From: steph@cs.uchicago.edu (Stephen Wilson Bailey)
Subject: Re: Cal 40...
Organization: University of Chicago Computer Science
Date: Wed, 26 Aug 1992 21:12:24 GMT

Sounds sorta like what we do on Wednesday nights.

First, the perfunctory: ``You can get polars for a Cal 40 from US
Sailing for $100 (member, $135 non-member)'' and figure out how fat
they think you should be.  Note that the polars only go down to 6.0
knots of true wind, and in lighter breezes the velocity predictions
can be way off.

Here are some light air observations based upon my experience with
heavy boats.

It is most important to keep the crew from running around, and
avoid maneuvering the boat (i.e. using the rudder).

It is very difficult to tell when you are footing.  Once you get
the boat rolling, by footing off somewhat, it is amazing how much you
can usually bring her up and still keep rolling.  With light air
there's little feel either in the sails or the helm, and boat speed
generated wind can make it feel like you're going fine long after
you've fallen out of the groove, so you've got to always be trying to
figure out what's happening with the true wind.

In light air, you've got to minimize drag.  Is your bottom
clean?  Less dead weight means less wetted surface and better
acceleration, so git rid of all that dead weight.  Is your prop folded
or feathered?  Most boats, especially older racer cruiser designs,
have minimum wetted surface with a substantial amount of heel---get
everybody sitting on the low side, this also helps the sails assume
their proper shape.  On many boats, you can further reduce wetted
surface by moving weight towards the bow---the stern section is
typically flat, for control when the boat is moving quickly.

Now to restate my understanding of the conditions: 6-8 apparent on a
beat is will be about 3-4 knots of boat speed and 4-5 knots of true
wind.

A light air slug will probably tack through about 100 degrees in 4
knots.

I'm assuming you're sailing time on distance PHRF scoring.  Time on
time is a different kettle of fish (that's what we use in our club).

Given 3 knots of speed and 100 degree tacking angle, it will take you
1867 seconds to cover a mile to windward.  The slower boat is allowed
to cover that distance in 1897 seconds, which means you must be 1.6%
faster, or the other boat must be going 0.05 knots slower.

On the other hand, if the slower boat tacks through 94 (as does a
J/30) in this light wind, you must be 8% faster, or the other boat
must be going 0.22 knots slower.

So depending upon how close winded your competitors are you may have
to be only a little, or a lot faster than them.  Unfortunately, it's
frequently the case that small, race oriented boats are faster and
more close winded than bigger ones in light winds.

On the other hand, with short courses, one decent wind shift, or
finding a spot of increased wind (or a hole) can wipe out all the
handicap difference between even the most disparate boats.  Hone your
knowledge of the winds and you can race competitively even in the most
ungainly tug.

Finally, we've found that we don't have a large speed margin over the
slower rated boats on the beats, so it is very important to get set up
and moving at maximum speed on the reaches and runs immediately, since
that's where we have our biggest speed advantage.

Good luck.  Let us know if you discover any useful tricks.

Steph


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