My question is how does the overall length affect the draw weight of the bow at a certain draw length.

I have a couple bows that take Hoyt formula limbs, one is a 17” riser and the other is a 24” riser. If I put the same limbs on them and pull to the same length, would I be getting the same poundage? Even though one is longer than the other?

I would imagine that the shorter riser would cause the limbs to start stacking quicker, but does that mean the longer limbs will be less than the stated poundage?

Shorter risers than the standard where limbs are measured (normally 25") the weight will be more than marked on the limb. There are exceptions where some are weighed on shorter risers like the Tradtech. It works like it always has with proprietary limbs like Bear or Wing back in the day. You make the riser shorter you're pulling a bit more weight at draw.

Grant, I have no specific data for Hoyt formula limbs, but the general rule of thumb for ILF limbs is for a given draw length, they will gain about one pound of draw weight for each inch shorter than the rated riser length. Limbs on a shorter riser have to bend more to give the same draw length, hence the higher draw weight.

I would guess limbs mounted on the 17" riser would have about a 7 pound higher draw weight versus when they are on the 24" riser. As with all 'rules of thumb', there are a number of variables that could impact what you actually see. If the risers are from different manufacturers or different models from the same company, the limb pad angles may be different. That difference can have a significant impact on draw weight.

Most Olympic/competition ILF limbs are measured on a 25 inch riser. As George mentioned, there are exceptions these days with ILF having made its way into the hunting market and the prevalence of shorter ILF risers. For limbs easured on a 25 inch riser, the general rule is draw weight will increase by 1 pound for every inch the riser decreases in length. A set of limbs that pull 40 pounds on a 25 inch riser should be around 46 pounds on a 19 inch riser, give or take a pound.

Riser length has little or nothing to do with stacking in the situation that you describe. Shorter risers will cause the limbs to have increased draw weight at a given draw length (IF the geometry of the different lengths of risers is comparable) simply because the shorter riser makes more limb bend.

The ROUGH calculation is that there is a change of draw weight of about 1lb. per inch of riser length. As the riser gets longer, the draw weight decreases at a given draw length because less limb is bending. As the riser gets shorter the draw weight increases 1lb. per inch of riser due to more limb bending.

That is NOT stack. Although some folks categorize it that way simply because it gets to a draw weight that they aren't comfortable with. When that happens they immediately jump to "these limbs stack". Not always the case.

True "stack" has direct relationship with overall bow length. Overall length is what determines string angle, and string angle has a direct impact on actual "stack".

for ILF in general and likely FORMULA as well, me being ignorant of FORMULA things.....it's still a bow. Generally there is a rough rule of thumb saying limbs taken off a 24-25 inch riser will scale roughly 1# higher per inch of shorter riser length....or in your 2 risers AROUND 7 pounds higher.

wow ah types purty slow.

thanks for the information, some of the limbs I have are specifically designed (have the name of the bow and logo printed on them) for the 17” riser. I would assume that means it is going to be the listed weight with a 17” riser? If I understand correctly this would that mean putting the same limbs on a 24”riser would result in the actual weight being about 6-7 # lighter?

" I would assume that means it is going to be the listed weight with a 17” riser?".......(if the 17" riser has the same geometry as the riser they are rated on. If not there will be a slight change. Less draw weight if there is more deflex in the limb pads, more draw weight if there is less deflex in the limb pads. But the difference should not be huge.)

"If I understand correctly this would that mean putting the same limbs on a 24”riser would result in the actual weight being about 6-7 # lighter?"......(Most likely. BUT the only way to REALLY know is weight them on the riser in question.)

I have a set of Hoyt Formula limbs mounted on my Buffalo riser. They are marked 38 and scale 47. Do the math, but off the top of my head, that is a pound and a half change per inch of riser difference. I would like to say that can used as a rule of thumb but it can't. I have seen a range from 1.1-1.5 pounds per inch.

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