Builders' Forum Archives
Re: for more info
Posted by Mark Camp on May 21, 2004
Thanks, Peter, Brian. Unusually pretty rig for a wingsail. In fact the whole boat is an oddly successful fusion of the modern with the traditional.
Ballast batteries are a natural idea that have been bouncing in my mind for a long time so I'll be eager to hear how they work. Dont need 'em on John's Sharpie, though.
I've been considering the various wing-sail or double-luff sail designs for my S. and G. boat abuilding. At first they seem the obvious fix to the glaring weakness of the traditional rig. But the more I study their history, the more it seems they have struggled to achieve their potential.
Interesting that they chose a rig based on the old balanced lug. Not known for its pointing ability. And in this rig, one of the aerodynamic flaws of the traditional lugsail rig (the upper spar) is magnified by exposing the engineered cross section as the leading edge of the sail. Sometimes these seeming aero flaws are not so bad in reality. Airflows are complicated things--maybe a high pressure bubble forward of the gaff is formed that acts as a virtual leading edge. Even the Bermuda rig is saved from total imcompetence by similar bubbles on the lee side and windward sides of the sail aft of the mast. When they first studied the drag created by the wires in the early airplanes, they wanted to see how much the drag would be increased by a second wire downwind of the first. Would it be doubled? No, in fact greatly reduced.
The traditional rig is like the internal combustion gasoline engine--it seems old and unsophisticated, but more technically appealing designs can't seem to overcome its practicality.
In Response to: for more info by Brian T. Cunningham on May 20, 2004