Almost everything seems slightly overbuilt on the early Islanders. Thankfully the keel is no exception.
UPDATE: Details on the 'final' keel bolt fix in March 2021.
The 1972 Islander 36 has a lead keel attached with 1" x 8 studs with 1 - 1/2" nuts. It's hard to imagine a more robust installation. I've recently obtained the blueprints and want to drop the keel. Nothing is screaming at me as an safety issue ... but it's 48 years old! It appears there's a studded metal plate welded on a steel backbone encapsulated within the lead keel. Best case scenario is to back the nuts off (or use a nut cutter), drop the keel, inspect the studs, replace as needed, chase the threads on the solid bolts, clean and reseal the plate, then reattach.
The keel weighs 5,820 lbs and the tensile strength of each bolt is more than 20,000 lbs.
There is a single keel plate in the bilge. The studs ensure the bolts don't turn when tightening the nuts. Large washers and lock washers fit on the studs before the nuts. The fiberglass join is bedded and attached to the lead keel. The downside of this configuration is the nuts will lose their galvanized zinc coating and accumulate surface rust over time. My bilge has been treated and painted several times over the years but when I inspected this year, I found the nuts were in good shape, but were rusty on the surface.
I'm lucky to have Port Townsend Shipwrites Coop nearby. They are a full service shop and they happened to have just completed an identical Islander 36 lead keel refit. See photo above where they dropped the keel, cleaned the threads and reattached. I contacted Brad Seamans of PT Shipwrites who said:
That Islander had the same exact issue with badly corroded nuts. We dropped the keel intending to send it off to Toronto where a company called, Mars (I believe), melts the bolts out and installs new bolts. We discovered that the bolts were actually in good condition and therefore we just chased the threads, reattached the keel, and added new nuts. Anders told me that there are 10 total. If you only count 9, there is one hidden under the mast step which takes a fair amount of work to get to. Anders suggested that you start squirting the nuts down with Aerokroil, now. If you aren't familiar with this, it's in an orange can and it's a penetrating oil. I'll send you another email later today with all the info. It is a time consuming process.
Given this, I decided to remove as much of the surface rust I could and see if there was any reason for concern. The rust chipped off cleanly and relatively easily. However the tight space was a challenge to get the wire wheel equally around each bolt. I did not pull the mast to access the keel bolt there, but will have a good look at that in the next year or two.
Here's what the nuts looked like when I was done.
After chipping away the rust and wire brushing, the bolts looked the same or better than the one recently pulled at PT Shipwrites Coop (top photo). After conferring and sharing images with Brad, we decided to not drop the keel at this point. I then painted the base plate with Rustoleum and coated the nuts with Lanocoat This should last several years before another 'bilge party' is required.
I learned a fair amount about surface rust. Most surface rust happens when paint breaks down. In my case, the bilge can be a nasty place where all spilled liquids eventually accumlate. Water enters the bilge from the cooler drain, the drain in the floor in the head, and the stuffing box.
Structurally, surface rust is generally not a problem, depending on the metal's thickness and alloy composition. It's best to correct surface rust as soon as you see it. If left untreated it will become an issue over time. My bilge has been treated and painted several times over the years.
Some good rust destroyers:
