Clark Y is the name of a particular airfoil profile, widely used in general purpose

aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engine ...

designs, and much studied in

aerodynamics Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dy ...

over the years. The profile was designed in 1922 by Virginius E. Clark using thickness distribution of the German-developed Goettingen 398 airfoil.Piccirillo, Albert, "The Clark Y Airfoil - A Historical Retrospective," SAE/AIAA paper 2000-01-5517, presented at the World Aviation Congress & Exposition, October 10, 2000, San Diego, California. The airfoil has a thickness of 11.7 percent and is flat on the lower surface aft of 30 percent of chord. The flat bottom simplifies angle measurements on propellers, and makes for easy construction of wings. For many applications the Clark Y has been an adequate airfoil section; it gives reasonable overall performance in respect of its

lift-to-drag ratio In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air. It describes the aerodynamic efficiency under gi ...

, and has gentle and relatively benign stall characteristics. But the flat lower surface is not optimal from an aerodynamic perspective, and it is rarely used in modern designs.

The Clark YH airfoil is similar but with a reflexed (turned up)

trailing edge The trailing edge of an aerodynamic surface such as a wing is its rear edge, where the airflow separated by the leading edge meets.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 521. Aviation Supplies & Academics, 199 ...

producing a more positive pitching moment reducing the horizontal tail load required to trim an aircraft.

Applications

Aircraft

The

Lockheed Vega The Lockheed Vega is an American five- to seven-seat high-wing monoplane airliner built by the Lockheed Corporation starting in 1927. It became famous for its use by a number of record-breaking pilots who were attracted to the rugged and very l ...

and Spirit of St. Louis are two of the better known aircraft using the Clark Y profile, while the

Ilyushin Il-2 The Ilyushin Il-2 ( Russian: Илью́шин Ил-2) is a ground-attack plane that was produced by the Soviet Union in large numbers during the Second World War. The word ''shturmovík'' (Cyrillic: штурмовик), the generic Russian term ...

and

Hawker Hurricane The Hawker Hurricane is a British single-seat fighter aircraft of the 1930s–40s which was designed and predominantly built by Hawker Aircraft Ltd. for service with the Royal Air Force (RAF). It was overshadowed in the public consciousness b ...

are examples of mass-produced users of the Clark YH.Lednicer, David, (15 September 2010)
The Incomplete Guide to Airfoil Usage
. Page not found 22 June 2019 The Northrop Tacit Blue stealth technology demonstrator aircraft also used a Clark Y. The Clark Y was chosen as its flat bottom worked well with the design goal of a low radar cross-section.

Model aircraft

The Clark Y has found favor for the construction of model aircraft, thanks to the flight performance that the section offers at medium Reynolds number airflows. Applications on model aircraft is very wide, ranging from free-flight gliders through to multi-engined radio control scale models. The Clark Y is appealing for its near-flat lower surface, which aids in the construction of wings on plans mounted on a flat construction board. Inexperienced modellers are more readily able to build model aircraft which provide a good flight performance with benign stalling characteristics.Martin Simons, ''Model Aeroplane Aerodynamics'', Model & Allied Publications 1978. Chapter 7 - 9, Aerofoil Sections.

Cars

An inverted Clark Y airfoil was used on the spoilers of the

Dodge Charger Daytona Dodge produced three separate models with the name Dodge Charger Daytona, all of which were modified Dodge Chargers. The name was taken from Daytona Beach, Florida, which was an early center for auto racing and still hosts the Daytona 500, NASC ...

and

Plymouth Superbird The Plymouth Superbird is a highly modified, short-lived version of the Plymouth Road Runner with applied graphic images as well as a distinctive horn sound both referencing the popular ''Looney Tunes'' cartoon character the Road Runner. It was ...

. (29 June 2005)
From NASA to NASCAR
retrieved 29 April 2017

Applications

Some of the better-known aircraft that use the Clark Y and YH: ;Clark Y *

Aeronca 50 Chief The Aeronca Model 50 Chief was an American light plane of the late 1930s. Consumer demand for more comfort, longer range and better instrumentation resulted in its development in 1938, powered by a 50-horsepower (37-kilowatt) Continental, Frankl ...

* Avia B.122 * Consolidated PT-1 to Fleet Fawn (all intermediate designs used the same section) * Curtiss P-6 Hawk (most of the Curtiss Hawks used the same section) * Heath Parasol *

to Orion (all intermediate designs used the same section) * Polikarpov R-5 * Ryan Brougham and related types including the Spirit of St. Louis * Stinson Reliant * Vultee V-11 * Waco Standard and Custom Cabin series ;Clark YH * Currie Wot *

and Il-10 *

Mikoyan-Gurevich MiG-1 The Mikoyan-Gurevich MiG-1 (russian: Микоян-Гуревич МиГ-1) was a Soviet fighter aircraft of World War II that was designed to meet a requirement for a high-altitude fighter issued in 1939. To minimize demand on strategic materia ...

and MiG-3 * Miles Magister *

Nanchang CJ-6 The Nanchang CJ-6 () is a Chinese basic trainer aircraft designed and built by the Nanchang Aircraft Factory (now Hongdu Aviation) for use by the People's Liberation Army Air Force (PLAAF). Development The CJ-6 (Chu Jiao 初教 = Chuji Jiaoli ...

Polikarpov I-153 The Polikarpov I-153 ''Chaika'' (Russian ''Чайка'', "Seagull") was a late 1930s Soviet biplane fighter. Developed as an advanced version of the I-15 with a retractable undercarriage, the I-153 fought in the Soviet-Japanese combats in Mon ...

Potez 39 The Potez 39 was a French two-seat single-engined parasol wing monoplane reconnaissance and observation aircraft of the 1930s. Development The Potez 39 was designed to a 1928 requirement for an aircraft to replace the Potez 25 and Breguet 19 mach ...

* Stolp SA-900 V-Star *

Yakovlev Yak-1 The Yakovlev Yak-1 (russian: Яковлев Як-1) was a Soviet fighter aircraft of World War II. The Yak-1 was a single-seat monoplane with a composite structure and wooden wings; production began in early 1940.Angelucci and Matricardi 197 ...

, 3 and 9 * Yakovlev Yak-50

References

{{reflist Aerodynamics Aircraft wing design