High Speed Destroyers: to the Edge of the Possible

I've written parts 1 and 2 (1997, 2002) of a projected "Trilogy" of technical articles on the hydrodynamics of high speed destroyers of the interwar period. Recently I've been doing research for Part 3, which I thought would not be too hard. Why? Because, having explored proportions and coefficients in parts 1 and 2, and having further discovered that neither experienced much change over the period I was planning to cover (1919-1942), I figured just writing the chronology would be easy. Documentary evidence for this recent period isn't like ancient Greece -- there are plenty of primary sources and if you're too lazy to use them, quite a few good secondary sources.

Well, actually doing research speedily made me change my opinion. Not only had I got the dates wrong -- in fact, the first US high speed destroyers were commissioned in 1918, not 1919, and the last weren't commissioned till 1953 -- but when I started getting information from two correspondents as well as from Google Books, I realized the story wasn't quite so simple as I thought. And the secondary sources weren't as good as I thought.

The basic outlines of the story are as I supposed: the proportions, displacement-length of 40 to 50, prismatic in the low 0.60's, midsection coefficient around 0.80 -- were discovered in the pre-World War I period and designers stuck with them to the end. However, increasing the size of World War I destroyers wasn't possible without also reducing the speed-length ratio. This is because resistance per ton is constant at "equivalent speed" (same Froude number) but absolute speed gets faster as size goes up. Power being resistance times speed means you need more power per ton as size increases...which is why there needed to be continual improvement in engine power density and also reductions in hull resistance per ton through improved hull form to allow the ships to set records for trial speeds in the 1930's. The picture shows USS Dunlap making 39+ knots on the measured mile off Rockport, Maine, in 1937.

But why the drive to higher speed? The military value of destroyer performance (compared with armament, cruising range, and sensors) came under more scrutiny during World War II and speed lost out in the Sumner and Gearing classes. The "need for speed" seems to have originated with the first destroyers created by the Royal Navy in 1893, which immediately started setting speed records on trials. (The precedent was set by torpedo boats in the 19th century, and it's arguable that they are the ultimate source of the emphasis on destroyer speed). These early destroyer records caught the imagination of naval officers as much as the general public (Rudyard Kipling was impressed enough that he wrote a poem, "The Destroyers," after riding one of them on trials in 1898). If the need for speed could affect the normally sensible British, it was only a matter of time before it caught the interest of the people whose ancestors had raced clipper ships around the Horn.

It might also be significant that the periods when speed was most important were times when overt war wasn't happening. Perhaps competition in a less violent form still needed to take place ...I'll leave that to those with more psychological expertise. But it's a fact that after issuing an official report, sponsored by Theodore Roosevelt himself, that said destroyers needed to be more seaworthy and longer range, and didn't need even the speed they had at the time (this was in 1905), ten-plus years later not only did the US ignore that report but through the 1930's it produced progressively more highly tuned designs, optimized for top speed. Doing that required designers to probe arcane phenomena such as cavitation, learning a great deal about high-powered, small warships and driving every feature of their design to the most favorable corner of the envelope in order to reach "the edge of the possible."

Britain, France, Germany, Japan, and Italy certainly also produced high speed destroyers; I believe Soviet Russia must have also although I haven't looked at the less comprehensive information that has reached the public domain in the West about that period in Russian history. So, that would mean they served in at least 6 and probably 7 navies. The French had the fastest of all, making 45 knots on trials without using any of the features the US developed to optimize the flow off the stern to flatten out the stern wave. Germany pioneered the stern wedge that does even more than the subtle shaping favored by American designers to optimize a design for extreme speeds.

While wedges are in common use in warships today, and the David Taylor Model Basin has recently developed a new form of stern "flap" that offeres even more all around performance, the high speed destroyer able to make more than 35 knots on trials no longer serves in any navy. A few still exist as museum ships; most have been scrapped.

To deliberately misquote Miss Austen, it is not surprising that relatively few high speed destroyers were built or that none are still in use; it is astonishing that any ever existed .

Part 3 is shaping up to be a rather complex tale. Let's hope Warship International continues to show interest in publishing it and doesn't find it too long and cumbersome.