Optimum thickness for red cedar soundboard?

[Greg Martin]

My next project is a 17" carved arch top I bought a WRC sinker split billet. it has between 28 and 33 LPI. I was told it was in the river at least 50 years.And has been air drying since 1995. My question is whether a sinker will have a different Youngs modulus reading because it has been in water so long. All this leads to the question of top thickness and tone as I start tuning the top.

[Alan Carruth]

I've only worked with one sinker cedar top, so take this with some salt. The Young's modulus along the grain was right in line with the density, and, of course, cross grain E varies all over the place. It was some of the softest wood I've ever worked with, denting about as easily as balsa. I made a nice sounding guitar, though.

If you can come up with a density reading that might give some idea of how thick to make it, but there are lots of variables there as well.