Primitive Archer
Main Discussion Area => Bows => Topic started by: WillS on April 17, 2013, 04:16:01 pm
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Quickie question for anybody who knows - if you know the draw weight of a bow at a certain draw length, is there a formula / calculation to work out what the weight will be at a different given length? For example, if a bow is say 50# at 18", is it possible to work out what the draw weight will be at 20", 22" and so on?
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I use 2.5# per inch and it will get you withing a few pounds.
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Cheers Pearl.
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Will if you scale your bow at 18" and it reads 42#, you can basically expect it to remain close to 2.33# per inch as you pull farther until stacking occurs past 90 degree's.
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I find my bows are more 3-5# per inch. Some of my warbows above 90# have been as high as 7# per inch.
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How much does the brace height affect this? I'm asking as I'm currently tillering a yew longbow, and it's at a low (2 inch) brace height so basically just a v. tight long string at this stage and it's dead on 50#@18". Does the formula still remain the same, or does a higher brace height change things? If we average out Pearl and Adb's answers and say about 3#/inch, does that mean that at 28" I should be expecting 80#, or will that go up/down once I'm at full brace?
Normally I don't consider this stuff, I just tiller out to my goal draw weight and so on, but it's too dark outside to use the tiller so I'm in "think" mode instead!
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Your math sounds right to me Will. Brace height doesnt affect draw weight.
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I don't know for sure, cuz I've only ever measured this at full brace. I wouldn't think it would change much, if at all.
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The limbs have to bend the same distance whether it starts at a 3" brace or a 6" brace, therefore the draw weight doesnt increase with a higher brace. The string will be tighter at a full brace, but the end draw weight will remain.
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Great, cheers for the replies guys!