Hi Sam

This certainly seems unusual, I have to ask some silly questions just to
discount some basic things.

Are you new to sailing?

Did you have the centreboard down?

Did the boat appear to drift sideways in the water?

Was there a strong current and little wind?

Were there large wind shifts?

Did you have the sheets pulled in tight?

Were main and jib both on the same side of the boat?

Were you pointing as close to the wind as possible ,
luffing occasionally?

Does the main and jib both luff at the same instant?

Does the boat swing upwind or down wind or load the helm
in gusts?


Old sails are likely to be stretched out of shape and therefore
not as efficient as new. That will only have a small effect on the
boats ability to point to windward but effect it's speed to a greater
degree.

Weight distribution (fore aft) should not effect pointing much but can effect
the helm in gusts and especially jibing in strong winds. It is also critical
to boat speed. In light conditions, you want your weight forward to get
the transom out of the water. In that trim, the boat is operating in
displacement hull mode which is the most power efficient mode
but has it's limitations. When the boat speed is equal to the speed
of the wake you get one wave length from bow to stern so the hull
appears to travel in a trough between the bow and stern wave crests.
that is the maximum speed of a displacement a hull. Adding more
power will not significantly increase boat speed. For a corsair,
that is around 5 knts. To go faster than this, you have to retrim
into planing or semi planing mode by shifting your weight aft
until the transom is the lowest point of the keel. In this mode,
there is positive pressure under the entire contact area of hull and
water. This pressure lifts the hull to plane across the surface and
escape the wave drag limitations of displacement mode.

Now small sail boat hulls are generally designed for planing so as
speed increases, the stern is sucked down and the distinction between
displacement and planing mode is blurred somewhat. However if you
don't retrim aft, you will have a neg pressure under the keel at the stern
and this will not allow the hull to lift as much as it might. The greater
wetted surface area and consequent skin friction will not allow the hull
to reach its maximum possible speed.

Between these modes, you just have to experiment to find the best fore/aft
trim for the prevailing conditions.

Best upwind performance is gained by:

Balancing the helm best achieved by raking the mast fore and aft
until there is no side load on the rudder. The amount of heal and
fore/aft trim will have some small effect on the helm so you need
a balanced helm for normal sailing trim conditions. Note that
most boats are not balanced but tend to swing upwind in gusts
because this is safer for novice sailors but not ideal for racing.
Raking the mast back produces weather helm (tends to swing upwind).

Sail twist:
Tell tails placed in the main and jib luff will tell you if there are areas
of the sail that are not working as efficiently as others. The aim is the
lee and windward telltales to both lie back straight at the same time,
indicating smooth flow over both sides of the sail. If the lee tell tail
blows up, down or forward, your sail is stalling and needs to be eased off
a little. When working, this is done by pointing up wind rather than easing
off the sheet. If the windward telltale acts up, then you are about to luff.
so ease off the wind or pull the sheet on.

Now placing 3 telltales along the luff say at 1/6 from the foot,
in the middle and 1/6 form the sail head and all 1/3 from luff to leach
will tell you what the lower middle and top thirds of the sail are doing
and this will indicate if there is any sail twist. You adjust twist in the
main by vang tension and in the jib by moving the sheet block fore and aft.

Jib and main balance. You want the jib and main to be working together
so the jib and main telltales should be telling the same story. So adjust
the jib block inboard or outboard until they are. The jib should not
backwind on the main but both sails should luff at the same time.
In practice, you may need to compromise a little but err on side of
getting the jib in tight so you can point closest to the wind.

The biggest factor by far is tactical, taking advantage of wind shifts.
Wind direction is ever changing. These changes either knock you
off your course upwind (disadvantage) or lift your course upwind.
Now a knock on your tack is a lift on the other tack so you need to
go about to take advantage of the shift. Smaller changes are often
not long lived enough to be advantageous, larger shifts usually are.
Also in racing it usually does not pay to go out to one side of the course
on a long tack. You could get severely disadvantaged by a permanent
wind shift. Of course, there are sometimes reasons for doing just that,
more wind over there or cloud movement may be indicating a substantial
wind shift so one side of the course would be advantaged etc.
It's a matter for judgment, smooth snappy tacking. Do not tack
randomly but only for good reason. This alone can make hundreds
of meters difference per km upwind.


Regards,
Ken


-----Original Message-----
From: corsair_136 [mailto:samc@...]
Sent: Tuesday, 27 January 2004 4:47 PM
To: CorsairAustralia@...
Subject: [CorsairAustralia] pointing up wind


This is probably a very basic question and perhaps not appropriate
for this group - please let me know if that is the case...

I am now the proud owner of an old corsair number 136, and have spent
a very happy weekend bobbing around Port Phillip Bay in it.

I'm having trouble beating into the wind. (2 miles out and back and
only a few hundred metres further up the coast!) What are some of the
factors that affect upwind performance?

Could the very old sails be the problem? Weight distributon in the
boat?

Any help, or pointers to on-line guides, very much appreciated.

Sam Coates




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