Trad Gang
Main Boards => The Bowyer's Bench => Topic started by: Forwardhandle on December 14, 2017, 05:40:00 PM
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Hi Fellas I have been studying about making glass bows I have made self type bows for a few years now but working my way to make one with glass I usaly don't like to ask questions unless I can't find the answer my self some where but one thing that's been puzzling me is on a average self bow the belly tapper is on average about 1/16 every 5 1/2-6 in. But on glass bows you see much flatter tapper 0.001,0.002,0.003 Ect ,could sombody explain that to me , could it be different front profile Ect ? I have googled the heck out of it but no answer ?
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I have measured hundreds of factory bows, and .003 taper seems to be the magic number.
James
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I would think it has to do with the addition of the glass making things stiffer.
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Also for narrower bows you need more thickness taper, as you have less side taper. :)
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It has to do with the strength of the wood or composite in the case of a glass bow. Fiberglass adds a considerable amount of bending strength to the overall limb composite. Taking 0.003" off the thickness of a glass bow may equate to 1 lb less draw weight. You might have to take 0.010" off of a self bow to lose 1 lb of draw weight. It's the same reason that most self bows start out at almost twice the thickness of a fiberglass bow, they aren't as strong.
A hypothetical example of 3 bows with similar width profiles may have the following taper rate to produce the same bend profile:
Elm Self bow- 0.010"/inch
Bamboo backed Ipe- 0.007"/inch
Glass bow- 0.003"/inch
And as mentioned, the width taper affects it too.
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Bmorv that was a excelent exsplanation thank you and the 0.010 is where I start tapper wise with a self bows your exsplanation makes prrfect sense to me.
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It is linked to the width profile. Parallel width limbs need more thickness taper. Pyramid width tapered limbs require less.
There is no 'magic' number for all designs.