Soundboardcrown

[Peter Kestens]

> -----Oorspronkelijk bericht-----
> Van: pianotech-bounces@ptg.org 
> [mailto:pianotech-bounces@ptg.org] Namens Richard Brekne
> Verzonden: maandag 16 december 2002 22:11
> Aan: Pianotech
> Onderwerp: Re: Soundboardcrown
> 
> 
> Where ya from there Peter ??

Belgium, my friend, Belgium.  Do you know Danny Boddin?  
> 
> As to your question, I think you will have to provide us with 
> just a tad bit more specific information.
> 
> As in... how dry did you get the board before glueing the 
> ribs on.... etc.
> 
> Tell us the whole story in detail and I am sure you will get 
> the answer you are looking for


Environment humidity was about 60%, that's normal in Belgium (but after
reading other mails, I think to high for gluing ribs)  Concerning the
humidity of the wood it self, I can't tell you.

I made the board and placed it upside down (has to, otherwise you will
get reversed crown)  in the press for gluing on the ribs. The wood of
the press bends just enough when you blow the hoses for receiving about
1 cm of crown 
The strange thing is when I eye-checked it,  the crown seems to have
disappeared (ie, when the board came out of the press, one really saw
the crown) .  But now, when I'm heating it to dry before gluing it in
the piano, and checked it with a straight piece of lumber I have crown
(about 12, 13 mm) across the ribs, the highest point of the board is
where it has to be, and I see  a little bit of negative crown along the
ribs (although this could be caused from heating the board, so it'll be
warmer in the center as on the ends)


Greetings 



Peter 
> 
> Cheers
> RiCB
> 
> Peter Kestens wrote:
> > 
> > Collegues,
> > 
> > I've build my first soundboard and I have to say, It looks 
> very good.  
> > I also glued the (flat) ribbs on and gives a crown, about 
> 3/8 inch by 
> > bending them, during gluing, with an compressed air press.  
> But a week 
> > later, I could not place the board in the piano earlier, the crown 
> > diminished and the board returned to be as good as flat.  
> My question
> > is:  is this normal or what is the cause.  And is there 
> somebody who 
> > can tell me how much crown he gives and what's staying 
> after a week, 
> > month (I mean the board only stocked in the shop, not placed in the 
> > piano).
> > 
> > Thanks a lot for the replies.
> > 
> > Peter Kestens
> > 
> > _______________________________________________
> > pianotech list info: https://www.moypiano.com/resources/#archives
> 
> -- 
> Richard Brekne
> RPT, N.P.T.F.
> UiB, Bergen, Norway
> mailto:rbrekne@broadpark.no 
> http://home.broadpark.no/~rbrekne/ricmain.html
> 
> _______________________________________________
> pianotech list info: https://www.moypiano.com/resources/#archives
> 
>