Zlin 24 Krajanek

Czechoslovak glider

The year was 1944. The war was still raging, but everyone was preparing for how to arrange their post-war life. Gliders in the Zlín region - today's Gottwald region - were also preparing for the revival of the gliding sport after the end of the war. Word got around and finally they convinced the avowed "engineer" Ladislav Marcol to help them. Comrade Marcol created a construction group from aviation and sailing fans, which included Ladislav Koutný, Ladislav Šváb, Miroslav Langr and Jan Kosek. After a series of consultations about how the glider should look, what it should meet, and most importantly, how it would be the cheapest to manufacture, it was agreed to construct a training glider. The name "Krajánek" was even invented. After this clarification and division of tasks, the group started working on its own construction. All activities were basically carried out at home, so that the occupiers would not find out that post-war production was being prepared. The structural work had to be done without a static calculation, as a structural engineer was not available.

In 1945 came the liberation of our republic by the Soviet Army. In the then Zlín Airlines, he became the director of Eng. Karel Tomáš, our well-known successful aircraft designer. He showed great understanding for the "Krajánek event" and made it possible both to complete the design and to perform the static calculation of the new glider during normal working hours, in other words, he took it over into the company's program. Simultaneously with the completion of the design work, the production of the prototype began. the workers were full of optimism and fandom for the renewed Czechoslovak sports aviation and successfully completed the prototype already in August 1945.

There has been weighing, calculating the center of gravity and other operations that go into each prototype before it takes off for the first time. It was found with satisfaction that the glider corresponds to the idea of the designers in terms of its own weight and the position of the center of gravity. Therefore, flights could begin at the Otrokovice airport. There was no winch or tow plane available, the take-off was carried out with a tow behind the car, via a pulley". Everything went well the first time, and the designers and the pilot Ladislav Šváb experienced an unforgettable feeling when, after being released, the Krajánek sailed majestically through the air. The narrowness that accompanies almost everyone disappeared designers before the first take-off of the new aircraft. Further tests with the help of a tow plane were carried out quickly and successfully. After the vertical tail area was increased, the prototype was registered in Prague-Puzyn, where it flew. Already during the tests, serial production was being prepared at the factory. A total of 301 were produced pieces of this now almost legendary glider.

TECHNICAL DESCRIPTION
The Z-24 Krajánek was a single-seater strut high-plane glider of all-wood construction.
The wing was single spar with ribs and half ribs. The leading part up to the beam was coated with plywood, the hard coating was also at the roots. half of the wing up to the diagonal beam and between the 15th and 16th ribs. The rest of the wing and ailerons were covered with canvas. The wing was equipped with folding brake flaps. In the rectangular central part of the wing, the Sikorski GS-M profile was used, which transitioned from the 15th rib into the self-stabilizing NACA M5 profile. The wing halves were attached to the fuselage with pins and supported by a pair of simple profile struts.

The hexagonal cross-section hull was a lattice structure with a rigid plywood coating 1.2 mm thick. The cockpit was equipped with a removable plywood cover with an organic glass wind shield. The small dashboard was equipped with three basic flight control instruments. The landing gear consisted of an ash ski supported by rubber blocks and a steel spur under the keel. At the nose of the fuselage there was a hanger for the rope for the aerofoil and under the center of gravity a hanger for the winch start. Steering was lever and cable. The brake flaps were operated by tie rods.

Tail surfaces. The horizontal tail surface was two-beam, the stabilizer was covered with plywood on the leading part, the rest with canvas. The elevator had a canvas cover. The keel surface firmly connected to the hull was covered with plywood. The considerably large steering wheel had the lower part covered with plywood and the rest with canvas.

Coloring. Production gliders were mostly painted a rich yellow. The registration marks and the sign on the sign Z-24 KRAJÁNEK were matte black. Gliders from the first series had a gray fuselage, and the cover of the wing, elevator and rudder remained in the natural color of the varnished canvas.

Technical data. Span 12.12 m, length 6.29 m, bearing area 13.5 m2, slenderness 10.9; empty weight 160 kg, take-off weight 250 kg. Gliding rate 1:18, minimum descent rate 0.8 m/s, maximum permissible speed 215 km/h, minimum speed 50 km/h, towing speed 120 km/h.

The Krajánek was designed by a group of sailing enthusiasts led by L. Marcol in 1944. A year later, in August 1945, the first prototype was produced at the then Zlín Aviation Company. Already during his tests, mass production was being prepared in the production plant. A total of 301 examples of this glider were produced.

For the Krajánka model, we will need a piece of balsa board, thickness 3 mm, balsa cuttings thickness 2 mm and plywood thickness 0.8 to 1 mm and bamboo splinter.

TO CONSTRUCTION (the drawing is in actual size, all measurements are in millimeters):
On a drawing board, we redraw the contours of half the wing, fuselage and tail surfaces using carbon paper and cut them out. According to these templates, we redraw the fuselage 1 and wing 2 on a board of medium-hard balsa thickness. 3 and cut them with the tip of a razor blade with an allowance of about 1 to 2 mm around the perimeter. Sand the hull to the exact shape. We glue the opening for the load in the front part on both sides with 3 pieces of plywood thick. 0.8 to 1. After drying, clean the front of the hull with sandpaper and round the edges of the entire hull. Sand the wing around the perimeter to the exact shape; then we grind them into a profile according to the drawing. We cut the vertical 4 and horizontal 5 tail surfaces from balsa sanded to a thickness of 1.5 and round their edges with sandpaper.

We paint all the parts of the model three times with a thin clear nitro lacquer. After each layer of varnish has dried, sand it with fine sandpaper. If you want to have a particularly faithful model, stick all the parts with thin yellow covering paper. We outline the moving surfaces with black ink or thin black nitroenamel. We cut out the registration markings on both sides of the fuselage and on the wing from above and below from paper adhesive tape, the sticky side of which we sprayed with black inner enamel. We will remove them on the model like a normal decal. We can also draw them with ink directly on the model. We draw the inscription ZLÍN 24 KRAJANEK on both sides of the SOP according to the template.

We cut the wing in the middle, grind the contact surfaces to a bevel and glue them to the riser according to the drawing. Glue the glued wing to the fuselage; until the glue dries, we secure them in the correct position with pins. At the end of the fuselage, stick the SOP and just before it the VOP. Between the fuselage and the wing we glue struts в made of balsa thick. 1.5. We bend a landing ski 7 from a bamboo split with a cross-section of 2x1 over the heat source. We glue two black-dyed balsa scraps 8, representing rubber spring elements, to the fuselage, and a ski to them. From the rest of organic glass or celluloid thick. about 1 we cut out the wind label 9.

We import the model with lead shot 10, poured into the space for load in the front of the hull, so that the position of the center of gravity corresponds to the data on the drawing. We slide it when there is no wind, preferably on a gentle grassy slope. Errors in gliding flight are eliminated by adding or removing load, minor deficiencies by bending the tail surfaces. With the Krajánek adjusted for straight flight, it is nice to fly on the slope.

 

Towing lines

F1A, A1 and A3 free glider launches cannot do without a suitable towing line, which should have a number of specific properties: in particular, high strength, low elongation, resistance to twisting and looping, and stable properties when wet.

During competitions, we can see a variety of materials on the start-whistles: nylon strings, various types of cords, linen and cotton twisted strings and strings knitted from synthetic fibers. Especially the latter, which are mainly of foreign origin, are used by most of our leading competitors in the F1A category.

L-23 Blanik

Minimoa glider