Why Char?

[Almostpighunter]

I figure this question has probably already been answered, but my search results turned up zilch so here it is again. I have seen some people charring the belly of their bows and I am wondering what benefit this provides. I like using the torch for cosmetic reasons but is there a benefit?

[Shaun]

try searching for "toasting" a more common term for tempering the belly material to add compression strength. Some woods respond well to this method - seems like hickory is often mentioned and maybe osage.

[Jude]

Marc first published his findings on heat treating elm and since that time several others have successfully used it with other woods, hickory being the most common, I think.  I used to hear that osage did not benefit from it, but recently I've seen posts stating that it does add performance.  The process involves toasting the belly slowly, without charring, so that the heat travels deeply into the wood. If you go to quickly, only the surface wood will be hardened, and you want the hardened wood to extend into the neutral plane.  The next part of the process is to let the bow rehydrate several days before stressing the limbs again, as a too dry bow can fail at full draw.  I have found this to not be a factor with hickory, since it likes to be much dryer than other woods.  I've had my hickory bows out shooting the same day they were treated with no bad results, but frankly, my biggest challenge in NY is getting hickory dry enough to perform well.  It takes abot 1-1&1/2 hours to do a complete bow, and the belly wood will turn medium to dark brown, as you slowly work a heat gun down each limb individually.  Most bowyers will also take the opportunity to introduce some reflex and remove prop twist at the same time.  The best way to do this is by clamping the limbs to a caul, either all at once, or gradually clamping as you work from grip to tip; the choice will depend on the type of wood, and the amount of reflex you are trying to introduce.  It is possible to heat treat by stringing the bow backwards on a tillering tree, but it is more difficult , since as you heat a portion of one limb, it will take on the reflex and the string tension will disappear.  With that method, you have to continually monitor the curvature you're introducing and adjust the string tension as you work down the limb.  With that method, I would commonly treat the inner limbs on both sides first, then work through the mid-limbs of both, then work to the outer limbs.  It worked well, but took longer, because you need to rewarm the area you left off at, when you switch from limb to limb.  Hope this helps to answer some of your questions.

Jude

[blackhawk]

A torch will not work well for heat treating. Its too hot and just burns the surface wood,and doesn't penetrate deeply enough. Get a heat gun if you wish to temper.

[PEARL DRUMS]

I have read that burning the wood weakens it. I have no proof because I have always tempered/toasted and never burnt any to know.

[Almostpighunter]

Great stuff guys! Thanks!

[Pat B]

Marc St Louis popularized this method to increase conpression strength in his high performance elm(and other whitewoods) recurves. He does a deep heat treatment using a heat gun held in a holder with the nozzle about 2" to 3" from the wood. He keeps it there for a while so the outside of the belly wood becomes charcoal almost.
  I have heat treated a few bows in the last few years. I don't do as deep of a char but I do scorch the wood pretty good. I generally do this as I'm adding reflex to the bow. Tempering(heat treating) works on whitewoods and woods that are less strong in compression. I have used it on osage with good results too.
  You only want to temper the belly and never the back. Charing the back can be fatal to a wood bow.

[crooketarrow]

  Although I never do it anymore you must use a heat gun put it on low as it go's. And go slow the slower the better.
 But here's want I found out through testing 6 bows 3 HICKORYS 1 ELM and 2 OSAGE. The three HICKORY 2 HICKORYS picked up, 3 and the other 4 fps useing a chono. the elm picked up 2 fps. The OSAGE picked up 1 and 2.
 W

[crooketarrow]

  Weather it helped with the life of the bow. Theres no way of telling since every stave is different. And you can't take the tempering back.
 I also tested a hickory bow where I used a torch. Where I did it as slow as the torch would let me. I chared it mostly the whole way. This is a no-no you damage wood cells. my bow shot 7 fps slower after I tempered it with the torch and went from 1/2 of string follow to 1 1/4.
  But with a heat gun do it slowly it dose help a little. Not really enough for me to do it. Acouple fps dosn't make a bow. The time is much better spent working on your tillering.

  Shoot your bow after you finish it all but the findle finish ofcorse. Then shoot it again after you temper it. See if it helped your bow. Ofcourse there's no going back after you temper it. But I've never seen any negive results useing a heat gun on low.  At least you'll know if it helped or not.

[Pat B]

If you are going to heat treat a bow be sure to let it rehydrate before you stress it. This time of year I'd give it a week in the bathroom where the humidity is the highest.