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Vibrations in aft staterooms


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This also happened on the Nieuw Amsterdam and the captain explained this is caused by both wave action and the "flattened" new ends of the ship - (duck bill shape I think).

 

So ships with aft cabins now that also have this extended water line "rear-end" addition, apparently get this vibration action during certain maneuvers from the waves and wind. It is temporary, and has nothing to do with the function of the engines. At least that is the way I thought it was explained to me.

 

Hopefully chenengkp can offer a better explanation.

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Didn't notice it on Koningsdam, but have noticed it on other HAL ships, only when docking or pulling away.

 

And Koningsdam has a larger "duck bill".

 

Maybe they were able to design around this problem for the Konigsdam, and there may be times when the wind and waves don't reach critical mass if there is a faulty "duck bill" tail end..

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During docking and un-docking procedures, the azipods are being rotated for directional control, and the props are not synchronized, meaning one is rotating slightly faster than the other. That is the reason for the slight vibration felt during close maneuvering near docks. Once the ship is clear of the docks, the props are rotating in sync and no vibration is felt. This will date me a bit, but flying back in the 50's and 60's in prop-jet aircraft, the pilot may not have the 2 or 4 props in sync and you feel the vibration in the cabin until they are synchronized.

On the aft cabins, the very short vibration felt during docking is a minor inconvenience compared to the huge balconies and beautiful views.

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In an aft SC stateroom on the Westerdam, I felt no unusual vibration. I did experience a rather odd cork-screw type movement that was slight but not disturbing when the sea and wind conditions caused this I was told.

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We have been in an aft balcony (my favorite!) on both Zuiderdam and Eurodam and felt the vibration.

At first I thought it was odd, but got used to it quite fast.

On the Eurodam, I was already prepared. Its kinda weird, but neat!

It once woke us up at 0200 just after leaving San Blas islands post Panama Canal transit. Turns out they had to med evac someone off the ship in a nearby port and the ship was preparing to sail onward to Fort Lauderdale.

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In an aft SC stateroom on the Westerdam, I felt no unusual vibration. I did experience a rather odd cork-screw type movement that was slight but not disturbing when the sea and wind conditions caused this I was told.

 

That's the one risk for me in an aft cabin. I don't mind pitching, I can put up with rolling, but corkscrewing gets to me. We had the windiest Caribbean cruise I can remember this winter. Several days of winds 35-40 knots against the side of the ship at just the right angle, and one day, the corkscrewing got to me. So I went up to Promenade deck and sat midships in the fresh air and I was fine.

 

Deck chairs were all taken, but I had a pool towel, so I just sat on the deck to read. A man whose wife and daughter "would be back soon" must have felt guilty for chair hogging. When he left a few minutes after I sat down, he said I could have his lounger, but insisted the wife and daughter were coming back for theirs. Never did see them, but it was nice of him to give me his lounger when he went inside.

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Here's some explanation I posted on a Carnival thread about the same thing yesterday.

 

http://boards.cruisecritic.com/showpost.php?p=52818747&postcount=19

 

This can happen on any ship, and depends on the weather, or on the port in question.

 

And as I noted in this post, it is not that the props on azipods are not turning in synch that causes vibrations when maneuvering into/out of port, it is the change in waterflow direction, especially when going astern, where you have the hull blocking clean water flow.

 

Ducktails have little or no benefit to vibrations, they are added for two reasons. The most important is to prevent "dynamic squat", where a ship tries to ride up onto it's bow wave, forcing the stern deeper into the water, and changing the hydrodynamics of the hull. The hollow ducktail is additional buoyancy just above the normal waterline, so as the ship tries to squat, this additional buoyancy forces the stern up again, leveling the ship. The second, and lesser reason is to lengthen the waterline of the ship, because the natural hull speed of a ship (the fastest you can push a hull through the water without requiring exorbitant power) is related to the waterline length.

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