Warp on back

[Bob Schmidt]

I am building an OM back and sides are walnut. The back has a slight warp on each side of center where the figure changes. It does clamp up OK on the rim but I am wondering if it might have a longer term issue. Should I think about an additional brace across the back or think about not using it?
I hope you can see it in the attached photo's. It is onboth sides of center.

[Bill McCall]

Weil, walnut is pretty stable, but I would think that since it’s already moving from your flat blank it will want to continue to move even after glue up. What, when and if it may break is a matter of conjecture.

Just my $.02.

[ProfChris]

That wouldn't bother me, I'd use it. Much of the warp will be glued to the tail block anyway.

[Tavy]

I think that should be OK, once it's braced and glued to the rim it should be fine, especially if you're inducing a bit of an arch anyway. If you're hoping for a dead flat back, you may be less lucky as I would expect some of the distortion to still show up.

I would brace it as intended and then clamp it to the rim and see how it looks?

[Bob Schmidt]

Thanks for the replies.
It is already X braced with a 15' radius. I dry clamped it to the rim last night and it does set in flat along the rim under the spool clamps. Since the X brace allows for a bit more movement along the back I thought an additional ladder type brace might be needed, but I am not sure how that would affect the sound of the instrument.
The warp follows the figure, which converges where the X brace crosses.