PS Advisor: 07/01/02
Bronze vs. Plastic Seacocks
As a long-time subscriber, I have often read your advice column. Now I could use some. I am replacing through-hull fittings on my Seaward 24 because I am replacing the head.The original fittings were plastic with hose barbs.
My boatyard suggested using bronze through-hulls and bronze seacocks. I do not have a bonding system, internal engine, or zincs, and I am concerned about corrosion of the bronze. The yard assures me that this is not a problem.
I am leaning towards using plastic fittings with Marelon seacocks because of corrosion, although I know about the durability issues. Would bronze fittings corrode without bonding or protective zincs?
Your yard is right—high-quality bronze through-hulls and seacocks don't present much of a corrosion problem, although they're not totally immune the way Marelon fittings are. In your situation, with an unbonded, trailerable boat, galvanic corrosion would be quite unlikely. If you leave your boat in the water all the time at a marina, though, you might want to connect a zinc "fish" to your rudderstock and dangle it overboard in case of stray current in the water.
Either bronze or Marelon is acceptable for use below the waterline (no cheap plastic, no gate valves). The bronze may be somewhat sturdier and resistant to breakage inside the boat, but may also be more likely to get stuck in place if left alone. Marelon is pretty sturdy stuff too, though, and should prove resilient for years without any special maintenance. It's not the same as the cheesy plastic fittings we've all seen degrade.
Any seacock should be cleaned and re-greased each season before going into the water, and during the season it should be opened and closed regularly, not only to keep it working, but to relieve pressure on hoses and fittings inside the boat. (Makers of washing machines also urge homeowners to shut the hot- and cold-water valves after running the washer. Not many of us do that But then, we're not worried about our houses sinking.)
Many boatowners insist that head seacocks be closed any time they're not in use. Some even make a habit of opening and closing the raw-water seacock for the engine as necessary. (This is a bad item to forget on your checklist when starting up.)
So there's no single answer here—you can take your yard's advice or follow you gut. Hard to go wrong in this case.
Dark Paint Down South
In your September 2001 issue yousaid to "go for it," when a reader asked about navy blue topsides. You mentioned three different disadvantages (deteriorates sooner, hotter inside the cabin, shows dings and salt stains) but nothing more serious.
I have since heard from several other sources that if one is planning to sail in the tropics, a dark hull is a very bad idea; that structural damage can occur because of the absorption of heat. I'm planning to repaint my Crealock 34 soon and am planning to sail south to the tropics. I would regret having to lose the dark blue hull, but would definitely paint her a lighter color if the warnings are true. Can you advise?
It's true that if you leave a dark-hulled boat with the hatches dogged down tight in the Caribbean sun, it will develop a great deal of heat in the cabin.
We vaguely recall a rumor about poorly installed bulkheads or cabinetry separating from the hull because of cabin heat. We won't say it can't happen, but there's certainly no epidemic out there. We'd be more worried about heat-sensitive things in the cabin like compressed gases or dainty electronics or M&Ms. Again, this is if you leave a boat alone with little ventilation, which is never a good idea anywhere.
We sent a note down to Dave Pugsley, marine director at the Bitter End Yacht Club in Virgin Gorda. Here's what he sent back:
"To my knowledge there have not been any problems with dark-hulled boats in this area. We have a Hinckley that we take care of here, and she's black. No problem.
"I would be more worried about applying the paint properly. If not done right, the paint can lift in the heat. (By the way, Awlgrip works fine in the hot sun.)
"As far as the idea of interior woodwork cracking and shrinking because of the heat, that doesn't seem to be a problem here, maybe because we're in the tropics and the air is very moist.
"The other side of this is that a dark hull does absorb the sun's heat, which heats up the interior faster. It will also show scratches and salt deposits more than a light color."