Flight, July 1921
THE SPERRY "COMMERCIAL" WING
DESIGNERS appear to be giving considerable attention to improved and new types of aeroplane wings just now, the principal aim in most cases being a wider speed range. From America come some brief particulars
of a new monoplane wing, which has already been tried out with apparently very satisfactory results. This wing has been designed by the Lawrence Sperry Aircraft Corp. of Farmingdale, Long Island, U.S.A., with a view to improving the performance of such machines as Curtiss J.Ns. ("Jennies"), Canucks, Standard Curtiss Js., etc. There are a large number of these machines being used for commercial and sporting purposes all over the United States, and in spite of the fact that their design is over five years old, they appear to serve their purpose remarkably well, and are likely to do so for some time to come. The ease of obtaining spare parts is a further aid to their popularity. The Sperry Co. have, therefore, placed their new monoplane wing on the market specially for use on these machines, so that owners of the latter may obtain better performance without, it is claimed, detracting from the practical features of the machine.
As may be seen from the accompanying illustration of a Curtiss J.N. fitted with the Sperry equipment, the wing is a thick section cantilever structure mounted parasol fashion above the standard fuselage. The attachments consist of eight Streamlined steel struts, four on each side of the fuselage. Of these a pair on each side extend from the lower longerons of the fuselage to the front and rear wing-spars, the others forming an inverted V, from the top longerons to the front wing-spar. Two round steel tubes, acting as drift struts, also connect the bracing points on the front spar with nose of the fuselage, on the lower longerons. The whole bracing system thus forms a rigid structure.
The strength of the Sperry wing has been tested in extensive trial flights, the factor of safety for the wing being given by the manufacturers as 10. No information is available on the internal construction of the wing other than that it is an internally braced wooden structure covered in the usual manner with fabric. It is also said to possess inherent stability.
Owing to the latter feature and to the raised position of the wing above the fuselage, the manufacturers state that a machine fitted with the Sperry wing will not get into a nose dive, if stalled, nor will it get out of control for any length of time. The following figures, prepared by the makers, give the respective performance of five popular types of machines when fitted with the Sperry wing :-
Machine Engine h.p. Speed Range m.p.h. Useful Load lbs.
Curtiss J.N. or Canuck Ox 90 35-75 800
Curtiss J.N. or Canuck Ox 100 35-80 800
Standard J.-I Ox 90 35-75 800
Standard J.-I K-6 150 38-90 900
Standard J.-I Hispano 150 38-90 900
The improvement in performance obtained with the Sperry wing, which is particularly noticeable in the low landing speed (the original J.N. biplane has a landing speed of 45 m.p.h. and the useful load is 500 lbs.), is due to the thick wing section employed, as well as to the great reduction in parasite resistance which is brought about by the cantilever construction. The parasol arrangement of the wings has the further advantage of providing much better visibility from the pilot's cockpit, and greater accessibility for the passenger and pilot. By virtue of the absence of wire bracing, interplane struts, etc., usually associated with biplanes, and requiring constant building-up, a machine fitted with the Sperry wing requires hardly any rigging, and is easily maintained in proper flying trim.