[Again, sorry, I’m politicked out for today. -BZ]
For the engineers and nautical experts amongst you:
Look at the above photograph I took back in 2004 of Holland America’s cruise ship Zaandam entering Glacier Bay, Alaska.
When some of the greatest dangers a ship — any ship — can face are heavy seas with rogue waves and “nautical” weather, why is it that massive ships — in this case, civilian ships — are designed to be, essentially, “top heavy”? Still, these days, most ships in dangerous waters (commercial, civilian, military) are struck by capsizing, which is an issue of rolling.
Please note the width of this large ship as contrasted to its height. For notation’s sake, the draft of the Zaandam is 26-feet, not a huge amount of footage below the water, considering the overall 780-foot length and 60,906 ton weight of the ship.
Does it not appear that it is “over-tall” and “too narrow” for blue waters and heavy seas?
On this planet, a given object can react in only three dimensional ways: roll, pitch and yaw. These are respective rotational axes sourced from a defined equilibrium state in air and water.
My question is this: With a tall ship, narrow width, does that not make the Zaandam, for example, subject to greater amounts of roll in nautical weather than a lower, wider ship?
When it would seem to me that the equation in shipbuilding is lower height coupled with greater width, where is it that I “go wrong”? Is this not the issue with the creation of, for example, the catamaran quotient? And further, does this not become, all things considered, a matter of safety?
WWII destroyers of the US were, to make another example, tall, narrow and light. They also fared the worst in heavy weather. Check out the new non-fiction book “Down To The Sea” by Bruce Henderson in which Admiral Halsey ordered ships into a typhoon, which resulted in the smallest ships — destroyers — taking massive casualties. Three ships sunk, 28 ships damaged, 146 aircraft damaged, with 756 human casualties. Further, the three ships sunk had recent modifications which included additional war guns and armor to their superstructures. Which, in turn, raised their calculated centers of gravity. Plus poor ship-handling.
One additional book to consider: “The Wave” by Susan Casey, which indicates that heavy weather, coupled with a huge increase in so-called “rogue waves” results in a Lloyd’s of London estimation that most ships frequenting disaster are bulk carriers, with hatch problems, metal fatigue and poor maintenance. Yet, the trend is to continue building more massive ships.
That said, the IMO reported, from 1990 to 1997, a total of 99 bulk carrier ships lost.
In 1995, Sir Ronald Warwick, captain of the Cunard liner Queen Elizabeth II (a 1,000-foot cruise ship!) encountered a series of 95-foot waves which smashed windows and part of its foredeck. He later went on to captain the virgin Queen Mary II because of his skills.
Lloyd’s of London currently estimates that 100 + ships sink per year due to heavy and/or unusual/loading conditions, but these statistics are highly guarded and mine are subject to confirmation. Which means, of course, they won’t be confirmed because the issue is too highly volatile. Some think that two large vessels sink weekly. I cannot confirm this.
Two large ships sink every week on average,” according to Wolfgang Rosenthal, of the GKSS Research Center in Geesthacht, Germany. This equals out to about 100 ships per year, excluding small craft or docked ships sunk by hurricanes or storms, which could be in the thousands in a given year. Many sinks are attributed to rogue waves, but they are often accounted to ‘bad weather’ and so it is difficult to track.
Perhaps some of my expert readers can answer my primary question.
It would, of course, apply to the bulk of boats and ships produced as well.
BZ
I am no expert so I would refrain from answering your question.
However, I will make an observation. From the looks of that ship, I would think even the slightest wave would knock that sucker over.
I’d be afraid to be on it.
While I expect that superstructure on a passenger ship is pretty light and there’s plenty of ballast capacity below that does look like a big target for high winds and big waves, don’t it? those container ships seem to be what looks like an accident looking for a place to happen to me, they stack those cans ever higher it seems, wonder how many of those account for the losses.
You are correct BZ, they ‘get away with it’ by using something like wing stabilizers (electronically adjustable) or horizontal fins below the waterline to limit rolling moments. Another option is to ballast down (e.g. take on sea water) to make the ship ride deeper in the water. The wider you make a ship, the more friction (and power loss) you encounter, plus the ride is not as smooth due to the wider beam the seas can act on. I wouldn’t take a free cruise if you gave me the Captain’s cabin and hot and cold running ‘maids’… Only about 30 people are actually capable of ‘running’ the ship…
It is a calculation of just how much ballast(lead) is in the keel of the ship.
The calcs will also tell you just how high above the c/g you can go with super-structure.
The ship designers do this without fail, but I, like you, wonder what would happen in very heavy weather out at sea. Would it roll, or recover,,,,,and stay upright on keel.
A lot also depends how the Captain steers the ship.
I would like to know it’s “safety factor” before I boarded it.
Most travel agents wold not have the slightest idea of what I just proffered!
bz . . . I’ve owned several ocean going small boats – and I think your basic theory is correct. At the same time I have a problem accepting your two boats a day comment. Despite the awful high-narrow-shallow floating hotels I’ve not heard of any going down in quite a while. Lloyds does insure a number of car-boats, passenger ferries, and other vessels that carry hundreds and sometimes thousands of people – and go to Davy’s locker every month. Usually in India, the Phillipines, Indonesia and etc. Maybe that’s what they are counting? Bump
But, Leticia, you can’t see the nature of that and other ships unless and until you view them from your own perch on a similar cruise ship.
Mark, I would concur. You know, of course, the origin of the word “ballast,” do you not, and how the word “ballast” also applies to the railroads?
And yes, containers ships these days take massive hits from our open oceans.
NFO: and THERE you go sir! Excellent! Yet, the Holland America line does NOT utilize horizontal stabilizers as you would expect — as the bulk of their ships are built by Fincantieri in Italy.
That also, NFO, is why you see so-called outriders on Long Liner fishing boats on the east coast. You remember the boat Andrea Gail in the book and film “Perfect Storm”? Those outriders on port and starboard had nothing to do with fishing. They instead trailed for stability. Check this site for overall fishing vessel stability: http://www.fao.org/docrep/011/i0625e/i0625e00.htm
It’s like what earth engineers consider to be a “surcharge” when they build fill into various bays. For example, the San Francisco Bay has many millions of feet of earth packed INTO the bay from the late 60s so that very VALUABLE properties could be built and, further, expensive motels and venues built. When you extend what is called “fill” into a water environment, you anchor and solidify the stability of the fill by removing the actual dirt surcharge and, instead, replacing the surcharge with BUILDINGS and edifices and WEIGHT. But, in the end, it is only just fill.
I learned this from my compaction engineering classes in college, of all places.
I would proffer this as something that ALL my readers can relate:
Have you not been to a beach where the tide or surf has just gone out and the sand looks dry? But just take your foot and tap it a few times over the seemingly “dry” sand. Does it not IMMEDIATELY liquify and allow your foot to sink? Such is it with fill in oceanic and water venues. Engineering once again rears its ugly practical head.
But there are still many things in engineering that I do not understand.
Grey Geezer: I proffer this from the most recent book “The Wave” by Casey. If you are also interested I would highly recommend — in terms of fishing vessels (specifically in Alaska) and their center of gravity, buoyancy, fishing gear stability, following and quartering seas, icing, hydrostatic curves, and the stability notice, to the book by Patrick Dillon: “Lost At Sea.” A very readable and, at the same time, pointed view of how building, loading and truth can come to disastrous loggerheads.
BZ
Bump: I would also submit that killing passengers is just a tad worse than losing a frigging massive load of containers that no one much cares about short of their respective insurers.
Let just ONE major cruise ship go down these days and the ENTIRE industry would stall for years.
BZ
BZ- you’re correct, I just didn’t get into the ‘small’ boats. Outriders (or sponsons)are used as a cheap alternative to the more expensive gyro or wing stabilizers.
NFO: and thanks, sir. But yeah, they are the cheaper alternative to those much more expensive options. Most people think the booms and lines somehow have something to do with fishing off the sides of the boats.
BZ
Not unless it’s by accident BZ 🙂