Evan Gatehouse2 wrote:

Winged keels are actually very HARD to get right.

This is a good point. I would agree about wings being difficult. A bulb
that doesn't do any lifting on it's own would be pretty hard to screw up
hydrodynamically unless you were obsessing about the last 1% of performance
for racing. Think about the drag of a lead wing that gets bent back on
itself after touching bottom


I don't like Sponberg's "beavertail" keel. I think there's a lot of
drag in the tail that isn't justified as an endplate astern of the
foil.

I could agree with that for racing but this is a cruising application. They
probably wouldn't notice much difference if they cut the bulb off flat on
back unless they had an identical boat to sail next to.

The most critical drag issue if they are going to sail anywhere that there
is kelp or lobster pots is having stuff slide off the keel easily. This is
always a problem with bulbs and the Scheel keel is expecially good in this
regard. I look at the Sponberg idea as a way to get the required volume in
the bulb without having to put if forward where it makes pot warps and weed
more likely to stick.

I'd try to emulate a Scheel keel (may be still patented) if you can get the
required area in but the Sponberg looks like it would shed most floating
stuff as well as any bulb.


Evan Gatehouse
(also a naval architect and ME)

--
Roger Long