Duo flexed bow. Thinking it through.

[Prarie Bowyer]

Hey guys!

I want to make a Duoflexed recurve similar to the ones Mark St. Louis makes.  He was kind enough to point out that there is a splice seam in the handle of those.  Clever fellow.  I never thought of that. 

So I'm looking at the idea and wondering how to get that angle.  in the grip section with a "Z" splice.  My inclination is to figure out the angle I want and make an angled sled for the band saw.  That way the seams fit togeather and then all I need to do is grind off the parts that stick up.

The hitch here is that I'm thinking of doing it as a 3-Lam.  One piece of bamboo backing.  My first inclination was to use multiple glue steps but I'm cautious to over dry the wood with several trips through the oven.  I believe one of my most dramatic explosions was from overdrying.

So I first thought to build the limbs seperately with the recurves minus the backin (Urac).  Then cut the Z splices and glue up with the riser in TB3.  Let all that dry and then Urac the bamboo backing over the cleaned up Z splice.

The handle is deflexed at the splice so that creates some clamping issues also.  I think bike tire tubes will fix that issue nicely but i need to leave gaps for air or the TB3 won't set up.

I doubt that dong it all at once will be possible and get clean glue lines.

OR.  I could rehydrate the wood some I guess.  I normaly wrap everything in shrink wrap for Urac glue ups.  So If I do the first stage.. each limb laminations and the recurves then cook that.  unwrap it, clean up the glue squeze out and make the Z splice and clean up the protrusions (it's happening at an angle remember) then I can glue that with TB3 with the riser, no oven.  Clean that up when dry, urac on the backing and cook it wrapped in shrink wrap.   So there is time to regain lost moisture, and it's mostly locked in anyway.  I could spritz it with H2O after the final cook and let it sit for a day or 3.  That might work.

What do you guys think?

I was going to go with the max I thought I could get in a central bend at glue up and deal with that.  But when I saw the seam Mark St. Louis did I was blown away with ideas and possibilities.

[mikekeswick]

Glue up your limbs minus backing , cut splice , glue backing on - Simple!

[Prarie Bowyer]

That is kinda what I outlined but I'm concerned about over drying the wood.  However I have a Job interview in the city in two days so I'll stop and grab some hickory at the lumber store.  For a DEEP bending design I have more faith in Hickory.  If it works out then I'll try it in Tri-Lam Ipe and bamboo.

[LivingElemental]

Anyway you can post a picture or link of a similar bow? Im not sure what this is supposed to look like.

[DarkSoul]

Titebond3 WILL set up when wrapped entirely with bike tubes. There is no need to leave spaces between the wraps for the moisture to escape through. Ithink the moisture from the glue is drawn into the wood, but I'm not sure. There could be a chemical process involved as well. When you wrap a glue-up entirely, it may take longer for the bow to fully dry. Leave it clamped/wrapped for at least 24 hours. Then remove the wrappings. You can start working the bow now, but some patches of oozed out glue may still be tacky (which can get onto your tools). I would advice to wait at least a few more hours after unwrapping, so the spilled glue has dried as well. Then you can work the bow, but you must still consider the wood to be moist. So leave it to dry for another 24 hours to get the excess moisture out.

I don't understand why you are concerned about over drying the wood. If the put wood in a heat box to let the epoxy cure, then you are sure the wood will dry out as well. So...? What's the matter? Just leave it outside the heat box for a few days and it will reach EMC again. No need to submerge the bow in water or spritz it with H2O. As long as you don't stress wood that is too high or too low in moisture content, there's nothing to worry about.

I'd personally rely on boo backed ipé for more radical designs. If you see this picture of a boo backed ipé recurve, you have to admit it can take far more than you'd thought. Hickory is more prone to taking set and high humidity than boo and ipé. I'm not saying hickory will not cope with that design, but I just think a bamboo backing is capable of dealing with more stress.

[Prarie Bowyer]

Anyway you can post a picture or link of a similar bow? Im not sure what this is supposed to look like.

http://www.primitivearcher.com/smf/index.php/topic,5717.0.html
http://www.ironwoodbowyer.com/
2nd from the bottom

http://www.ironwoodbowyer.com/Selfbows.html
pic # 6 from the top.