Heat treating boo backed bow

[Kidder]

I’m starting on what will eventually be a boo backed hickory bow and am looking for input on heat treating the belly. I’ve searched online and have yet to see where anyone has done a heat treated boo backed bow of any kind, but I can’t imagine this would be a first. I use EA 40 for the glue up. Questions related to timing of the heat treat and issues it presents.
1) I could wait until it’s glued up and tillered. What is the likelihood of damaging the epoxy if done this way?
2) I could heat treat the belly on a form like one would do for a non-laminated bow and then glue it up after. For the heat treat to be effective I imagine I’d have to be tillered very well on both belly and back pre glue up and the belly would have to be very light otherwise it’d be an 80 lb bow or I’d scrape away all the tempered wood. If done this way should I put in any Perry reflex or just the heated in reflex? If so how much would be appropriate given that the belly will be tempered and at risk of a tension break?
Any other thoughts would be greatly appreciated.

[superdav95]

I would go with option 2 imho.   Hickory will be great in compression if thoroughly heat treated thru with out scorching the belly.  You can have a form prepared to toast your hickory first to the reflex you want.  If you have made a boo backed hickory before of this style you can use those thicknesses as a reference for this build so that you don’t have to scrape away too much belly wood.  The only glue I’m aware of that might possibly allow any heat treat after glue up is urac 185 or replacement unibond 800.  Even better would be system three g2 epoxy.  West systems too.  The g2 is rated up to 170 degrees if your doing a mild heat treatment if insistent on heat treating after glue up.  I think you’d be better to do a solid heat treatment of hickory lam separately and then laminate with 2:1 ratio with smooth on ea 40.  It gives better performance at that ratio if then placed into hot box to fully cure.  I’ve done ambient temps for overnight cure on ea40 at that ratio with good results on wood to wood glue up.  My boo to wood glue ups also were fine at non hotbox glue ups.   I guess time will tell for the difference. Hope this help in your decision.  Reach out if any more information needed.  I know Allen case on here is a glue expert too so he could chime in on this for ya.  I’ve heard that it’s been done after glue up with certain glues but it seems to me that to get the most benefits of proper heat treatment of hickory you’ll need to go well above the 170 mark in my opinion.  250-300 more like it.  FYI.   

[Del the cat]

If you want to go with option 1, this post from my blog may help. (The heat treating bit is down the bottom of the post)
https://bowyersdiary.blogspot.com/2015/02/two-steps-forward-one-step-back.html
Del

[Eric Krewson]

I have heat treated several bamboo backed bows that turned out sluggish because I used softer osage in them. The heat treat turned them into fine bows.  I used Urac  glue in one and Unibond in the other that I can remember, these glues can stand a lot of heat so I had no problems.

[Gordon]

Heat treating limbs that have already been glued up is asking for trouble. Best avoid potential delamination and heat treat the belly before you do the glue up.

[Eric Garza]

I would heat treat on a form before glue up. I made a hickory backed heat treated hickory bow similar to what you are proposing, and it turned out well. I tillered the belly as if I were making a bow that was ~15 pounds lighter than my goal, then heat treated both limbs while it was clamped flat to a 2x4. I then glued the bow up as normal, and tillered from there. It didn't require too much wood removal, so the belly still had some visible temper.

I have since set this bow aside though and will probably never hunt with it. I glued in way too much reflex and the bow is hard to string. It is also very unstable, and sometimes spontaneously unstrings itself by twisting around. It hasn't broken though.

[Kidder]

I opted to heat treat it on a reflex form with 2 inches of reflex. Kept about 1.5 inches of reflex. Plan to glue in another inch or so of Perry reflex. It was tillered a little lighter than normal but still probably on the heavy side where I will lose a bit of the heat treat. I also had a little bit of wrap around scorching but I doubt this will be an issue as it should all theoretically be under compression with the boo carrying the tension load. We shall see…

[superdav95]

Looks good brother.  I think you’ll be pleased with the performance you get. 

[Kidder]

Thanks Dave. So one thing I didn’t account for was the cupping that would occur from the heat treat. Once I flattened the boo I realized that the back of the hickory belly was no longer flat. So had to spend some time on the wheel edge of my belt sander - couldn’t use the flat top because of the reflex. But I got it acceptably flat again. It had taken just over 2 inches of heated in reflex. I glued in another 2 inches of Perry reflex. So it’s sitting on the form with just over 4 inches of reflex. I’ll know how much it keeps when I unwrap it later today but I’d guess it keeps almost all of it given that half is heated in.

[Kidder]

Came out of glue up with over 3” of reflex. So kept about an inch of Perry reflex.

[Will B]

That is looking great Kidder!  Should be a very durable bow with that combination. Good luck the rest of the way. Looking forward to seeing the finished bow.

[superdav95]

I bet this will be one of your fastest bows.  You’ll be impressed with results.  My fastest bows often have some heat treatment on hickory or hhb.  I’m excited to see your results on this bow. 

[Kidder]

So I thought I’d share my follow up experiences for the good of the group. I made a few mistakes tillering on the long string and when I braced it I had far too stiff of outers and ended up almost immediately fretting the bow. Worked those hinges away but by the time it was done I had very very tiny frets for around half of each limb, maybe more. There are a few places without and a few with more but overall there are tons of tiny ones spread out. I haven’t shot it yet but interestingly it has about 2 inches of reflex still. I will shoot it in and tweak the tiller but it’ll go into the “meh” bow pile. Most of the heat treat is gone. I suspect part of the problem was design - I was only 1.3” wide from fades to the last 12 inches. I’d have liked to have gone wider but that was all the width I had to start and wider also means thicker when dealing with boo so it was a trade off. I should have also gone thinner before the heat treat on the belly so as to maintain more at completion. But not sure that would have solved the issue as it still fretted in places with some toasting left on. Not saying Hickory Boo bows are impossible but they aren’t easy and I haven’t succeeded yet. As my kids would say, I definitely had the “cheese touch” on this one - everything I touch turned to cheese!

[superdav95]

Ah man sorry to hear that it didn’t meet your expectations.  I had high hopes for this one myself.  I’m surprised at that many frets.  The neutral plane too far one way I suspect.  Who knows maybe just a bad section of hickory?   I would think that the boo backed hardened heat treated hickory would be a winner for sure.  I wonder if too much of hardened cells were removed like you say.  Hard to know exactly at this point.  I’d be interested in looking into this further with you when I get back.  I gotta think something went wrong there.  I reach out when I get home.   Cheers. 

[Stickhead]

My only experience with boo-backed hickory was a disappointment, too.  The boo was too thick, and I had to remove practically all of the hickory to get it tillered.  Ended up with a lot of set.