epoxy alone

[Delwin D Fandrich]

----- Original Message -----
From: "Ron Nossaman" <RNossaman@cox.net>
To: <pianotech@ptg.org>
Sent: June 08, 2002 6:21 AM
Subject: Re: epoxy alone


> Glyde,
> In the case of the Conn, it should be fine because the existing bolts are
> holding it from separating more. It would probably be just as fine if you
> didn't do anything to it at all. This is likely the case with the
Wurlitzer
> too. Given a piano where the lags have pulled out and there's a gap all
the
> way across the top, I wouldn't trust a repair without bolts. Looking down
> into these gaps, I usually (not always) see a relatively clean separation
> at the glue line with little splintering of the wood. That means you won't
> have a wood/epoxy/wood joint when you glue it back up. You'll have a
> wood/old glue (that failed)/epoxy/old glue (that failed)/wood joint. Why
> wouldn't the old glue that failed the first time not fail again this time,
> with an indestructible layer of epoxy hanging on to it like grim death?
> Epoxy alone might work, or might not. It might work temporarily or
> permanently. It might just barely hold, or be something you couldn't break
> if you wanted to. How would you know how well it's working until it fails?
> I wouldn't trust it. I am reasonably certain that 4-7 3/8" carriage bolts
> won't fail under a load that can be overcome with a couple of C-clamps,
and
> as long as I am unable to properly clean the old glue from the joint, I
> think I'll keep using bolts.
> Ron N


I agree. Most vertical pianos built in the past 40 or 50 years have used
heat-setting (that is via RF energy) adhesives to bond the pinblock to the
back assembly. The process works well when constant attention is paid to
details such as open time, even spread, consistent RF power, cleanliness of
the electrodes, consistent (and adequate) press time, moisture content of
the wood, etc.

Unfortunately, many piano makers didn't (don't) always do this and have
ended up (still end up) with joints in which the adhesive has dried but only
partially cured, or boiled and lost its adhesive strength, or.... By using
just epoxy you will end up with a joint that is only as strong as the
already-failed original adhesive.

When in doubt -- through-bolt.

Del