Flettner rotor proa
Ok, I just stumbled across this video of what looks like an Mbuli powered by a Flettner rotor.
And it’s fast!
https://www.youtube.com/watch?v=VuobfwRo-IE
Is this the new self trimming wing sail? Discuss.
I have been thinking a lot of Flettner rotor sails, but i really don´t like having a big cylinder rotating at 400 - 800 RPM on my boat. I don´t like being dependent on some kind of engine, multiple ball-bearings and supportive structure. It does not take much misalignment to create lots of vibrations and noise.
I think it is a good idea, but very difficult to build, if it needs to be strong, easy to service, easy to repair and generally “cruising-proof”.
For a racing/speed machine it could be real fun though. A very delicate carbon-fiber cylinder with lots of power for rotating it at high RPM. It could create very high lift and probably be very close-winded.
Cheers,
Johannes
Thanks for the link, tis most interesting.
Joseph Norwood covered rotors in chapter 7 of AYRS publication 120-II, lots of relevant material, even proposes a pedal powered proa.
Skip
Thanks for the link, tis most interesting.
Joseph Norwood covered rotors in chapter 7 of AYRS publication 120-II, lots of relevant material, even proposes a pedal powered proa.Skip
The pedal-powered flettner proa got built—and sailed at Weyouth. Don’t know how it did… I think the Thiink proa has been to Weymouth as well.
I believe Johannes puts his finger on it—the high rotational speed rotor not only makes for complications—and danger (what happens when/if it goes out of balance while spinning?—it also generates very large gyroscopic forces as the boat rolls and pitches.
Cousteau’s Alcyone had the best magnus-effect setup I’ve seen. The cylinder didn’t rotate; there was a huge vacuum fan inside, jillions of small holes in the cylinder and a rotatable “sliding valve” arrangement to cover/uncover the ones they wanted, depending on course. The vacuum just sucked in air where it would normally separate, reattaching flow. Final air flow—and final performance, were identical to flettner—but without rotating parts. It was unfortunate that the boat was unmanageable (very fat, flat-bottomed triangular barge, basically. Supposed to be a prototype for later ocean racers, but missed the mark. Threw researchers and crew alike off their feet. Also made them seasick. Worse, it was slow, always a death-knell. It seems the bad rap extended to the turbosail rig as well, which evidently was revolutionary.
Google: Alcyone also Cousteau-Pechiney Turbosail
Dave
There’s also the Rotorboat, by Stephen Thorpe:
The Daily Sail - Think you understand how rigs work?
AYRS Catalyst number 24 - Rotorboat (PDF, go to pages 26-30)
Cheers,
Paul
Flettner rotor monowing RC - Youtube
It is not my video.
Even though i understand the magnus effect and have toyed around with it (an big paper-tube rotated by my drilling machine) the flying Flettner rotor monomwing looks strange. It does not look like it should be able to fly, even though i know in a theoretical way that it can…
It is very fun to play with this kind of device, since it seems almost magical, doing something it does not like it could do.
Cheers,
Johannes
Here’s a resource links page on rotor kites: http://www.ict.griffith.edu.au/anthony/kites/rotor/
Interesting. One of my early memories is of flying a rotor kite with my dad, would have been around 1963. It was called a ‘satellite’ and I recall that it was quite powerful, but then I was only five years old at the time.
Mal.