Need Help-----Question on Dry Heat Bending

[Glenn R.]

Hey Guys, I haven't been on the site for awhile, I took a board position with the United Bowhunters Of Illinois and seem to have lost all my free time. Anyway, I'm building a bow to donate to our banquet and need a question answered. First--a run down of the bow---it's a short brush bow, osage, 3-1/2" steamed reflex in the handle, sinew backed, 56" long, ridgid handle, narrow--mid limbs 1-1/4" with semi- pyramid taper down to 5/16 nocks. Right now its tillered at a brace of 6-1/2"--can leave in tillering stick for 3 hours--take off and limbs go back to reflex---am shooting for a finish weight of 50# at 27" draw. I posted a short osage bow-54" on here last year but this one is much nicer. I drew the 54" bow 29" without losing the string but its close. On this new bow I believe I'm safe on string angle not going past 90 degrees but am toying with putting a slight flare on the limbs tips---I should have done this before the sinew while I was steaming Oh well, thats hind sight.          So here's the question: 

With the sinew in place, can I use dry heat and put a slight flare---back 2" from tip---changing the string angle to keep string from pulling off limb,  without damaging the sinew to wood bond?   Thanks for any advice/prior experiences you can give,  Glenn.
 

 

[FlintWalker]

If the sinew goes out to the tip...no.  If it stops short or where you want to heat it...yes.  If you plan to heat it, I would wrap the are you don't want to heat with something to pratect it from getting hot.  If that hide glue gets hot enough it'll soften up and you'll loose the reflex you gained with the sinew.

[M-P]

I recently reworked a sinew backed osage that I originally made ~ 10 years ago.  It was one of the first two stave bows I built and my first ever sinewing job.   I never liked it though because of an uneven tiller and an ackward handle.   Anyway I  retillerd the bow and then heat treated the belly to bring the draw weight back up.   By being careful where i pointed the heat gun I got good results and even slightly reflexed the limbs.   So I feel that you probably could induce a mild  recurve.   If you did notice damage to the backing, you could always scrap the damaged sinew off and re-apply to that area.   Another option might be to skip the recurve and try building up enough sinew on the tip to create a small hook of just sinew.  Some of the California bows had similar all sinew recurves, just to prevent the string from slipping.  If that explaination is unclear I try to copy a diagram from a book for you.
Ron

[Glenn R.]

Thanks Ron, I do remember seeing pictures of a small hook to prevent string slippage if overdrawn. This is pretty close to what I had in mind--but had figured on heating the tips back to 2" so as not to put alot of stress on one small area. I'm still exercising the wood/ letting the belly compress---haven't had past brace yet, but when I do will make a decision based on string angle--I think the idea of a build up of sinew on the end sounds like a safer bet--just as long as I don't add much weight--I'm building this with the idea of sqeezing evert bit of energy/speed out of a short, straight limbed bow. Right now, tension on the string at brace is unreal, and have removed all the mass I dare from the outer limbs. I'm donating this bow to our banquet auction and the majority of the members wanted something offered in the 50# range--can't wait to see how fast it spits out a 500 grain arrow   I will get some pictures posted before it goes off to banquet.  Glenn 

[JackCrafty]

I assume you're using pin nocks?  If not, can you get away with making the nocks deeper?

I've tried heating and making corrections to sinewed bows before and hide glue holds up well if it is very dry.  I was able to make only slight corrections so I'm not sure you'll be able to recurve the tips without cooking the backing.  The backing might look OK afterward, but it might become brittle...I dunno.

On one of my bows, I just wrapped a small amount of sinew above the nock to keep the string from slipping off.  You don't need too much, especially of the bowstring is not waxed.

[Badger]

I have often thought about getting some kind of heat strip or wire like they use for defogging mirrors and try to wrap the affected area to be curved wit the hot wire, not sure if theat would work or not, has anyone ever tried this? Steve

[islandpiper]

Badger, Guitar sides are often bent using "heating blankets", silicone pads that bend and get really hot.  Check out some of the luthier supply places or google "silicone heating blankets"    piper