Clark Y is the name of a particular

airfoil An airfoil (American English) or aerofoil (British English) is a streamlined body that is capable of generating significantly more Lift (force), lift than Drag (physics), drag. Wings, sails and propeller blades are examples of airfoils. Foil (fl ...

profile, widely used in general purpose

aircraft An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...

designs, and much studied in

aerodynamics Aerodynamics () is the study of the motion of atmosphere of Earth, air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dynamics and its subfield of gas dynamics, and is an ...

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, and has gentle and relatively benign stall characteristics. 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, 1997. ...

producing a more positive

pitching moment In aerodynamics, the pitching moment on an airfoil is the Moment (physics), moment (or torque) produced by the aerodynamic force with respect to the aerodynamic center on the airfoil . The pitching moment on the wing of an airplane is part of ...

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 its high speed and lo ...

and

Spirit of St. Louis The ''Spirit of St. Louis'' (formally the Ryan NYP, registration: N-X-211) is the custom-built, single-engine, single-seat, high-wing monoplane that Charles Lindbergh flew on May 20–21, 1927, on the Charles Lindbergh#New York–Paris flight ...

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 by ...

are examples of mass-produced users of the Clark YH.Lednicer, David
The Incomplete Guide to Airfoil Usage
The

Northrop Tacit Blue The Northrop Tacit Blue is a technology demonstrator aircraft created to demonstrate that a low-observable Stealth technology, stealth surveillance aircraft with a low probability of intercept radar, low-probability-of-intercept radar (LPIR) and ...

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 In fluid dynamics, the Reynolds number () is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between Inertia, inertial and viscous forces. At low Reynolds numbers, flows tend to ...

airflows. Applications range 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 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 Road Runner. It was th ...

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

Aircraft

Some of the better-known aircraft that use the Clark Y and YH: ;Clark Y * Aeronca 50 Chief * 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

* Stinson Reliant *

Vultee V-11 The Vultee V-11 and V-12 were United States, American stressed-skin monocoque monoplane attack aircraft of the 1930s. Developed from the Vultee V-1 single-engined airliner, the V-11 and V-12 were purchased by several nations for their armed forc ...

* Waco Standard and Custom Cabin series ;Clark YH * Currie Wot *

and Il-10 * Mikoyan-Gurevich MiG-1 and MiG-3 * Miles Magister * Nanchang CJ-6 * Polikarpov I-153 * Potez 39 * Stolp SA-900 V-Star * Yakovlev Yak-1, 3 and 9 * Yakovlev Yak-50

References

{{reflist

External links

Clark Y airfoil at airfoiltools.com
including coordinate data
Clary YH airfoil at airfoiltools.com
Aerodynamics Aircraft wing design