Jedi has stated the proper answers and solutions.
Our Caliber 40, designed in 1988 as a cruiser, and we purchased hull
72 in early 1995, had terrible weather helm
when sailed in gusty winds. At the time we bought our boat I had extensive experience racing
and skippering several serious and competitive race
boats so I really pushed the factory and sail manufacturer to deal with the problem.
Several sail makers spent a lot of time on our boat in winds up to 45 knots. The genoa
was recut twice and the main once. Eventually consensus was reached on close hauled down to close reach sail trim in heavy wind
or gusty conditions.
- manage the main to keep steady helm
at 7 degrees or less:
by using the newly installed cunningham - flatten that luff
being delicate with the traveller adjustment - no fixed rule
here - play with it
most importantly do not oversheet
a fishermans reef (bubbly luff) if perfectly acceptable because, as I promised my wife, we are not racing
- if the helm needed to maintain heading in gusts is more than 10 degrees
ease the traveller
ease the main
reef some more
- keep the heel between 10 and 18 degrees to minimize the effect of gusts and to maximize VMG
reef the main
furl the genny some more and if more than 22 knots apparent
completely furl the genny and use a staysail (or that sail on the inner forestay if I can't call it a staysail)
on our boat - more than 18 degrees heel just generates leeway but does nothing for VMG
BUT - the real problem was the stitching in the main - the 3rd sail maker convinced me that it was not the mainsail
material that was stretching - it was the thread between the panels
that was stretching. After putting in lots of tell-tales and vertical marking stripes we were able to verify that in gusts the draft
was becoming 30% - 50% deeper and moved at least three feet aft.
I ordered a very flat Spectra main with full length battens. IT SOLVED
ALL THE PROBLEMS!
stays where I put it in the gusts and I can shape the much stiffer material to put the weather
helm at exactly where I want it. On our boat that is 6 to 7 degrees.
I can still induce weather helm by over trimming and we still have to reef sooner than I expect, even after 13 years, but the uncontrollable weather helm in the gusts or very heavy weather is gone.