Everything Old is new again - Flettner Rotor Ship is launched

They must have done the sums on antiquated SAILS. More manpower, lower performance, great maintenance.

 

More relative to what? More relative to diesel electric - yes. More relative to other wind assist - doubt it, but we don't have enough real world data for what niches are best for which tech and where to draw the lines.

 

Huh? I actually said RELATIVE to sails, AND "More manpower, lower performance, great maintenance than Sail."
And as far as "real data", this whole thread is about how much more efficient rotor sails are then regular sails for wind assist, WITH actual performance data.

 

It looks great but you should go first.

 

I'm just trying to understand this response. Is it a comment on the first new article, of the E-Ship_1 being launched ?
If so, you can find further articles about its multiple Atlantic Ocean crossings fully loaded, some in this discussion thread.
"2021 · Since its maiden voyage in 2010, E-Ship 1 (developed for transporting. Enercon wind turbine components) has covered more than. 170,000 sea miles,"

 

@rwatson Sorry, but I don't understand what you mean in post 616. Are you saying they are comparing their proposal to old sailing ships, or that what they are proposing is, in effect, old sail tech. I still can't figure out what comparison you are trying to make.

Of course I'll continue to have problems with simple comparisons between power driven wind assist like rotors, and passive capture technology like sails and kites done using things like Cl. But that's just a concern over terminology and the methods of comparison. The total lift of a rotor is only partly due to the far field flow circulation. You can compute a lift coefficient for this, just as you can compute the lift coefficient for a helicopter's airframe. But we aren't going to compare a helicopter airframe's lift coefficient to that of a glider where lift coefficient is a meaningful performance indicator.

 

Its always hard to make meanings on the internet.
When you said "It looks great but you should go first.", I had no idea what you were referring to.
To this

or this


But as regards your observation
"The total lift of a rotor is only partly due to the far field flow circulation. You can compute a lift coefficient for this, just as you can compute the lift coefficient for a helicopter's airframe."
I get the impression that you have yet to dig deeply into the 3 dimensional formulas involved, as this very effective graphic illustrates.


This diagram shows the comparative CL using the various technologies, but the Rotor also has other great "extras"
1) It is trimmed with the turn of a button.
2) Its propulsive force is straight fore and aft on a beam reach, therefore very little heeling motion.

A full description of the practicalities of "sailing a cylinder" is found in this link
Everything Old is new again - Flettner Rotor Ship is launched https://www.boatdesign.net/threads/everything-old-is-new-again-flettner-rotor-ship-is-launched.24081/page-2#post-393067

Check out this old photo of a traditional sailing ship versus a rotor, and note
1) The higher pointing angle of the Rotor yacht
2) The vastly reduced healing moment of the Rotor yacht.

 

Turbosail – Cousteau https://www.cousteau.org/legacy/technology/turbosail/

 

The BIGGEST downside to this method, is all the air pumps and gear under the deck required to drive the rig..
For commercial use, the ability to move the "sail" around is a huge advantage,
This animation is now installed on at least one cargo ship.



Edit: Found the Actual Installation video.

 

As part of the comprehensive source of Flettner history, the 2nd Rotor ship , Barbara, rarely gets a mention


History of Flettner Rotors | Flettnerrotor https://www.esru.strath.ac.uk/EandE/Web_sites/18-19/Flettner/strathflettner.wixsite.com/flettnerrotor/history-of-flettner-rotors.html

 

The sailboat won that race, which indicates that the illustration above is not correct. If the rotor had anything like the efficiency it claims the sailboat would have easily been beaten.

The pointing angle isn't relevant since we have no evidence that they were both trying to go to windward when the pic was taken.

That 'wing types efficiency scale' appears to be complete fantasy. I own four or five wingmasts and a bunch of windsurfer rigs with pocket luffs, and there is no way that they provide as much extra efficiency as the relative size of the two left-hand rigs implies.

As the sailing scientists who I know say, if the theory and lab experiments do not tally with the real world experience then the theory and lab experiments are wrong, not real life. In real life there have been many, many boats with wingmasts that have shown little if any improvement over conventional rigs. They have been tried in Flying Ants, Cherubs, Merlins, 12 Foot Skiffs, 18 Foot Skiffs, Gwen 12s, speed windsurfers, Raceboard windsurfers, Moths, International Canoes and many other classes and been abandoned in every one of the named classes and most others.

The same applies to wingsails. They have been tried in As, windsurfers, Int Canoes, Moths and many other classes and normally abandoned after failing to show the expected performance.

Since we know that theory doesn't predict reality in that case, we know that we cannot trust the theory in other cases like the rotorships.

 

"The sailboat won that race, which indicates that the illustration above is not correct. If the rotor had anything like the efficiency it claims the sailboat would have easily been beaten."
The actual translation is "the sailboat won by a small margin."
Now you are just saying that one leg of a race dictates the whole outcome. Any experienced sailor knows that there is a lot more than just sail performance to win a race. For an experimental rig, the Rotor performed very well.

"That 'wing types efficiency scale' appears to be complete fantasy. I own four or five wingmasts and a bunch of windsurfer rigs "
Hmm, but not one Rotor sail, NOR any laboratory tests to support your claims.

"As the sailing scientists who I know say, if the theory and lab experiments do not tally with the real world experience then the theory and lab experiments are wrong,"
So, where are these "real world experiences" that prove the lab experiments wrong ?

"The same applies to wingsails. They have been tried in As, windsurfers, Int Canoes, Moths and many other classes "
So? What is your point ? For a start, every class you mention is really weight sensitive. Hardly a comparison of overall sail efficiency. And Rotors aren't built for toy ships.

"Since we know that theory doesn't predict reality in that case, we know that we cannot trust the theory in other cases like the rotorships."
We know no such thing! If a 100,000 ton ship reports predicted performance, what other evidence do you need ?

Guaranteed by the vendors

 

Marketing claims from commercial parties are not proof of anything. A vendor showing a guarantee is not convincing at all since they are normally matters of standard contract law.

As another example, the paper by Elie et al using a modified Hobie Tiger F18 catamaran claimed that a 2.8m by .45m rotor rig would produce half the power of the catamaran's standard 20m rig. However in the tests the rotor catamaran (which was slowed by dragging a small turbine) achieved 3.8 knots on a beam reach in 9.4 knots of breeze. Other runs achieved very similar results.

That is extraordinarily slow for a Tiger; far slower than a Laser Radial or 4.7 which gets over 6 knots on a reach in 10 knots (Bins et al paper on a sailing simulator) or a J/24 which sits on 6.13 knots on a beam reach according to the ORC. The Tiger with a rotor was achieving speeds close to that of an Optimist (using the speeds from Binns et al). Incidentally I've experimented with a Laser using a 3.3m Optimist rig, and from my very rough calcs and experience I'd guess it would do at least 4.5+ knots on a 10 knot reach.

A few calculations of yarsticks indicate that a standard Tiger in a beam reach in 9+ knots of breeze should be going roughly 9 knots, ie close to three times the speed of the rotor boat. With a good half-size rig it would, at a guess, be doing about 8 or more - not 3.8.

The point is that when a Hobie Tiger is fitted with a rotor that is allegedly half as powerful as a 20m2 wingmasted sloop and it then achieves speeds about a third of the speeds a Hobie Tiger can get with a normal rig and speeds that are slower than that of a J/24 or Laser Radial, then some of the calcs of rotor efficiency are way out of kilter.

That doesn't mean we reject rotor rigs (which I have never done) but it means that we have evidence that shows that some modern claims are way overstated. Some historical claims appear to be over-stated as well. It is therefore perfectly reasonable to not accept them.

 

The point is that when a Hobie Tiger is fitted with a rotor that is allegedly half as powerful as a 20m2 wingmasted sloop and it then achieves speeds about a third of the speeds a Hobie Tiger can get with a normal rig and speeds that are slower than that of a J/24 or Laser Radial, then some of the calcs of rotor efficiency are way out of kilter.

So, can you provide a link to these tests and craft?

 

Experimental proof-of-concept of an energy ship propelled by a Flettner rotor
Elie, B,
Bognet, B
Boileau,
Weber, M
,
J-C Gilloteaux
et al. 
Journal of Physics: Conference Series
; Bristol Vol. 2265, Iss. 4, (May 2022): 042057. DOI:10.1088/1742-6596/2265/4/042057

Out of interest when I was trying to find information on the Flettner yachts' performances in Die Yacht magazine archives, I noticed that Flettner Yachts appeared to be the biggest advertiser in the magazine. I was unable to find detailed information about the races. However, the fact that Flettner was advertising heavily underscored once again that (as with so many other "novel" rigs that cause big claims that are not backed up) the promoter was trying to make a profit by selling the rig. That is perfectly fine but it does lead one to ask why claims by such promoters are so often accepted with little question. We don't tend to accept claims made by car makers, toothpaste makers, real estate agents, builders of conventional boats and rigs or others who are hoping to profit by getting us to believe their claims - so why do people so often apparently accept the claims of rig developers without serious questioning?