Skeg

Skeg (pronounced skeg)

(1) In shipbuilding, a fin-like projection supporting a rudder and protecting the propeller(s) at its lower end, located abaft a sternpost or rudderpost.

(2) In the design of smaller boats, an extension of the keel, designed to improve steering.

(3) In the slang of naval architects (in certain contexts), a stump or branch (the after-part of a ship's keel).

(4) In the slang of the General Motors (GM) stylists, a “lower fin”, matching the upper on the rear of 1961-1962 Cadillacs.

(5) The fin which acts as a stabilizer on a surfboard.  To suffer some injury after being hit by one of these fins is to be “skegged”.

(6) In Australian slang, a surfer; a person who leads the lifestyle of a surfer (used also derisively in the form “fake skeg” of those who adopt the style an appearance without actually surfing.

(7) A type of wild plum (obsolete).

(8) A kind of oat (obsolete).

(9) In Northern English dialectal use, a look or glance.

(10) In many cultures, a slang term applied to youth suggesting slovenliness, a predilection to petty crime and other anti-social behavior; also used widely in Scottish slang for a surprising variety of purposes including legs, trousers, dirt, scotch eggs, sex and women of loose virtue.

1590–1600: From a dialectal term for a stump, branch, or wooden peg, from the Dutch scheg (cutwater), of Scandinavian origin and related to the Swedish skog and the Old Norse & Icelandic skegg (projection on the stern of a boat).  In some Nordic languages, skegg means “beard” and was from the Old Norse skegg, from the Proto-Germanic skaggiją, from the primitive Indo-European skek, kek-, skeg & keg- (to jump, skip, move, hurry).  The name of the English coastal town of Skegness is though a construct of the Old Norse skegg (beard) + -nes (headland) and was thought a reference to the geography, the original settlement situated farther east at the mouth of The Wash (thus jutting out like a beard from a face).  A link with the Old Norse name Skeggi is thought unlikely.  The skegs of nautical architecture should not be confused with the homophone Sceggs, the acronym for students of Sydney Church of England Girls Grammar school (S.C.E.G.G.S.), seen also in the adjectival forms sceggesque & sceggish (one whose style suggests something similar to the stereotypical student of the school).  Skeg is a noun; the noun plural is skegs.

Lindsay Lohan in wet suit, with surfboard, Malibu, 2011.  The stabilizing skeg is the black protrusion at the back of the board.

On nautical vessels, skegs where they exist fulfill a significant function but they are not an essential part of hull design.  A skeg is an external structural feature, a vertical tapering projection permanently fixed at the aft, usually close to the centre-line.  Most are located in front of the rudder and structurally can often be considered a sternward extension of the keel (the internal, longitudinal members which lend much strength of the hull).  Although in military vessels there are additional functions, the moist significant contribution of a skeg is in hydrodynamics, a skeg designed to influence the flow patterns and thus affecting the dynamics of both the rudder (which is usually in line with the skeg) and propeller(s).  The design is thus a finely tuned equation because while a skeg inherently induces drag, the way it alters the flow pattern can reduces the drag and resistance suffered by the rudder and propeller(s), essentially by transforming the turbulent characteristics of the flow to laminar at the stern.  Historically, skegs were a vital component in maintaining a course and that’s still an important consideration in smaller vessels but in larger craft, improved rudder and advanced navigational as well as stabilization technologies like thrusters have meant skegs are no longer of the same significance in maintaining directionality.

An US Navy Iowa class battleship, showing the inner set of propeller shafts wholly enclosed in a pair of skegs.  On the big ships, the skegs were designed also as load-bearing supports while in dry-dock.

In the modern age, skegs became an unusual feature on warships, a relative few so equipped and the designs varied, some with only a few of their shafts inside skegs while others encased all.  While the traditional design imperatives were shared with other ships, for navies, they also offered the advantage of affording some degree of protection for rudders and propellers against torpedo attack.  Historically, another important attribute of skegs was what they add to a hull’s structural strength, making the (inherently weaker) stern resistant to outside forces and all the last of the US Navy’s dreadnoughts featured skegs.  Their hulls narrowed towards the stern and to save weight lacked the sternpost plates the British, German and Japanese navies always fitted to their battleships and the skegs compensated for this, offering a hull with similar rigidity.

The US Navy’s South Dakota class battleships were fitted with an unusual set of skegs, the design dictated by the relatively short hull, the large outboard skegs helping to reduce the adverse effects of fluid dynamics induced by the hull’s abrupt end.

However, advantages in engineering and metallurgy meant much of the functionality afforded by skegs could be achieved in other ways and skegs became unfashionable in naval architecture.  The modeling and simulations made possible by supercomputers meant hull designs could be rendered which mastered the turbulence caused by fluid dynamics so rudders and propellers were less affected so the skeg was in many cases a source of performance-sapping skin-friction drag with little compensating benefit.  Indeed, not only did this hamper performance, in some cases excessive vibration was caused, something which could only to a degree be ameliorated by changes to the propellers’ configurations.

Cadillac’s Skegs, 1961-1962

Cadillac Coupe DeVille, (1959, left & 1960 right).

The 1959 Cadillac’s tail-fins are the best remembered and most emblematic of the brief, extraordinary era during which the absurdly macropterous flourished.  They’re rightly known as “peak-fin” but it’s a myth they were the tallest because, measured from the ground, those on the 1961 Imperial are just under an inch (25 mm) more vertiginous.  The attractions of the style however were fading and in 1960, Cadillac and Chrysler (Ford never really got involved) began to tone them down.  Another cultural phenomenon is that because of the large number of pink 1959 Cadillacs which now exist, many assume they were a common sight when new, the things perhaps made memorable by the sight of the one owned by the admirable Jayne Mansfield (1933–1967).  However, the factory never made a pink 1959 Cadillac and in the era, it was only in 1956 such a color was on the option list and Ms Mansfield had one of those while her 1959 convertible received a custom re-paint.

Cadillac Coupe de Ville, (1961, left & 1962 right).

For the 1961 & 1962 range the fins became lower still but in compensation, the design staff added a lower fin and these, informally they called “skegs”.

1961 Cadillac Coupe de Ville, (left), one of the design proposals for 1961 (centre) & captured German V2 rocket (right).

While of course an extravagance, the skegs could have part of something even wilder because among the design proposals which emerged from the General Motors Advanced Design Studios was one which clearly was the ultimate expression of the motif of the 1950s which borrowed so much from the aerospace industry,  The proposed fins essentially were those of ballistic missiles which for decades were an evolution from the German Vergeltungswaffen zwei (V-2), developed first by the German military with the code name Aggregat 4 (A4).  Vergeltungswaffen is translated variously as "retaliatory weapons" or "reprisal weapons" but in English use is often written as “vengeance weapons”.  Aerodynamically, presumably the proposal has something to commend it and it proceeded far enough into the selection for an expensive, full-sized clay model to be rendered (one wonders what the rejected sketches looked like) but ultimately the longer though somehow more restrained skegs were preferred.

The 1961 Cadillac: The long (left) and slightly less long (right) of it.

One quirk of Cadillac’s brief embrace of the skeg was there were two iterations: skeg long and skeg short.  Whether in response to or in anticipation of some owners preferring their Cadillac in a more conveniently sized package, between 1961-1963 a “short-deck” option was made available on certain body styles.  Offered first on the six-window Sedan de Ville, an encouraging 3,756 were built so the option was in 1962 offered on the four-window Sixty Two Town Sedan but sales actually dropped to 2600, the decline in interest confirmed the next year when only 1575 of the four-window Park Avenue Sedan de Ville were sold.  Using the same 129.5 inch (3289 mm) wheelbase as the regular models but eight inches (200 mm) shorter in overall length (215 vs 223 inches (5461 vs 5664 mm)), space utilization was obviously a little better but the market had spoken.  With fewer than eight-thousand of the short-deck models sold across three seasons while the standard editions shipped in the tens of thousands, the flirtation with (slightly) more efficient packaging was abandoned for 1964; in the course of the following decade, Cadillacs would grow another seven inches (178 mm) and gain over 400 lb (181 kg).

For 1963, the short-deck models returned for another dismal season but the skegs were abandoned, never to return.  The fins however the design studio found harder to forsake, conscious perhaps it was on the 1948 Cadillac they’d first appeared.  Then, modestly sized, they’d been an allusion to the tail-planes used on the twin-boomed Lockheed P-38 Lightning (1939) but the fashion had passed and the fins had to go so, inch by inch, there was a retreat from the heights and exuberance of 1959 until in 1966 the fins were vestigial, a hint which for decades would be retained.

A gang of four Sceggs, Sydney, Australia.