Saturday, June 3, 2017

Cast iron keels and keel bolts

Before..

...after sand blasting, epoxy filling and sanding, then three coats of epoxy primer the cast-iron keel of our Columbia 43 is ready for bottom paint. It has a complex and beautiful shape that you could only achieve with a strong, durable materal like iron.
I get a lot of questions about keel bolts. Almost every potential owner and owner of a Columbia 43 worries about them.

I only really know about my boat, a Columbia 43 Mark I, but I think it is like most of Tripp-designed boats Columbia built. They had cast-iron keels attached with galvanized keel bolts. The keel was set in a socket in the fiberglass hull with an industrial adhesive called Furane Epibond, which is still made today.
The keel installation page from the Columbia 43 plan set. Note the beautiful drafting, which was all done by hand. Tripp was a consummate artist.

Here's an interesting paragraph from a 1971 article in Boating Magazine describing in detail how the keel on a Columbia 43 is attached:

"With a 10,250-pound cast iron fin keel hanging on the bottom of the boat, we were interested in the method used to secure same. We found that the keel flange is flushed into a recess or pocket in the hull. Prior to attachment, the keel is given a dry run to check for accurate fit in the recess. If all is not well, the flange is ground to suit--the pocket is never ground except to remove gel coat. When the fit is satisfactory, the recess is coated with a thick application of Furane Epibond, and epoxy compound. With the entire weight of the boat resting on the keel, ten 3/4" diameter cotton-wrapped bolts, nuts, flat washers and lock washers are installed. Internally the keel weight is distributed by a heavy, glassed-in platform and a series of steel transverse channels that pickup the keel bolts. We were convinced that the keel is there to stay."

The article didn't specify that the bolts were galvanized steel, but the plan sheet for attaching the keel does. That's what is on my boat too.

Galvanized bolts were exactly the right thing to use. They start out being 18 percent stronger than the same sized stainless bolt. From there the stainless bolt has nowhere to go but down. I would not trust any stainless bolt more than 10 years old. They can look perfect and yet fail catastrophically with no warning.

Galvanized bolts, on the other hand, retain their strength even when they are rusty. So a 50-year-old galvanized bolt that is 18 percent rusted away is about the same strength as a brand new stainless steel bolt. I won't even get into crevice corrosion in stainless steel. Let's just say a damp bilge provides the perfect environment for crevice corrosion.

If someone, I'm thinking a boat buyer here, looks in a bilge and sees some rusty keel bolts they totally freak out! I've had more than one person tell me that they once considered buying a Columbia 43, but didn't because of the condition of the keel bolts. I also had a C-43 owner bemoan the fact that she almost had her boat sold until the potential buyer looked in the bilge and saw the keel bolts. I told her to get a wire cup for her drill and go to work on them to get the loose rust off them, wipe them down with acetone, prime with a rust converter and then spray paint them white. I hope that was good advice. (While you're at it GET RID of all the old useless wires, pumps and junk in the bilge.)

The keel bolts on the Columbia 43 Mark I were studs and can be backed out (theoretically). I wouldn't do it. I might sister them, but I would not do that either unless the bolts -- all or most of them -- had all but disappeared. I can think of all kinds of things that could go wrong. You could get the new bolts torqued wrong and start a leak, for example. (More about this later.)

The thing is, there are no cases where a Columbia 43 has lost her keel. If there were, we would hear about it. (Think Cheeki Rafiki.) Also, Columbia tested the adhesive system they used on these keels using it alone without any keel bolts. It worked fine, or so the story goes. I don't know if they went back and added keel bolts later or not. Let's just say I trust my 46-year-old keel attachment more than I would most new boats.

Now for the Columbia 43 Mark III: The Mark III was a later development of the original Mark I. One of the biggest changes Columbia made was a smaller keel (same depth, 6'11", but a much shorter chord) to reduce wetted surface. I haven't seen a Mark III out of the water nor have I seen the design drawings. From what I can gather the keel had external lead ballast on a fiberglass keel stub. I don't know what kind of bolts they used. I also don't know who did the redesign, since Bill Tripp (the Columbia 43's designer) was dead before Columbia came out with the Mark III.

One of my friends who has a Mark III in the Sea of Cortez had problems with his where it developed a smile (in boatyard parlance, it's called a "Catalina smile"). It looked like the keel was starting to become detached. He had a yard in Mexico fix it -- I don't know the details -- but so far he's happy with it.

Stumpy J, the Columbia 43 Mark III that competed in the 2013 Transpac and finished 6th in Division 8, the same division that Dorade won that year, also had problems with her keel. When the owner was getting her ready for the race someone recommended that he re-tighten the keel bolts. He did that and it caused leaks that plagued the boat throughout the race and afterward.

That's about all I know about Columbia 43 keels. I believe a lot of the Tripp-designed Columbia's had cast iron keels similar to the 43 Mark I. One notable exception is the Columbia 50, which has lead encapsulated in the fiberglass hull. (This, to me, is the most trouble-free method. I hesitate to say "best" because other things come into play.)

I generally think Columbia 43 boat owners worry a lot about keel bolts because they look bad, not because there is any real danger of losing a keel. Should I be worried? Comment below. You'll have to cite actual examples of keel failures if you want me to pay attention.