Cabin Top Leaks

This column is a forum for sharing the vast range of practical paper towel. Stick the thumbtack into the wood as close to
experience accumulated by our membership and not just my the leak as possible, and put the end of the string or towel
favorite boat maintenance topics. It is intended to be the place into a bucket. The water will run down the string or towel
where you, the reader, can ask technical questions and either and quietly deposit itself in the bucket.
obtain direct answers in this column or direction to appropriate 3. Now go back to sleep or reading your book. You have done
reference material. all that you can do until daylight, and you won’t have to

Well “popular demand’ struck again I’m happy to say, so listen to… splat….splat….splat anymore.
we’ll depart from the originally planned series of articles and 4. Oh yes, remember where the bucket is so you don’t step
respond to a request for some maintenance / repair advise. into it in the morning.
Before proceeding though, I have to admit that what you are When daylight comes you have several alternatives. Which
about to read is based only on my limited experience. I am not a one you choose depends on several things; boat construction,
professional boat builder, nor am J in the boat repair business. size of the leak, size of your wallet, level of patience, etc. Going
But aside from the legal disclaimers, I have been messing from complex (expensive but thorough) to easy (quick but
around with boats for 35 years and during that time needed to hazardous to the long term health of your boat), here are the
repair a lot of different things myself (due primarily to lack of choices as I see them.
cash). If any of the pros that read this want to comment, A. Complete disassembly of the companionway trim and
please…please, let’s hear from you! framing and inspection of the area for deterioration.
So here it is springtime, a very rainy spring at that, and a Radical surgery!
reader asked a question about leaks in the cabin top, especially B. Localized disassembly of the structure in the leak area
around the companionway hatch. Well as luck has it, two years and a limited inspection. A measured approach.

ago this was my problem as well. It was discovered during a C. Caulk the area of the leak and hope there is no hidden

real downpour while sitting at our mooring. It was just a drip. damage. The ostrich approach.

Nothing to get excited about. Just one of those really annoying Whatever the case, you should not ignore it. You may choose

splat…splat…splat noises that overpowers your concentration to have someone else fix it if the alternatives are either “A” or

when you are trying to read a really great sea story on a dark “B”, but I would at least give it a good inspection.

rainy night. The only good part of this leak was that it wasn’t The decisions you make are based on what you find during

right over my berth. the inspection and many of the factors I joked about above. but I

So putting the book down, troubleshooting started! There think the basis of the decision is driven by the construction of
wasn’t much wind that night, so the water couldn’t have been the cabin top and your basic skills.

blown in past the baffles under the hatch. Further investigation With a solid fiberglass cabin top you can probably get away

revealed that pressing on the trim piece at the forward side of with choice “C” since fiberglass has a real high rot resistance.

the hatch opening forced water to squeeze out. The only way However, if the boat has wooden rails you may want to remove
the water could get there was to come in under the hatch rail. If and re-bed them so the rails themselves don’t rot. This repair
that was the case, the water was also getting into the wood should be well within anyone’s capability.

cabin top. I don’t know how long it had been going on, but I At the opposite end of the spectrum, the cored fiberglass

suddenly saw my biodegradable boat rotting out from under construction might require very detailed inspection that can

(over?) me as I slept. only be accomplished if you disassemble all of the companion-

The construction of the cabin tops on our Friendships is as way trim so you can see what’s behind it. If the folks who made
varied as the boats themselves. Wood (of course), laminated the boat didn’t seal the core completely when they were cutting
plywood, laminated plywood sheathed in fiberglass, solid fiber- _the cabin top to fit the companionway, you have a problem. The
glass, and cored fiberglass (usually with balsa) are some of the reason for this radical surgery is the fact that any water that
construction methods that are used. Leaks in any type of leaks into the sandwich is trapped. It soaks into the core

construction require at least minimum inspection to see what material and if the material is wood, such as balsa, it rots. A

the total extent of the damage or deterioration might be and rotten core significantly reduces the structural strength of

locate the source of the leak. My boat’s cabin top is fiberglass- sandwich construction. Fixing a large section of damaged cabin
sheathed plywood, but before we get into my story, let’s review _top that’s made with cored construction is better left to a pro. It

a selection of the initial actions that should or could occur. involves cutting out the interior surface and exposing the core

1. Localize the source of the water intrusion as best you can. so you can rip out the bad core material and laminate new

This step can be the hardest because water can migrate a _ material into the void.
considerable distance before it drips or runs down the Diagnosing the extent of the damage can be accomplished
headliner. with a reasonable degree of accuracy. Obviously the primary

2. If it’s a small leak get a thumbtack and piece of string. If diagnostic tool is your eyes. Visual inspection will usually give

the leak is larger, get a long towel or even a long section of (Continued to Page 7)
-6-

you many clues on where a leak is and the extent of the
damage. Hidden damage requires a different troubleshooting
method. I like to use sound, like sonar, to hear the differences
in material density of the wood or whatever is under the fiber-
glass. Good solid wood sounds like …well…g00d solid wood.
When you hit it, it goes thump. No hollowness, no echo, just a
deep base tone. Rot eats the lignin in the wood leaving voids in
the wood’s structure. When you hit it, it sounds hollow. Its’ one
of those things that when you hear it, you’ll know! The best
way to familiarize yourself with the sound is to start tapping on
good wood and work your way toward a known rotten section. I
used a small leather mallet because it won’t damage the surface,
but you can use almost anything. Just remember that the
hammer may cause more damage than you want, so tap
judiciously.

Another way you can locate the damage in a non-cored cabin
top is to remove the headliner and do a visual inspection. If the
damage is extensive, it will be obvious. You’ll probably pull
pieces of the wood or plywood off with the headliner. Less
extensive damage can be difficult to locate. One of the telltales
will be the stain that the water leaves on the surface of the
wood. After repeated wet / dry cycles a residue that contains the
breakdown byproducts forms on the surface. Probing the area
with a small penknife or ice pick will usually show you where
the weak / rotten areas are located. Plywood can be a little
tricky. Because of its’ layered construction, water and rot can
migrate down one layer yet leave the other layers untouched.
Tapping will usually work, but you may need to take core
samples to really home in on the problem.

Since I had fiberglass-sheathed plywood, and very little exter-
nal evidence of water intrusion, I used two methods to locate
the extent of my problem; sounding with the leather mallet and
drilled core samples. First I tapped….tapped….tapped on the
fiberglass sheath on the outside of the top. Using the differences

in the sound I outlined the suspect area which was about the
size of an8 % X11 piece of paper. I marked the area off with a
pencil. Then I took a thin-walled plug cutter and cut a hole into
the underside of the top near the point where it was leaking.

The hole was just deep enough to get a good wood sample but

not deep enough the cut through the fiberglass. This first

sample showed me that wood was not rotten, so I took three
additional samples. One was about 6 in. from the first, and
again showed no rot. The last two were taken in the center of
the area I mapped and again about 6-in. apart. The conclusion
of all this probing was that my problem was delamination, not
rot, Evidently there was just enough flexing of the delaminated
section so that when I walked on the cabin top the slight
movement broke the seal of the bedding compound under the
hatch rail allowing it to leak. It hadn’t been leaking for long
and there was no indication of moisture in the samples.

Now the issue was how to repair it. For this I went to the

Gougeon Brothers “West System” epoxy repair book. In it they

outline a procedure where you drill a pattern of small holes in

the top of the cabin, about an inch or two apart, that will accept
the tip of a small syringe. But the first things that had to be
fixed were the holes cut with the plug cutter on the inside of the
cabin. Luckily the holes took the next plug size up, so armed
with a little thickened epoxy they were set home and allowed to
dry. Next, a thinned mix of epoxy was injected into each hole of
the pattern that covered the area I had mapped while trouble-
shooting. The trick is to fit the tip of the syringe tightly into the
lowest hole and inject enough epoxy so it oozes out of the holes
above it or beside it. When it’s full of epoxy, put a match stick
or wood plug in the hole so the epoxy doesn’t run out.

The epoxy was left over the next week to setup. Finishing the
repair was fairly straightforward. The process of sanding,
filling, fairing, sanding, filling, and final fairing; followed by
priming and painting, and painting took the next two
weekends. The job came out pretty good, in spite of my amateur
status. The best part is that the leak hasn’t returned. I could
have had the boat yard do the job, but I always subscribe to the
philosophy that if I pay someone else to do the job, I’ve lost
twice; once when I paid them the money, and again because |
lost the opportunity to learn something.