[j-san]

While tinkering with a recurve this weekend, I came to the realization that there is a relationship between preload and brace height (feel free to correct me if I'm wrong). The set up I was tinkering with is a 58" AMO recurve consisting of a Dryad 15" Epic riser with medium 45# TradTech Black Max Carbon Extremes.

With max preload (limb bolts 1/2 turn out from snug), I find I am able to shoot a lower brace height than if I had the limb bolts max out (4 turns from snug). I also noticed the brace height increased slightly when turning the bolts out (not taking string off), but there was increased noise on the shot, similar to what I usually get when brace is too low.

On the extremes of either side, I found the bow would behave well with a brace of 6 5/8" with max preload, but would need a brace of 7 1/2" with min preload. I determined the brace heights by way of the sound on the shot and simply added/subtracted twists until the shot no longer sounded harsh. I also noted that the further out I turned the limb bolts, the greater the "twang" I would get from the limbs regardless of brace height. Just for fun, I turned the bolts in as far as I could (just lightly snug) and found the bow to be remarkably quiet. I suppose this may be the reason why bolt-downs are desirable. At any rate, just thought I'd post up my findings and see if others here concur or disagree.

 

[Grantmac]

For fun place a piece of masking tape alongside the string groove. Mark where the string leaves the limb when at correct BH and full preload. Then do the same at correct BH and low preload.
I'm betting the results are VERY close and would also be consistent across riser lengths.

I believe Sid brought up the concept of marking limbs with a BH range at the string lift point rather than publishing it as a number.

-Grant

 

[j-san]

Interesting. I'll have to give that a try. I suppose a couple dabs of nail polish would make for a more permanent brace height marker once the correct range has been established.