PS Advisor May 1, 2002 Issue

PS Advisor: 05/01/02

Pitted Iron Keel
I am a new owner of a 1980s-era Beneteau First 32 with a cast iron (I believe) fin keel that is showing lots of rust spots bleeding through the bottom paint. There is one especially hard-hit section about 2" square that is corroded to a depth of about an 1/8" to a 1/4". The pitting is not up near the hull but about halfway down the keel.

First, what's the best way to repair the deeply pitted section, and second, how should we prepare the iron keel to keep the damage from recurring?

She's a sweet boat, fast and points well. This rust problem is the only real concern.

-Robert Ferraro
New York City


As you've discovered, an iron keel rusts quickly when its protective coatings break down. Each marine paint company has special products for metal keels. Here's the procedure for Interlux:

1. Degrease the surface with Fiberglass Solvent Wash 202 or Special Thinner 216.

2. Shot blast the keel or grind with a 36-grit wheel to remove all paint.

3. Immediately coat with Interprotect 2000E/2001E. If more than one hour has passed since blasting, coat with Viny-Lux Primewash 353/354 thinned 25% with Viny-Lux Solvent 355.

4. Fill cavities with Watertite YAV135 and sand fair.

5. Apply four coats of Interprotect 2000E/2001E.

It's a lot of work, but necessary, as the rust will only get worse. The treatment should last at least a few years. As with any paint job, the key to long-term success is preparation. Any dirt, grease, or other imperfections on the surface will inhibit bonding of the paint and be the source for future failure. If you nick the coating during a grounding, this, too, provides a path for water to make its way under the coatings and cause failure.

This illustrates the major trade-off between lead keels, which cost more initially, and cast iron ones, which are prone to problems like this.

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Mixing Different-Size Batteries
I'm planning to increase my battery capacity. I currently have two group 24 deep-cycle 12-volt batteries in parallel. I'd like to change one 12-volt to starting (bank #1) and add more batteries to the other to form a larger bank (bank #2).

I'd like to add to bank #2 one group 31 12-volt and two 6-volt batteries in series (this would maximize my battery capacity for the available storage space). Assuming that I use consistent battery types (e.g., all flooded or all gel, and all deep cycle) is there any reason why I can't arrange the four proposed batteries into bank #2, as described?

-Klaus Schaefer
Mississauga, Ontario


Mixing battery sizes of the same type is marginally acceptable. The three batteries (the two 6-volt batteries act as one) wired in parallel are essentially just one big battery. They will charge OK. And if the boat is used every day, their different self-discharge rates won't be a problem. But because their self-discharge characteristics will vary widely, when at rest they will discharge each other at a remarkably high rate. If the boat is left to rest for a couple of weeks or more, you'll likely have dead batteries. Battery isolators were invented to solve this problem, but these diodes lower voltage. You can work around this, but it starts to get complicated.

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The Lowenbrau Solution
Our big event, other than a few local fun races, is a three-week cruise. We usually head south. Because places to restock food are rare, we like to pack a load. We have a good-sized Tundra system. My problem is that my wife, who likes to eat well, loads the fridge/freezer so full that there's no space for my beer. I go only about three bottles a day, but I love it. So, I need cooling space. Got any ideas?

-Jack Wallace
Santa Barbara, California


This is indeed a dire problem. As you know, the ideal temperature for beer is in the rough, ballpark range of 48.27352 F. The high-brow solution is to avail yourself of a small thermoelectric cooler. These work on what's called the Peltier Effect and use very little 12-volt power. In an hour they'll drive the inside temp down 40 to 45 below ambient temperature, which is often a fine beer-drinking temperature. The last time we tested these coolers was in '96. Now you can get better ones for less at Wal-Mart.

The mid-brow solution is to take along a regular, small "For My Daily Beer Only" cooler. Decide (with your wife, of course) what you're going to eat for dinner each night, and stick the frozen food in with the beer mid-afternoon. A few hours later the beer will be chilly and the food defrosted.

The Lowenbrau solution is to put the beer in a net bag with an old galvanized cleat and dangle the lot about six feet under that cool Pacific water for about an hour. Cheers.

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