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Looking for guidance on ILF stack

PostPosted: Sat Jan 30, 2016 8:34 am
by Marcb
I'm looking to make some ILF limbs for the riser I made last spring. I'm hoping to hit 45 lbs on the fingers at my long draw (about 32 1/4) Commercial limbs I add about 8lbs to the stated weight on my Oly setup. So I'm guessing about 37/38 lbs at 28".

The loose layup plan at this time is 0.043 ULS Fiberglass on the back, followed by a walnut veneer (I have to cut this so I can setup the thickness as I want), then bamboo core material, followed by Carbon purchased from Big Jim's Bow Company.

I'd like a bit of guidance on the overall stack height needed to hit this number. I understand that each limb design varies in draw weight, but I'd like to at least get in the neighborhood so to speak. I'd rather not make a 16lbs or 70 lbs limb to start with.

Also if anyone has a limb design to share that makes a known draw weight I'd be inclined to use it. I'm going to copy a commercial design I like otherwise.

These need to be "long" ilf limbs. With my long draw and the 19" riser I can't go any shorter without stack and finger pinch issues.

Re: Looking for guidance on ILF stack

PostPosted: Sun Jan 31, 2016 8:52 am
by Robertfishes
I have an ILF recurve form and a 37# @ 28" ILF long limb on a 19" riser would have a 0.242 stack.. The black limbs are ILF shorts, the other picture 15" VPA riser and long limbs. There is no carbon in my limbs, I use action boo and gordons fiberglass.. Image Image

Re: Looking for guidance on ILF stack

PostPosted: Sun Jan 31, 2016 8:59 am
by Marcb
Thanks, I spent some time looking at Binghams chart of draw weights and tried to extrapolate but figured someone here would have good info.

Re: Looking for guidance on ILF stack

PostPosted: Tue Mar 22, 2016 12:50 pm
by jwillis
I think Robert is probably close. It depends on your taper rate of course, whatever that is for an ILF limb. My "C" limb on my 64" takedown with a 21" riser is probably close to an ILF limb. On a 21" riser it makes a 64" bow and on a 19" riser it makes a 62" bow...both with a 18 degree limb angle. On the 64" bow my chart shows .238 for 35#@28 and .244 for 40#@28. On a 19" riser it will be a little heavier. This is a veneer bow with boo cores, 003 total taper, and 020 veneers on back and belly. I'm also not sure what the carbon layer will do, but being inside it will likely just be a stiff racing stripe. Maybe this will help. Jim