Double Bass Carving back plate question

[ctregan]

As I was carving away on the back plate arching, I noticed the flat side (non carved side) was starting to curl up, in a potato chip like manner.

Is this from large amounts of stock being removed from only one side?
Should I remove some stock from the inside now to balance things out?

Would it be better to carve the back 6-10 ml heavy, let it sit for a few weeks, then finish the carving after the wood has relaxed to its new shape?

Another explanation for the wood movment; maybe the wood is too new for instrument building.

 

[ctregan]

Here is a picture of the back.

 

[Matthew Tucker]

What's happening is that one side is drying out faster than the other. As you carve, you're exposing a new wood surface that has a different moisture content to the flat surface. As it gets thinner, it will tend to warp. I have found it usually sorts itself out eventually, and yes, carve it thickly, stick it in a well aerated place for a while and let it all relax, then keep carving. Don't force it flat, if you want to get it to sit flat, spray the driest surface (usually concave after warping) with a bit of water and leave it for 10mins.

 

[ctregan]

Thanks Matthew, The back is still rather thick so I should still have some room for flattening.

So far I like this phase of the bass building project the best. I am going slow, but having lots of fun!

 

[JKoehler]

Is the back of your bass slab cut? Sometimes that makes a difference between that and quartered.

 

[Don Harris]

Looks great! Seems like I read in the Johnson and Courtnall violin making book about this happening. I think that it said it would work itself out when you hollow the other side. Looking for it now, I can't find it... It happened to me a bit on my bass top.

 

[forester]

nice..nice...plainsawn i suspect..it would take a big time cherry to get quartersawn those widths.