black birch

[bowman_79]

I finally have a nice dried and strait stave of black birch. I took it down to rough dimensions today. Its a pretty tough wood to work with a sg of .67. For some reason, I cant find my notes for finding the optimal poundage for a 2" wide black (sweet) birch selfbow. Its going to be 66 1/2" ntn. Can anyone give me a little advice? thanks.

[Pat B]

You ought to be able to get a 45# to 50# overbuilt bow with sweet birch. It is stronger in compression and not so strong in tention, I believe.    I've made a few but they were sluggish.   Pat

[bowman_79]

That light for such a heavy wood? I was hoping for a different answer than that.    :(   huh

[Pat B]

Try a piece and see what results you can get. It was a few years ago when I built one and since then I found other woods I like better. Maybe if backed it would work out better. We have a lot of sweet birch here. The twigs taste good if that helps any.    Pat

[bowman_79]

The grain is really straight, so I'll keep it unbacked. I guess trapping might be an option here. I use this website for all my wood specs...   http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr83.pdf

I see compression on there, but what do I use for the tension properties? Sweet birch is on page 27.

The winter hasnt been hard enough to start chewing on the twigs yet.

[Pat B]

Even though the grain is straight adding a backing will add tention strength that I believe birch lacks. Both of us are lucky to have plenty of good bow woods where we live. I have played with most of them and have become partial to some and others I don't mess with. Birch is one I haven't messed with for a while. I do have a few staves in my work shop.
  Sweet Birch is where oil of Wintergreen comes from. Primitives used the twigs for tooth brushes. It has a nice cooling taste to it.   Pat

[Pat B]

John, Trapping might be a good idea for birch but trap it backwards...wide back narrow belly.   Pat