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MODELING
Construction of a semi-copy model. Tips for a modeler
Directory / Radio control equipment The construction of a semi-copy model begins with the manufacture of the fuselage (Fig. 1), the contours of its lateral projection should most accurately reflect the resemblance to the copied aircraft. The fuselage design demands maximum strength with minimum weight. The greatest difficulty in its manufacture is to reduce the weight of the tail, which is much longer than the front, therefore it is made truss. The manufacture of the tail farm is complicated by the need for mutual adjustment of parts and their gluing. Its upper and lower shelves are made of pine slats 3-4 mm thick and 8-12 mm wide (along the forward fuselage). It is desirable that the cross section of the rails decrease towards the end. The thickness of the diagonal spacers is 1-2 mm, the width is equal to the width of the shelves in this place. Instead of diagonal braces, the space between the shelves can be completely filled with light foam. The farm ends with a boss. All parts of the fuselage are connected with PVA glue or epoxy resin. The length of the glued joints of the shelves and the bow should be at least 30 mm. Since there is no need to worry about lightening the forward part of the fuselage and its strength, it is made from a monolithic wooden bar. Sometimes the bow is pasted over with a cloth or fiberglass on glue or resin. This reduces the fragility of the pine plate. Particular attention should be paid to the conformity of the contour of the vertical tail - the keel and the rudder (Fig. 2), since they serve as a kind of autograph of the design bureau that created this aircraft. The keel with the rudder is made of a wooden plate 1-2 mm thick. The rudder is tilted to the right by 10-15° to tension the cord in flight and increase the rigidity of the vertical tail. The stabilizer and elevator are also made of a wooden plate 2-3 mm thick. The front edge is rounded, the back edge is reduced to a thickness of 0,5-1mm. All this to reduce drag and weight. The movable elevator is usually installed on only one half of the stabilizer. This is quite enough.
Before gluing the empennage, check the location of the center of gravity of the fuselage with the engine installed and the empennage attached. It should be at the level of the leading edge of the wing. Otherwise, it is necessary to take measures to lighten the farm and tail (Fig. 3). The engine is attached to the model (Fig. 4) with four bolts and nuts. Under both nuts, so that they do not cut into the wood, it is necessary to lay one common metal plate 10x20 in size and 1,2 mm thick. The nuts are fixed with locknuts. On models of aircraft with a nose wheel, the landing gear is fastened with a collar under the same nuts. To move the center of gravity of the fuselage forward, instead of the hexagonal nut securing the propeller, a steel spinner (Fig. 5) with an internal thread along the engine shaft and a transverse hole for the tightening knob is installed. Sometimes the nose of the fuselage on the side opposite the engine is pasted over with thin plywood, which closes the cutout for the crankcase. On the same side, the exhaust pipes of the aircraft engine are drawn or glued (Fig. 6). The cockpit canopy (Fig. 7) is usually made of transparent celluloid or plexiglass. Inside the celluloid lantern, you can insert the image of the pilot's head. The fuselage truss is pasted over with paper after mounting the tail assembly and preliminary balancing of the model assembly with the engine and propeller. Then proceed to the manufacture of the wing. A typical design feature of the semi-copy model wing is a central plywood spar 2-3 mm thick (Fig. 8), which provides a strong connection between the wing and the fuselage and the transfer of forces from the landing gear (on most aircraft they are installed on the wing). The height of the plywood spar is the same as the height of the ribs at their intersection, or somewhat less. Its shape takes into account the transverse V of the wing. The ribs cut into the spar by one third of its height. The cutout at the ribs is usually from below, at the spar - from above.
The ribs (Fig. 9) are cut with a jigsaw from 1 mm thick plywood or lime veneer. Thin linden plates are sawn off on a circular saw and processed to level the surface with sandpaper glued to a wooden flat bar 200-300 mm long and 50-60 mm wide. In addition to a short plywood power spar, a two-shelf spar runs along the entire wing, connecting all the ribs and the wing tip. It consists of two pine slats, which are inserted at the top and bottom of the ribs into the corresponding slots. Make the leading and trailing edges of the wing. The front, usually square, is inserted into the cutouts in the toes of the ribs with glue, the rear, triangular in cross section, has cuts, the tails of the ribs are inserted into them, having previously smeared with glue. Cuts should be made one-third of the edge deep and exactly the thickness of the rib tail. Wing tips (Fig. 10) - made of wooden plates or foam blocks, treated with a knife and sandpaper. First, one half of the wing is glued, and after the glue has completely dried, the second. The assembled wing is mounted on the fuselage (Fig. 11), the power spar is inserted into the corresponding slot in the fuselage and fixed with glue. Shelves of spars and the leading edge are glued on plywood corners. During installation, do not forget about the installation of the root (adjacent to the fuselage) ribs. These parts only serve to fasten the wing cover and can be significantly lightened by internal cutouts. The wing jamming angle must be strictly maintained and be constant throughout the span - distortions are excluded. Transverse V wing - symmetrical with respect to the plane of symmetry of the fuselage. After the wing, the landing gear and tail assembly are mounted (Fig. 12). The stabilizer is superimposed on the fuselage truss or cut into the boss (depending on the design of the aircraft and the model drawing). Triangular reinforcements (side of triangular section 2-3 mm) are placed at the joint of the fuselage and the stabilizer from below and from above for the strength of gluing, which are sanded after the glue dries. The keel and rudder are mounted after the stabilizer. Landing gear (Fig. 13) schematically copy real aircraft. So, on the La-5, Yak-7, Yak-9, the racks are straight, and on the Yak-1, Yak-3, they seem to go around the wheel, on the Il-2, the "leg" of the chassis is two-column. Racks - made of steel wire Ø 2,5-3 mm - are attached to the plywood spar with threads on glue. Several holes are drilled in the spar, through which the rack is, as it were, sewn. At the point where the strut exits the wing plane, a plywood rectangle is glued to the spar and rib, and a skin is attached to it. The wheel is usually made of foam (Fig. 14). The hole in it for the axis is drilled after gluing reinforcing plywood strips 3 mm thick on both sides. To reduce friction, a copper or tin (bent from a strip of tin) tube is inserted into the wheel. Without reinforcing side plates, the wheel of the model, despite the presence of a sleeve, is crushed and begins to touch the rack. The side of the wheel is glued with a circle of drawing paper, which hides the defects in the installation of linings, imitating a wheel disk. Foam rubber wheels are more consistent with the prototype, but require special care - they are "afraid" of fuel from the engine. On a real aircraft, shields are installed on the racks, closing the landing gear hatches. Their characteristic shape for this aircraft should be repeated on the model. The control system (Fig. 15) consists of two flexible rods made of steel wire Ø 0,6-0,7 mm, a three-arm duralumin (S = 1,5 mm) rocking chair, the axis of which rotates in the lugs of a bracket mounted on the fuselage, as well as a wooden rods with two wire Ø 1,5 mm ends, a duralumin rocking chair riveted to the elevator, plywood or wire guides at the end of the left wing for the passage of rods (pos. 6). These guides are located 20 - 30 mm behind the center of gravity of the model. In flight, the fuselage should be directed not tangentially to the flight path, but nose outward of the circle. This is necessary to tension the cord, that is, to ensure reliable control of the elevator. To prevent the model from rolling inside the circle under the weight of the cord or from an accidental gust of wind, the outer right wing is weighted with a load of 20-30 g. with a tank, rocker, thrust and elevator are located on the starboard side, and two holes are drilled in the fuselage for the passage of flexible rods. After mounting all the units of the model, the location of its center of gravity is once again determined. It should be ahead of the first quarter chord of the wing.
Cover model - paper: fuselage - mica or writing, on the front of the wing and near the fuselage - drawing, in other places - mica or writing. For its sticker, it is best to use PVA glue. The paper lining of the model must be coated twice with AN-1 nitro-lacquer (enamelite), which can be replaced with a solution of celluloid in a solvent for nitro-paints or acetone. The second coating is done 3-4 hours after the first has completely dried. It is desirable to paint the model with a spray gun or spray gun with a liquid solution of nitro paint. Practice painting on something else before painting. After all, the appearance of the model depends on the quality of this final operation. Typical military aircraft paint colors are blue on the bottom and various shades of green or camouflage on top. Many aircraft had green and brown patches of camouflage on top. The red stars on the wings, fuselage and vertical tail at the beginning of the Great Patriotic War did not have a white border along the contour. Wheel rims are usually green or gray, "tires" are black. The color of the tires must be restored regularly, as the paint is rubbed off on the ground during takeoff and landing. After painting, final balancing is performed. The center of gravity of the finished model should be no further than the first quarter of the width of the wing. In most cases, it is necessary to load the nose with additional metal spacers for the engine mounting bolts, since with a rear centering (heavier tail), the model does not obey the elevator well and flies unstably. Author: S.Malik
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