Official Luthiers Forum!

I am building my first concert size uke using the Kasha style bracing for the first time from the Georgia Luthier plans. I have never used this style bracing and I have never used walnut for a top, only spruce and cedar. Any advise for the thickness of the top being walnut? do I need to lighten up the bracing a bit more when tuning?

The wood I got as two protective boards with a redwood guitar top a friend gave to me. Will make a nice little 1 piece back and top.

Thanks

Rob

I've not built using Kasha style bracing, but have made quite a few ukes with hardwood tops.

My test for thickness is the longitudinal stiffness of the top (I pretty much ignore cross-grain stiffness because my normal ladder bracing deals with that). I want to be able to flex the top appreciably with light finger pressure to get around 1/2 inch deflection for a soprano or concert size top without much effort - the wood should feel springy, but I shouldn't be working hard to deflect it.

All my hardwood tops end up thinner than 2mm, and the smaller the body size the thinner the top wants to be. So the camp uke I made (8 inch diameter body) ended up below 1.5mm. I'd guess around 1.8mm for concert, but it really depends on the individual properties of the wood. Even two consecutive boards can have different longitudinal stiffness. I'd take it down to 2mm and then start flexing.

Standard bracing for a concert is two ladder braces and three fans, and the risk with Kasha style is therefore adding too much weight to the soundboard. Every fraction of extra weight on such a small soundboard reduces the playing volume, because it requires more energy to get the soundboard to move. You'll want to take this into account when sizing your bracing - I've no idea why the right answer would be.

For what it's worth, my reading suggests there are no tonal advantages to Kasha bracing on a uke, except perhaps that if you plan to use a low G the balance between strings might be a little more even.

Thank you! That gives me a good place to start!