BOUZOUKI: THEORY AND PRACTICE OF DESIGNING

BOUZOUKI: THEORY AND PRACTICE OF DESIGNToday we offer air fighters rather unusual material. It to modelers “mediocre” are not only good examples of several design developments that can be used to practice aerial combat, but based on them the basic principles of the calculation and creation of new machines. We hope that the theoretical part of the material will be even more useful than pure information: it will help not only in understanding the strengths and weaknesses of existing models, but also in the design of bizovac new types.

Before you start exploring the selected example designs, I would like to say a few words about why these machines have attracted attention. They are United by one feature — bearing front monocromo. The power circuit of the wing somewhat outdated. If we talk about high level, it is completely extruded foam lomikami having dvupolnye wooden spars and paper close-fitting foam. For masters, this is most likely the best solution — enough tech, low weight and, moreover, providing high survivability model, if adopted today, the relative thicknesses of the profiles. But “thick” profiles, proven in championship modern technology and allows you to fully realize all the advantages of foam lobikov, not always suitable for bizovac average, the transition level. The fact that the reference technique involves the use of supernatural and initially aimed at the specialized engines high power. Athlete “mediocre” operates almost in naskolko times weaker engines and, of course, when designing patterns keep that in mind. Play championship of bizovac without correction of their scheme gives good results, except… specific speed and agility factors that determine primarily the success and suitability of the technique in a dogfight.
It seems that the only way to provide satisfactory “competitiveness” with limited engine power — to make a logical step and go back n scheme, justified in a time when energy fighting motors in the fractional horsepower, and not a few “horses”. The scheme will allow monaurally (attracting new knowledge) to create a sufficiently agile model with small wings relative thickness, which is necessary to ensure rapidity. Frame the frames are definitely less viable in battle: to bring the model down enough to compromise the integrity of the sheathing in one or two sections (as a result of the wing is curved and the model becomes incapable of flight, which does not occur in the developed foam forehead). However, this is the only serious deficiency that had to be reconciled — otherwise “outdated” technology to be better! In addition, it is useful to consider another factor — adaptability in the real world. Foam lobiki good when a Modeler has at least a satisfactory osnastka, great source material, much experience in such work. In any other case a champion technology gives results that are immeasurably worse than monochromie! Examples of this can be found a lot, not to mention the warnings of juniors. The losses are not only in aerodynamics (and thus, for rapidity and agility), but also on the mass and strength of the model as a whole.
 
The first game presented is typical for the Western championship of the school of design, carrying the loud name “Mansi Banzai” is mostly created from balsa. Power head for increased strength and impact resistance of glued three layers of wood. Ribs, scarves and items of sakatchewan carved from balsa veneer thickness ZMM (and all front end parts). The power rib is formed by two pine strips section 3×13 mm, between which are glued the block in the area of the motor (balsa), the axis of rocking (OBC and 2 mm), scarves trailing edge, a shim under the insert of the stabilizer (balsa thickness 1.5 mm). The rear edge of the dubbed — from pine slats 3×6 mm (front) and balsa 5×6 mm (rear). The small distance between pine rails power rib allows you to stick them straight on top and bottom of the wooden beams of the motor section 12×13 mm To the profile rib is complemented by a spruce part plate, is completely similar to a typical intermediate ribs. To facilitate the process of covering the wing with film to the right of the motor is still Polonnaruwa Central node increases prikladnoi blocks and veneer from balsa. The model fitted by the thick captive (for comparison we will specify that the thickness of the polyester in known sets of five different colored sheets of 600×1000 mm, in the best case equal to 0.025 mm). Judging by the large shift of the back tubes for the withdrawal of the wires from the wing, the model is designed for high reliability of the stretch cord, regardless of the power mode of the engine and weather conditions. The maximum thickness of the airfoil is about 50 mm (the profile of the classic type, similar to the series NAKA 00..).
 
R and S. 1. Championship
 
R and S. 1. Championship” model of air combat “Maxi Banzai” under the engine working volume of 2.5 cm3.
 
Fig. 2. Championship model of air combat English athletes under the engine capacity 1...1,5 cm3 (the
Fig. 2. Championship model of air combat English athletes under the engine capacity 1…1,5 cm3 (the”school” division of bizovac). The photo shows the installation of a safety.

 
 
R and p. 3. Championship model air combat domestic developments under the engine working volume of 2.5 cm3. The main symptoms -
 
R and S. 3. Championship model air combat domestic developments under the engine working volume of 2.5 cm3. The main symptoms – “odnomernaya” scheme and flexible frame of a wing with a reduced moment of inertia. The figure on the left shows a diagram of the engine mounts on the two points (over the back wall and the cylinder head).
 
 
Fig. 4. Method of calculating power front monocracy strength and bending
 
Fig. 4. Method of calculating power front monocracy strength and Flexural strength.
 
The second model is also of noble birth, a native of England. Designed to participate in the competition in the class “polutorametrovoy” (corresponding to the domestic division of school models) and are designed for serial compression engine is very limited power. Design alnobetula. Power front edge of the permanent Secunia 18×18 mm, rear — mm. 4×18 Typical intermediate rib, the elements of the wingtips, fairings trailing edge — wood, 3 mm thick veneer cut From chetyrehkilometrovoy basal and a pair of glued together blanks for the root rib and the Elevator and adjacent the rear edge. On top of the assembled frame of the Central rib is sheathed top and bottom curved clip polutorametrovoy of plywood that connects the middle area into a single rugged unit. As the first model tank hard top, soldered tin. Rocking the management of the PCB is mounted on plate bracket (plywood 3 mm), the conclusions of the wires shifted back. Engine mount formed by the Assembly of polutorametrovoy veneer inlays, two bars motor of beech cross section of 9×9 mm and balsa “cowl” with a thickness of 9 mm. the Covering model — brand film, the characteristics are roughly equivalent to the domestic Dacron with a thickness of 0.02—0.025 mm. the center section of the frame to enhance can additionally obthayutsya thin kapron TANU. It is useful to pay attention to the angle of the needle guard the needle valve, hold the legs above the crankcase During operation of the engine with front-wheel distribution this simple detail will help keep the nozzle from the First game presented is typical for the Western championship of the school of design, carrying the loud name “Mansi Banzai”— the basics- • Mr. created from balsa. Power head for increased strength and impact resistance of glued three layers of wood. Ribs, scarves and items of wingtips carved from balsa veneer thickness ZMM (and all front end parts). The power rib is formed by two pine strips section 3×13 mm, between which are glued the block in the area of the motor (balsa), the axis of rocking (OBC and 2 mm), scarves trailing edge, a shim under the insert of the stabilizer (balsa thickness 1.5 mm). The rear edge of the dubbed — from pine slats 3×6 mm (front) and balsa 5×6 mm (rear). The small distance between pine rails power rib allows you to stick them straight on top and bottom of the wooden beams of the motor section 12×13 mm To the profile rib is complemented by a spruce part plate, is completely similar to a typical intermediate ribs. To facilitate the process of covering the wing with film to the right of the motor is still Polonnaruwa Central node increases prikladnoi blocks and veneer from balsa. The model fitted by the thick captive (for comparison we will specify that the thickness of the polyester in known sets of five different colored sheets of 600×1000 mm, in the best case equal to 0.025 mm). Judging by the large shift of the back tubes for the withdrawal of the wires from the wing, the model is designed for high reliability of the stretch cord, regardless of the power mode of the engine and weather conditions. The maximum thickness of the airfoil is about 50 mm (the profile of the classic type, similar to the series NAKA 00..).
The second model is also of noble birth, a native of England. Designed to participate in the competition in the class “polutorametrovoy” (corresponding to the domestic division of school models) and are designed for serial compression engine is very limited power. Design alnobetula. Power front edge of the permanent Secunia 18×18 mm, rear — mm. 4×18 Typical intermediate rib, the elements of the wingtips, fairings trailing edge — wood, 3 mm thick veneer cut From chetyrehkilometrovoy basal and a pair of glued together blanks for the root rib and the Elevator and adjacent the rear edge. On top of the assembled frame of the Central rib is sheathed top and bottom curved clip polutorametrovoy of plywood that connects the middle area into a single rugged unit. As the first model tank hard top, soldered tin. Rocking the management of the PCB is mounted on plate bracket (plywood 3 mm), the conclusions of the wires shifted back. Engine mount formed by the Assembly of polutorametrovoy veneer inlays, two bars motor of beech cross section of 9×9 mm and balsa “cowl” with a thickness of 9 mm. the Covering model — brand film, the characteristics are roughly equivalent to the domestic Dacron with a thickness of 0.02—0.025 mm. the center section of the frame to enhance can additionally obthayutsya thin kapron TANU. It is useful to pay attention to the angle of the needle guard the needle valve, hold the legs above the crankcase During operation of the engine with front-wheel distribution this simple detail will help to keep Inler
in all situations. The airfoil of the type “plate” has a thickness of 18 mm.
 
The third model of air combat — domestic developments. Spoeksman on it under the obvious influence of frame “odnoprovodnoi” scheme, promoted by the magazine “modelist-Konstruktor” and not found in other publications for modelers. The main characteristics of this concept — basing on domestic materials, the maximum design simplicity, to take into account such important factors as the moment of inertia of the model relative to the axis of rotation maneuver and the effect of the elastic wing (sorry, in lack of mo^ appreciated by athletes). Power front edge (ellipse section, with a height of 11 mm and a length along the chord 17 mm) to both ends of the wing has polutorakratnogo reduction section. The Central reinforcement of the edges is used in order to give the opportunity to push a relatively heavy engine in the wing. If the tail of bouzouki such an event reduces the moment of inertia of the model at a constant alignment. The result benefits not only the nature of control and maneuverability in General. The cross section of the reinforcement insert 11 x 14 mm. the Material is the same as that of the edges and all other parts of the model,— pine-medium density, but higher quality (grained, without ROE). The trailing edge section 4×14 mm should be made of pine, the horizontal arrangement of annual layers. The intermediate ribs have a cross-section of 4×16 mm ending — 9×11 …12 mm (the last dimension is height). The Central rib is represented by beam cross-section 9×18 mm. Gusset plate is sawn from plywood with a thickness of 2.5…3 mm. the Entire Assembly is carried out by Strait benevolence seams fresh plasticized epoxy resin. Avoid the use of scarce mm plywood even in the area of motor managed by the two pairs of wedge-shaped plates rigidly connecting the Central rib with the force edge. The engine is hung on the most modern system — at the corners, screwed n the rear wall of the housing and the bracket on the cylinder head Such a scheme not only reduces mass of the model, but also reduces the moment of inertia. After profiling of the wing (by the way, as noted, is more useful when lapping the front edge to the cross section closer to the triangle than n times, although ideally it requires proper palealis) and it stitched the captive medium, or the increased thickness of the space under the hinge of the engine are cleaned up, they are the boss of beech wood or thick plywood, and through the whole “sandwich” is sealed with filament winding a steel pipe under the main bolt of the engine. The Elevator is an arbitrary design but with the minimum mass. Here, given the over-chemomentum of inertia it is useful to know that the relief helm on 5 g gives the same result as the removal of 20 with the rear edge! You can also make another conclusion: dramatically easier and stabilizer nodes can be, for example, not to trifle with the cross-section of the trailing edge (excluding the Central nodes of the junction) and of all other parts located near the center line of gravity. The long massive engine KMD-2.5 allowed beam design of the whole control system it loss the moment of inertia is largely kompensiruet increase the effectiveness of all-moving tail. Centering the load on the outer end of the wing is shifted towards the leading edge, which significantly improves the nature of the input and output of the model in forward and reverse maneuvers. The thickness of the wing in the center, 18 mm. it Should be noted that the “odnoprovodnoi” scheme, this frame size does not make much sense, as the overwhelming area of the real thickness profile of the given film and facing Naga a lot less. If desired, instead of one intermediate rib, each console can be set at two, while increasing the profile thickness up to 25…35 mm, and going to the ribs on the plywood thickness 2.5 mm. 3…Also from plywood or pine strips are made and extensions of the Central rib-beam ‘ cross-section which is allowable in this embodiment to reduce up to 9×11 mm. However, similar experiments with pereprofilirovanie should be treated with caution. In some cases, this can give not only a reduction of speed, but maneuverability is directly associated with the flexibility of a framework for the scope and flexibility of a film of plating.
 
In the initial embodiment portenoy the frame of the wing of the type proposed with built-in tank, control system and the load on the end of the wing has a mass of 180 to 200 g. it has to be noted that when the limited power of the engine is not worth chasing… sorgoleone model. Oddly enough, it is. When “decheniana” flight speeds lightweight, for example, to 100 g of models of air combat maneuvering, but absolutely unreliable in the sense of the tension cord and control not only when a sharp gust of wind, but even in some of the series of figures, accompanied by a decrease of speed. Therefore, when the area of the wing about 20 dm2 weight bouzouki в400 g admittedly optimal. The reliability factor of the tension cord is so important that sometimes leads to paradoxical results in a class “polutorachasovom” — there are cases when only for reasons of manageability had to reload very good for aerodynamics and strength of a small car! And therefore the choice of optimum load-bearing area must be treated carefully as possible, taking into account not only the engine power, but all the other factors.
 
To help the designer of new bizovac, we offer a detailed strength analysis of the bearing element, power front monochrome. Factor introduced into the calculation of the bending moment is derived as the average. It is obtained based on processing all available materials on known good machines and takes into account the distribution and concentration of mass along the span. We recommend to use the given calculation across all instances of the use of monochrome, especially when creating a new-fangled flexible frames.
 
V. KIBETS,
CCTBM engineer, group leader

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