brace height question ?

[jacobsladder]

im getting some conflicting info..

Does higher brace height cause arrow to act stiff or weak..

and the same question for lower brace height...

ive always assumed the lower brace height would be more of a power stroke so would tend to make an arrow act weaker... is this true?

[vermonster13]

If the arrow is right on the edge spine wise it can. You gain 4% for every inch of power stroke. SO a 6" BH compared to an 8" on the same bow will give you 8% more which could mean you need a different spine arrow.

[jacobsladder]

dave ..would there be a difference between 2 " of draw length and  2" of brace height as far as power stroke is concerned? would it be considered the same thing?

[xia_emperor]

Dave. "If the arrow is right on the edge spine wise it can." what? cause arrow to act stiff or weak?

Lower brace means you would need a stiffer arrow?

 

[Molson]

Originally posted by xia_emperor:
Dave. "If the arrow is right on the edge spine wise it can." what? cause arrow to act stiff or weak?

Lower brace means you would need a stiffer arrow?

   

No.  If you had an arrow that was too stiff, you could possibly lower the brace enough to get it to fly.  Likewise, if your arrow was too weak, you could possible raise the brace enough to get it to fly.  In either case, the arrow is incorrect for the bow and brace hgt has nothing to do with that.

[Tom A]

Raising brace will cause a stiff arrow to act weaker. If your arrow is too weak you would lower brace. Too stiff you would raise brace.

It works backwards than you think it would because a lower brace gives you more speed. But changing the brace changes the whole dynamics of how and where the arrow bends around the bow.

[Tom A]

Its pretty complicated. This link has some pictures and info.

 http://goarchers.org.uk/mechanics/bh.htm

[vermonster13]

Lower brace height needs a stiffer arrow and longer needs a weaker comparatively. If your arrows are that close you should consider new arrows though. Yes two inches less brace height is very close to gaining two inches in draw length because the arrow is on the string that much longer so more energy is transferred. The bow will also be less forgiving of form errors at a lower brace height.

[Tom A]

Vermonster I disagree. Lower brace requires a weaker arrow. Higher brace requires a stiffer arrow.

[Kip]

Now you all got me seeing it clear as mud.Kip

[Tom A]

Its all detailed in that link I posted above and I have seen the results in my own bareshafting.  If a arrow is planing left a small bit(stiff). You can usually get it to come back to center by raising your brace a few twists. If a arrow is planing right a little (weak) you can lower brace and get it to come left.

[pseman]

One of you is definately correct. I just don't know which one.  :confused:

[tjjsidekick]

I think Tom a is correct. I higher brace height places more pre-stress on the limbs so that at full draw your holding more poundage that will be translated to the arrow. This increased poundage at full draw is what will cause the arrow to act "weaker" Conversly, a lower brace height has less pre-stress on the limbs so that at the same relative draw length, there is less force being held and translated to the arrow resulting in a "stiffer" acting arrow. Arrow speed is a function of how long the arrow is on the string (the longer power stroke), but the relationship between the power stroke and the resulting force translated to the arrow is an inverse one.

[whitebuffalo]

Great link Tom A..

[Rick_H]

I'm happy to jump right in!! Tom A, your link states that lower brace height produces more stored energy which I take to mean able to shoot a stiffer arrow.

[Tom A]

Yes but in the "Dynamic spine" area it also states that raising the brace increases the amount the arrow bends and that is the dominant factor.

[Blackhawk]

Vt..13,

Are you saying this:   :confused:  

If I have a bow with an 8" brace height with my 27" draw, then I can lower my brace to 6" and this would be the same as if I had a 29" draw?

Not doubting you, I just wanted to make sure.    

Interesting thread and thought provoking.

[vermonster13]

It would produce similar energy to that of the same bow at 8" Brace drawn to 29" (if the bows had the same draw weight at 27" and 29")if that bow can shoot with a 6" Brace.

A higher Brace height actually causes you to hold less weight at peak according to Tom's web page link.

Actually it decreases the amount of time the arrow has to bend in since it has less string time. How it increases the bend while giving less energy to the arrow is rather confusing. Olympic Archery Style site working with some pretty long bows also.

[vermonster13]

Like I said earlier though, if your arrows are that close to the edge, you'd be better served with a different arrow set-up. If you short draw or over draw just a little at the moment of truth you're not going to get very good arrow flight.

This is also another reason a lot of bows test different in the reports than in real world shooting. Brace is set at the lowest spot for testing to get the fastest speeds and noise and such aren't a consideration. A lot of the barn burner bows have 6-7" recommended brace heights and in many cases guys just aren't going to shoot them set that low.

[pseman]

Not sure if the decrease in brace height would produce nearly as much speed increase as equal increase in draw length. I believe it was SlowBowinMo that had done some testing on this subject recently and found only minimal increase in speed with lower BH as opposed to marked increase in fps with each inch increase in draw length. The reason was that the force exerted on the arrow at the bottom of the draw cycle(lower BH) is not nearly that which is imparted on the arrow at the end of the draw cycle(inc draw length).

Hope this makes sense. It made sense when he posted the numbers. Hopefully I explained it correctly.