Bamboo backed Osage selfbow

[muzzlebrake]

I decided to re-work and re-shape the limbs of my Osage selfbow in order to take off a bit of draw weight. After reshaping the limbs to a narrower profile, more of a pyramid design, I re-strung it and checked the tiller and all was good so I shot it a few times and what a difference. Almost no hand shock and seemed to be casting just as fast as before only the draw weight was about 10lbs lighter. I'm tickled at this point so I decided to clamp in down and use a heat gun to remove some of the set before I re-finished it with Tung oil.
Fast forward to after the re-finish and I go out to shoot it again and it seems to have re-gained most of the original draw weight. WTH? After shooting it about 50 times I unstrung it and the set has not come back as much so at least the heat has worked so far. Now I'm wondering if I should take the limbs down a little more to get me back down to 40-42lb. Would the heat have caused the thing to increase poundage?

[Bisch]

Arvin, where are you?

Bisch

[AJMag]

It depends on how much heat you put to it. Once a bow takes set... it's there for good. By that point you're only changing the looks of the bow and not the performance. How does the tiller look after changing the design of the bow? How thick is the bow at the fades? Just remember that the set is already in the bow and isn't leaving, you're only changing the look of it at this point. The wood cells on the belly have already been crushed to the previous weight, so lowering it won't help performance because it wont have the tension-compression ratio that it had at first.

[muzzlebrake]

I removed wood on the belly from the fades to about 9" from the tips. Overall I removed up to 1/8" from the sides to get a more straight taper and a little more from the tip back about 9" where I had stopped on the belly. I probably only removed about 1/16" or less from the belly. So far the set I removed has only come back about half way. I did get the wood pretty hot but not enough to scorch it, just hot enough that you couldn't touch it for long.
The bow was originally 55lbs @ 28" and my goal was 40-42 @ 27". I think it has come back to around 46-48 after the heat treatment.
The tiller has remained the same as near as I can tell.
Top limb is a tad weaker as before

[AJMag]

Well seeing the design on the back, I guess you're limited to working the belly a little more. I would just be really careful about how much more you take. It won't take much at all to get down a couple more pounds. The more I think about it, I can't fully explain why it would gain weight. Personally, I wouldn't have put heat to it with a backing on it in case it started to weaken the glue, but I guess you would have seen any issues by now. I've never worked with bamboo backing, only hickory and no backing, so I couldn't tell you if boo gets any tougher with heat, which could add a little tension. Looks good anyways. Good luck with it

[muzzlebrake]

That is the belly. Tiller is +1/4" on top limb and set is now reduced to 1-1/2" where it used to be 2-1/2". Gonna shoot it some more today and see if it will lighten up some. The best part so far is I have removed about 90% of the hand shock by re-shaping the limbs.

[muzzlebrake]

Amount of Set after heat treating.
Shot it about 100 times now it it's holding it's own.

[Selfbowman]

Steve you don't wat to get the bow very hot it could delaminate. If it is staying together don't heat it any more. It gained weight for two reasons. One when you took the set out you increased the draw on the the bow. Two heat will make the wood on the belly not compress like before. Bowyers Bible 4 speaks of heat tempering. Shoot it some more and then retiller to desired weight. And yes you can remove set with heat but not suggested on laminated wood bows. Been there done that.

[muzzlebrake]

Thanks Arvin. This is one of those El Cheapo bow kits I glued up and finished. I will keep and eye on it for any delamination.
If it blows up then I haven't lost very much.
It seems to like about 6.5" brace hgt and shoots pretty smooth.

[live2hunt65]

Nice bow