Schweizer SGS 1-35
The SGS 1-35 was designed by Leslie Schweizer to 15 m racing class rules.The 1-35 is a high performance single seater which first flew in prototype form in April 1973, and completed its FAA certification programme in the spring of 1974. It was offered in two versions in addition to the standard 1-35, the SGS 1-35A Unrestricted 15m Class variant, and the SGS 1-35C, or Club-35, a simplified and cheaper version for club or syndicate ownership.
The 1‑35 has removable wingtip training wheels, a skid under the nose, and an external radio antenna features. In lieu of spoilers or air brakes, the 1‑35 uses a trailing‑edge flap. All models use flaps for performance and approach control with -8 to +32 degrees that can be deflected beyond its normal landing setting to increase sink, with a maximum deflection of 80 degrees.
The structure is all-metal monocoque fuselage and single-spar, multi-stringer stressed skin wing; elevator and rudder fabric covered.
The 1-35A has a retractable monowheel forward of the cg, with a hydraulic brake, a large tailwheel and no nose skid. Interconnected flaps and ailerons are standard, and the flaps can be lowered to 80° for use as air brakes; there is provision for up to 145 kg/ 320 lb of water ballast with an empty weight of 490 pounds. The 1-35A is claimed to have the widest range of wing loadings in the FAI 15m Class, from 5.78 to 8.96lb per sq ft, enabling it to compete effectively in both weak and strong soaring conditions. Later production 1-35As have a more painted nose and improved wing root fairings.
The 1-35C less expensive has a non-retractable unsprung Cleveland monowheel aft of the eg, with a hydraulic brake, and a nose skid plus a tailskid. There is no provision for water ballast, and the maximum wing loading is 6.59lb/sq ft. The C has a 425-pound empty weight. Low profile rivets are used on the 1-35C's rear fuselage, and its best glide ratio is 36:1 compared to 41:1 for the 1-34A. Altogether 96 1-35s of all versions had been built by January 1980. The type has cantilever shoulder wings with aluminium stressed skin and stringers, the ailerons and flaps being of aluminium torque cell construction; air brakes or spoilers are not fitted. The monocoque fuselage is entirely of aluminium, and incorporates an integral fin; the T-tail is likewise of aluminium with a fixed-incidence tailplane and fabric-covered elevator. The pilot sits in a semi-reclining position under a one-piece detachable canopy.
By 1977 72 1‑35s have been built, and they were coming off the line at the rate of one per week.
Part of the price was due to the costs of FAA certification, but most competition pilots modify their ships back into the experimental category anyway.
The first 1-35 serial 001, belongs to the National Soaring Museum.
Wing span: 15m / 49 ft 2 in
Wing area: 9.64sq.m / 103.8sq.ft
Aspect ratio: 23.29
Airfoil: Wortmann FX 67-K-170/150
Length: 19 ft 2 in
Height: 4 ft 5 in
Empty Weight: 181kg / 400lb
Payload: 118kg / 260lb
Gross Weight: 299kg / 660lb
Wing loading: 5.58 lb/sq.ft
Max speed: 121 kt / 139 mph
Rough air speed: 121 kt
Max aero-tow speed: 139 mph
Stall: 28 kt
L/DMax: 39 88 kph / 48 kt / 55 mph
MinSink: 0.61 m/s / 2.0 fps / 1.18 kt @ 40 kt
No. Built: 101