[PUP] Lightning and Re: Motor+sailer vs Motor-or-Sailer

[Mike Maurice]

> Lastly, Buehler and Kasten for example offer designs with a sail plane. 
> Surely they think these sails will move the boat.
> 
> R


If it takes 10-50 horsepower or so to move a small cruising boat, that 
can be translated into pounds of pull. That can be figured into so many 
square feet of sail area times so much wind speed. In other words, 10 
knots of wind times 300 feet of sail area equals say 10 horsepower 
(that's not the correct numbers, but you get the idea.).

It takes so much lever arm to make the boat stand upright or nearly so 
for each 10 horsepower of wind, call it ballast. It takes so much 
lateral resistance to keep the boat from sliding sideways, the more 
lateral R the more directional control you can anticipate.

If you keep on adding sail area, then it takes more ballast to keep the 
boat upright. More sail area also requires more lateral resistance, 
commonly called keel. The more sail, the more wind, the more keel the 
closer you are to a "Sail" boat. This is not rocket science and the 
factors that are required are pretty well known and have been since the 
early 1930's.


By the way, the more wind resistance from say a high cabin the more 
horsepower it takes to make the boat go. Which means, more sail, more 
ballast, more keel. You can see where this leads. At some point there is 
vanishing point where there is almost no additional advantage that can 
be gained.


Regards,
Mike

_____________________________________
Capt. Mike Maurice
Beaverton Oregon(Near Portland)