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How does a keel cooler
work, and is there any special maintenance involved? M.L., via
e-mail
A keel cooler
is much like the radiator in your car. It extracts heat from engine coolant
via a network of piping and transfers it to the surrounding environment.
The difference is that in a car that environment is air, while on a boat
it’s sea water, and instead of a radiator, a boat has a series of
tubes attached to the outside of the hull. (On commercial vessels the
tubes are attached to the keel, where they won’t snag nets or pots,
but on pleasure vessels they can be most anywhere.) Keel coolers are usually
found on displacement-style vessels, where the added hydrodynamic drag
isn’t a concern.
Take a look at the diagram
to the right. It shows not just the location of the keel cooler (at the
bottom), but also the myriad pipes and valves between it and your engine.
There are advantages
and disadvantages to this system. A keel cooler is simpler, since it eliminates
through-hull fittings, strainers, hoses, and raw-water pumps, with their
notoriously problematic impellers. On the flip side, the exposed cooling
lines—even if keel-mounted—are subject to damage from underwater
objects and groundings and produce unwanted hydrodynamic drag on planing
hulls. Moreover, exterior corrosion can cause leaks, and accumulated fouling
can degrade the tube’s heat-exchanging capability.
What is the best
way to remove several drops of varnish from my fiberglass deck?
B.H., via e-mail
If your decks
are smooth, take a reasonably sharp putty knife and carefully pry the
hardened drops off. With rough or nonskid decks, fold a paper towel into
quarters, lay it on top of the varnish, and drip lacquer thinner onto
the towel. This should soften the varnish enough that you can remove it
with a ScotchBrite pad and some elbow grease.
I’ve ruined
several putty knives with accumulated buildup from paint stripping. Any
suggestions on a way to prevent this from happening in the future?
R.J., via e-mail
Before beginning
your job, coat both sides of your putty knife with a nonflavored, nonstick
cooking spray. Then, as you continue working, clean the knife off with
each pass and recoat the blade as necessary. You will find the buildup
is less likely to adhere to the blade than before.
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