Soundboard Installation & MC

[Erwinspiano@AOL.COM]

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In a message dated 4/23/2002 9:08:29 AM Pacific Standard Time, 
pianobuilders@olynet.com writes:


> Subj:Re: Soundboard Installation & MC 
> Date:4/23/2002 9:08:29 AM Pacific Standard Time
> From:<A HREF="mailto:pianobuilders@olynet.com">pianobuilders@olynet.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 
> 
> 
> 
> 
> ----- Original Message -----
> From: "Farrell" <mfarrel2@tampabay.rr.com>
> To: <pianotech@ptg.org>
> Sent: April 23, 2002 4:12 AM
> Subject: Re: Soundboard Installation & M 
>  
>                 Del, Ron,Terry
>   
>                 I Read each of your post and I think I have a diiferent or 
> additional  point of view  about the comments about the rim having  having 
> no effect on holding crown. The rim in my view at least is a supporting 
> agent to crown.
>   Let me explain. Although from what my colleagues  Ron /Del have stated 
> about emc at the time of ribbing and to the precrowning of ribs and such I 
> can say our methods are similar except for the redesign factor.
>     This to say were all building a pretty stiff soundboard system. When 
> I'm setting my bridge height for bearing I do this as a dry fit with clamps 
> and screws and such. With the plate installed over the board and screwed 
> and fastened down I then prestress the board with wedges before cutting 
> down the tops of the bridge to the height I want. Thus setting my bearing.
>    Once I,m happy with that I remove every thing and finish the bridge, 
> glue it on the board and glue it in the piano somewhere between 6 to 7% emc 
> or so.
>  In spite of the board being very stiff I find that it is much more easly 
> forced down during my bearing pre-stressing procedure and it demonstrates 
> much more flacidity( is that a word?) than after it is glued to the rim.
>    With the rib ends  and board perimeter at last are glued to the rim the 
> board takes on an dramatic increased dimension of stiffness. 

   So I will humbly disagree that the rim is not a supporting agent of the 
crown for without it the strings would squash more of the crown out as the 
rib ends and board edge are moving outward and lifting. Without the Rim  the 
rib ends and board edge  would still woggle around and lift when depressed in 
the middle.
  The other isuue is that although the bearing is essentially a downward 
force it does push out wards and into the rim at least a bit once the board 
IS glued in. Since we have an arched system, vaguely similarto the concept of 
a flying buttress used in cathedral construction,it is a resistive element.
 How much is I think part of the debate here. 
    I'm not saying the rim does alot to hold a crown from diminishing  I'm 
just saying it's a supporting agent which aids the boards stiffness.
 >>>>>...Just my two cents worth--------Dale Erwin>>>>>>>>>>
     


> Tery wrote
> > What argument would there be for drying prior to installation?
> Del wrote
> With a compression-crowned board? It is easier to work with and glue into
> the rim if it is dry, having little crown.
> 
> With a rib-crowned board there is just the matter of consistency. You don't
> want the board too dry or too wet--both have a negative affect on the glue
> bonding strength. We rib our boards at 6.5% and glue them in at 6.5% to
> 7.5%.
> 
> 
> >Terry
> > Has this become the "standard" because the "masters" did it that way back
> when it was a fact that the rim supported the crown?
> Del
> It has never been a 'fact' that the piano rim supports the crown though 
> many
> have believed this over the years. Some argument can be made that beveling
> the rim--as is the practice of some--does have some nominal effect on
> soundboard crown, but it is very short-lived. Consider that this effect is
> greatest in the treble region of the soundboard panel and yet this is the
> region that typically looses its crown--certainly the stiffness related to
> crown--the earliest in a compression-crowned soundboard system. Obviously,
> the effect is minimal.
> 
> 
> >Terry
> > I suppose if you flat ribbed it and dried the bajeezers out of it, the 
> rim
> just might help to hold a bit of crown - at least until it got off the
> showroom floor!
> 
> If the rim actually did support crown you'd never see a M&H with a flat
> board!
> 
> Wood--primarily the spruce used in the soundboard system--simply has too
> much compliance and is to susceptible to long-term creep for the rim to 
> have
> any real function in sustaining crown.
> 
> Del
> 
> 


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