Grand Rim Construction

[Delwin D Fandrich]

----- Original Message -----
From: Stephen Birkett <birketts@wright.aps.uoguelph.ca>
To: <pianotech@ptg.org>
Sent: May 17, 2000 6:21 AM
Subject: Re: Grand Rim Construction


> Del wrote:
> > Interesting.  For a project a few years back I dry-pressed some rims --
> > i.e., normal veneer lay-up, no glue -- and studied the results after
varying
> > periods of time.  (Don't ask why.)
>                               ^^^^^ Now you've done it...Why??
> > After the veneer lay-up had been in the
> > press for a week or so, the veneers had taken on a very definite set.
They
> > certainly didn't "pop...back to almost flat after a spell."  I would
assume
> > that with the liberal application of water (from the adhesive) the
veneers
> > would take on even more of a set.
> >
> Probably with thin veneers this is what happened. Harpsichord builders in
> the past have used all of: cold soaking, dry heat (i.e. fire scorching)
> and cold dry to bend their bentsides. Now these are thicker than your
> typical modern veneers you would have used, so probably the cold dry
> bentsides did not take on sufficient water from the glue to plasticize
> much. Also, sizing everything before gluing reduces the water transfer to
> the material.
>
> Stephen
---------------------------

Veneer thicknesses used in modern piano rims ranges from less than 1/16"
(approx. 1.5 mm) up to 1/4" (approx. 6.4 mm).

When I said "dry-press" I really meant "dry-press."  No water or glue was
involved.  Looking at the results I assumed that the permanent deformation
of the wood rim veneers was simply time-dependent deformation (creep).  And
that as time passed this deformation would gradually relax the induced
stress, i.e., 'stress relaxation.'

Del