FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1963
1963 - 1131.PDF
Air-Cushion Vehicles FLIGHT International supplement, 25 April 1963 THE COCKERELL PAPERS Part Three Hovercraft Report No 1/1957; Decem ber 9th, 1957. ONE OF THE largest of Cockerell's early reports, this report of Hovercraft Limited (the inventor's own company) is a fundamental dissertation on the design of high-speed surface craft. Right at the outset he establishes the soundness of his approach:— Since we have none of us seen a 1,000- ton craft which can travel at 100 knots over the Atlantic in a gale, we do not know what it would look like, and we are therefore justified in pursuing any unfamiliar form until solid argument forces its rejection; and, in fact, the probability is that the correct solution will be something very different from anything that exists at present. After considering the speed limita tions of displacement ships, planing craft and hydrofoil craft, with some discussion on the proportions of drag due to wave generation and friction, he continues:— It would seem that there are only two ways of drastically reducing skin friction: either an air film must be introduced and maintained between the bottom of the vehicle and the surface of the water, or the bottom of the vehicle must be made to have no motion relative to the water, i.e., some form of wheel or belt system, or a combination of both systems. Having discussed the limitations on speed of existing craft—and, in this connection, the part played by skin- friction drag—Cockerell then examines the influence of the surface over which a high-speed craft may ride:— Water at 100 knots is more akin to concrete than to the gently flowing or stationary water that we know, and therefore it is more helpful in some ways to think along the lines of devising a vehicle which would be capable of travel ling over rough open country than to think of it as travelling over the yielding waves in which we bathe. If one considers the various existing surface vehicles—the motor car weighing a ton, the lorry of 20 tons, the tank- transporter of 100 tons, the train of 500 tons, or even the horse-drawn sleigh of a few hundredweight—they all have one thing in common which is not part of the design of any form of boat: and that is that they are sprung, to help them to deal with a rough surface. This would seem to be the second vital clue. This springing does more than just produce a soft ride, for, by making the 90 80 70 ^o 40 30 20 HOVER HEIGH JET WIDTI- 10 9 g 7 p 5 3 i ! i I 1 L THEORETICAL FIGURE PERFORMANCE ONF DFFLECTOF M,. _ // // / '/ '// —fp 1 / i //' / // // '/ Y WITH / X. y J yy y • XA 'V \ -0° \ - 45 O ^ <s —V JETS EXPERIMENTAL PERFORMANCE. I 30 40 50 60 70 8090 100 5 6 7 8 9 10 20 PRESSURE JET P, PRESSURE CUSHION P Basic experimental data obtained by Cockerell on his third research rig at Somerleyton, as noted in the text. The photograph below shows the rig itself, with tufting to indicate the local direction of airflow in the jet and cushion 62
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
