[pianotech] Measuring Crown Radius

[Ron Nossaman]

On 7/13/2011 10:48 PM, David Love wrote:
>
>
> RN
> It made no point at all, and was a ridiculous comment since a panel
> wouldn't crown without a rib. It addressed nothing. Make some attempt to
> stay within reason.
>
> DL
> Of course an unribbed panel will crown.  Dry it down and glue it to the rim
> and let it take on moisture.  The expansion has to go somewhere. If the rim
> of the piano is beveled or if the board starts even marginally crowned
> upward it will continue to crown upward.  Since you are arguing that the
> ribs that would have been bent by the expanding panel would have a negative
> impact on load support you would then expect that this crown, unribbed panel
> would support more of a load than a ribbed, crowned panel.  Is that what you
> are saying?
>
>
> RN
> It's not a premise. It's elementary mechanics and physics. A flat rib
> will begin to support load as a beam only after it's pushed concave. If
> the panel is holding it up in a crown, it's not supporting anything.
>
> DL
> Of course.  You could also say that a flat rib won't be pushed concave until
> it begins to support a load.  But ribs on a CC board when the panel is glued
> into the rim are not flat any longer.  They are bent.
>
> See the attached photo.  Are you telling me that a flat rib bent into a
> crown and fixed at the ends won't support anything until it's pushed
> concave?

It's clear to me that you have no intention of ever making any attempt 
to understand what I've been trying to tell you. I tried, but I've 
wasted enough time on you.

Ron N