CHECK OUT the sailing
canoe pages, by Dan Miller and yours truly, for information on
Rushton's batwing sails. When
more info arrives the descriptions will be more elaborate.
And there will be info on making your own batwing sail. In the meantime, check out these diagrams of gunter sails.
(Update: I've made a prototype batwing sail and tested it. It
seems to work very well. I've taken some photos and when they come back
I'll scan them.)
And here is Robert Laine's great little application which will give you panel shapes for homemade sails (...arrrgh, Windows only). Sailcut4 is for three- and four-sided sails. Sailcut8 will take care of junk sails, and with a little care, batwing-style battened sails.
But note that both Batwing sails and Chinese lugsails do not
require cambered panels. They can be one big flat piece of material. Of
course cambered sails will have more power when sailing to windward.
I MADE the junk sail and the small mizzen sail (called a dandy by oldtimers) on my canoe out of polytarp. Here's a link to my Junk Sail Tutorial:
I've also built a sprit-boomed leg of mutton sail, a sharpie-style battened sail, and an experimental battened lugsail with bendy airfoil battens. I'm working up a small crabclaw sail of the sort that proas use.
How to make a small sharpie sail (this one is really a good performer for all its flat simplicity):
How to make a small balanced lugsail:
One of the most interesting small-boat books I've read is the obscure Sea-boats, Oars and Sails by Irish yachtsman Conor O'Brien. A discussion of some of his ideas can be found at this link. While I don't agree with his hatred for boomed sails, he has some very well-worked-out simplifications for "small boats" (meaning 20 or 24-footers) and I wish he'd had a wider audience for some of these.
Illustration from Dixon Kemp's
Manual of Yacht and Boat Sailing,
first edition, 1878.
