Kite pulling of commercial vessels meets the requirements of delivery days and times. It is therefore to be expected that this may hinder its expansion as long as storage problems (in the broadest sense) remain, especially as these vessels are generally huge.
To my way of thinking, this falls into the âAll Ya Gotta Do IsâŠâ category of energy innovation. âAll ya gotta do isâ add 5 smaller ships, each connected to pull the original larger ship. each with its own energy kite system. The problem I see with this approach is the complication and cost of adding and operating these extra âtugboatsâ, not to mention the inefficiency - more hulls and mass to drag through the water. You give up the basic idea of a ship able to power itself. If a kite can fully propel a âtugboatâ, with so much extra power as to pull a larger ship too, why not just pick a smaller ship and pull it with the kite?
This is where I ask the question and imagine what the answer(s) might be:
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Could it be that the variability of the pulling force of a crosswind kite flying a pattern might cause problems for the shipâs stability? Could it be that only a kite much smaller than required to actually power the ship is acceptable from a ride-quality standpoint?
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Could the pulsating pull present a problem?
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Could the kite cause the ship unacceptable amounts of roll?
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Could there be structural problems of trying to exert that much force on the top (deck) of the ship, rather than a driveline solidly mounted to the hull, near the bottom of the ship?
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Is it possible that the contribution of the kite toward propulsion is so small that the only justification that can be made is to exaggerate a very small contribution toward propulsion, whereby a more appropriate kite-to-ship size match would reveal how little is being gained?
It seems that such basic questions are not being asked, let alone explained. Seems like part of âthe syndromeâ where people can make claims that later seem outrageous, or just incorrect, and nobody is supposed to question anything that is supposedly âgreenâ or that symbolizes a green feeling in some possible way.
I donât know what the answer is - I don;t see any reason a kite could not pull a boat of appropriate size compared to the kite, but that is one of those cases of âthe devil is in the detailsâ.
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One of the advantage of kite is that it could be used for refit of existing boats. These boats have no daggerboards, so for a similar kite size you would have more drift with a smaller boat.
Another (bad or good ?) reason is bigger boats tend to be faster (Froude limit). The absolute savings for a faster boat can be higher than for a slower boat (as power saved is to the first order the product of kite forward pull by boat speed).
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OK hereâs an idea: Contact yacht dealers and marinas, and find a sailboat that has a broken mast. Convince the boat owner to buy a kite instead of a new mast. Mount the kite where the mast previously emerged, leaving the stump of the mast in place to help handle the pulling force of the kite.
You also have to get rid of the useless keel weight. And youâd better attach the kite to where were the shroud to deal with a pulling force.
I think @dougselsam has a good point. A simplest starting point may be to use a sailboat as-is. Even with the mast intact. Then you may find that controlling the kite is enough of a challenge to keep you busy for yearsâŠ
Syroco is taking a different approach in my opinion, making a very specialized vessel. But I think this approach also means that getting to a generally useful thing is far away. There will probably be steps that are hard to automate properly.
Retrofitting a sailboat turns this upside down. The first job is to implement something so automated as to be generally useful. Once that hurdle is passed, you could decide if you want to go the route of world records, leisure sailing or cargo shipsâŠ
All I was saying is a sailboat already has a centerboard - keel - whatever you want to call it. That would help from having the boat side-slipping. A sailboat is obviously engineered to be pulled by the wind, more than a motorboat. Did someone mean use a motorboat? Why? The broken mast thing is just so you have the stub still running from the bottom of the boat thru the top to add structural integrity. If not a broken mast, cut the mast off yourself, from any old sailboat. I was not really thinking about the Syroco flying yacht concept with that post, just the simple(?) kite-pulls-boat idea. To me, it seems sensible to choose a kite and a boat of a size that allows the kite to actually PULL the boat, NOT just âhelp a littleâ. I really donât understand why nobody is doing it, given the success of kitesurfing. Maybe everybody is busy staring at their phone or posting nonsense on the internet! Otherwise, should we say it is now proven that a kite-powered boat is not doable, after ten years of talking about it? Seems like nobody is even trying. Why? Thereâs gotta be a sailboat with a broken mast somewhere. 
You have many such projects at relatively some scale. I try to keep up to date (but I know it is not) a list here Robokite: SynthĂšse kiteboat. When you need automation, the increase in development cost pushes toward bigger boats with more promises of Return On Investment
My question is, if a Skysails kite can contribute, say, 20% of the propulsive power for a given ship, why donât they install the same kite on a smaller ship - maybe one fifth of the tonnage (size) or maybe even one sixth, assuming larger ships are more efficient? Of course the ship would still need engines for all the times the wind is not right, and for maneuvering in traffic and harbors, but why not show how a kite can pull a ship, instead of being just a virtue-signalling decoration? Isnât there a route somewhere that is mostly crosswind, where such a kite could really prove itself? I just donât see why there isnât a more appropriate size match. Itâs like if a wave surfer had a little kite that just helped pull him along a little bit - who would want to bother with such a partial solution? âHey, look at my toy kite! It helps a little bit! Pretty cool, huh?â Can a kite pull a ship or not? Seems like the answer is âNo, a kite cannot pull a shipâ.
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In my view there are two chances of this happening in the foreseeable future: Zero, none, and a teensy possibility that indirect kite propulsion by way of on-board kite generated electricity driving a conventional propeller may work. Whoops thatâs three, but youâll get the drift. But this is not to say itâs not worth trying. [âŠ]
As well as unacceptable reliability because of wind variability, there is a technical reason why kite power cannot be useful for commercial shipping- unless container ships change to submarine form so as to reduce their above-water-line drag profile. Aerodynamic drag is the killer. A largish container ship, with containers stacked up 15m and more above deck level can have side area above the water line of about 5000sq.m. Even if itâs kite is also 5000sq.mâs (5 x larger than any kite thatâs yet been built, but probably possible), the shipâs superstructure drag will reduce the efficiency of the kite/line/ship system (measured by lift to drag ratio, L/D) to less than one, and options for upwind courses will fade away. This will be so even if this kiteâs stand alone L/D is 5, (a little above current state of the art for traction kites).
When other other inefficiencies, such as hydrodynamic drag, are also allowed for, even if the apparent wind strikes the shipâs superstructure at 45degrees rather than the worst case of beam-on, upwind sailing will still not be achievable to any bankable extent. Additionally, the usefulness of kite power for container ships is restricted because they travel FAST- and customers will not generally accept slow because the cost of holding stock while in delayed transit exceeds the extra cost of cranking up a few more knots. Fuel use per tonne km is perhaps 70 times better for a container ship than for a truck or train- theyâre VERY fuel efficient. Under kite power, it canât be expected that a commercial ship will be able to achieve sustained travel at wind speed or above.
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Straight talk from one of the âKite GodsââŠ
Superior in what way? The only people i see using single skin kites is in snow kiting for the small packing size. From what i heard it is less maneuverable, not good jumping with and there must be a reason why racing kites also still is high aspect dual layer foil kites. And most brands are not even making single skin kites. It is mostly just Flysurfer Peak, and Ozone Explore. Or are you talking about LEI kites as single skin?
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One thing Iâve wondered about is the scenario he describes, where a larger kite is used to function more as a standard-type of sail, holding a relative position, rather than a smaller kite flying a higher-speed pattern. He makes a good point about how much air resistance all those containers already have. The immense size of such a kite seems like it might present difficulties, whether for launching, storage, handling, weight, strength, safety, and cost. Also mentioned are all the additional drag forces of the ship holding its position against the kite!
Anyway, such a larger kite holding a constant position was what I had originally envisioned way back in the 1980âs when I was first learning CAD, with my first CAD drawing being a kite pulling a boat.
I would point out, as an aside, a reason I seem to have a more critical, less forgiving eye for wannabe wind energy âsolutionsâ:
My reason for being interested in wind energy was based on an actual interest in wind energy technology, based on it being an economical clean energy solution requiring no constant fuel supply, rather than a knee-jerk reaction to some temperature story. We didnât have the temperature story back then, other than it was generally acknowledged that the next glacial phase of the current ice-age was about due, or overdue. Besides that backdrop, nobody was cris-crossing weather concerns with energy concerns. Back then, you had to have actual interest in the technology itself as a motivating factor. So in my case, and Iâm sure many others, the main thing was not some symbolic virtue-signaling. We had to actually understand and be interested in the technology itself.
I grew up building our own kites, and sailing a sailboat. I would imagine the amount of horsepower an engine would require to power our sailboat at the same speed as the sail, and realized there was truly a lot of power available from the sail
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The moment I really got enthusiastic about wind energy was still in the 1960âs as we toured the hydroelectric power plants at Niagara Falls, and I saw these immense generators lined up in a huge room that looked like a set from a science-fiction movie, and was told they provided our electricity 70 miles away, and powered most of our part of New York State, requiring no fuel whatsoever! And I was told our electricity was unusually cheap, due to no requirement for fuel.
That was when, knowing a sail could provide a few horsepower, I saw we could do the same thing with wind, and started learning more about wind turbine design and functionality. Combining that with the habit we had developed of building our own kites, the AWE aspect seemed a natural fit. It was a typical thing for me as a kid to wonder âwhen will all the âscientistsâ become as smart as I already am as a kid?â
Back then, scientists were still trying to say all the craters on the moon and other planets were volcanic, NOT impact craters. I would scratch my head wondering how âall the expertsâ could be so stupid that even I as a little kid could out-think them. To me, anyone who had read a science-fiction book knew the craters were from meteor strikes. I guess it was too much for the âscientistsâ to handle.
Going back in time before I was alive, itâs well-documented that âofficial scienceâ declared in no uncertain terms âStones cannot fall from the sky!â Next time someone tells you âall the expertsâ agree on something, think twice.
When I say single skin in this context, I meant single skin as an inflated LEI vs a ram air kite. A single skin kite eg Flysurfer Peak would be in the «ram air» camp though technically it is a single skin also.
I wont dig i to why LEI were superior for kitesurfing, I think history speaks for itself. Foils are niche market today. But who knows, if some time in the future foil kiting and snow kiting is the mainstream of kitesurfing, LEI may become the niche kite design.
It all depends on whats best for a particular ise, I guess
Ok i misunderstood then. I have not heard people use the term single skin for LEI kites, just for single skin foil kites.
The reason people use LEI kites for kitesurfing is mainly because they float and can float on the water for as long as you want (while with closed cell foil kites you want to get it up again as fast as possible when you crash it so it does not lose to much air).
High aspect two layer foil kites has superior performance compared to LEI kites when it comes to speed. And that is why they dominate kite racing and is often separated into their own class if you have a mix of riders with LEI and foil kites in a race to keep it more fair. And the high aspect two layer foil kites is also superior to LEI kites in low wind.
LEI kites has traditionally been more maneuverable than foils. But some of the low aspect foil kites is catching up here. I have tried the Ozone Hyperlink foilkite and it turns just as fast as a similar sized LEI kite. It is just that it is so freaking expensive, or i would have bought it.
I think its more complicated. Racing is really a small niche in kitesurfing. Most kitesurfers just enjoy riding back and forth with an added jump here and there. Though foils may be more aerodynamically efficient, kitesurfers are like conosieurs that would mostly be very specific about which kite has a better feel. The benefit of a LEI kite of course is the stiffness of the frame and the fact that the skin is completely flat, which again means less deformation in flight.
Still about Wisamo:
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Thanks for that breath of fresh air, Pierre. Looks very nice, good thinking with the telescopic deployment. Are they inflated with air?
Not sure how much it would actually help, considering it is of a similar size to other structures on deck.
The ship operators seem to like the fact that they donât need people from Michelin onboard to operate it (maybe in comparison to kites) and it is capable if staying out of the way of normal operating activities.
The website and another video for additional explains:
INFLATABLE
As the telescopic mast unfolds, the fabric inflates via an integrated fan system. Thanks to our low-pressure technology, the wingsail keeps a completely symmetrical shape, avoiding any wind deformation and effectively absorbing shocks.
TELESCOPIC
A telescopic mast consisting of several segments raises and lowers automatically. Its fully retractable design facilitates loading and unloading operations as well as passage under bridges.
AUTOMATED
A digital control panel allows you to raise or lower the wingsail automatically, without any human action. Sensors detect the wind direction and force to maximize performance and make it completely safe and easy to use.
See also the Woopy, which is an inflatable wing using a similar technology. Perhaps its ability to be quickly deflated could be a way for reel-in phase, or rather for easier takeoff, landing, and also storage at the station.