by Bob Norson
Excessive weather helm can be exhausting
of crew and ruinous of autopilots. It also places unnecessary
strain on the rig and slows the boat down. Not that all weather
helm is bad. A certain amount is better than the alternative.
An unattended helm going to weather is of little concern. More
embarrassing than harmful but lee helm, the tendency to fall
off the wind can instigate an accidental gibe which in strong
conditions can be quite destructive. Lee Helm is common and no
issue in light airs.
How does it happen and what can you do
about it? There is a point in your boat underwater that the boat
pivots from. If you could look from above as equal force is applied
in opposite directions from your bow and stern you would observe
the one point that doesn't move, the centre of spin, the axis.
That is your Centre of Lateral Resistance or CLR.
(Figure C)Vessel trim can effect the location of
the CLR somewhat. The other factor is where the power is applied
on your sail boat. Your sail(s) have one point that is the centre
of that power. Depending on sail trim, heel, wind strength, sea
this point can move around a bit which is why
few boats will keep a course without helm input but overall it
won't shift too far. That is your Centre of Effort
When your CE lines up vertically with your
CLR, your helm is neutral. (Figure A)No input required
if you are on course. If the CE gets forward of the CLR the boat
falls off, Lee helm. If the CE is aft of the CLR,(Figure B)
there is your weather helm as the power in the rig is now putting
more effort aft, it pushes that part of the boat away from the
wind which causes the bow to turn into the wind as she pivots
on the CLR. This must then be corrected by rudder which when
used to excess is nothing but a big brake.
What to do? You can't easily change
your boats hull/rudder design but you can alter your CE without
cost and the article you have just
read explains how. Chronic weather helm can often be cured
or at least helped by rig adjustment. Moving the mast head forward
brings the CE forward. This will reduce weather helm. Conversely,
moving the mast head aft, or putting in rake has
the opposite effect. If the weather helm can't be cured to satisfaction
by rig adjustment then it's time to talk to your sail maker.
I was at the helm of a 100 foot schooner, The South Passage,
and noted the heavy helm. The skipper told me it used to be even
worse. The ship had had to have the main boom shortened and sail
area reduced to make the ship manageable. Sure enough, when I
looked at older photo's you could plainly see the change. They
didn't take off just inches!
If you can adjust your forestay anchoring
point or mast step forward, these are also methods to move your
CE forward to mitigate weather helm.
If your boat has weather or lee helm, or
if your boat points better on one tack than the other, the information
in this and Petreas article should help you work it out.
But! (There is always a but!) Don't mess
around with this if you aren't comfortable with your understanding
of the information. Do take baby steps in your learning curve
if you can. Easy conditions near a place where you can source
pro help for example but do not fear your boat either. Your pro
can't usually take an all day sail to fine tune.
Sailors have been doing this for thousands of years; chances
are we aren't any dumber than they were.
My qualification? None really, and thats
I was able to listen to people of Petreas qualification
and apply the information successfully. I am proof that any simple
sailor can do it. Also thanks to Dana Freeman.