Epoxy vs CA

[Delwin D Fandrich]

Frank Weston wrote:

> ----------
> > From: Glen_Deligdisch@sil.org
> > To: Pianotech@ptg.org
> > Subject: Epoxy vs CA
> > Date: Tuesday, March 17, 1998 8:00 AM
> >
> >      Dear List,
> >
> >      I want to thank all of you that responded to my 30 minute epoxy
> >      question.  The information you gave was just what I needed.
> >
> >      Just one more little aside.  Talking to the folks in the hobby shop
> >      revealed some interesting opinions.  They said that model builders
> >      coming to their store preferred epoxy over CA.  I asked why.
>
> As one who has more than a little experience in aviation, both model and
> otherwise, I can unequivocally state that the opinion expressed by the
> store is pure hogwash.

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During the late 80's I was involved in some experiments that involved bonding a brass
device to maple. Since this would have had to be done in production, setup speed was an
issue. I contacted what were then the three largest manufacturers of CA adhesives and was
assured by all of them that CA adhesives would be inappropriate for this application for
basically three reasons:
    1)    The parts would be under constant vibration and CA would probably not hold up
well under these conditions,
    2)    One of the substrates was wood and during application much of the CA would wick
into the wood and the resulting bond would be weaker as a result, and
    3)    One of the substrates was rigid (brass) and one of the substrates (wood) was
not. The wood would swell and shrink slightly and this would place a changing shear stress
on the CA joint leading to ultimate failure.

Now, that was approximately ten years ago and I'm sure much progress has been made in the
development of CA adhesives. For one thing, thickened, and "toughened" CA's were not yet
on the market although they were available for testing. Like all other adhesives that I
know of, CA's are excellent for some applications and inappropriate for others. The wise
technician will learn which is which.

So far, I would have to agree that epoxy adhesives do have a better track record where
longevity and "toughness" is concerned.

ddf