So noone suggested using Flettner both for sail and keel yet? 
Such advanced research. Would be nice to see it flying, or doing SOMETHING. Meanwhile I’ll take some of that Aloe Vera. Or is that even Aloe Vera?
There is not enough lift to lift the assembly with the propeller which is used here as a wind rotor, and also the bevel gear, both being relatively heavy compared to the potential lift of the bottles having a small surface area.
I was however able to fly a Sharp rotor like a kite for a few seconds, no more due to balance issues. A video of this experiment:
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Hi Pierre:
Yes I’m sure that kite could be stabilized in some way - at least it flew.
By the way, I realized I had peter Sharp’s email and have also been in touch with him, after you mentioned emailing him - thank you. He has a lot of interesting info to share. I pointed him to this website and he did visit here on the web.
Here’s my question about the Magnus/Flettner concept in general:
Obviously, the idea is the entrainment of the airstream by the surface of the spinning cylinder, right?
So why are the cylinders always smooth? Wouldn’t they entrain more air if they had a rough surface?
What about a series of ridges or fins to further entrain the air? This question might apply to rotor sails.
Does anyone know the answer to this one? I’ll run it by Peter Sharp too and see what he says.
Peter Sharp indicated that (without lifting gas in an inflatable version) a central large disc was required, as for any rotating Magnus effect kite like on
But perhaps end discs could be enlarged as for the Savonius-type kite on
I read somewhere that indeed a rough surface would be preferable. There is also the presence and size of the discs, the aspect ratio…
I have a question: would an inflatable Flettner rotor (which remains a lighter AWE option) like Omnidea, be as effective as a rigid rotor? Omnidea tests showed good performance but at a low tangential rotation speed (well below 10 m/s), and also a relatively high power consumption in regard to the low tangential speed.
I’m also concerned that wind pressure will hollow the balloon, putting pressure on it to hinder rotation.
Peter Sharp is really an expert in Flettner and (of course) Sharp rotors.
The latter can explain the previous.
Oh Boy, here we go again!
Airbus to launch new low-carbon ocean fleet featuring Flettner rotors (newatlas.com)
More “news of the future”…
One more rendering…
I’m wondering if the amount of supposed fuel savings will be worth the extra weight, additional power required to spin the cylinders, and the added physical and operational complexity and increased danger.
Do you think this is really going to happen? Or is it just one more fluff piece?
Love the way they are saving on their carbon footprint by producing airplanes. Like Norway’s low carbon oil.
6 posts were merged into an existing topic: Slow Chat II
Hi Guys!
I just saw a couple new articles on cylindrical sails for ships:
Both articles suggest 90% fuel savings in the headline, but it gets watered down to 50% in the text.
Is either figure likely to be true?
Giant cylinder sails could cut 90% fuel consumption in cargo ships (msn.com)
"cylinders would generate thrust by sucking in air, pressurizing it, and then ejecting it in a different direction. "
Cylinder sails promise to reduce cargo ship fuel consumption by up to 90% (msn.com)
“To achieve this, Zha’s giant cylinder sails would be mounted on the decks of cargo ships. These cylinders would suck in, pressurize, and eject air in different directions, generating ‘thrust,’ or momentum.”
Though Zha has published his research through the University of Miami, his invention is being developed through a startup: CoFlow Jet.
Diagrams compare the movement of air in CoFlow cylinders, versus Flettner Rotors. Photo courtesy of CoFlow Jet
Zha’s cylindrical designs use a twist on the Flettner rotors developed in the 1920s. Flettner rotors are large rotating cylinders that produce thrust at the proper angles when air passes over them. Zha’s cylinders, however, do not rotate.
Rather, the cylinder takes in a small amount of air from the intake, then pressurizes it with a device called an impeller, and then expels the air through an outlet to generate a pressure imbalance.
This creates a substantial amount of thrust and is extended through the full length of the cylinders - which, as a reminder - are several stories tall.
On large cargo ships, Zha said the cylinders could cut fuel consumption by as much as 50% - and by up to 90% on smaller ships.
See my comment on the linked video:
CoFlow Jet Green Aviation Presentation for Frost Science Museum (youtube.com)
If co-flow jet technology could give electric aircraft range “on par with conventional aircraft” (@time 0:34), which is a big “if”, then it could also increase the range of conventional aircraft, so “conventional” aircraft would then still enjoy a far superior range. So this one sentence makes no sense in two ways. First, is it really that good, and second, if so, wouldn’t everyone then use it? The wind tunnel test measures only a top wing surface, not what’s going on inside the wing to make it happen, nor the associated opposite forces. Renderings will appear to behave in whatever way is intended. Where’s the real aircraft to prove this? It could be demonstrated and proven at an RC model scale.
I think coflow technology is an interesting addtion to rotating magnus sails which seem to be experiencing at least some success around the world.
I think though that the notion that you can suck air in from an inlet and pump out at a nozzle is a bit farfetched because there are sure to be a lot of losses in the inlet to nozzle path. Maybe a rotating cylinder with fans is a more useful next step? Anyways, I would say this would be money well spent on basic research. If it can transition to an actual ship, time will tell
The CFJ ship sail page says no moving parts which I think must be an exaggeration. Surely they are envisioning som kind if compressor in there? I am also thinking about the amount of air that needs to be moved, and the diameter of the channels in which the air is moving, and how many bends these channels should have…
I think @dougselsam you would not be reading about all these if you were not interested and your curiosity was not triggered. Also meaning that you see some potential in such technology.
Interested, of course. Convinced? Not so much. For mostly the reasons you cite. For example, why aren’t STOL competition planes using Co-Flow Jets, if it works as advertised? Hmmmm…
The derangement syndrome pushes people to not fully question supposed “innovations” based on partial research results that may not, in totality, be as convincing as the pre-selected positive-sounding partial results that make it into the press-releases and investor packages.
The “researchers” sense where the money is, and realize big companies demonized for “destroying the planet” are willing to waste money to paper-over their use of hydrocarbons with highly-publicized short-term demo projects as “window dressing” that they never really expect to end up as standard operations.
Meanwhile, I just saw a video on “icebreaker” ships, many of which are nuclear-powered, and can operate for 7 years between refueling, and not even stop in port for a year straight. The video explains that they end up being more cost effective than having to go to port just to refuel all the time with bunker fuel.
And meanwhile again, I’m hearing more and more that the “climate scientists” are admitting
that requiring low-sulfur fuel has eliminated one of the main planet-cooling sources of atmospheric sulfur, which normally comes from volcanoes, but was enhanced by ships burning high-sulfur bunker fuel.
Meanwhile for the third time, most container ships have no space on the deck for sails of any kind - it is taken up by stacked containers. That’s most of what the average person thinks of when presented with ideas like this, without even thinking it through at such a basic level. There are only a few bulk carriers that could even think about trying to mount such big, heavy, cylindrical powered sails on their decks, which might also have to be reinforced just to support them. Is there even a true net positive result?
It all comes down to responding to partial stories. Luckily we have a system where, hopefully, after enough years, the truth at least has a chance of coming forward and settling out from the mass confusion.
I think this was already discussed here Co-Flow Jets - #48 by dougselsam. I see more relationship with suction sail (already discussed here Suction Sails) than rotor. I don’t understand the point of having a cylinder, it is probably suboptimal, it would be more appropriate on a wing, with a flap (a bit like bound4blue, but with blowing).
I don’t really trust results when I see negative Cd without a power coefficient given, it is meaningless.
An example is given with Turbosail from Jacques-Yves Cousteau:
I think you allude to a quote of a referenced paper:
It seems that both suction sails and above all Flettner rotors are starting to be implemented in the maritime domain.
For an AWE use, Flettner rotors like Omnidea’s balloon look to be easier to implement because a cylindrical shape is easy to obtain with a light inflatable balloon. And drop-stitch and similar technologies could (?) allow to stiffen the balloon and save energy consumption.
https://glomeep.imo.org/technology/flettner-rotors/
…and many other examples. Flettner rotors for ships are booming.
And for AWE Flettner rotors could be rather like rotors for ships (being inflatable balloons quite high pressure) rather than wings for airplanes. The kite I used for a stack of Sharp rotors was just a means to assist in takeoff.
Expected advantage for AWE: high CL(CL/CD)² with low motion.
Yup, we’ve seen so many of these flettner ships. They are a main feature in the latest “press-release-breakthrough” space. But will flettner sails for ships take hold, or is it a GW derangement-induced fad? As silly as they look, and as much space and material as they take up, and as much danger as they introduce, I think I know the answer.
And let’s remember, it is not practical on container ships, which produce the bulk of the emissions.
However, I CAN think of a reason why we don’t see them in airplanes.
Same reason the electric multirotor drones for carrying people are not taking off:
DANGER:
If you lose your power, you lose your life! Neither is capable of gliding to a landing.
You’d be wishing you at least had Sharp rotors!
Even then, what if some unforeseen failure impedes rotation?
For an AWES, it would be a blackout. If at the same time you were flying in an electric plane powered by this AWES, you could risk falling, excepted if you had the good idea to implement batteries. For the AWES itself, rotation would stop, and the AWES would go down slowly. 
On the contrary, a space saving (for a same power, thanks to the high lift coefficient) is expected compared to classic sails on masts. If many companies are now studying and building Flettner rotors, it is because they have found valid reasons.
Hello Pierre: I remain unconvinced. At most, I think we might see a few symbolic uses of these flettner sails, or other hard sails, because such decisions are made by the wrong people these days - for reasons of appearing to be “saving the planet” to appease the strong oppressive forces mandating such symbolic implementations. After all these years, how many ships are powered by kites, for example, versus all the stories you’ve heard for the past decade? I’d say the actual number is zero. The same will most likely happen with the flettner sails. It’s similar to the hydrogen-as-energy-storage theme - promoted by people who studied the humanities, but are unable to do even junior-high-school-level math.
I’m still wondering why, if sails are such a great idea for modern, giant steel ships, why don’t we see a single cloth sail on any such ship? Not one? After all those “news” stories? Come on - not one, right?
After what, a decade?
So the Flettner sails are that much better? As I pointed out, they are over 100 years old! Never worked out for anyone! Why would they suddenly work out now? And the latest stories are promising 95% fuel savings. Don’t you think that is laughable?
The only way any of this can be proven is with the passage of time. But, as I’ve shown with regard to all of this “press-release-breakthrough” stuff, and with AWE itself, no matter HOW much time passes, the true-believers will just keep on believing the next lying press-release, just as they believed the last 100. When I say the AWE people don’t really have a grasp of wind energy, it was at one time debatable, but after 16 years, at some point, people MIGHT start to say I was right all along, since nothing in AWE is working today. Is 16 years enough? I don’t know, you tell me.
Gen IV nukes could power merchant ships of the future (newatlas.com)
More possibly true, possibly not “news of the future”!
Watch the video - those old announcers with their “announcer-voice” and the symphonic music are so stereotypical of that era!