The sink-weight for the centerboard has been a bit of a puzzle for me. I thought 44 lb. (20kg specced in the plans) seemed like a lot. After reading some material about creating sink-weights, I thought, maybe, the plans were mistaken - that John really meant 20 lb. not 20 kg. But then the dimensions of the sink weight specced in the plans, when plugged into the formula I found, produced a weight of 44 lb. But I was hard-pressed to find a suitable mold measuring 2" x 3" by 8". What I found was a 1½" x 7" x 11" metal baking pan I decided to use for the mold. Lead was melted over a camp stove and poured into the baking pan to create a sink weight of 42 lb. Not quite the specced weight but close. The top surface of the weight isn't pretty but it will all be sealed and faired. If the CB doesn't stay down, I'll add weight…
By not using a 2" thick weight, I needed to fill space in the cavity. I "sealed" one side of the cavity with a piece of sheet metal wrapped in brown packing tape (to keep epoxy from sticking to it) and taped to the centerboard. I slathered neat epoxy on the edges of the cavity and layered a good amount of thickened epoxy over the taped sheet metal seal. A ¼" luan plug (cut to fit the cavity) was pressed into/onto the thickened epoxy followed by another layer of thickened epoxy. The sink weight was set on the thickened epoxy in the cavity and more epoxy was poured around the edges.
Thats where I left it this evening. Tomorrow I will coat the sink-weight with thickened epoxy, place another ¼" luan plug over the weight and "seal" it with the taped sheet metal backing board. Once the luan skins are sanded fair, I plan to cover the centerboard with fiber glass cloth.
As for the rudder, I am happy with the sink-weight. I plan to sand it, cover it with fiber glass cloth and fair it before painting.