“What differentiates it from other wind solutions,” says Bernatets, “is that the wing is not just pulled by the wind and countered by the ship.” Instead, it flies in figure-of-eight loops, which multiply the pulling effect of the airflow to give what he calls “crazy power.”
“Plus, we fetch the wind 300 meters above the sea surface, where it’s 50% more powerful,” adds Bernatets. The combination “explains why the power is tremendous for a system that is very compact, simple on the bow of the ship, and can be retrofitted on any ship, not just new ships,” he says.
“What differentiates it from other wind solutions,” says Bernatets, “is that the wing is not just pulled by the wind and countered by the ship.” Instead, it flies in figure-of-eight loops, which multiply the pulling effect of the airflow to give what he calls “crazy power.”
That’s an innovation over square-rigged ships, sure, but not so much over fore-and-aft-rigged ones (where the sails act like aerofoils).
The chain for the anchor can be much heavier as it doesn’t have to be suspended by something flying in the wind when being drawn out. The water also acts as a shock absorber (as do the individual links) if the chain were to break.
The point is that people working on ships already know how to take precautions around lines that can break with enough force to kill a person. They establish zones on the ship that people can’t be in when the lines are being used. This is a very old problem that was solved a long time ago.
They’re not a joke, they’re a product called Seawing, made by a French company. They’re being being actively tested and can be retro fitted to existing vessels rather than requiring a new design.
Correct, I think they were saying it was being reported on as if it was a joke. Not being taken seriously as a good step towards reducing carbon emissions.
I’m not sure who they wrote that headline for. “Giant kites” is one thing, but what really stood out to me was that they added on the “reduces carbon emissions” as if that part would be unexpected. Like the whole point of these giant kites is to pull the ships and reducing carbon emissions is icing on the cake, rather than sails coming back because they are a carbon-neutral method of propulsion.
And they’re a lot more advanced than traditional sails.
Traditional sails only work with surface winds, which are relatively weak. These giant kites can go much higher and take advantage of much stronger and more reliable winds at higher altitudes.
The thing about those big kite sails is the wind has to be coming from pretty much astern for them to work; if the ship is sailing into even a quartering headwind they’re of no use.
There’s a technology…I forget what they’re called, some kind of turbine, where you have a couple of tall spinning cylinders on the deck, which interact with the wind in such a way to provide thrust for the ship, this is mechanically simpler, fewer ways it can go wrong, you can just hinge them down and secure them in a storm or to pass under bridges, and they can drive the ship in quartering headwinds.
I’ve seen kiteboarders able to go in pretty much whatever direction they want as long as there is wind. These kites are the same thing but bigger.
That said, idk if cargo companies really want to be adding distance to the trip by tacking back and forth into the wind. My impression is that they want to get there ASAP and screw the fuel consumption.
They will slow down to conserve fuel, because when you’re burning it at the quantities these ships do you’re talking millions of dollars per voyage, and especially if you’re going to end up waiting in line like you do at American ports…why hurry?
Because faster trips means more trips per year. Even if the margins per trip is lower due to increased fuel consumption, quarterly revenue is higher. Even if significant time is waiting at port.
That said, I don’t work in the logistics industry, so I don’t have the number to say how much the difference would be.
By why hurry I mean, why rush to cross the Pacific ocean only to have to wait at anchor for a dock to become available in Los Angeles harbor?
There’s an old law, been on the books since the 19th century, that requires ships traveling between US ports to be US registered and be crewed by mostly US citizens. This causes a problem in the modern day because…imagine you’ve got one of those gigantic containerships leaving Asia for the US, the ship is owned by who gives a shit and the crew was chosen practically at random from citizens of the world. In a sane world, you could plan the trip to visit several ports along the US coast, dropping off cargo from Asia at each where it’s most convenient, and loading cargo that’s going to your next port of call. Well unless the ship is American, this is illegal, which makes the United States a complete fucking problem, which is why tthere are just…containerships hanging around outside US ports waiting to offload ALL of their cargo whether it makes sense or not, taking on whatever’s at this particular port, and then leaving the Western hemisphere again.
Huh, I assumed the queue was first-come-first-served, are you telling me that these ships reserve a time at a port in advance? That’d make sense, and in that case you’re right it only makes sense to arrive there just in time for your reservation. But if it’s FIFO then it still makes sense to get there ASAP even if you’re waiting, because arriving later doesn’t make the wait shorter.
Wrt USA being a problem, I feel like that’s probably true of every industry lol
Sails don’t billow into the wind. They are set at an angle to it. Just enough to inflate them, creating an airfoil. The remaining wind blows across the airfoil, creating “lift” (like vertical airplane wings) that pulls the boat along more efficiently. That’s why sail boats can actually go faster than the wind.
From this photo, the wind is blowing almost parallel with the sails.
The type of sail you’re referring to is ‘bermuda-rigged’, like the smaller ones at the front of the boat in the picture. The big ones in the middle of the picture are ‘square-rigged’ which are really only good for sailing downwind.
Maybe, although I haven’t seen anyone doing it. I’m guessing you would need a sheet to each corner to trim the sail tightly enough which I think would be too much of a headache for the crew. Worth thinking about tho, especially in a castaway situation!
To clarify, it’s not that the square rigged sails themselves can be used to sail upwind. I was talking about how you could rotate the yard so that the sails could continue to catch a wind. But, for sailing upwind, the square rigged sails wouldn’t help much. It’s that square rigged sailing ships had staysails which would let them sail upwind slightly. Apparently a fore-and-aft rigged sailing ship can sail within 20 degrees to the wind, while a square rigged ship could only do about 60 degrees.
In a castaway situation, I wonder what the best idea would be. Try an experimental modification of an existing sail to give you better mobility? Or be thankful you have a working sail and accept limitations on how much you can steer? Ignoring the sails though, my guess is that in a shipwreck, one of the most likely to be damaged things will be the keel, and trying to sail without a good keel would suck.
FYI, the main innovations of these kite sails compared to traditional sailing ships are that it doesn’t need masts that get in the way of cargo handling and that it requires fewer crew. In other words, it’s not faster or anything; it’s just cheaper.
Modern cargo ships are so huge traditional sails wouldn’t provide enough force to push them around. Neither will these kites, mind you. But, supplemental energy will still be a bonus, and a kite can reach higher and sit in faster, more stable winds.
Hmm i feel like there it was a case of working against the ocean whereas here I think it is working with the wind so it shouldn’t be THAT bad… but who knows…
You underestimate the force of wetted surface area resistance. The sail area needed to move a modern cargo ship at the snail’s pace of old sailing ships would be unmanageably large. You simply couldn’t hold enough sail area to get them near their current speeds. These hybrid sail concepts are nice, but all they do is save some fuel.
The longer the ship, the more masts you can add, so the length doesn’t really matter. What would matter is the width, but I don’t see why the sail surface area couldn’t scale with the ship’s surface area. Sure, it would be a huge amount of sail, but it’s a huge amount of steel.
The resistance from the wetted surface area scales up a lot more quickly than the wind force does. You’d have to completely redesign the hull shape to try to compensate, significantly reducing internal cargo volume and still not getting the ship above a few knots of speed…
Digging up my old naval architecture notes I’m reminded that I was a bit wrong in pointing out the real problem. It’s the speed that causes an exponential increase in required effective horsepower, not the displacement. And it’s exponential by a cube factor, so doubling the speed typically requires about 8x the power.
So, you can make a giant ship move under wind power, but you can only ever get so much power from the wind, limited by how big you can effectively make your sails and all the wind turbulence issues that arise from that. Sailing ships never went very fast, so that speed is never going to get much above 4-10 knots, as horsepower requirements above that just start to skyrocket. And there are few merchants who will accept that kind of speed when the competition will get their goods to market 2-3x faster using engines. Even goods that can survive a longer voyage will lose out on profit to those that get to the best market the quickest.
The really neat thing about this is that the largest factor in creating this drag at higher speeds is actually the waves created by moving. You end up trying to sail upstream, essentially, as you outpace your wake. There’s a certain point where, if you’re going fast enough, the resistance goes back down a bit as you ride your own wake, but beyond that it’s a vertical line. There are some real clever things you can do to get around this with lighter sailboats, but anything hauling cargo is just too bogged down to try it.
It’s the speed that causes an exponential increase in required effective horsepower, not the displacement
Is any of this dependent on the size of the ship?
limited by how big you can effectively make your sails and all the wind turbulence issues that arise from that
Is this a bigger problem with big sails? I can imagine with a really big airfoil sail it might be hard to get the ideal angle / shape. But, if it’s a square-rigged ship it seems like it would be less sensitive to turbulence because it’s not an airfoil?
Sailing ships never went very fast, so that speed is never going to get much above 4-10 knots
And a modern cargo ship goes about 20 knots, right? But, does that mean that you could get maybe 16 knots out of the engine and 4 from the wind? Or is it that the wind can supply 1 MW of power, which is enough to move at 4 knots, but if you want to move at 20 knots you need 30 MW of power, so the wind would only supply about 3% of what you need, so it might not be worth it for all the added complexity?
Even goods that can survive a longer voyage will lose out on profit to those that get to the best market the quickest.
And, because petroleum-based fuel is very cheap because you don’t have to pay for the impact it causes, you can get an incredibly powerful engine that doesn’t cost an absurd amount to run. So, the additional cost to ship things at 30 knots using vast amounts of very dirty diesel is low enough that it’s still worth it?
You end up trying to sail upstream, essentially, as you outpace your wake
Yeah, I read about that, and how at one speed your bow and stern are both at wave peaks so it’s very efficient, but if you go faster your bow is a peak and your stern is a trough and that’s the worst situation.
If you wanted to go post-apocalypse mode though, is there any size-scaling thing related to ships that means that big ships are impossible to scale as sailing ships? Or if you can scale the sails up with the size of the ship, could you have an enormous post-Panamax sailing ship with absurd sized sails and a ridiculous sized keel that would cruise around at the same speed as the cargo sailing ships of old? Imagine seeing one of the biggest of the big cargo ships of today but rigged for sail power only. Either with a crew of 5000 post-apocalyptic refugees-turned-sailors handling the absurdly complex sails, or, with a computer in charge with hundreds of different motors all making continuous tiny adjustments to keep dozens of sails all set up perfectly.
Is any of this dependent on the size of the ship? Yes, but there are various factors and trade offs. A factor of your total resistance is your viscous resistance which scales geometrically with your wetted surface area. You can make your ship shape a rounded box, which maximizes cargo for surface area, but then causes more hydrodynamic drag. Or you can make the hull shape a tapering hydrofoil to solve that, but increasing the surface area underwater if you try carrying the same cargo. The choice to go with ends up depending on what the ship is carrying. For instance, oil tankers will go with the rounded box because their cargo is practically the same density as the water so they have to carry it low. Container ships can afford to stack their cargo very high and can even play games with arranging it by weight, so the can get away with a slight, or slender hull below water without sacrificing much cargo. In trade they can get more speed. Bulk cargo ships will fall somewhere in between. The draft and beam required for ports visited and canals traversed all factor heavily into the choice as well.
Is this a bigger problem with big sails? I can imagine with a really big airfoil sail it might be hard to get the ideal angle / shape. But, if it’s a square-rigged ship it seems like it would be less sensitive to turbulence because it’s not an airfoil?
They actually still work as airfoils, ideally. The best way to extract the most energy from the wind is the angled sail working as an airfoil. This, of course limits how far apart the sails can be. I imagine it also places some limits on overall size based on the balance of more sails vs bigger sails. The height will be limited by the righting moment of the ship, so you can’t just make them crazy tall without also needing to make the ship so wide it can’t fit into port, though I guess you could play games with outriggers to push that boundary.
And a modern cargo ship goes about 20 knots, right? But, does that mean that you could get maybe 16 knots out of the engine and 4 from the wind? Or is it that the wind can supply 1 MW of power, which is enough to move at 4 knots, but if you want to move at 20 knots you need 30 MW of power, so the wind would only supply about 3% of what you need, so it might not be worth it for all the added complexity?
24-34kts is what I worked with. I’m not sure exactly how the energy would be combined, but this is essentially what they’re doing with these sail kite ships. It only saves a few percent of fuel, but that is nothing to sneeze at. I’ve seen various articles about the project with the kite since 2007 all claiming various savings, but it’s supposed to pay for itself in a year or two, I’ve heard. It certainly feels worth adding, to me, but I don’t manage a shipping line.
And, because petroleum-based fuel is very cheap because you don’t have to pay for the impact it causes, you can get an incredibly powerful engine that doesn’t cost an absurd amount to run. So, the additional cost to ship things at 30 knots using vast amounts of very dirty diesel is low enough that it’s still worth it?
Heavy fuel oil makes diesel seem squeaky clean by comparison, but it makes up for it by being even cheaper and containing more energy. The energy is so great, that all the fuel and engine space take up a relatively small amount of volume compared to the cargo. And you can cram that fuel into all the strangely shaped parts of the hull that would otherwise just contain ballast water. They actually do put work into cleaning up the exhaust, at least in reputable shipping firms. There are exhaust scrubbers that pull NOx, SOx, and particulates out at the same time as they recover waste heat. The output is still pretty foul, but the scrubbers take a big chunk out without much negative impact.
If you wanted to go post-apocalypse mode though, is there any size-scaling thing related to ships that means that big ships are impossible to scale as sailing ships?
Just the speed and overall size. Like, worst case you could always build a wind energy storage system to capture power from wind turbines, save it in power cells of some kind, then release it in bursts.
I don’t see why you couldn’t get traditional speeds doing square rigs on a repurposed container ship, but maneuvering would be hard. I don’t know much about tall ship design, but I think they have to be able to turn very well to really tack with the wind.
If you wanna go real apocalypse mode to though, just cobble together a crude nuclear reactor in the boilers of a steam ship and steal some fuel. You’ll probably die from cholera before the radiation gets you, anyway!
I still really want us to go in for nuclear cargo ships though. The NS Savannah is so cool. I’ve gotten to tour her a couple times in Baltimore. They want to turn her into a public museum ship with a reactor mock-up you can walk into, but need a few million in funding to properly decommission the real one.
I don’t see why you couldn’t get traditional speeds doing square rigs on a repurposed container ship, but maneuvering would be hard. I don’t know much about tall ship design, but I think they have to be able to turn very well to really tack with the wind.
Yeah, turning would be a massive challenge, and forget trying to sail upwind. But, the size of the ship would make them really stable, so they might be able to get sails up into winds that are more predictable and steady. On the other hand, they would require a massive keel, and that would limit them to really deep waters. Maybe in a sail-punk scenario you’d see trans-continental sailing ships being offloaded at offshore platforms, and smaller ships would then shuttle the goods to the mainland.
I still really want us to go in for nuclear cargo ships though. The NS Savannah is so cool. I’ve gotten to tour her a couple times in Baltimore. They want to turn her into a public museum ship with a reactor mock-up you can walk into, but need a few million in funding to properly decommission the real one.
Yeah, I understand the reluctance to have a nuclear reactor on a ship – on anything that moves really. But, when you need megawatts of power to move something, you really have to think about the safety of the reactor vs. the fact that pollution from petroleum-based ships actually does kill people too, just in a much less accountable way. The Russians have a nuclear-powered icebreaker, I think. If ships are going to keep getting bigger and bigger, it makes sense to me that eventually more than just military ships will have reactors. Maybe we’ll have to wait for the climate catastrophe to get worse, or for reactors to be less feared.
So, I got that information from a different Lemmy comment, and on the spur of your contradiction I went looking myself. My search results are flooded with mostly useless news articles (they went to tell stories, not relay technical information). Regardless, the most ambitious claim I’ve seen is to reduce emissions by up to 90% for a ship design that can’t handle shipping containers and is about 1/4 the size of the largest ships being produced today.
Don’t get me wrong, I want this to happen. In fact, I would ban carbon-fuel shipping today, if I could make it happen. That being said, I don’t think we’ll ever get back to 100% wind power.
The sail kite project has had claims of up to 10% fuel savings for about 20 years, now.
It’s all moot when we should just be focusing on figuring out practical nuclear shipping. It’s the only way to meet or exceed our current standard and be carbon-free. The NS Savannah proved it could be profitable ages ago, and that without any economy of scale to reduce costs.
Why can I only think of that journey to the center of the earth movie with the kite sail and had the one dude browsing google with the PSP. Why can I only remember two things from that movie?
Modern cargo ships are so huge traditional sails wouldn’t provide enough force to push them around.
Believe it or not, “proportionality” is a thing. You make the ship bigger, you make the sails bigger to match. Simple! Granted, previously, making sails bigger was limited by the weight of the things when hoisted by men operating manual winches, but now we’ve got motors now to solve that, and higher strength-to-weight ratio materials, too.
Point is: I maintain that, in principle, you could make a post-Panamax sailing ship – even a traditional fully-rigged one – if you really wanted to, and it would be capable of sailing at hull speed on wind power alone. It’s just that they don’t want to for reasons unrelated to technical feasibility.
It would be really interesting to see a fully rigged ship with dozens of sails where the rigging was pulled by motors and controlled by computers rather than humans. It would also be interesting to see what they could do with modern materials. Nylon sails, carbon fibre masts, steel lines, etc.
Having said that, I would bet that a real modern cargo ship would probably use fancy solid wing-style sails.
A bigger challenge would be sourcing enough shantymen to be feasible. I’m not sure that the world has sufficient production capacity to provide the necessary rum for more than a handful of ships.
You also need vastly less sail area and the things are more reliable because wind gets quite a bit stronger and reliable at 100-300 metres up. The system actually isn’t new. AFAIU main reason for it not getting wide-spread adoption is that shipping lines, not ship owners, pay for fuel.
And the load on its sheets is enormous. Oh boy can it cause a problem if anyone makes a mistake handling it! Now imagine the load from the kites proposed. I wonder if that is even feasible with today’s materials.
Edit: did some reading around. So it seems at current level the system can be used as a supplementary propulsion saving some fuel. Ahoy, mates, we are back and our sails are higher than ever!
When it comes to material stresses the sails can always be scaled down, but off the top of my head kevlar and zylon would be good candidates for getting the biggest, toughest sail in an economic fashion.
If you want to go down a related rabbit hole take a look at the sails used in regattas. The technology and money that goes into them is ridiculous.
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