Ship Size & Ride?

[mtwoodson]

I am interested to hear from small ship guests that have experienced rough seas when on Renaissance R-class ships like Pacific Princess, Tahiti Princess, Insignia, Nautica or Regatta and also on large ships. How did these 30,000 ton ships ride and how do you think they did compared to the large ships closer to 100,000+ tons?

 

For the Naval Architects online does size really matter, or do they all move around relatively the same amount in 30 foot waves/swells? Design would also seem to be a factor as many large ships do not have deep hulls so they can get into more ports without having to tender. The largest cruise ship is Freedom of the Seas and has a draft of 28 feet. Grand Princess for example is 109,000 tons and has a draft of 26 feet. Celebrity Mercury is only 77,000 tons but also has a 26 foot draft. All the Oceania ships are 30,000 tons and have a draft of 20 feet which are the highest ratios of draft to tons. Does this matter? What does?

 

I personally have been in several gales with 25 to 30 foot seas and the ships road beautifully. I've also been in 8 foot seas on another larger ship and it moved around more than the slightly smaller ship in the larger seas. I even rode through a hurricane on a 200 ft. research ship many years ago with 45 foot seas. Now I am very curious about the old myths and what the reality may be.

Thanks.

John

[kitty9]

I have been on the very small ships like Seabourn which is less than 10,000 ton and on the behemoth QM2. A lot has to do more with the stabilizers than with the size of the ship and also the type of waves. I've been in rough seas on Seabourn and didn't feel much and then again I was on a North Atlantic crossing on Seabourn and couldn't walk in the cabin because it was so rough. I was surprised by how much pitch and roll I felt on the QM2. The smoothest ship I've been on, and I've been on most of them, is Crystal Symphony. We did a crossing from FLL to London and had 45ft seas and barely felt it move. We only knew it was rough because the green water was washing over the windows on deck 6. The old Ren ships, for whatever reason, don't seem to handle rough seas as well as ships of a similar size, namely Silversea and Regent.

[Cuizer2]

I am interested to hear from small ship guests that have experienced rough seas when on Renaissance R-class ships like Pacific Princess, Tahiti Princess, Insignia, Nautica or Regatta and also on large ships. How did these 30,000 ton ships ride and how do you think they did compared to the large ships closer to 100,000+ tons?

 

For the Naval Architects online does size really matter, or do they all move around relatively the same amount in 30 foot waves/swells? Design would also seem to be a factor as many large ships do not have deep hulls so they can get into more ports without having to tender. The largest cruise ship is Freedom of the Seas and has a draft of 28 feet. Grand Princess for example is 109,000 tons and has a draft of 26 feet. Celebrity Mercury is only 77,000 tons but also has a 26 foot draft. All the Oceania ships are 30,000 tons and have a draft of 20 feet which are the highest ratios of draft to tons. Does this matter? What does?

 

I personally have been in several gales with 25 to 30 foot seas and the ships road beautifully. I've also been in 8 foot seas on another larger ship and it moved around more than the slightly smaller ship in the larger seas. I even rode through a hurricane on a 200 ft. research ship many years ago with 45 foot seas. Now I am very curious about the old myths and what the reality may be.

Thanks.

John

 

The QM2 has a deeper draft than the Freedom of the Seas. The QM2 is an ocean liner while the Freedom of the Seas is a cruise ship.

[mtwoodson]

The old Ren ships, for whatever reason, don't seem to handle rough seas as well as ships of a similar size, namely Silversea and Regent.

 

I've also noticed that the Crystal ships seemed to ride very well, Silversea did not and the Regent Mariner was excellent but Navigator "wobbled". I've also been on several large ships that did very well (e.g Celebrity M-class, RCCL Vision and Radiance-class) and many that did not. I have long suspected there are not only sea condition issues but ship design issues that I don't understand. Draft may be a factor.

 

Have you sailed on the old Ren ships? These are all coming back into the US based market with new names and I have never sailed on one of these.

Thanks.

[mtwoodson]

The QM2 has a deeper draft than the Freedom of the Seas. The QM2 is an ocean liner while the Freedom of the Seas is a cruise ship.

 

I see that the QM2 has a 33 foot draft for her 150,000 tons which suggests it might ride better than Freedom, but as Darcie pointed out in her post QM2 still moves around a surprising amount. I wonder if the ratio of the draft to tons is better indicator? The QM2 which you described as an oceanliner and not a cruiseship has a surprisingly poor ratio of tons per foot of draft - about the same as the Voyager of Sea class ships which one might think would also be in your cruiseship category.

 

Darcie noted Crystal Symphony rode notably well to her. It is 51,000 tons and has a 25 foot draft. It has about 1 foot of draft for every 2000 GRT, as does the Regent Mariner and a few others. The QM2 has 4600 GRT per foot of draft - one of the worst ratios I could find except for Freedom of the Seas. The old Royal Viking Sun (now Prinsendam) which did and has done World Cruises for years has a ratio of only 1600 GRT per foot and those old Renaissance ships have only 1550 GRT per foot of draft. Does this imply they should ride better or at least very well?

 

Another factor that may be interesting is that many of the new ships have very heavy pods hanging off the bottom of the ship in the aft area. That is a lot of weight very low in the water - does this act like a heavily weighted keel like we find in fast racing America's cup ships?

[spongerob]

... A lot has to do more with the stabilizers than with the size of the ship and also the type of waves...The smoothest ship I've been on, and I've been on most of them, is Crystal Symphony. We did a crossing from FLL to London and had 45ft seas and barely felt it move. We only knew it was rough because the green water was washing over the windows on deck 6.

The smoothest ship we've sailed on was the old Royal Princess, now P&O Artemis. I highlighted the quote above because I believe that Crystal's ships are based on the design of the original Royal Princess. The key thing is not stabilizers, but hull design and sail area (I know they don't have sails, that refers to the area that can be affected by wind). The Princess Grand-class ships seem to move a little more than you'd expect when it's windy - I don't think it's unpleasant, but that's just me. Stabilizers only do so much and serve to limit and counteract roll, not prevent movement altogether. In fact, stabilizers are often retracted because they reduce the ship's top speed and cause extra fuel consumption.

 

I think it's a complete myth that bigger ships are more stable than smaller ships. All ships are going to move, and maybe a lot, if conditions get bad.

[LHT28]

We have sailed the Insignia in the Irish sea in a gale and the Regatta in the Caribbean in rough seas ...we didn't have a problem it was a bit bumpy on both but it all depends on how far apart the waves are and if they are off the beam etc....

A lot of people were sick that day.

In the Caribbean it was more noticable and we had some good rollers....one night we hit a rogue wave that went over the stack.

We were on deck 4 & we thought we had hit a container but found out the next day it was a wave.

If you are sensitive to motion you will feel it on most ships....go prepared with seasick medicine.

[hyperion]

The other professionals haven't weighed in yet so I'll try to answer.

 

As you have noticed as ship with a deeper draft isn't necessarily going to roll less that one with a shallower draft. It all really boils down to ship stability.

 

The lower the center of gravity the more the ship will want to stay vertical. The higher your center of buoyancy, the greater the righting arm to to roll the ship back to the vertical when she lists. The mathematical size of this righting righting arm will make the difference on how the ship responds to a roll. Too large a righting arm and the ship will be very "stiff", listing only a little to either side but very quickly returning to the vertical. If the righting arm is smaller, the ship experiences a more "tender", slower roll, but typically will list to a greater angle from the vertical.

 

This is why most heavy machinery like engine spaces are located at the bottom of ships and why one cruise ships one of the items on the emergency checklists is to drain the. the ships pools. Actually, when the Grand Princess first entered service there were a lot of rumours going around that while still at the drydock she had to have her Disco (the big handle shaped thing on the stern) redesigned so that she could pass her

stability test. (Quite possible considering the final 2 ships in that class have a totally different arrangement.)

 

As previously mentioned by others the use of stabilizers on cruise ships help tremendously with this effect.

 

If you would like to learn more about transverse stability wiki "Metacentric Height."

 

 

Cheers,

 

John

[mtwoodson]

John,

Great reply. I was hoping to hear from some professionals. I can't wait to try that "wiki" reference.

 

I sounds like conventional wisdom that the bigger the ship the better the ride is probably a myth.

 

It also sounds like the ships with those very heavy pods hanging underneath ride better for a reason. You would think the cruise lines would want to advertise this and market this.

 

This does raise many questions like:

1. How does one figure out which ships will ride well especially when planning cruises that going into well know rough areas?

2. Can a well designed small ship ride as smoothly as a big ship?

Thanks again.

[hyperion]

I sounds like conventional wisdom that the bigger the ship the better the ride is probably a myth.- I guess the best way to look at that concept is as more of a thumb rule. (It all depends on how you define "big" ? Tonnage, Length, Beam, Height...)

If you mean length...the same factors I mentioned in my previous post also work longitudinally (bow to stern) through the ship. On that basis a longer ship is going to pitch along a longer axis than a shorter ship giving a feeling of less movement.

 

This does raise many questions like:

1. How does one figure out which ships will ride well especially when planning cruises that going into well know rough areas?- As a passenger unfortunately the only real way is probably by word of mouth. Of course as you are aware, not everyone has the same notion of what constitutes a lot of motion.

2. Can a well designed small ship ride as smoothly as a big ship? Good question! I'm just a lowly navigation officer so that goes beyond my knowledge base. I would say that through the use of stabilizer fins, and bilge keels can go a long way to reduce rolling but the ship will still pitch.

 

Does that help any? There's a couple of Captains kicking around the board the might be able to explain this part better than I can.

[Cuizer2]

How does one figure out which ships will ride well especially when planning cruises that going into well know rough areas?- As a passenger unfortunately the only real way is probably by word of mouth. Of course as you are aware, not everyone has the same notion of what constitutes a lot of motion.

 

This reminds me of a story my Dad told me. He was on a Caribbean cruise and asked the captain if it was always this calm. Before the captain could answer another passenger asked if it was always this rough.

 

How is it being determined which ships move more than others? Are these side by side comparisons measured by reliable gauges or are these lay people's opinions.

 

It is likely very hard for a lay person to tell the difference between an four foot wave and a five foot wave while standing 50 to 100 feet above the water line. Yet the five foot wave is 25% bigger than the four foot wave and thus likely to cause more ship "movement."

 

Are the comparisons being made while the ships are moving at the same speed and hitting the waves at the same angle? A ship at getting hit square in the bow by a five foot wave will probably move less than a ship getting hit square on the side by a four foot wave.

 

 

Are the people making the comparisons standing in the same place? Someone standing on the bow will feel more movement than someone standing mid ship.

 

What kind of movement are we talking about here? Pitch or roll? Are the wind conditions the same for all the ships being evaluated? What are the currents like while someone is evaluating whether one ship moves more than the other?

 

Draft effects "movement." So does size, weight, center of gravity, wind, current, sea condition, wind, ship speed ...

 

Weight is a factor. No matter how well you design it, a speed boat is going to move more than a cruise ship, simply because it is easier to move a 5000 pound speed boat than it is to move a 50,000 ton (not gross ton) ship.

 

Stabilizers design also plays a factor.

 

Does the QM2 move around more simply because it spends more time in rough seas (aka the north Atlantic)?

 

You can say that all things being equal, a bigger ship will ride better than a smaller ship. However, not all things are equal. If the waves are coming at the bow, a longer ship will ride better. If the waves are hitting the side of the ship, then a wider ship with a lower center of gravity will ride better.

 

Remember the twin hull Diamond? That was supposed to be a good ship in rough seas. However, that ship had other problems (slow speed, deep draft ...).

 

You want the smoothest riding ship for rough seas? Join the Navy and volunteer for submarine duty. Those ships ride real well in rough seas. Of course then also have incredibly deep drafts. In fact, the drafts are so deep, that usually the waves continue right over the ship without causing any movement at all.

[mtwoodson]

...

1. How does one figure out which ships will ride well especially when planning cruises that going into well know rough areas?- As a passenger unfortunately the only real way is probably by word of mouth. Of course as you are aware, not everyone has the same notion of what constitutes a lot of motion.

2. Can a well designed small ship ride as smoothly as a big ship? Good question! I'm just a lowly navigation officer so that goes beyond my knowledge base. I would say that through the use of stabilizer fins, and bilge keels can go a long way to reduce rolling but the ship will still pitch.

 

Does that help any? There's a couple of Captains kicking around the board the might be able to explain this part better than I can.

 

Yes your posts have definitely helped, thank you. People often have many choices of ships to the same destination. For many itineraries like Alaska and most summer-time Europe destinations bad weather isn't very likely so other factors can be used as the basis of a decision. However, for someone considering a cruise where the seas are known for their potential for being rough the stability of the different choices can be an important factor for some. If there is a big difference between how a luxurious 30,000 ton ship would ride (stability) compared to a 100,000 ton ship, it could be an important factor in the decision. If there is no clearcut advantage for either size ship this factor can be ignored in the decision and that is very helpful to know.

 

If the answer is it is impossible to tell, or we just don't know, one either must ignore this factor or hope the the subjective feedback provides some insight. Subjective feedback while very interesting is very difficult to use to answer questions like which is better A or B because the person giving the feedback can never be on both A & B at the same time in the same conditions to compare. We know that two people on the same ship and the same time can report wildly different views on stability. If there are a large percentage of the samples of A or B that report great ride or poor ride, we may be able to get some idea.