Basic geometrical parameters of paraglider wing selection criterion

Аuthors

Shved Y. V.

e-mail: yuriy-shved@mail.ru

Abstract

The article considers wing design parameters, having the greatest impact on its inductive drag. It becomes up- to-date due to the fact, that with low speed flying vehicles, and paragliders among them, inductive component of a sing drag appears to be several times greater than its airfoil part component.

From Expressions obtained show that with flying vehicle specified mass and its vertical overload the value of inductive drag of its wing will be inversely proportional to the square of its wingspan and square of its speed. Thus, with equal wingspan and speed, either narrow wing with high aspect ratio and high-lift airfoil, or wide wing with low aspect ratio and low-lift airfoil having equal lifting force will possess the same inductive drag.

This implies also the futility of replacement of wide wing by several wings with a number of narrow chordes. Even without considering polyplane wings negative interaction with total area equal to paraglider wing area and wingspan, polyplane wing inductive drag will not be less than that for a monoplane. It is shown for gliding systems, how we can determine required C_ya by C_xa and gliding speed, or find gliding speed by aerodynamic coefficients in terms of gliding system characteristics. In both cases we can calculate glide angle and corresponding to it system aerodynamic efficiency in terms of wing parameters; and then locate it relative to shroud lines in such a way that provide required wing incidence angle during gliding.

Any two airfoils having the same Kmax, create the same drag at a given lifting force, but the airfoil of the same quality with greater lifting force will require smaller wing chord and, accordingly, greater aspect ratio and minor stiffness with one and the same wing inductive drag. Besides, taking into account that extra lifting force value under lift devices deviation is proportional to wing area, we are interested at maximally wide chord. Thus, airfoils, providing minimum C_ya with the same aerodynamic efficiency, are preferable.

It is worth mentioning, that the demand for atlas of special airfoils for soft wings in the frame of aerodynamic quality, load-bearing capacity in deformed state, as well as safety, still remains impelling and unsatisfied.

Keywords:

paraglider, soft wing, wing aspect ratio, wing span, lift-drag ratio, airfoil

References

1. Ivanov P.I. Proektirovanie, izgotovlenie i ispytaniya paraplanov (Design, production and tests of paraplanes), Feodosiya, Grand-S plyus, 2007, 281 p.

2. Pyshnov V.S. Iz istorii letatelnykh apparatov (From history of flying vehicles), Moscow, Mashinostroenie, 1968, 105 p.

3. Malte Janduda. Patent DE 102006007905, 30.08.2007.

4. Pieri Frederic, Armant Luc, Dagault David. Patent FR 2972422, 14.09.12.

5. Subbotin A.A. Patent RU 2410288, 27.01.2011.

6. Shved Yu.V. Patent RU 2389644 С2, 20.05.2010.