Secrets of the Spitfire: The Story of Beverley Shenstone, The Man Who Perfected the Elliptical Wing by Lance Cole

Author:Lance Cole [Cole, Lance]
Language: eng
Format: epub
ISBN: 9781781599969
Publisher: Pen and Sword
Published: 2012-08-19T07:00:00+00:00

The Details of Design – the Boundary Layer and the Wing Root Fillet and Tail Designs

The tuning of the ellipse, of creating a uniquely re-shaped and reformed ellipse and adding to it the boundary layer effect, was to become Shenstone’s forensically minded area of focus in the 1930s. Intriguingly, at the same time, his uncle, Allen G. Shenstone, FRS, who went on to become one of the twentieth century’s leading atomic physicists, worked on the gaseous boundary layer in his atomic physics research at Princetown USA – where the world of mathematics and science in the 1930s saw many advances. Beverley Shenstone’s diaries record contact at the time between the two families, and he visited America in 1934 as part of the Vickers delegation, but it is impossible to know if the two Shenstone men shared any of their thoughts with each other over the subject in 1934. But one thing that is obvious is that both men were operating at the leading edge of research thinking.

Shenstone studied the boundary layer and aircraft skin design with Junkers and Lippisch, and talked with Prandtl and von Karman, two of the leading boundary layer gurus of their time.

By January 1937, Shenstone had published a major paper25 that he had spent some time researching and writing during his Supermarine years on the theory of boundary layer control techniques, and ultimately that of mechanically sucking airflow from the boundary layer through holes in an aircraft’s wing or fuselage. Before that, from 1929, he had begun a close study of the boundary layer – the thin sheath of air that lies very close to an aircraft’s skin that is subject to friction-related, localized speed changes, which in turn affects airflow further out from the aircraft’s skin. Some of this airflow slows down and stagnates above it, and the airflow increases it speed. Between these layers is the ‘boundary’ layer.

By creating an especially smoothed and shaped skin surface, by tuning the movement and speed of airflow patterns and their behaviour across the wing’s skin, Shenstone tuned these factors to reduce localized turbulence and drag by altering and speeding up the boundary layer airflow – this was why Shenstone insisted on the flush rivets of the Spitfire’s construction.

Prior to experiments with perforated or sucking wings, this smoothing and sculpting of the Spitfire’s skin friction boundary airflow was the first step in applying boundary layer thinking to a high-performance fighter aircraft wing. Shenstone was inspired by hydrodynamic studies he had made as a post graduate student in Canada, and by hydrofoil research. The effects of the Junkers designs’ skin corrugations, and the smooth skin criteria on advanced German glider designs and on delta shapes, only served to confirm to Shenstone that the effect of aircraft skin surface design on the boundary layer, was the key to improving performance. It would be nearly a decade before the first boundary layer laminar flow wing, that of the P-51 Mustang, would see production.

Shenstone was also quite happy to admit that the

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