Official Luthiers Forum!

if i put in an F hole.....is this going to happen.

I suppose it could happen, but I've never seen a guitar do that.

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"Act your age, not your shoe size" - Prince

Yes, that will happen. I am assuming your drawing is exaggerated to illustrate the point. I am assuming that instead of carving the radius into the top (as in an archtop) you are just bending a flat top plate over a curved semi-solid core. I have done something similar and run into the same problem.

But if the curvature is not too severe, the problem is barely noticeable. The place you'd notice it the most is on the inside of the ends of the "f"s, where you have a tongue of wood that is going across the grain. One way to mitigate this is by angling the f-holes such that the long axis runs perfectly parallel to the center line of the top. If the "f-holes" were really just slots then you wouldn't have this problem at all. But plain slots are kind of ugly so perhaps you can come up with some design where those cross-grain tongues are minimized or eliminated.

Curving the top too much, f-hole or not, can run the risk of splits down the road, especially if there isn't extensive bracing inside. You may also think about bracing the inside of the top if you're going to bend it that way. A lot depends on the wood and its thickness.