Flettner rotors are practical. They have been proven on various boats. They can produce a Cl an order of magnitude higher than the Cd of the non rotating rotor. However the drive is not much compared with a sail of equivalent height.
A cruising rig will typically be sized to handle 15 to 20kts of wind without the need to reef. Beyond that the sail area is reduced. Reefing is not possible with a rigid wing so it needs to be sized to take the highest reasonable wind. In this part of the world 60kts can be expected on rare occasions.
Those AMS autonomous drones have a wing area around 1sq.m on an 85kg boat. The stated speed is 2.8mph. To put that in perspective an A-class cat has about twice the weight but 14 times the sail area. A wing of 1sq.m on an 85kg catamaran might be capable of surviving the worst conditions - time will tell. The little cats are stated as self-righting so the buoyant wing offers that potential.
I am aware of a a fellow who posts on proaforum who has played with rigid wing and is looking to scale up:
It gives an idea of what might be a "safe" size wing for calm water.
On 07/01/2016, at 2:10 PM, "robriley@rocketmail.com [harryproa]" <harryproa@yahoogroups.com.au> wrote:
The Russians have a few tris offered for sale with rigid sales but there is no reliable follow up as to there use. We know about the oceanography devices and there are others, and there was the Flettner rotor, most famously used on Cousteaus Alycone. No Alycone isnt the same, but by eye there does seem to be a lot of windage aloft
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Posted by: Rick Willoughby <rickwill@bigpond.net.au>
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