Build Your Dream Boat #21

By glenlmarine · Wednesday, June 2nd, 2010

Today we’re going to talk about fiberglassing a wood boat. Many are under the impression that when you apply fiberglass to a wood hull, it makes it structurally stronger and therefore, thinner or less quality wood can be used. This is NOT correct.

First, let’s define what we mean by “fiberglass”. We are referring to the application of fiberglass cloth over a plywood boat which is then impregnated with either epoxy or polyester resin. The purpose of fiberglass is to protect the wood from abrasion and provide an easier surface to maintain. Any strength that comes from fiberglassing is incidental and not meant to replace the proper wood or craftsmanship.

Years ago, polyester was the resin of choice but we never use it, nor do many of you. Epoxy is a superior product, so when we refer to resin in this Newsletter, we’re talking about epoxy resin.

Fiberglassing is an option when you build a plywood boat; it is not required. But, we recommend it simply because it’s easier to maintain a fiberglassed surface than a painted wood surface. Plus, it’s far better to scratch some fiberglass off your boat rather than wood and have to deal with the possible rot that will inevitably happen if unnoticed.

If cost is a factor and the boat will not be sitting in the water, by all means just seal the wood with a wood sealer or a coat or two of epoxy and paint it. We won’t beat you.

I think for some, fiberglassing is simply intimidating so that keeps them from doing it. But, once you watch the DVD of Allyn fiberglassing various boats in the Glen-L shop, you’ll have the confidence you need to do it yourself. Seeing someone else actually doing it really makes the process seem less of a challenge.

We offer Fiberglass Kits for most of our wood designs. These kits provide the epoxy, hardener and cloth to cover the bottom, sides and transom of the Glen-L boat you are building. Plus, you get a sampling of some application tools such as squeegees, foam rollers & disposable brushes. Just click on the kit name or item number for a listing of the specific contents.

You’ll notice that for most designs we show three fiberglass kits: One contains Glen-L Poxy-Shield epoxy resin and we just call it “Fiberglass Kit”. The other two kits contain either System Three General Purpose or their Silver Tip resins. The General Purpose resin is very comparable to our Poxy-Shield, but we offer both as some of our clients have used the System Three products before and are used to them. The Silver Tip is a top of the line epoxy that is non-blush. With the other epoxies, once the epoxy cures it emits what is called an “amine blush”. This material needs to be removed with denatured alcohol (shellac thinner), lacquer thinner or acetone or even water prior to sanding. A no-blush epoxy is better to use if you are trying to achieve a natural wood finish.

If you are striving for a natural wood finish, make sure that the weave of the cloth is completely filled with resin. It usually takes 3 or 4 coats to accomplish, but don’t get hung up on how many coats-just make sure you can no longer see the weave of the cloth. That will make a huge difference and as many can attest, it’s tough to go back and re-do it if you don’t do it right the first time!

So there you have it, a quick primer on fiberglass. I highly recommend our DVD though, because nothing compares to actually seeing it done. If you have questions, you can email or call us or visit the Boatbuilder Forum because your question has probably already been discussed.

GLEN-L WORD OF THE WEEK:

WATERLINE LENGTH - Length of the boat at the designed waterline.

Significance:
One of the factors used to determine the speed potential of a displacement boat. The longer, the greater the speed potential. The overall length is irrelevant; overhangs fore and aft do not increase “hull speed” potential.

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