Dirigible

Dirigible (pronounced dir-i-juh-buhl or dih-rij-uh-buhl)

(1) An airship.

(2) A machine designed for or capable of being directed, controlled, or steered.

1583:  From the Latin dīrigere (to set straight), present active infinitive of dīrigō (steer, to direct) where it existed as an adjective with the meaning in the literal sense.  The use to describe airships dates from 1885, a direct borrowing from the French balloon dirigeable (steerable balloon), from the adjective dirigeable (capable of being directed or guided), a practice English would repeat with words like aileron and fuselage, reflecting the early French lead in aviation.  Dirigible is a noun & adjective, indirigibility & dirigibility are nouns and indirigible is an adjective; the noun plural is dirigibles. 

The Hindenburg, 1937

Frontal schematic of Hindenburg (LZ 129).

Built in the mid-1930s, Nazi Germany’s two Hindenburg-class dirigibles were hydrogen-filled, passenger-carrying rigid airships, the family named after Generalfeldmarschall Paul von Hindenburg (1847–1934; Reichspräsident (1925-1934) of the German Weimar Republic 1918-1933). They were the last of their type and the largest ever to fly, longer than three of the original Boeing 747s and only slightly shorter than RMS Titanic.  The first commissioned was Hindenburg (LZ 129) which undertook its maiden flight in March 1936 and powered by four Daimler-Benz DB602 V16 diesel engines rated at 890 kW (1190 horsepower), under neutral atmospheric conditions it typically cruised at 130 km/h (80 mph).  That made for leisurely transatlantic crossings (albeit much faster than ocean liners) but it could carry 72 passengers in some comfort as well as several tonnes for freight over a maximum range of 14,000 km (8700 miles).  By contrast, the Junkers Ju 52 (a contemporary airliner), although able to cruise faster at 210 km/h (130 mph) rarely carried more than 18 passengers with range restricted to a hardly intercontinental 1000 km (625 miles).  With a Berlin-New York ticket priced at the equivalent of around US$8000 in 2024 values, the big dirigible was the Concorde of its era and although obviously not supersonic, it was more luxurious and unlike the noisy, vibrating Ju 52, passengers enjoyed the comfort of small cabins, washrooms, a bar, a dining room and several lounges.  Although it may seem surprising given the craft's fiery demise, located within the body of the craft (surrounded by all that combustible hydrogen) was a smoking room.  To enter or leave the smoking room, passengers had to pass through an air-lock designed to ensure the flammable gas never came into contact with a naked flame, the barman's most important duty to check each of his customers as they went to leave, ensuring no forgetful smokers left with cigarettes still lit.

Hindenburg's interior was decorated in the then fashionable art deco "ocean liner" style: dining room (left), bar with a waiting bottle of Benedictine liqueur (centre) and lounge with world map annotated showing symbols illustrating the routes flown by the dirigible (right).

The safety record of the big dirigibles in the previous two decades had been patchy with a half-dozen crashes involving French, US and British craft with a death toll of some 250 souls.  Despite this, the Hindenburg operated a regular and profitable transatlantic passenger service for over a year, flying to both South and North America.  However, the designers were forced to use highly flammable hydrogen rather than inert helium because the US, the only country able to supply the necessary volume of the latter, refused on grounds of national security.  On 6 May 1937, while attempting to dock at Lakehurst Naval Air Station, New Jersey, the Hindenburg was destroyed by fire with the loss of 36 lives and although a variety of hypotheses have been suggested, the cause of ignition remains unknown.  The disaster shattered public confidence and marked an abrupt end of the passenger airship era, the Hindenburg’s sister-ship, the Graf Zeppelin never operated on a regular passenger service and scrapped in 1940.  Hitler's last word on the matter of the accident was "it was an act of God".  The combination of the Hindenburg disaster and the rapid improvement in the range and capacity of post-war airliners meant there was no return of the big passenger dirigibles, even among those manufacturers with access to ample supplies of helium.  Despite that, the things never went away and for decades there has been interest by both the military and commercial concerns in using them for a variety of purposes including as camera platforms, carriers of scientific instruments and survey vehicles for mining exploration and oceanographic research.  Dirigible the word however endured less well.  Preferred use now is the generic airship or, sometimes inaccurately given it’s technically different from the rigid or semi-rigid dirigible, the pleasing blimp.

Last moments of the Hindenburg, Lakehurst Naval Air Station, New Jersey, 6 May 1937.

One novel (although an adaptation of a concept in use for almost a century) use which remains at the proof of concept stage is as a lift vehicle for the LOHAN (Low Orbit Helium Assisted Navigator) and although there was no direct connection to Lindsay Lohan (not noted for her interest in aerospace matters), the project team cheerfully did admit the acronym was constructed as a publicity tool, blatantly trading on her notoriety (the name dating from 2012).  The idea is that because the cost of delivering a rocket-powered spaceplane into the stratosphere is so significant, if the travel from the ground to the critical altitude at which the rocket engine will ignite can be handled instead by a helium-filled dirigible, the economics of such devices become more compelling.  The concept is for the dirigible to carry a large number of rockets to an altitude of 65,000 feet (20,000 m) at which point they’re released, allowing their journey to continue to the planned altitude of some 80,000 feet (25,000 m), the dirigible returning to ground to be re-used for subsequent launches.  The initial testing plan was to use a large helium balloon to carry as small scale (3D-printed) rocket but despite years of negotiation, the developers were never able to secure a launch licence from US aviation authorities.

The LOHAN spaceplane.

Interestingly, the substantially amateur team found the greatest engineering challenge was not the lift device or the design of the spaceplane but ensuring the rocket reliably would fire as required, the thin atmosphere at 20,000 m containing only some 5% of the oxygen typically found as sea level, the solution being an exotic igniter-mix, a kind of super spark-plug which works when 12 miles (20 km) high.  Without the prototype able to be tested, it’s not clear if things are in abeyance.

Act

Act (pronounced akt)

(1) Anything done, being done, or to be done; deed; performance.

(2) The process of doing.

(3) A formal decision, law, or the like, by a legislature, ruler, court, or other authority; decree or edict; statute; judgment, resolve, or award (with initial capital when part of a name).  An act is created by a legislature passing a bill.

(4) An instrument or document stating something done or transacted.

(5) One of the main divisions of a play or opera.

(6) A short performance by one or more entertainers, usually part of a variety show or radio or television program or the personnel of such a group.

(7) A false show; pretense; feint.

(8) In scholasticism (a medieval school of philosophy), (1) activity in process; operation, (2) the principle or power of operation, (3) form as determining essence & (4) a state of realization, as opposed to potentiality (an occurrence effected by the volition of a human agent, usually opposed at least as regards its explanation to one which is causally determined).

(9) To do something; exert energy or force; be employed or operative.

(10) To reach, make, or issue a decision on some matter.

(11) To operate or function in a particular way; perform specific duties or functions.

(12) To produce an effect; perform a function; to behave or conduct oneself in a particular fashion.

(13) To pretend; feign.

(14) to represent (a fictitious or historical character) with one's person; to perform as an actor.

(15) To serve or substitute (usually followed by for).

(16) To actuate, to move to action; to actuate; to animate (obsolete).

(17) As ACT, the initialization for Australian Capital Territory, a federal territory created for the establishment of Canberra as Australia’s capital city.

(18) In certain English universities, a thesis maintained publicly by a candidate for a degree, or to show the proficiency of a student.

(19) In mathematics, construed with on or upon, of a group; to map via a homomorphism to a group of automorphisms.

(20) In Scottish law, to enact, decree (obsolete).

1350–1400: From the Middle English act & acte, from the Old French acte, from the Latin ācta (register of events), plural of āctum (decree, law (later “something done”)), noun use of the past participle of agere (to set in motion, drive, drive forward", hence "to do, perform" and figuratively "incite to action; keep in movement, stir up" a verb with a broad range of meaning in Latin, including "act on stage, play the part of; plead a cause at law; chase; carry off, steal”), the construct being āg- (past participle stem) + -tum (the neuter past participle suffix) and directly from the Latin āctus (a doing; a driving, impulse, a setting in motion; a part in a play), the construct being āg- + -tus (the suffix of verbal action); the ultimate source was the primitive Indo-European héǵeti. The word partially displaced deed (which endured also to enjoy a specific meaning in law), from the Old English dǣd (act, deed).  Source of it all was the primitive Indo-European root ag- (to drive, draw out or forth, move).  The present participle is acting, the past participle acted.

The theatrical (part of a play (from the 1510s)) and the early fifteenth century legislative senses of the word existed also in Latin although the idea of "one of a series of performances in a variety show" seems not to have been in use until the 1890s although such forms of entertainment were by then long-established.  The (usually disparaging) use to suggest a "display of exaggerated behavior" is from 1928, extended from the theatrical sense.  The "act of God” (a natural force or event uncontrollable by man) was first recorded in 1726 as a legal term to refer to matters in which plaintiffs could not sue for compensation or relief because the consequent losses could not by anyone have been “…guarded against by the ordinary exertions of human skill and prudence so as to prevent its effect.”  Even Adolf Hitler (who wasn't fond of of churches and priests (the Roman Catholic ones he called "black crows") found it often convenient to invoke the name of the Almighty) found the concept helpful, describing the destruction of the Hindenburg dirigible in 1937 as “an act of God”.  The word had been in the language of law for a while, an act in the 1590s understood as something "in the process" and legal scholars link this with the late sixteenth century use of act as a euphemism for "sexual intercourse”.

The verb was a mid fifteenth century development from the noun and most of the modern senses in English probably are from the noun.  In the mid 1400s, it began with the sense of "to act upon or adjudicate in legal matters” before from circa 1600 coming to be used in the familiar general meaning of "to do, perform, transact", extended to things in the sense of "do something, exert energy or force”, by 1751, a use which would become increasingly common in physics and cosmology.  In theatrical performances, from the 1590s it meant to "perform as an actor" (intransitive) and by the 1610s "represent by performance on the stage" (transitive). The meaning "perform specific duties or functions," often on a temporary basis, had come into use by 1804 and was given a new legitimacy when the Duke of Wellington (1769–1852; UK prime-minister 1828-1830) was described as “acting prime-minister” between November-December 1834 while awaiting the return from Italy of the king’s appointee.  One verb form which in general use didn’t survive was co-act ("to act together in a performance), noted from circa 1600 and which begat co-action; co-active; co-actor etc although co-act (and variations) is still sometimes used in scientific papers.

To “act on” in the sense of "to exert influence upon" entered general use in the 1810s, the adoption encouraged by the increasing appearance of the phrase in scientific literature.  To “act up” came by 1900 mean "be unruly" (in reference to a horse in the same way bolter (ie “to bolt” in the sense of “gallop off without warning”)) was used, a reversal of the earlier meaning "acting in accordance with a duty, expectation, or belief” which dates from 1645.  To “act out” (behave anti-socially) was part of the jargon of psychiatry noted first in 1974; it meant "expressing one's unconscious impulses or desires", following “acting out” (abnormal behavior caused by unconscious influences) from 1945.

The idiomatic forms are legion.  “To get into the act” (participate) dates from 1947 and “to get (one's) act together” (organize one's chaotic life) is said not to have been used until the mid-1970s which seems surprising but more than one source records this.  The idea of the “one-act” was borrowed from the literal “one act play” (a performance consisting of a single act), noted since 1888, the figurative use suggesting either brevity or inadequacy depending on context.  The verb overact (to go too far in action) faded from use except in its original sense from the theatre where it described an actor “playing a part with too much emphasis; an extravagant and unnatural manner”.  The theatrical slang encapsulating this was “chewing the scenery", which sounds modern but dates from the 1630s.  To “act one’s age” is to behave in a manner befitting the maturity one is presumed to have attained at a certain stage in life.  An “act of faith” is to embark on a course of action on either (1) a basis of trust rather than any guarantee or (2) as a demonstration one's religious faith.

Acts & Scenes

William Shakespeare agitprop.

The act is a major division in many performance pieces such as plays, film, opera etc and frequently (though not of necessity) consists of a number of scenes, the concept dating from the theatre of antiquity.  Traditionally, the division of a work into acts and scenes was undertaken by the author but such delineations, especially of older material, can be made by critics or those applying academic analysis and where the notion of authorship can become blurred (such as a film director interpreting a text), there can be variations from the original, something sometimes controversial.  The application of the concept (and the labels) of acts and scenes is widely applied to many forms of entertainment, sometimes to provide a structural framework and sometimes, one suspects, to lend a not always deserved gravitas.  In the production of more recent material, commercial imperatives can also dictate the divisions, the single intermission a common occurrence which renders a performance inherently a two-stage event in some sense.

The five-act structure.

The number of acts in a piece need not bear any relationship to its length although this certainly is the general tendency, a one act play usually a deliberately short work.  Although the five act structure had until the early nineteenth century been most frequently used by playwrights, many analysts suggest this was a kind of formalism, a deferential (and perhaps devotional) nod to William Shakespeare (circa 1564–1616) who usually adhered to the five act model in his plays.  The bard had his reasons and there is a discernible rhythm as his five acts evolve but none the less, even in the most intricate of his plays, it’s possible convincingly to map onto them the now conventional three act structure.

The three act structure.

The three-act structure can simply and unexceptionally be understood as the beginning, the middle and the end.  It is in act one that the nature of the conflict is established and the identities of the protagonist and antagonist are revealed (or in the case of the latter, at least alluded to.  During the second act, difficulties will arise, these the dramatic device which seem to create the insurmountable obstacle which much defeat the protagonist.  In the third act, there will be a climax (and perhaps anti-climaxes), the point at which all seems finally lost for the protagonist.  However, despite it all, the protagonist prevails and, even if they die, the circumstances will be such that resolution attained is sufficient to satisfy the moral point to be made.

F Scott Fitzgerald with wife Zelda (Zelda Sayre, 1900-1948).

F Scott Fitzgerald’s (1896–1940) oft-quoted phrase “there are no second acts in American lives” appears as a fragment in his posthumously published, unfinished novel The Last Tycoon (1941) but he first published it in the early 1930s in the essay My Lost City, a kind of love letter to New York.  The quote is frequently misunderstood as an observation that for those Americans who suffer disgrace or destitution, there is no redemption, no coming back.

Second (third, fourth etc) act specialist: Lindsay Lohan mug-shots 2007-2011.

However, from politics to pop culture, there are many examples of temporarily disreputable Americans resurrecting their public lives from all but the most ignominious opprobrium.  Fitzgerald was a professional writer and his observation was an allusion to the structure used by playwrights in traditional three-act theater: (1) problem, (2) complication & (3) solution.  He thought the nature of the American mind was to prefer to skip the second act, going straight from a problem to finding a solution.  His point was well-made and it’s one of the themes of the narrative which underlies the discussions (which became arguments and sometimes squabbles) of military and political strategy between Washington and London during the Second World War.

Kammback

Kammback (pronounced cam-bak)

A motif in automotive styling (originally dictated by wind tunnel findings during research into aerodynamic properties) in which rear of the car slopes downwards before being abruptly cut off to terminate in a vertical or near-vertical surface.  The things are known also as the Kamm tail (K-tail).

1950s (the actual design first appearing in 1938): The construct was Kamm + back.  The surname Kamm (related to Kamp) was of Germanic or Jewish (Ashkenazic) origin and translates literally from the German as “comb”.  The German comb was from the Middle High German kamb, kambe, kam & kamme and the Yiddish kam (comb).  Genealogists conclude Kamm was probably an metonymic occupational surname for someone who either made or sold combs, a common tool used for grooming or for textile work such as carding or combing wool.  There’s also the possibility the name of some Kamm clans could have been of topographic origin because in German, Kamm can also mean “ridge” or “crest” of a hill, mountain or some other elevation; it could thus have referred to someone who lived near such a geographical feature.  Less likely is that some arose from nicknames based on physical features or personal characteristics with Kamm used to describe someone with hair resembling a comb or someone with a sharp or distinctive personality.  The surname emerged in the Middle Ages, a time when hereditary family names were becoming more common in German-speaking regions and in addition to the presence in Germany, exists at various scale in areas with a historic patter of German migration (notably the north-eastern US and South Australia.

Back was from the Middle English bak, from the Old English bæc, from the Proto-West Germanic bak, from the Proto-Germanic bakam & baką which may be related to the primitive Indo-European beg- (to bend).  In other European languages there was also the Middle Low German bak (back), from the Old Saxon bak, the West Frisian bekling (chair back), the Old High German bah and the Swedish and Norwegian bak; there are no documented connections outside the Germanic and in other modern Germanic languages the cognates mostly have been ousted in this sense by words akin to Modern English ridge such as Danish ryg and the German Rücken.  At one time, many Indo-European languages may have distinguished the horizontal back of an animal or geographic formation such as a mountain range from the upright back of a human while in some cases a modern word for "back" may come from a word related to “spine” such as the Italian schiena or Russian spina or “shoulder”, the examples including the Spanish espalda & Polish plecy.

Tail was from the Middle English tail, tayl & teil (hindmost part of an animal), from the Old English tægl & tægel (tail), from the Proto-Germanic taglaz & taglą (hair, fibre; hair of a tail) (source also of the Old High German zagal, the German Zagel (tail), the dialectal German Zagel (penis), the Old Norse tagl (horse's tail) and the Gothic tagl (hair), from the primitive Indo-European doklos, from a suffixed form of the roots dok & dek- (something long and thin (referring to such things as fringe, lock of hair, horsetail & to tear, fray, shred)), source also of the Old Irish dual (lock of hair) and the Sanskrit dasah (fringe, wick).  It was cognate with the Scots tail (tail), the Dutch teil (tail, haulm, blade), the Low German Tagel (twisted scourge, whip of thongs and ropes; end of a rope), the dialectal Danish tavl (hair of the tail), the Swedish tagel (hair of the tail, horsehair), the Norwegian tagl (tail), the Icelandic tagl (tail, horsetail, ponytail), and the Gothic tagl (hair). In some senses, development appears to have been by a generalization of the usual opposition between head and tail.  The Oxford English Dictionary (OED) suggest the primary sense, at least among the Germanic tongues, seems to have been "hairy tail," or just "tuft of hair," but already in Old English the word was applied to the hairless "tails" of worms, bees etc.  The alternative suggestion is that the notion common to all is that of the "long, slender shape."  It served as an adjective from the 1670s.  A long obsolete Old English word for tail was steort.  Kammback is a noun; the noun plural is kammbacks.  No lexicographer seems to have listed Kammbackesque, Kammbacklike or Kammbackish as standard adjectives but, given the extent of the deviances from Professor Kamm's original which are still labelled as “Kammbacks”, they might be useful forms.  Who wouldn't want to be able to use terms like the comparative “more Kammbackish” and the superlative “most Kammbackish”?

Some notable Kammbacks

The Kammback (also known as the Kamm tail) was named after German engineer & aerodynamicist Professor Wunibald Kamm (1893–1966) who during the 1930s pioneered the shape, his work assisted greatly by some chicanery within the Nazi military-industrial complex which enabled the FKFA (Forschungsinstituts für Kraftfahrwesen und Fahrzeugmotoren Stuttgart (Research Institute of Automotive Engineering and Vehicle Engines Stuttgart) institute he established in 1930s to secure funding to construct a full-sized wind tunnel equipped with a two-part steel treadmill in the floor and an 8.8 metre (350 inch) diameter axial fan, able to drive air at up to 400 km/h (250 mph).  What the two concentric floor turntables allowed was that as well as enabling turbulence to be studied from the side on the running steel belt, slip angles were also possible.   At the time, it was the most modern structure of its kind on the planet, the very existence of which was owed to the priority afforded by the Nazis to re-armament, especially the development of modern airframes, most of the money eventually coming from the Reichs-Luftfahrt-Ministerium (RLM, the State Air Ministry).

A classic Kammback on a 1970 Fiat 850 Coupé (1965-1973), one of the last of the generation of post-war mainstream rear-engined cars built in Western Europe.

While Professor’s Kamm’s work on automobile shapes continued, increasingly the facility became focused on military contracts, contributing to an extraordinary range of novel aircraft designs, some revolutionary and most of which would never reach production.  All of this ceased in July 1944 when the facility was severely damaged in air-raids by Royal Air Force (RAF) Bomber Command, a costly campaign in which one mission incurred a loss-ration of 20% and it wasn’t until the late 1940s that reconstruction began after it was acquired by Daimler-Benz AG which enlarged and modernized the machinery, the early fruits including the 300 SL (the W194, first gullwing coupé) which won the 1952 Le Mans 24 hour race and the W196R “streamliner” Grand Prix race cars which created such a sensation in 1954.  Although he wasn’t part of “Operation Paperclip” (the US project which secured (by various means including the military “smuggling” them into the country despite many being wanted by those investigating war crimes and crimes against humanity) Professor Kann was acknowledged as one of the world’s leading authorities on turbulence and between 1947-1953 was part of the team working at Wright-Patterson Air Force Base in Dayton, Ohio.  Some of what was undertaken then remains classified but it can be assumed it was all related to military projects and what would later become the space program.

The Kammback which really wasn't: 1976 Chevrolet Vega Kammback.

One often misunderstood aspect of the Kamm tail is that the aerodynamic benefits are realized only if the flat, vertical surface created was no more than about 50% of the total area of the vehicle (as viewed directly from the back).  That’s why even designs which don’t conform to the requirements are often casually referred to as “Kammbacks” and in the US, Chevrolet were cynically opportunistic when the Vega range (1970-1977) included what was nothing more than a two-door station wagon (estate), it was named “Vega Kammback”.  Actually, even the existence of the thing in the US was unusual because at that stage, General Motors (GM) really “didn’t like” small station wagons but many critics did agree the Kammback was the best looking of the Vega’s body-styles.

2023 Ford Mustang coupe (left) and convertible (right).  Three of the Mean Girls (2004) ensemble (Karen Smith (Amanda Seyfried (b 1985)), Gretchen Wieners (Lacey Chabert (b 1982)) & Cady Heron (Lindsay Lohan (b 1986)) in 2023 filmed a commercial for Pepsi Corporation, one of the props a 2023 Ford Mustang convertible.  So ubiquitous has the Kammback become that its now unnoticed (except in its absence), one quirk being that when convertibles are created from such a base, many of the aerodynamic advantages are lost, one reason why (all else being equal which is rarely the case) a convertible will tend to have slightly inferior performance and slightly higher fuel consumption.

The knowledge gained from aero-engine development during World War I (1914-1918) meant even the mainstream engines of the 1920s were developing much more power so the speeds of cars were rising.  Some intrepid types also took advantage of the number of huge, powerful aero-engines being sold cheaply as “war surplus”, installing them is powerboats and racing cars, resulting in some fast machines and not a few fatalities.  However, it became clear the law of diminishing returns applied as speeds rose because while an increase of 100 horsepower might make possible an increase in top speed from 100 to 120 mph, another 100 hp might yield only another 10 mph; wind resistance increasing too much for the power to overcome.  Thus the interest in aerodynamics, then usually called “streamlining” something which, coincidently, produced some memorable art deco designs buy the engineers were interested in higher speeds and lower fuel consumption for a given quantum of energy input (fuel consumption).

2014 Shelby American Cobra 427 50^th Anniversary Edition in aluminium (left) and 1964 Shelby Daytona Coupe (right).

The AC Shelby Cobra (1962-1967) was small, light and powerful which made it an instant success on the race tracks but, ruggedly handsome though it was, its aerodynamics limited the top speed and on the some fast, open European circuits it gave away as much as 50 km/h (30 mph) to less powerful but more streamlined machines.  More power wasn’t the solution but a new Kammback body was and the Daytona duly won its class in the 1965 World Sports Car Championship.  All used the 289 cubic in (4.7 litre) Ford Windsor V8 although one briefly was fitted with a 390 (6.5) FE V8 and the planned 427 (7.0) version (CSX3027, the so-called “Daytona Super Coupe”) was never completed until sold by Shelby some 17 years later in a “rummage sale”.  The Kammback Daytona was the work of US designer Pete Brock (b 1936) and in a macabre coincidence, his namesake, the Australian racing driver Peter Brock (1945–2006) was killed while competing (in retirement) in a replica Daytona Coupe during the now defunct Targa West (2005-2021) in Western Australia.

Before the Kammback, the state of the aerodynamic art was the airship-like "streamliner" which, although it probably didn't cross the engineers' minds, owed something to the train of a bride's gown.  1939 Lincoln Zephyr V12 Coupe (left) and 1937 Mercedes-Benz 540K (W29) Special Roadster (originally delivered to Mohammad Zahir Shah (1914–2007; the last King of Afghanistan 1933-1973) (right).

What soon became clear was that the shape of the dirigible (better known as the “airship” or “blimp”) was close to ideal and needed to be tweaked only by honing it into a “teardrop shape” with a rounded nose, extending to a long, tapered tail, a shape which in the 1930s caught the imagination of designers who rendered some memorable designs although the most famous were impractical and inefficient in terms of packaging, thus suitable only for the then small market niche which sought speed.  It was to try to gain the benefits of streamlining in a shape more suitable for mass production that Professor Kamm and others took their slide-rules to the wind tunnel began to experiment.  The solution which emerged was to terminate the lovely, long flowing roofline with an abrupt end at a surface which was either vertical or close to it, an unexpected benefit being an improvement in high-speed stability, obviating the need for (a usually central) stabilizing fin (a la an aircraft’s tail).  By 1938, BMW had produced a car with a Kammback and although World War II (1938-1945) interrupted development by the late 1940s the shape had begun to appear in showrooms and in little more than ten years it was common in specially bodied racing cars.  That didn’t mean the allure of the teardrop went away because the aerodynamicists (who now had both access to bigger wind tunnels in which higher speeds could be tested and the novelty of computers which could process previously unimaginable quantities of data) could still prove ultimate slipperiness could be attained only with the teardrop.

Pre-Kammback & non-Kammback.  Porsche 917LH (Langheck (long tail)) at Arnage, Le Mans 24 hour, 1969 (left) and 2020 McLaren Speedtail (right).  Such things are now possible.

It was this which convinced Porsche to use such a tail on their revolutionary 917 in 1969 and having encountered no stability issues on their test track, sent the car to the circuits where it proved as fast as expected.  Unfortunately, the size of the Porsche test facility limited the 917 to 290 km/h (180 mph) and when on the long straights of some European circuits when speeds exceeded 320 km/h, it was clear the thing was lethally unstable.  Although the drivers killed at the wheel of the early 917s didn’t die at such velocities, it was understood it would be only a matter of time so the rear bodywork was redesigned.  When in 2018 McLaren returned to the teardrop for the “Speedtail” (a car which sacrificed just about anything not mandated by law in the quest for top speed), it was able to achieve a safe (it’s a relative term) 400 km/h (250 mph) because advances in aerodynamics, computing, materials & hydraulics had made such things possible although the packaging inefficiencies remained, something not significant for the target market.