"Gary" wrote

Wow. this is dumb.
Sorry. I shouldn't have shot my mouth off, even if this is a
newsgroup. Since you seem to know what you are talking about, would
you please help me understand some of this stuff better?


First, a clarification: I didn't mean that you can't unbalance a sail
plan to the point that the vessel becomes uncontrollable, just that
most vessels tolerate much larger shifts than yacht designers obsess
about when they are balancing paper cut outs of the underbody on a
pin. Some vessels tolerate these shifts, which do create small
differences in rudder angle and helm force, better than others. I'm
sorry to hear about the handling problems with your ketch.

Now my questions:

Putting aside a few dinghies with jibing centerboards and some older
racing boats with keel trim tabs, the angle of attack of the
symmetrical foil that is keel or centerboard is exactly fixed by the
hull's motion through the water. Anyone can look at a boat hull and
figure out that it will go more easily through the water straight than
with the flow at an angle. Minimizing leeway certainly is a key both
to speed and making as high a course to windward as possible.

You say:

The flow across the rudder and keel have a slight angular component
but that gives "lift" hydrodynamically.


I would very much like to know where this angular component comes from
because I've clearly been missing something all these years. I've been
producing the angle of attack necessary to create the lift to that is
the opposite force vector to the sails by letting the hull go through
the water at a slight angle. Your way is clearly better because of the
lower drag. Please tell me how to do it.


In your other response, you said:

The optimum (heel) angle is usually pretty close to flat.

When I'm sailing my 32 foot boat alone, my weight does not effect heel
noticeably. I scooch as far up on the coaming as I can and stretch
lifelines out with my back but it doesn't seem to help much. On the
135 foot schooner I sailed to Bermuda on a couple of times, people
were too busy with classes, sleeping off watch, and other things. The
captain looked at me kind of funny when I asked if everyone could come
out and sit on the rail for me.

Most of the sailing I've done in boats big enough to sleep in has not
provided the opportunity to shift any significant weight. The only way
to reduce heel is to reef, ease sheets, or head up. I've always done
this just enough to get the heel down to the angle that the boat seems
to move fastest at. When I reduce the heel further, the boats I sail
have always slowed down. Heading up too much in strong breezes before
I got a little more helm time under my belt would sometimes result in
their slowing down so much that loss of water flow over the rudder
would lead to going out of control.

Clearly, I've been missing something all these years. I suspect it is
connected to my confusion about leeway. I'm sure that, after you
explain how to create the side force at zero angle of attack, I'll be
able to learn how to head up or reduce sail enough that there is
almost no heel. The hull will then be in minimum drag configuration,
symmetrical and going straight through the water, and the boat should
just fly.

I can't wait until next summer to try this out but first, you've got
to tell me what I've been doing wrong.

--Roger Long










































--

Roger Long