More marine myths:
Bronze is somehow ‘corrosion proof” in seawater. As I
have explained elsewhere in the forum, bronze isn’t just bronze. It can be a
casting of a number of different metals, each with a different nobility and
those different nobilities cause the metal itself to generate galvanic
corrosion. Bronze often has high levels of zinc, and that fact alone causes it
to self destruct in an electrolyte of seawater. There is no numerical rating
system for bronze, and in fact bronze is called by so many different names it
is questionable what it contains (need I mention China-made pet food and
drywall?). So buyer and sailor beware.
Fiberglass has to “breathe”. I suppose when fiberglass develops blisters
it is because its little lungs are filling up with water, right? No fiberglass
doesn’t breathe, and can and should be encapsulated in epoxy as a permanent
means of stability. Fiberglass on both old and new boats is often laid up too
dry and literally contains un-wetted out fiberglass cloth in its layups, which
can attract and hold moisture and of course does nothing for strength.
Fiberglass can also contain voids that can contribute to porosity. Finally,
some boats were and still are built using a chopper gun for some areas of the
structure (Halberg Rassy’s for instance use chopper guns to build the entire
hull). Fiberglass molded with a chopper gun makes the weakest hulls of all and
can definitely use the epoxy as a means of fortification.
The best substrate for a primer / LPU finish on decks and
hulls is two or more layers of unthickened epoxy, sanded smooth. Likewise, the
best finish for the interior of your hull is unthickened epoxy colored with a
white or gray pigment. The coating completely seals and strengthens the hull,
making a permanent painted finish to the bilge and lockers of your boat, yet
you can bond to it with epoxy and fiberglass cloth at any time without having
to sand off paint.
Stainless steel will always suffer from crevice corrosion
in a sea water environment. Related myths include:
steel always rusts—it just stains less (get it?) than mild steel.
steel turnbuckles will always suffer from galling and failure.
stainless steel fasteners will always gall.
steel has to “breathe” (can’t forget about its tiny lungs).
Crevice corrosion in 302 and 304 stainless steel is caused
by a lack of oxygen in stagnant salt water. In that environment, an ionic
transfer takes place and the results can cause crevices to form in the steel, eventually
breaking under load. 316 stainless is much less susceptible to crevice
corrosion The bottom line is, underwater metal unless it is Monel needs to be
inspected like everything on your boat.
Staining. Yes stainless steel will stain, but it does not
rust and the staining can be instaly removed with a little Comet or similar
Turnbuckles. Like every kind of marine gear there are
turnbuckles and then there are turnbuckles. There is a lot of crap made in now—regardless
of whether it is bronze or stainless I would not risk my rig with it. There are
high quality stainless turnbuckles: I have them on my boat and they don’t gall
or corrode or deteriorate. Galling has a lot to do with how the threads are cut
and if friction is added, heat is added, galling can occur. I have had it start
to occur treading stainless bolts into holes tapped in epoxy. The bottom line
is to use quality stainless, fasteners and turnbuckles and you won’t have a
problem with galling.
Fiberglass hulls have to flex and bend or they will
shatter. Boat owners espouse this who
own boats that are built with a thin layup schedule, or are structurally just
not stiff. However, fiberglass boats can and should be just as stout and
inflexible as wood, alumimum or steel boats. Anyone who says fiberglass boats
show flex has never sailed a Westsail 32, a Morris Yacht, a Bristol Yacht, a
Hinckley Yacht, a Pacific Seacraft, a Southern Cross, a Hans Christian, a
Shannon Yacht, an Ocean Cruising Yacht, a Cherubini, a Camper and Nicholson, a
Sam Morse BCC, a Little Harbor, a Swan …the list goes on and on. All extremely
stiff boats that do not flex, bend, twist, bow, or shatter.
Epoxy is not waterproof. Blame Larry Pardy for this
one. For some reason he has a hard-on about epoxy—I think because he had some
glue failures in the cabin sides of his boat and blamed the glue instead of
user error. Epoxy is waterproof for all intents and purposes if used correctly
and the surface is prepared correctly.
That means the epoxy must be mixed correctly and completely.
It means it has to be used at full strength without thinning
it with some chemical and it has to be used in the proper temperature range.
It means it cannot be applied over paint, or “red lead” or
any other coating that prevents it from saturating the wood fibers.
It means you have to wipe the surfaces first with acetone to
remove any oils or impurities.
It means planks have to be clamped according to the Gudgeon
It means you have to apply enough coats of epoxy—West
Systems recommends a minimum of two. I stick to a minimum of three. And it has to be protected from UV, either with paint or with a clear coating that
contains UV filters.
It means if you are using epoxy on brightwork, it should
surround the wood encapsulating it so there are no edges of epoxy where bare
wood can be exposed to moisture.