“BOUZOUKI” IN “DIPLOMAT”

Modern models of air fight as a championship class and “Junior” are in many respects similar in construction and, accordingly, on the concept. They completely satisfy the “fighters” requirements and only differ in the manufacturing technology.

However, despite the perfect scheme, “Junior” subclass sometimes appear unusual decision, the purpose of which, as a rule, are secondary issues. And we offer our “fighters” case: the main goal of our experiments was the creation of ultra-compact models of low mass, designed for engines of limited power. It was assumed that such models will be able to compete in the competitions mid-tier “bouzouki”, equipped with much more powerful (“professional”) engines with comparable maneuverability and speed, however, reduced due to the small mass of medium level of the tension cord. It appears that the experience of working with similar unconventional models and from the individual stages of work results and insights can enrich the theoretical and practical knowledge modelers. In addition, familiarity with the design and technological discoveries and errors generated by creating ultra-compact “bizovac”, will also help in the design models of other classes and types.

First of all, about the tasks that were set in the design of innovative models. As mentioned above, in the first place was required to significantly reduce the weight and wing area that allowed even taking into account the limited capacity of the plant to achieve a high specific speed. It is important to preserve such properties “bizovac”, as their reliability and ease of starting of the engines, and the reliability of their behavior under any atmospheric conditions at any point of the flight hemisphere. The latter requirements are particularly important in the calculation of the operation by pupils not having sufficient experience of piloting cord models.

Good piloting on takeoff “bouzouki” with a limited wingspan is attainable only with maximum compensation of reactive torque from the rotation of the propeller, otherwise, at low forward speed the model vigorously raises the outer wing goes in a circle with the loss of tension cord. To offer readers models this problem is solved by deepening the engine to the wing. The air screw is approaching the front edge of the wing and the flow, screw propeller, immediately SpryAssets wing surface. Thus kompensiruet a large part of the reactive moment. In favor of the improvement of the tension cord as on the rise, and in the mode of driving, there is a difference in scale polycrylic and handlebar stem height, running on models of the scheme “flying wing” functions of the flaps on the outside from the axis of the engine. When the deviation of the rudder there are two side, useful for data compact models effect: decreases the lifting force on the outer wing (“bouzouki” trying to tilt on the outer wing, trying to leave the circle). This also increases the aerodynamic drag of the same wing. As a result, the model may run out of the circle, but in the perpendicular plane. However, the smooth wing shapes both work equally effectively, due to the equality of their areas.

The initial version of the model of air combat (top – General view):

1 – elements endings (plywood with a thickness of 1.5 mm); 2 – piping tips (pine, 2×4 mm cross-section); 3 – the leading edge (pine, cross-section of 5×5 mm); 4 – rib (plywood thickness 1,5 mm); 5 – easy strut (pine, cross-section 3×3 mm); 6 – plate spar (pine section 4×15 mm; by the end of the wing section is uniformly reduced to 4×3 mm); 7 – COC-nut (D16T or brass – depending on alignment); 8 – casing of the Central unit (plywood with a thickness of 1 mm at the top and bottom of the wing); 9 – spacer-stringer (pine, cross-section 3×3 mm); 10 – bracket offset hinge rudder; 11 – Elevator (alder plywood with a thickness of 5 mm with relief, or precast frame from pine strips); 12 – hog steering (suspension point of the tape); 13 – thrust wheel (aluminum knitting needle Ø2. 5 mm); 14 – piping edge (pine, 2×4 mm cross-section); 15 – rocking bracket (plywood thickness of 3 mm); 16 – rocking chair (D16T sheet thickness of 1.5 mm); 17 – bill boss under the springs of the withdrawal cord wires; 18 – through-wires Ø0,8 mm); 19 – the Central rib (plywood with a thickness of 2 mm); 20 – figure block engine mounts (birch, the cross section of 7×10 mm, with taped pins M3); 21 – a wall of the engine compartment (plywood with a thickness of 1 mm); 22 – the extension of the spar (Linden, thickness 4 mm); 23 – engine, refined and lightweight MARZ-2.5 rear wall from the MK-12 V (in vertical position the cylinder head to match the axis of the nozzle with the mid-height of the tank had to lower the engine down to 6.5 mm; the bulk of experiments were conducted with single-vane air propeller is lightweight and is used solely for balancing)

The second version of the model of air combat subclass of 1.5 cm3

The second variant of the model of air combat subclass 1.5 cm³:

1 – ending (plywood thickness 2.5 mm); 2 – filler forehead (foam stamps PHV); 3 – the leading edge (pine, section 2,5×4 mm); 4 – mamoplastia spar (pine, section 2,5×14 mm; to the ends of the wing cross-section is uniformly reduced to 2,5×5 mm); 5 – Kok-nut; 6 – sealed steel stud M2. 5 for fixing the dural area, screwed to the cooling jacket of the cylinder of the engine; 7 – fuel tank non-traditional forms; 8 – terminal brace (pine, section 2,5×2,5 mm); 9 – rib (plywood thickness 2.5 mm); 10 – stand (pine, section 2,5×2,5 mm); 11 – rear flange (pine, cross section of 3×5 mm); 12 – bracket offset linkage steering (OVS wire Ø1,8 mm), the suspension point of the tape; 13 – the Elevator (easy, stacked frame of pine slats with a rounded front edge); 14 – adjustable pylon; 15 – center brace (pine, section 2,5×2,5 mm); 16 – plate for the output thrust from the cavity of the wing (lip thickness: 2 mm); 17 – the Central rib (plywood thickness 2.5 mm); 18 – casing of the Central unit (plywood with a thickness of 1 mm at the top and bottom of the wing); 19 – thrust wheel (aluminum knitting needle 02,5 mm); 20 – an arm of the rocking chair (birch); 21 – rocking chair (D16T thickness of 1.5 mm); 22 – leashes (OVS wire Ø0,4 – 0.5 mm); 23 – flush solitaire node (plywood 1.5 mm thickness); 24 – wire Ø0. 8 mm; 25 – tail gusset plate (plywood with a thickness of 2 mm); 26 – pads (birch or hornbeam); 27 – glued tube bolt M3 fastening angle brackets, screwed to the crankcase of the engine (steel Ø4×0,5 mm); 28 – boss (birch); 29 – engine refined and lightweight MK-17 “Junior” with cut jet and embedded in the posterior wall of the needle adjust the fuel mixture

Failed we must admit the choice of direction of Vicosa the axis of rotation of the Elevator. When working in both directions under conditions of blowing on it there is no aerodynamic moment of force directed in a circle. However, the calculations showed that the magnitude of this force is negligible compared to other factors; so that Vegas were chosen for purely technical reasons (if a different design would be more profitable to put the wheel perpendicular to the direction of flight or even Vicosa in the opposite direction).

Pre-rendering, have shown that under reasonable the value of the specific load on the bearing area is so compact model engine MARZ-2.5 (or other, similar type), that it is no problem is without disassembly in the case of type “diplomat”. Subsequently it is very simplified trips on flights.

Construction of the first version of “bouzouki” poses difficulties for modelers of any level. So on the technology of its production does not make sense. My only comment: to complicate the conditions of the experiment, the engine was boosted to the level of the average quality of the engine type CMD (when operating at high speeds with easy screws) and at the same time greatly facilitated. Alignment was set at the conventional boundaries; the angles of deflection of the small area of the Elevator is increased due to his small shoulder and… sure: a rich piloting experience extreme machines in any case will enable you to handle this technique.

The first flights of fancy “bouzouki” gave surprising results. At a standard length of cord approximately 16 m take-off of such a small and light model held perfectly, regardless of the direction and strength of the throw. The “bouzouki” quickly gained speed, and… in level flight began to happen something strange. I had the impression that someone was systematically pulling over the top, over the bottom cord: the model is constantly “dancing”, and her flight had to correct a significant deviation rudders. In the figures the behavior has stabilized a bit, but after returning to horizontal flight, the effect occurred again. Immediately a thought came: the instability is associated with the rear alignment too. Therefore, to increase the mass of the bow was mounted a single blade prop with a counterweight and at the same time replaced the Elevator. In the same area, he became three times easier, and the gap between the wheel and the rear edge of the wing has doubled. A single blade propeller, among other things, has almost two times smaller moment of inertia, which promised reduction and the possible influence of the gyroscopic moment. As a result of modifications to the alignment have moved forward by almost 10%.

However, the result of improvements was zero: the model flew exactly the same as before. On takeoff and acceleration, and ideally after a set of speed – could not be worse. I must admit, the puzzle to a person familiar with the aerodynamics, that still. For a while, “bouzouki” was postponed as it was necessary first of all to understand the reasons for what is happening. But at this stage it was the biggest problem.

“Enlightenment” came much later… it Appeared, the whole thing is not in the aerodynamics and the control system. The secret was to not parallel the wires, matching the rocking control. In terms of the usual conditions have created a perfect analogy of the rocking with “return sweep”. And this has one hidden feature, which is useful to know all cordovil, as this effect is on all the models, especially heavy and fast.

If you look closely at the kinematics of operation of the rocking of this type, it will become clear – with deviation from neutral in any direction it is a redistribution of the shoulders of the forces of the tension cords. The consequence is different stretch the threads themselves, and the result is uneven elongation. Because even with a slight exaggeration in standard diameters and lengths cord (and even more twisted wires) the absolute value of the total stretch is calculated in centimeters, in the “reverse sweep” rocking occurs, the effect of the throw of the steering wheel in tiltable, is set by the pilot side. And it is manifested even at small deviations from neutral. Therefore, it becomes almost impossible to keep the model in level flight. And most importantly – all this quite apart from the degree of stability of the aircraft!

It is useful to know that the rocking chair with the “direct sweep”, which in its most successful period of his life he has actively used and promoted the famous American proteinic Denis Adamson (he claimed, citing the kinematic scheme of such a system dramatically enhances the handling and improves her character) actually has the opposite effect.

Redistribution shoulders on it is that, on the contrary, when the deviation from neutral forces, which, due to the difference of stretching of the cords return the rocker to the neutral position. Careful analysis driven Adesina of graphs and charts, has proved if not the fallacy, then, at least, incorrect conclusions. In a special experimental model built to test the impact of “sweeps” of rocking, was consistently installed all versions questionable items. Trial flights fully confirmed the theoretical calculations: the “reverse sweep” leads to an absolute instability of the control and flight model from any, even over-front alignment, and the “direct sweep” had a pronounced effect of “blunting” at a critical alignment, not to mention the traditional position of the center of gravity. General conclusion: in all cases, it makes sense to establish direct rocking with the location of the holes for cords and under the Central axis on one line. All measures to improve stability or handling must be carried out exclusively due to the aerodynamics or balance of the model itself, but not at the expense of rocking (or rather, not “sweep”). Attempts to “break” unstable machine introduction of the “direct sweep” rocking also doomed to failure: fatigue management in fact only reduces the effective gear ratio, leaving the model itself is unstable in flight and very sensitive to wind gusts. Again to clarify: “reverse sweep” not only as it increases the gear ratio of the swing, but significantly, to an unacceptable degree, changes the nature of the transfer effort.

The redistribution of existing shoulders rocking control when you sweep rocking or not parallel cord wires (this is the cause of different tension cords and their various elongation)

Redistribution of existing shoulders rocking control when you sweep rocking or not parallel cord wires (this is the cause of different tension cords and their various elongation)

Fuel tank:

1 -tube drainage or boost (copper Ø2×0,5 mm); 2 – tube for filling the tank (copper Ø3×0,7 mm; after refueling to silence); 3 – body of the tank (tinned plate 0.3 mm thick); 4 – supply pipe of the engine (copper Ø3×0,7 mm); 5 – additional attachment point for the feed pipe on the tank wall. When powered by a fuel pressure bleed from the crankcase volume through the nozzle-valve, preferably at the ends of all tubes to napati rings of copper wire Ø0,4 – 0.4 mm, forming a sort of collar fittings

The frame of the second version of the model

When it became clear the reasons for the failure of the first compact “bouzouki”, was created the second “diplomata” model, but calculated under the engine MK-17. For the time required to analyze the kinematics of the control system, there are new ideas that were embodied in the new design, created specifically for the competition.

In addition to the enhanced speed and agility, the second version of “bouzouki” also had to ensure very high reliability take-off without desire care in a circle and to further increase the probability of capture and cut the ribbon model of the opponent. The latter managed to achieve a sharp “skew” the wing, resulting in the best place for the stretch cord is the redistribution of load-bearing space between the left and right polycrylene (relative to the axis passing through the shaft of the propeller). And the cut tape is now carried out not only in case of contact with rotating propeller, but in the case of seizure of the beveled leading edge of the left wing. Tape, leaning over the edge, was moved to the middle “bouzouki” and there were cut the screw or lunging, hitting on the drainage tube or the engine mount. Note that the proposed solution meets the rules prohibiting to have a special device to cut the tape: in our case they are not, and breakage due to contact with the motor mount is quite likely and the usual technique with a certain manner of operating the pilot with Konami after the bend of the strip through the front edge. We only increased the likelihood of such a cut-lead, bringing the attacking width of the gripping zone are almost up to 300 mm (with screw diameter).

In the last performance of “bouzouki” has become even easier and, like the first, is laid in “the diplomat”, however, with the removed engine. Flight tests have yielded good results in all modes and under all atmospheric conditions. Of course, with a reliable working of the “heart” of the model engine.

V. TIKHOMIROV, master of sports, head of airmodelling mug

Recommend to read

SET ON THE LAWN
In the cold season it is nice to remember the hot summer, Blazhenny hours of quiet rest in the shade of the trees in the garden or at the cottage. But remember at the same time and on...
THE MOUNTAIN BREEZE
Not so often at the winter tracks and the hills will meet snegohodnomu homemade equipment for children. This is mainly well-known industrial design of the "Chuk and GEK". On some have...