Category: Ballast Keel

Boatbuilder Alex Hadden and friend John Peterson provided essential help getting the ballast keel moved under the boat, positioned for keel bolt holes to be bored, and then bedded and bolted in position. Great care is necessary in moving a keel weighing more than 1200 lbs., and jacking and nudging it into position. Both Alex and John had prior experience doing this sort of thing.

The first step involved moving the keel from its position outside the shed to directly under the boat. Tools at hand included pieces of pipe to use as rollers, strips of plywood to support the rollers, John’s tractor with a front-end loader, ratcheting straps, and some hydraulic jacks. To make space under the hull, we moved stacks of cribbing as far forward and aft as we could manage, and used jack stands to keep the hull upright.

The bucket on John’s tractor was able to lift one end of the keel so we could get rollers under it, and using a strap we pulled the keel out to the front of the shed. This was easy, as the pitch was slightly downhill. By adjusting the angle of the keel’s position on the rollers, we could steer it reasonably well.

We were able to push the keel up the slight incline into the shed, then lift it with the hydraulic jacks and pivot it into position under the boat without disturbing the cribbing.

The centerboard slot in the ballast keel needs to be aligned with the slot in the keel plank. We used pieces of lumber about 1 1/8″ thick, spanning the slot in both parts to guide the keel into position as we raised it with jacks. With the ballast keel contacting the keel plank for the first time, it became apparent that the fit was good, but would be improved if a bit of the ballast keel were shaved away. So we lowered the keel and John and I pared it down using a block plane and rasp.

Holes for the keel bolts had been drilled in Justine‘s floors before they were even riveted to the frames, and acted as reliable guides for extending the holes down through the ballast keel. Keel bolts are 3/8″ and 1/2″ diameter, and lead is very soft, so it requires drilling at low speed and using kerosene or something similar as a lubricant. The holes drilled were up to 8″ long.

After drilling for the keel bolts, the keel was lowered once more, drill shavings cleaned up, the upper surface of the ballast keel was coated with a layer of asphalt roofing cement, a layer of canvas, and a final layer of roofing cement. (The roofing cement and canvas act as a gasket to keep the joint from leaking.) The same process was used in fitting the deadwood.

We then bolted the ballast keel in place using silicon bronze carriage bolts I forged from bronze rod.

Bedding the keel with roofing cement is messy, particularly containing and cleaning up the squeeze-out as the keel bolts are tightened. The roofing cement continues to ooze out for several days. But there’s a great sense of accomplishment once those keel bolts are in place!

Although the Flatfish design incorporates a centerboard, it also has a substantial ballast keel consisting of a lead casting of 1270 pounds that is attached under the keel plank. The casting is about 8′ long. In the photo below, you can see that the longer bottom surface is flat, and the longer top surface is curved to match the curve of the keel plank that it will be fastened underneath.

The Flatfish plans set includes drawings for construction of a wooden mold in which the keel can be cast. The keel is cast upside down, so that the curved upper surface of the casting is formed by the bottom of the mold, and the flat bottom surface of the casting is at the top of mold and corresponds to the mold’s “fill line” (the top of the liquid lead just after the mold is filled).

Lead melts at 323 °C (613 °F) and this is hot enough to char wood but not burn through a 1″ plank. And if the wood surface is coated with a thin layer of refractory  (e.g., water glass), wood makes a perfectly good mold material for Justine‘s ballast keel. So the Flatfish plans suggest making the keel mold from 1″ pine planks.

The mold tapers significantly toward both ends, and its sides slope somewhat. All the joints need to be reasonably tight so molten lead will not leak out.

The slot for the centerboard is formed when the keel is cast. It’s made by a wooden insert about 1 1/4″ thick fastened along the centerline of the mold.

The after end of the mold is covered, forming a facet in the casting (this is where the “deadwood” will be—more about that in a subsequent post).

Small cleats across the top of the mold hold the centerboard plug in place, and keep the lead from forcing the sides of the mold apart.

Some home boat builders will melt lead and cast their own keels. I chose to have I. Broomfield and Son, a commercial foundry in Providence, RI, do the casting. A significant part of their business is casting boat keels. But I did collect as much lead scrap as I could (about 800 pounds) to save the expense of having to buy all the lead. About half of it was recycled roofing flashing, and the remainder took the form of large toroidal pieces that had been scrapped by MIT’s research reactor! (It had been checked with a Geiger counter to ensure it was not radioactive.)

Wood keel molds get used only once because of the extensive charring that occurs as the molten lead solidifies and cools. The foundry simply pries the mold pieces off the casting and they are discarded. I also had them fair (some machining, and a skim coat of filler material) and paint the casting’s surface.

On the second trip to Providence, my high school classmate Bill Hindle generously agreed to use his new truck to haul the keel casting back to Georgetown. The keel was on a wood pallet, and the foundry’s fork lift placed it on the open trailer I’d rented for the trip. We did our best to lash it down with straps, and while it remained more or less in place horizontally, the pallet took quite a beating each time we went over a big bump in the road. I’m sure we never exceeded the speed limit on the return trip.

I’d arranged for help in Georgetown when we returned with the keel. Our friend Dave Polito brought his tractor, made a rope sling that passed through the centerboard slot, lifted the sling with hooks on his front-end loader, and moved it onto blocks just outside the boat shed.

The finished keel was on site on August 5, 2015. It would be a little over a year before it actually was moved into position under Justine and bolted in place.