Tropics tough on rig fittings

I read Dick de Grasse’s recent report on outside boat storage (Storing a boat in the tropics Issue 127, Jan./Feb. 2003) with considerable interest. For the last 11 years, we have sailed our Cape Dory 22, Searcher, out of Nevis in the Leeward Islands, where we live for about nine months each year. Then we haul the boat (over the beach with a backhoe) and join the snowbirds heading north for the summer.

Unfortunately, the article contains what my experience has shown to be a serious error as well as several important omissions. Although the warm, clear, tropical water and brilliant sunshine is far more benign to humans than the cold, gray water and climate of New England, it is far more brutal to materials, particularly stainless steel and rubber.

Without going into the metallurgy, stainless steel of the types commonly used for marine hardware is subject to intergranular attack, stress corrosion cracking and crevice corrosion — all of which can cause catastrophic failure. The nature and the velocity of the attack is a function of the chemistry of the material, the manufacturing history of the part (particularly cold work and thermal treatments), the stress level (both applied and residual), and the service environment and temperature. One of the worst environments is warm water rich in chlorides: tropical seawater. A chemist’s rule of thumb is that for every 10° increase in temperature, the rate of a reaction doubles. Therefore a Type 304 stainless-steel clevis pin, toggle or turnbuckle that could last 20 years in New England or the Pacific Northwest, might not last five in the Caribbean.

One sparkling day last year, I was beating out of the strait between St. Kitts and Nevis into a Force 5 trade wind. The boat was under precisely the right sail for the conditions, double-reefed main and the heavy No. 3, and was going beautifully. Then I noticed a discrepancy in the shroud count. Searcher is supposed to have three on each side, but there were four on the leeward side and only two to weather. A clevis pin that had appeared fine when installed three months before had disintegrated. Yet, the cotter pin holding it was still in new condition. Fortunately, it was on one of the lowers. A couple years ago, a similarly corroded toggle was found when the rig was inspected after haulout. It was made by one of the largest and most reputable manufacturers of marine hardware and stamped with its logo. In both cases, inspection of all the similar hardware found nothing amiss. In my years of sailing down here, I have also found cracks in the swage ends of standing rigging and in the adjusting screws of lifeline terminals. Searcher’s chainplates and turnbuckles are bronze, but even these get looked at closely. I don’t recall ever encountering such problems in a lifetime of New England sailing. I’m sorry, but I find Mr. de Grasse’s practice of leaving the rig standing under tension over the summer and then sailing to “remote areas with few shore-side facilities” dangerous.

When a boat is hauled in the tropics, the rig should be removed, cleaned and minutely inspected, and so should the lifelines. Turnbuckles and toggles should be disassembled, cleaned with paint thinner and a tooth brush, and inspected either with a magnifying glass or with dye penetrant. Before reassembly, the threads and sliding surfaces should be lubricated with a thin film of anhydrous lanolin. All the swage terminals should be inspected for stress corrosion cracks. Anything that looks at all doubtful should be replaced. Clevis pins are a problem. Some may last for years, but others may turn to dust in a matter of months. If any clevis pin shows more than the most superficial discoloration or rust, replace it.

If the boat has stainless-steel chainplates, and particularly if the cover plates have been leaking, they must be inspected annually. If the boat has stainless turnbuckles, and particularly if they are of the closed-body type, they should be replaced. These parts live at the deck edge, where the hot tropical sun meets the warm, chloride-rich sea. It is here that stainless-steel fittings and the rig they support are most at risk. But those higher on the mast should also be inspected because warm salt spray flying to the spreaders is not at all uncommon. It’s one of the attractions of tropical sailing. None of these things can be properly inspected without pulling the rig.

The primary function of a boat is to keep the water out, and the only sure way to get rid of tropical mildew, once it is established, is with a flamethrower. Small deck leaks that lead to mildew when the boat is closed up over the summer should not be tolerated. Rubber fittings and gaskets do not last in the tropics. Don’t ask me why, but a rubber band holding the chart-table pencils in a bundle that would last for years on Puget Sound, turns to goo in a month or two in the Caribbean. For this reason, hatch and port gaskets should be cleaned, inspected and lightly coated with silicon grease at haulout. Even with proper care, they will probably need to be replaced every few years.

Down here, where so much of the sailing is done reefed down under boisterous winter trade-wind conditions, deck fittings and tracks are subjected to much higher prolonged loads than in the light and variable winds during summer in northern waters. They must be checked for any leakage during the spring wash down and rebedded as necessary. Searcher is 22 years old and, after standing in my backyard for three months, has dusty bilges. If she doesn’t, I find out why and fix it.

Another omission in the article was mention of seacocks. Because everything grows more quickly in the tropics, these must be checked frequently to assure that something has not moved in and jammed them. Because fixing them with the boat in the water is impossible, and travel lifts are few and far between, they should be disassembled, cleaned and greased during the annual haulout.

I do agree with Mr. de Grasse that boat covers are useless down here. The tropical UVs devour them. I always clean and wax Searcher’s gelcoat at haulout. It makes the fall cleanup much easier.

Jule Miller is a retired welding engineer who worked for 30 years in the materials laboratories of aerospace companies. He lives on Nevis in the Leeward Islands, where he and his wife Heide sail their Cape Dory 22, Searcher.

Dick de Grasse responds:

Jule Miller is clearly an expert in metallurgy, which I am not. He is right, the closer you get to the equator, the more favorable conditions are for stainless-steel failures. The rig must be inspected every season and more often if possible. Miller rightly suggests unstepping the mast every year to facilitate rig inspection. However, unstepping the mast on a 22-foot Cape Dory is much simpler than on the typical larger cruising boat; most of us settle for deck-level and up-the-mast inspections.

Rubber does go bad in the tropics, and all seacocks should be lubricated when the boat is put away. We plug them with screen to prevent mud wasps and other critters from entering. Mildew is a problem, but Miller’s flamethrower is more than I dare to try. n

By Ocean Navigator