Terry K said

All this puts me in mind of patching an old goatskin water
bladder with a piece of new leather.

Also, cost benefit analysis, proper surface preparation, who
knows what?

All ties in with chemical bond curing. How about contact cement
or other "primer" over old poly, followed by more poly / glass?


John M wrote:
Terry
Please note I never said the epoxy repair would not be stronger than the
same in polyester. Lets take this to the extreme and say epoxy is 100 times
stronger and many think this is the case. Why on a 25 year old boat would
anybody want one side to be 100 times stronger than the original deck. I
think I did mention proper workmanship counts which precludes contact
cement.
No doubt Matts repair will be stronger and probably prettier than mine but
strong enough is strong enough.
John


My sentiment, too. With whom are you in dispute?

I am interested in knowing if there might be a primer of some sort
that might improve the mere 13,000 lb(whatever!) per sq inch bond of
poly on poly that is supposedly not sufficient to be trustworthy
when compared to 18,000 (whatever!) epoxy glue.

How did the old guys work up the nerve to trust oakum and white lead
jammed in all those lapstrake planks? Wonder what it's bond strength
was, 10 lbs per sq inch? The nails would each contribute, what, 200
lbs per nail? Could structure and configuration and application have
anything to do with it?

My HR28 seemed quite happy with the approx 9:1 taper, one sided, one
splot, external conical wad patch over a removed 1.5" thru hull
hole, with one layer of glass inside just for worries sake, as per
the Gougeon brothers advice. Of course, the HR was about 1/4" thick
solid glass, and some will say, built like a brick tank to begin
with. (Cobham armour, anyone?)

Neither welded titanium nor epoxy could have performed better in any
imaginable circumstace. After the boat was destroyed by arson and
nearby glass burned and melted, the patch was still unnoticable,
still trustworthy, still about 5 bucks cheaper, still gelcoatable,
if one wanted to gelcoat under bottom paint. Another gold plating
option unexcercised.

I can not see where using a thinner epoxy splot would actually save
any appreciable weight, either. Of course, new construction maxi
racers, engineered all to hell for every imagined marginal advantage
doesn't exactly reccommend itself either, after what seems to happen
to aramid and carbon fibre racing boats exposed to one inch higher
or one knot faster waves and winds than designed up against.

This epoxy thing seems like a sickness, mania, or sales hype to me.

My whacko buddy was rabid about Mission brand speakers being
unarguably, vastly superior while arguing in his commonly
bewildered, strangely motivated state. My test equipment was
irrelevant in that it did not appreciate subjective, sensible colour
of sound, and phase, or something. I simply maintained that the
possible .00001% undetectable "improvement" over my old EPIs was
irrelevant to the application, cost benefit wise, considering the
way premium prices. He went incohate, popped his wads! Too much
meth? Stock in the company? Or, just innocent testosterone?

I would really like to believe, but no epistle has arrived, as yet,
and the light required to see such epistle remains dark.

As far as the material for replacement core is concerned, balsa is
primarily spacer. It's strength really isn't appreciable. Old
plywood scraps is as good or stronger, if a little heavier, if kept
dry. Small pieces, isolated by plasic dams is adequate, at least.

Terry K