effect of changing brace height?

[Jim Keller]

What effect does changing brace height have on tuning? I saw a byron Ferguson video and he was tuning his arrow flight by changing brace height but didn't give a good explanation on what raising and lowering does . Can anybody fill me in?

[X2]

Raising the brace height will make the arrows act weaker, and lowering the brace height will make the arrows act stiffer.  It can be used for minor tuning, but I prefer to find the best brace height for each bow arrow combination.  (least vibration), and then bare shaft tune.  That is what works best for me.

[Friends call me Pac]

A weak shaft can be tuned stiffer  by increasing brace height and a stiff shaft can be weakened by decreasing the brace height.  This is fine tuning to me after getting the best arrow combo that I can come up with.  It has to be really close before changing brace height factors in for me.

By tuning this way it is possible to get better arrow flight but the sweet spot of the brace height may be affected causing more noise.

As an exaple I shoot 195 gr field points and 195gr magnus 1 broadheads.  They both weigh the same but if I have the string set up for my broadheads to hit dead center in my 3D vitals the field points will shoot slightly weak and impact in the right hand side of the kill zone.

To get the field points to hit dead center I have to put two twists in the string and that will put my field tips dead center in the vitals.

[Kevin Winkler]

Originally posted by Friends call me Pac:
A weak shaft can be tuned stiffer  by increasing brace height and a stiff shaft can be weakened by decreasing the brace height.  This is fine tuning to me after getting the best arrow combo that I can come up with.  It has to be really close before changing brace height factors in for me.

By tuning this way it is possible to get better arrow flight but the sweet spot of the brace height may be affected causing more noise.

As an exaple I shoot 195 gr field points and 195gr magnus 1 broadheads.  They both weigh the same but if I have the string set up for my broadheads to hit dead center in my 3D vitals the field points will shoot slightly weak and impact in the right hand side of the kill zone.

To get the field points to hit dead center I have to put two twists in the string and that will put my field tips dead center in the vitals.

Duh! ............ Now that's and idea that I never thought of. Thanks, PAC

[Shooty1]

Heh--
Only three posts and you get to see the great brace height debate exemplified.

I'll go ahead and throw mine in:
Raising brace height weakens the arrow, and lowering the brace stiffens the arrow. The simple explanation is that yes, the lower brace height imparts more velocity to the arrow, but the higher brace height bends the arrow around the riser more easily.

Byron will tell you the opposite, as will the 50% of shooters who believe that to be the case.

[rraming]

For once everyone got it right - let us celebrate!

[BD]

Raising the BH stiffens the arrow, lowering it weakens the arrow. Pac is right on with this.

[Jim Keller]

Thanks guys.Man I learn so much on here. This site shortens the learning curve a lot.

[jojotater]

Why does lowering the BH weaken the arrow?

[rraming]

OK here is the real answer - If you reduce the brace height (causing the arrows to increase speed) it will require a weaker spined arrow and vice-versa. Shooty1 answered it correctly - kind of like moving the plunger in and out (makes it weaker the farther it has to go around bow) If you don't believe me try it for yourself. Take your tuned bare shaft and raise your brace height by 1/2"  - shoots weak - longbow shooters will notice it more than center shot recurves - it is what it is. And I have only been shooting traditioal for 4 years - man I'm a quick study!
JOJOTATER - it doesn't
Good job Shooty1 (Dan)

[Brian Krebs]

OK we have two different opinions. I started a thread a while ago asking why Byron Fergusons brace height is so high. I got no satisfaction out of the answers at all.

 Point of fact - Byron is a trick shooter; he shoots better than most of us here; and look at the brace height of his bows. When he puts on an arrow the fletch comes no where near the back of the bow; the string hits about three inches from the inside of his elbow; he hits his hat with the string every time he draws back ----
 If two twists make a bow shoot better; then a newer string still stretching could throw off your shooting really bad.
 And using a specific brace height might mean nothing at all - it may come down to tuning your bow by adjusting your brace height until the arrow shoots perfectly.
 If we came to that conclusion; seems like we could toss out half the tuning threads on record.

 WHY is it that Byron has a longer brace height; and can out shoot everyone?

 If two twists make it perfect; what would three do; and what would ten twists do: compared to 12?

       :confused:

[bigcountry]

I disagree with some.  Raising BH will make your bow gain poundage which in some cases will weaken an arrow (to a point) because now, you have lost power stroke.  Its a give and take balance.  At some point raising BH stiffens an arrow.  

Think about it, your at full draw, holding effectively 60lbs, what would happen if you shortened the string at that point .5"?  Your making your limbs bend more and raise poundage.  That inpulse right when you let go of the string is greater that point.  But your stroke is less.

[Spike]

Raising the brace shortens the power stroke and gives less energy to the arrow, therefore it acts like a stiffer arrow. Lowering the brace increases the power stroke and provides more energy making the arrow act like a weaker arrow. Those of you familiar with a draw force curve will understand a low brace will allow more energy to be stored in the bow, a high brace will allow less. The area under the curve is the energy stored. Less energy stored in the bow less energy provided to the arrow. Less flex as the arrow is shot makes it act like a stiffer spine.

[Spike]

Your bow will only start higher on the curve not gain poundage across the curve, however the slightly lower starting poundage times the 1/2 inch lost in power stroke is energy lost. A 50#@28 bow will weigh 50# @ 28 wither its braced 7" or 8".

[BD]

Well stated spike

[bigcountry]

Originally posted by Spike:
Your bow will only start higher on the curve not gain poundage across the curve, however the slightly lower starting poundage times the 1/2 inch lost in power stroke is energy lost. A 50#@28 bow will weigh 50# @ 28 wither its braced 7" or 8".

Totally false and totally impossible.  Go out to your bow shop raise the BH to 10". Yes your limbs can handle it.  Wiegh it at 28".  Lower it to 3" BH and see what happens.  If your at full draw, and you take 1" of string length off, your limbs are going to bend more, your wieght will increase.

Read TBB vol 1 on energy curve and preload.  Starting out with higher preload will have more energy than lower preload. This is of course if the power stroke is the same which is not.    

Before you reply, go out and do the test on a bow scale.  What your saying is impossible in the physics.

Every selfbow I have built so far has said different.

[bigcountry]

Originally posted by Spike:
Your bow will only start higher on the curve not gain poundage across the curve, however the slightly lower starting poundage times the 1/2 inch lost in power stroke is energy lost. A 50#@28 bow will weigh 50# @ 28 wither its braced 7" or 8".

Ok, so those fimiluar with the intregation of area under an energy curve clearly knows starting out higher preload will increase area.

[Friends call me Pac]

"If two twists make it perfect; what would three do; and what would ten twists do: compared to 12?"

Since the two twists was from me I'll try to answer that.  If 2 twists gets me in the center of the vitals 3 twists would start to move my impact to the left.  kind of like clicks on a rifle scope.  

Does it work for everyone I don't know.  But it works for me.  

I started trad last July and thanks to tradgang there has been much experimenting on my part.  I think I have tinkered with just about every way I can think of with my bow.

[Shooty1]

All this brace height conflict eventually ends up in the middle east, you know.

[Brian Krebs]

Shooty1 - LOL

 I Wonder if a bow is efficient at lets say 6 " more than 6 1/2 - and then again at 9 but not 9 1/2.

 B-E-C-A-U-S-E   ole Byron is shooting a brace height that is really high; and well...he is shooting really well to perfect.

 Before our swords are so sharp we start accidentally cutting each other; there is the apples to oranges factor. A reflex deflex shooter may experience a different reaction to BH than a 'D' longbow shooter and ditto on the recurve shooter.

 Without those factors included- everyone could be right: with a different answer.

 Will it harm a bow to increase the BH to find out the answers ????

    :confused: