Aft veranda K'dam - how do you sleep if at all?

[MogeyMan]

I found it impossible. Nav. deck. The vibration was insane, almost shook me out of bed, it was like BIG thrust then shake shake shake. A few seconds respite and then repeat all night long.

 

Anyone else? I so looked forward to it, but never again. I had to resort to sleeping medication.

[CruiserBruce]

Slept with no problem for 3 weeks on KDam last March in an aft Neptune Suite. Heard a noise once, IIRC.

[kenevenpar]

Never noticed it. 10 nights Nov. 2017. DW is an extremely light sleeper; she would have noticed it. YMMV

[Homosassa]

Yes, you will feel motion in cabins aft or forward. The amount will depend on the ship's speed and sea conditions.

 

The motion you are describing sounds like yaw which is the motion a ship makes around a vertical axis as waves hit from off center or the side (not rolling).

 

Book cabins that are low and amidships to minimize any motion.

[CruiserBruce]

Yes, you will feel motion in cabins aft or forward. The amount will depend on the ship's speed and sea conditions.

 

The motion you are describing sounds like yaw which is the motion a ship makes around a vertical axis as waves hit from off center or the side (not rolling).

 

Book cabins that are low and amidships to minimize any motion.

 

The OP is talking about vibration...not sure that equals rolling or similar.

[Daisyloo]

We were petty far aft on deck 6 for 10 days and never had an issue. We personally have found the Koningsdam to be the most stable (least motion) of any ship we have sailed on. We have done 3 cruises on her, once mid-ship, once far forward and once far aft, all with no issues.

[3rdGenCunarder]

I found it impossible. Nav. deck. The vibration was insane, almost shook me out of bed, it was like BIG thrust then shake shake shake. A few seconds respite and then repeat all night long.

 

Anyone else? I so looked forward to it, but never again. I had to resort to sleeping medication.

 

Oh, yeah. It was trying to sleep near a construction site. We had winds and some waves, but I've had worse sea conditions than we had (last week of January) without the banging I experienced on K'dam, including aft corners on Vistas. One day i stood on our balcony and watched the water. When a wave broke at the stern, it caused a shudder that ran through the whole aft end. And if it was windy, the ship had a sort of shimmying motion at the back.

 

I spoke to people who were forward or midships and they had none of these issues. So it's definitely a stern thing. Don't know if there's anything they can do about it. I love corner afts, but never again on this ship!

 

We were petty far aft on deck 6 for 10 days and never had an issue. We personally have found the Koningsdam to be the most stable (least motion) of any ship we have sailed on. We have done 3 cruises on her, once mid-ship, once far forward and once far aft, all with no issues.

 

The funny thing is we didn't have a lot of pitching or rolling. No corkscrewing, either. We had a nice straight wake. Just the bouncing and banging.

[Homosassa]

The OP is talking about vibration...not sure that equals rolling or similar.

 

Yaw does feel like a vibration or oscillation.

[chengkp75]

Oh, yeah. It was trying to sleep near a construction site. We had winds and some waves, but I've had worse sea conditions than we had (last week of January) without the banging I experienced on K'dam, including aft corners on Vistas. One day i stood on our balcony and watched the water. When a wave broke at the stern, it caused a shudder that ran through the whole aft end. And if it was windy, the ship had a sort of shimmying motion at the back.

 

I spoke to people who were forward or midships and they had none of these issues. So it's definitely a stern thing. Don't know if there's anything they can do about it. I love corner afts, but never again on this ship!

 

 

 

The funny thing is we didn't have a lot of pitching or rolling. No corkscrewing, either. We had a nice straight wake. Just the bouncing and banging.

 

This is the infamous "azipod shimmy", which is caused by the azipod propellers wake sweeping back and forth while steering to maintain heading. Much pronounced when a following sea. Cruise ship sterns are not designed to handle following seas very well, due to the wide, flat area required above the pods, and the sharp break to the vertical. All designed to maximize azipod efficiency, but not ride.

 

Also, due to the squared off sterns on these ships, following seas will "slam" more than ride up and over the sea. Also, in following seas, the stern has a whole lot of reserve buoyancy in that squared off stern, so it will rise more than the bow does, and this brings the rapidly turning propellers closer to the surface, and causes more vibration. When seas are from ahead, not only the finer entry of the bow, but the bulbous bow tends to keep the ship from "climbing its bow wave" and keeps the stern and the propellers deeper in the water.

[Florida_gal_50]

This is the infamous "azipod shimmy", which is caused by the azipod propellers wake sweeping back and forth while steering to maintain heading. Much pronounced when a following sea. Cruise ship sterns are not designed to handle following seas very well, due to the wide, flat area required above the pods, and the sharp break to the vertical. All designed to maximize azipod efficiency, but not ride.

 

Also, due to the squared off sterns on these ships, following seas will "slam" more than ride up and over the sea. Also, in following seas, the stern has a whole lot of reserve buoyancy in that squared off stern, so it will rise more than the bow does, and this brings the rapidly turning propellers closer to the surface, and causes more vibration. When seas are from ahead, not only the finer entry of the bow, but the bulbous bow tends to keep the ship from "climbing its bow wave" and keeps the stern and the propellers deeper in the water.

Thank you for the information. Would you expect that the koningsdam would feel more rough than let say the NA, eurodam or any of the vista class ships?

[I_r_a]

>This is the infamous "azipod shimmy",

 

Well done, Cheng.

 

Ira

[chengkp75]

Thank you for the information. Would you expect that the koningsdam would feel more rough than let say the NA, eurodam or any of the vista class ships?

 

Well, shipbuilding being more art than science, even between the Eurodam and the NA, you will find that various parts of the ship vibrate differently, if you could put them side by side in the exact same weather. It has to do with the natural frequency of the "sound box" that is the ship's hull, and lots of that natural frequency can be varied by how the welder felt that day as he was welding a section of the hull. Different stresses put into the steel by different welding techniques and skills, will affect the frequency of a portion of the hull. If the wind and waves hit the ship in the right harmonic of that natural frequency, there will be greater vibration. I work on a class of tankers, where our company has 12 "identical" ships, and each one vibrates differently, and in different areas.

 

All three ships have azipods, and all three have similar sterns (I haven't been close enough to know how similar), so it really wouldn't stand out that one ship would handle following seas worse than the others.

[Florida_gal_50]

Well, shipbuilding being more art than science, even between the Eurodam and the NA, you will find that various parts of the ship vibrate differently, if you could put them side by side in the exact same weather. It has to do with the natural frequency of the "sound box" that is the ship's hull, and lots of that natural frequency can be varied by how the welder felt that day as he was welding a section of the hull. Different stresses put into the steel by different welding techniques and skills, will affect the frequency of a portion of the hull. If the wind and waves hit the ship in the right harmonic of that natural frequency, there will be greater vibration. I work on a class of tankers, where our company has 12 "identical" ships, and each one vibrates differently, and in different areas.

 

All three ships have azipods, and all three have similar sterns (I haven't been close enough to know how similar), so it really wouldn't stand out that one ship would handle following seas worse than the others.

Thank you for being such a great resourse to this board. I appreciate you taking time to answer my question.

[cb at sea]

I'm with you about the vibration. I find it disconcerting....and it took me forever to fall asleep. Something more midships helps...you don't feel it there.

[3rdGenCunarder]

This is the infamous "azipod shimmy", which is caused by the azipod propellers wake sweeping back and forth while steering to maintain heading. Much pronounced when a following sea. Cruise ship sterns are not designed to handle following seas very well, due to the wide, flat area required above the pods, and the sharp break to the vertical. All designed to maximize azipod efficiency, but not ride.

 

Also, due to the squared off sterns on these ships, following seas will "slam" more than ride up and over the sea. Also, in following seas, the stern has a whole lot of reserve buoyancy in that squared off stern, so it will rise more than the bow does, and this brings the rapidly turning propellers closer to the surface, and causes more vibration. When seas are from ahead, not only the finer entry of the bow, but the bulbous bow tends to keep the ship from "climbing its bow wave" and keeps the stern and the propellers deeper in the water.

 

Thanks for the explanation. I noticed the shimmy more in the dining room (lower) than our cabin (higher). It wasn't bothersome, more weird. I don't remember ever feeling that before.

 

I don't remember the exact direction of the waves the afternoon I watched to see if I could figure out the source of the banging. I think they were at an angle halfway between behind and to the side.

 

The interactive TV has less navigation info than the older system on other ships. I missed the diagram with the huge arrow to show wind direction. That explains a lot about what you're feeling onboard.

[frankc98376]

Former Nieuw Amsterdam was famous for vibration. You had to hold onto a drink to keep it from vibrating off of the table.

 

As I recall someone said that the ship harmonized with the drive shafts. I don't know if they were ever able to correct it.

 

We called her the magic fingers ship after the units in motels that vibrated the beds.

[3rdGenCunarder]

Former Nieuw Amsterdam was famous for vibration. You had to hold onto a drink to keep it from vibrating off of the table.

 

As I recall someone said that the ship harmonized with the drive shafts. I don't know if they were ever able to correct it.

 

We called her the magic fingers ship after the units in motels that vibrated the beds.

 

What we experienced on K'dam was random bangs, like going over speed bumps, not the kind of regular vibration you're talking about. I'm used to that kind of vibration. (no, not from hotel beds!) My beloved QE2 vibrated a lot when she was accelerating out of port. She didn't have pods, so all the machinery was inside the hull. All the souvenir glasses and mugs in the shop way at the back would rattle and make jingling noises when she was sailing at a high speed. And the harmonics that chengkp75 described would make one aft bank of her elevators vibrate.

[chengkp75]

Former Nieuw Amsterdam was famous for vibration. You had to hold onto a drink to keep it from vibrating off of the table.

 

As I recall someone said that the ship harmonized with the drive shafts. I don't know if they were ever able to correct it.

 

We called her the magic fingers ship after the units in motels that vibrated the beds.

 

Yes, multi-propeller ships tend to have problems with vibrations. If the two propellers are turning at the same speed (which they normally do, because of the command/feedback nature of their controls) and the propeller blades are in synch (both have a blade pass the "12 o'clock" position at the same time, you get two cavitation waves coming from two slightly different positions (the distance between the propellers) hitting the hull, and this causes vibration. Many systems will incorporate a "blade position" sensor so that they can shift the "phase" of one propeller so that even when turning at the same speed, the blades are not passing the hull (12 o'clock) at the same time, reducing the vibration.

[chengkp75]

What we experienced on K'dam was random bangs, like going over speed bumps, not the kind of regular vibration you're talking about. I'm used to that kind of vibration. (no, not from hotel beds!) My beloved QE2 vibrated a lot when she was accelerating out of port. She didn't have pods, so all the machinery was inside the hull. All the souvenir glasses and mugs in the shop way at the back would rattle and make jingling noises when she was sailing at a high speed. And the harmonics that chengkp75 described would make one aft bank of her elevators vibrate.

 

A lot of this "banging" (known as "slamming") is caused because the ship's speed is out of synch with the waves' speed, so the ship doesn't ride up and over smoothly, but every 3rd or 4th wave catches the ship heading down when it should be going up to ride the wave, and the wave slams into the ship. Many times a small adjustment to speed can reduce this greatly, and following or "quartering" (45* to stern) seas will magnify the effect.

[MogeyMan]

A lot of this "banging" (known as "slamming") is caused because the ship's speed is out of synch with the waves' speed, so the ship doesn't ride up and over smoothly, but every 3rd or 4th wave catches the ship heading down when it should be going up to ride the wave, and the wave slams into the ship. Many times a small adjustment to speed can reduce this greatly, and following or "quartering" (45* to stern) seas will magnify the effect.

 

And yes, during the day when I suppose they weren't trying to make time, it wasn't there, and I could nap, thank og.

[3rdGenCunarder]

A lot of this "banging" (known as "slamming") is caused because the ship's speed is out of synch with the waves' speed, so the ship doesn't ride up and over smoothly, but every 3rd or 4th wave catches the ship heading down when it should be going up to ride the wave, and the wave slams into the ship. Many times a small adjustment to speed can reduce this greatly, and following or "quartering" (45* to stern) seas will magnify the effect.

 

Yes! I did notice that several waves didn't cause a bang and then suddenly one would. So it's the intersection of two sets of oscillations at different frequencies--the frequency of the waves and the frequency of the ship's pitching. Cool! I do love physics!!!

(we need a nerd smilie)

[catl331]

All three ships have azipods, and all three have similar sterns (I haven't been close enough to know how similar), so it really wouldn't stand out that one ship would handle following seas worse than the others.

We had this problem for a couple days in a stern cabin on the Noordam.