4 ms·

It is common practice to let vessels drift freely if no anchorage is available (congestion, depth of water) or if there's no intention to anchor the vessel. If

by tawm 8y ago

It is common practice to let vessels drift freely if no anchorage is available (congestion, depth of water) or if there's no intention to anchor the vessel. If the orders for the vessel weren't clear, it's very much possible that it was drifting a few miles off the Chinese coast.

freddie_mercury 8y ago
The linked article includes a chart showing the vessels movements mapped down to every few minutes. Looking at that picture it is hard to imagine its path is caused by drifting. It is clearly moving in a circle. You can't tell from the static map in the article but if you check other marine vessel tracking websites you can see that it is moving in a counterclockwise circle at a fairly steady rate. I suppose that could be caused by an anchor and drifting but it seems more likely to me (as an uninformed idiot, though I've been in anchored boats before and don't remember them moving in circles because of it) that it is under power (albeit not very much).
- theresistor 8y ago
  Swinging about an anchor under the force of wind or currents would tend to make a circular arc.
  - poooogles 8y ago
    Same for tides.
  - dmurray 8y ago
    Normally back and forth on the downwind or down-current side of the circle, though. The chart shows it completing several circles.
    - windows_tips 8y ago
      The chart shows most of the data points on a small portion of the arc.
    - theresistor 8y ago
      Reversals are completely normal for cyclic tidal currents or sea breeze / land breeze cycles.
- EdwardDiego 8y ago
  > Looking at that picture it is hard to imagine its path is caused by drifting. It is clearly moving in a circle Eddies are a thing. https://oceanservice.noaa.gov/facts/eddy.html https://oceanservice.noaa.gov/facts/eddy.html
- dghughes 8y ago
  Huge heavy ships need many kilometers to stop and then to get back up to speed more time and burn lots of fuel. If there was a possibility the ship was going to be allowed to dock in a certain window of time it would make sense to just keep sailing. I see it like big rig trucks who don't want to stop at stop signs since the need a lot of energy and rowing through gears to get back up to speed. Just my wild Saturday morning pre-coffee theory.
duxup 8y ago
Considering how long it can take to get the engines started up on a big ship... drifting aimlessly seems a bit risky.
- jacquesm 8y ago
  Engine operation is independent of propulsion. You can have the engine idling and the screw in neutral.
  - rnd90 8y ago
    You can, but it's not always that simple :) Some ships have a direct drive. So the moment the engines start, the prop shaft is turning. These ships will control thrust via Controlled Pitch Propellers. Basically the pitch of the propeller blades are controlled hydraulically and the steeper the pitch, the more the blades cut through the water and the more thrust generated. CPP systems allow ships to use shaft generators for electrical power at sea. The engine's revs are constant (to keep the electrical frequency the same) and power is changed via setting the propellers pitch. Some ships have drive trains which let you clutch engines in and out, but you wouldn't run them for long periods of time de-clutched. The engines do not like being run at an idle load for long periods of time (whether direct drive or clutched), you get loads of crud building up as they don't properly warm up. Also you are burning fuel and increasing their hours (planned maintenance is usually based around running hours). So you wouldn't generally drift and idle. You would shut the engines down and keep them on immediate notice. A lot of modern ships are diesel electric. So the props are driven by large electric motors. So in this case, you can stop and start propulsion instantly (as long as you have enough generators running and connected to the switchboard)
    - jacquesm 8y ago
      I think 'screw in neutral' adequately addresses variable pitch screws. The proper term in windmills and airplanes is 'feathered', I don't know what to call that state in a boat.
      - 8y ago

by tawm 8y ago

freddie_mercury 8y ago

The linked article includes a chart showing the vessels movements mapped down to every few minutes. Looking at that picture it is hard to imagine its path is caused by drifting. It is clearly moving in a circle. You can't tell from the static map in the article but if you check other marine vessel tracking websites you can see that it is moving in a counterclockwise circle at a fairly steady rate. I suppose that could be caused by an anchor and drifting but it seems more likely to me (as an uninformed idiot, though I've been in anchored boats before and don't remember them moving in circles because of it) that it is under power (albeit not very much).

theresistor 8y ago
Swinging about an anchor under the force of wind or currents would tend to make a circular arc.
- poooogles 8y ago
  Same for tides.
- dmurray 8y ago
  Normally back and forth on the downwind or down-current side of the circle, though. The chart shows it completing several circles.
  - windows_tips 8y ago
    The chart shows most of the data points on a small portion of the arc.
  - theresistor 8y ago
    Reversals are completely normal for cyclic tidal currents or sea breeze / land breeze cycles.
EdwardDiego 8y ago
> Looking at that picture it is hard to imagine its path is caused by drifting. It is clearly moving in a circle Eddies are a thing. https://oceanservice.noaa.gov/facts/eddy.html https://oceanservice.noaa.gov/facts/eddy.html
dghughes 8y ago
Huge heavy ships need many kilometers to stop and then to get back up to speed more time and burn lots of fuel. If there was a possibility the ship was going to be allowed to dock in a certain window of time it would make sense to just keep sailing. I see it like big rig trucks who don't want to stop at stop signs since the need a lot of energy and rowing through gears to get back up to speed. Just my wild Saturday morning pre-coffee theory.

duxup 8y ago

Considering how long it can take to get the engines started up on a big ship... drifting aimlessly seems a bit risky.

jacquesm 8y ago
Engine operation is independent of propulsion. You can have the engine idling and the screw in neutral.
- rnd90 8y ago
  You can, but it's not always that simple :) Some ships have a direct drive. So the moment the engines start, the prop shaft is turning. These ships will control thrust via Controlled Pitch Propellers. Basically the pitch of the propeller blades are controlled hydraulically and the steeper the pitch, the more the blades cut through the water and the more thrust generated. CPP systems allow ships to use shaft generators for electrical power at sea. The engine's revs are constant (to keep the electrical frequency the same) and power is changed via setting the propellers pitch. Some ships have drive trains which let you clutch engines in and out, but you wouldn't run them for long periods of time de-clutched. The engines do not like being run at an idle load for long periods of time (whether direct drive or clutched), you get loads of crud building up as they don't properly warm up. Also you are burning fuel and increasing their hours (planned maintenance is usually based around running hours). So you wouldn't generally drift and idle. You would shut the engines down and keep them on immediate notice. A lot of modern ships are diesel electric. So the props are driven by large electric motors. So in this case, you can stop and start propulsion instantly (as long as you have enough generators running and connected to the switchboard)
  - jacquesm 8y ago
    I think 'screw in neutral' adequately addresses variable pitch screws. The proper term in windmills and airplanes is 'feathered', I don't know what to call that state in a boat.
    - 8y ago