"Martin Baxter" wrote in message
...

What is the largest triangle (area) that can be fitted
into an area
bounded by the boom, mast (between gooseneck and backstay
crane),
backstay crane and backstay?

This is basically the problem that is causing such a
kafuffle in a few
other threads here.

Well actually it's not going to be a triangle because the
boom does not
extend to the backstay. We can increase the area bit by
bowing out the
leech of the sail to just reach the backstay at a point
roughly
perpendicular from the position of the clew on the boom,
this is roach.

For structural reasons the top of the headboard is not
pointed but
rather chopped of parallel to the foot and this is partly
why the
backstay is carried aft of the mast head by the crane,
allowing the head
board to hoist a bit higher.

Now hear is the rub: If we lower the headboard by a foot
and increase
the curvature of the roach to meet the headboard at the
new lower
position we REDUCE the area of the main. The roach,
expressed as a
percentage of the area of the main increases. This happens
for two
reasons: 1) The leech is now at a position further forward
of the old
on, so the distance from the point of maximum roach to the
line
connecting the clew and head is a bit larger. 2) The area
of the
triangle defined by luff, foot, and line connecting clew
to head is now
smaller. Consequently the roach percentage rises.

BUT, the overall area of the sail is LESS!

Now why would you not want a sail that hoists to the black
band?


I don't know, but all the racing boats I've seen are.

Scotty