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.
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.
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.
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.
You’re assuming everything scales linearly, which is not necessarily accurate. The square-cube law rains on many people’s parades.
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.
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.
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.
Hoist the mainsail and shiver me timbers.
They are literally kites—not sails. I’ve never seen a sail flying 100 ft above a ship before.
https://en.wikipedia.org/wiki/Spinnaker
When a vessel is running (meaning moving in the same direction as the wind) it can fly a spinnaker, which is just a kite on short lines.
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.
https://en.m.wikipedia.org/wiki/Parasailing
…
parasail
“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).
A 300m line holding turbulent sail kite would never have the chance getting tangled or snapping and killing someone when it whips back
Yeah there’s similar problems for the ropes that anchors are attached to as well, so they shouldn’t be using those either.
And what is wrong with taking stress off the engines? I hate how they report this like it is a joke, because it is still a solid step.
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.
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.
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.