Mary vibrations


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#1
Near Windsor UK
238 Posts
Joined May 2002
Thinking of a round trip from Southampton next year. Princess Grill. I read of quite strong vibration in cabins between stairwells b and c. Deck plans don't identify stairwell letters, but cabin 10119 has been mentioned. Any advice?
#3
Pennsylvania
6,522 Posts
Joined Jul 2010
Last Christmas we were in 11012. We felt a certain vibration there. It was more surprising given the deck height rather than bothersome.

The stairwells are numbered from the front, A-D. C and D don't go as far up as A and B. 10119 is between C and D.
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Past:
Queen Mary 2: 8 cruises
Queen Victoria: 2 cruises

ms Amsterdam: 1 cruise
ms Eurodam: 1 cruise
Caribbean Princess: 1 cruise
Carnival Pride: 1 cruise
#4
Canada
70 Posts
Joined Dec 2013
When I have been on the QM2 I have always sailed on deck 11 - usually towards the back. Interestingly sometimes there has been vibrations and others not. That said the vibrations have never been annoying. I am curious as to what causes them and to why they are there on some trips and not the other.


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#6
Maine or at sea
13,959 Posts
Joined Feb 2013
Vibrations can be caused by a few things. One is the infamous "azipod shimmy", which is caused primarily when the ship is in following seas, and to keep a constant heading, the azipods that steer will "sweep" back and forth, port to starboard and back, as the following seas swing the stern one way or the other. This constant sweeping of the propellers causes the water flow into and out of the propellers to sweep across the flat hull above the pods, and the ship vibrates horizontally. More noticeable the further aft you go. This problem was so severe on the QM2 at sea trials, that they had to take the ship back into drydock and add a "skeg" or vertical portion of hull between the port and starboard azipods for more lateral stability.

The other vibrations are because the ship is a large "sounding box" like a violin or guitar. Externally produced vibrations, like the blades of the propellers passing the hull at the top of their rotation, or periodic waves striking the ship, can cause the ship's hull to vibrate. Due to the complex nature of the hull structure, various areas will have different natural frequencies, and so will start to vibrate at different times when different frequencies are induced. So, combinations of propeller speed, wave period, wave direction relative to ship's course, and the like will vary the input vibrations, and consequently an area might vibrate in the morning and not in the evening, if the environmental conditions change. Similarly, one cabin may vibrate at one speed, in a given weather condition, but not another cabin down the passageway, but if the propeller speed changes by a few rpm's, the second cabin may vibrate while the first does not.
#8
Canada
61 Posts
Joined Jun 2018
Originally posted by chengkp75
Vibrations can be caused by a few things. One is the infamous "azipod shimmy", which is caused primarily when the ship is in following seas, and to keep a constant heading, the azipods that steer will "sweep" back and forth, port to starboard and back, as the following seas swing the stern one way or the other. This constant sweeping of the propellers causes the water flow into and out of the propellers to sweep across the flat hull above the pods, and the ship vibrates horizontally. More noticeable the further aft you go. This problem was so severe on the QM2 at sea trials, that they had to take the ship back into drydock and add a "skeg" or vertical portion of hull between the port and starboard azipods for more lateral stability.

The other vibrations are because the ship is a large "sounding box" like a violin or guitar. Externally produced vibrations, like the blades of the propellers passing the hull at the top of their rotation, or periodic waves striking the ship, can cause the ship's hull to vibrate. Due to the complex nature of the hull structure, various areas will have different natural frequencies, and so will start to vibrate at different times when different frequencies are induced. So, combinations of propeller speed, wave period, wave direction relative to ship's course, and the like will vary the input vibrations, and consequently an area might vibrate in the morning and not in the evening, if the environmental conditions change. Similarly, one cabin may vibrate at one speed, in a given weather condition, but not another cabin down the passageway, but if the propeller speed changes by a few rpm's, the second cabin may vibrate while the first does not.
Good insights chengkp75 ...
Harmonics are mysterious and wondrous things!

We recently had a new-build small vessel that kept destroying drive belts to the alternator PTO, and we were investigating misalignment, bad bearings, all kinds of things. Turned out in the end to be a faulty fuel injector that introduced a harmonic at certain engine RPMs which manifested in a local vibration that destroyed the drive belt. Seemed very counter-intuitive to me.

I also sailed on an icebreaker that would experience harmonics in shallow waters at certain engine rpms, where vibrations made the whole ship feel like it was driving over a corduroy road or a series of speed bumps. Vary the speed by a few revs and the problem would disappear.

I'm joining the QM2 next week in Brooklyn, but I don't anticipate too many vibrations to bother me on Deck 12 forward. Should they occur, I'm only a scant few metres from the wheelhouse so I'm guessing the OOW will feel them too and make the appropriate adjustments.
PJ
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QM2 - Roundtrip TransAtlantic Crossing M832A - Aug-Sept 2018

Professional Mariner, Shipbuilding Project Director, SAR Guy
Queen Mary 2 - Roundtrip Transatlantic Crossing (M832A
#9
Maine or at sea
13,959 Posts
Joined Feb 2013
Originally posted by VintageCCG
Good insights chengkp75 ...
Harmonics are mysterious and wondrous things!

We recently had a new-build small vessel that kept destroying drive belts to the alternator PTO, and we were investigating misalignment, bad bearings, all kinds of things. Turned out in the end to be a faulty fuel injector that introduced a harmonic at certain engine RPMs which manifested in a local vibration that destroyed the drive belt. Seemed very counter-intuitive to me.

I also sailed on an icebreaker that would experience harmonics in shallow waters at certain engine rpms, where vibrations made the whole ship feel like it was driving over a corduroy road or a series of speed bumps. Vary the speed by a few revs and the problem would disappear.

I'm joining the QM2 next week in Brooklyn, but I don't anticipate too many vibrations to bother me on Deck 12 forward. Should they occur, I'm only a scant few metres from the wheelhouse so I'm guessing the OOW will feel them too and make the appropriate adjustments.
PJ
Yes, combine the reflected pressure wave from the propellers bouncing back from the shallow bottom to the ever present blade passage pressure wave against the hull, and you have ample opportunities to match the natural harmonic frequency of the hull.

I have been standing in an engine room, feeling very minimal vibrations, and watching a small free-standing tank rock back and forth so violently that I thought it would rip the welds out. A bit of cross-bracing helped.
#10
Hamburg
439 Posts
Joined May 2013
Thanks for the insight.
One question, if you don‘t mind:

How much do the exhaust pipes generate the vibrations on a cruiseship?

We always try to stay away as far as possible from the areas, where they obviously go up till the top deck.
Our observation is, that usually the aft half of the ship are more prone to vibrations than the front - regardless the vibrations that are created by propulsion and engines (though it may be difficult to differentiate engine noise from exhaust vibrations as they are generated at the same area)
#11
Maine or at sea
13,959 Posts
Joined Feb 2013
Originally posted by Yoshikitty
Thanks for the insight.
One question, if you don‘t mind:

How much do the exhaust pipes generate the vibrations on a cruiseship?

We always try to stay away as far as possible from the areas, where they obviously go up till the top deck.
Our observation is, that usually the aft half of the ship are more prone to vibrations than the front - regardless the vibrations that are created by propulsion and engines (though it may be difficult to differentiate engine noise from exhaust vibrations as they are generated at the same area)
The exhaust would produce no vibration. Unlike a car's exhaust, the gas does not flow in pulses caused by the sequential firing of the cylinders. The exhaust gas flows from the engine's cylinders to a turbocharger, where the flow is balanced out to a smooth, constant flow. However, the diesel engines are typically located under, or slightly forward of the stack where the exhaust pipes go up, so these will generate vibration. While there is machinery located virtually the entire length of the ship at the bottom in the engineering spaces, most of the vibration causing equipment (diesel engines, and propellers) are located from midships aft.
#12
Magnolia, Texas
1,487 Posts
Joined Jul 2009
Queen Mary 2 has in addition to the diesel engines below, two gas turbine engines (think jet plane engines) in the enclosure below the funnel on deck 12. These are not always in use to save on fuel costs, but if the Captain needs to make up time he will use them. I would imagine that could cause some vibrations to passengers in deck 11 staterooms. For those interested here is a link to a story on the engines .https://www.geaviation.com/sites/def...se-history.pdf
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