"Newdirections Int [Australia]" wrote in message ...
Think of a sailing boat as an aircraft on its side. That's what, in
principle, happens and the principals that you have described are the reason
that your sail area is greater than your keel.
Install some ventilation for the epoxy fumes (5Litres/second/square metre of
workspace) and try a nice single malt whiskey - It's a much nicer method of
addling the greycells.


"Parallax" wrote in message
om...
Almost mounting my mast so it would be underwater got me thinking (as
it should). Why not underwater sails? Force on a sail is
proportional to the density of the medium and that makes a 5 knot
water current give about 50X the force of a 5 kt air current on the
same size sail. This means you could sail across the Gulf Stream with
an underwater foil. However, I am not sure where your rudder and
centerboard would be, in the air? Could you make a planing boat with
an underwater foil taking advantage of the water current? That way
you would not be limited to the 1.2Xsqrt(waterline length) in speed
anf might get up to absurd speeds.
Then again, maybe this idea is the result of breathing epoxy fumes.


At the risk of starting a flame war:

Most keels do NOT act as vertical wings but only provide a lateral
force to resist windage and to keep the boat going straight. To be a
good wing, they would have to have an assymetrical cross section.

In principle, you could sail across the current if you could minimize
windage (waterage) from the water current just as you sail across the
wind with a normal sail. Maybe use an enormous "Air Keel" instead of
a keel in the water.

I know, I know, its simply a mental excercise and not practical,
but.....