Do not jump overboard unless you have no alternative. That is what this explanation of buoyancy -- the power to keep afloat -- is intended to impress upon you.
For a vessel to stay afloat, the upward pressure of the water must be equal to the downward pressure or weight of the vessel. However, because a ship is torpedoed, it does not necessarily follow that the balance of opposing pressures is going to be so altered that the ship must sink. Four men on the torpedoed tanker Malay were unable to consider this, and they lost their lives, though the Malay itself made port safely.
A vessel is composed of several units. Each hold, as well as the fireroom and engine room, is an independent buoyant section.
Picture in your mind a small freight vessel. Visualize each hold as being detached from the other. Each, as you picture it, is now floating independently. The engine room and fireroom, you will see, are floating deep. The #1 and #4 holds are not quite so deep. The #3 hold has less draft, while the #2 hold has the least depth of all.
The sums of all these individual buoyancies make the total buoyancy of the vessel.
Though the tanker E.H. Blum was broken in two by a torpedo, the forward half still had sufficient buoyancy to permit it to be towed to port.
Captain Theodore Bockhoff understood the buoyancy set-up of his stricken freighter after it was hit by a torpedo. That is why he ordered Seaman James Sherlock, who was running for the starboard boat, to wait. A few moments later, as the starboard lifeboat reached the water with six men in it, a second torpedo blew it to bits.
When the torpedoed tanker Gulftrade broke in two, nine men were on the stern. Seaman Leonard Smith wanted to jump overboard. Guy F. Chadwick, the chief engineer, reminded Smith that the water was cold. "Let's stick with the ship," Chadwick advised, "as long as she'll stick with us." At the very least, the chief's understanding of buoyancy spared a man from exposure and frostbite.
Suppose the vessel is loaded with lumber, and a hold is stove in. Since the specific gravity of wood runs from one-fifth to a slight fraction beyond that of water, the only loss is in the reserve buoyancy, as the lumber's buoyant qualities will substitute for the loss of actual
buoyancy. The space which the sea can occupy is only the area not already taken up the lumber.
Often, when only one or two buoyant sections are immediately damaged, the vessel eventually sinks. The China Arrow, torpedoed twice, took an hour sink. This was probably due to the fact that while the destruction of tanks in the vicinity of the blasts was not enough to sink the China Arrow, the detonations sheared plates and loosened rivets in the tanks beyond. Buoyancy is often lost on tankers when heat from the oil blaze buckles the plates. Our point is that it takes time for this buoyancy to be lost.
This is borne out by the Latvian freighter Ciltvaira. After abandoning ship the men were able to go back, run up SOS flags, and salvage valuables. Captain T.R. Hennevig returned to his crippled freighter eight hours after it had been torpedoed and shelled. A sugar transport vessel, torpedoed off Nuevitas, Cuba, remained afloat and was beached, though 22 crewmen died when lifeboats were sunk by gunfire.
A hold stowed with general cargo presents a serious condition. All the buoyancy of that hold would be lost. Grain cargo likewise adds a threat to a stricken vessel. Expanding from absorbed water, the grain will exert pressure on the watertight bulkhead and loosen rivets.
In short, experience and the laws of physics indicate that men usually have more time to abandon ship than they allow themselves. However, statistics are often contradicted by an individual situation, so don't let them lull into carelessness. Ships have sunk in five minutes or less.
For your protection discuss with the mates and engineers the buoyancy problems of your ship. And before you jump, remember that Bryan Lloyd, a seaman, had time to swim back to his ship from a swamped lifeboat, rest five minutes, and release a liferaft. Captain Knut O. Bringedal was able to return to his torpedoed vessel three times. And the tanker Esso Bolivar, with water ballast, was towed into port with a 40-foot hold blasted in her side.
This old-type tanker made port under her own power.
(Official U.S. Navy photograph--International News Photos)
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