The Rot Doctor


Subject: Question (42' Egg Harbor)
Date: Thu, 08 Aug 2002

Hi there!!

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.