Polyster resin is not really very water proof. Water permeates it over
time. Epoxy is more water resistant. Epoxy is also less brittle than
polyster resin. So it less likely to crack when flexed. It is also
generally stronger. You use it the same as polyster resin. The mix is just
different, usually 1:1, 2:1 or 3:1 hardner. I personally like US Composites
http://www.uscomposites.com/ epoxies and they are very reasonably priced.
Big chemical companies make the epoxy ingredients and smaller companies
package and sell it so you're just paying for the name when you buy
something like West Systems. You can get a thin coat epoxy and paint the
inside of the hull. You can also seal your lumber with thin epoxy before
you start installing it. Make sure you really soak the ends well. You use
epoxy with fiberglass cloth just like you would polyster resin.

"anxious boater" wrote in message
.. .
Hi Jeff,

You sometimes don't know what you're getting into. Some advice I read and
didn't head - "If you find yourself in a hole, STOP DIGGING!"

Because of the stringers I also ended up pretty much gutting the boat. At
least I can now build something I'll be happy with.

A surveyor I talked to suggested that I epoxy the enitre hull while I was
doing everything else. You did that. I never asked him why I should. Why
did you go that route?

"Chehalis Jeff" wrote in message
oups.com...
Hi Steve,

I have a 1972 boat that had the same problem I spent the greater part
of last summer fixing. I read everything I could find to read about it
and then decided to do the job myself. It turned out great and I think
the boat is stronger and lighter than original.

I agreed to paint my dad's house (a bigger job than anticipated) in
exchange for the "family boat" that dad no longer used (but it was
stored in 'dry' storage.) After making my dad's house beautiful, I went
to load up the boat and stepping onto the deck I went right through. It
was rotted through and through. I then realized the deal I made with
dad wasn't such a great deal- well maybe for my dad it was, and that's
OK I guess.

Anyway I brought the boat home and went about stripping the boat down
(removing all interior upholstery and hardware) removing the deck and
stringers. I cut everything down to the bare hull and made sure to kill
any sign of mildew or mold (didn't want it growing under anything...)
Fortunately for me, the transom was OK - there were a couple of tiny
rot spots in it I was able to repair.

Now that I had a completely clean hull, I laid out stringers out of
Alaska Yellow Cedar (not for strength, but because it doesn't rot)
fitting them closely to the hull line. I made up cross-braces out of
marine-grade plywood. Before placing ANY wood in the boat, I first
coated it in thin epoxy that soaked into the wood (sometimes two coats
if it looked like it needed it) which didn't increase the weight of the
wood by much. This way I knew the wood was totally encapsulated. Then I
placed the wood into the boat, laid everything out and screwed/glued
the cross braces to the main stringers with cleats (also pre-treated.)
I also added supports for the deck (places to attach the deck and seats
down to the stringers/cross-braces.)

Once everything was in place I started lay up. I used a coarse
fiberglass mat (I used as large pieces of fiberglass mat as possible -
eliminating as many joints and overlaps as possible) for the first
layer. I did NOT use polyester resin, instead I used epoxy for the
entire job. This takes a little longer since I think it's important to
allow the epoxy to cure between coats which can take a week. After my
first layup, then I used a finer cloth over the heavy cloth, making
sure the joints and overlaps in this cloth were in different places
than the first layup. Again, I used epoxy and at this time I also
coated the entire inside of the hull. (One thing to make sure of before
you start this is to support the boat hull in such a way so that it's
not deformed [even a little] because however the hull is shaped when
you start, is how it will be shaped forever.)

After a lot of work and a couple gallons of epoxy, it came out
beautifully and the boat actually works better than ever. I think it's
a little stiffer and it definitely feels more solid
than before (that is, before it rotted out.) From what I removed from
the boat I could tell it was not put together very well... there was no
glass mat, only chopper material covering the stringers which is why I
think it failed. The thickness of the chopped glass varied a lot.

That's my story...


Jeff





anxious boater wrote:
I have a 1969 fiberglass (polyester) hulled houseboat. It's a
Thunderbird
Drift-R-Cruise. All the engine stringers and three interior stringers
are
shot. Everything I have read so far basically says to epoxy the
stringers in,
fillet and glass over. I am certain the first two steps were omitted,
either
when this boat was built or this job was done in the past. Some of the
inside stringers aren't even resting on the hull interior surface. From
what
I can see, water leaked in at the bow (and other places) and simply
migrated
to the back of the boat. The rot is really bad starting in the bilge
(the
stringers oozed out when I started cutting!) and improves some moving up
closer to the bow. Is this poor boat building, or just the way it was
done
back then?

Now I'm not so sure that I should put the new stringers in using the
current
methods. For example, will the vibration from the motors cause cracking
in
the hull glass if they are epoxied in, solid as a rock?

Thanks,
Steve