How do changes in brace height effect performance

[hcbowhunter]

I started shooting my new recurve this evening. As I started increasing the brace height the vibration lessened and the bow got noticeable quieter. It also appeared that I was loosing arrow speed as I increased brace height. I always thought increasing brace height would have the opposite effect, at least up to a certain point.

Has anyone ever experienced this or have any advise?

[RickBarbee]

Brace height is pretty much primarily a tuning approach for achieving stability of the bow, quietness of the bow, and fine tuning arrow dynamic spine assuming you are fairly close in spine already.

Lowering the brace height changes the angle of the arrow effectively to the outside, thus compensating some for a weak spine.

Raising the brace height changes the angle of the arrow effectively to the inside, thus compensating some for a stiff spine.

Contrary to old popular beliefs, raising & lowering the brace height does not increase, or decrease the power stroke of the arrow enough to significantly change the speed of the arrow. It might change it a tiny bit, but that's all.

There is an optimal point of brace height for every bow. Going above, or below that point will always yield diminishing returns, but generally undetectable (except for in tune/arrow flight) as long as a reasonable window of brace is maintained.

Rick

[Cwag]

Longer brace height means there is a smaller draw curve. In other words there is less distance of string movement for force to be applied to the arrow.
As to why it is quieter and has less vibration, the proper brace height of a bow does a lot of things:
1) when the brace height matches the dynamic spine of the arrow the arrow will use the proper archers paradox. ( flex around the bow) too much flex will put excess vibration on an arrow/bow when the inertia of the tip battles the KE of the string causing the arrow to flex too much around the riser. Too stiff an arrow/ to high of a brace height can make the arrow bounce off the shelf. (not enough flex)
2) string slap:
When the brace height is too low on a bow it causes the string to contact more of the limb. This causes two things. The increased vibration of the increased surface area of the string contacting the limb. Also when the brace height is lower there is slightly more play in the string. Thins means that after the arrow has left the string, the string has more mobility to move in abstract directions caused by minor differences in tiller/ grain fluctuations etc.

[Cwag]

Oh Rick beat me to it.

[Selfbowman]

I am sure Rick will disagree but selfbows perform better with a low brace ht. 61/4 - 61/2 . At least mine do. Arvin

[RickBarbee]

I am sure Rick will disagree but selfbows perform better with a low brace ht. 61/4 - 61/2 . At least mine do. Arvin

Nope, I don't disagree at all.

The thing is - you can have two otherwise identical bows, yet they perform their best at different brace heights.

Selfbows generally will wind up with their highest preload at lower brace heights, which mean their optimal brace height is at that lower point.

Rick

[hcbowhunter]

Thanks for the replies.

I'm a up to 8.5 inches on brace height and the bow continues to get quieter. Do I keep increasing bh? Recommended is 7-8. What happens when you surpass the sweet spot? Recoil? Bow noise?

[hcbowhunter]

Bow is a 45 lb Hoyt buffalo

[Limbwalker]

Brace height is pretty much primarily a tuning approach for achieving stability of the bow, quietness of the bow, and fine tuning arrow dynamic spine assuming you are fairly close in spine already.

Lowering the brace height changes the angle of the arrow effectively to the outside, thus compensating some for a weak spine.

Raising the brace height changes the angle of the arrow effectively to the inside, thus compensating some for a stiff spine.

Contrary to old popular beliefs, raising & lowering the brace height does not increase, or decrease the power stroke of the arrow enough to significantly change the speed of the arrow. It might change it a tiny bit, but that's all.

There is an optimal point of brace height for every bow. Going above, or below that point will always yield diminishing returns, but generally undetectable (except for in tune/arrow flight) as long as a reasonable window of brace is maintained.

Rick

Rick just saved me a bunch of typing. Listen to the man.

The idea that brace height is going to change performance really needs to be just thrown out.