Questions about heat treating

[Centrvm Medivm]

Hey guys, I've been reading primitive archer for several years and finally decided I needed to be a part of this. A couple of months ago I built a really nice bamboo backed maple laminate flat bow for a good buddy of mine who recently moved to TN for a job. Its 66'' long, 1 3/4" wide at mid limb and roughly 40lbs or so @28". I'm afraid I over stressed the limbs when I was tillering it, and I did have minor delamination near the limb tip that I had to cut out.

After I shot it in, I noticed that I had a solid 3" of string follow across both limbs and the draw weight dropped off to around 35lb @28".  I've read Mr. St. Louis' work in TBB vol. 4 and I think that heat treating might be a good way to get the draw weight up to where it should be. The guy I'm making this for wants to hunt feral pigs down south, and I don't feel comfortable sending him up against an animal like that with a bow that light (I'd be more comfortable with a 50lber personally). Also I think the set problem might be the humidity here in WI this time of year, either way, I think I could make it shoot harder. 

My main worry here is that if I heat treat the bow, the limbs might delaminate again. I glued her up with titebond 3, and I'm not sure how it reacts to heat. Does anybody have any experience with this? I'll post some pictures once I get them downloaded.

Thanks!   

[Wiley]

Heat will release TBIII. Really handy for most things but you want to do the heat treating of anything bonded with it before you do the glue up in bow making.

[Centrvm Medivm]

Then I'm really glad I didn't just go ahead and do that! Would've been a shame to wreck that bow.
Thanks Wiley

[Centrvm Medivm]

Well, here's the pictures just to make good on saying that I'd post them earlier. I haven't had another bowyer look at any of my work and am very interested to hear if anyone has something I can improve on tillering wise etc.

[Centrvm Medivm]

I guess my picture files are to large to upload all at once... whoops, here it is unstrung.

[mikekeswick]

To access the tiller properly it's essential to have a picture of the bows width profile and then a picture of it drawn by hand.

[DarkSoul]

Welcome!
Heat treating a laminated bow is a big no-no. Never do that, please! You could heat treat the lams prior to the glue up, but not once they are glued together. The intense heat will loosen a glue like titebond, and at least weaken a 'heat resistant' epoxy.

Bamboo backed maple is not the best combination ever. The bamboo is a bit too powerful for maple. Maple also doesn't really need to be backed (as long as the grain is straight), since it is excellent in tension itself. There is a multitude of much better belly woods for bamboo.
I can't really judge the tiller properly so far, but it appears to be bending too much in the mid limbs and not enough near the handle. The set doesn't look like 3" in that unbraced pic...looks less.
Try uploading picture to www.tinypic.com and post them here. Then there is no restriction in file size.

There's no legitimate way to raise the draw weight of that bow from 35# to 50#. You need to start a new one. Did we mention that making bows is addictive? 

[blackhawk]

Even tho maple isn't the best belly for boo your width and dimensions is still decent enough to counter set and  string follow,and if done right should still work ok and not take as much as yours....its pretty apparent to me that you over stressed it during tillering,AND the tiller is not so good(to be honest)...and if you've been shooting it like that then it just makes it all the worse...I see a hinge in the upper limb..and two real subtle hinges in your lower limb with a flat spot in between...your unbraced profile is telling the same story and can be seen....to me your biggest issue and problem is tillering..and to solve that ya just need more practice is all...there's no convenient and practical way to up the weight on that IMHO....time to make another one to be honest...learn how to tiller better..and its not just the final outcome at full draw but everything ya do before full draw is achieved....I'd recommend trying simple self bows at first to learn how to tiller,then go to the more complex bows..

[Marc St Louis]

There is a way of using dry-heat on a laminate without it coming apart but I don't know if it's worth the effort, this is something I have done before but just on short sections.   I just don't know if the heat necessary for heat-treating would damage the glue though, that I haven't done before.  The way to do it involves a bit of prep-work before using the heat and it does leave marks on the wood.  What you have to do is clamp the limbs together so they don't delaminate, naturally you can't use clamps for this.  What I did was to hold the laminations together by using strong cotton string, do not use a synthetic string, and wrapping the limbs tightly leaving 1/2" ~ 3/4" between the string, the string has to be strong and it has to be wrapped quite tight.  Now someone in the past has claimed to have spoken with the makers of TB and apparently the glue becomes stronger when it is heated to a high temperature but.....

[Eric Krewson]

I have heated urac glued BBOs three different times. Not the deep, long heating like Marc but plenty hot enough to turn the limbs(yellow osage) very dark brown. Urac can stand the heat and none have delaminated. All were sluggish shooters with a lot of string follow, after heating they retained reflex and really zipped an arrow.

[Marc St Louis]

If the Osage turned dark brown then that wood was heat-treated.  Osage seems to transfer heat better than a white-wood so the glue no doubt got very hot