The Rot Doctor


Subject: Fiberglass over Cedar
Date: Sun, 05 May 2002

I have recently acquired a 14' runabout constructed as a wooden frame and keel with cedar strip (1/4"x 3") laid butt joint square with what appears to be caulk in each joint, these joints are not tight fitting (1/8" gap) and then the outer skin was applied fiberglass.

The boat has been upside down in a backyard for a number of years the gunnels and frame appear to be good, the fiberglass had separated from the cedar, so it has been stripped completely and the cedar underneath is very dry and mostly quite solid. The deck is pretty well gone and most likely I will start from scratch on that.

My thought is to start with CPES on the cedar strips, but what should fill the gaps between the strips (or perhaps they do not need to be filled?) before applying a new fiberglass skin. Any recommendation for the reconstruction process would greatly appreciated.

Thanks in advance,
Bill R.

Assuming that the boat is going to be "dry-sailed", that is taken out of the water after use, you have a couple of options here:

1) Treat the cedar with the CPES, as you suggested, fill the seam gaps with our Fill-It Epoxy Filler, and then re-glass the boat with new cloth and EPOXY resin, such as our Layup & Laminating Resin. Considering that this is your personal boat and you want a long-lasting and strong covering, I wouldn't even think of using a standard polyester resin. They just don't bond that well with wood. The Layup & Laminating Resin applied to dry, CPES-treated cedar with a glass cloth, should last almost indefinitely. The glassed surface will have to be scuff-sanded prior to painting.

2) If the boat is going to "wet-sailed", that is allowed to sit in the water or spend a lot of time weather-exposed, you should think about filling the CPES-treated seams with our 3M™ 5200 adhesive/sealant, and then coating with our new ELASTUFF 120 (first coat cut 10% with MEK, second coat full strength), and then two coats of our Elasta-Tuff™ 6000-AL-HS. These are very tough flexible membranes and will allow the hull to expand that small amount it wants to with changing moisture/heat conditions. You will probably have to do some light sanding on the ELASTUFF 120 to smooth. The Elasta-Tuff™ 6000-AL-HS has the color built into the formula, so there would be no painting -- assuming you can find one of our colors that you can live with. The Elasta-Tuff™ 6000-AL-HS produces a semi-gloss, smooth finish and is absolutely UV resistant.

Because your boat is small, option one would probably work also under weather-exposed conditions. The expansion/contraction would be contained by the epoxy/glass sheathing.

Hope this has been of some help, and come on back if you have additional questions.