glass poundage

[bigbob2]

I know I asked this question some time back but I cant find it. I know wood core rough rule of thumb is about 3thou per lb, but for the life of me cant remember what the difference in glass thickness is roughly, ie if using same size wood stack but say .030 glass compared to .040 glass?

[bamboo]

its total stack thickness thats measured-
less glass+more wood=same poundage
more glass + less wood=same poundage[for a given thickness]
hope that makes sense!

[bigbob2]

Thanks for your reply Bamboo. Some where I read that one could roughly say that when calculating total stacks to arrive at draw weight, it  was roughly .003 per lams per lb, but there was a figure for glass as well, maybe it was .001 per lb. I can come in at the required weights when using .040 glass but am going to use .030 for this next light draw bow and am trying to calculate the stack allowing for the lighter glass.

[bamboo]

i would do the calculations for stack[to hit the poundage]--then make up the difference with lamination--add .020 to the core wood thickness[making up for less glass]--and that would be the starting point--sometimes you have to tweek the calcs on the second bow
also keep detailed notes

[johnny girardi]

Bow poundage vary from bow to bow with the diff length there built.Glass will ad about 1 pound per 1 thousandth.Thats about 10# pounds for .010 of inch glass. Wood is .003 to.004 = 1#. Your fornula for wood core is not those figures.These figures are to add or subtract poundage.

[bigbob2]

Bamboo,Adding 20# to the stack for the lighter glass seems on the money. I did a bow with .040 glass which I wanted to be the same draw weight as one I did with .50 glass.I wanted to see the difference the differing glass would make using the same draw weight. I added .021 to the stack and after cleaning up was right on the money.Johnny Giradi Appreciate your input. I do realise the formula is a different matter to adding and subtracting for different glass, but thaks for your valued comments.Thanks guys.