When Keel, Stub Part Ways

Seam-ingly small problem could be major one.


I have a 1980 Albin Cumulous with an iron keel. The keel has recently been cleaned, primed, and painted, and is holding up well. However, the seam between the keel and the keel stub is opening up. The keel bolts are not leaking. The last time this seam opened, I squeezed in some 3M 101 polysulfide sealant and that seemed to work. Is there a better sealant that I should be using?

Tom Penny
Albin Cumulous
Brooklyn, N.Y.

Often seemingly minor problems on boats are indicators of more serious problems that, if not addressed early, will lead to bigger headaches and more expensive repairs. Gelcoat cracking on the deck, which can be either a harmless cosmetic problem or a symptom of wet core or some other structural failure, is a classic example of this scenario.

Your keel seam falls into the same category. It might easily be resolved with some underwater sealant, or it could be a symptom of a far more serious problem. Without dropping and inspecting the keel, you cannot know for sure. Given that this iron keel is 28 years old, the likelihood of serious corrosion between the stub and the ballast is significant. The keel bolts themselves may also be corroded. If your keel has never been dropped and inspected before, a close inspection is long overdue, particularly if you plan to take the boat offshore or beyond coastal waters.

Even if all is well with your keel assembly, it is unlikely that you will permanently seal your keel seam without some thorough prep work at the joint. Certainly, you may be able to fill the seam with a good adhesive sealant like you did before, but it will likely open again over time and you will not solve any larger hidden problems.

Once your inspection and any repairs are taken care of, achieving a proper seal will ensure this problem doesn’t crop up again. To get a good seal, both the keel stub and ballast must fit cleanly together. In other words, the mating surfaces should be uniform and flush. Typically, the joint would require a minimum of sealant, most of which squeezes out of the joint upon tightening the keel bolts. If there was a poor fit to start with, more sealant isn’t the answer.

The ballast needs to be removed, the surfaces cleaned, and a high-density epoxy filler will be required to fill the voids.

Once your keel stub is relatively smooth and free of voids, you can use it to “mold” a clean mating surface in the keel. To do this, you need a sheet of heavy polyethylene plastic that will fit like a gasket between the keel stub and keel and keep the two from bonding. For extra protection, you should cover both sides of the “gasket” in a release agent. You must also make sure the keel bolts are liberally coated and packed in grease. A failure to ensure a clean release here can cause some significant problems. You then fill the voids in the mating surface of the ballast keel with putty or high-density Chockfast (www.chockfa

st.com). The hull and its plastic gasket is then lowered back onto the epoxy-filled ballast (with the plastic in between the hull and putty-coated keel), and the excess epoxy squeezes out evenly, developing a flush fit. The hull is again lifted, and the epoxy and grease residue are thoroughly cleaned. Finally, the hull/ballast joint is bedded with a polysulfide or polyurethane adhesive meant for underwater service. The parts are mated and lightly bolted up. Dont make the final torque adjustments until the sealant has fully cured.

Ralph Naranjo is a Practical Sailor contributing editor whose specialty is safety and seamanship. During his 10-year stint as the Vanderstar Chair at the U.S. Naval Academy, he augmented safety and seamanship training and played a key role in the development of the Navy’s 40-foot new sail training sloops. His sailing background includes a five-year family voyage around the world and the management of a full service boatyard. He and his wife Lenore have made two other lengthy cruises aboard Wind Shadow, a 41-foot sloop the Naranjos have owned for over three decades. During the past 15 years, he has moderated US Sailing Safety at Sea seminars across the country, and now is an adjunct lecturer at the Annapolis School of Seamanship. His newly developed courses on weather routing, seamanship, and celestial navigation are among the most popular in the school’s lineup. He is the author of Wind Shadow West, an inspiring account of the family’s five-year voyage, and The Art of Seamanship: Evolving Skills, Exploring Oceans, and Handling Wind, Waves, and Weather, a comprehensive textbook aimed at the advanced cruising sailor. For information about his virtual or in person seminars on a range of topics contact the editor at practicalsailor@belvoir.com.