J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Putting Rhapsody's Keel on a diet

For Rhapsody, I mixed thickened epoxy, made a "hot dog" shaped tube with it and taped it in place with wax paper at the bottom of the keel. I allowed this to harden, then shaped it and faired with the templates.

I don't think lead is worth it. Like 12 pounds in my case and worth something like 4 pounds of rail meat. Give a six pack to the crew and get more effect.

The foil simulator gives a bit more lift with a 1.5 inch extension, about 3 tenths percent. Not much but it's more than it gives you for shaving the aft sections to class minimum.

Seems the bluntness of my leading edge is a bigger deal. More likely to stall at low speed.

By the way...after some more measuring and number crunching, our class minimum keel section is an NACA 0012 with about 85% of the trailing edge trimmed off.

My leading edge is much more blunt than an 0012...much. The theory suggest fixing this should improve performance coming out of tacks, powering up at the line and managing light air chop. Might point better but really shouldn't make much difference when you're in the groove. Likely pinches better. Seems like the consensus of the actual benefits of of fairing to templates.

You may have the math to back it up (I know I don't!), but it seems to me that twelve pounds of additional weight at the extreme bottom tip of the keel would have more of an impact on righting moment than 4 pounds on the rail. Both the hiking position and the bottom of the keel are about the same distance from the axis of rotation (about 5'+ or -). Seems to me if you go to the trouble of adding the depth, mixing in a generous quantity of lead shot would be well worth it.

The thinner leading edge and the longer chord length make a significant performance difference upwind. I find I point better, accelerate a bit faster, and have a more stable groove in lighter air.

Imagine a vertical plane that passes fore and aft through the center of flotation. The righting force of a weight is proportional to the distance it is from that plane. Unless you got her WAY over, the rail is further out from that plane than the tip of the keel. Rail meat is much more effective than keel weight if you sail her flat. On the other hand, if your worried about knock downs weight in the keel tip is the best place for it.

Math aside, I'd do the whole thing in lead if I could figure out a way that wouldn't cost a fortune and I was sure wouldn't fall off. Expect I'll end up doing something like Bill.

That makes sense! Thanks for the explanation.