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Rotating Sails Help to Revive Wind-Powered Shipping

239 points by ystad 6y ago

bufferoverflow 6y ago
Aren't kite systems much more efficient and lighter and cheaper? https://www.researchgate.net/figure/A-ship-sailing-with-the-assistance-of-a-kite-sail-Photo-Skysails_fig5_338901158 https://www.researchgate.net/figure/A-ship-sailing-with-the-...
- bserge 6y ago
  Surprisingly, no. Last time this was posted there were some efficiency figures, wingsails being the best, but Flettner rotors still beating old-fashion sails and kites. And rotors are very likely cheaper than a sail/kite long term (they need complete replacement quite often because of rips and tears).
- frederikvs 6y ago
  From the article : "Ships can easily be retrofitted, literally overnight, with rotors activated by an on/off switch." I think kite systems require more work, e.g. for launching & landing. When it gets taken down, you probably need to dry it, fold it, stow it, etc. So even if they are more efficient, lighter & cheaper, doesn't mean they're necessarily the preferred solution.
  - studius 6y ago
    With the technology we have today, why couldn't self-drying, self-folding, self-stowing sails be used to make ships even more efficient? Edit: there actually is a ship called the Oceanbird[1] with telescopic metal sails. [1]- https://www.youtube.com/watch?v=pZVDs4n_a0M https://www.youtube.com/watch?v=pZVDs4n_a0M
    - Tade0 6y ago
      Because that's a fairly hard problem comparing to just tacking two rotating columns.
      - studius 6y ago
        There's a patent for a memory metal sail[1], telescopic sail mast[2], automatic retractable sail[3], and many others[4]. Also, there's the Oceanbird[5], a modern car-carrying ship with telescopically retractable metal sails. [1]- https://patents.google.com/patent/US9481432B2/en https://patents.google.com/patent/US9481432B2/en [2]- https://patents.google.com/patent/DE202011101489U1/en https://patents.google.com/patent/DE202011101489U1/en [3]- https://patents.google.com/patent/CN103086280B/en https://patents.google.com/patent/CN103086280B/en [4]- https://www.google.com/search?q=telescopic+sail+patents https://www.google.com/search?q=telescopic+sail+patents [5]- https://www.maritime-executive.com/article/swedish-collaboration-unveils-world-s-largest-sail-powered-car-carrier https://www.maritime-executive.com/article/swedish-collabora...
        curtainsforus 6y ago
        All this complicated, fiddly tech, vs. two spinning bits of metal. I know which one I'd be more confident in...
    - frederikvs 6y ago
      Perhaps they could, assuming somebody is willing to make the necessary investment to develop what you describe. However, it will probably be a complex system, and like most complex systems, it will be fairly fragile. Compare that to these Flettner rotors, which are essentially "a tube and a motor".
  - mhb 6y ago
    Ships can easily be retrofitted, literally overnight, with rotors activated by an on/off switch. Kite systems seem far less practical but this can't possibly be true unless they're talking about a Sunfish. And even then, I'm skeptical. Or maybe they're using literally, as is the fashion, to mean figuratively.
    - jcims 6y ago
      Yeah that claim stinks to high heaven. You're just going to bolt these suckers down to the deck and plug in an extension cord? https://en.m.wikipedia.org/wiki/Rotor_ship#/media/File%3ACargo_E-Ship_1%2C_Emder_Hafen%2C_CN-03.jpg https://en.m.wikipedia.org/wiki/Rotor_ship#/media/File%3ACar...
      - fulafel 6y ago
        That picture is not of an auxiliary retrofited sail, but of E-Ship 1 which is all sails. The retrofitted ones are much smaller relative to ship size and are used together with main engines.
- perlgeek 6y ago
  Are they? How is maintenance? How sensitive are they in changes to wind? How much training does the crew need to operate either? https://en.wikipedia.org/wiki/Wind-assisted_propulsion https://en.wikipedia.org/wiki/Wind-assisted_propulsion says > In comparison to kite sails, Flettner rotors often offer considerable efficiency gains when compared to the size of a sail or kite vs. size of the rotor and prevailing wind conditions. But I'm not sure if this size comparison makes all that much sense (maybe the performance per dollar invested would be more interesting?) I'm genuinely curious about a comparison from an operator's perspective, and I also hope both approaches are being developed further.
- JamisonM 6y ago
  Pretty sure you need a tail-wind to use a kite system, this works in any wind.
  - frederikvs 6y ago
    Pretty sure you don't need a tail-wind. Regular old sails as well as kites can be used at various angles to the wind. See e.g. https://en.wikipedia.org/wiki/Point_of_sail https://en.wikipedia.org/wiki/Point_of_sail [edit] P.S. from my understanding of the mechanism, I'm not so sure these Flettner rotors are useful in a headwind. They work by creating a pressure difference, but in a headwind, you could only create a pressure difference between the port and starbord sides, not the front and back. Unless there's some mechanism I'm missing?
    - mannykannot 6y ago
      If, by headwind, you mean sailing directly upwind, then no, they cannot do that, but they can beat to windward like a sailboat (the direction of the rotation must be reversed when tacking.) According to Wikipedia, the rotor ship Buckau could sail within 20-30 degrees of the wind, though I suspect that is a misreading of the supposed source of that data, and that 50-60 degrees is a more plausible figure. Similarly, I suspect the claim that they can sail closer to the wind than conventional sailing vessels is in comparison to square-rigged ships. https://en.wikipedia.org/wiki/Rotor_ship#Pioneers https://en.wikipedia.org/wiki/Rotor_ship#Pioneers https://books.google.com/books?id=9lqwg3iZyH0C&pg=PA656#v=onepage&q&f=false https://books.google.com/books?id=9lqwg3iZyH0C&pg=PA656#v=on...
    - odonnellryan 6y ago
      I would be surprised if a kite system could get much closer than 90 degrees to the wind.
  - rightbyte 6y ago
    Aslong is the wire points forward of left and right the net force is forward right? In practice you probably want the wire +-45 degrees from the bow or something. That is where you would use a gennaker or spinnaker.
- harperlee 6y ago
  If I understand the concept correctly the rotor does not only work as "sail" but also as "air propeller", as you need to input energy through its rotation (that gets multiplied by the "sail" effect of the Magnus effect). So that's an apples to oranges comparison, that does not bode well for the kite (as it is "passive", not effecting any compounding of energy).
- rossdavidh 6y ago
  What I've read previously is that the kite systems took more training and skill to utilize, which was holding back adoption, whereas this sounds like it would be a much easier technology to use. Although, I do wonder if one could use both.
- hanniabu 6y ago
  I can see the ecological disaster of loose kites in the ocean already
- paulryanrogers 6y ago
  Kite lines can kill others nearby. There is some animosity between windsurfers and kite surfers because of this risk.
  - JoBrad 6y ago
    Surely this isn’t an issue in the open sea, where tankers would mostly be using this.
  - yardie 6y ago
    Kite surfers are the assholes of the sea according to some sailors. I've seen them zip in and out of navigation channels and between boats. Also had a few get dangerously close and cross our bow as we were sailing on a reach. Also, I do enjoy the sport. It's similar to endurance swimming and nearly every muscle in the body is worked. I found kitesurfers in some really remote banks and wondered how the hell did you get all the way out here.
- odonnellryan 6y ago
  How to kite systems work any direction into the wind? Like anything from the beam or closer?
- neurostimulant 6y ago
  Why not both? Flettner rotor works best when the wind is perpendicular and kite works best when the wind blows in the same direction to the ship's course.
JamisonM 6y ago
Perhaps also of interest: E-Ship 1 https://en.wikipedia.org/wiki/E-Ship_1 https://en.wikipedia.org/wiki/E-Ship_1 In service since 2010!
sradman 6y ago
From Wikipedia [1]: > A rotor ship is a type of ship designed to use the Magnus effect for propulsion. The ship is propelled, at least in part, by large powered vertical rotors, sometimes known as rotor sails. German engineer Anton Flettner was the first to build a ship that attempted to tap this force for propulsion, and ships using his type of rotor are sometimes known as Flettner ships. Container ships reduce the superstructure to enable loading but these rotor sails could possibly be used on oil tankers and bulk carriers. We don’t hear about autonomous water vessels very often, perhaps a Flettner water drone is possible. [1] https://en.m.wikipedia.org/wiki/Rotor_ship https://en.m.wikipedia.org/wiki/Rotor_ship
- musingsole 6y ago
  I can't recall the researchers name, only that they had some association with NCSU, but they worked heavily with wind-propelled aquatic drones. I remember a talk they gave about waiting for wind conditions and the quirks of the control system.
- icegreentea2 6y ago
  As noted in the article, many of these ships may need the ability to stow away the rotor to be able to pass under bridges anyways. It could still be viable for container ships.
  - jdeibele 6y ago
    Looking at a picture of a large container ship there's more of a challenge siting rotors. Up high they would be in the way of cranes loading containers and might require really strong (and large) towers to hold the rotors. Built only as high as the containers, it doesn't seem like they would see any wind. How would you envision them working on a container ship? https://zeymarine.com/wp-content/uploads/2020/01/container-ships-zeymarine-blog.jpg https://zeymarine.com/wp-content/uploads/2020/01/container-s...
    - icegreentea2 6y ago
      I'll admit that I straight up don't know how the structural loading would be like - but I seems to be me that you might be able to get some sort of telescoping solution that works ok. Since you'd probably need to clear the containers anyways to get the most of the power out of the system, the lower portion of the sail doesn't need to be a rotor - just a mast for the rotor section to telescope over.
nabla9 6y ago
MS Viking Grace has rotor sail. Fuel savings are 300 tons per year from the sail. It also uses LNG fuel. In best conditions the sail can provide 20% fuel savings. In reality much less than that, but it's a small sail compared to the size of the ship. Viking Grace is a cruiseferry, so even in full capacity it's almost empty compared to a cargo ship. Maersk Pelican (tanker): 8.2% fuel saving during the first year of operation. M/V Estraden (ro-ro cargo): 6.1% fuel saving. https://www.norsepower.com/ https://www.norsepower.com/
- PopeDotNinja 6y ago
  I don’t see the article specifically mention slow steaming... https://en.wikipedia.org/wiki/Slow_steaming https://en.wikipedia.org/wiki/Slow_steaming Using sails to increase fuel economy seems like a no brainer, but now I’m wondering if cargo ships were ever using sails to increase their maximum safe cruising speed. Does anyone know?
  - ghaff 6y ago
    Before steam they did :-) Sail died off pretty quickly once steam came in. [EDIT: Apparently in some applications much faster than others.] In the case of modern examples, I'm pretty sure it's been exclusively for fuel economy. And, until recently, the overhead associated with using sails was generally more trouble than they were worth.
    - nabla9 6y ago
      Steam ships used to have sails for a long time. Gradually the amount of sails deceased. Last ocean liners with sail assist were build in 1884. The most famous clipper (fast sail ship) Cutty Sark (later Ferreira) operated between 1870 - 1922 (17.5 kn max speed).
      - Retric 6y ago
        Yea, the original limitation was the manpower cost of manning the sails which is why they where eventually dropped. With modern systems they are almost completely automated, which makes them far more viable.
silicaroach 6y ago
Wow ... this comes up a couple of times a decade. It's like the Simpsons 'We'll build a monorail'. It's right up there with the Solar Sail scam.
- burlesona 6y ago
  It doesn’t seem quite like that. There appear to be a dozen or so of these ships already running, and more being converted. Perhaps this remains a small niche, but it certainly is an area of active investment and growth today.
UI_at_80x24 6y ago
This looks similar to something Jacques Cousteau implemented. On his ship the Alcyone. https://en.wikipedia.org/wiki/Turbosail https://en.wikipedia.org/wiki/Turbosail
- satori99 6y ago
  While they look similar, Turbo sails are not Flettner rotors. Turbo sails use an internal fan to draw air into the tubes, and vents are used to control where the air pressure drops. They do not rotate at all.
chooseaname 6y ago
This comes around every so often, with the same claim, then disappears.
- geocrasher 6y ago
  Indeed. It's one of those recurring engineering memes that makes the rounds every decade or so. Id be surprised if it hasn't been on the cover, or in the pages of, Popular [Science|Mechanics] at least once a decade for the past 50 years. What I personally don't understand is why these aren't themselves driven by a vertical air wind turbine. The rotational speeds aren't very high, and it seems like a no-brainer. A VAWT with variable vanes could easily be shut down in a storm.
  - selimthegrim 6y ago
    Savonius turbines just aren't very efficient.
carapace 6y ago
The interesting thing about the Magnus effect is that the lift goes up with the second power of the radius of the rotor, so twice as large gets you four times as much lift. The largest Magnus effect vehicle I know of was a huge sphere with the crew cabin hanging below it from the axle. The whole sphere was the lifting body. The old OMNI magazine had an article wherein they calculated that you could put Magnus effect rotors on a bus and it would fly at (speeds as low as) 35mph. I've had plans for years now to build large flying buildings (if I can get my act together I might eventually do it) using geodesic cellular kites and the Magnus effect. (Look up Alexander Bell's kites, and Bucky Fuller's "Cloud Nine" aerial city concept.) - - - - http://www.rexresearch.com/flettner/flettner.htm http://www.rexresearch.com/flettner/flettner.htm http://www.rexresearch.com/skybow/mueller.htm http://www.rexresearch.com/skybow/mueller.htm http://www.rexresearch.com/aero/1aero.htm#thompson http://www.rexresearch.com/aero/1aero.htm#thompson http://www.rexresearch.com/aero/1aero.htm#flettner http://www.rexresearch.com/aero/1aero.htm#flettner And I found some images but not the name of the upside-down-hair-band-sphere design on this blog post: https://steemit.com/airship/@everittdmickey/magnus-effect-airship https://steemit.com/airship/@everittdmickey/magnus-effect-ai...
- dragosmocrii 6y ago
  Can you get your act together and build this? I'd like to see the end result, and the process.
  - carapace 6y ago
    You and the other folks responding to this so positively have got me doing some soul-searching. One of my personal limiting factors on this is that there hasn't been a lot of interest so far. It's like, why perform if there's no audience? ("But, if we don't perform, in what sense do we have an act?" ~B.B. Rodríguez) So, um, wanna join my mailing list? mailto:~sforman/heliotrope.pajamas+subscribe@lists.sr.ht (Web interface: https://lists.sr.ht/~sforman/heliotrope.pajamas https://lists.sr.ht/~sforman/heliotrope.pajamas ) I'm joking, but I'm also serious: if you really want to see this happen the most useful thing you could do would be to pay attention to it. If I know folks are interested that's hella motivating, y'know? Cheers!
julosflb 6y ago
Related to this, a french startup is trying to build fleet of autonomous ships to harvest energy from ocean. They make use of flettner rotors also. https://farwind-energy.com/ https://farwind-energy.com/
deleted 6y ago
[deleted]
jeffreyrogers 6y ago
There were some planes that used this concept, but they were never commercially successful (partly because if they lose power they cannot glide to a landing like a normal plane can). I think it was used in some bomb designs as well.
russfink 6y ago
Off topic, but would a practical plan be to build a solar powered ship, with a large, miles-long towed solar panel array?
- jacquesm 6y ago
  You'd have to overcome the drag of that array. At a rough estimate at 1 KW / square meter for half the day it wouldn't be worth it unless you added a way for it to be pulled in at night (which is going to be pretty hard to do with solar panels which are quite fragile). On top of that, the ocean is about as hostile an environment as you could wish for and it wouldn't work anywhere near busy shipping lanes. Creative idea though, I haven't seen it before.
  - m463 6y ago
    https://upload.wikimedia.org/wikipedia/commons/e/ef/Solar_Sailor.jpg https://upload.wikimedia.org/wikipedia/commons/e/ef/Solar_Sa...
    - jacquesm 6y ago
      Yes, so? That's not exactly a towed array now, is it?
williesleg 6y ago
Not gonna happen as long as those china ships belch diesel fumes underwater so we don't see them. They're killing the oceans.
Tepix 6y ago
I've already bought some chocolate that was transported by cargo sailboat Avontuur, a 100-year-old 2-master schooner. Here's some information in English : https://www.zotter.at/en/about-zotter/projects/translate-to-english-kakao-setzt-segel https://www.zotter.at/en/about-zotter/projects/translate-to-... https://timbercoast.com/en/ship/ https://timbercoast.com/en/ship/ and in German: https://www.zotter.at/das-ist-zotter/kakao-setzt-segel https://www.zotter.at/das-ist-zotter/kakao-setzt-segel https://timbercoast.com/de/schiff/ https://timbercoast.com/de/schiff/ PS: The chocolate was delicious! It's also a fantastic gift for sailors
- usrusr 6y ago
  Oh, there's more than one? I only know the one that ends up with https://chocolatemakers.eu/eu/de/19-schokofahrt https://chocolatemakers.eu/eu/de/19-schokofahrt getting distributed from the Netherlands across neighboring countries by cargo bike. Surely won't scale for anything other than awareness luxury gifts, but that cannot be seen as a reason to look the other way when you happen to buy luxury gifts.
BurningFrog 6y ago
Some questions after spending 10 minutes studying this: 1. These ships all seem to have two towers. Why not more? Can't they be closer for some science reason? 2. This works by spinning the towers using a motor. How do the propulsion gains compare to using the same motor power on a propeller?
- frederikvs 6y ago
  Regarding the two towers : if you look at the E-ship 1 [0] you'll see 4 towers - 2 in the front, 2 in the rear. There are no towers in the middle, probably because that area is intended for cargo. I presume there is also a minimum distance they need to be separated - if you look at some of the illustrations of the Magnus effect [1], you'll see a turbulent region downwind of the tower. Another tower in this turbulent region won't work as intended. This is pure speculation on my part, but perhaps most ships simply aren't wide enough to have two towers side by side (the E-ship 1 being an exception). That, and wanting to use most of the ship for cargo, explains why most ships only have 2 towers. [0] https://en.wikipedia.org/wiki/E-Ship_1#/media/File:Bateau_enercon_P9240983_part.jpg https://en.wikipedia.org/wiki/E-Ship_1#/media/File:Bateau_en... [1] https://en.wikipedia.org/wiki/Magnus_effect https://en.wikipedia.org/wiki/Magnus_effect
  - shagie 6y ago
    There is a fair bit about the design and its efficiency at https://www.stg-online.org/onTEAM/shipefficiency/programm/06-STG_Ship_Efficiency_2013_100913_Paper.pdf https://www.stg-online.org/onTEAM/shipefficiency/programm/06...
kebman 6y ago
I'm just thinking out loud. Some things don't need fast shipping. Instead it needs a steady and even supply. And if a ship doesn't use any fuel, it could even serves as a kind of movable storage house. Thus I'm really looking forward for the developement of autonomous sailing ships. I really believe there's a market for them, or at least a niche within shipping.
- lopmotr 6y ago
  Although reducing speed and fuel usage reduces fuel costs, it increases fixed costs (you need more ships for the same throughput) as well as operating costs like crew. It might turn out to still be more expensive in the end. Then there's the problem of less certainty about price changes if you have to wait longer for the product to be delivered which leads to inefficiency (over/under-supply if mispredicted). There's also the opportunity cost of money being tied up for longer in the delay between production and consumption.
- kardos 6y ago
  Would they not be sitting ducks for pirates?
  - stubish 6y ago
    Kidnapping and ransom seems to be the most profitable part of piracy. Insurance costs would likely go down for unmanned vessels. You could spend money on arms and mercenaries and RPG launchers and machine guns and escorts and drone squadrons through danger zones, but it is cheaper to just pay insurance. If insurance stops working, the next cheapest would be to pay pirates protection money to keep other pirates in check. https://www.forbes.com/2010/04/15/pirates-somalia-shipping-insurance-business-logistics-piracy.html https://www.forbes.com/2010/04/15/pirates-somalia-shipping-i...
  - kebman 6y ago
    On the open ocean? No. That's very unlikely. Along contested shores? Yes. That's where you'd employ the coast guard or naval forces to protect the vessels. Perhaps you could even bring aboard an armed crew as needed, or employ various defences, beginning by making it harder to breach the containers, up to just about any fully automated defence system you can imagine.
Animats 6y ago
Oh, Flettner rotors again. Those keep coming around. Jacques Costeau used to have a rotor ship, the Alcyone.[1] It wasn't really worth the trouble. "In fact, we were motoring most of the time" - Alcyone's captain. [1] https://sea-to-summit.net/the-flettner-rotor-makes-a-comeback/ https://sea-to-summit.net/the-flettner-rotor-makes-a-comebac...
- geoduck14 6y ago
  >Those keep coming around. BAA HAHAHAHA
- ipsum2 6y ago
  That piece is some high quality independent journalism.
- Angostura 6y ago
  Been reading about them for decades, but the good news here is that there a bunch coming into service.
wefarrell 6y ago
Would like to see more about what's going on below the waterline. The challenge with any form of wind power is that the propulsion doesn't typically point forward - it's at an angle with a forward component. So on a sailboat you need a long keel (or centerboard/daggerboard) to translate the lateral propulsion into forward movement. That constricts the vessel from operating in shallow waters and causes the vessel to lean due to the opposing force under the waterline.
mmaunder 6y ago
Very little discussion here or in the article on why use these in favor of traditional sails. Looking at America’s Cup, the trend one would expect would be foils supplemented by motor and more traditional sails. I’m sure these are easier to deploy, but consider that an America’s cup boat can do 40 knots in a 12 knot breeze. Sure that’s without cargo and on a highly optimized design with hard working crew, but it does prove the remarkable efficiency of a traditional wing.
- dzhiurgis 6y ago
  Indeed one is for racing another for cruise. Wonder if you can make inflatable tower for lesser weight and reefing. Maybe there’s some stable design where you start foiling using motors then when you are stable - use excess power to turn rotors. AC75 boats are very unstable without foils and these things are heavy as.
- throwaway0a5e 6y ago
  Racing has a very different labor cost situation than commercial freight. Commercial freight will likely make use of far less energy efficient but far more labor efficient designs.
- nabla9 6y ago
  You can just install these rotating wings on the deck and get 5-7% increase in fuel efficiency immediately and lasts 20-30 years with minimal maintenance. The investment pays itself back in 3-8 years. Wing is obviously more efficient. The problem with the wing is the cost and size. You need to design the ship for the wing. https://en.wikipedia.org/wiki/Oceanbird https://en.wikipedia.org/wiki/Oceanbird
- walrus01 6y ago
  > but consider that an America’s cup boat can do 40 knots in a 12 knot breeze an america's cup boat is to sailboats what an F1 racing car is to a toyota camry. at the very high end of bespoke carbon fiber racing sailboats with crews of 8 or more, we're talking about toys for billionaire status symbols... Look at the ownership and sponsorship of the boats in this for instance: https://en.wikipedia.org/wiki/The_Ocean_Race https://en.wikipedia.org/wiki/The_Ocean_Race
dzhiurgis 6y ago
So how well does these sails point into wind and how do control lift angle?
- _hl_ 6y ago
  They don't. The lift is orthogonal to the wind direction, so it will be most efficient when the wind is directly from the side, with the forward force falling of with the cosine of the wind angle. There's really no way to change that with these types of sails. This is actually quite an important limitation for cargo ships, as wind directions on the large oceans are somewhat constant and mostly east-west. Hence these sails would be better for north-south routes.
AtlasBarfed 6y ago
I just wonder if massive sails that double as solar panels, and additional fold-out solar arrays, would be superior overall and lighter. But any short-term "jury rig" is valuable. And if we get enough cheap excess green energy, carbon-neutral artificial fuels might be superior too.
yread 6y ago
Slightly related: wind powered car that goes faster than the wind https://phys.org/news/2010-06-wind-powered-car-faster.html https://phys.org/news/2010-06-wind-powered-car-faster.html
- comboy 6y ago
  This is so counter-intuitive. I couldn't wrap my head around this and wikipedia article was more helpful to me than the article: https://en.wikipedia.org/wiki/Blackbird_(land_yacht) https://en.wikipedia.org/wiki/Blackbird_(land_yacht) Thanks for the link.
- Metacelsus 6y ago
  I remember this was on a Physics Olympiad question! (And I got it wrong . . .)
voldacar 6y ago
Super interesting - is a perfectly smooth cylinder most desirable? or should it be a little rough in order to better tug on the air as it spins?
- cadence- 6y ago
  On photos it always looks smooth. I guess you also need to make sure it doesn’t cause too much drag when not in use (for example, if you travel against the wind).
  - blacksmith_tb 6y ago
    I wondered that as well - I suppose the added weight/complexity of using vanes that could be folded in (sort of like a big turbocharger) must not be worth any gains. Hard to beat the simplicity of a big tube.
- hliyan 6y ago
  Theoretically, there is no aerodynamic difference between a rotating, perfectly smooth cylinder and a non-rotating one. I'm not a physicist, but judging by the fact that basketballs tend to perform best in popular Magnus effect demonstrations, I'm assuming some surface texture is necessary.
dghughes 6y ago
I remember seeing this on the cover of Popular Science in 80s (maybe early 90s). A ship with a large cylinder used for propulsion from wind energy. edit: I found the issue https://www.google.ca/search?sa=X&sxsrf=ALeKk01n7hvalLGEwW3eeY3YxlQXY64mxw:1609101075935&source=univ&tbm=isch&q=%22popular+science%22+magazine+spinning+sail&hl=en&ved=2ahUKEwiIkKfQgO_tAhWpGVkFHTw9AIIQ7Al6BAgHEAo&biw=1920&bih=1086 https://www.google.ca/search?sa=X&sxsrf=ALeKk01n7hvalLGEwW3e...
colinmegill 6y ago
RC Plane leveraging Magnus effect https://youtu.be/GAqLyyg2AHk https://youtu.be/GAqLyyg2AHk
oli5679 6y ago
Naive question: is solar + battery feasible for shipping?
- hliyan 6y ago
  Water offers a lot more friction than air and requires a lot more energy to push a ship through than can be generated even if we cover the entire ship surface with panels. Of course, it can offset some of the energy requirements. The ship can be made wider to accommodate more panels, but that in turn increases the contact between water and hull, increasing friction. If we extend the panels over the hull, wing-like, the ship will be unstable under the windy conditions often found at sea.
mixmastamyk 6y ago
Thankful. The few times I’ve been on a ferry or cruise ship I’ve been appalled enough at the amount of pollution to not do it again. Are there any other technologies like solar, wind, or gulp nuclear, that are becoming economical?
- bluquark 6y ago
  It's one of the hard bits of decarbonization. The current trend is towards lighter varieties of fossil fuel (especially liquefied natural gas). In the long run, it could be fully decarbonized with hydrogen. See https://safety4sea.com/cm-shipping-decarbonization-what-does-the-future-hold/ https://safety4sea.com/cm-shipping-decarbonization-what-does...
pqdbr 6y ago
There's a great Veritasium video explaining the Magnus effect and the Flettner rotor here: https://www.youtube.com/watch?v=2OSrvzNW9FE https://www.youtube.com/watch?v=2OSrvzNW9FE The Norsepower company (which installs Flettner rotors on ships) also has a short video explaining the effect here https://www.youtube.com/watch?v=FUCShEXkpL8 https://www.youtube.com/watch?v=FUCShEXkpL8
ngcc_hk 6y ago
No picture or video ?

239 points by ystad 6y ago

Aren't kite systems much more efficient and lighter and cheaper? https://www.researchgate.net/figure/A-ship-sailing-with-the-assistance-of-a-kite-sail-Photo-Skysails_fig5_338901158 https://www.researchgate.net/figure/A-ship-sailing-with-the-...

bserge 6y ago
Surprisingly, no. Last time this was posted there were some efficiency figures, wingsails being the best, but Flettner rotors still beating old-fashion sails and kites. And rotors are very likely cheaper than a sail/kite long term (they need complete replacement quite often because of rips and tears).
frederikvs 6y ago
From the article : "Ships can easily be retrofitted, literally overnight, with rotors activated by an on/off switch." I think kite systems require more work, e.g. for launching & landing. When it gets taken down, you probably need to dry it, fold it, stow it, etc. So even if they are more efficient, lighter & cheaper, doesn't mean they're necessarily the preferred solution.
- studius 6y ago
  With the technology we have today, why couldn't self-drying, self-folding, self-stowing sails be used to make ships even more efficient? Edit: there actually is a ship called the Oceanbird[1] with telescopic metal sails. [1]- https://www.youtube.com/watch?v=pZVDs4n_a0M https://www.youtube.com/watch?v=pZVDs4n_a0M
  - Tade0 6y ago
    Because that's a fairly hard problem comparing to just tacking two rotating columns.
    - studius 6y ago
      There's a patent for a memory metal sail[1], telescopic sail mast[2], automatic retractable sail[3], and many others[4]. Also, there's the Oceanbird[5], a modern car-carrying ship with telescopically retractable metal sails. [1]- https://patents.google.com/patent/US9481432B2/en https://patents.google.com/patent/US9481432B2/en [2]- https://patents.google.com/patent/DE202011101489U1/en https://patents.google.com/patent/DE202011101489U1/en [3]- https://patents.google.com/patent/CN103086280B/en https://patents.google.com/patent/CN103086280B/en [4]- https://www.google.com/search?q=telescopic+sail+patents https://www.google.com/search?q=telescopic+sail+patents [5]- https://www.maritime-executive.com/article/swedish-collaboration-unveils-world-s-largest-sail-powered-car-carrier https://www.maritime-executive.com/article/swedish-collabora...
      - curtainsforus 6y ago
        All this complicated, fiddly tech, vs. two spinning bits of metal. I know which one I'd be more confident in...
  - frederikvs 6y ago
    Perhaps they could, assuming somebody is willing to make the necessary investment to develop what you describe. However, it will probably be a complex system, and like most complex systems, it will be fairly fragile. Compare that to these Flettner rotors, which are essentially "a tube and a motor".
- mhb 6y ago
  Ships can easily be retrofitted, literally overnight, with rotors activated by an on/off switch. Kite systems seem far less practical but this can't possibly be true unless they're talking about a Sunfish. And even then, I'm skeptical. Or maybe they're using literally, as is the fashion, to mean figuratively.
  - jcims 6y ago
    Yeah that claim stinks to high heaven. You're just going to bolt these suckers down to the deck and plug in an extension cord? https://en.m.wikipedia.org/wiki/Rotor_ship#/media/File%3ACargo_E-Ship_1%2C_Emder_Hafen%2C_CN-03.jpg https://en.m.wikipedia.org/wiki/Rotor_ship#/media/File%3ACar...
    - fulafel 6y ago
      That picture is not of an auxiliary retrofited sail, but of E-Ship 1 which is all sails. The retrofitted ones are much smaller relative to ship size and are used together with main engines.
perlgeek 6y ago
Are they? How is maintenance? How sensitive are they in changes to wind? How much training does the crew need to operate either? https://en.wikipedia.org/wiki/Wind-assisted_propulsion https://en.wikipedia.org/wiki/Wind-assisted_propulsion says > In comparison to kite sails, Flettner rotors often offer considerable efficiency gains when compared to the size of a sail or kite vs. size of the rotor and prevailing wind conditions. But I'm not sure if this size comparison makes all that much sense (maybe the performance per dollar invested would be more interesting?) I'm genuinely curious about a comparison from an operator's perspective, and I also hope both approaches are being developed further.
JamisonM 6y ago
Pretty sure you need a tail-wind to use a kite system, this works in any wind.
- frederikvs 6y ago
  Pretty sure you don't need a tail-wind. Regular old sails as well as kites can be used at various angles to the wind. See e.g. https://en.wikipedia.org/wiki/Point_of_sail https://en.wikipedia.org/wiki/Point_of_sail [edit] P.S. from my understanding of the mechanism, I'm not so sure these Flettner rotors are useful in a headwind. They work by creating a pressure difference, but in a headwind, you could only create a pressure difference between the port and starbord sides, not the front and back. Unless there's some mechanism I'm missing?
  - mannykannot 6y ago
    If, by headwind, you mean sailing directly upwind, then no, they cannot do that, but they can beat to windward like a sailboat (the direction of the rotation must be reversed when tacking.) According to Wikipedia, the rotor ship Buckau could sail within 20-30 degrees of the wind, though I suspect that is a misreading of the supposed source of that data, and that 50-60 degrees is a more plausible figure. Similarly, I suspect the claim that they can sail closer to the wind than conventional sailing vessels is in comparison to square-rigged ships. https://en.wikipedia.org/wiki/Rotor_ship#Pioneers https://en.wikipedia.org/wiki/Rotor_ship#Pioneers https://books.google.com/books?id=9lqwg3iZyH0C&pg=PA656#v=onepage&q&f=false https://books.google.com/books?id=9lqwg3iZyH0C&pg=PA656#v=on...
  - odonnellryan 6y ago
    I would be surprised if a kite system could get much closer than 90 degrees to the wind.
- rightbyte 6y ago
  Aslong is the wire points forward of left and right the net force is forward right? In practice you probably want the wire +-45 degrees from the bow or something. That is where you would use a gennaker or spinnaker.
harperlee 6y ago
If I understand the concept correctly the rotor does not only work as "sail" but also as "air propeller", as you need to input energy through its rotation (that gets multiplied by the "sail" effect of the Magnus effect). So that's an apples to oranges comparison, that does not bode well for the kite (as it is "passive", not effecting any compounding of energy).
rossdavidh 6y ago
What I've read previously is that the kite systems took more training and skill to utilize, which was holding back adoption, whereas this sounds like it would be a much easier technology to use. Although, I do wonder if one could use both.
hanniabu 6y ago
I can see the ecological disaster of loose kites in the ocean already
paulryanrogers 6y ago
Kite lines can kill others nearby. There is some animosity between windsurfers and kite surfers because of this risk.
- JoBrad 6y ago
  Surely this isn’t an issue in the open sea, where tankers would mostly be using this.
- yardie 6y ago
  Kite surfers are the assholes of the sea according to some sailors. I've seen them zip in and out of navigation channels and between boats. Also had a few get dangerously close and cross our bow as we were sailing on a reach. Also, I do enjoy the sport. It's similar to endurance swimming and nearly every muscle in the body is worked. I found kitesurfers in some really remote banks and wondered how the hell did you get all the way out here.
odonnellryan 6y ago
How to kite systems work any direction into the wind? Like anything from the beam or closer?
neurostimulant 6y ago
Why not both? Flettner rotor works best when the wind is perpendicular and kite works best when the wind blows in the same direction to the ship's course.

JamisonM 6y ago

Perhaps also of interest: E-Ship 1 https://en.wikipedia.org/wiki/E-Ship_1 https://en.wikipedia.org/wiki/E-Ship_1 In service since 2010!

sradman 6y ago

From Wikipedia [1]: > A rotor ship is a type of ship designed to use the Magnus effect for propulsion. The ship is propelled, at least in part, by large powered vertical rotors, sometimes known as rotor sails. German engineer Anton Flettner was the first to build a ship that attempted to tap this force for propulsion, and ships using his type of rotor are sometimes known as Flettner ships. Container ships reduce the superstructure to enable loading but these rotor sails could possibly be used on oil tankers and bulk carriers. We don’t hear about autonomous water vessels very often, perhaps a Flettner water drone is possible. [1] https://en.m.wikipedia.org/wiki/Rotor_ship https://en.m.wikipedia.org/wiki/Rotor_ship

musingsole 6y ago
I can't recall the researchers name, only that they had some association with NCSU, but they worked heavily with wind-propelled aquatic drones. I remember a talk they gave about waiting for wind conditions and the quirks of the control system.
icegreentea2 6y ago
As noted in the article, many of these ships may need the ability to stow away the rotor to be able to pass under bridges anyways. It could still be viable for container ships.
- jdeibele 6y ago
  Looking at a picture of a large container ship there's more of a challenge siting rotors. Up high they would be in the way of cranes loading containers and might require really strong (and large) towers to hold the rotors. Built only as high as the containers, it doesn't seem like they would see any wind. How would you envision them working on a container ship? https://zeymarine.com/wp-content/uploads/2020/01/container-ships-zeymarine-blog.jpg https://zeymarine.com/wp-content/uploads/2020/01/container-s...
  - icegreentea2 6y ago
    I'll admit that I straight up don't know how the structural loading would be like - but I seems to be me that you might be able to get some sort of telescoping solution that works ok. Since you'd probably need to clear the containers anyways to get the most of the power out of the system, the lower portion of the sail doesn't need to be a rotor - just a mast for the rotor section to telescope over.

nabla9 6y ago

MS Viking Grace has rotor sail. Fuel savings are 300 tons per year from the sail. It also uses LNG fuel. In best conditions the sail can provide 20% fuel savings. In reality much less than that, but it's a small sail compared to the size of the ship. Viking Grace is a cruiseferry, so even in full capacity it's almost empty compared to a cargo ship. Maersk Pelican (tanker): 8.2% fuel saving during the first year of operation. M/V Estraden (ro-ro cargo): 6.1% fuel saving. https://www.norsepower.com/ https://www.norsepower.com/

PopeDotNinja 6y ago
I don’t see the article specifically mention slow steaming... https://en.wikipedia.org/wiki/Slow_steaming https://en.wikipedia.org/wiki/Slow_steaming Using sails to increase fuel economy seems like a no brainer, but now I’m wondering if cargo ships were ever using sails to increase their maximum safe cruising speed. Does anyone know?
- ghaff 6y ago
  Before steam they did :-) Sail died off pretty quickly once steam came in. [EDIT: Apparently in some applications much faster than others.] In the case of modern examples, I'm pretty sure it's been exclusively for fuel economy. And, until recently, the overhead associated with using sails was generally more trouble than they were worth.
  - nabla9 6y ago
    Steam ships used to have sails for a long time. Gradually the amount of sails deceased. Last ocean liners with sail assist were build in 1884. The most famous clipper (fast sail ship) Cutty Sark (later Ferreira) operated between 1870 - 1922 (17.5 kn max speed).
    - Retric 6y ago
      Yea, the original limitation was the manpower cost of manning the sails which is why they where eventually dropped. With modern systems they are almost completely automated, which makes them far more viable.

silicaroach 6y ago

Wow ... this comes up a couple of times a decade. It's like the Simpsons 'We'll build a monorail'. It's right up there with the Solar Sail scam.

burlesona 6y ago
It doesn’t seem quite like that. There appear to be a dozen or so of these ships already running, and more being converted. Perhaps this remains a small niche, but it certainly is an area of active investment and growth today.

UI_at_80x24 6y ago

This looks similar to something Jacques Cousteau implemented. On his ship the Alcyone. https://en.wikipedia.org/wiki/Turbosail https://en.wikipedia.org/wiki/Turbosail

satori99 6y ago
While they look similar, Turbo sails are not Flettner rotors. Turbo sails use an internal fan to draw air into the tubes, and vents are used to control where the air pressure drops. They do not rotate at all.

chooseaname 6y ago

This comes around every so often, with the same claim, then disappears.

geocrasher 6y ago
Indeed. It's one of those recurring engineering memes that makes the rounds every decade or so. Id be surprised if it hasn't been on the cover, or in the pages of, Popular [Science|Mechanics] at least once a decade for the past 50 years. What I personally don't understand is why these aren't themselves driven by a vertical air wind turbine. The rotational speeds aren't very high, and it seems like a no-brainer. A VAWT with variable vanes could easily be shut down in a storm.
- selimthegrim 6y ago
  Savonius turbines just aren't very efficient.

carapace 6y ago

The interesting thing about the Magnus effect is that the lift goes up with the second power of the radius of the rotor, so twice as large gets you four times as much lift. The largest Magnus effect vehicle I know of was a huge sphere with the crew cabin hanging below it from the axle. The whole sphere was the lifting body. The old OMNI magazine had an article wherein they calculated that you could put Magnus effect rotors on a bus and it would fly at (speeds as low as) 35mph. I've had plans for years now to build large flying buildings (if I can get my act together I might eventually do it) using geodesic cellular kites and the Magnus effect. (Look up Alexander Bell's kites, and Bucky Fuller's "Cloud Nine" aerial city concept.) - - - - http://www.rexresearch.com/flettner/flettner.htm http://www.rexresearch.com/flettner/flettner.htm http://www.rexresearch.com/skybow/mueller.htm http://www.rexresearch.com/skybow/mueller.htm http://www.rexresearch.com/aero/1aero.htm#thompson http://www.rexresearch.com/aero/1aero.htm#thompson http://www.rexresearch.com/aero/1aero.htm#flettner http://www.rexresearch.com/aero/1aero.htm#flettner And I found some images but not the name of the upside-down-hair-band-sphere design on this blog post: https://steemit.com/airship/@everittdmickey/magnus-effect-airship https://steemit.com/airship/@everittdmickey/magnus-effect-ai...

dragosmocrii 6y ago
Can you get your act together and build this? I'd like to see the end result, and the process.
- carapace 6y ago
  You and the other folks responding to this so positively have got me doing some soul-searching. One of my personal limiting factors on this is that there hasn't been a lot of interest so far. It's like, why perform if there's no audience? ("But, if we don't perform, in what sense do we have an act?" ~B.B. Rodríguez) So, um, wanna join my mailing list? mailto:~sforman/heliotrope.pajamas+subscribe@lists.sr.ht (Web interface: https://lists.sr.ht/~sforman/heliotrope.pajamas https://lists.sr.ht/~sforman/heliotrope.pajamas ) I'm joking, but I'm also serious: if you really want to see this happen the most useful thing you could do would be to pay attention to it. If I know folks are interested that's hella motivating, y'know? Cheers!

julosflb 6y ago

Related to this, a french startup is trying to build fleet of autonomous ships to harvest energy from ocean. They make use of flettner rotors also. https://farwind-energy.com/ https://farwind-energy.com/

deleted 6y ago

[deleted]

jeffreyrogers 6y ago

There were some planes that used this concept, but they were never commercially successful (partly because if they lose power they cannot glide to a landing like a normal plane can). I think it was used in some bomb designs as well.

russfink 6y ago

Off topic, but would a practical plan be to build a solar powered ship, with a large, miles-long towed solar panel array?

jacquesm 6y ago
You'd have to overcome the drag of that array. At a rough estimate at 1 KW / square meter for half the day it wouldn't be worth it unless you added a way for it to be pulled in at night (which is going to be pretty hard to do with solar panels which are quite fragile). On top of that, the ocean is about as hostile an environment as you could wish for and it wouldn't work anywhere near busy shipping lanes. Creative idea though, I haven't seen it before.
- m463 6y ago
  https://upload.wikimedia.org/wikipedia/commons/e/ef/Solar_Sailor.jpg https://upload.wikimedia.org/wikipedia/commons/e/ef/Solar_Sa...
  - jacquesm 6y ago
    Yes, so? That's not exactly a towed array now, is it?

williesleg 6y ago

Not gonna happen as long as those china ships belch diesel fumes underwater so we don't see them. They're killing the oceans.

Tepix 6y ago

I've already bought some chocolate that was transported by cargo sailboat Avontuur, a 100-year-old 2-master schooner. Here's some information in English : https://www.zotter.at/en/about-zotter/projects/translate-to-english-kakao-setzt-segel https://www.zotter.at/en/about-zotter/projects/translate-to-... https://timbercoast.com/en/ship/ https://timbercoast.com/en/ship/ and in German: https://www.zotter.at/das-ist-zotter/kakao-setzt-segel https://www.zotter.at/das-ist-zotter/kakao-setzt-segel https://timbercoast.com/de/schiff/ https://timbercoast.com/de/schiff/ PS: The chocolate was delicious! It's also a fantastic gift for sailors

usrusr 6y ago
Oh, there's more than one? I only know the one that ends up with https://chocolatemakers.eu/eu/de/19-schokofahrt https://chocolatemakers.eu/eu/de/19-schokofahrt getting distributed from the Netherlands across neighboring countries by cargo bike. Surely won't scale for anything other than awareness luxury gifts, but that cannot be seen as a reason to look the other way when you happen to buy luxury gifts.

BurningFrog 6y ago

Some questions after spending 10 minutes studying this: 1. These ships all seem to have two towers. Why not more? Can't they be closer for some science reason? 2. This works by spinning the towers using a motor. How do the propulsion gains compare to using the same motor power on a propeller?

frederikvs 6y ago
Regarding the two towers : if you look at the E-ship 1 [0] you'll see 4 towers - 2 in the front, 2 in the rear. There are no towers in the middle, probably because that area is intended for cargo. I presume there is also a minimum distance they need to be separated - if you look at some of the illustrations of the Magnus effect [1], you'll see a turbulent region downwind of the tower. Another tower in this turbulent region won't work as intended. This is pure speculation on my part, but perhaps most ships simply aren't wide enough to have two towers side by side (the E-ship 1 being an exception). That, and wanting to use most of the ship for cargo, explains why most ships only have 2 towers. [0] https://en.wikipedia.org/wiki/E-Ship_1#/media/File:Bateau_enercon_P9240983_part.jpg https://en.wikipedia.org/wiki/E-Ship_1#/media/File:Bateau_en... [1] https://en.wikipedia.org/wiki/Magnus_effect https://en.wikipedia.org/wiki/Magnus_effect
- shagie 6y ago
  There is a fair bit about the design and its efficiency at https://www.stg-online.org/onTEAM/shipefficiency/programm/06-STG_Ship_Efficiency_2013_100913_Paper.pdf https://www.stg-online.org/onTEAM/shipefficiency/programm/06...

kebman 6y ago

I'm just thinking out loud. Some things don't need fast shipping. Instead it needs a steady and even supply. And if a ship doesn't use any fuel, it could even serves as a kind of movable storage house. Thus I'm really looking forward for the developement of autonomous sailing ships. I really believe there's a market for them, or at least a niche within shipping.

lopmotr 6y ago
Although reducing speed and fuel usage reduces fuel costs, it increases fixed costs (you need more ships for the same throughput) as well as operating costs like crew. It might turn out to still be more expensive in the end. Then there's the problem of less certainty about price changes if you have to wait longer for the product to be delivered which leads to inefficiency (over/under-supply if mispredicted). There's also the opportunity cost of money being tied up for longer in the delay between production and consumption.
kardos 6y ago
Would they not be sitting ducks for pirates?
- stubish 6y ago
  Kidnapping and ransom seems to be the most profitable part of piracy. Insurance costs would likely go down for unmanned vessels. You could spend money on arms and mercenaries and RPG launchers and machine guns and escorts and drone squadrons through danger zones, but it is cheaper to just pay insurance. If insurance stops working, the next cheapest would be to pay pirates protection money to keep other pirates in check. https://www.forbes.com/2010/04/15/pirates-somalia-shipping-insurance-business-logistics-piracy.html https://www.forbes.com/2010/04/15/pirates-somalia-shipping-i...
- kebman 6y ago
  On the open ocean? No. That's very unlikely. Along contested shores? Yes. That's where you'd employ the coast guard or naval forces to protect the vessels. Perhaps you could even bring aboard an armed crew as needed, or employ various defences, beginning by making it harder to breach the containers, up to just about any fully automated defence system you can imagine.

Animats 6y ago

Oh, Flettner rotors again. Those keep coming around. Jacques Costeau used to have a rotor ship, the Alcyone.[1] It wasn't really worth the trouble. "In fact, we were motoring most of the time" - Alcyone's captain. [1] https://sea-to-summit.net/the-flettner-rotor-makes-a-comeback/ https://sea-to-summit.net/the-flettner-rotor-makes-a-comebac...

geoduck14 6y ago
>Those keep coming around. BAA HAHAHAHA
ipsum2 6y ago
That piece is some high quality independent journalism.
Angostura 6y ago
Been reading about them for decades, but the good news here is that there a bunch coming into service.

wefarrell 6y ago

Would like to see more about what's going on below the waterline. The challenge with any form of wind power is that the propulsion doesn't typically point forward - it's at an angle with a forward component. So on a sailboat you need a long keel (or centerboard/daggerboard) to translate the lateral propulsion into forward movement. That constricts the vessel from operating in shallow waters and causes the vessel to lean due to the opposing force under the waterline.

mmaunder 6y ago

Very little discussion here or in the article on why use these in favor of traditional sails. Looking at America’s Cup, the trend one would expect would be foils supplemented by motor and more traditional sails. I’m sure these are easier to deploy, but consider that an America’s cup boat can do 40 knots in a 12 knot breeze. Sure that’s without cargo and on a highly optimized design with hard working crew, but it does prove the remarkable efficiency of a traditional wing.

dzhiurgis 6y ago
Indeed one is for racing another for cruise. Wonder if you can make inflatable tower for lesser weight and reefing. Maybe there’s some stable design where you start foiling using motors then when you are stable - use excess power to turn rotors. AC75 boats are very unstable without foils and these things are heavy as.
throwaway0a5e 6y ago
Racing has a very different labor cost situation than commercial freight. Commercial freight will likely make use of far less energy efficient but far more labor efficient designs.
nabla9 6y ago
You can just install these rotating wings on the deck and get 5-7% increase in fuel efficiency immediately and lasts 20-30 years with minimal maintenance. The investment pays itself back in 3-8 years. Wing is obviously more efficient. The problem with the wing is the cost and size. You need to design the ship for the wing. https://en.wikipedia.org/wiki/Oceanbird https://en.wikipedia.org/wiki/Oceanbird
walrus01 6y ago
> but consider that an America’s cup boat can do 40 knots in a 12 knot breeze an america's cup boat is to sailboats what an F1 racing car is to a toyota camry. at the very high end of bespoke carbon fiber racing sailboats with crews of 8 or more, we're talking about toys for billionaire status symbols... Look at the ownership and sponsorship of the boats in this for instance: https://en.wikipedia.org/wiki/The_Ocean_Race https://en.wikipedia.org/wiki/The_Ocean_Race

dzhiurgis 6y ago

So how well does these sails point into wind and how do control lift angle?

_hl_ 6y ago
They don't. The lift is orthogonal to the wind direction, so it will be most efficient when the wind is directly from the side, with the forward force falling of with the cosine of the wind angle. There's really no way to change that with these types of sails. This is actually quite an important limitation for cargo ships, as wind directions on the large oceans are somewhat constant and mostly east-west. Hence these sails would be better for north-south routes.

AtlasBarfed 6y ago

I just wonder if massive sails that double as solar panels, and additional fold-out solar arrays, would be superior overall and lighter. But any short-term "jury rig" is valuable. And if we get enough cheap excess green energy, carbon-neutral artificial fuels might be superior too.

yread 6y ago

Slightly related: wind powered car that goes faster than the wind https://phys.org/news/2010-06-wind-powered-car-faster.html https://phys.org/news/2010-06-wind-powered-car-faster.html

comboy 6y ago
This is so counter-intuitive. I couldn't wrap my head around this and wikipedia article was more helpful to me than the article: https://en.wikipedia.org/wiki/Blackbird_(land_yacht) https://en.wikipedia.org/wiki/Blackbird_(land_yacht) Thanks for the link.
Metacelsus 6y ago
I remember this was on a Physics Olympiad question! (And I got it wrong . . .)

voldacar 6y ago

Super interesting - is a perfectly smooth cylinder most desirable? or should it be a little rough in order to better tug on the air as it spins?

cadence- 6y ago
On photos it always looks smooth. I guess you also need to make sure it doesn’t cause too much drag when not in use (for example, if you travel against the wind).
- blacksmith_tb 6y ago
  I wondered that as well - I suppose the added weight/complexity of using vanes that could be folded in (sort of like a big turbocharger) must not be worth any gains. Hard to beat the simplicity of a big tube.
hliyan 6y ago
Theoretically, there is no aerodynamic difference between a rotating, perfectly smooth cylinder and a non-rotating one. I'm not a physicist, but judging by the fact that basketballs tend to perform best in popular Magnus effect demonstrations, I'm assuming some surface texture is necessary.

dghughes 6y ago

I remember seeing this on the cover of Popular Science in 80s (maybe early 90s). A ship with a large cylinder used for propulsion from wind energy. edit: I found the issue https://www.google.ca/search?sa=X&sxsrf=ALeKk01n7hvalLGEwW3eeY3YxlQXY64mxw:1609101075935&source=univ&tbm=isch&q=%22popular+science%22+magazine+spinning+sail&hl=en&ved=2ahUKEwiIkKfQgO_tAhWpGVkFHTw9AIIQ7Al6BAgHEAo&biw=1920&bih=1086 https://www.google.ca/search?sa=X&sxsrf=ALeKk01n7hvalLGEwW3e...

colinmegill 6y ago

RC Plane leveraging Magnus effect https://youtu.be/GAqLyyg2AHk https://youtu.be/GAqLyyg2AHk

oli5679 6y ago

Naive question: is solar + battery feasible for shipping?

hliyan 6y ago
Water offers a lot more friction than air and requires a lot more energy to push a ship through than can be generated even if we cover the entire ship surface with panels. Of course, it can offset some of the energy requirements. The ship can be made wider to accommodate more panels, but that in turn increases the contact between water and hull, increasing friction. If we extend the panels over the hull, wing-like, the ship will be unstable under the windy conditions often found at sea.

mixmastamyk 6y ago

Thankful. The few times I’ve been on a ferry or cruise ship I’ve been appalled enough at the amount of pollution to not do it again. Are there any other technologies like solar, wind, or gulp nuclear, that are becoming economical?

bluquark 6y ago
It's one of the hard bits of decarbonization. The current trend is towards lighter varieties of fossil fuel (especially liquefied natural gas). In the long run, it could be fully decarbonized with hydrogen. See https://safety4sea.com/cm-shipping-decarbonization-what-does-the-future-hold/ https://safety4sea.com/cm-shipping-decarbonization-what-does...

pqdbr 6y ago

There's a great Veritasium video explaining the Magnus effect and the Flettner rotor here: https://www.youtube.com/watch?v=2OSrvzNW9FE https://www.youtube.com/watch?v=2OSrvzNW9FE The Norsepower company (which installs Flettner rotors on ships) also has a short video explaining the effect here https://www.youtube.com/watch?v=FUCShEXkpL8 https://www.youtube.com/watch?v=FUCShEXkpL8

ngcc_hk 6y ago

No picture or video ?