[pianotech] Measuring Crown Radius

[David Love]

Really, cut with the ad hominem and self aggrandizing attacks.  You haven't
adequately answered the question, at least not to me and I am open to it.  I
have no personal agenda.  First, by your explanation then heavier rib sets
in compression crowned boards would tend to increase panel damage under load
(after they are glued into the rim we're talking about) by virtue of the
fact that they are pulling down harder than lighter rib scales.  Further,
proportional deflection might be increased with heavier rib scales by virtue
of the fact that they are pulling down harder.  Is that what happens?  I
can't answer that question but it certainly seems counterintuitive.  Second,
at what point in the continuum of combinations of various amounts of
compression and rib crowning does one system transform into a completely
different system.  

Don't waste your time any further answering, I know you've given it your
best shot and I know your time is precious.  But neither am I incapable of
understanding reasonable explanations adequately expressed.  

David Love
www.davidlovepianos.com

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Ron Nossaman
Sent: Thursday, July 14, 2011 7:31 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] Measuring Crown Radius

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