Approximately how much weight will I gain...

[ssrhythm]

Not sure Brad.  I’ve never sinewed over a cracked back, and I don’t want to waste the time and sinew for it to just break anyway.  The bow was too long to begin with…for a sinew backed recurve, it is way, way too long.  I’m aiming for 60-62 inches, so I think I’ll be gaining enough weight to just eliminate the compromised back.

[bradsmith2010]

how do you know the crack is only one growth ring

[bradsmith2010]

show me a pic of crack,, so I am not just guessing

[joachimM]

Assuming you can consider the bow limb as a lever and the handle as the fulcrum, halving the bow in length should double the draw weight, Archimedes already provided a geometrical proof of this principle thousands of years ago.
So from that it's easy to calculate from the initial length and draw weight, and the intended draw weight the length required to get to that draw weight.
Or you can reverse it (how much do I gain from shortening X amount?)

I could send a spreadsheet with the details, you just have to copy the three values (length, current draw weight, intended draw weight) and it will output the desired bow length.
There are a few additional underlying assumptions, but in general this works pretty well.

For example, if your current bow is 65" and draws 45#, and you want to get to 50#, the new length should be 61.7", assuming the bow can take the extra strain.

[bradsmith2010]

or you could tie nocks at 61 and test before you cut,,

[ssrhythm]

Great ideas and points to try and consider.  Bow is a scosh shy of 67” as is.  I’ll try to post a pic tomorrow. I can’t be sure it’s only in the top growth ring, but I think it is.  I worried about pulling it enough yo get good glue under it, but superstition CA would probably get in there.  If it’s into the next ring, I’ll probably shorten it more and make It my son’s new bow and just start another for Mo.  We are finally getting some decent temps to get out and do something with it starting tomorrow.  Thanks for all the input.

[bradsmith2010]

what caused the crack, how big is it etc,,

[Aksel]

I just piked a 72" bow to 70". Gained 3#. It took a slight reflex out of it. It´s now straight, so it was a slight trade off but I think it was worth it.

[Pat B]

You can always add reflex back into the bow with heat.

[Aksel]

Pat,  I guess I could but it´s a reflexed kink on only one limb on a Mollegabet bow I´m working on, right on the fade where the limb transitions from bending to stiff outer limb, so I´m fine with it looking less wonky now.