For a voyaging yacht, the keel attachment must (like Cesar's wife) be beyond doubt. The consequences of the hull and your keel going there separate ways is potentially in the realm of the unthinkable for those involved. If it's just playing in a few fjords or local waters... well then you may be able to take a few risks. Me... I like to be SURE, very SURE!

I bet the methods that all of you have described above will hold your keels in place forever.  Personally I would not be so concerned about the strength of the putty or glue between the keel and hull. After all, most keels are primarily held in place with bolts. Some shear strength of the glue would be welcome when running aground, but apart from that, its main purpose is in my view to keep the boat from leaking and the bolts from rusting.

My last boat, Johanna (grp with cast iron keel) was never completely tight when I had her. When the new owner this summer ran her onto a rock at speed, the leak became annoying (about 1 – 2litre a day), so she was slipped. The joint line between keel and hull was then carefully sanded down and a string of good polyurethane putty was added. This fix has proven to be very good as Johanna’s bilge is now dust dry for the first time.

If I were to bolt on a keel to a grp or wooden boat, I guess I would just use a half-strong putty  (butyl rubber?) or a rubber gasket in between. Then I would, as with Johanna, add that final string of high-quality polyurethane putty/glue along the joint line. This combination would be strong and watertight enough and still let me remove the keel without too much trouble (..I write this with this drawing in Annie’s first book, “Voyaging on a small income” in mind.).

Cheers, Arne

Annie I have no criticism of what has obviously worked for you, however I would argue that it is a waste to use a hard epoxy rated at ten or so times the strength of the wood it is gluing to. A somewhat softer and more resilient adhesive can still have twice the strength of the wood it is gluing and have a small amount of resilience to absorb shock and slight deformation that can occur in any hull. When I was working for the wooden Boat Center in Marina Del Rey, California, we did some tests on the high strength epoxies such as West, and the lower strength ones such as the Shell Epon 3 with a Versamid 140 hardener. We put the blade of a putty knife into a small container of mixed epoxy, waited for it to harden, peeled the container off and attacked them with a hammer. The high strength epoxies shattered at the first blow but the ones with the Versamid hardener just would not break they just slowly deformed as you continued to hammer on them. We had one set of samples at the Long Beach  boat show and the Versamid hardener sample survived the ten days of the show being hammered on every day, it ended up looking very battered but was still adhered to the putty knife and largely intact. I know which one I would want joining my keel to the hull.

We also did a number of experiments with additives and found that when gluing wood the phenolic microballoons weathered much better than the harder fillers. The slight resilience prevented cracking when the wood moved with changes in moisture content. In strength tests the epoxy mixed with microballoons was still stronger than the wood it was gluing

Hi, having installed the new keel on Arcadian I feel that I can offer a bit of advice regarding this issue. Firstly epoxy  with a high strength filler can be brittle and much stronger than the wood you are attaching to, so my advice is to use a low strength filler such as phenolic microspheres. These are slightly resilient and allow a very slight amount of movement without cracking. I used a mixture of sawdust and microspheres when attaching Arcadian's keel and have had no problems with cracking at the keel joint.

 As I recently stated in my profile, after eighteen years of spare-time work on the project my Badger is finally nearing completion. One major task I hope to wrap up this summer building season is bolting on the concrete and scrap metal keel. A dry fitting has proved that the bolts line up perfectly with the holes in the floors and that the keel's curved contour matches well the curve of the hull. Now, having read conflicting opinions on the subject, I'm uncertain which type of bonding agent to use, thickened epoxy or 3M 5200? is there a real possibility of an epoxy bond cracking, given the brittle nature of the material? If this happened what sort of "fix" could there be? The keel has given me the most trouble of any component in building the boat. With half cu. ft. test blocks I couldn't get the concrete and metal punchings to come up anywhere near the needed weight of 320# per cu. ft. so ended up using a whole ton of lead. The finished keel weighs 4150 pounds, only a bit more than Jay Benford specified. I worry, however, that based upon what seems to me a miscalculation on his part of the weight of materials in his instructions, my keel — with all its lead — may be too heavy for the boat, in which case I would likely have no choice but to remove it and either somehow lighten it or have another, lighter one made. Did he really mean that the keel should weight 4000 to 4100 pounds? I guess I'm asking two questions here: 1) epoxy or 3M 5200? and 2) has any other builder of a Badger had a similar problem coming up with the specified weight using only concrete, sand and scrap steel? I'd be ever so grateful to anyone here who might choose to provide advice. (My sincere apology for being so "long winded!!")