"60' vs. 100' Radius Board"

[Alan W Deverell]

Del & Dale etc.

I don't know the history underlying the adopting of the 60/100'.

I do NOT know of any scientific research having been done to measure
the properties of different radii of curvature.

Can anyone please help or direct me to sources of this information.

AlanD (trying to grow his own soundboard)

>-----Original Message-----
>From: owner-pianotech@ptg.org
>[mailto:owner-pianotech@ptg.org]On Behalf
>Of Delwin D Fandrich
>Sent: Saturday, June 27, 1998 4:03 AM
>To: pianotech@ptg.org
>Subject: Re: "60' vs. 100' Radius Board"
>
>
>Dale,
>
>Who said any of these were "standard?" I've never actually
>measured a soundboard
>with a 60' crown radius. Has anybody? This is because the
>crown radius of the
>piano soundboard is an ever changing quantity. Among other
>things, it varies
>dramatically with changes in ambient humidity. This is
>especially true with
>compression crowned boards, but the crown radius of all
>soundboards -- with the
>notable exceptions of laminated panel construction -- is
>going to change as
>humidity changes.
>
>The actual design crown radius of a soundboard assembly
>depends on how the
>soundboard is designed and built. If it is a pure
>compression-crowned soundboard,
>then the crown radius is primarily dependent on the moisture
>content of the panel
>when the ribs are pressed on, the stiffness of the ribs
>resisting the development
>of the crown and the humidity level of the factory in which
>the soundboard is
>being pressed. If the rib cauls are radiused, then this must
>be factored into the
>equation. If the ribs themselves are crowned, then the
>results will, once again,
>be quite different.
>
>Depending on the type of sound we want to get from a
>particular instrument and
>depending on the soundboard shape and the location of a
>particular rib on that
>soundboard, we will use one of 5 different radii. None of
>them are as large as
>either 50' or 60'.
>
>I really don't care what the soundboard looks like after it
>is ribbed. I care a
>lot more about what it sounds like once it's assembled into
>a piano and loaded
>with a bunch of strings. I'm not building salad bowls, I'm
>building pianos.
>
>Regards,
>
>Del
>
>-------------------------------------
>
>Daleboy@aol.com wrote:
>
>> Dear List,
>>      Just a lil' question about Soundboard radius
>configurations..........
>> In the past the SB installers that I was associated with
>were using a radius
>> of 100' on Steinways and a 60' radius on Mason &
>Hamlins........how come most
>> everybody has gone to a "universal" 60' and in some cases
>a 50'...???
>> A 50' radius board pre-installed must look like a salad
>bowl (chuckle).
>> Curiously yours,
>> Dale Whitehead, RPT
>> Franklin Piano Restorations
>
>
>
>