5 ms·

Why would this be better than sails?

fulafel 9y ago
You mean compared to traditional sailboat sails? There don't seem to be products that would add them to traditional cargo ships or ferries. Probably blocked by the crew skills and effort needed to operate and maintain them, as well as more invasive structural demands placed on the ship. The only other recent sail boost attempt is kite based approach: https://www.treehugger.com/cars/cargo-ship-with-kites-first-trans-atlantic-trip-a-success.html https://www.treehugger.com/cars/cargo-ship-with-kites-first-... A cynic might of course also propose that you can't get public research money or patents for a product based on traditional sail...
- Someone 9y ago
  ”as well as more invasive structural demands placed on the ship.” Why would that be the case for a sail that gives the same fuel reduction? Are these rotors less impacted by sudden gusts of high wind speed than traditional sails?
  - Sharlin 9y ago
    A rotor sail is just a tube that rotates. Regular sails need complicated rigging.
    - Someone 9y ago
      Why? Without additional arguments on the table, I would think the force exerted on the wind-catching structure would be equal between sails and these rotors, for equal efficiency gains. That load has to go somewhere. Rigging is a way to do so with traditional materials, but nowadays, a sturdier mast without rigging is possible. (Rationale: if the ‘mast’ hidden in these rotors can be made strong enough, we can also create a mast holding a traditional sail taking the same load)
      - newnewpdro 9y ago
        Have you ever been sailing?
        Someone 9y ago
        Does that matter? It’s all physics. If you think my logic is incorrect, point out where.
        newnewpdro 9y ago
        Rotor sails are relatively insensitive to foul weather and wind direction. If you had any experience with sailing, especialy on the high seas in a variety of conditions, you'd have a much better understanding of the problems. If you have the means to go out on the sea in a sailboat, I highly recommend it. Especially for someone with a STEM background, it's actually a quite interesting activity.
      - Sharlin 9y ago
        Rigging is not about strength. It's about adjusting the shape, size, angle, and trim of the airfoil that is the sail. Sails are not just vertical parachutes, those would be useless in anything except straight tailwind. Sails are vertical wings. They can provide propulsion (lift) even in headwind.
juhanima 9y ago
Modern, mechanical sails have been tried, too. The Japanese Nippon Kokan built ships like this in the 1980's: http://collections.rmg.co.uk/collections/objects/66022.html http://collections.rmg.co.uk/collections/objects/66022.html Apparently the savings in fuel consumption were ~10%, so not really worth the hassle. Viking Grace's new tube may actually be more effective if the 20% of fuel savings can be trusted, besides being simpler to operate and less intrusive.
newnewpdro 9y ago
Weather and wind direction variance prevents traditional sails from being practical. They barely even need a crew on these ships, and can pretty much ignore the prevailing wind direction. There's insufficient economic incentive to incur the significant costs of operating with sails. There's a reason the age of sail is in the past, it couldn't even compete with steam.

You mean compared to traditional sailboat sails? There don't seem to be products that would add them to traditional cargo ships or ferries. Probably blocked by the crew skills and effort needed to operate and maintain them, as well as more invasive structural demands placed on the ship. The only other recent sail boost attempt is kite based approach: https://www.treehugger.com/cars/cargo-ship-with-kites-first-trans-atlantic-trip-a-success.html https://www.treehugger.com/cars/cargo-ship-with-kites-first-... A cynic might of course also propose that you can't get public research money or patents for a product based on traditional sail...

Someone 9y ago
”as well as more invasive structural demands placed on the ship.” Why would that be the case for a sail that gives the same fuel reduction? Are these rotors less impacted by sudden gusts of high wind speed than traditional sails?
- Sharlin 9y ago
  A rotor sail is just a tube that rotates. Regular sails need complicated rigging.
  - Someone 9y ago
    Why? Without additional arguments on the table, I would think the force exerted on the wind-catching structure would be equal between sails and these rotors, for equal efficiency gains. That load has to go somewhere. Rigging is a way to do so with traditional materials, but nowadays, a sturdier mast without rigging is possible. (Rationale: if the ‘mast’ hidden in these rotors can be made strong enough, we can also create a mast holding a traditional sail taking the same load)
    - newnewpdro 9y ago
      Have you ever been sailing?
      - Someone 9y ago
        Does that matter? It’s all physics. If you think my logic is incorrect, point out where.
        newnewpdro 9y ago
        Rotor sails are relatively insensitive to foul weather and wind direction. If you had any experience with sailing, especialy on the high seas in a variety of conditions, you'd have a much better understanding of the problems. If you have the means to go out on the sea in a sailboat, I highly recommend it. Especially for someone with a STEM background, it's actually a quite interesting activity.
    - Sharlin 9y ago
      Rigging is not about strength. It's about adjusting the shape, size, angle, and trim of the airfoil that is the sail. Sails are not just vertical parachutes, those would be useless in anything except straight tailwind. Sails are vertical wings. They can provide propulsion (lift) even in headwind.

juhanima 9y ago

Modern, mechanical sails have been tried, too. The Japanese Nippon Kokan built ships like this in the 1980's: http://collections.rmg.co.uk/collections/objects/66022.html http://collections.rmg.co.uk/collections/objects/66022.html Apparently the savings in fuel consumption were ~10%, so not really worth the hassle. Viking Grace's new tube may actually be more effective if the 20% of fuel savings can be trusted, besides being simpler to operate and less intrusive.

newnewpdro 9y ago

Weather and wind direction variance prevents traditional sails from being practical. They barely even need a crew on these ships, and can pretty much ignore the prevailing wind direction. There's insufficient economic incentive to incur the significant costs of operating with sails. There's a reason the age of sail is in the past, it couldn't even compete with steam.