Rim Bevel

[Erwinspiano@AOL.COM]

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In a message dated 2/17/2002 7:19:04 PM Pacific Standard Time, 
mfarrel2@tampabay.rr.com writes:


> Subj:Rim Bevel 
> Date:2/17/2002 7:19:04 PM Pacific Standard Time
> From:<A HREF="mailto:mfarrel2@tampabay.rr.com">mfarrel2@tampabay.rr.com</A>
> Reply-to:<A HREF="mailto:pianotech@ptg.org">pianotech@ptg.org</A>
> To:<A HREF="mailto:pianotech@ptg.org">pianotech@ptg.org</A>
> Sent from the Internet 
> 
> 
> Terry you wrote
> For all you soundboard builders that use tighter arcs than a 60-foot 
> radius: I think the 60-foot radius arc is common on most old pianos (at 
> least the crown was about that when the board was new), and I suppose many 
> newer ones.
> 
>>>>>>>>Just when you thought it was safe to think something.......A 60 ft. 
crown is a starting point for many. I've measured some spots in my boards 
when glued in and yet unstrung that measured any where from 55 to 70 ft. in 
the bottom and in  the treble 50 to 25 ft. arcs. I really doubt any new 
Steinway ever had even one spot that had a sixty ft. crown and I don't think 
they even had a specification. If they had one I suspect the radius was 
flatter like 75 to 90 ft. They and other makers dragged a dozen nicely dried 
boards out of the hot box on a soggy summer  morning and by the time the 
ribbed the last one in the afternoon the e.m.c.s had changed dramitically. 
What was that you say specifications? E. m.C. squared = a flat board. Da kno.
   
           And I assume that the edges of a 60-foot radius board will have an 
angle of about 
> 1-1/2 to two degrees at its edges - about the same as the bevel on the inner 
> rim. Now, when you go to 40 or 30-foot radii - or even tighter - surely the 
> edge of the board forms a significantly steeper angle from the horizontal 
> than that of a 60-foot radius board.
> 
> My understanding is that the bevel of the inner rim is very important to 
> the soundboard maintaining its crown. 

>>>>>>>>I have installed two of my boards onto  flat rims and those boards (A 
6 ft. Weber and a Hardman  5 ft. 10 " and both soft rim pianos) ended up with 
less crown than any other in my practice. I was a little concened. That was a 
long time ago and honestly other factors could have entered in. Inexperience? 
However I see no reason to think that gluing a crowned board to flat surface 
is a design practice I want to endorse. It would seem that a flat rim 
introduces another unneeded bending strain. I feel more comfortable gluing 
the edge of a crowned board to something that's going in the same direction. 
That being said a beveled rim doesn't seem to inhibit more steeply crowned 
ribs from retaining their shape.
        I agree with Del that once the board is strung it has flattened 
greatly. Hey you know in that case the board  was probably designed to be 
jjjjjjjjjust the right hieght when under string load.to match the rim 
bevel.!!! Who knows.

> 
> So, the question is do you put a steeper angle on the rim bevel, do you 
> angle off the outer 3/4 inches (however wide the inner rim is) of the board 
> to match the existing rim bevel, or do you just clamp the darn thing 
> together and all seems to work just fine.

.........>>>>>>>> What you said. works
          Just  Fuel for cannon fodder--Dale Erwin
         San Diego was great!

>   
> 
> 


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