Subject: Question (42' Egg Harbor)
Date: Thu, 08 Aug 2002
I saw in one of your q&a pages that you stated that covering the entire hull
with fiberglass presents its own set of problems. I have a 42' Egg Harbor
that I plan to re-plank with plywood strips instead of cedar and laminating
the entire hull with fiberglass (or west system epoxy) with roving and
kevlar fabrics. What are the special problems I can expect? Any info is
greatly appreciated!!! Thanks!!!
Interesting question! I certainly hope your plans include the use of
marine ply for this rebuild.
The Q&A comments you refer to are intended mostly for those who want to
take a planked boat and sheath it in fiberglass. It hardly ever works
because the planks will continue to expand/contract with heat/moisture
changes, the sheathing cracks, water gets in, and separation and rot occur.
It is doable, though, if 1) the boat is completely dried out (kept under
cover), 2) all seams are routed out and filled with a soft wood spline
(pine or western red cedar, for example) epoxy bonded in place, and then
sheathed with light glass cloth and epoxy resin. We are in fact
beginning such a process now with our old tug.
If you started with a dry frame and marine ply and all
bonding/seam-filling was done with a high-grade epoxy (our Tropical
Hardwood Epoxy Adhesive is a "soft" epoxy and would be perfect for such
an application) then your results would almost surely be favorable.
For our tug, we are going to vary this procedure somewhat. Instead of
using epoxy/glass for the final coating, we are going to use at least 2
layers of our ELASTUFF 120 followed by at least 2 more layers of our
Elasta-Tuff™ 6000-AL-HS polyurethane. We have tested these and are
impressed with their characteristics. No cloth is required and the
coating will always retain a degree of flexibility impossible to obtain
with epoxy resin. Such a coating system would waterproof the hull
totally, for all practical purposes, and have good impact resistance. It
would also be easily repairable. The Elasta-Tuff™ 6000-AL-HS cures with a
matte-gloss finish, which we prefer to the high gloss of painted surfaces.
I don't believe that the polyurethane system would add any significant
structural strength to a hull, which in the case of our tug is hardly
required. If your plans include the use of the epoxy/glass to help add
structural strength, then you should be sure to stick to that procedure.
Don't even think about using anything but an epoxy resin!
I would also suggest that all ply strips be saturated with our CPES
(Clear Penetrating Epoxy Sealer) after they have been cut and trimmed
and are ready for installation. All drilled holes for any type of
fastener should also be CPES-treated. All the testing we have done --
and we've done a lot -- show that the use of CPES on plywood
significantly improves its resistance to wood deterioration and delamination.
If you go through with this project, keep us posted! And feel free
anytime to come back if you have questions.