I have an old plywood rowboat which periodically is repaired with
fiberglass cloth. This has worked very welll- the boat is now about 70
I just did some minor repair work including bottom painting and
fiberglassing. The bottom is still quite rough as over the years there
have been many layers of paint which has peeled off unevenly.
Even heavy sanding won't fix it completely.
For years it has seemed to me that painting the entire bottom with
fiberglass resin (no cloth) would make an extremely durable and
water-resistant primer, to be painted over with polyurethane marine
Is there any reason this shouldn't work really well?
Thanks in advance!
That is historic and should be preserved! I recall plywood being used for
sailing dinghies in the late 40s here in the UK but not before WWII. I'd be
loath to do what you are proposing.
I sanded down many dinghies of the 50s era and when not wishing to explore
too deeply used stopper to smooth off the surface. I could feather that down
so smooth that I could get a fine finish to the paintwork.
I could easily be wrong but wonder whether you might be creating a layer
that would be pierced and trap water?
The nearest that I could find to stopper these days is Sikkens.
This actually was a custom-made sailing dinghy. My father had it
on his cabin cruiser when they went to the 1939 World's Fair in NY.
It has a lot of freeboard, very practical in the chop here on Cape
Cod, MA, US. It was punctured in a couple of places during a
hurricane, but my father patched it.
I too am concerned about trapping water, which may be a good
reason not to do this. However, with fiberglass patches applied
liberally over the years, particularly where the sides meet the
bottom, and still no serious rot anywhere, I am inclined to be
somewhat less concerned. However, I will consider your thoughts
Please note that I do not have the time or inclination to do any
kind of fine finish work on this boat. My goal is simply to keep it
leak-free and in one piece.
Thanks very much for your thoughts.
the resin bond will only be as good as the paint bond underneath the resin.
if the resin is applied to bare wood,then it will bond to the porous
wood,much stronger than to paint.
I'd use stripper and sanding to get down to bare wood before applying
www.systemthree has the Epoxy Book,a great resource about using epoxy
resins for fiberglassing.It's a free download.
Thanks for your suggestion. I really don't have the time or the
inclination to go down to the bare wood. I would have to take a
chance on the paint as a base. (Would check that carefully
before applying the resin, though resin over the paint historically
seems to give a very good bond.)
Will look at System Three.
Thanks very much.
After being patched with fibreglass, no wood boat maintains its
antique value (if any.) Main considerations seem to be:
1. Total weight of a boat with resin skin
2. Possible effects of the resin on the adhesive holding
together the wood plies (and no plywood glue made 70
years ago was expected to last long in a wet environment.)
So long as the resin skin were perfect, you might be OK.
Any scrape or imperfection might fatally weaken the whole.
1. Cured polyester resin is quite brittle. Fine with fiberglass cloth, not
good by itself.
I speak from experience...I once did all the considerable bright work on a
42' yacht with polyester resin; thinned it, brushed several coats, wet
sanded, polished with rubbing compound. It looked great. For a while.
Until it started cracking. Lopts of work to remove and replace with
2. The solvents in the resin *may* affect the paint to which it is applied.
OTOH - given the prevalent use of Bondo - maybe not.
3. Adhesion would depend upon the condition of the paint to which it is
applied. Since there are "many layers of paint which has peeled off
unevenly" I sure wouldn't trust the adhesion.
Best would be taken down to wood. You are disinclined to do that.
Next best would probably be to chemically strip paint, fair up clean surface
with resin and Cab-o-Sil or other filler, apply a thin, overall layer of
glass cloth and resin. then paint. That's a bunch of work too.
Given your constraints of time and interest, I think your best bet is to
simply paint; if necessary, use a conventional primer first.
Thank you both for your comments. As for antique value, really don't
care. As for fatal mistakes, fiberglass cloth has been rather crudely
slapped on this boat for about 30 years with no major rot occurring.
dadiOH's reply is really what I was looking for. I assumed there
would be an issue of flexibility with just resin, although where the
resin overshoots the edge of the cloth, I have never seen much
evidence of cracking, even in completely unsanded areas. (How
*do* you remove it once it hardens?) But then it has been applied
over polyester paint- perhaps that makes a difference.
I think your final advice to "simply paint" is a good one. I have
painted with Interlux, but have applied polyester resin (no cloth)
to a few ragged areas. Will see what happens.
Again thanks to you both.
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