SAIL TRIM & SPEED

by

Bruce Goldsmith

Reprinted from Rebel Rabble February 1981

     The skipper winning the most races inevitably is going to be the one with the best 
touch.  I call touch the simultaneous coordination of steering and sail trim with wind  
and sea conditions.

     Tactics and wind patterns can be reduced to a matter of odds; they tend to be 
spread out over a group of equal sailing minds over a given period of time.  But 
the guy who wins most is the one who can squirt out on two out of five starts, 
or squirt out of a pack after rounding a leeward mark.

     This same fellow doesn't even seem to be pointing particularly high, but he 
always winds up to windward.

     This guy has a great touch.  A few people seem to be born with it.  Most aren't.  
But studying how to coordinate steering and sail trim to the wind and sea conditions,
all at the same time, should help you develop your own touch.

     First, a little bit about your main-sail.  It's the key driving force in most 
small boats.  In general, a full sail with its maximum draft well forward has what
I call an accelerating shape (Figure 1 a).  This shape has power but doesn't really 
produce top speed and pointing ability.

Now a sail that is very flat with its maximum 
draft aft has a shape that can give you the 
potential for high speed and high pointing 
ability (Figure 1 c).  But it cannot provide 
the top acceleration and power you can get 
from the accelerating shape.

     You can achieve this complete range of 
shapes on most boats simply by changing the 
sail's luff tension and by adjusting the 
trim of the mainsheet.  The greater the luff 
tension on the sail the further forward the 
draft will be pulled.  If the mainsheet is 
also trimmed down, the mast (on a small boat) 
will deflect, which removes the draft from 
the front of the sail.




     This downward trim also tightens the leech, actually adding a small amount of 
draft in the after part of the sail.  The total effect of all these adjustments is that 
the entire draft will be reduced and moved aft in the sail.

     Sailing upwind is really a never ending series of accelerations; the shifting to 
higher speeds and higher pointing angles and then a slowing down again as the wind 
comes and goes.

     The smaller and lighter the boat and the more erratic the wind velocity, the more 
pronounced the acceleration and course headings are going to be.

     Simultaneously, he will alter course from what has been almost a close reach to 
a high pointing, angle.  And, as the inevitable slowdown comes once again from a 
drop in wind velocity, he gradually eases the sheet and makes the boat drop off to 
an angle that is again a close reach in time for the next puff.

     If this lull is going to last more than a few seconds, it is important in small 
boats to use the speed you have built up to help get your boat to windward.
The best way to do this is to hold the sail trim, steer a little higher, and 
simultaneously roll the boat to windward in a slow manner.

     In extreme lulls this tactic can land you a couple of boat lengths to windward 
without losing much potential speed.  The theory here is that the sail is going to
luff no matter what direction you point the boat, for the only wind left now is 
caused by boat speed, and the relative wind is going to be directly on the nose no 
matter where you are headed.

     But this condition will abruptly change again as the next puff hits. it is 
essential that you be set up to accelerate again as the puff comes by easing the 
sheet heading off slightly, and letting the boat heel.

     The guy with the great touch can first trim loosely for acceleration; but 
he is also able to change to a high speed, high pointing sail shape just as he 
reaches the end of his maximum acceleration.

     This maneuver sets the boat up for the "squirt" that everyone cherishes 
and it is especially noticeable in small centerboarders.

     Ideally, you should always trim the sails and position the boat with gentle 
sheeting changes and smooth steering-all done just an instant before the puff hits.

     If you do it too soon you will waste precious distance sailing to leeward.  
If you do it too late you will waste the first part of the puff and must use some 
of it to get the right trim and angle for acceleration.  This delays the squirt 
and, with boats around you, can be the difference in having clear air or not.

     When you are sailing in steadier winds it's more important to maintain maximum 
boat speed, and individual spurts have less significance. In this case you must 
search for an upwind groove.  When you have found it the boat will nearly sail itself.  
It should have a very slight weather helm, and be sailing nearly flat.

     Small changes in wind velocity and heeling moment will hardly change this feel 
at all.  But remember this steering groove is only made possible by the shape and 
position of the sails.  You must continually try to flatten your sails more to the 
high speed, high pointing sail shape.

     And if you start to sail too fat off the wind, the boat will gyrate quickly 
from the weather helm to a lee helm as the boat becomes level again from its 
former heeling angle.

     But if you try to sail to windward this way you will be sailing more by 
observing the leading edge of the sails than by really feeling the groove.

     If the sails are set too flat the boat will tend to have a constant lee helm, 
for the same forces that created a weather helm with a full draft sail now cannot 
deflect the wind enough to get a bite to windward with the excessively flat sail.

     Heeling the boat slightly will decrease the lee helm a little bit, but it 
will also reduce the drive.  You will notice the boat never squirts on a puff.

     If there is someone alongside who seems to be able to steer his boat a little 
higher, and can sail faster with sails set flatter, eat your pride and set your
own sails a little fuller.  And steer the boat at a little less critical
angle. The feeling is one of constant blah when a sail has been set too flat.

     When you are sailing "in high point conditions" namely, steady medium 
force air of 5 to 15 mph with no waves, the groove will be very close to a 
point at which the sails are set too flat.  In these conditions make sure 
you get the boat moving properly again after each tack, and closely watch 
for the occasional lull.  Steering the boat now becomes the critical factor, 
for the boat must be kept at just the right pointing angle.  Many times the 
sail will be so flat forward that you can be too high on the wind and pinching, 
and it still won't luff.

     And by the time you feel the boat slowing, it is already too late and 
failing off won't help much.  The reason: your sails are not set to give you 
that fast acceleration again.  So far I've tried to show the sail setting/steering 
relationships which can run from one extreme of acceleration to the other, which 
features super high speed and high pointing.  My discussion assumes a moderate 
sailing breeze of about 5 to 15 mph.  But sailing in winds on either side of this 
range should merely narrow your thinking toward the sail shape that applies.
For instance, if you're in a drifter, steering and sail set will remain in 
the acceleration stage longer.  Even after the boat gets moving, the sail shape 
and steering won't change much toward the high speed/high point range.

     However, in winds over 15 mph acceleration isn't the problem; you are now 
sailing almost entirely in the high speed/high point end of the range.

     Closely note, though, that waves can really play havoc with your touch in 
these heavy air conditions.  You'll also find you have a tendency to under react 
to the changing situation when the really big breeze comes in.  Strong wind and 
relatively small waves are typical of a rapidly increasing breeze and it is 
necessary to get to the flat end of the sail set range very quickly.

     The tipoff here is that weather helm increases and the boat feels glued into 
the water and bound up.  It happens because the mainsail has not been flattened 
enough for the wind.  In other words, you never shifted out of second gear you 
have power but no boat speed.   Now as the waves build up you might tend to keep 
flattening your sails even more to make the boat free up and get into high gear.   
This is a fatal mistake, for at this point you will be pointing too high and 
waves will be giving you trouble, forcing you to make leeway.  In short, when you 
finally get around to flattening way in for the breeze, you really should be 
moving back to a slightly fuller sail set and driving off a little bit more to 
compensate for the waves.  This is a time when that groove can really be elusive.

     Coordinating your steering and sail set with the 'wind and sea conditions is 
a subtle matter.  Changes must be smooth and simultaneously coordinated, If you 
are not moving your boat as fast as some of your competitors you've got to react 
immediately with a course change and a different sail set.

     Believe me, it's a constantly changing situation.  Running from acceleration 
bursts to the high speed range is always an exhilarating experience, and you can't 
learn how to do it overnight.  But once you get it you can lock in the groove and 
really perfect that bit of expertise every great sailor carries around with him-that  
little technique called touch.