Melt and Pour Lead Keel Bulb - i550 Sailboat

This past weekend, we moved ahead on a step that has been a bit intimidating – pouring the lead bulb. As it turned out, it wasn't as tough as I had worried. Kind of medieval work with the advantage of power tools. Speaking of tools, a power planer, grinder and air chisel were helpful.

The plan was to melt lead in a large pot over a propane turkey fryer. We built molds from plaster of paris using a bulb plug turned on a lathe to the dimensions shown in the plans. In order to prevent the plug from sticking to the plaster, we wrapped the entire plug in plastic stretch wrap. The plug came out of the plaster pretty easily with just a little plastic sticking to the plaster.

In order to have a slot for the keel strut, we made plaster molds of the bottom six inches of the keel strut and supported those molds inside the bulb molds with screws to hold them at the correct elevation while we poured the lead. We had to weigh down the strut molds to prevent them from floating in the molten lead prior to setting up. After the bulb halves came out of the molds, we trimmed them and weighed them. It turns out that we were 20 lbs too heavy. So I used a power planer to shape the bulb to its final size and weight. The air chisel was needed to shape the slot for the strut.

We bolted the bulb to the strut using six inch stainless bolts ½ inch in diameter that were trimmed flush with the bulb after they were tightened. After the bulb was bolted to the strut, I taped the bulb seams with duct tape and poured thickened epoxy in the slot to fill the voids around the strut and between the two bulb halves. Then epoxy/microballon was used to fair the bulb.

We probably should have used sand or something else to make our molds. Even though I let them dry for two weeks in a room with a dehumidifier, they vented a lot of steam when we started to ladle in the molten lead. It seemed a bit dangerous but we wore face shields and welders gloves while we poured and then got out of the way while the lead hardened. There is still a bit of fairing to do before painting but it feels good to get another major component nearly finished. More photos can be found at http://picasaweb.google.com/intune99.