Sea Sick on Koningsdam - Dec. 23-30 Sailing

[Turtles06]

Yes - just ask at the front desk for motion pills. They are free! My DW takes them the first couple of days on our cruises and also if we are doing a small boat tour. They don't make you tired.

 

Respectfully, this is not a statement that is true for all people regarding their reaction to meds for motion sickness. Even meclizine (brand name Bonine), promoted as a "non-drowsy" med, make some folks sleepy or woozy. People who haven't taken these meds before might want to try one on land to see how they react before taking them for the very first time on a ship.

[Tom O.]

And if you prefer to get it ahead of time... bestter to start 1-3 days ahead on it... meclizine is what you want to look for. Not drowsy like dramamine is (even when it says it isn't)

 

Dramamine II, usually marked "Less Drowsy Formula" is actually Meclizine. Other brands of Meclizine are Bonine, Bonamine, Antivert, Postafen, Sea Legs and many generics.

[igraf]

Thank you for your comments as I find this topic to be interesting.

 

In general, I have deep reservations about the addition of structure to the highest deck (or even adding a top deck) to an already carefully designed ship. I would guess that the new Vista-class cabins and cabana deck will generate additional revenue at the expense of the ship's dynamics.

 

igraf

 

 

 

 

 

Well, yes and no. While raising the center of gravity of an object on land, without changing the base width, does result in a less stable object, in water the situation changes.

 

What determines a ship's stability is its "metacentric height", or the distance between the center of gravity and the "metacenter". The metacenter is the point around which the center of buoyancy moves as the ship rolls. Because a ship in cross section looks like a rectangle in the water, as it rolls, the shape of the portion under water that provides buoyancy changes, and therefore the center of bouyancy moves side to side. This change in the center of buoyancy is an arc, and the center of this arc is the metacenter. So, the buoyancy force acts up through the metacenter (along a radial of the buoyancy arc), while the center of gravity acts down through the center of gravity. The distance between these two force vectors is the "righting moment", or the amount of force the ship generates to right itself from an outside induced rolling force. A low center of gravity compared to the metacenter (think of a loaded tanker with only a couple of feet above the water), has a low metacentric height, and therefore rolls quite easily, but also does not generate much righting moment, so it rolls slowly and "hangs" at the end of each roll, as we say "thinking about whether it will come back". A ship with a high center of gravity with relation to the metacenter, like a cruise ship, will generate very high righting moment at very low roll angles, so these ships tend be more resistant to rolling, but roll very quickly. This quick rolling is very uncomfortable (called snap rolling), so a moderately high metacentric height, but not too high, is desirable for a cruise ship.

 

To make a long story short, raising the center of gravity changes the roll period (how fast the ship rolls), but not necessarily the "roll stability", as the high metacentric height is difficult to start to roll initially.

 

Now, if you are talking about surface area, and wind induced heel, that is a totally different thing, and is related to size.

Edited December 27, 2016 by igraf

[sailandcruise]

Stabilizer effectiveness has a lot to do with the ship's speed, both the speed over the ground and the speed through the water. The stabilizer is just like an airplane wing, so the faster it moves through the water, the more "lift" it generates to counteract the rolling. With today's reduced ship speeds between many ports, the stabilizers aren't that effective.

 

There are also certain times when the wave period and direction, in relation to ship speed and course, and the hull design, result in a "harmonic" resonance to the ship's rolling, and the stabilizers, no matter how "new" can only do so much. A ship is much larger than an airplane, and a stabilizer is much smaller than an airplane wing.

 

chengkp75,

 

thanks for all your detailed and accurate explanations. i always find them informative and scientific.

 

however, i don't completely understand your statement above, at least the part about stabilizer effectiveness depending on both the speed over the ground and the speed through the water. why would ground speed matter? my understanding is that stabilizers generate lift from the fluid flow around them. how would they interact with the ground? (or is this an indirect interaction in so far as the fluid dynamics, especially in shallow water, are effected by the currents, which in turn affect the stabilizers?)

[chengkp75]

chengkp75,

 

thanks for all your detailed and accurate explanations. i always find them informative and scientific.

 

however, i don't completely understand your statement above, at least the part about stabilizer effectiveness depending on both the speed over the ground and the speed through the water. why would ground speed matter? my understanding is that stabilizers generate lift from the fluid flow around them. how would they interact with the ground? (or is this an indirect interaction in so far as the fluid dynamics, especially in shallow water, are effected by the currents, which in turn affect the stabilizers?)

 

Well, its simply that the speed over ground and speed through the water are related. Speed over ground is sort of the major factor, since with a static ocean, this also equals speed through the water. Then, depending on the direction of the current or seas, the motion of the water over the ground will add or subtract from the speed over ground. So, while a 1 knot current from ahead or astern will affect the speed through the water, whether the ship is doing 18 knots or 5 knots, will have a greater impact on the effectiveness of the stabilizer. But, yes, it all comes down to the speed of the fluid the wing is passing through.

[AV8rix]

Well, its simply that the speed over ground and speed through the water are related. Speed over ground is sort of the major factor, since with a static ocean, this also equals speed through the water. Then, depending on the direction of the current or seas, the motion of the water over the ground will add or subtract from the speed over ground. So, while a 1 knot current from ahead or astern will affect the speed through the water, whether the ship is doing 18 knots or 5 knots, will have a greater impact on the effectiveness of the stabilizer. But, yes, it all comes down to the speed of the fluid the wing is passing through.

 

Great explanation of fluid dynamics!! Back when I was young and flying in Texas ….where we ALWAYS have strong winds….. we could fly our antique planes (low stall speeds) literally backwards just for fun. No, we didn’t crash, the airfoil was quite happily maintaining lift…wind over the wing was greater than the stall speed…but our ground speed was actually negative and we were moving backwards relative to a reference point on the ground.

 

Always a treat to read ANY of your posts, chengkp75.

[oatbagg1]

We were on the Koningsdam for our 5th cruise Dec 4-14 and were actually disappointed because the stability was TOO good. We like it rocky for fun. Must've just been a rough run for you.

 

we were on 12/4-12/14 Southern Caribbean on deck 7 and there were times it felt like we were hitting objects in the water. All the way forward is our favorite place to be. but it felt very jolty. The exercise room was always rocky.

[lorimay]

We were on the same cruise as the OP and it was rocking some days. I have had terrible problems with sea sickness in the past and took meclazine the first two days but it makes me way too drowsy to enjoy anything. I stopped taking it and never felt ill, but every one is different.

We went to the "Ask the Captain" and he said they were using the stabilizers but that the seas had been very rough due to high winds for the last six weeks. Apparently this weather is not expected until January and he seemed very upset about it. He denied any difference from the Koningsdam to other ships in regards to smoothness of sailing.

 

 

Sent from my iPhone using Forums

[Lady Arwen]

Well, yes and no. While raising the center of gravity of an object on land, without changing the base width, does result in a less stable object, in water the situation changes.

 

What determines a ship's stability is its "metacentric height", or the distance between the center of gravity and the "metacenter". The metacenter is the point around which the center of buoyancy moves as the ship rolls. Because a ship in cross section looks like a rectangle in the water, as it rolls, the shape of the portion under water that provides buoyancy changes, and therefore the center of bouyancy moves side to side. This change in the center of buoyancy is an arc, and the center of this arc is the metacenter. So, the buoyancy force acts up through the metacenter (along a radial of the buoyancy arc), while the center of gravity acts down through the center of gravity. The distance between these two force vectors is the "righting moment", or the amount of force the ship generates to right itself from an outside induced rolling force. A low center of gravity compared to the metacenter (think of a loaded tanker with only a couple of feet above the water), has a low metacentric height, and therefore rolls quite easily, but also does not generate much righting moment, so it rolls slowly and "hangs" at the end of each roll, as we say "thinking about whether it will come back". A ship with a high center of gravity with relation to the metacenter, like a cruise ship, will generate very high righting moment at very low roll angles, so these ships tend be more resistant to rolling, but roll very quickly. This quick rolling is very uncomfortable (called snap rolling), so a moderately high metacentric height, but not too high, is desirable for a cruise ship.

 

To make a long story short, raising the center of gravity changes the roll period (how fast the ship rolls), but not necessarily the "roll stability", as the high metacentric height is difficult to start to roll initially.

 

Now, if you are talking about surface area, and wind induced heel, that is a totally different thing, and is related to size.

 

That's just what I would say. Honest.

[St. Louis Sal]

We were on the same cruise as the OP and it was definitely a rock and roll cruise. When the captain uses the term "gale winds" I know we are in for some bouncing. The bags were put out at least twice and walking down the halls was an adventure some days. We took two cruises in November and also experienced a lot of wind and high seas which caused a couple of our ports to be cancelled. I was glad we had such a perfect day at HMC on Thursday!

 

Just a side note: K'dam seems to have eliminated the yum-yum man. It was strictly self-serve for mints and ginger each night we were in the dining room on both levels. Very disappointing:(

 

St. Louis Sal