Slingsby T.13 Petrel
This high performance single-seater was one of the first prewar British attempts to produce a sailplane to rival such well-known German types as the Condor, Rhonadler and Minimoa in terms of performance and aerodynamic refinement. It was, in fact, based on the Rhonadler, with a gull wing of very similar plan form and long span ailerons, with a low wing loading suitable for the rather weak British thermals; no air brakes or flaps were fitted.
Of conventional spruce and birch plywood construction, the Petrel had an all-moving tailplane very similar in outline to the Rhonadler's in its initial form, but later production aircraft had a larger, broader chord tailplane and elevators with a step in the rear fuselage underneath the tailplane.
The cockpit canopy was of a type later to become commonplace on many sailplanes, flush-fitting and completely faired into the fuselage line without a step, while the landing gear consisted of a long wooden skid under the fuselage, without a monowheel, and a tail bumper.
The Petrel first flew in prototype form in December 1938 and production aircraft, known as the Petrel 1, were offered to customers for a mere £266 in 1939, but only six were built before the war put a stop to further production. Two of these G-ALNP and GALPP, survived the war, the latter later being sold to Eire as IGA101.
Span: 56 ft 9 in
Length: 23 ft 9.5 in
Wing area: 180 sqft
Aspect ratio: 17.9
Empty weight: 440 lb
Max weight: 637 lb
Max speed: 105 mph
Min sinking speed: 2.1 ft/sec at 50 mph
Best glide ratio: 27:1 at 42 mph