"Gary" wrote:

You've had yours pulled ;-)

So I have. I missed your the link when I wrote last night. (You can
tell that New Years isn't a big deal at our house.)

This turns out to be one of those newsgroup exchanges where two people
who actually do know what they are talking about hurl darts back and
forth reacting to simple statements and imprecise language. Clearly,
you were not trying to tell me that keels develop side force at zero
angle of attack, etc.

Aside from providing entertainment for the bystanders, these cyber arm
wrestling matches can be educational. I'm sure anything we say from
this point on we'll both find that we actually understand and agree on
when we dig deep enough into it.

Many of these discussions get kicked off by absolutes. I can't
remember if it was my statement or someone else's' but the proposition
that a freewheeling prop has more drag kicked off a long thread a
while ago. It's a true statement in that it will apply to the majority
of auxiliary sailing vessels and engine installations. In the
exceptions, the savings from freewheeling will be too small to be
worth the vibration and bearing wear. It is not a theoretically
accurate statement however because there are exceptions. If the
friction, pitch, and size relationships are right, freewheeling may
produce less drag at certain speeds. It's just not common.

The contribution of weather helm to performance is a similar issue.
The symmetrical keel requires an angle of attack to develop the
necessary lift. As you have pointed out, (and I have agreed while
sniping at you for thinking you were saying the opposite) the
resulting yaw increases resistance. The rudder can develop side force
lift without requiring a corresponding yaw angle of the hull as a
whole.

Small rudder angles can (that's "can"; not "will", "always", or
anything like that) increase speed made good to windward by developing
side force that does not carry the penalty of increased leeway. As the
angle increases however, the lift vector of the rudder is increasingly
aft and drag greater so the contribution quickly becomes negative. It's
a lot like my plane, the first 10 degrees of flaps increase lift with
very little change in speed. As I put them down further, they
transition into being primarily speed brakes.

My boat has a reputation for having weather helm. Driven hard in fresh
breezes, it carries a large rudder angle and a huge wash under the
transom. The angle is 15 degrees or more so there is certainly a lot
of drag but it is also nearly up to hull speed by this point so it is
not going to go a lot faster anyway. The boat remains very
controllable as I have noted and sailing it as I have posted before
makes the helm tolerable. Still, it would be nice to sail in those
conditions with just 2 or 3 degrees of rudder.

This situation does not exist on my boat because the lead is 15%
instead of 20%. No amount of sail area distribution without adding a
bowsprit would change the situation significantly. Moving the rudder
all the way aft to the transom would take a degree or two off the
angle because of the increased lever arm but that wouldn't turn it
into a boat that didn't have a reputation for weather helm. Moving the
leading edge of the keel way aft would have helped. The keel then
would have needed to be deeper to develop the necessary area. The boat
would be harder to haul out and in more danger if it dries out after
running aground (a real consideration for the kind of sailing in out
of the way places I plan to go). This kind of change might take
another couple degrees off the rudder angle.

The biggest change, as you have said and I have agreed in backhand,
would be achieved by an increase in stability. If I were designing a
new boat to be much like the E32, I would give it a bit more beam and
less keel volume (very thick as a heritage from the keel/centerboard
version).

All these changes are what I meant when I said (not too clearly) that
weather helm is more a function of the overall design than the
designer's fiddling with paper cut outs of the underbody.

Nice playing darts with you. Next time, we'll use a target.

--

Roger Long