When to add recurve? Before, during, or after tillering?

[txdm]

I recently made a nice hickory board bow all the way through to the point I would toast the belly and put a finish on it, then decided to try to add recurve to the tips.

I made a mold with about 11" diameter bend of 45°. I first tried using a heat gun over a period of about 30 minutes with mineral oil, and got it bending, but it cracked open.

I dont know if it was because I'd already tillered the limb (it had 1.5" of set), or if the radius was too tight, or if I didnt heat it properly (the crack was about 1/8" in from the surface). I might have used too much heat and not enough time?

I decided to experiment and boiled the other limb for about 2 hrs, then put it on the mold. It bent much easier and only a small crack lifted on the surface of the belly. It was a failure, but much less than the dry heat was.

So I have made myself a new mold that has a much larger 45° curve to it that should span the last 10" of the limb. I feel like this curve would work fine even with my dry heating method, but I'd still like to improve it if possible.

Would it be better for me to attempt to add the recurve earlier on in the process, before there is stress added to the ends on the limbs? Also, if I plan to dry the roughed out bow in a box with a space heater before tillering, would it be good to put recurve in it before drying?

[gfugal]

I started a topic about bending a while ago with responses that might help. http://www.primitivearcher.com/smf/index.php/topic,59205.msg821282.html#msg821282. I Think you should be able to get a bend much steeper than a 11-inch radius unless it’s some un-bendable wood I’m unaware of. I was able to get kiln dried oak to bend a 5 ½ inch radius. Maybe you’re measuring diameter not radius, if that’s the case then it’s the same as what I did. I would do it before you tiller and everything because it’s good to tiller for the recurve, otherwise it might break since recurves stress the limb more. I bent the red oak when it was a little over ½” thick. People were saying that it probably should have been a little narrower, but it should be fine for a wood that bends easily and not kiln dried red oak. The thinner it is the easier it will bend but you risk losing poundage. Its possible that the internal part of the wood didn’t heat up enough. You really got to be patient with dry heat at a lower setting. I liked the boiling method. It sounds like you tried that though? Was it submerged completely? A 11 inch radius would mean you would need a very very tall pot so it’s possible the reason it broke is because parts of the wood weren’t heated further down the limb. Do you have a picture where it broke and the form you have?   

[Del the cat]

I'd say it's easier once the bow is part tillered. Makes the bending easier and also makes the early tillering easier (less likely to flip the bow or end up under weight)
Del

[txdm]

Thanks Greg, yes in all instances, I was meaning Diameter, not radius.

So my first failed attempt wold have been a 5.5" radius, and the new mold I made is probably a 11" radius. From your pics, it looks like I'd be better off adding the recurve earlier during the tillering process, and not after the bow is finished.

My plan is to:

• cut out the profile,
• Thin the limbs down to close to my previous bows thickness,
• boil & bend recurve,
• then dry it in the box,
• heat treat the recurved part
• Add a handle block,
• finish the tillering,
• heat treat the rest

[gfugal]

Sadly that bow ended up braking due to a crack forming while bracing it for the first time. Del makes a good point, maybe it would have lived if I tillered to brace first before adding the recurves. But it's just a matter of preference and accounting for those variables. I wouldn’t wait till the very end like you did the first time though.

[DC]

The thinner it is the easier it bends. The first rule of bending stuff

[txdm]

Del makes a good point, maybe it would have lived if I tillered to brace first before adding the recurves.

The thinner it is the easier it bends. The first rule of bending stuff

Based on the previous bow, I should be able take the outer half of the limbs down to 1/2" thick before bending the recurves.

[DC]

I only try to put big hooks into perfect wood and even then I fail sometimes. I think you have to develop a strain gauge in your arm so you know when to stop. You can also kerf it or cut it real thin and glue on an underlay. All this was learned by failing so take it with a grain of salt.

[upstatenybowyer]

I'd say it's easier once the bow is part tillered. Makes the bending easier and also makes the early tillering easier (less likely to flip the bow or end up under weight)
Del

+1

[txdm]

Well I cut out a stave today and got it in good initial shape, but I noticed a tiny knot on the belly in the area just near the end of where the recurve would be. I'm going to put some full-length reflex into this one instead, and try doing recurve on a later one.

[bubby]

I like to get the atave tillered to 20" , that way you don't get too many suprizes