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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?

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We were in 10051 and had a lot of vibration at strange times. Really felt it on the sofa. It didn't ruin our crossing.

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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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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.

 

 

Sent from my iPhone using Forums

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I was annoyed by the vibration in 11120 during a transatlantic crossing in January 2017.

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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.

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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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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.

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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)

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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.

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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/default/files/30mw-queen-mary-case-history.pdf

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Thanks for all the very interesting insights. I have now booked cabin 9009 so should be well away from any possible vibrations.

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Wow, so much great information. Having booked an aft 11 deck portside room, I'm unsure to try to change it or ride the waves so to speak, all good in any case, Thanks 

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On 11/21/2018 at 8:43 PM, chefandthedancer said:

Wow, so much great information. Having booked an aft 11 deck portside room, I'm unsure to try to change it or ride the waves so to speak, all good in any case, Thanks 

 

We’ve just come across in 11070 and that was fine.

It depends upon what you are expecting of course.

I’m very sensitive to noise and vibration, when we are on our canal boat it just needs someone nearby to start an engine to charge their batteries and I’m “off on one”! But somehow, when we’re on a liner it seems very natural and doesn’t seem a problem.

 

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On a TA last year on the QM2 my wife and I were fortunate enough to have had dinner with the Deputy Captain on the second night out. Having already noticed these vibrations in our cabin (12022), I asked what the cause might be and even suggested some of the various ideas listed in the above posts. The Deputy Captain told me that what we were actually feeling were vibrations transmitted through the ship from the very large commercial washers and dryers used onboard. He said this is one of the most common questions he is asked. 

 

Jack

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I'm afraid I'm going to disagree with the Deputy Captain on this one.  All of the commercial washers and dryers onboard are mounted on springs, or they would tear themselves out of the ship when unbalanced (much like your washer at home can sometimes start "walking" when unbalanced since it is not fastened to your floor).  And, typically, the laundries do not run 24/7.  If the washers and dryers were so poorly mounted that you could feel the vibrations around the ship, then the vibrations from the diesels would overpower them by a couple of orders of magnitude.  If they can mask the engine vibration using flexible mounts, they certainly can mask the vibrations from the laundry.

 

I'm pretty sure the senior staff had a chuckle over this at the next day's morning meeting.

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On 8/18/2018 at 1:13 PM, Bigmike911 said:

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/default/files/30mw-queen-mary-case-history.pdf

 

While increased speed might cause an increase in the vibrations associated with the azipods or the sea state induced vibration there would not be any additional vibration induced by the gas turbines.  Marine gas turbines operate within very tight tolerances and high vibrations within the engine, which are measure in mils and the tolerances are in the single digits, are causes for automatic shutdown of the engine.  Marine gas turbines can be loud, if inside the operating enclosure, but they are exceptionally smooth when in operation.  In fact, it is a necessary condition of a gas turbine engine that it not vibrate excessively, otherwise the engine will literally eat itself.

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18 minutes ago, cougaraz said:

 

While increased speed might cause an increase in the vibrations associated with the azipods or the sea state induced vibration there would not be any additional vibration induced by the gas turbines.  Marine gas turbines operate within very tight tolerances and high vibrations within the engine, which are measure in mils and the tolerances are in the single digits, are causes for automatic shutdown of the engine.  Marine gas turbines can be loud, if inside the operating enclosure, but they are exceptionally smooth when in operation.  In fact, it is a necessary condition of a gas turbine engine that it not vibrate excessively, otherwise the engine will literally eat itself.

Additionally, the gas turbine enclosures are shock mounted to reduce the high frequency vibrations (of small amplitude as you say), from the structure of the ship.

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1 hour ago, chengkp75 said:

Additionally, the gas turbine enclosures are shock mounted to reduce the high frequency vibrations (of small amplitude as you say), from the structure of the ship.

Good point, totally forgot about the mounts.  I have spent enough time inspecting them that I should know better!

 

Love the fact that you are able to bring so much technical expertise to the boards.  I speak ship pretty well, but the difference between the Navy and the commercial world, especially the cruising world, is usually a bridge too far for me.

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with so much machinery running there is bound to be noticeable vibrations on the ship some places worse than others. Mid-ship deck 3 [ ?] near the elevators rumbles[not props] ,while other places are smooth .We once had a cabin that the floor vibrated but about a half hour after each docking it stopped once again not propeller .Another time there was a generator failure and you could feel it smooth out even when the turbines kicked in it was smooth abet they kicked up air movement [intakes] at the stern .....bottom line it is mostly luck of the draw and timing if you get a vibrating cabin ....imho ......nothing has disturbed my sleeping on board ......even the morning kid zone "commute" in the hall

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During a TA, I awoke in the middle of the night when I sensed a loss of any vibration.  I checked the information page on the television.  Sure enough, we were slowing down from 19 knots to 10 knots.  I woke DH up and told him that we were slowing.  He was sleeping like a baby.

 

 A few minutes later, there was an announcement in the passage way by a younger officer's voice for emergency crews to report to the ECR.  DH, an airline captain rolled over and said not to get excited unless you heard the Commodore's voice on the PA.  Five minutes later, we heard the Commodore's voice on the PA asking crew to report to the ECR.  That got his attention.  We stayed awake for a little while waiting for the call to man the lifeboats.  It never came and we went back to sleep.

 

The next morning, we determined that one of the pods had a malfunction and it had to be dealt with.  That was the reason for the loss of vibration.  The Commodore explained at the noon announcement that it was better to muster the entire crew to deal with such a development than to chase getting the right person in place.  Good headwork.  

 

The moral of the story is true of both airplanes and ships.  Don't start to worry until there is no vibration.  Silence is not a good thing. 

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One Christmas while we were at dinner in Britannia it all went quiet and dark. The ship was without power for several minutes. I noticed that the POS terminals for ringing up passengers' drinks remain we powered up.

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11 hours ago, Underwatr said:

One Christmas while we were at dinner in Britannia it all went quiet and dark. The ship was without power for several minutes. I noticed that the POS terminals for ringing up passengers' drinks remain we powered up.

probably the same trip we were on........iirc after leaving a port and during dinner. I was concerned enough to finish our food outside ,that is when i found out about the turbines 

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For those of us who book steerage, midships cabins can have a lot of vibration. On 5, I think it's the range from 5140 to 5150--look for those ominous big blank spaces on the deck plan! 

 

And to add to chengkp75's excellent explanation of vibrations and resonance, does anyone remember QE2's E elevators? At the right speed, the natural frequency of the elevator shaft matched the vibrations, and those elevators shook.

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