Ekolot KR 010 Elf
Elf self launch Ultralight sailplane.
Jerzy Krawczyk, in addition to Ekolot’s Junior and Topaz, has several light aircraft, crop sprayer, and sailplane designs to his credit. In creating the self launching Elf sailplane, he employed composite sandwich and carbon structures to achieve the exceptional strength and durability required to pass UK BCAR Section ‘S’ airworthiness certification.
The Elf prototype used the JPX 330 engine which, unfortunately, was withdrawn from production in 2006 after over 20 years in the market. Fortunately, Compact Radial Engines in Canada has produced a very similar unit. This is 20% more powerful than the JPX and also employs a clutch which eliminates folding prop ‘chatter’ on start-up and allows the prop to fold whilst the engine is on idle. This engine has displayed instant re-start capability.
The Elf employs full span flapperons, and airbrakes, and has excellent rudder/stick co-ordination. The NN17-18 aerofoil possesses mild stall characteristics and overall, the handling conveys a strong sense of stability and security to the pilot.
Production aircraft will have the more powerful Compact Radial engine and a 126cms prop with a projected climb rate of 500 ft/min.
Engine off, the Elf with it’s 120 ft/min sink rate is capable of slowing down to exploit the slightest lift and core the smallest thermal. This is where the fun and skill challenge begins and where, if the pilot falls out of lift into sink, he can be confident of a quick engine restart and climb back to the area of lift.
Engine: JPX 330, 24 hp
Prop dia: 116cms , folding
Weight: 145 kg (with BRS)
Gross Weight: 260 kg
Area: 10.8 sq/m
Span: 11.2 m
Fuel Capacity: 15 litres (3 hours + reserve)
Proof Load: +6 / -3
Max Pilot Height: 1.9m (6’3”)
Max Pilot Weight: 100kg (220lbs)
Cruise: 50 mph at 5,100rpm
Max Climb: 400ft/min at 30mph
Best L/D: 26.4:1, 150ft/min at 45mph
Min Sink: 120ft/min at 39 mph
Airbrake: 300ft/min at 45mph (13:1)
Fuel burn: 4.5 litres/hour