In any event, in light air, a big round section with a relatively
flat entry will keep attached flow and build up much more power
than a draft forward conventional airfoil shape.

The navigator© wrote:
There we disagree, in ligh airs the angle of attack of the leading
section must be close to zero to attach flow.

??? How do you get this out of what I said above?

Hence it should be full.

No. To keep flow attached (actually, to re-attach flow after passing the
mast) the leading section should be flatter further aft. Furthermore, at low
Reynolds numbers, the lift/drag ratio is better for the sort of shape I'm
describing.

This is one case where theory and practice seem to mesh pretty well. I read
a lot about new methods of sail trim and watched some of our competitors,
and found that what looked wrong (a deep round section) was actually quite
fast.




Surely you would agree that aeronautiucs shows that deeper foils
generate more lift at low speeds....

Again, how do you get this out of what I said?


I can see the topping lift, whih is presumably straight, and the
distance from the battens to the topping lift does not appear to
increase towards the middle of the sail.

You are forgetting the roach...


No I'm not, I'm looking at the angle of the battens. When a sail is twisted,
the battens take a series of angles as you look up the sail. Not exactly
rocket science.


Looking closely, I can see what might be leach ribbons flowing.
That's a good sign.

Yes they are, and it is.

Depends on the boat and the conditions. Some boats like the top telltale
flying all the time, some like it curling back some of the time, some more.

Usually boats that like to pinch (as opposed to boats that do better footing
off) want to have the upper leach ribbon curling back at least 25% of the
time, although in light air you have to be careful that the upper section
isn't stalling.




Why do you have a backstay antennae and no wire to it? Is the
wire lead up the mast and to the antennae at the top?

Well spotted. The wire is off.


OK, that's allowed

It's a good idea until you go offshore. Means that the connections don't
'weather' until they are needed.

You need some No-Ox.

Fresh Breezes- Doug King