Rim Construction

[Delwin D Fandrich]

----- Original Message -----
From: "Farrell" <mfarrel2@tampabay.rr.com>
To: <pianotech@ptg.org>
Sent: October 31, 2000 6:57 AM
Subject: Re: Rim Construction


> ... One additional item related to this is why
> the predominance of maple as opposed to oak (red or white). I don't have
> tech specs for either, but most all oaks are seemingly not too far from
> steel! And I do realize oak has been used in rim/framing in the past. But
> why sooooo much maple. Is it that maple is harder? Or is it that maple is
> considered hard enough, but still workable. Does it take glue better? I
have
> used oak (white only - red rots) extensively in marine applications and it
> bends quite easily (with a little heat) and works well with epoxy. Just
> curious. Any thoughts?
>
> I did not realize that some pianos were built with hardwood block rims. I
> take it the design is similar to Bosendorfer or Bechstein with their
spruce
> blocks, i.e. rectangular block with long axis vertical, edge glued with a
> couple laminations on inner side and outside?
>
> Terry Farrell
> Piano Tuning & Service
> Tampa, Florida
> mfarrel2@tampabay.rr.com
------------------------------------------------------------

Oak has been used.  And it works quite nicely.  The criteria is density and
'strength.'

Probably it was a matter of which wood was most readily available -- read,
least expensive.  Both are adequately dense enough and strong enough to do
the job.  As are quite a large number of other woods; birch, beech, I think
I've even seen white ash on occasion.  Also, considering how few of them
there are, oak rims seem to have a somewhat higher tendency to separate, so
possibly it was a bit more difficult for them to glue.  I've not seen this
to be particularly catastrophic, just something to watch.

(Baldwin's smaller traditional grands -- the M, R and L -- used maple for
generations.  Then they were switched to poplar, but only briefly.  Sustain
dropped so significantly that the inner rim was switched back to maple, but
still with a poplar outer rim.  I understand the outer rim is now also once
again maple.)

Epoxy was not around in the late 1800s and early 1900s.  Even if it had
been, it's not likely it would have been used as a construction adhesive.
It is considerably more expensive than most woodworking adhesives, very
messy to use in production of this type and there would be no compelling
reason to put up with it.  Maple worked fine and, until the forests nearly
ran out of maple trees, quite inexpensive.

Block rims are built with the blocks on the horizontal.  They were sawn out
and stacked flat with all joints overlapping.  Much like a cutting board
laid sideways.  Construction techniques varied, but usually what we now
think of as the inner and outer rims would have been made as a single piece
with each block being cut to the full width of the whole.  Above the
soundboard shelf the blocks would be cut to the width of just the outer rim.
They were typically veneered on just the outer surface below the
soundboard -- i.e., the inside surface was not veneered -- and on both above
the soundboard where it could be seen.

Del