Fibrera KK-1 Utu
The Finnish Utu is a Standard Class single-seater that was designed and built over a three year period by a team of engineers of OY Fibera AB, a company specialising in glassfibre manufacture.
The design team was headed by Dipl-lng Ahto Anttila, and the Utu was intended to investigate the structural applications to sailplanes of plastic laminates stabilised with polyurethane foam. The prototype, designated KK-1a, first flew on 14 August 1964, and was followed by four more prototypes, designated KK-1b,c,d and e, each with structural modifications resulting from variations in the constructional techniques used. Tests with these proved the superiority of plastics over conventional wooden construction, and the Utu in due course went into small-scale production, a total of 22 having been built when production ended early in 1970.
The high cantilever wings have single I-spars and no ribs, each wing consisting of a polyester/glassfibre laminate sandwich shell with foam plastic core. The upper-surface hinged ailerons are of glassfibre reinforced plastic shell construction with foam plastic stiffening; there are no spoilers but flaps are fitted. The Utu has a trailing-edge split spoiler/terminal-velocity brake. One surface rotates up like a spoiler and the other splits down like a flap and the resultant air deflection from the upper spoiler drives the wing down in a strong negative lift configuration.
The fuselage is a double shell monocoque with a polyester/glassfibre laminate outer shell and a sandwich-type inner shell of similar construction to the wing. The fin is moulded integrally with the fuselage and has the tailplane mounted on top of it; the tail surfaces are glassfibre-reinforced plastic shells stiffened with foam plastic. There is a nonretractable monowheel with a drum brake, and a tail skid. The one-piece canopy is blended into the forward fuselage shape, and oxygen and radio is installed aft of the pilot's seat.
Wing span: 15m / 49.2ft
Wing area: 11.24sq.m / 121sq.ft
Empty Weight: 200kg / 441lb
Payload: 110kg / 242lb
Gross Weight: 310kg / 683lb
Wing Load: 27.58kg/sq.m / 5.65lb/sq.ft
Water Ballast: 0kg / 0lb
Aspect ratio: 20
Airfoil: NACA 63 (3)-618 root. 63(1)-612 tip
L/DMax: 35 @80 kph / 43kt / 50 mph
MinSink: 0.61 m/s / 2.0 fps / 1.18 kt
No. of Seats: 1
No. Built: 22
Span:49 ft 2.5 in
Length: 21 ft 4 in
Height: 4 ft 0 in
Wing area: 121.6 sqft
Aspect ratio: 20.0
Empty weight: 441 lb
Max weight: 684 lb
Max speed: 155 mph (in smooth air)
Max aero-tow speed: 124 mph
Min sinking speed: 2 ft/sec at 46 mph
Best glide ratio: 35:1 at 50 mph