Cross-section help

[Academonicon]

Hey bowyers.  I need some advice again.  I'm working on an osage stave, and it's really pretty nice for the most part.  Very straight grain, minimal knots/pins, thick late-wood in the growth rings, etc.  A promising stave for sure.  However, it does have a problem I'm not sure how to deal with, since up to this point I've almost exclusively worked with boards.

The cross-section of the stave isn't symmetrical, which I assume is going to be a problem.  This is what's going on:


If I shape the belly so that it's symmetrical, then both limbs of the bow will be bending significantly to one side.  On the other hand, if I just continue working the belly down evenly, I'll wind up with different widths on either side of the limbs.  What should I do?

[Academonicon]

Oh, also: How wide should it be at the fades if it's going to end up being something like 40-45# @27"?

[mikekeswick]

Make it even on both sides at all costs!! What you are describing is called propellor twist but don't worry if you must you can straighten it with the aid of a solid vice, heatgun, an adjustable spanner and a bucket of water. However it isn't necessary to straighten it.

[Academonicon]

Thanks Mike.  It's actually not exactly propeller twist.  If I make the limbs even thickness on both sides (which makes sense to me), both limbs will be bending in the same direction.  Nevertheless, I think I can probably correct it using the same methods you mentioned.

[Del the cat]

Thanks Mike.  It's actually not exactly propeller twist.  If I make the limbs even thickness on both sides (which makes sense to me), both limbs will be bending in the same direction.  Nevertheless, I think I can probably correct it using the same methods you mentioned.

Err... if both limbs are slanted in the same direction then just rotate the bow in your hand by a few degrees!
If it changes up and down the limbs, make the belly follow the back, but check that it draws true.
The bottom is...
The only thing that matters is that they pull back straight.
My 'go to' bow is called "Twister" but it draws straight and true.
Del

[Academonicon]

I get what you're saying, Del.  The issue is that if I rotate the unstrung bow so that the limbs are straight, then the belly and back of the bow will be pointing off to one side.  Which might be fine, I don't know!  They might still pull straight back toward me, but I've never dealt with this issue before, so I'm concerned about it.

To clarify, this is what I'm talking about (forgive my poor graphics.  God, how I miss photoshop.):

[Del the cat]

Maybe this post will help ... it shows how you can kep an eye on it as it draws back.
http://bowyersdiary.blogspot.co.uk/2011/03/twisting-bow.html
This post shows what Twister looks like, yet with careful tillering it comes back straight...
http://bowyersdiary.blogspot.co.uk/2011/09/explain-more.html
(I wanted to do do a bow without heat correction as I'd done a lot of heat work on previous bows)
Here it is finished 
http://bowyersdiary.blogspot.co.uk/2011/09/finishing.html
What I'm saying is, it doesn't matter which way the belly and back 'aim' it's which way it flexes. So your picture on the right isn't a problem as long as it pulls back straight down (along the line of the red arrow).. you'd think it would want to pull back on a line at right angles to the belly  but it ain't necessarilly so.
I've done a pic to show what I mean... not quite sure how it's achieved... maybe 'A' is just a tad deeper than 'B' ... that's part of the fun of making bows.
If you don't fancy trying it, you can steam or heat it to remove the twist.
Del

[Academonicon]

Okay, thanks Del, that's good to know.  I'll be careful to watch the way it bends as I tiller it.  The end of one of the limbs does have a little more twist than I'd like and I may try to heat it out, but overall it's comforting to know the bend won't necessarily follow the right-angle to the belly.  Counter-intuitive, but comforting.