Epoxy Bridge repairs

[Farrell]

I agree with you Joe - no need for clamps - assuming the bridge hasn't moved
more than an eighth to a quarter or so of an inch. If it is actually loose
and you can move it with your finger, then perhaps a clamp is in order just
to hold it in position - otherwise no clamping. Just fill the gap with a
good gap filling thick epoxy, stick in pins, wait a day or two, and string.

I use West System epoxy resin, hardeners and fillers:
http://www.westsystem.com/  My favorite for a cracked bridge is #404
High-Density Filler. The following is from the West System web site:

404 High-Density Filler
404 High-Density filler is a thickening additive developed for maximum
physical properties in hardware bonding where high-cyclic loads are
anticipated. It can also be used for filleting and gap filling where maximum
strength is necessary. Color: off-white.

Also from the West System web site:

Adhesive Fillers vs. Fairing Fillers

Fillers are used to thicken the basic resin/hardener mixture for specific
applications. Each filler possesses a unique set of physical
characteristics, but they can be generally categorized as either Adhesive
(high-density) or Fairing (low-density).

Adhesive filler mixtures cure to a strong, hard-to-sand plastic useful in
structural applications like bonding, filleting and hardware bonding.

Fairing filler mixtures cure to light, easily sandable material that is
generally used for cosmetic or surface applications like shaping, filling or
fairing.

Just wanted to point that out Joe. Even though they use the term "Adhesive"
filler, you don't need to clamp these epoxy mixtures. They are indeed gap
filling.

Terry Farrell

----- Original Message -----
From: "Joseph Garrett" <joegarrett@earthlink.net>
To: <pianotech@ptg.org>
Sent: Tuesday, January 01, 2002 7:16 PM
Subject: Epoxy Bridge repairs


> All,
> Several have suggested "clamping" the epoxy! I strongly suggest that, if
you
> want a failure, go ahead and clamp it! The only failures I've ever had,
was
> when I attempted to clamp a warped, (read split), bridge while using
epoxy.
> Epoxy is a CO-hesive substance NOT an AD-hesive substance. ie is bonds
> better with itself, in volume, than with other substances. There are some
> epoxies that are meant to be "clamped". The West systems ADhesive epoxies
> are in that group. These are very specialized epoxies. Personally, I find
> trying to get clamps in the proper positions on a bridge, is really
> difficult and falls into the "make work" category.
> An item I forgot to mention, in my last post, was the use of dental
scrapers
> to the fine cleanup of the pin/termination point(s) are really the way to
> go.
> IMHO CA glue has no place in a piano, except for a last ditch effort on a
> defunct pin block. CA glue has a nasty habit of breaking down over time. I
> did the research and found this to be true. (Flame suit zipped tight!)
> Regards,
> Joe Garrett, RPT, (Oregon)(Go Ducks!)
>