Out, Out, Bad Pox!
By Jack Owen
Article taken from Good Old Boat magazine: Volume 2, Number 5, September/October 1999.
“The shock of discovering bubbles on your boat’s
bottom is merely the prelude to a prolonged pain in the assets.”
Boat pox, osmosis, or blisters . . . call it what you will. Most fiberglass
boatowners prefix the blight with a salty expletive deleted. The shock
of discovering bubbles on your boat’s bottom is merely the prelude to
a prolonged pain in the assets.
Parnassus, my beamy Montego 25 sloop, was built by Universal Marine
in St. Petersburg, Fla., in 1980. That was just about the time I had sworn
off boat ownership in favor of crewing aboard OP (other people’s) craft.
But last year I lapsed. My reaction to a 40th school reunion in a room
filled with geezers jockeying for parking space for their walkers propelled
me to recapture the spirit of adventure I vaguely recalled from my youth
. . . that of owning a boat.
The sticker price of Parnassus removed most of the lumps from under
my mattress. And the discovery of a badly blistered bottom has siphoned
off the balance.
Twenty years ago the annual haulout to scrape, sand, and bottom paint
an earlier boat was a week-long project. My land-lubberly lifestyle during
the interim had not exposed me to the blister blight, which apparently
hit its zenith a decade ago when fiberglass, the panacea for all boat
hull maintenance woes, mutinied.
Today, many boat owners
– including me, now – are aware of the cancerous reaction of water collecting
under the hull gelcoat to create an odoriferous vinegary bubble of acid
formed when moisture – from the ocean outside, or bilge water inside –
reacts to solvents, resin, or additives in porous pockets beneath the
gel surface. Those voids, perhaps no bigger than a pinhead, may have been
created by just one speck of dust in the builder’s boatyard – so you can
imagine the possibilities. Or perhaps it was the failure of boatbuilders
to totally resin-soak every last fiber of chopped strand mat between the
gelcoat and woven-roving laminated layers. That inner skin of chopped
matting supposedly prevents the woven roving pattern from emerging on
the surface of the gelcoat, making the hull look like a floating waffle
. . . whereas the surface of a blistered bottom – once the pustules have
been pricked – resemble the pocked face of the moon.
Unfortunately, the aesthetics of what, primarily, would be the boat’s
profile under the waterline, is a minimal problem compared to the dire
predictions of fiberglass layers de-laminating, structural failure, a
cracked seeping hull, and death by drowning.
All this and much more, I learned from leather-skinned liveaboards and
margarita mariners lined up at the boatlift as Parnassus was hauled
out last June. After that, the boatyard manager, Jason Sprague, told me
my carefully estimated haulout and bottom job bill would have to be revised
upward . . . somewhere near the stratosphere.
A professional labor/cost guesstimate, quoted in one of the many magazines,
newspapers, and books about blisters I devoured researching the repair
process, projected a $350-plus-per-foot price tag. That included peeling
the bottom to the first layer of woven roving, re-glassing, fairing, and
barrier coating, then repainting the bottom with anti-fouling bottom paint.
Forking out the best part of $10,000 to float my boat, was not an option.
Fortunately, Old Slip Marine, Riviera Beach, Fla., is a “do-it-yourself”
yard. UN-fortunately, despite abbreviated classes at the Eastbourne Technical
School, England – 40 years ago – my handyman skills would make Rosie the
Riveter blanch. But, faced with a boatyard hourglass dumping dollars by
the day just for storage, I was shocked into becoming a semi-shipwright.
Jason explained the yard’s procedure for curing the ills, after waltzing
around Parnassus with a moisture meter which pegged off the scale
(25 percent) from the keel to the rubrail. The moisture meter indicates
how much potential liquid is trapped under the gelcoat, poised to provide
The blisters needed
to be popped then ground off down to the roving. Ideally, Jason said,
the hull should be professionally peeled to the roving. Then the boat
should sit and dry out until water drained out or evaporated, and the
moisture meter lowered to about five percent. To encourage that, the hull
should be pressure washed with a hot-water machine.
Estimated time: two to three months! Florida in the summer is not the
most pleasant place in which to don full protective dust-suit, mask, head
sock, and filter-respirator. All this prior to entering a still-air cavern
created by the environmentally-correct tarpaulin-shrouded hull of Parnassus in which to begin grinding.
During the summer of 1998, while Florida went up in flames, boatyard temperatures
and humidity readings competed to break the 100-degree barrier. It was
a tad nastier under the tarps, where the grinder created intrusive toxic
dust clouds of multi-layered old bottom-paint, gelcoat, and fiberglass.
There were more than 100 blisters, from pinhead to half-dollar size, for the grinder to eviscerate. I circled a dozen locations with a waterproof felt-tipped marker and marked them with date and moisture meter readings. Twice during the next two months, her hull was pressure washed with hot water to encourage the trapped water and acid to seek the surface.
After two months, no new blisters appeared, but there was barely any downward movement in the moisture meter readings. According to some experts, the hull must be totally dry before repairs can begin. On the other hand, there are those who have little faith in moisture meter results and prefer to patch and plop dinged hulls – wood or fiberglass – after an eyeball, feel, and balance determination.
The balance part of the equation is weighing whether the Band-Aid approach or boatyard advice method will leave a positive-dollar balance in the old bank account. Like all things connected with boats, it’s a compromise.
We opted to work within
the guidelines offered by the boatyard boss, plus snippets garnered from
old salts in their slips, marine hardware store employees – most working
to keep their own boats afloat – and published pundits, from boating journalists
to marine surveyors.
The following list of procedures worked for Parnassus and, today, knock-on-wood, she’s blister-free and floating.
Parnassus is my getaway
floating island, whether she’s tied up at the slip, moored in the lake,
or day-cruising when wind, tide, and time allow. There are no plans for
any solo long-distance bluewater voyages, ala Joshua Slocum or Robin
Lee Graham, in her future. She was designed to perform under MORC (Midget Ocean Racing Club) rules and as a comfortable family cruiser. There may
be moisture in her hull adding to her weight and slowing her down, but
whether she’s cruising downhill with a following wind at seven knots or less, we’ll be out on the water . . . sailing.
And a pox on all blisters!
At the time boat is hauled and pressure washed, the blisters will be most
apparent. Mark them before they drain or deflate. Wear protective goggles
when popping and scraping them. The liquid is often under pressure, and
a squirt in the eye can be harmful.
A grinding wheel should be used to smooth the cavity created by exposing
the blister pocket and to fair it down at the edges to allow epoxy filler
to meld with the contour of the hull. Sanding with coarse-grit paper does
not do the job efficiently.
The blisters are visual indications that pockets of acid exist under the
gelcoat. But there may be more latent moisture seeping from water tanks
or bilges within the boat, trickling through or trapped between layers
of fiberglass, moving toward the gelcoat. A two- to three-month drying
out period is a prudent step to take.
To encourage chemical liquids within the hull to leach to the surface
and to speed up the drying-out process, hot water washdowns are recommended.
The most widely touted method for patching blister damage, because of its ease of application, is the West System brand of epoxy products. However, the yard manager at Old Slip Marine claimed fewer customer complaints and a higher success rate when his experts used the Interlux two-part InterProtect Watertite compound. One can contains the base materials, a cream-colored putty-like gook, the other a blue paste containing the curing agent catalyst which binds both elements into a steel-hard set-up finish. The mix is two-parts cream to one-part blue.
Cowboy, the resident yard helper for the past decade, demonstrated the proven consistency, eyeballing amounts, texture, and color until the combination turned aquamarine. He advised only mixing sufficient material for about 20 minutes of work – depending on the temperature of the day. The approved boatyard palette is an ordinary piece of packing-box
cardboard. A wooden tongue-depressor is used for mixing.
Once the fill has set up, sand the entire hull (80 grit) to level out patched
blister cavities and rough the surface in preparation for the barrier and
bottom coats. Tip: least used is easiest removed. Because we were too liberal
in applying the mixture with a putty knife, when it set up solid as steel
on the hull surface, it added hours to the time needed to sand the fill
Scrub the hull down, using a stiff-bristle brush and hot soapy water
to rid the surface of dust and any dormant chemical residual. Interlux recommends
using their fiberglass solvent wash 202. However, when we tried it, our
workgloves dissolved, the linen-rag disintegrated, and our hands looked
like bleached prunes.
We skipped the next step: applying a barrier coat of Interprotect 2000E/2001E
which re-seals the hull and replaces the gelcoat. Although we had more than
100 blisters to repair, more than 80-percent of the original hull finish
(gelcoat) remained intact and unblemished. If, as the experts say, blistering
is formed where voids exist under the gelcoat because the water is trapped
under the skin, we reckoned the integrity of her hull – after almost 20
years – would survive a little longer.
We opted for Fiberglass Bottomkote ACT antifouling paint, based on the local
knowledge of the boatyard manager. Old Slip Marine has been a family-operated
business for more than three decades and is familiar with the barnacle build-up
potential of a variety of gunkholes, marinas, and slips in the area. The
reputed advantage of ACT as a soft paint permits the surface to wash away
by water movement over the hull constantly exposing fresh and effective
biocide. It also eliminated bottom paint buildup and, I hope, will require
less sanding to prepare the hull at the next haulout. We shall see.
Parnassus was named for one of the twin mountaintops in Greece, sacred
to the Muse. Her oft-deflated tender is the party animal Bacchus. Jack Owen
is a freelance writer and out-of-print bookshop owner on the poor side of
the lake from Palm Beach, Fla. He has crewed on corporate stinkpots and
has owned/ disowned several disastrous ragbags. He is a leading contender
for the newly created “Hard Aground Club” annual award for personally
visiting each of the sandbars in the Lake Worth Lagoon.