Limb Lam Thickness -vs- Draw Weight

[huntwithastick]

Can anyone give me a good estimate on how much increase/decrease in draw weight can be expected by increasing/decreasing the thickness of the limb?

Thanks.

[Apex Predator]

It greatly depends on design.  The more curvy designs require less lam stack.  The same can be said for shorter designs.  On my 66-68" straight and slight R/D longbows, it usually is 2.5# per .010 lam thickness.

[huntwithastick]

I guess my question was for one specific design - say D/R design!  Thanks for quick input on the straight and R/D designs!

[Apex Predator]

Do you have photo of your form.  Riser length?  A lot of variables!  Go to Binghams or Three Rivers Archery websites.  They each have a limb thickness chart for the designs they offer.

[Swissbow]

I got an excel table from Jason for a moderate R/D-design. It has worked very good so far. You can get it in the download section on my website.
 
 www.swissbow.com

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Andy

[Jason Scott]

Are you copying an existing bow? I have a cube root formula that I can send that will get very close to a new weight for any style bow you want to copy. All you have to do is precisely measure the bow you want to copy, enter its stack, weight and your target weight and it will give you the new stack height. You have to rebuild to exact except for the new stack.

[Jason Scott]

Using the formula you can deduce how much stack changes differ in weight.

[swamp ghost]

Can you post the cube root formula?

[Jason Scott]

I have it in Excel. I will have to email it to you.

[Jason Scott]

I don't know how to attach a file using the TG email feature. Your email is not listed. Respond to my email and I will have yours.

[Trick]

Jason,

I would appreciate it if you could send me the formula also.

Thank you,
Patrick

[huntwithastick]

I started out w/the Bingham pronounced design.  I like short risers though, so shortened my riser to 14".  The three times I've tried to order from Binghams and tell them my dimensions I've come in significantly off target on weight.

[Jason Scott]

I'm guessing you came in lighter than you wanted. Maybe you could just order a stack that is 15 pounds heavier than your target weight according to their normal design and just not tell them about your shorter riser. After your layup with the 14" riser the 15 extra pounds will go away with the 4" loss in riser length. Not sure what their standard riser length is though, assume its 18". Basically just order 3 to 4 pounds heavier for every inch shorter your riser is than theirs.

[huntwithastick]

Whoooohooo! Eureka! I had a set of partially finished limbs that I got around to finishing and they came in at 55lbs.  So, now I have my baseline and can adjust from there!  Thanks for all the input guys - I do appreciate it.