Rip Rap July 1, 2003 Issue

Willow's Not Weeping: An Update

In response to an editorial question:

No one thinks kindly of water that leaks down below into our supposedly dry sanctuaries. Nothing is more annoying than trying to sleep with water dripping on your head, wet charts and books, and spoiled food. On one Bermuda passage in a leaky wooden boat, we set up strings to direct deck drips away from our berths and into pots on the sole (like spiderwebs and dew). On another Bermuda passage, we had a water leak get into a food locker and expand all the pasta to twice its size. 

The Dow Corning 795 silicone building sealant is an inexpensive solution to porthole installations. Each tube costs under $6 and comes in a variety of colors.

Before setting off for Bermuda last summer in Willow, our 1980 Bristol 40 yawl, we made a major effort to stop the water leaks below from the ports and the keel-stepped mast. (See PS July 15, 2002.) Our 2,200-mile trip took us from Baltimore down the ICW to Wilmington, NC, over to Bermuda, up to Portsmouth, RI, and back to Baltimore. The trip gave us a great opportunity to test the water-tightness of our porthole caulk and the Spartite mast wedge. We had five days of gales with seas crashing on the boat, portholes under water, and rigging shaking in the wind. After our "shakedown" cruise, we're pleased to say that the porthole caulk and the Spartite mast wedge lived up to our expectations.

As we said in the July report, instead of painting the Spartite mast wedge, we covered it with a Sunbrella® mast boot that we had previously used. Spartite is affected by UV, so either it needs to be painted or covered with a mast boot. Also, the manufacturer recommends using a non-silicone caulk for sealing the edge between the mast collar and the Spartite wedge. We decided not to put caulk in the edge to see how much water we would get below on the trip. Also, if we did get water, we could easily add caulk while on our trip.

To our surprise, despite water everywhere, none came down the mast into the cabin. We know we had a lot of water on top of the cabin because the two cabin hatches both leaked badly (another project).

The Sunbrella mast boot wasn't waterproof, but it probably reduced the chances of water spraying into the edge (or gap) between the mast collar and the Spartite wedge. Even after three feet of melting snow sitting on the boat this winter, we still have not had any leaks at the mast collar.

Before we poured the Spartite into the space between the mast collar and the mast, we put a small bend in the mast to preload it. We did this with the thought that it would help stop the mast pumping that we've experienced in other heavy weather. We were very pleased that with the Spartite wedge, the mast pumping was almost non-existent.

We have not yet taken the mast out of the boat, so we can't comment on the ease of removing the Spartite wedge from the mast collar. We're hoping that the lack of water leaking isn't an indication that the plug has become a permanent part of the mast collar.

One item we were concerned with, which turned out not to be a problem, was the clay left behind from the dam we built. Before pouring Spartite into the gap, one first needs to build a "floor" in the gap to stop the Spartite liquid running down between the mast partners. We had been advised by the manufacturer to remove all the clay after the Spartite cured. Their concern was that the clay might get soft in the summer heat and that it would dribble out of the partners. We had problems removing all the clay, and were pleased that the remaining clay stayed where it was.

So far, Spartite has met all of our expectations.

Dow Corning® 795 Silicone Building Sealant
How boring—there's nothing to report regarding the 795 silicone sealant, except that it worked. Not a leak or drip. No gooey or gummy residue on the porthole Plexiglas®, like other silicone products can leave, nor is the 795 sealant causing any fogging or discoloration around the edges of the Plexiglas. The sealant is still flexible, with no chalking, color changes, cracks, or tears, with many miles under the sun and, again, three feet of snow piled against the cabin.

Watching the ocean slamming into the portholes from down in the cabin, we were glad for the additional rigidity built into the cabin sides, plus the holding power of the sealant.

However, as we're very aware, one year doesn't test the longevity of a sealant. Only many more years of sun, salt, and water exposure will show.

We're heading off now to go sail more miles to test the longevity...


Dow Corning Corporation, 517/496-6000,
TCC Spartite LLC, 877/772-7848,

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