Sorry OZ,

Wally asked what the shelf is for. I have to tell him.

I'll give it a try. Wally, the shelf is made of a very stretchy material
made to fill the opening at the bottom of the main when the sail is
trimmed to have a deeper draft. The theory being that the separation
between the foot and the boom will be a cause for the air to form a
vortex and lower the efficiency of the main. It is supposed to act like
the fins on the tips of aircraft wings.

Now, since the foot of the main is of flexible material and the free
footed main can carry the trim to the very bottom of the sail ( Sails
with there foot attached to the boom actually lose their trim at the
bottom of the sail) The possibility of the Vortex was eliminated by
putting a very light material that wouldn't have enough force to effect
the curve of the foot of the sail but would send the vortex off the back
of the sail rather than under it.

The shelf had to be made a material that would pull even with the foot
of the main when the main was flat. If it didn't that would have cause
its' own eddies.

I hope I haven't screwed you up but maybe at least you will be able to
see that there isn't any force on the center of the boom that could be
considered support.

Wally, I'm very surprised at how many in this group have no knowledge of
what the main shelf is.

AND; I'LL DRINK TO THAT!

Ole Thom