Brace Height and Arrow Speed

[bradsmith2010]

DC,,no worries ... thanks for all the positive input,, it s does seem reasonable that the longer power stroke of the low brace would have a postivie effect on arrow speed,,,

[Stick Bender]

 I read that same book Brad and always thought that to be true but I really think it depends on the bow design I recently made a highly reflexed FHLB that ended up at 63lb @30 1/2 I couldnt get the brace down below 8 1/2"  with out making limb contact so I was determined to bring it down to 7 1/4 "  so I narrowed the limbs & traped both the back and belly got the draw weight down to 57 lb @ 7 1/4 " with the limbs bending more ,I didnt like the way it was shooting even though it wasnt making limb contact and I returned to the 8 1/2 " brace the bow chronyed at the same numbers ether height but shot much better at the higher brace, I cant really exsplain it other then when moved to the higher brace it a loud more of the highly reflexed limb to work negating the extra length, I dont think the lower brace height applies to all bows but just my 2 cents !

[DC]

This is kind of like tuning my model sailboats. You know from the physics of sailing that doing something is a positive thing. What you don't know is how much will it change and will the change be negated be something else that the change will do. It can get very frustrating.

[bradsmith2010]

Stickbender,, good point,, I think you are right,, and just because someone got a certain result with a bow,, does not mean it is correct for all bows,, for sure,, and DC,, thats a good thought as well,,
maybe with a straight limb self bow it is more applicable,,, I just enjoy getting a bow to shoot smooth with good,, or perfect to my eye,, arrow flight,, and enjoy the rest of the technical stuff, ,but dont let it get me too frustrated,,

[Danzn Bar]

Very good posts here guys.
Good information.
What this site is all about
You Guys sure can put it in words better than i.
Thanks
DBar

[Stick Bender]

I think there is always trade offs with a bow, change one area and it changes in other places it's kind of a balancing act of sorts but a whole hardly agree how the bow shoots regardless what the chrony says is most important , I think that's what makes this bow making fun ,regardless what you read you really don't know tell you make the bow and test it !

[Danzn Bar]

If it feels good when shot.....its a gooder 
DBar

[bassman]

Hatfield did those tests with Damon Howatt bows that had a lot of early tension built in to them.Most were recurve bows. I don,t think he pulled that number out of the sky.As has been said it may be different with self bows or backed bows or siyah bows etc.Those bows were a very good production bow, maybe the best, and still going strong.Wished he could reply to defend his statement.Might surprise a lot of us.

[kbear]

A very interesting topic. Forgive my novice interjection..... but what effect does a higher brace height have on the longevity of a selfbow? Would a higher brace height not place greater stress on the bow during extended periods whilst strung, and result in increased cast-robbing set? A common theme among bowyers I have noticed is that during the tiller process, set becomes more a problem when the bow is first strung at brace height due to the change in the angle of force the string is now applying. From that view point, would a bow being tillered at a lower brace height, and then strung for use at a lower brace height, presumably not be subject to the same force/angular "abuse".

 

[bushboy]

Maybe nonsense,but could a longer power stroke affect penetration?same speed but more kenetic energy?

[Badger]

A very interesting topic. Forgive my novice interjection..... but what effect does a higher brace high have on the longevity of a selfbow? Would a higher brace height not place greater stress on the bow during extended periods whilst strung, and result in increased cast-robbing set? A common theme among bowyers I have noticed is that during the tiller process, set becomes more a problem when the bow is first strung at brace height due to the change in the angle of force the string is now applying. From that view point, would a bow being tillered at a lower brace height, and then strung for use at a lower brace height, presumably not be subject to the same force/angular "abuse".

 

If you did loose 1 1/2" power stroke on the bottom end it wouldn't have much effect n arrow speed, less than 1# stored energy in the last inch and 1/2.

[DC]

A very interesting topic. Forgive my novice interjection..... but what effect does a higher brace high have on the longevity of a selfbow? Would a higher brace height not place greater stress on the bow during extended periods whilst strung, and result in increased cast-robbing set? A common theme among bowyers I have noticed is that during the tiller process, set becomes more a problem when the bow is first strung at brace height due to the change in the angle of force the string is now applying. From that view point, would a bow being tillered at a lower brace height, and then strung for use at a lower brace height, presumably not be subject to the same force/angular "abuse".

 

You got me thinking. An interesting thing is that the lower the brace height the more tension there is on the string. A 40# bow can have 45# of string tension at brace. This tension actually drops when you draw the bow. Now if the damage done to a braced bow is caused by the string compressing the wood then a lower brace height would cause more compression and more damage. But at the same time a higher brace height bends the bow more. We're back to numbers again, which scenario causes more damage or is it so slight that it doesn't matter. I think i'll go with that

[Badger]

The lower brace is still less stress. It just has less leverage to bend the bow so is pushing it together more in a straight line.

[Bayou Ben]

DC, have you measured string tension on your bows? 
I never did but have heard from glass builders that string tension is close to double draw weight in some designs.  I thought your bows would have higher string tension. 

[DC]

Not on any of the RD's. I have on some of my earlier selfbows. They were just a few pounds over draw weight, nothing like double. maybe I'll try an RD. Once you get the scale in the string it's really weird to draw the bow and watch the scale go down.