Flipping a Settee Sail

Canoe and Sail Rotated

In  my previous discussions on sails I waxed on about the Settee Sail  which is a  quadrilateral (4 sided)  sail. 

It is 4 sided by dint of a very short luff. How short is open to adaptation, but in exploring the sail offered by Bill Mantis --in excruciating detail --I realized that he too was offering a Settee Sail. He may not call it that, but that's the lateen he uses.

I was exploring the Settee and seeing how it may relate to the  Mantis  rig when I realized that he was in fact  adapting a Settee by turning it 90 degrees. The spar/rod instead of being suspended from a short mast, became the mast.

So I grabbed an image of a canoe rigged with a Settee Sail and turned it 90 degrees.

(See image: drop head to left shoulder  to view original horizontal mode)

Sails are going to  be dependent on  wind dynamics and just because you flip a sail , it doesn't necessarily mean that you transfer all the harvestible energy of the original design with the flip.

Traditional Settee Sail

But the fact that a good idea may work on a different dimension as well as its original is something I find very appealing.


The Sweet Logic


Hypothetically, if you consider the drawing and imagine that the spar that forms the diagonal is a mast and you straightened that mast closer to the perpendicular, the tail/bottom end of the sail will rise allowing for easier viewing less obstructed by the shroud. This would be the case in low wind.

Settee Rotated

If, as the wind rises you lower the mast  the sail will billow out as its surface area decreases due to the shortened angle. I wonder if you still get reasonable line of sight because of the billowing? As you shorten the angle to the horizontal  you 'reef' the sail.

The further option is that if you let out more sail --so to speak -- and allow more play in the sail by running out more rope at the leech (? : sail right angle/at bottom) to the lee you can harvest more downwind  without  either spinning  a batten  over the water  or steering the craft to the starboard.

The key difference is, of course, the luff (?:top aft/flap of sail) which is supported in the Mantis case by a batten.

And the spar doubles as the mast.

Bill Mantis sailing his rig

Brilliant.