Its still too early to determine what caused the Korean ferry disaster, where hundreds of school kids drowned. We don’t know if it was mechanical failure, crew error, an act of God, or even enemy action. (Would anyone put it past the N Koreans to have mined those waters, or torpedoed the vessel?) Most likely, it was a combination of several of those factors.

The current speculation is that the ship violently maneuvered, perhaps to avoid a small fishing vessel or some other hazard to navigation, and that this allowed the cargo in the holds (automobiles) to shift.I caught a brief glimpse of the vessel lying on her side as she was slowly capsizing and I think I may have seen a stabilizer fin poking out of the ship’s hull, amidships, below the waterline. But I didn’t get a good look at it and I may have been mistaken.

Stabilizers are airfoils, like stubby wings, which can be tilted to help keep a ship stable in a seaway, or while maneuvering. Most ships are kept stable by heavy ballast below the center of gravity or by a hull shape of complex curves which exerts buoyant forces which tend to counteract a heel. Typically, a vessel will rock and roll quite a bit through small angles of heel, (low initial stability) but righting forces quickly take over and keep the ship upright at extreme angles of heel (high final stability). Ships with this traditional design tend to rock considerably in light weather (people get seasick very easily), but are extremely resistant to capsize in heavy seas, or even when flooding catastrophically.

However, these complex hull shapes are expensive to design and build, usually have deep drafts (which limits their visits to deep-water ports) and they do not use space efficiently. The trend today is to design ships like flat bottom boxes to maximize cargo capacity for a given size and minimize draft. Stability is maintained by computer controlled mechanical stabilizers that counteract the vessel’s tendency to heel.

I have long suspected this type of stabilization is highly prone to mechanical (or computer) failure and is, by definition, almost worthless when the ship is stationary or moving slowly.

There was a severe accident on a cruise ship based in south Florida some time back which I suspect may have been caused by just this sort of material casualty. The liner suddenly underwent an extreme and unexpected heel and crew and passengers were thrown about violently, resulting in numerous injuries and considerable water taken aboard. This occurred while the ship was operating under normal conditions in good weather. No cause was announced for the accident, and although the stabilizers were never mentioned it appears to me a stabilzer suddenly deploying incorrectly, or locking into the wrong position, could explain the facts. I have commented before on the concessions made in hull design in order to maximize passenger capacity, shallow water anchorage, and ease of construction.

The cruise industry is very big in South Florida, and both the shipping companies and the local economy would benefit by not publicizing a mechanical cause to this type accident. Call me paranoid…