To the Edge of the Possible

Part 4, the final part of my historical/technical analysis of US high speed destroyers, has just appeared in Warship International, Vol. 50 issue 4.  This completes what was about a 15-year effort, and it should be no surprise that I learned a few things while doing it.

When I presented part 1 to the American Society of Naval Engineers annual symposium in 1997, I started my presentation by saying the high speed period in destroyer design resembled the horsepower war in American cars of the 1960's -- a period when I was too young to have a driver's license but was still an interested spectator.  In reality, there must be a better comparison in history, because the efficiency of high speed destroyers was not a brute-force thing; they had power to weight ratios about like a 1950 VW Beetle, yet could still slice through their own bow-waves into a semi-planing regime.

The second revelation was that the proportions and coefficients of the type were established in a time period when the methods I used to rediscover those elements were not yet known.  How designers and builders figured out what proportions to use is a mystery.  When they figured it out must have been around the time of the Civil War or just afterward.  Again, my earlier notions (aided by published sources, to be sure) that steam yacht builders were at the forefront because owners were essentially racing them doesn't seem to be consistent with chronology -- the smaller, high speed "express" launches hadn't yet come into vogue when fast torpedo boats first appeared with the proportions later to be used in destroyers.

So, while I'm happy with the articles, there is more research that could be done on this subject.

Light Sport Aircraft

One of the things that happened in aviation since I got my license is the light sport aircraft or LSA (and its corresponding special license, the Sport Pilot license.) Like the Recreational license and the ultralight aircraft that preceded it, the light sport aircraft is officialdom's response to the spiralling cost of aircraft ownership and the resultant decline in the pilot population. A light sport aircraft is of limited performance capability with only two seats and a modest top speed of about 120 knots in level flight. Gross weight is also limited to about 1200 pounds. In exchange for these limitations, manufacturers are able to follow a streamlined certification process that does not involve actual FAA inspections of the aircraft or most parts used in it. This is supposed to result in a less expensive certification process.

But what does it mean to the pilot? Is an LSA as safe as a Part 23 approved airplane, and how much utility do you give up? On Sunday, Sept. 11, 2011, I took a lesson in the LSA pictured. I wasn't particularly trying to answer these questions. The FBO I'm now flying with, Trident Aircraft at Bay Bridge Airport, has somewhat stricter standards than the FAA for currency. They like you to fly at least every 60 days (the FAA requires 90, and that's only if you carry passengers) or you have to do a mini-recurrency with an instructor, which adds considerable expense without, I felt, returning much in the way of either recreation or skill-building for someone who has had a license for more than a decade. Since the LSA at Bay Bridge airport is considerably less expensive per hour even than a 172, reflecting lower capital, maintenance, and fuel costs, I figured I could use it for local flights to maintain currency. In addition, it is suitable for going to Ridgely Airport where the ultralights and hang gliders fly on weekends. The LSA's short landing and takeoff runs and light weight would make it easier to taxi off the pavement onto the grass without getting stuck; there's no paved parking area in Ridgely.

This particular LSA, a Remos GX, is made in Germany and it is tiny. The instructor took one look at my flight bag and suggested I leave it behind because there was no room for it! I found this was true. The plane has 2 seats and a small, maybe 2 cubic feet, cargo space that has a 60 pound capacity but can't be accessed in flight because the pilot's seat covers the door giving access to it when the seat is occupied. Head room is ample but leg room is tight for someone my size. Just as well there are no toe brakes because I probably couldn't engage them. Outward visibility is excellent, however, and controls are feather light and hyper-responsive. There's a little mini-PFD in front of each seat and a GPS with an extra large screen in between those two PFD's, plus standby conventional airspeed and altimeter instruments. All 3 electronic displays have their own batteries so they don't go dark immediately when you turn off the airplane master switch. The wings fold so you can push the plane onto a trailer to tow home behind your car. Anyway, it was about as different as it's possible to be from a Cessna, so I had an interesting flight. I expect I'll need one more lesson to be able to fly it by myself.

Is it as safe as a Part 23 airplane? I think it probably is. It's stressed for +4 and -2 G's, which is somewhat beyond the "Normal" category requirements from the FAA, and in addition, it has a Ballistic Recovery System with a parachute that can lower the whole airplane and occupants to the ground should something break that makes the plane uncontrollable in midair.

How is it to fly? In a word, it's weird. Its designers evidently started from a clean sheet of paper. In general layout it resembles a Cessna in that it's high wing, strut braced, and conventional tail. It's also tricycle gear with very effective, precision nosewheel steering that works through the rudder pedals. Beyond that, controls just go their own way. A World War II-style stick is used for roll and pitch control, with a button on it for electric pitch trim (no mechanical trim at all). This trim acts on a section of the elevator whose upper surface is smooth composite with no hinges. The linkage from the trim motor slides a link fore and aft on the lower surface of the tab to produce aeroelastic forces on the elevator. The seats don't slide; to adjust them for your size you lift them out of the airplane, releasing a linkage first that retracts rods from a series of holes in the Kevlar and carbon fiber airframe. then you move the seat to the correct position and re-engage the rods into the appropriate holes. Needless to say you can't adjust it in flight. The doors are gullwing, retracting up against the lower surfaces of the wings. Visibility ahead and to the sides is excellent, almost bubble canopy good, because of the size of the windshield and side windows. The doors are almost all Plexiglas. The brake lever is between the seats, and for those who drove sports cars with a handbrake in that position, you might as well recognize you need total re-training, because the lever must be pushed, not pulled, to stop the landing roll. To facilitate using this brake, there is an auxiliary throttle on the upper left of the panel that the left-seater can manipulate with his left hand while his right is busy stopping the airplane.

Speaking of sports cars, getting into the Remos resembles what those of us of a certain age remember in connection with the 1966 Austin-Healey Sprite. Except, you need to step up, rather than down, to get into the cockpit, and after you're in, you still need to move one leg over the stick. There isn't much room between it and the underside of the dashboard so if your legs are long they'd better not be too fat.

The engine is weird too. It's geared, screaming at 5200 RPM on takeoff, and produces 100 shp. However, that's enough, with the sophisticated, 3-bladed propeller with swept tips, to allow very rapid climbs. It has both air and liquid cooling systems and therefore coolant level must be checked as well as oil during preflight. It's a Rotax 912, a common ultralight and LSA powerplant that has also powered many homebuilt and experimental aircraft. It sounds about like a lawnmower. It has an oil cooler with a flap to close it off, and that's used for temperature control in flight, not just applied for warmup. It even has a choke, but it pops back in instantly when the engine fires, probably a safety feature to avoid its becoming engaged in flight. There is no mixture lever, just the two throttles, because something in the carburetion adjusts for air density changes with altitude. Indeed, where it can differ from an ordinary airplane, it does.

Handling continues the weird theme. Rudder must be used sparingly, because the ailerons have been rigged so that most of their effectiveness is in dumping lift off the "down" wing rather than adding it to the "up" one. this means very little adverse yaw. Stalls are rather abrupt wing drops to the right with power off; I expect they will be even more abrupt to the left with power on. there's no stall alarm and I couldn't feel a pre-stall buffet, but maybe you need more familiarity with the airplane to detect the buffet. Vy, best glide, and approach speed are all the same, which makes for not so much to memorize. since the airplane is not approved for flight in IMC, there is no pitot heat, even though this one had enough instrumentation that you could practice approaches in it. Takeoffs and landings are extremely short but otherwise conventional. Of course you have to wait to flare till you think you must be about to hit the ground, because the seating position is a lot lower than anything I've flown before. Nevertheless my first landing was nearly perfect; the second was a little hard (flared too high).

LSA's seem to be gaining fast in popularity. Most are imported; even Cessna's new one is made in China. But, they are much less expensive than "real" airplanes; a Remos costs about half of a Cessna 172 and has almost as much performance if you think in terms of speed and climb rate. The 172 can carry 2 additional passengers, and maybe even more important, you can file IFR with it. However, for many flight "missions" in a general aviation aircraft neither the extra seats nor instrument capability is really needed. I think the LSA is here to stay.

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.

Cirrus SR 20

In a recent business trip to New York (unfortunately, aborted by a dental emergency -- don't ask), I tried to schedule a preliminary visit by air. I found that even though I am checked out in 2 C172 SP's with G1000's, neither of them was available for an operation requiring that I keep it overnight and return it the next day. I think the problem is that 172's fly so often for training that you have to reserve them really far in advance to get them for a substantial period.

Anyway, being aware that my local FBO has only 2 172's (only one with G1000) now, because they no longer have the 182 that was my favorite, plus larger airplanes they use for charter operations, I knew I could get no relief from that direction. The larger FBO at Bay Bridge Airport has so many airplanes that I just asked the instructor who had checked me out in their 172 SP if they had other airplanes with very similar avionics, and he suggested the Cirrus SR 20.

So a few weeks ago I had an "avionics intro" to the SR 20 where an instructor parked the airplane close to a hangar where it could be plugged in and we could demonstrate the avionics. The "perspective" system in the Cirrus is essentially like the G1000 in the sense it has a PFD and MFD with almost all the features in common (software by the same company, Garmin). There's an additional keypad for typing in frequencies, which is easier than scrolling through all the letters when you know you want a "z". The keypad is alphabetic -- not a standard "qwerty" layout, but I figure I'll get used to that pretty easily. The autopilot is totally different but maybe easier, since it's integrated, taking its target altitude and altimeter setting off the PFD display so there are less redundant things to set. I decided to check out.

Cirrus has a rather elaborate syllabus that takes you through a somewhat regimented checkout process, but of course how onerous that is depends on how ready the instructor is to customize it to the individual student. In the case of Bay Bridge Airport it seems the instructor is quite willing to customize, both because I have a good facility with the G1000 and also because our first lesson happened on a day with favorable weather for flight and I pointed out that even though the syllabus said the first lesson was ground only, it would be a shame to waste a good day.

So, last Friday, I did steep turns, stalls, and normal takeoffs and landings. The SR 20 is different from airplanes I've flown before. It's essentially all composite (in fact, the POH says the factory needs to approve colors and brands before an owner can have his airplane repainted because the material could be damaged by solar radiation without sufficient protection). While it has fixed gear, its modern aerodynamics allows it to fly at Piper Arrow speeds or even a little more even with the streamlined gear hanging out. (I use the Arrow as a comparison because the SR 20's engine is the same size, 200 hp). Its controls are odd, a "side stick" emerging from the fuselage interior, so that the pilot flies with his left hand and the instructor with his right. (With a conventional yoke, both pilots can fly with the same hand.) The stick is extremely responsive with a very fast roll rate and somewhat slower pitch rate that's still impressive compared to other airplanes I've flown. However, those favorable features come at a price -- higher forces in pitch if you don't use the very fast, almost hyper 2-axis electric trim very often. Also, ground handling is somewhat clumsy because steering at low speeds is only by differential braking; the nosewheel casters. On landing, the fast pitch response can cause a tail strike if you flare too much or too quickly.

Safety features are unusual but reassuring: a ballistic recovery system, although it isn't rated up to VNE for this heavy, fast airplane, airbags integrated into the 4-point seatbelts, plus synthetic vision technology (SVT) for the PFD that's so good it gives you an image of the runway numbers in the screen as you pass over them in reality. But the big deal is terrain that's shown in what looks almost like 3-D on the screen. Of course there's also the XM weather and collision avoidance features I've praised before in using the G1000 in other airplanes.

While the SR 20 cruises at speeds in the mid 130's without much effort, it is handicapped compared, say, to a 182, by rather long takeoff and landing distances. At Easton that wouldn't matter but Bay Bridge is about 2700 feet long, and the SR 20 needs about 2500 in zero wind. That means you'd better land in the right direction if the wind favors one direction even a very little!

It appears the SR 20 offers some useful features compared to traditional, all-metal aircraft of the kind that were around when I was learning to fly. While I don't like it as much as a Bonanza, we need to keep that in perspective (pun not intended) -- a Bonanza costs on the order of $900,000, and for that price you can have 2, or even maybe 3 SR 20's.

Nautical Literacy

What should a sailor know to distinguish him or her from a landlubber? Never mind how I was led to consider this question, just think about it.


This resembles (sorry) disputes about the literary canon that were a big deal for a while in academia and politics, but seem to have died down today. Why? Because being nautically literate seems to mean a lot more than just being a competent boat operator. A person can be a whiz at handling a small powerboat, know the Rules of the Road by heart, never confuse port with starboard, and still be functionally illiterate in the sense I mean.


I think nautical literacy includes some surface knowledge of the history. One should at least recognize a few important names (Horatio Nelson, Isambard K. Brunel, William Webb, and Charlie Barr for the English-speaking). One should at least recognize most of the sailing rigs and the terms for sails and the major control lines, although picking out a mizzen topgallant sail on a sail plan is more than I expect. You should know that the bathroom is called a "head" -- and why. You should be able to tell a tug from an offshore supply boat, and know some of the general terms like port and starboard. While being able to handle a vessel counts for something, I don't think that skill necessarily confers nautical literacy.


Can a person be nautically literate without any seamanship skills? Maybe someone so badly afflicted with seasickness that within a boat length of the pier he starts to feel so queasy he can't give the boat his full attention? I think maybe so, although of course many of the already nautically literate will disagree.

Design Aesthetics

A picture in "AOPA Pilot" magazine reminded me of a subject I last wrote about in 1971...in an essay on college admissions applications. In that essay I remarked on the fact that ships (I might as well have said airplanes, cars, or any number of devices with a definite transportation or other practical function) are also aesthetically pleasing -- or that they should be.

In the current AOPA Pilot is an article on the diamond DA 42 NG, a small twin with diesel engines. The picture on the cover of the magazine shows probably the ugliest nacelles installed on an airplane since before World War II. That got me thinking about why I thought they were so ugly, and I came to the conclusion that aesthetics aren't transcendent: they must be appropriate rather than beautiful in any grandiose way. The blunt, blocky nacelles on the DA 42 are annoying to the eye because the rest of the airplane has a graceful, almost exaggerated aero look, betraying its glider ancestry and the efficient aerodynamics that go along with it. To have such bluff nacelles coexisting with that kind of fuselage (composite, with compound curvature and a high aspect wing with winglets) just isn't appropriate (see photo 1, from AOPA's Web site).

More everyday examples abound. While some people disapprove of sport-utility vehicles (SUV's) on principle, I take a balanced view: they are designed for hauling big loads over surfaces that might not be as "improved" as most US roads. That being so, why do some of the manufacturers try to make them look aerodynamic (and in the process, reduce the internal volume that makes them useful for their intended function) as well as reduce outward visibility? While I'm not an extreme partisan that form must follow function, I think form must be appropriate to the function. A shape like this (Photo 2) doesn't "say" it can take 6 people and hundreds of pounds of cargo over miles of dirt roads. A shape like this (Photo 3) does!

It's the same in ships and airplanes (and probably lots of other devices I'm not as familiar with.) Aesthetics is everywhere because we're human -- something I was exposed to early on in my education when I found that in the ancient world, utilitarian devices like weapons, armor, clothes, pottery, buildings, and shoes were often decorated with not only patterns but also artwork that is considered almost like fine art today. In ships and airplanes, though, it's usually the overall shape and layout that makes or breaks the aesthetics. A DC-3 (photo 4) looks exactly like what it is -- a sky bus. Most pilots like the way it looks because its aesthetics are appropriate to its function. A Constellation, on the other hand, goes aeons beyond what it is and is graceful and elegant, too. I like its design even more.

In ships, a World War II destroyer is fast and looks it. A battleship dominates the environment with its big guns and you can tell that by looking at it, too. Today's ships? Boxes to enclose their "payloads" -- not aesthetic at all.

Aesthetics are everywhere. Too bad so much of it is "bad" (inappropriate) aesthetics!

Force Levels

Discussion on the MarHist Listserv has triggered some thoughts on this subject. What force level is sufficient for a navy? This may at first glance seem like a stupid, or political, or philosophical question, but I think its answer lies mainly with psychology, and therefore to answer it is quite difficult.

From the point of view of theorists like Capt. Mahan, one may suppose that an adequate force level would be one that would be noticeably superior to that of your nearest competitor. Such a force level should lead a rational competitor to avoid combat.

This has proven to be inadequate. In the Napoleonic Wars, Britain boasted 108 ships of the line in 1796, while France disposed of but 71 in 1789, and some were no doubt no longer serviceable by the time war broke out. This is about a 30% advantage to the British and yet it was no deterrent. In 1914, Britain had 24 dreadnoughts and Germany had 17, even a bigger advantage percentage-wise, and of course, war broke out anyway. (Britain seized two Turkish battleships under construction in Britain that later served as HMS Agincourt and Erin, and in 1915, HMS Canada, previously under construction for Chile, also joined the Grand Fleet, giving it a huge numerical advantage.)

Evidently, a 10% advantage, what to the uninitiated would seem a significant one, will not be enough to deter war from breaking out, although it might be enough that the war could be won. However, in the two examples cited, the respective wars dragged on for many bloody years.

In Japanese samurai lore there is a sort of just so story (possibly written by Musashi?) that bears on this issue. A samurai visits a swordsmith. The swordsmith demonstrates his wares by taking a katana to a nearby stream, and putting the blade into the water, edge upstream. It's fall (or spring) and either fallen leaves or cherry blossom petals are flowing downstream with the fast current. They split, a foot upstream of the blade, and go either side of it because they "know" it's so sharp it will slice them in two just from the force of the current. There's a "moral" to the story that goes something like "The greatest warrior need never draw weapon." This would lead us to the suggestion that overwhelming superiority in force is necessary to deter opponents from challenging a navy.

However, we should also realize that in both examples, wars broke out not only as a result of naval rivalry (although that did exist at the time) but for ideological and political reasons, respectively, and indeed those reasons are much more common reasons for wars to occur than merely naval rivalry. It may be less important what the force levels are from a deterrence point of view, and we should be more concerned about being able to win the war should it break out.