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By Frank Lanier Latitudes and Attitudes (2004)
Most boaters get the big picture concerning boats and water – keep the water on the outside of the hull and you’ll have a lot more fun. It’s easy to imagine the effects generated by a failed through-hull or ruptured hose, however there’s a more insidious side of water most folks don’t even think about. It probably causes more boat damage every year than sinkings, groundings, fires, and alien abductions combined, although you may feel as though you’ve been anally-probed from a financial standpoint as repairs are usually expensive, sometimes exceeding the value of the boat itself. And here’s the scary part – if you’re a typical boater, chances are it’s happening on your vessel at this very moment, unnoticed until the damage is already done. The cause of this lurking horror? Water intrusion into cored decking and superstructures due to poorly bedded or improperly mounted deck hardware. Yes friends, we are our own worst enemy when
it
comes to drilling, screwing, and fastening things to our boats – and
we’re not
alone. A lot of builders, dealers, and
other professional folks out there just can’t seem to get their
proverbial
feces in one sock either when it comes to drilling holes and screwing
things
into your boat, a situation exacerbated by the fact the problem often
doesn’t
show up until years later. The first step in understanding the problem
is
finding out what the term “cored” means and why water entry is such a
problem. The majority of today’s boat
decks (along with a lot of superstructures) are cored, typically with
materials
such as end grain balsa, plywood, or maybe one of the more high-tech
foam
variations. Cored construction simply
means you’ve got an inner and outer skin of fiberglass with one of the
above
materials bonded / sandwiched between them. Gone are the days of all solid fiberglass
deck and
superstructure construction. Capitalizing
on the strength of the “I” beam effect, cored
construction
is both lighter, stronger, and provides better heat and noise
insulation than
solid fiberglass. It’s also cheaper to
build, which is often the real driving force from a manufacturing
standpoint. There are real benefits to
cored construction, so long as builders respect its limitations and
utilize a
judicious combination of both cored and solid fiberglass construction
in their
vessels rather than going hog-wild and coring everything in sight just
to save
a few dollars. What this means for the average Joe is that
unlike
the old days of solid fiberglass construction (when you could drill,
mount, and
be done with it) chances are you’ll probably be drilling through cored
panels
and it’s going to take a little more time to do it right.
The numero uno thing concerning cored
construction is maintaining waterproof integrity in order to prevent
moisture
from entering the core and causing trouble, particularly with balsa or
plywood
– wet wood coring can rot, allowing the cored deck to separate,
drastically
reducing structural integrity. Long
term water exposure causes problems with foam-cored decks as well (core
separation and even disintegration in some cases) so don’t think you’re
totally
immune to the problem just because you happen to have foam coring. Anything and everything penetrating the core
has to
be properly mounted and bedded to prevent water entry, and I mean
EVERYTHING –
antenna mounts, windless foot switches, stanchion mounts and yes,
especially
those innocent looking canvas snap buttons you’ve got screwed allover
the cabin
top deck and cockpit. Holes left after
removing hardware are bad too, particularly when whoever removed them
just gooped
a dab of sealant over it and called it good. Many
boaters fail to realize that drilling a hole into
your boat’s deck
or cabin top is exactly the same as drilling a hole in the roof of a
house. Anytime you screw or drill through a cored
panel,
the first rule is properly sealing the core against moisture entry. There are a number of ways to do this, but
the best one is to avoid breaching the core material in the first place. In a perfect world, your boat’s manufacturer
has anticipated where all deck penetrations are necessary (stanchion
bases,
cleats, etc) and has “de-cored” these areas by reverting to solid
fiberglass,
allowing you to mount hardware without drilling into the core. But, in the case of new installations
(particularly if you’re lucks like mine) your chances are slim-to-none
that any
of these areas will coincide with whatever aftermarket doo-dad you want
to
mount, meaning you’re going to have to do it the hard way.
The good new is the hard way is fairly easy,
as long as you have access to the underside of the deck where you’re
doing the
mounting. What you’re going to do is a little de-coring
of
your own. The easiest way to remove
coring is with a hole saw and a little caution. Let’s
say you want to mount a new cleat on your foredeck, but the
entire area is cored. First step is
marking and drilling the appropriate sized bolt holes.
Then, take a 2 inch hole saw (or larger,
depending on the size of your backing washers) and remove the coring
from the
underside of the deck where each bolt is to be installed, being careful
NOT to
drill through or damage the upper layer of fiberglass (you also have
the option
of removing a single section of coring large enough to encompass both
bolts). I find it works best to drill
almost through the coring, but leave the last ¼” or so to be removed by
hand
(to avoid any chance of damaging that outer fiberglass layer).
Once the cutout and coring is
removed, seal the exposed edges of the coring in the holes with
thickened epoxy
paste. Now all you have to do is mount
the cleat using properly sized backing washers and a good bedding
compound
(under both cleat and washers) and Whaa-la! You’ve
got a properly mounted cleat that won’t leak and
has no chance of
letting water into the core. I like the above method of dealing with
mounting
holes in cored panels, but it’s not the only way to address the problem. An excellent reference for this and just
about any other type of fiberglass repair or maintenance issue is
“Fiberglass
Boat Repair And Maintenance” published by Gougeon Brothers, Inc. (517) 684-7286. It’s
a good how to booklet and well worth space on any vessel’s
bookshelf. “But Frank,” I hear you say, “This seems like
a lot
of extra work. Why can’t we just drill,
goop it up good, and mount it through the core?” The
problem is cored construction isn’t strong enough to handle
point loading – tightening up the mounting bolts invariably crushes the
core,
causing the part to loosen and leak. Another worthwhile project is inspecting and
sealing
any exposed coring left over from previous installations.
Cutouts for Dorado vents, hatches, chain
plates, hawseholes, port lights, etc should be inspected to insure they
were
properly sealed during the installation. It’s also a good idea to through bolt the
hardware
you’re mounting if at all possible. Screws
are a horrible way to fasten anything to fiberglass, a brittle material
that
doesn’t hold screws well to begin with, particularly if the fastener
itself
will be under a load (canvas snaps being a good example).
Anything under pressure and relying on
screws for mounting will eventually work itself loose or get ripped out. Squirting sealant under the screw head
doesn’t help much either; as the working of the screw also breaks the
sealant
bond, allowing water to enter. In
instances where screws just have to be used, some folks have had
tolerable
success by drilling the screw hole larger than needed, digging out the
core
past the edges of the hole, and filling the hole with thickened epoxy
paste. This allows you to then drill
the screw pilot hole into solid epoxy, thus eliminating the chance of
water
migrating into the core. That being
said, the best solution remains using through bolts and adequately
sized
backing plates or washers on all hardware whenever possible,
particularly those
under load. What about existing hardware?
When’s the last time you pulled, inspected,
and re-bedded your cleats, chain plates, lifeline stanchions and the
like? I’ll let you in on a little know
fact – if
you haven’t re-bedded in the last 7 years or so, that old caulking
doesn’t owe
you anything. No one likes to re-bed
hardware – it’s a pain, isn’t very glamorous, and doesn’t physically
add to the
appearance of your vessel like other projects (that new dodger for
example). It can, however, prevent some
massive repair
bills. At a minimum, all deck hardware
should be pulled, the deck inspected for damage, and re-bedded at least
every 7
to 10 years (more frequently if the situation calls for it). The other thing to remember is that gooping
sealant around the outside edges of a chain plate or other piece of
deck
hardware in efforts to stop a leak or do a “quickie” re-bed job is like
throwing sawdust against a waterfall – it has to be pulled and
re-bedded or
you’re just wasting your time. Finally, use a good marine grade caulking to
bed
whatever it is you’re mounting, and use plenty of it.
The stuff you get at the hardware store just doesn’t hold
up as
well, meaning you’ll not only have to re-bed sooner, but you’ll most
likely be
dealing with leaks in the meantime. There’s
a mind boggling array of sealants on the market
and what you
finally use is a matter of personal choice, however knowing the 4 basic
types
will help in choosing one that meets your particular needs. Polysulfides are one of the most versatile of
the
lot and can be used to bed most anything – except plastic items
(deadlights,
port light frames, etc). The solvents
in it cause polycarbonate, acrylic, ABS and PVC to become brittle and
crack,
however it can be used with fittings constructed of epoxy, Delrin, or
nylon. When used as a bedding compound,
polysulfides are flexible enough to allow for movement caused by stress
and
temperature changes, yet strong enough to maintain a tenacious bond
between the
two surfaces. It adheres well to oily
woods (like teak) and stands up well to the harsh cleaners typically
used on
them. It can also be sanded once cured
and readily accepts paint. Polyurethane is kind of like the Superglue®
of
caulking and is as much adhesive as sealant. Fittings
and such bedded with polyurethane typically can’t
be removed
without damage to either hardware or vessel (or both).
Polyurethane is a good choice for keel
joints, hull-to-deck joints, and through-hulls, however there are
differing
opinions concerning their use to bed deck hardware.
The fact that 3M 5200 is gooey, sticks to everything, and
forms
such a strong bond is exactly why it should be used according to some.
Those
against argue that because the fitting can’t be removed without damage
come
re-bedding time, polysulfides are a better choice, while the other side
counters this just means you can go longer without having to re-bed. Weigh the pros and cons and choose
what’s
best for you, however keep in mind that polyurethane can’t be used on
plastic
either and can be damaged by teak cleaners, meaning they shouldn’t be
used to
bed teak rails or decks. Next up is silicone, the only one of the
three major
types that can be used to safely bed plastics. It’s
also excellent for bedding dissimilar metals due to
its insulating
qualities, such as stainless steel and aluminum. Silicone
is best viewed as a gasket material rather than a
sealant however, meaning it works best between two items held together under pressure.
Because it relies on compression rather than
adhesion, it’s a poor choice for bedding deck hardware. The final caulking category would
by hybrids such
as Life Seal, a silicone / polyurethane blend produced by BoatLife
especially
for use on fiberglass. According to the
manufacturer, it’s a “fast-curing, low
odor, high
adhesion, non-sagging, non-corrosive, non-yellowing formula” that can
be used
above and below the waterline. No matter what your boating philosophy a common sense approach to drilling and cutting into your cored deck will go a long way towards protecting your investment. A proactive maintenance schedule concerning pulling and re-bedding of deck hardware is critical as well, so when you mount and screw, don’t forget to spread the goo.
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