Fiberglass Setback

Peeling fiberglass off wooden boat
Peeling 6 oz. fiberglass cloth off the boat with a heat gun

I have not failed.  I have just found 10,000 ways that won’t work.                 — Thomas Edison

Adding a layer of fiberglass cloth to any wooden boat will add an enormous amount of toughness to it.  And if you do it right, the fiberglass is invisible.  That’s right — invisible.  The problem is in the “doing it right” part.

Okay, let’s step back a bit.

Stained wooden boat
The boat was stained with Minwax Gunstock stain before adding a layer of fiberglass cloth.

I finally finished sanding the planking on the boat.  The bottom and topsides were fair and I stained it with Minwax Gunstock stain.  The plan was to add 1 layer of 6 oz. fiberglass cloth to the sides and 2 layers to the bottom.  The bottom layers would overlap at the keel, and I would add 2 layers of strips to the chines to really toughen up these areas and provide impact protection.

It all went well until it didn’t.  We got the chines, both sides and the transom covered, and two additional coats of epoxy to fill the weave in one long day.  But there was just the slightest bit of cloudiness in the coating.  There was nothing to do but hope for the best and go home.

Making slow but sure progress

But the next day, under bright lights, the cloth was unmistakable.  There was a cloudiness, and in some places it looked like there was a veil over that beautiful woodgrain.

I tried to find a way to live with it for two days.  I researched what might have caused the cloudiness.  At first I thought it was the high humidity.  The relative humidity was 83% that day with a temperature that started at 84 F and ended at 83% and 90F.  But we had used WEST 207 hardener, and the literature said it was unaffected by humidity.  It seemed like the chine strips actually came out perfectly clear, but we used 209 hardener for those to get extra working time because of the high temperature.  I called the gurus at WEST System and asked what happened.

If you look carefully you can see tiny white dots in this freshly sanded layer of fiberglass and epoxy. These are pinhole bubbles in the resin exposed by sanding. This is a clue that your epoxy cured too fast.

They confirmed that the humidity was not a factor since we used the 207 hardener.  But we were too ambitious.  We needed to work slower with smaller batches of epoxy.  The epoxy began to cure before it had completely saturated the fibers of the glass.  That’s why the 209 hardener, with the longer working time came out clearer.

Then I asked what I could do to fix it. I was pretty sure I already knew the answer.

Yep.  Strip it all off.

Now that’s not a small task.  I was looking at about 3 extra weeks of work to get back to where I started.  But the WEST guy did say that if I could get an edge started, I could peel the fiberglass back with a heat gun.  Then I’d have to sand the remaining epoxy off.  But hey, not having to deal with the dust created by sanding a layer of fiberglass cloth off was worth it.  And it saved time as well.  It took 4 days to get the fiberglass off.  I’m still sanding the epoxy, but that will be gone soon–a couple more days.

And the silver lining to this cloud? (There’s always one if you look for it.)  The stain acts as a guide coat to help get the boat even more fair for the second go round.

So I’ll continue sanding.  Then re-stain.  Then wait for cool weather and work in small batches.  I’ll cover one side in a long day, rather than trying to get the whole thing done.

Nothing in this world can take the place of persistence. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent.                                                                          — Calvin Coolidge

7 Replies to “Fiberglass Setback”

  1. Hey Tim. What a bummer!
    Thanks for the tips on the subtleties of a perfect epoxy finish. Hard way to find out though. The problem should be better advertised in the product info.
    The Minwax Gunstock stain is interesting. Im planning on staining before epoxy finish is applied…when I get to that stage…. but have been worried about any adhesion issues and choosing the right stain product. Have you got any product assurance on that one?
    Love the posts and the project. Im at least 12 months behind you, but having just retired hope to catch up a little!

    1. Hey Chris,
      Yes. The folks at WEST said oil based stains are fine as long as you make sure they’re completely dry before coating with epoxy. If you can still smell the solvent of the stain, it isn’t dry. I wait several days after staining before coating.

  2. Tim, on top of persistence and determination I would add courage! Having achieved a beautiful finish on the mahogany planking it took courage to to do anything more to the surface, except varnish!

    1. Yes. Varnish would have been the easy way to go. But I would at least build up several layers of clear epoxy first. It’s much better at making the boat waterproof than plain varnish. It also provides a very stable substrate for any varnish you use. And you do need to use some kind of UV protection over the epoxy because it has almost none and will yellow and cloud over time if not protected. So my final coats will be some kind of varnish or Urethane clear coat with UV protection. That said, the added toughness of fiberglass makes it worth the trouble in my opinion.

  3. way to stick to it…i take it sanding off the epoxy coats means masks to keep particles out of your respiratory system, right? will it be more difficult to keep the finishes even in smaller spaces of area? to this untrained eye, the woodgrain work looks so beautiful

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