dougies, go back and re-read it until you understand about vertices (not
vortexes, but vortices).

"vertical pressure distribution"? dougies, dougies, dougies, the term is
"spanwise loading". Now, go back to study hall.

JAXAshby wrote:

dougie, the tip vortex comes about because the pressure on the windward
side of
the sail is greater than on the leeward side. The greater pressure tries
to
make it to the lower pressure. the air on the heavy side rolls over the
aft
edge of the sail in the easiest possible manner, which includes going up as
well as back. This makes for the vortex as the aft edge of the sail meets
the
forward edge.

A little slower, Jax... Navvie is taking notes...

You have got part of the explanation of tip vortex, so far so good. But if
what you
say is all there is, then why are there not a series of vortexes all along
the
trailing edge instead of just at the tip? Of course, when the flow is just
starting, that's true, but after flow is established there is just a vortex
at the
tip.

Another thing to account for is vertical pressure distribution.





having a main sail downwind of the jib does not cause the jib airflow to
stop
trying to go from high pressure to low pressure. The vortex generated
causes
turbulant air from the jib to screw up the airflow across the main. moving
the
top of the jib lower than top of the main just causes the jib vortex to hit
more of the main.

okay?

But that doesn't answer the earler question... the differential pressure
across the
main is going to interfere with (and suppress) the tip vortex from the jib.
Got it
so far? That means that energy lost through the jib head tip vortex will be
less.

Now, is that energy gain for a frac rig greater or less than the gain a
masthead
rig gets from not having the jib head tip vortex disrupting flow across the
main?

Folks, I think Jax *might* begin to actually grasp the question this time....
any
bets?

Fresh Breezes- Doug King