FLIGHT International supplement, 28 February 1963 Air-Cushion Vehicles

Mr Herb Bartlett, of Washington, USA is an indefatigable ACV experimenter: these are some of his successful designs, referred to below

world, and can supply their products for use in air-cushion vehicles as well as in snow sleds, aircraft, helicopters and industrial applications. After being carved all the propellers are covered with a newly developed epoxy coat to make them impervious to moisture; a stain­less-steel leading edge is then installed. Lists and prices are available on application

PAINT FOR N1 AND N2

Like its predecessor SR.NI, the West-land SR.N2 is coated with a polyamide-cured "Lpikote" resin-based paint. Manufactured by Titanine Ltd from "Epikote" resins supplied by Shell Chemical Company, this paint meets the stringent requirements of the Ministry of Aviation Specification DTD.5555. One coat each of primer, undercoat and finish has been applied to NI and N2.

PITCH-AND-ROLL INDICATION

The Westland SR.N2 and Vickers VA-3 are fitted with gyroscopicully con­trolled pitch-and-roll indicators made by Gyro & Electrical Instruments, Lion Lane, 118b Station Road, Redhill, Surrey. Full technical details of these units are not yet available, as the com­pany is committed in a consultancy capacity. We are informed, however, that it covers all aspects of research and development in this field, and can readily be called upon to afford all facilities.

LETTERS TO THE EDITOR The Editor of "Air-Cushion Vehicles" is not necessarily in agreement with the views express­ed by correspondents in these columns. Names and addresses of writers, not jor publication in detad, must in all cases accom­pany letters.

The Smooth Wake SIR,—In reply to "Perplexed" (Air-Cushion Vehicles, January 24) may I suggest that the smooth wake created by a hovercraft over water is due to two things:—

(1) The bows of the craft "clipping" the tops of the waves as it passes over them an effect similar to that pi oduced by hydroplanes and other flat-bottomed craft which skim the surface.

(2) The total effect of the cushion, the high-pressure curtain and the com­pression of the free stream air which passes beneath the vehicle is to tend to damp out any unstable condition—i.e., wave motion—which may exist on the free surface of the water.

The whole discussion, of course,

turns on the definition of a "smooth wake." I doubt if waves of a sufficiently small size to pass under the vehicle would be discernable in the general kerfuffle following the passage of an ACV. I do not claim to be the tech­nical expert that your correspondent requires, merely an enquiring aero­nautical engineering student. Helensburgh, DAVID W. NORMAN

Dunbartonshire

American Amateur Construction SIR,—I am most impressed with the sample copy of Air-Cushion Vehicles I viewed in the November 22 issue of Flight International. 1 enclose pictures of my machines which you may find of interest. All are of the plenum-chamber type with a 3 h.p. Briggs & Stratton lawn-mower engine. Best all-up weight is 4251b, best forward speed 26 m.p.h., and hull clearance about 14in to 18in. Please feel free to use any of the pictures. [They are reproduced above—Ed.] Washington, USA HERB BARTLETT

INDUSTRY PROPELLERS FROM AMERICA

We are informed by Oklahoma Propel­ler Co, P.O. Box 457, Shawnee, Okla­homa, that they are one of the largest manufacturers of wood propellers in the

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