Lateen (MiniCup) sail shape.
 

I tried my new polytarp MiniCup sails that I had edge shaped. One was
shaped according to the polysail directions with more "body" than the
other. The more "shapely" sail was really bad. The less shapely sail
had a problem at the leech where it curved radically to windward so the
air cannot flow over it too well. I tried to tighten it to get this
curve out with little success. It seems that lateen sails should be
cut with NO body and maybe even negative shape. I am not sure of my
next step but will involve some experiments.

Looked over the "more shapely" sail today and find that I can fold over
the curved edges to yield a "flat cut" but I will have to add grommets
between those I already have. This will look very odd but will be a
good test. While the first boat is being repaired from its mast step
failure, we will experiment with the flat cut sail and the one with
some body to see which is best.
I attached the sails to the spars with cable ties and had them all very
tight. I believe that by moving the sail outtward along a line
bisecting the gaff-boom angle and then using looser ties near the
gooseneck and loose ones at the outward end while having tight ones in
the middle, I can achieve the effect of a flat cut. If this works, I
will simply cut off a couple inches at the leech.

The ideal sail shape is to have some good curve at the front of the
sail and have the sail get flat as it goes back. It is also good to
have the sails shape twist so the back edge (leech)angles further from
the boom as it goes up. Lateen sails don't do this very well, they
just look neat.

An airplane wing is actually a good shape to model your sail after.
The top curved part of the wing being your sail shape.

A baggy sail is good in light wind sailing off the wind.

On 24 Apr 2005 20:03:29 -0700, wrote:

Looked over the "more shapely" sail today and find that I can fold over
the curved edges to yield a "flat cut" but I will have to add grommets
between those I already have. This will look very odd but will be a
good test. While the first boat is being repaired from its mast step
failure, we will experiment with the flat cut sail and the one with
some body to see which is best.
I attached the sails to the spars with cable ties and had them all very
tight. I believe that by moving the sail outtward along a line
bisecting the gaff-boom angle and then using looser ties near the
gooseneck and loose ones at the outward end while having tight ones in
the middle, I can achieve the effect of a flat cut. If this works, I
will simply cut off a couple inches at the leech.

Recut flat cut sail worked better than one with curved foot and luff.

wrote:
The ideal sail shape is to have some good curve at the front of the
sail and have the sail get flat as it goes back. It is also good to
have the sails shape twist so the back edge (leech)angles further
from
the boom as it goes up. Lateen sails don't do this very well, they
just look neat.

An airplane wing is actually a good shape to model your sail after.
The top curved part of the wing being your sail shape.

A baggy sail is good in light wind sailing off the wind.

On 24 Apr 2005 20:03:29 -0700, wrote:

Looked over the "more shapely" sail today and find that I can fold
over
the curved edges to yield a "flat cut" but I will have to add
grommets
between those I already have. This will look very odd but will be a
good test. While the first boat is being repaired from its mast
step
failure, we will experiment with the flat cut sail and the one with
some body to see which is best.
I attached the sails to the spars with cable ties and had them all
very
tight. I believe that by moving the sail outtward along a line
bisecting the gaff-boom angle and then using looser ties near the
gooseneck and loose ones at the outward end while having tight ones
in
the middle, I can achieve the effect of a flat cut. If this works,
I
will simply cut off a couple inches at the leech.

Yah, but better than what? Did it point higher? Go faster downwind?
Reach faster?

On 1 May 2005 19:03:39 -0700, wrote:

Recut flat cut sail worked better than one with curved foot and luff.

wrote:
The ideal sail shape is to have some good curve at the front of the
sail and have the sail get flat as it goes back. It is also good to
have the sails shape twist so the back edge (leech)angles further
from
the boom as it goes up. Lateen sails don't do this very well, they
just look neat.

An airplane wing is actually a good shape to model your sail after.
The top curved part of the wing being your sail shape.

A baggy sail is good in light wind sailing off the wind.