Research Note

the Austrian triple-decker wooden battleship Kaiser (centre of picture) ramming the Italian ironclad Re di Portogallo

Fought between the Italians and Austrians on July 20, 1866 (Lissa Day is just a few days from now. . . ) the battle was decided by the imaginative tactics of the Austrian Admiral, Tegetthoff. Outgunned, outnumbers and out armored by the Italian fleet, he turned the tables by reviving the ancient tactic of ramming.

Because it was one of the few naval actions fought between steam-powered and armored ships in open waters prior to 1890, it had a disproportionate influence on ship design. Tegetthoff's tactics worked because naval gunnery had not caught up to hull design. The guns were theoretically capable of sinking a ship before it could ram, but 1860s gunlaying prevented the guns from being able to actually do so. Tegetthoff deserved the victory because he realized that, and used his fleet in a manner that allowed him to exploit that factor.

Because of the decisive nature of the Austrian victory, many naval architects felt that they should ensure that their ships could also use ramming as a weapon. So, they added ram bows. Better a ship with a ram bow that did not need it than a ship without one that did. Besides, the ram bow created a really cool-looking bow wave.

At the speeds of pre-dreadnaught battleships circa 1870-1890 the ram bow did not significantly reduce speed. (The resistance goes up as the square of the speed, and at low speeds -- below 15-18 knots -- the bow wave resistance is not that big a factor.) However, once ships got faster, the ram bow often acted as a brake. Eventually the marginal utility of the ram bow was outweighed by the increased resistance, and they stopped using them -- really starting about 1890 -- 25 years after Lissa.

One interesting curiosity that I was told of when I was in college, learning to be a naval architect, was that the ram bow contributed to the development of the bulbous bow. Some grad students were doing towing tank tests of hulls for a thesis. The ship they had been using was unavailable, and they substituted an old battleship hull with a ram bow. The resistance was below what was predicted, and one of them was sharp enough to realize that the ram was partially filling in a low-pressure area at the foot of the bow. A little more tow-tank work and they had the geometry of the bulbous bow figured out.

The story I hear is that this took place in the 1920s, and the grad students did not have enough pull to convince people of the contra-intuitive performance of putting a big bulge on the bow of your hull form. But they saved the idea until the 1940s when they were respected and senior naval architects and made the idea stick then.
{Mark Lardas}

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