Clark Y
Encyclopedia
Clark Y is the name of a particular aerofoil
profile, widely used in general purpose aircraft
designs, and much studied in aerodynamics
over the years. The profile was designed in 1922 by Virginius E. Clark
. The airfoil has a thickness of 11.7 percent and is flat on the lower surface from 30 percent of chord
back. The flat bottom simplifies angle measurements on propellers, and makes for easy construction of wings on a flat surface.
The Lockheed Vega
is one example of the Clark Y used in practice. For many applications the Clark Y has been adequate; it gives reasonable overall performance in respect of its lift-to-drag ratio
, and has gentle and relatively benign stall
characteristics. But the flat lower surface is sub-optimal from an aerodynamic perspective, and it is rarely used in new designs. The Spirit of St. Louis
used the Clark Y; the Piper Cub used the quite similar USA 35B.
The Clark YH airfoil was the same but with a reflexed (turned up) trailing edge producing a more positive pitching moment
for improved longitudinal stability. The Hawker Hurricane
used this profile. Мany Soviet
aircraft of the 1930s and 1940s including all of the World War II
Yakovlev
fighters and MiG-3
used the Clark YH airfoil (Shavrov 1994).
The Clark Y is appealing thanks to its high camber, which produces a very good lift-to-drag ratio on comparatively lightweight balsa models, and for its near-horizontal lower surface, which aids in the accurate construction of wings on plans mounted on a flat construction board.
Young and inexperienced modellers are thus able to build model aircraft which provide a good flight performance due entirely to its aerofoil shape. The benign stalling characteristics of the airfoil are another aid, as this allows an inexperienced radio-control model hobbyist a better possibility of recovering from a stall in flight, to the benefit of the model.
The depth of the section lends itself to easier wing repair, as the modeller will often then have better access to balsa structural elements. In addition, the Clark Y section's depth also permits the flush installation of what are considered "standard" sized R/C servo motors within a wing for actuation of ailerons, flaps etc. , without an excessive reduction in performance.
Airfoil
An airfoil or aerofoil is the shape of a wing or blade or sail as seen in cross-section....
profile, widely used in general purpose aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft 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 engines.Although...
designs, and much studied in aerodynamics
Aerodynamics
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...
over the years. The profile was designed in 1922 by Virginius E. Clark
Virginius E. Clark
Virginius Evans Clark was an American World War I engineer. Clark designed the 1922 Clark Y airfoil used by many early aircraft.-Biography:...
. The airfoil has a thickness of 11.7 percent and is flat on the lower surface from 30 percent of chord
Chord (aircraft)
In aeronautics, chord refers to the imaginary straight line joining the trailing edge and the center of curvature of the leading edge of the cross-section of an airfoil...
back. The flat bottom simplifies angle measurements on propellers, and makes for easy construction of wings on a flat surface.
The Lockheed Vega
Lockheed Vega
|-See also:-References:NotesCitationsBibliography* Allen, Richard Sanders. Revolution in the Sky: Those Fabulous Lockheeds, The Pilots Who Flew Them. Brattleboro, Vermont: The Stephen Greene Press, 1964....
is one example of the Clark Y used in practice. For many applications the Clark Y has been adequate; it gives reasonable overall performance in respect of its lift-to-drag ratio
Lift-to-drag ratio
In aerodynamics, the lift-to-drag ratio, or L/D ratio, is the amount of lift generated by a wing or vehicle, divided by the drag it creates by moving through the air...
, and has gentle and relatively benign stall
Stall (flight)
In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs when the critical angle of attack of the foil is exceeded...
characteristics. But the flat lower surface is sub-optimal from an aerodynamic perspective, and it is rarely used in new designs. The Spirit of St. Louis
Spirit of St. Louis
The Spirit of St. Louis is the custom-built, single engine, single-seat monoplane that was flown solo by Charles Lindbergh on May 20–21, 1927, on the first non-stop flight from New York to Paris for which Lindbergh won the $25,000 Orteig Prize.Lindbergh took off in the Spirit from Roosevelt...
used the Clark Y; the Piper Cub used the quite similar USA 35B.
The Clark YH airfoil was the same but with a reflexed (turned up) trailing edge producing a more positive pitching moment
Pitching moment
In aerodynamics, the pitching moment on an airfoil is the moment produced by the aerodynamic force on the airfoil if that aerodynamic force is considered to be applied, not at the center of pressure, but at the aerodynamic center of the airfoil...
for improved longitudinal stability. The Hawker Hurricane
Hawker Hurricane
The Hawker Hurricane is a British single-seat fighter aircraft that was designed and predominantly built by Hawker Aircraft Ltd for the Royal Air Force...
used this profile. Мany Soviet
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
aircraft of the 1930s and 1940s including all of the World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
Yakovlev
Yakovlev
The Yak Aircraft Corporation is a Russian aircraft designer and manufacturer...
fighters and MiG-3
Mikoyan-Gurevich MiG-3
The Mikoyan-Gurevich MiG-3 was a Soviet fighter aircraft used during World War II. It was a development of the MiG-1 by the OKO of Zavod No. 1 to remedy problems that had been found during the MiG-1's development and operations. It replaced the MiG-1 on the production line at Factory No...
used the Clark YH airfoil (Shavrov 1994).
Model aircraft
The Clark Y has found tremendous favour for the construction of model aircraft, thanks to the flight performance that the section offers at medium Reynolds number airflows. Application on model aircraft is very wide, ranging from free-flight gliders through to multi-engined radio control scale models.The Clark Y is appealing thanks to its high camber, which produces a very good lift-to-drag ratio on comparatively lightweight balsa models, and for its near-horizontal lower surface, which aids in the accurate construction of wings on plans mounted on a flat construction board.
Young and inexperienced modellers are thus able to build model aircraft which provide a good flight performance due entirely to its aerofoil shape. The benign stalling characteristics of the airfoil are another aid, as this allows an inexperienced radio-control model hobbyist a better possibility of recovering from a stall in flight, to the benefit of the model.
The depth of the section lends itself to easier wing repair, as the modeller will often then have better access to balsa structural elements. In addition, the Clark Y section's depth also permits the flush installation of what are considered "standard" sized R/C servo motors within a wing for actuation of ailerons, flaps etc. , without an excessive reduction in performance.