Niemi Sisu 1A
The prototype, designed and built over a period of six years by Convair engineer Leonard Niemi in his garage workshop and known as the Sisu 1, was a cantilever shoulder-wing type of all-metal construction with a laminar flow wing of NACA 65-series section to provide very low drag over a broad speed range, with forward sweep to delay tip stall. The 'butterfly'-type V-tail has an included angle of 90°. The two-spar wing has an aluminium alloy skin and plate stringers, with glassfibre/foam stiffening in the leading edge and camber-changing flaps. To achieve the smoothness and accuracy necessary for laminar flow, wing contours were filled and sanded, and all control surface hinge lines and joints in the canopy and removable fairings were sealed.
The Sisu 1A was the production version, 10 of which were built by Arlington Aircraft at Arlington, Texas, and later at Greenville, South Carolina, between 1960 and 1965. This version had a lighter wing structure, and featured vented air brakes and large-span slotted flaps. Landing gear consists of a retractable monowheel and a miniature fixed tailwheel; the pilot sits under a flush-fitting two-piece canopy.
Flown for the first time on 20 December 1958, this American high performance single seater was noteworthy in being the first sailplane ever to exceed1,000km in a soaring flight when. flown by Alvin H. Parker, it set up an international straight line distance record of 1,041.52km (647.17 miles) in a flight from Odessa, Texas,.
The Sisu 1 A set three world records for Alvin Parker out of Odessa, Texas : 784 km/ 487.24 miles on 27 August 1963, 1963; free distance 1,041.52 km. /647.17 miles to Kimball, Nebraska, on 31 July 1964; and goal, 930.6 km. / 578.27 miles, 1969. The Sisu 1A N1100Z, the second 1A to be built, that set the world distance record was donated to the Smithsonian Air & Space Museum and another was donated to the National Soaring Museum.
The type has won the US National Soaring Championships three times, in 1962,1965 and 1967, flown by different pilots (John Ryan, 1962; Dean Svec, 1965; and A.J. Smith 1967). A. J. Smith, winner of the 1967 US Championships, further lightened his ship, and flew his Sisu for a time with wing tip extensions to increase the span from the standard 50ft 0in.
Span: 15.24 m / 50 ft 0 in
Length: 21 ft 2.5 in
Wing area: 10.03 sq.m / 108.0 sqft
Aspect ratio: 23.1
Airfoil: NACA 65 (3)-418
Empty Weight: 222 kg / 490 lb
Gross Weight: 347 kg / 765 lb
Payload: 125 kg / 275lb
Wing Load: 34.6 kg/sq.m / 7.1 lb/sq.ft
Max speed: 161 mph (in smooth air)
Min sinking speed: 0.64 m/s / 2.07 ft/sec / 1.24 kt at 55 mph
L/DMax: 37 @ 92 kph / 50 kt / 57 mph
Best glide ratio: 41.4:1 at 62 mph
No. of Seats: 1
No. Built: 11