Designed by P. J. Beatty of Johannesburg and W. A.T. Johl especially for South African climatic conditions and the strong thermals experienced in that country, the single-seater BJ-3 was based on experience gained with the successful BJ-2. The prototype, which was built by Performance Sailplanes of Activia Park, Germiston, made its first flight in 1965 and a BJ-3 set up an international speed record over a 500km triangular course on 28 December 1967 of 84 mph.
The BJ-3 is of largely all-metal construction except for the fuselage, which is of glassfibre from the nose to the wing spar, the remainder being a semi-monocoque with duralumin skin and stringers. Landing gear consists of a retractable monowheel aft of the centre of gravity, with a brake, and a retractable nosewheel; in its original form the BJ-3 was to have had a nose-skid. The one-piece plastic canopy hinges to open at the rear, jet fighter fashion, and the BJ-3 is fitted with a full instrument flight panel as well as VHP radio and oxygen. The wings have a basically duralumin load-carrying structure with a wide spar, and are covered with polystyrene foam with an outer protective skin of glassfibre which gives a smooth finish. An unusual feature is the very generous flap area, the Fowler flaps covering no less than 80% of the span and increasing the wing area by 30% when lowered to their full 30°; they have a steel tube spar and, like the main wing structure, are covered in polystyrene foam and glassfibre. Four sets of double DFS-type air brakes are fitted above and below each wing, and the ailerons are of foam and glassfibre. Another unusual feature for a sailplane is a tail braking parachute housed in the tail cone. The fin and rudder are of duralumin, whereas the fixed-incidence tailplane is of plywood-covered spruce construction.
A developed version, the BJ-3A appeared in 1968 and this was followed by the BJ-4, two of which were built for the 1970 World Championships, in which the existing BJ-3 wings were married to a new fuselage and tail unit, the T-tail being replaced with a taller fin and rudder and an all-flying tailplane repositioned on the fuselage behind the rudder.
Span: 52 ft 11.75 in
Length: 24 ft 7.25 in
Wing area: 132.4 sq.ft
Aspect ratio: 20 (flaps in)
Aspect ratio: 15.82 (flaps extended)
Max weight: 1,151 lb
Max speed: 177 mph (in smooth air)
Max aero-tow speed: 138 mph
Min sinking speed: 2.2 ft/sec at 46 mph / 40kt
Best glide ratio: 40:1 at 81 mph / 70kt