“DRAGONFLY”-WINNER | MODEL CONSTRUCTION

Analysis of the number of participants in youth competitions of aeromodellers in the expense of building a traditional school clearly indicates a much higher availability of gliders compared to rezinomotornaya. This is understandable: because in the end, the last is the same as the gliders, but are equipped by Moto installations, bringing the sharp complexity of not only manufacturing, but, more importantly, adjust Svobodnaya.

The boys from the group have developed and tested a rather unusual rezinomotornaya (transparent wings immediately named “Dragonfly”), which allowed repeatedly to take prize-winning places at city and regional competitions with the results 470-495 points. A few years of operation “Dragonflies” has convinced us and our rivals not only in their simplicity, but also in competitiveness with more complex, including the balsa.

The most challenging elements of flying models are the supporting plane. To simplify the work on the wings was chosen as the so-called “schematic” power scheme. Despite the small stiffness for a twist like the wings are fully justified in the construction of school rezinomotornaya models.

Rezinomotornaya model airplane.

Below shows the cross section of the wing at the pylon beam and the stabilizer Central rib (with stand).

The ribs and wingtips and stabilizer are made of two layers of fake veneer thickness of 1 mm. Workpiece width 8 mm impregnated with water, smeared with PVA glue, put in pairs and privinchivayut to a plywood frame rubber thread. To protect couples from bonding between them lay the ribbons of Mylar film. On the mandrel at one time we can accommodate up to four sets of workpieces.

The manufacture of the ribs (A) and endings (B):

1 — mandrel (8 mm plywood), 2 — procurement (Linden 1 mm), 3 — lining (Dacron), 4 — a rubber band.

Dried parts cut lengthwise into two halves with a jigsaw, then vyskazyvat. The length of the part cut off in accordance with the marks applied on the mandrel. The ends of the ribs are sanded on a sheet of sandpaper for a tight fit to the edge of the wing.

After preparing the strips for the edges begin to build. Edge glued thread with the corners pinned with pins to flat bench with a drawing, secure the top with transparent tape. Ribs put on epoxy glue or PVA. Ending process “on us” and connect with the edges of the lugs of thread with glue, after which these parts are strapped to the free ends of the corners of the center section. Soaking the last of the knots with glue, put lugs under the wooden bars and press them to the frame so that there was no twists and the angle of the transverse V of both ears were the same. Upon completion of the wing under it are mounted two elongated rail for mounting on the pylon, and on the ground perform of the winding grooves to ledges on the lower plane.

Assembly of the stabilizer similar to the wing. The only difference in the sequence here: first, edges connected with the endings and then mounted ribs and the Central part — the stand. The wing and stabilizer covered with Mylar film thickness of not more than 0,015 mm.

Tube of the fuselage is glued on the epoxy resin of two layers of cardboard (other name — presspan) with a thickness of 0.2 mm on a conical mandrel. The technology is simple: a mandrel wrapped with a Mylar tape wrap around a sheet of cardboard, smeared with glue only in the area of the second coil, placed second protective layer of the film and all the tape up with electrical tape PVC. Except for trimming the ends of the finished tube in the final design is not needed. The front and rear ends are closed by bonding dural rings-frames. The mass of the finished part 26 g.

Tail ravine glued in the adapter. Before doing this it is desirable to mount the resin-ready-made keel scored on the flat bench of slats. At the rear edge of the keel is made of propyl, in which is tightly inserted the rudder are made out of aluminium with a thickness of about 0.3 mm. Cording to the keel of the Mylar film.

Motor part:

1 — hub (OVS wire Ø 2 mm, solder seam with a coil of thin copper wire), 2 — washers, tin (solder), 3 — spring (OVS wire Ø 0,5 mm, 10 turns, termoobrabotki), 4 — washer (steel), 5 — boss (D16T), 6 — pin (brass), 7 — lock nut M2 8 — bearing (bronze), 9 — shaft (wire OVS Ø 2 mm) with thread M2 on the rear shank, 10 — blade, 11 — tube fuselage, 12 is the rear rubber motor pin (D16T), 13 — adapter (D16T), 14 — tail boom (pine 8X8 mm by the end of the cross section of 6X6 mm), 15 — rear frame (D16T, gluing in the fuselage), 16 — the front frame (D16T, gluing in the fuselage), 17 — pin (steel, pressed in the frame).

Design the boss of the propeller clear from the picture. It should be noted that we from the bearings refused deliberately. Experimentally proved that this class models the time of promotion of the harness is the same with the boss, equipped with ball bearings and a bronze sleeve bearing. In addition, the rolling bearings in the field requires constant attention and frequent washings.

When triggered, the stop after the promotion of the rubber motor shaft’s free end enters the hole of the wall of the boss. Rule out situations are possible when using the traditional scheme of locking when the blades because of the elasticity of the shaft are knocked back and fall is finally in an unplanned situation (which tended to crash the model).

The inconvenience of charging harness rubber motor eliminates the production of dual harness length, one end of which passes freely through the eyelet of the shaft.

The blades are cut from fake pieces of size mm. 210X50X12 First processed “in plan view”, which is the axial distance of 25 mm from the edges and it is kicking the line cross-sections, bearing the markings of the width of the blade. Then follows the marking of the side surfaces in accordance with the table and the beginning of the profiling of the lower (rear) surface of the blade. You need to consider that almost all “sweep” this surface is concave. Then filing and top. At this stage the mass of one blade is approximately equal to 5.5 g. After drilling the holes in the butt (with a template) the item is placed on the bracket, sealed retaining washers and the surface of the wood varnished. Komel filing so that, resting in the bend of a wire wheel hub, it restrict the opening angle of the blades at 90° relative to the axis of rotation of the screw.

Marking of the workpiece propeller blade.

Markup of procurement of the propeller blade.

Symbols correspond to the table. The parameters of the resulting propeller: step — 600 mm, diameter — 420 mm.

Fixture for drilling the hole in the butt of the propeller blade.

Markup of procurement of the propeller blade.

The rubber motor is running from a domestic rubber section 2X1 mm. Otesyvajutsja 24 g rubber thread, and it’s no stretch is wound on two nails scored at a distance of 940 mm from each other (this is double the length of the motor). The ends of the strands are connected among themselves or with any round. Working with an assistant, which needs taut connecting strands, as is tying the knot thread. (By the way, in our view, wrap the threads of the “ears” is not necessary). The finished harness is caught in two places with thread to prevent tangling of the rubber. Then there is the daubing castor oil, and the motor is put in place in the fuselage.

Now you need to determine the location of the center of gravity of the already completed fuselage with tail surfaces and a propeller to properly place the pylon of the wing. The mutual arrangement should ensure the alignment of the model in 60% of the leading edge of the wing (center section). Arc pylon covering the fuselage, wrapped with thread. During the attaching node is controlled by the parallelism of the wing and stabilizer from the front.

Special attention should be taken to adjusting runs. The work begins with planning debugging with it. Placing a plate under the front or rear edge of the stabilizer to achieve smooth reduction. This is only a preliminary adjustment. Now twist the rubber motor at 50 rpm and gradually let the model parallel to the ground. So, the simulated motor end of the flight and transition planning. The flight should go without reduction, right-hand turn. Repeating the runs, a permutation of the stabilizer and rudder to achieve the circling radius of about 15 meters with no reduction. Then increase the spin up to 100 rpm, again adjusting motor and planning regimes. If the model is fine planned, and the motor is sharply reduced, it is necessary either to increase the radius of the bend or to raise the thrust of the screw due to re-aim it to a lower pitch. When bending the wire wheel hub will turn out that the folded ends of the blade move away from the fuselage, so after all the adjustments, you may have to remove the blade, tape up the holes and re-drill a new one (prior to removal of the blades it is necessary to accurately measure the new installation angle). To do this you will need more than one time, but the reliability of the self-node mounting of the blades is absolutely worth the inconvenience in debugging.

Gradually increasing the twist of the motor, approaching the moment when the model after the start, certainly released against the wind parallel to the ground, will carry the hill, floating in the air in a vertical position and then falling on the tail. Placing the adjusting plate between the fuselage and the propeller hub, slip the screw shaft to the right. The regulation clarifies with fresh rubber motor.

By the way, new rubber motor (or well, “rested”) is recommended prior to installation on the model to work. For this purpose it is three times stretched to the maximum length, then give birth to 100 revolutions and unwind.

The maximum number of turns of the rubber motor — 450, works with the screw 30-35 C, the flight model in terminou weather, not less than 80 C. better results can be achieved by transition to the wing with double-sided sheathing.

Weight data model, g

Wing: 48

The fuselage with the pylon: 36

Tail boom Assembly: 17

Stabilizer: 11

Propeller Assembly: 25

The rubber motor: 25

The basic data model

Wingspan, mm: 1030

Overall length, mm: 1037

Bearing area, DM²: 13,9

wing — 11,1

stabilizer and 2.8

Takeoff weight, g: 162

Mounting angles, degrees,:

the wing is 2.5

stabilizer — 0

Alignment, % SI: 60

The direction of flight:

motor mode — the right turn

planning — the right turn

V. TYUTIN, master of sports, head of the society, Arzamas

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