"Gary" wrote in

You have conveniently snipped your initial statement that was the
genesis of our discussion:

Oh, all right.

Moving the sail plan fore and aft will have an effect on the angle of
the rudder and the amount of helm force. However, very large changes
in the distribution of sail area have very modest effects. If the sail
plan looks normal, the boat will work just fine. Very small changes in
distribution that require the calculations that are so prominent in
yacht design books are only going to change the rudder angle by small
amounts and the helm force in ways you would have to make direct
comparisons between identical boats under controlled conditions to
detect.

Boats do turn out having excessive weather helm. When this happens, it
has more to do with the hull dynamics and rudder design than the sail
balance. It isn't because the designer set the lead at 10% instead of
12% or even 15%. The kind of things that can be done by tweaks like
raking the mast less are not going to turn a heavy helmed boat into a
well balanced one. They will help a little but the psychological
effect will far outweigh the actual change in helm force.

People will tell you that they have solved their weather helm by
adjusting mast rake but they have also really been paying attention to
the boat and their steering during the tweaking process. They are
tweaking other things besides the fore and aft position of the rig,
like leech tightness. During the process, they get to know the boat
better and their helmsmanship improves.

In racing boat design, where you are trying to wring every bit of
performance out of the boat, you might care whether the rudder was at
a 1.5 degree instead of a 2 degree angle in a 16 knot wind with a
perfect set of sails. In that case, you might look at the lead of
similar boats. For cruising, and even racing among dissimilar boats,
you're just fooling yourself. The rudder angle is going vary within
several degrees depending on how hard the boat is being driven and
other factors. Mast rake adjustment will also create detectable
differences when you are obsessing about fine performance and looking
carefully but this isn't the same thing as the distinction between a
boat with heavy weather helm and a well balanced one.

All else being equal, the amount of lead just establishes the wind
speed at which helm angle will be absolutely optimum. The more lead,
the higher the wind velocity. Too much lead and you will have lee helm
in light air but this it pretty hard to achieve in most boats without
a bowsprit.

Balance in boats is real but the typical presentation of it in yacht
design books and articles and the C.P. / C.L.P. business is a complete
crock.

--

Roger Long