I gave up looking for comparative information on boats.
It seems like every person who ever bothered to think a Flettner rotor boat was a good idea, didn't bother to also obtain a regular sailboat to compare the results against.
What is a LOT easier to compare, is wind power-generation turbines.
I started out tracking down the cover article of this example- http://www.boatdesign.net/forums/att...d-windmill.jpg
which is on Google books- http://books.google.com/books?id=jzj...page&q&f=false
...He got a $48K grant from the DOE to build it, but couldn't complete it. The GENERATOR it was supposed to run, he just couldn't afford. And unfortunately for science, that was the best way to determine how efficient it really was. But he was really, really sure
that it was making like, way
lots of power:
"...The major thing I don't have is the horsepower-versus-wind-speed curve", he laments. "And that's what will prove whether or not a Magnus effect turbine is economical. " (p. 62)
Apparently it wasn't.
The PopSci article noted that SoCal Edison was interested, but web searches 27 years after this story appeared don't turn up any Magnus-rotor windmills ever built or operated by them.
The PopSci article has a cutaway view of the hub internals; I'm not even sure what all's going on in there. The diagram text says that the rotors are only spun with external power to start
them spinning, and then the motor can be shut off as it's not necessary.
This looks like a perpetual-motion machine to me. If a electric motor is used to (1) spin five tubes to create a Magnus effect, and then (2) those five tubes spin around a windmill hub, there will always be losses between the two stages (1) and (2), so you'll never get more power out than the electric motor puts in.
Also I've not found any other articles that claimed the Magnus-tube-spinning motor could be turned off, or that the rotating of the individual cylinders could otherwise be powered by the wind. Have any of you?
Most of the actual, real-metal work of Magnus wind turbines has been done by a lone Japanese company named Mecaro: http://www.mecaro.jp/eng/introduction.html
I found a number of research projects, but could not find any other company actually selling a product.
They moved to a design using spiral fins around the cylinders.
On the above linked page they note that-
"... Since then, many countries have tried to develop the cylinder-blade windmill, but have not been successful to put into practical use. There was a problem to overcome that the smooth surface of the cylinders required top speed spinning of the cylinders, which consumed more power than the wind turbine could generate. ..."
The Mecaro website has a webcam page, by the by. When I looked, the windmill wasn't spinning.
But at least it is
a real windmill, that they really built
There's another (nameless) company that all they seem to have produced so far is generic-looking CGI movies of imaginary silvery spiral-Magnus windmills that work perfectly.
So okay, Mecaro has their spiral thing going on.
Nobody else seems to be doing it that way, but anyhow.
How many have they sold? .....Well, they don't say how many are sold or installed. The few photos I find on the company website or elsewhere are all located in or around the town in which the factory is located, leading me to believe that they are all "test installations" at least partially owned by the company itself.
Well, maybe most people are dumb and just scared of new things, and don't recognize a technological breakthrough when they see it?
Let's compare the specs of the Mecaro spiral-Magnus windmill with a similar-sized conventional (airfoil-blade) type:
Mecaro spiral magnus 5-rotor windmill - (specs given on the bottom of this
page) Wind Turbine Diameter........ 11.5m (37.7 feet)
Rated Output.................... 12kW
Rated Wind Speed.............. 11m/s
And here's a "normal" windmill I picked randomly from Google- (I went looking for windmills that had rotors close to the same diameter as the Mecaro spiral-Magnus) http://www.windturbinestar.com/20kwh-wind-turbine.html
Aeolos 20kw: Rotor Blade Diameter.......... 10.0 m (32.8ft)
Rated Power....................... 20 kw
Rated Wind Speed.............. 10 m/s (22.3 mph)
How strange,,,,,, in ~10% less wind, the slightly-smaller-diameter conventional 3-blade windmill produces nearly twice the power
that the spiral Magnus 5-blade does.
Okay, maybe Aeolos are a bunch of lying crooks. Who cares what they say?
Here's another model from another company, A & C Green Energy- http://www.acgreenenergy.com/PowerMa...rator_20kW.php
Powermax 20K: Rotor Blade Diameter.......... 33 ft
Rated Power....................... 20 kw
Rated Wind Speed.............. 24 mph
Another slightly-smaller 3-blade airfoil windmill, that produces nearly twice as much power in the same wind......
Here's another example, from Hummer Wind Power- http://www.hummerwind.com/hummer_20kw.htm
20kw (model) Blade Diameter............... 9m (29.5 ft)
Rated Power................... 20kw
Rated Wind Speed.......... 10m/s (22 mph)
And again: slightly smaller rotor diameter, only three airfoil blades, and yet producing nearly twice the power.
If you want a boat with a Flettner rotor, go ahead and have fun with it, you only go around once in life after all... but there's real reasons that most engineers ignore them, and it's not because they're too dumb to understand it, or nobody told them.