Soundboard shims via Spurlok method

[Farrell]

Epoxy is perhaps the best thing since sliced bread. I use West System for
zillions of applications. I use the Spurloc shimming system for soundboards.
I (strictly personal opinion - I realize epoxy should work just fine here)
like to use wood shims for cosmetic reasons and because I can really get
glue between the soundboard and the rib (assuming it is separated as it
often is) from the enlarged cut.

Regarding the Spurlock method. Be sure the board is VERY dry. I put several
50W Dampp-Chaser rods under the board with blankets over the top for several
days to a week. I stick a hygrometer on top of the board and see that it is
down below 30% relative humidity. Most important, watch the existing cracks.
You need to see new cracks opening up or lengthening of existing cracks
(look for light-colored wood at the crack ends). Drying the board will also
help to flatten it.

The last piano I did had quite a bit of crown to the board. I had some nice
four-foot long aluminum right-angle pieces for router truck guides, but the
crown was WAY too much. I used shorter sections. Try 18 inches. Try 24
inches. Just get it small enough that you can use the thick (are you using
the thick double sided tape?) tape, one piece at each end and the center of
the guide just touches the board. You can actually usually bend the rail
down a tad at the ends. This way you do get a little deeper cut in the
center, but not much. Your shim will be right down to the rib anyway.

Once you have your guides in place, make sure you only chew out a little bit
of wood at a time. Little bites. Getting too aggressive with the air grinder
will make the thing go wild (trust me, I know!). Just take out 1/8" depth on
a pass (you can do more, but when starting, only do a little). Do a modest
enough approach and the grinder should never take off from you. After you go
down to the ribs and need to make the cut wider, make sure you are moving
the grinder bit against the direction of rotation. And only cut a little bit
at a time. Use shims between the grinder and the metal of the truck to which
the grinder mounts to make small adjustments. Make sure cut is close to even
width along entire length.

I have been able to put a dozen shims in a board with not a crack/gap to be
seen. I even made a curved shim that went along the back side of a treble
bridge - used the bridge as a guide. Don't be afraid to go wide with the
shim if you need to make things nice and even. Cut your own shims any width
you need. All you need is a little table saw. I make mine and they work
perfect. That way I can go to my local lumber store and pick out perfect
matches for wood color. You mentioned you have gone as wide as you dare with
the shims you have. I made plenty of mistakes my first few tries - and yes,
had to make the cut a little wider. This is part of why I highly recommend
that you cut your own shims of various width out of 3/4 boards. That way, if
you goof, just set up your guides again and go real slow. You'll get it
right, and then use whatever width shim you need.

When you are ready to fit the shim into the cut soundboard, just pick a shim
that is narrow enough at its base, to fit all the way into the bottom of the
cut, and wide enough at the top to completely fill the cut. Then simply trim
off the bottom of shim to get perfect fit. You will likely be trimming off a
tad less in the middle of a cut because you may have routed a bit deeper
there because your guide was lower - but we are only talking 1/8" or less
here. I simply run my shims through the table saw to trim the bottom until
it fits. When the shim is too tall, it will bottom out on the ribs before it
fits perfectly to the soundboard edges. The perfect job is when the shim
bottoms out on the rig and at the same time it is snug against the
soundboard edges. When you get a good fit - watch out! It can be hard to get
the shim out because it fits so well (just tap it out from the bottom!)

If your routed cuts are straight and of consistent width, and your shims are
cut at the proper angle, you should end up with perfect fitting shims.

Prop your board up from below to force a crown into it (don't make it pop
out of the case!). Apply your glue of choice (I use hot hide) and apply
pressure from above (with whatever system you have available - I use go bars
to my ceiling). Let dry a day. Remove clamps, plane and sand.

I just think they look so dog gone professional.

I have no doubt that properly thickened epoxy would work well also. Maybe
I'll try it someday.......maybe.

Terry Farrell
Piano Tuning & Service
Tampa, Florida
mfarrel2@tampabay.rr.com

----- Original Message -----
From: "Greg Newell" <gnewell@ameritech.net>
To: "Pianotech forum" <pianotech@ptg.org>; "Master Piano Tech"
<mpt@talklist.com>; "College and University Technicians" <caut@ptg.org>
Sent: Monday, April 30, 2001 3:58 PM
Subject: Soundboard shims via Spurlok method


Dear Lists,
    I've got trouble. I just started using the sound board router system
the venerable Mr. Bill Spurlock sells. I don't like it! Maybe it's just
me but I can't get a handle on how to affix a rail to the crowned sound
board. I would be easier if the board was flat bu then I'd be replacing
it not shimming it. I've always been taught that a glue joint is only as
good as the mating surfaces. I have several small gaps in various places
and I've gone as wide as I dare with the shims that I have. Kind of like
the wobbly chair syndrome. I've never had a router bit cut so poorly,
chattering and pulling like it did.
    I am gluing the shim in now with as much of the gaps minimized as
possible but I'm finicky. I'd rather not see any at all. I think I'll
switch gears here and try the epoxy method. Would any of you be so kind
as to detail this method to me along with the product you use and your
results with it. Before the forum police come to get me, I know this has
been posted before. Nevertheless I'd appreciate a complete approach if
any of you are so inclined.
    Thanks a bunch! You all are the best!!!!

Greg
--
Greg Newell
Greg's Piano Forté
12970 Harlon Ave.
Lakewood, Ohio 44107
216-226-3791
mailto:gnewell@ameritech.net