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FAQ

Wingtip-Classifications

Since the winggrid has a different topology compared to other wing-tip devices, it is essential to classify
it and understand its effects.

Properties	Authors
practical limit span_efficiency	Zimmer 83	Kroo 95	La Roche 96
parameter h/b compares vertical dimension h of configuration to span b	pure geometrical classification criteria	mix of geometry and downwash-wake criteria	downwash-wake parameters only vortex-spacing and vortex-core Spreiter & Sacks
e=1.1 h/b=0	contour/straight	planar with nonplanar wake	contour
e=1.4 with h/b=0.2	simple wingtips/ endplates	nonplanar monoplane	endplate
e=1.2 h/b>0.2	slotted edge/fanned partial	nonplanar monoplane	open fanlike
e=3.0 with h/b<0.05 for Winggrid	N.A.	N.A.	closed multiple Winggrid/ Spiroid
e=1.5 with h/b=0.2	N.A.	multiplanes/box/strut/ closed, C-Wing	N.A.

second row explains assessment criteria of the different authors
span efficiency is the efficiency relative to an elliptical wing
N.A. = not available
95 = year of publication

References:

H. Zimmer, The aerodynamic optimization of wings at subsonic speeds and the influence of wingtip design, NASA TM-88534 1987 (translation of dissertation, Stuttgart 83).

Ilan Kroo, John McMasters, Stephen C. Smith, Highly Nonplanar Lifting Systems, Transportation beyond 2000: technologies needed for engineering design, NASA Langley Research Center, Hampton, VA, September 26-28, 1995.

U. La Roche and S. Palffy, WING-GRID, a Novel Device for Reduction of Induced Drag on Wings, Proceedings ICAS 96, Sorrento, ITALY, September 8-13, 1996.

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Updated: 31 January, 2007