the rest, the more important that your rest set up needs to be perfect. And it isn’t a 1:1 ratio. A 5” vs. 6” brace is MUCH bigger of a deal than 6” vs. 7”. 
If you are perfect, and always release exactly the same, it isn’t a big deal. If you are less consistent, this may have a more pronounced effect for you.


----------



## the.pabst (Nov 6, 2014)

Mahly said:


> I believe that there are several items to look at.
> 1) Stability. Putting weight away from your grip improves stability... or at least, slows you down.
> With a long ATA bow. This is accomplished without affecting the balance of the bow. To match it with stabilizers, you would need a good bit of weight coming out of both sides, centered on the grip.
> Of course, you could do the same to a long ATA bow and have even more stability.
> ...


Wow, very good explanation. Thanks!!!!


----------



## Padgett (Feb 5, 2010)

I have shot from 35 to 39 inch target bows and each of them I was able to get the draw length to where it fit me good. I have spent most of my last 10 years with a 37.5 inch bow. 

To me the biggest issue is draw length, it absolutely must be perfect with the perfect d-loop length. It is more important than holding weight and stabilizer length and weights on the end. 

Overall I have had at least 3 different target bows that I loved the feel and hold but the last bow I will shoot is my bowtech specialist, the one thing it does that the other bows from matthews and prime and pse don't do it hold the sight pin. I watch tons of good shooters turning their windage during competitions and I simply don't. My specialist will hold a sight pin for 2 to 3 months at a time without one windage click. To me that is worth something, it means that my bow will hit behind the pin if I do my job. 

There is nothing worse than making a smooth shot and the arrow hits 2 to 5 inches off line and you are left standing there wondering what in the hell is my arrow doing over there. With my specialist when I do my job it is behind the pin.


----------



## Padgett (Feb 5, 2010)

Be careful, one thing I have learned is a lot of the sponsored shooters want to use "This Bow Holds Better than any bow I have ever shot" I am calling bs on that. You set up the stabilizers with weight to balance it to your preference and total weight. One of your hands is touching your release and the other hand is touching a few inches of the grip so don't be trying to tell me that that bow holds amazing compared to anything else out there. As long as the holding weight and your draw length is the same it will hold the same as long as your stabs are set up and the total weight is the same.


----------



## *SWITCH (Nov 27, 2007)

Padgett said:


> Be careful, one thing I have learned is a lot of the sponsored shooters want to use "This Bow Holds Better than any bow I have ever shot" I am calling bs on that. You set up the stabilizers with weight to balance it to your preference and total weight. One of your hands is touching your release and the other hand is touching a few inches of the grip so don't be trying to tell me that that bow holds amazing compared to anything else out there. As long as the holding weight and your draw length is the same it will hold the same as long as your stabs are set up and the total weight is the same.


I get that, not sure I completely agree with it, but get what you are saying.

Also, i think the bows grip and the hand position can also play a part. Everything else being equal, if your main contact point with the bow is different (high/low or position etc) from one bow to another this could mean stability differences.


----------



## j_0_h_0 (Sep 10, 2016)

lots of good info people have given here


----------



## OCHO505 (May 27, 2010)

I think sometimes get to caught up on specs... I go off of feel and what feels best and that's that. I know all my spes but don't put yourself in a box that your not even sure it the best box for you. 

And I don't agree at all with Padgett saying a bow is a bow and holds good. My Bowtech Boss verses, my Reign 7, verses my Invasion all feel different and they are shoot differently. One is way longer, one is way shorter one is in the middle and so I set them up differently. Even if they had them same purpose I wouldn't set them up differently. One bows like 7 oz lighter than the other. 

I saw a video of Griv paper tunning a Hoyt for the new year similar to his last years bow. Well he took his exact stabs, sight etc of the old bow and shot through paper and big tail out of the shaft. He messed with it and messed with it and finally took the bars off. Tail was gone. Point is what works on one thing may and will not work on the other. Just like form. Some guys shoot better long DL, short DL and all over with weight, stab lengths and sights. That is why I go off feel. JMO


----------

