A question from a landlubber

Roamy here. I know it has to be different for every ship, but I was wondering just how much list could a ship handle before it capsizes or breaks up? I would think that the old sailing ships had to have a lot of ballast, and a list would be expected with full sail.

On this day in 1941, the aircraft carrier HMS Ark Royal was part of a convoy to supply Malta when she was torpedoed by a German U-boat off the coast of Gibraltar. The torpedo tore a 130 × 30 ft hole on the starboard side below the bridge island, between the fuel bunkers and bomb store. After the ship started to list, Captain Loben Maund gave the order to abandon ship.

The Ark Royal was part of Force H that had sunk the Bismarck the previous May; now other ships of Force H, led by Admiral James Somerville, came to her rescue. Unfortunately, damage control was too little, too late, and hatches and covers had been left open during the crew evacuation. The Ark Royal listed 45°, capsized, broke in two, then sank on November 14. All but one of the 1,487 officers and crew survived the U-boat attack – Able Seaman Mitchell was killed in the initial explosion. Captain Maund was later court-marshaled for negligence.

The Ark Royal did have several design flaws that were corrected for the Illustrious– and Implacable-class carriers. There were no backup generators, so when the boilers went out, so did the bilge pumps. There was a boiler room flat that ran the width of the Ark Royal, so the bulkhead and boiler intake designs were changed to prevent that kind of flooding.

I think the aircraft onboard are Fairey Swordfish; please correct me if I’m wrong.

8 thoughts on “A question from a landlubber”

  1. Foamy – the amount of stability in a ship is directly related to how much water the displaces. Meaning that the design of the ship has to account for length, width and height of the superstructure. The are two balance points ona ship – center of gravity both vertical and horizontal and length over all. The equations aren’t complicated but they determine how much draft the hull requires to stay upright and stable. Draft meaning how much water is below the waterline. On a sailing ship like the frigate USS Constitution COG & LOA balance is done by figuring the amount if weight needed to counteract the forces mentioned – that weight is called ballast. Hope that helped. I could go into more detail but I’m using my Droid and I hate the virtual keyboard. 🙂

  2. I think you’re right about the Swordfish. I read a book last year written after the war by the pilot who killed the Bismark (although, he didn’t know it at the time). He was flying a Swordfish.

  3. The Swordfish did not kill the Bismarck. A torpedo from a Swordfish jammed one of the rudders, slowing it down. The ship was eventually brought to bay, and several Battlewagons, Rodney and King George V among them, hammered the ship to death.

    Roamy, the sailboats in the pick are not listing. A list is an abnormal “leaning” of the ship to one side of center line caused by a load imbalance. The sail boats are “heeling” in response to the load of the wind on the sails, and is a normal phenomenon.

    The boat will heel until there is a balance between the force on the sails, and the righting moment of the boat. You should remember that from your course in Statics and 1st semester Physics. The moment arm between the force that produces the righting moment, and the “center of effort” (the point on the sails where you could resolve the entire force produced by the wind) will determine the amount of heel. Racing boats routinely place most of the crew on the windward side to reduce the heel and increase the efficiency of the boat after the sails are set for the tack they are on for that part of the race.

    The righting moment is determined by a combination of factors. Boat weight and hull shape are the two most obvious factors. Since wetted area of the hull also determines hydrodynamic drag, efforts are made to reduce the draft of the boat to a minimum. That means you will have to effectively increase the draft of the boat through other means. The most popular are very narrow “fin keels” with weights attached to the bottom of the fin to increase the righting moment. These weights lower the center of gravity below the center of buoyancy to produce the righting moment. The boat will not be stable if the center of buoyancy an the center of gravity coincide. If the center of buoyancy is lower than the center of gravity, the boat will have a tendency to “turn turtle” or capsize. Certain waves at sea can produce that effect if the righting moment is overwhelmed. The worst form of turning turtle is “pitch poling” where a wave actually tosses the boat end for end. Pitch poling can do serious damage to the boat structure, while turning turtle often just damages the boat rigging.

    The Coast Guard has boats with extreme righting moments, I saw a film demo of one rescue boat, the type they used to place at their “surf stations” that they completely capsized, but the boat would right itself. The crew would not enjoy the experience, however. I would have wanted a motorcycle helmet to crew that boat!

    What happened to the Ark Royal in the incident you mention came as a result of the damage to the main hull of the ship. Such ships are not designed to operate with a significant amount of water inside teh hull, and the extra load caused a cascading failure that broke the ship apart. The loss of the Ark Royal was actually caused by crew failure. Later in the war, we were saving ships with far more grievous damage. The Franklin is a good example of a capital ship of the same basic type as the Ark Royal that was saved after such damage. I think the Brits to heart the lessons we learned early in the war about damage control and fire fighting and sent a bunch of people to some our DC & FF schools and took the knowledge back with them. If the Ark Royal incident had occurred in 1944 instead of 1941, the ship most likely would have been saved.

    1. Well… the Ark Royal had a huge hole in the bottom. The Franklin didn’t. She DID have stability problems from free surface area issues from firefighting water sloshing around. But the basic integrity of the hull was still there.If she’d sustained the same type of underwater damage as Ark Royal, I’m not certain she’d have been saved. The Essex class were incredibly tough ships, and DC/FF had been GREATLY improved, but comparing torpedo damage to fire/kamikaze damage is a bit apples and oranges.

  4. Stability is something that is a part of my working life. There are many factors that can affect it, including icing, wind, bunkers, trim and free surface effect by seawater not clearing freeing ports in a timely manner. The boats I operate and the barges I tow have stability instructions including how many tanks slack tanks may be maintained at any time. Also, the waters you operate in dictate how the vessel may be loaded (Tropical, Summer, Winter, Winter North Atlantic) Which in turn bears on stability. Nowadays, computer programs make the task of loading cargo on a barge and maintaining the stability instructions easier than pulling out the engineering calculator and a scratch pad. Stability is something a mariner ignores to his own peril. Xbrad may remember the “A” boats out of Anacortes, two fishing boats lost with all hands around the time we graduated high school. They had been modified and refitted to the point that they exceeded their ability to right themselves when fully loaded. They both went down within a couple miles and a few hours of each other. In flat calm weather.
    The worst roll I ever took on a boat was 40 degrees. It is not an event I ever want to reapeat.

    1. I’d forgotten the “A boats” story. Perhaps I’d already left town?

      But I do know we took the Whidby to 55 degrees once.

      Once.

      And by “freeing ports” do you mean “scuppers?”

    1. Yep, scuppers.
      My cook here on the boat grew up in Anacortes. His cousin was on the Altair. There is an excellent book on the loss of the “A” boats and the tangled investigation into why called “Lost at Sea” by Patrick Dillon.
      Also should mention the other little thing regarding stablity when operating a towing vessel. Being “tripped” or “girded” by your tow. Here’s a good example what happens when your center of gravity is overcome: http://www.youtube.com/watch?v=QEfUblSDzww
      You may recognize the place, xbrad. Skookumchuck Narrows is what we knew as Sechelt Rapids.

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