Bridge Crown

[Ron Nossaman]

>When building a new bridge, my understanding is that you will want to put a 
>concave curve along the long axis of the bridge bottom (or maybe you will 
>even want to modify an old bridge that does not seem to have the proper 
>bottom curve). But how much curve? I strongly suspect no approach to this 
>will be perfect, but we presumably should have some target in mind. Do we 
>clamp the soundboard into the piano (or install it), let it equilibrate with 
>the shop environment (letting it achieve its normal crown), and then attempt 
>to put the same crown as the soundboard has inversely on the bottom of the 
>bridge? Or do we want to guess at how much the board will compress under 
>string load and target that curve/crown? Or do we want to approach it in 
>some other manner? Or just put a 60-foot radius on the bridge bottom and get 
>some sleep?
>
>Ideas? Thoughts? Sarcastic criticisms?
>
>Terry Farrell
  

Flat. Works fine.

We did this on the list just a couple of months ago. The bridge is curved.
A crowned bridge will lay flat on a crowned soundboard. A flat bridge will
also lay flat on a crowned soundboard. A crowned bridge will neither
conform to the board better, nor support any more bearing by virtue of it's
crown. Having done them both ways, I can't detect any benefit at all to
crowned bridges unless you're charging by the hour. Nearly as I can tell,
the curve makes bridge crowning superfluous.

Ron N