DSK wrote:

Matt Colie wrote:

Strangly,
That is not at quite what the towing tank data work here says.
For a conventional vessle sailing in moderate conditions with a slight
weather helm (Ra 3).
Yes, the rudder has a lift component to weather and it is most typically
below the center of bouyancy.

MC wrote:
So now we agree.


Funny... do you realize what he's saying, MC? In any case, it does not "agree"
with your earlier statements.


Yes he does, he now agrees that the rudder gives lift with weather helm.
Read it again carefully.


Matt is exactly right, that lift comes at the cost of drag, and weather helm can
easily cost more in speed than it gains in reducing leeway. The usual figure
given as max desirable weather helm is 2 degrees, which ain't much.


Of course, we all know lift always comes at the expense of drag! The
real issue is why might lift from the keel be more efficient than that
of the rudder?

Since the question was weatherliness and not speed, the increased drag
may be acceptable.

You probably don't know this but tests with a full size boat showed that
having two rudders and no fin keel per se. produced some real benefits
in windward work but it was at the expense of complexity and diffuclty
in control.




I think you've evaded the point. Of course the keel provides most of the
lift but the rudder dfoes add some -right? Remember even a small gain
wins races to windward!


Really? You can state this from personal knowledge? How many races have you won,
MC? IIRC the last race you mentioned, you dropped out and ruined your dinghy
motor. Does dragging a dinghy upside down improve pointing?


We weren't racing -when racing we don't tow a dinghy do you? Where do
you get your strange ideas?


Cheers