soundboard?

[Newton Hunt]

Back in the bad old days tuners would put valve springs between the
board or ribs and the backpost or staunch ion to force some crown
back into a flat board.

I thought it a bad practice but after some discussion on this list
I realized that it can be a solution to an awful dissuasion where
there is no money for a new board.

I have a newish (8-10 years) Knabe which has a "rolled Bridge" and
there is actually considerable negative bearing.  The raucous
noises coming from this area in unpleasant and people do hear it. 
Springs may well be a "best fix".

How much tension should there be?  I don't know except you don't
want to break the board glue joints or increase bearing beyond what
is needed.  As long as there is _some_ crown and _some_ bearing
that is enough as long as the two are about equal.

> NEED this after the piano is finished being rebult

Pat, if it is being rebuilt then is the only best time to fix the
problem with a new board.  

A rocker gauge is often quite sufficient but it can give you false
positive results is the bridge is severely "rolled" where on side
of the bridge is high enough and the other side is low enough.  In
that care the component bearing gauge is the only way to go.

If the pianos has some crown but too little bearing then the plate
needs lowering but only as far as is needed to make bearing amount
and crown amount about equal.

This has to be fix before the end of the rebuild and not after.

		Newton