It may be the single greatest advancement in making sailboats affordable but fiberglass is horrible stuff to work with! Here you see me emerging from the forward anchor locker where I’ve been grinding a 2sq-foot section directly into my own face. Even with a shop vac sucking air out of the compartment it would so rapidly fill with dust (which was also filtering into my foggy goggles via the ventilation holes) that I was doing most of this by feel. No doubt the wost job yet on the boat but we’ll see what’s to come…
This was just a quick side project cleaning up the locker for a little more glass and repainting but I spent that whole day grinding fiberglass. Mainly I was prepping the half dozen or so through-hulls which we are going to be glassing back over:
First, each through-hull was ground down to give a nice beveled edge. West System calls for a 12-1 bevel in order to achieve the same strength as the original fiberglass. We, of course, cheated. My boat was built in a wonderful age when people couldn’t engineer fiberglass down to the last molecule and were forced instead to just pile on some extra to be sure. This resulted in an incredibly strong hull which is solid fiberglass and nearly an inch thick in places! Now imagine following the book to the letter- we would be grinding away the hull in a 24″ circle, just to patch a 1/2″ hole.
Obviously the lesson here is to never follow directions. Instead, we ground everything out to about a seven-inch diameter. We chose this because it’s the natural diameter made by the contour of a well-used 4-1/2″ grinding wheel but if anyone asks I’m going to say it was the result of lengthly and difficult calculations. (Learned-the-hard-way tip: When grinding beveled edges always use an old, worn grinding wheel. When I chucked a new one on the sharp right-angle edge quickly cut jagged grooves into my nearly-smooth bevel)
Once ground out to our exacting standards, each hole needs to be backed so that new glass can be pressed in firmly. To do this West System recommends using a piece of plastic or something similar firmly pressed against the inside of the hull so as t assume the curve of the boat. We, of course, cut some corners. Instead we just went on the inside and quickly applied two layers of fiberglass cloth over the holes, sealing them and providing enough of a backing to allow patching from the outside. (Beveling and patching should always be done from the outside so that water pressure or impact damage will be trying to push the repair in tighter rather than pop it out.)
This article was syndicated from Safe At Harbour But Meant For The Sea: DIY Sailing with Paul Calder