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Green indicates the page you are on The KIM-3 " Stakhanovets " (1936) CTAXAHOBEUA few years ago I became intrigued by the short write up and (the) profile of this little known Russian glider in Martin Simons’ publication "Vintage Sailplanes 1908 - 1945" . This two seat glider from 1936 is believed to be the first high performance sailplane (unless you know otherwise) to employ a forward swept wing, which allowed the rear pilot to sit over the centre of gravity of the glider, meaning that no trim change was necessary for various weights of passenger and gave the added advantage of a clear view forwards and upwards for both occupants, which can be critical in a steeply banked turn in thermals. The early three view had some errors but these were subsequently revised in Martin’s later publication "Sailplanes 1920-1945" which is still in print. So here I have produced with the help of Martin’s work and further searches through Russian books provided and assisted by K. Matthew Victor, as much information as I have been able to put together, including some rare pictures.
The KIM-3 is better known as the two-seater "Stakhanovets", with which the world distance record for multi-place gliders was made by pilots Kartachev and Savtov, soaring 619 km from Moscow to Ouchnia on July 22nd 1936. The Stakhanovets was a two seat performance glider designed by V.I. Emelyanov and was constructed at his glider factory in 1936. In this glider the designer continued the development of the earlier KIM-2 glider, by improving its exterior shape. The most notable feature of this high performance sailplane was the pronounced sweep forward of its wings, which allowed perfect visibility from both cockpits, something that cannot be claimed for any other two-seater of the time. Straight dihedral was used with the wing tip deflected downward to prevent tip and aileron damage on landing and take off. The glider wing was of monospar construction design with a trapezoid planform using a large taper. (and a swept forward wing, with the wing tips being bent downwards as a rubbing block to allow protection from damage of the wing during landing and take off.) The glider fuselage is of semi monocoque construction. The cockpit was was equipped with dual control and enclosed with a celluloid panelled canopy with sliding windows. It was also equipped for night and instrument flights, the lights working from storage batteries, which also powered a radio receiver and loudspeaker. Behind the second pilot there was a luggage compartment for 10 - 15 kg of baggage. The landing skid was a rigid ski box without any springing. The sailplane was stressed for aero towing and flight in rough air. Further details of the construction of this unusual design are lacking, however the specifications and performance figures are as follows:
In November, 1936 a Stakhanovets was exhibited in the Soviet section of the 15th International Aviation Exhibition in Paris (below). Note the different cockpit canopy used compared to that of the picture at the top of this page which appears to be the design type drawn by Martin Simons. The arrangement of this changed cockpit is shown in the other three view on this page.
From Martin Simons "Vintage Sailplanes" The swept forward planform had another advantage. On any tapered wing the tip sections naturally tend to stall earlier than the roots. The practice in Germany was to twist the wings progressively to lower angles of incidence towards the tips, in order to retain control. Unfortunately this feature was a disadvantage at high speeds. The tips would quickly reach zero angle of attack relative to the local airflow and any further increase in airspeed would see them actually beginning to flex downward, throwing more load onto the inner parts of the wing, creating great drag. Sweep forward has the effect of delaying tip stalling and so the Stakhanovets needed no geometric wing twist at all, even though it had a very strongly tapered planform. In theory its glide ratio at high speeds would therefore be very good.
The only disadvantages of such a shape were that it tended to complicate stressing and construction. To avoid the constructional problems as far as possible, on the Stakhanovets all the nose ribs were glued to the spar at right angles. When covered with plywood to form the usual 'D' - nose, they did not create any appreciable drag by being set at an angle to the direction of the flight. Aft of the spar, the ribs for the fabric covered portion of the wing were aligned parallel to the aircraft's centre line, which, because of the sweep, required them to be set at a slight angle to the spar. The wing root fittings also needed extra work. Otherwise Emilyanov's wing was simple in structure and proved extremely efficient. The Stakhanovets must have been difficult to land in small spaces, although spoilers were fitted on the upper surface of the wings, they proved ineffective, pilots reporting that they made hardly any difference when opened. There is little doubt that the Stakhanovets was in terms of gliding performance, better than the German Kranich. It had a larger span, higher aspect ratio and was at least equally clean aerodynamically. It had the additional advantage of a good high speed performance because of the untwisted wing. The Stakhanovets broke and re-broke all the important two-seat records.
Sailplanes 1920 – 1945 by Martin Simons, |
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