Kent Chasson wrote:
For what it's worth, I also do as someone else suggested and brace my flat tops at a lower humidity to help with the going concave issue.
That's what I used to do, and will again whenever I get back to building. The preventative dryness protection was really a byproduct in my mind, with the main reasons being tonal. Bracing it dried out and relatively flat, allowing it to swell in to a crown as it re-humidifies results in some noticeably different tonal qualities than bracing it directly in to it's final shape. It adds different internal stresses in different areas, and sounds different. It controls the top in a different way. Wish I could be more specific than that, but
. The word I've often used is "shimmer", not that that means anything really.
This was a technique we independently arrived at when I was at Bryan's, and rather naively though it something new and innovative at the time.
Of course it's been around for a long time though, and is how Steinway has been putting the crown in to their soundboards for at least the last century. I'm sure makers of many other instruments have done the same.