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There
are few problems that can cause more damage and detract from the
value of your boat than window, porthole and hatch leaks. Even well
constructed boats will eventually develop leaks simply because boats
are not totally rigid structures. In fact, they twist and flex quite
a bit, and poorly constructed boats flex a lot, which is why we
see so many entry-level boats that more or less just strain the
water before it enters the interior.
I am constantly amazed at the number of boats I
see where the owner has simply smeared some caulking around the
window frames of leaking windows. Let's start with the point that
not only does this make a mess of your boat, but this a complete
waste of time. When you develop leaking windows, ports or hatches,
no surface remedy is going to solve the problem.
The leaks usually develop because the seal between
the window frame and the fiberglass part of the boat has broken.
The break in the seal can be so small that you can't even see it.
This is because of the capillary effect, which draws water into
the smallest of cracks and more or less acts as a water pump to
keep bringing water in. Its also why water can enter at one point
and be coming out somewhere else, perhaps two feet away from the
source of the leak.
Most boats now have aluminum window frames, and
which constitute the major source of leaks. This is usually not
the fault of the frame, but of the poor design of the structure
to which the frame is attached. Please see the "Windows,
Windows, Those Leaky, Leaking Windows" essay for
photos and a more detailed discussion of design. Many boats are
so badly designed that no matter what you do, you're not going to
be able to stop the leaks. Before tackling the project, here's what
to look for:
- The window frames are the only thing holding up the flying
bridge.
- The side decks are weak, and when you walk on them, it pulls
the deck and house side away from the window frame.
- Frame is not channelized, but consists of just the frame and
glass clamped against the house side with screws.
- The window frames are black and you live in the south.
If you have a poorly designed boat where the window
frames are holding up the flying bridge, or are very low to the
side decks and the deck flexes when you walk on it, it is not likey
that you can stop the leaks by recaulking the windows. This is a
design problem that you're pretty much stuck with.
Black aluminum, anodized or painted, is
a problem because aluminum is a great heat conductor, and when they
heat up in the sun they expand and break the caulking seal, as well
as helping to make the cauking brittle. To stop leaking, you have
to use a non-hardening caulking so that the caulking can move with
the expansion. To deal with this problem, you have to remove the
frames, rebed them and refasten them less tightly than they were
previously installed. The reason is that if the frames are drawn
very tight, they will squeeze all the caulking out and not allow
any movement without breaking the caulking seal. In this case, its
best to use one of the specially formulated non-hardening silicone
epoxy compounds and use 3/32" shims to prevent the frame from
being drawn completely flush, particularly along the top of the
frame where most leaks develop. Draw the frame tight against the
shim - which is only inserted along the edges - and then let the
bedding fully set before pulling the shims out. Once the caulking
has fully set - say a week - then go back and retorque the fasteners
just a little tighter. What you now have is a gasket against which
the frame can be drawn up against.
This method works for all types of windows, including
glass sandwiched between two pieces of wood. The trick here is to
NOT initially draw the frame completely flush, thereby squeezing
all the bedding out. If the frame starts to leak at a later date,
you then have the opportunity to tighten it even further, whereas
had all the bedding been squeezed out, retightening would have no
effect because there's really no gasket in there.
Removal You must completely remove the frames
and clean all the mating surfaces thoroughly before applying the
bedding. Use toluol or lacquer thinner or acetone to completely
clean off all old bedding. Be sure to clean the fiberglass mating
surfaces as well. If there is corrosion on the surface, you should
sand it off completely as water will wick right through the aluminum
oxides and defeat your efforts.
Bedding Glass If you have water leaking
under bedded glass, such as on a front windshield, the only way
to fix this is to remove the glass and rebed. Don't even think about
smearing caulking around it because that won't work. Besides, it
is not particularly difficult to remove the glass and do it right.
After removing the glass, you also have to thoroughly
clean the channel in the frame in which it sits. Most window channels
will be full of crud and corrosion. If you do not get it perfectly
clean, all your effort is likely to be wasted, so be sure to do
a good job. Two people can reset three windshield lites in a half-day
so its not a big job.
To reset the glass, use a silicone based window
glazing SPECIFICALLY designed for this purpose. Do not use plain
old silicone sealer. Clean the glass edges thoroughly with an alcohol
based glass cleaner. Plain old Windex is fine. What you're going
to do is to apply the window bedding very heavily to the frame channel
and then press the glass into place, squeezing out the excess that
you will later trim away with a razor blade once it fully cures.
Don't attempt to smooth out the excess with your finger because
you'll just make a mess of things. Yes, its going to look ugly at
first, but the razor blade will trim it away as nice as can be.
Before setting the glass in place, you'll need
a dozen 2mm or 3/32" shims for each pane of glass. The reason
for this is the same as with window frames: you don't want your
bedding to be too thin. Use any kind of stock sized material for
the shims. Before applying the bedding, set the glass back in the
frame and shim it into the final position that it will be in when
the job is finished. From the interior, now place the shims right
along the very edges of the frame between frame and glass. You can
either use tape, or silicone sealer to hold them in the exact location.
Silicone will work best because they won't move, but you have to
give the silicone time to set before installing.
After the shims are in place, pull the glass back
out and apply the bedding. Then set the window back into the bedded
frame.
Note: You can use this same procedure
for rebedding leaking hatch frames, especially on decks that flex
a bit. Use the 3/16" shims under the edges of the hatch to
keep from squeezing all the caulking out when you tighten the screws.
After the caulking is fully cured, come back and retorque the screws.
If the hatch ever starts leaking again, all you have to do is again
retighten the screws and this should stop the leak. This is because
you can continue to tighten the frame against the semi-soft caulking
which is really now a gasket.
Now, place shims under the bottom edge of the glass
from the exterior. We do not want the glass resting on the bottom
of the frame because if the frame moves, it will also move the glass,
so shim it up so the glass is approximately centered in the frame,
not touching on any side. Allow the bedding to set up overnight
before you go back and apply the final glazing to the exterior.
If there are snap-in exterior moldings, wait a day before putting
those back in so that you don't disturb the positioning.
After the bedding has cured, you can now trim the
excess on the interior, or finish with the exterior glazing. To
trim, hold the razon blade at an angle about 30 degrees off of vertical
and cut at this angle all the way around. Then finish up by trimming
the horizontal surface, separating the bedding from the glass just
up to the point of the vertical cut. Have a supply of blades because
the glass will dull them quickly and they will not cut cleanly when
dull.
If you do not have exterior moldings to install,
use your bedding to finish up the glazing. To get a nice smooth
surface, use a NEW chrome plated putty knife sprayed with silicone
to prevent sticking. Don't try to remove all the excess, just get
the glazing part smooth. You can trim the excess with a razor after
it sets, which is very easy to do.
Viola! You're finished.
The Result: What you have done here is to
create sort of a free-floating window pane. The soft bedding will
allow considerable movement without breaking the seal so that future
leakage will be eliminated, or at least greatly reduced. This method
works not only for windows, but for portholes and deck hatches as
well, or any place a more rigid frame is mounted to a flexing hull
or deck surface.
Note: Most windows have a two-part frame,
the outer frame which is the major part, and the inner which is
more or less just a trim bezel. Even so, that trim bezel probably
plays a major role in the sealing process, so the inner part needs
to be removed and rebedded as well. However, you don't need to shim
it when reinstalling. When drawing up the screws, don't pull them
real tight, just draw it up within about a 1/16" until the
bedding sets. Then go back and retorque the fasteners to make it
a little tighter.
Deck Hatches Usually leak because the deck
flexes somewhat, breaking the caulking seal. The remedy for this
- as long as the deck doesn't flex too much - is the same as for
the window glass described above. Again, the trick is to make the
bedding layer thick enough so that it can be torqued down like a
gasket. Pulling that hatch frame down tight was what created the
problem in the first place, so once again use shims on the preliminary
reinstallation. Then go back and retorque after the bedding cures.
Tinted Lexan against a black surface: This
is a combination that will never stop leaking in Florida or the
Gulf coast simply because the black absorbs too much heat from the
sun and the rate of expansion is too high to permit a seal. The
only solution is DON'T USE BLACK MATERIALS.
Related Article: Windows,
Windows, Those Leaking Windows
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How
to Repair Window Leaks
