If it's not broke . . .

EVERY TIME I SEE an advertisement for an epoxy barrier coat, I flinch. I am reminded of a terrible mistake I made while trying to waterproof the bottom of my boat. It was an attempt to make sure that my 26-year-old Cape Dory would never fall victim to the dreaded boat box, the blisters that knowledgeable people call osmosis. But it turned out to be a big waste of time, labor, and money.

It occurred to me one day that I should remove the great wodge of bottom paint that had built up over 26 years. None of my boat’s previous owners had bothered to scrape the bottom down to bare fiberglass. So, at the next haul-out, I set to. It took me weeks, working on my own, to remove all the old modified epoxy antifouling paint, and when it was all done I was very glad to see that underneath it all the  gel coat was as good as new.

But I couldn’t leave well enough alone. The devil came to me during the night and whispered: “Now that you’ve got all the paint off, why don’t you apply a good barrier coat to prevent osmosis?”

“But she hasn’t got osmosis,” I pointed out. “Her bottom is perfect.”

“Ah, but she could get it at any time — especially now that you’ve removed those thick layers of paint. And besides, when would there be a better opportunity to barrier-coat the bottom? Everybody’s doing it, you know. You’ve seen the advertisements, haven’t you? Osmosis is a dreadful thing. You don’t want osmosis,”

Yes, I had seen the advertisements. And yes, the devil had his wicked way with me. I applied two coats of epoxy barrier coat, following the instructions meticulously. On top of that I applied two coats of modified epoxy antifouling paint. And so I went about my daily tasks smiling and whistling happily and thinking to myself that however my good old Cape Dory might deteriorate in the coming years, she would at least never catch the boat pox. Yeah, right.

Two years later, when she was hauled out for new antifouling paint, her bottom was covered in tiny blisters. I couldn’t believe my eyes. I called in a surveyor. He laughed. “Why did you put on a barrier coat if there wasn’t any osmosis?” he asked. “If a boat has been in the water for 26 years without blistering, there’s not much chance she’s going to get blisters now. What made you do it?”

“The devil made me do it,” I said.

“Well, you’d better send the bill to the devil because you’re going to have to remove the barrier coat,” he said. “It’s not a big problem — the blistering is between the gel coat and the barrier coat; it’s just cosmetic, not a structural problem — but all those pimples will slow you down terribly in light weather. Take her down to bare gel coat again, and just apply straight antifouling.”

Thus, I learned the hard way that you must never give a fiberglass hull a barrier coat unless the hull is absolutely dry. And I don’t mean surface dry, but dry right through. It can take many months for a hull to dry out, even if you use hot air to help it along.  And you’ll need a moisture meter to find out if there’s still any water present in the layup. If there is, your barrier coat will simply seal it in.

The other thing I learned is that you shouldn’t barrier coat a hull that’s spend 10 years or more in the water without developing blisters. I would have saved myself a whole lot of time, labor and money if only I had remembered the wise old saying: If it’s not broke, don’t fix it.

Today’s Thought

What cannot be cured must be endured.

— Rabelais, Works  

Tailpiece

“Darling, will you still love me after we’re married?”

“Sure, why not? I’ve always been partial to married women.”

(Drop by every Monday, Wednesday, Friday, for a new Mainly about Boats column.)

It's no longer a death sentence

I’M GLAD TO SEE that the hysteria over osmotic blistering of boat hulls has greatly died down over the years. There was a time, early on in the fiberglass era of boatbuilding, when a diagnosis of osmosis was considered to be the equivalent of a death sentence. But since then the truth has seeped in gradually — like cancer in humans, osmosis in boats isn’t necessarily fatal.

Osmotic blistering of the hull, or what used to be known as the dreaded boat pox, affected about one in four boats, although fewer modern boats are affected now. It’s caused by the migration of water vapor through the gelcoat into the laminate of glass fibers and polyester resin that we call GRP, or glass-reinforced plastic. The blisters usually manifest themselves in the outer one-tenth of the GRP.

Blisters come in all sizes, but luckily most of them are fairly small. Consequently, most cures involve nothing more than drilling out the blister site with a conical bit, letting the hole dry out, and then filling it with epoxy and filler.

If you’re really unlucky and have a more severe case of blistering, the gelcoat will have to be removed — peeled off by a professional, usually. The hull must be dried thoroughly, often for several months, and the gelcoat must be replaced by coatings of epoxy or vinyl resin.

Bad cases of osmosis are comparatively rare but they are expensive to fix — often amounting to 50 percent of the boat’s value or more — so the resale value of an affected boat is low.

Although we now take a more casual approach to osmosis, it’s best not to let things get out of hand. Examine the underwater hull every year for osmosis. Catch it quickly, while the blisters are still small and fix it.

Today’s Thought

Build me straight O worthy Master!
Staunch and strong, a goodly vessel
That shall laugh at all disaster,
And with wave and whirlwind wrestle.
— Longfellow, The Building of the Ship

Tailpiece

A grateful importer wanted to show his appreciation to a Customs officer who had smoothed the passage of a large consignment of  exclusive French perfume.
“Here, I’d like you to accept a large bottle of our most expensive scent,” the importer said.
“Sorry, sir, but the regulations don’t allow us to accept gifts.”
“No problem,” said the importer. “Tell you what. I’ll sell you this bottle for 25 cents.”
The Customs man looked at him thoughtfully. “In that case,” he said, “I’ll take a dozen.”

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)

Don’t let blisters bug you

“SHOULD I BUY a boat with blisters?” That’s the query from a reader in San Diego. “Cautious” has fallen in love with a 10-year old, 30-foot sloop, but he’s scared to tie the knot. He’s afraid to commit, because when he had her surveyed he found she had “a whole lot of dime-sized blisters on her bottom.”

Well “Cautious,” my advice is to grit your teeth and buy her. Nobody’s perfect, and no boat is, either. Although fiberglass boats have been around for more than 50 years, there’s still a lot of misinformation doing the rounds, especially regarding the dreaded boat pox.

It’s reassuring, therefore, to hear the experience of David Pascoe, a marine surveyor based in Destin, Fla., who says that in 30 years of surveying and examining 4,000 hulls, he has seen fewer than 10 cases where blisters have resulted in serious structural degradation of a hull.[1]

We’re talking here of dime-sized blisters. In 99 percent of the boats Pascoe has surveyed, blistering involved only the gel coat and the surface mat — neither of which is a structural part of the hull laminate.

Pascoe says that even boats with numerous blisters up to about 1-inch in diameter usually show no significant weakening of the plastic. As a result, “moderate blistering on an older boat rarely impedes the sale.”

As a matter of fact, Pascoe reckons that by the time a boat is 8 or 10 years old, “whatever is going to happen to the hull has probably already happened.” That means if she hasn’t developed blisters yet, she’s not ever likely to, so don’t be tempted to apply a barrier coat.

It’s quite another matter if a new boat develops blisters, of course. On a boat that’s been afloat for only two or three years, it’s likely that blistering is just the beginning. That’s not good news. But one that’s been afloat for eight years or more without developing blisters is a pretty safe bet.

Interestingly, Pascoe doesn’t even think it’s necessary to do anything about small blisters. Admittedly, they make the hull more difficult to paint and they will slow the boat down slightly, but: “If blisters cannot be shown to be causing significant damage, then repair is certainly not mandatory, despite the many horror stories you may hear from people trying to sell you a costly repair job ... Bear in mind that blister repair jobs are now big business for boat yards, so that taking advice from yard managers may not be a good idea.”

He makes another good point, too: “Further, you should be aware that the number of failed blister repair jobs that surveyors find is very high. No one’s ever going to know why blister repairs fail because no one is going to spend the money to find out.”

So go ahead, “Cautious.” Be brave. Put your money where your heart is. Who else is going to see your new girl-friend’s bottom anyhow?

[1]http://www.yachtsurvey.com/BuyingBlisterBoat.htm

Today’s Thought
The desire of perfection is the worst disease that ever afflicted the human mind.
— Fontanes, Address to Napoleon, in behalf of the French Senate, 1804

Boaters’ Rules of Thumb, #127
Locating faint lights. To find a faint light, such as a star, at night, look a little to one side, or above or below where you might expect to find it. If you look straight at an object, the light rays fall on an area inside the eye that is not as sensitive as the surrounding areas. So faint lights are often first seen in or toward the corner of the eye.

Tailpiece
”Why do you call it love at second sight?”
“I didn’t know she was rich when I first saw her.”