Crown, was RE:Curve on Bridge Bottom

[Richard Brekne]

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Hey Dale...

So you actually gave that a try then eh ??? Good for you... nothing like
good old hands on experimentation to make things clear in ones mind eh ?
Actually I did it both ways myself. Never really thought about the
difference between arc lengths and chord lengths before. The math is
easy enough for sure... but it left me personally scratching my head
saying like you seemed to do... "nahhhhh... can THAT be ??"  So I took a
thin piece of molding (easy to bend) about a meter long and dinked
around afterwards... then got to wondering just how much it would take
to get a .05 inch difference and was suprised at the result.

"Doing the math" is of course a virtue a lot of us could persue more
then we do, but then that doesnt always contribute much to understanding
or perception of a thing. I suppose thats because we all think
differently and thats really a fascinating thing in itself me thinks.

Now, tho I suppose some few may mind... I will ponder a bit more about
why this and a few other facts we've seen makes it meaningless to view
the panel as a buttressed arch in any sense.

I wonder, if you had absolutly rigid supports, and no ribs at all, how
much support such a mild arching piece of wood like our generic
soundboard would have for any given load over a given period of time.

Thanks for the posting Dale.

Cheers

RicB



Anyways that

Erwinspiano@AOL.COM wrote:

> In a message dated 5/3/2002 6:18:31 AM Pacific Standard Time,
> RNossaman@KSCABLE.com writes:
>
>
>
>> Subj:Re: Crown, was RE:Curve on Bridge Bottom
>> Date:5/3/2002 6:18:31 AM Pacific Standard Time
>> From:RNossaman@KSCABLE.com
>> Reply-to:pianotech@ptg.org
>> To:pianotech@ptg.org
>> Sent from the Internet
>>
>>          Rick
>
> , Ron
>   Well it does seem doeable at first thought but, it's not.  I toook a
> long rib (60 ft. radiused) unattached to any thing and simply bent it
> down flat as an experiment. Imperceptable change in length to the eye.
>
> No more argument from this casual observer>
>   >>>>Dale >>>>>>>>>
>
>
>>
>> >Just trying to figure out why Dale got the notion that the panel
>> would
>> >spread by
>> >0.05 " (1,27mm).
>>
>> Just eyeballing, it seems a reasonable enough first guess - until
>> you check
>> the math. It's just another of the 7.3 billion things that aren't
>> what they
>> seem to be at first glance, traditional wisdom, or intuition. Of
>> course,
>> it's just a matter of opinion that the math is right, and we haven't
>> heard
>> all the expert estimates yet.
>>
>> Ron
>
>
>




--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html


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