The Mystery of the Bulging Fin Keel

What could cause an Islander 28s keel to begin to bulge after 35-plus years?


Islander 28's fin keel

I was reading a Mailport letter in the December 2014 issue of Practical Sailor, and it led me to your May 27, 2014 blog regarding keel failure. We have a 1977 Islander 28 with a bolted-on fin keel that is creating a safety issue. I am confident I know what the proper repair is (remove the keel and re-secure it), but I am more wondering if youve ever seen anything like this. On the starboard side of the keel, below the keel joint, a square chunk of lead is bulging out of the keel side. Ive had a few surveyors take a look at it, and theyve never seen anything like it either. The keel bolts do not leak-at least water doesn’t come in. Thoughts?

Michelle Shrider,
CMM, General Manager
Washburn Marina
Islander 28
Washburn, Wisc.

It could be a case of steel keel bolts expanding, but like most domestic production boats of that era, the Islanders have lead ballast and 304-stainless-steel keel bolts. On most boats, these were held in place by a stainless plate that was embedded in the keel. During construction, the plate had to be heated so that the lead being poured did not cool too quickly around the keel-bolt weldment. Lead thats cooled too quickly will not become part of a uniform casting, and the crystallized boundary can easily shear, even separate from the casting. If this happens in the region where keel bolts are joined in a weldment, this can be a very structurally significant problem.

Try to find out which casting company (Mars or other) made the keel and how the bolts were embedded. If they used a stainless plate, were willing to bet it cooled too quickly or was never heated. Also, there looks to be a pretty good smack on the keel, and the resulting side load could have exacerbated the problem.

This can also happen when a J bolt is too close to the skin and a similar thermal reaction-where hot lead meets relatively cool stainless bolts-occurs.

We suggest digging into the area around the sheared lead to see whats going on. Even if the keel is removed, youll still want to see whats happening under the separating lead.

Practical Sailor has been independently testing and reporting on sailboats and sailing gear for more than 45 years. Supported entirely by subscribers, Practical Sailor accepts no advertising. Its independent tests are carried out by experienced sailors and marine industry professionals dedicated to providing objective evaluation and reporting about boats, gear, and the skills required to cross oceans. Practical Sailor is edited by Darrell Nicholson, a long-time liveaboard sailor and trans-Pacific cruiser who has been director of Belvoir Media Group's marine division since 2005. He holds a U.S. Coast Guard 100-ton Master license, has logged tens of thousands of miles in three oceans, and has skippered everything from pilot boats to day charter cats. His weekly blog Inside Practical Sailor offers an inside look at current research and gear tests at Practical Sailor, while his award-winning column,"Rhumb Lines," tracks boating trends and reflects upon the sailing life. He sails a Sparkman & Stephens-designed Yankee 30 out of St. Petersburg, Florida. You can reach him by email at