Wood/bamboo Backing

[DC]

I've done Bamboo backing and noticed how stiff the bow gets after glue up. Does other wood like Maple or Hickory behave much the same? I'm doing a Black Locust with Maple backing and I'm wondering how thin I can make the BL before glue up. Looking for about 40#. I want to glue some reflex in and the thinner the BL the easier that's going to be. The maple is about .140" thick.

[Bob Barnes]

Every time you back with wood or bamboo you will add several pounds to the draw weight.  The more reflex you add when gluing the backing will also add weight.

[DC]

What I'm wondering is if bamboo and wood add about the same?

[JWMALONE]

DC, I've only done a few of each. They seem to be about the same to start. The hickory backed  ive done seemed  to drop weight faster when tillering. The bamboo also seemed to hold more reflex. Ive only done a few of each and I'm no expert, but that's been my observation so far. This was done with ipe belly wood so the only variable was the backing.

[Springbuck]

  They are both pretty close, DC.  I'm convinced that bamboo is more tension strong than hickory, but they are both much stronger than the belly will be for most woods.

Part of the stiffness just comes from thickness.  Adding a 1/8" thick backing to a belly slat is proportionally a lot of stiffness, and Perry reflex makes it more so.

[DC]

Good I will press on. Thanks

[Springbuck]

   How thick is your locust, and how good quality? Fifteen years ago or so, I bought a huge (2" thick, 42" long, maybe 17" wide, flat sawn, monster slab) very dense BL board, that cost me over a hundred bucks.  I made like 14 pairs of 3/8" thick, quarter sawn belly lams out of it, and made maybe 8 successful bows from those. 

A lot of guys were saying bamboo would "overpower" locust, but most became bamboo backed bows.  I generally always trap the limbs but leave BL at least 1-3/4" wide, or even the full 2" .  I did notice that the QS bellies seemed to take a LITTLE set early on, then stop.  Either way, at hunting draw weights, the thinnest part of the finished  limb usually has something like the 1/8" backing and the belly is down under 1/4".  But that's the THINNEST, and I do usually use a power lam.

[DC]

It's iffy quality BL. A 2- 2 1/2" sapling. I decrowned and removed all the really fine ringed sapwood. What's left looks good though. I'm going to back it with Hard Maple. It's just under 1 1/2" wide and about 1/2" thick. I'm planning to trap the back. That would be my next question, how much to trap it?

[Springbuck]

  I dunno exactly, sorry.  Really sharp angles always look and feel weird to me.  I play it by ear during tillering.   Tips often end up rounded or something else anyway. 

  I use trapping more to reduce limb weight without affecting tiller or draw weight, than to balance tension and compression as some guys purport.  That probably has some benefit, but "a bow is a bow until its back breaks", and I want my backing not to be imperiled.   

 BL has that reputation for being stiff, but not as elastic as some other heavy woods.  You have all the width you are going to get, so I mentioned trapping.  I don't think it'll hurt if the maple is backing-worthy.

Maybe just take the corners of the backing down at 45 degrees and leave the BL squared up?  Doesn't sound TOO iffy, though.  Saplings often have either wide rings or very tough wood in their first years, and if that's turned to heartwood and looks ok otherwise.......