7 ms·

Wow, the same ship with a very unusual accident just 14 Months ago. A very bad look and hints to a deeper systemic issue that was not fixed.

by chki 6y ago

brazzy 6y ago
The cause for that accident seems to have been strong wind, which apparently makes these huge ships very hard or even impossible to maneuver when they are going slow. If true, then the "systemic issue" is only that ships are getting too big.
- lmilcin 6y ago
  Hi. Skipper here (nothing of the size of the ship in question, obviously:). Ships of ANY size are hard or impossible to maneuver when they are going slow and have a blackout. The size doesn't matter. The control surfaces only work when they move with regards to water. The ship that does not move is uncontrollable with rudder and it needs to use something else to help it maneuver. This something else can be a tugboat that rotates the ship by the force it can generate, or it can be thrusters. Thrusters aren't propulsion method and they are relatively small and can counter only so much wind.
  - speexmex 6y ago
    Isn't this why new ships are starting to have multiple 360 degree electrical drivers instead of one big propeller? I think they are called iso-pods.
    - lmilcin 6y ago
      You mean this? https://en.wikipedia.org/wiki/Azipod https://en.wikipedia.org/wiki/Azipod I think the biggest issue is complexity and resulting unreliability. On a ship that has to be in constant use for decades you want things that are simple and reliable. "The latest design, the Azipod X, incorporates these improvements, with a view to a service interval of five years, and features bearings that can be taken apart and repaired from inside the pod while the ship is harbored normally" Yeah, that pretty much sums it up. They are working on it:) Also an important factor on large vessel is fuel efficiency. You don't want anything sticking out unless absolutely necessary, so these would have to be meant for propulsion. But because of complex construction I can expect they are less efficient than just straight through axle and a huge propeller on it. I expect things like this to be useful on utility vessels of small to medium size where you don't necessarily need so much efficiency but the utility comes from being able to maneuver quickly and in various conditions.
      - gebruikersnaam 6y ago
        Harbor tugs are more commonly equipped with these: https://en.wikipedia.org/wiki/Voith_Schneider_Propeller https://en.wikipedia.org/wiki/Voith_Schneider_Propeller They're quite efficient (although maybe only for lower speeds) and provide extreme maneuverability.
      - NorwegianDude 6y ago
        They usually isn't used as the primary means of propulsion on most bigger ships. It's also not uncommon for them to be retractable. If you need a large ship at a very specific position for a week, then you definetly need it, and that is a common use case as it allows for impressively accurate control. Heck, you could avoid moorings altogether and just keep it in place without it if you wanted to.
  - Symmetry 6y ago
    For ships that have turbo-electric drive trains rather than big shafts, I wonder if it would be possible to vector the propellers somewhat for better maneuverability, the same way that rockets use gimballing engines? Probably not worth the maintenance though, with sealant and salt water considerations.
    - VBprogrammer 6y ago
      This is common on cruise ships. They spend so much of their time going in and out of port the extra manoeuvrability is worth it in requiring fewer tugs. https://en.wikipedia.org/wiki/Azimuth_thruster https://en.wikipedia.org/wiki/Azimuth_thruster
    - lmilcin 6y ago
      Anything else than straight shaft with a propeller on it is a loss of efficiency and reliability. When the fuel efficiency and reliability drive your competitiveness that is a huge issue.
      - VBprogrammer 6y ago
        Something that people perhaps don't appreciate is that typical large ships like this don't even have a gearbox (which would be perhaps 95% efficient). They use large two stroke diesel engines which can be stopped and started in reverse. They use an extra valve in the engine head to admit air for starting and have valve gear which controls the direction. Cruise ships on the other hand have electrical house loads which are almost the same as their propulsion loads. In addition to the manoeuvrability advantages this makes diesel electric drive advantageous.
        foobarian 6y ago
        Megaship engines are so fascinating. Over 100k horse power! https://www.youtube.com/watch?v=gXeBQrio4Uo&t=680s https://www.youtube.com/watch?v=gXeBQrio4Uo&t=680s
        6y ago
  - brazzy 6y ago
    I was referring to the incident in Hamburg, where there was (according to the article) no blackout, the ship had two local pilots on board and a tugboat attached. And yet, they were unable to prevent the wind from pushing them into a moored ferry they were passing.
  - candyyfl 6y ago
    Can I also ask if it’s true that such a beast like the ever given would have as little as 30% of back maneuver power compare to forward sail?
    - lmilcin 6y ago
      I have absolutely no first hand knowledge of these beasts, but some common sense here below: The engine can most likely work both directions equally. The propeller is optimized to work in forward direction, so it will have worse efficiency going in the other direction. The rotation would have to be limited when going in reverse because of cavitation (and maybe other structural limitations). That again is a result of the wrong shape of the propeller (when in wrong direction). The hull will have significantly more drag when in wrong direction. Now, engine power is defined as whatever it can put out and if the engine works the same way in both directions then power is the same also. So you can think this way: most likely it has the same power as going forward but it can't use it and whatever it can use will be much less efficiently translated into motion.
- sandworm101 6y ago
  >> The cause for that accident seems to have been strong wind The more descriptive cause is the failure to pay for adequate tug support/escort. "(Escort tug charge) = 6,600 SDR/tug" https://openjicareport.jica.go.jp/pdf/11657251_04.pdf https://openjicareport.jica.go.jp/pdf/11657251_04.pdf
  - brazzy 6y ago
    I was talking about the incident in Hamburg, not at the Suez canal. I'm not sure about Suez, but I'm pretty sure you don't get to choose whether and how many tugs you need at Hamburg; the port will decide that. The article cites a tug captain as saying that they have a very limited ability to react to big ships being pushed by strong wind. They compare it to driving a care on ice.

Wow, the same ship with a very unusual accident just 14 Months ago. A very bad look and hints to a deeper systemic issue that was not fixed.

by chki 6y ago

Wow, the same ship with a very unusual accident just 14 Months ago. A very bad look and hints to a deeper systemic issue that was not fixed.

brazzy 6y ago

The cause for that accident seems to have been strong wind, which apparently makes these huge ships very hard or even impossible to maneuver when they are going slow. If true, then the "systemic issue" is only that ships are getting too big.

lmilcin 6y ago
Hi. Skipper here (nothing of the size of the ship in question, obviously:). Ships of ANY size are hard or impossible to maneuver when they are going slow and have a blackout. The size doesn't matter. The control surfaces only work when they move with regards to water. The ship that does not move is uncontrollable with rudder and it needs to use something else to help it maneuver. This something else can be a tugboat that rotates the ship by the force it can generate, or it can be thrusters. Thrusters aren't propulsion method and they are relatively small and can counter only so much wind.
- speexmex 6y ago
  Isn't this why new ships are starting to have multiple 360 degree electrical drivers instead of one big propeller? I think they are called iso-pods.
  - lmilcin 6y ago
    You mean this? https://en.wikipedia.org/wiki/Azipod https://en.wikipedia.org/wiki/Azipod I think the biggest issue is complexity and resulting unreliability. On a ship that has to be in constant use for decades you want things that are simple and reliable. "The latest design, the Azipod X, incorporates these improvements, with a view to a service interval of five years, and features bearings that can be taken apart and repaired from inside the pod while the ship is harbored normally" Yeah, that pretty much sums it up. They are working on it:) Also an important factor on large vessel is fuel efficiency. You don't want anything sticking out unless absolutely necessary, so these would have to be meant for propulsion. But because of complex construction I can expect they are less efficient than just straight through axle and a huge propeller on it. I expect things like this to be useful on utility vessels of small to medium size where you don't necessarily need so much efficiency but the utility comes from being able to maneuver quickly and in various conditions.
    - gebruikersnaam 6y ago
      Harbor tugs are more commonly equipped with these: https://en.wikipedia.org/wiki/Voith_Schneider_Propeller https://en.wikipedia.org/wiki/Voith_Schneider_Propeller They're quite efficient (although maybe only for lower speeds) and provide extreme maneuverability.
    - NorwegianDude 6y ago
      They usually isn't used as the primary means of propulsion on most bigger ships. It's also not uncommon for them to be retractable. If you need a large ship at a very specific position for a week, then you definetly need it, and that is a common use case as it allows for impressively accurate control. Heck, you could avoid moorings altogether and just keep it in place without it if you wanted to.
- Symmetry 6y ago
  For ships that have turbo-electric drive trains rather than big shafts, I wonder if it would be possible to vector the propellers somewhat for better maneuverability, the same way that rockets use gimballing engines? Probably not worth the maintenance though, with sealant and salt water considerations.
  - VBprogrammer 6y ago
    This is common on cruise ships. They spend so much of their time going in and out of port the extra manoeuvrability is worth it in requiring fewer tugs. https://en.wikipedia.org/wiki/Azimuth_thruster https://en.wikipedia.org/wiki/Azimuth_thruster
  - lmilcin 6y ago
    Anything else than straight shaft with a propeller on it is a loss of efficiency and reliability. When the fuel efficiency and reliability drive your competitiveness that is a huge issue.
    - VBprogrammer 6y ago
      Something that people perhaps don't appreciate is that typical large ships like this don't even have a gearbox (which would be perhaps 95% efficient). They use large two stroke diesel engines which can be stopped and started in reverse. They use an extra valve in the engine head to admit air for starting and have valve gear which controls the direction. Cruise ships on the other hand have electrical house loads which are almost the same as their propulsion loads. In addition to the manoeuvrability advantages this makes diesel electric drive advantageous.
      - foobarian 6y ago
        Megaship engines are so fascinating. Over 100k horse power! https://www.youtube.com/watch?v=gXeBQrio4Uo&t=680s https://www.youtube.com/watch?v=gXeBQrio4Uo&t=680s
        6y ago
- brazzy 6y ago
  I was referring to the incident in Hamburg, where there was (according to the article) no blackout, the ship had two local pilots on board and a tugboat attached. And yet, they were unable to prevent the wind from pushing them into a moored ferry they were passing.
- candyyfl 6y ago
  Can I also ask if it’s true that such a beast like the ever given would have as little as 30% of back maneuver power compare to forward sail?
  - lmilcin 6y ago
    I have absolutely no first hand knowledge of these beasts, but some common sense here below: The engine can most likely work both directions equally. The propeller is optimized to work in forward direction, so it will have worse efficiency going in the other direction. The rotation would have to be limited when going in reverse because of cavitation (and maybe other structural limitations). That again is a result of the wrong shape of the propeller (when in wrong direction). The hull will have significantly more drag when in wrong direction. Now, engine power is defined as whatever it can put out and if the engine works the same way in both directions then power is the same also. So you can think this way: most likely it has the same power as going forward but it can't use it and whatever it can use will be much less efficiently translated into motion.
sandworm101 6y ago
>> The cause for that accident seems to have been strong wind The more descriptive cause is the failure to pay for adequate tug support/escort. "(Escort tug charge) = 6,600 SDR/tug" https://openjicareport.jica.go.jp/pdf/11657251_04.pdf https://openjicareport.jica.go.jp/pdf/11657251_04.pdf
- brazzy 6y ago
  I was talking about the incident in Hamburg, not at the Suez canal. I'm not sure about Suez, but I'm pretty sure you don't get to choose whether and how many tugs you need at Hamburg; the port will decide that. The article cites a tug captain as saying that they have a very limited ability to react to big ships being pushed by strong wind. They compare it to driving a care on ice.