*Department of Biological Science, University of York, Heslington, York YO1 5DD
The effect of size on the optimal shapes of gliding insects and seeds
Article first published online: 23 MAR 2009
Journal of Zoology
Volume 219, Issue 1, pages 61–69, September 1989
How to Cite
Ennos, A. R. (1989), The effect of size on the optimal shapes of gliding insects and seeds. Journal of Zoology, 219: 61–69. doi: 10.1111/j.1469-7998.1989.tb02565.x
- Issue published online: 23 MAR 2009
- Article first published online: 23 MAR 2009
- Accepted 13 December 1988
Conventional aerodynamic arguments suggest that possession of high aspect ratio wings will always improve the flight performance of glides. Drag and power will be minimized at intermediate flight speeds. It is shown, however, that as the aspect ratio increases, these minimum drag speeds are reduced, and will fall below the stall speed of the glider. This will happen at lower aspect ratios in small gliders, which operate at higher profile drag coefficients. Increasing the aspect ratio further will improve performance less than this analysis suggests.
A detailed analysis is developed to calculate the optimum shape of small gliders. Profile drag increases with aspect ratio, owing to the fall in the Reynolds number, while induced drag falls with increasing aspect ratio. Minimum drag will be encountered and hence the glide angle will be minimized at intermediate values of aspect ratio. Best glide angles are achieved at low speeds (high lift coefficients) and the optimum aspect ratio increases with the mass of the glider.
Small natural gliders possess large, low aspect ratio wings. The aspect ratios are generally somewhat below those which would produce the best glide angle at stall speed, but should give a reasonable performance over a range of speeds.