FLIGHT MODEL FOR BEGINNERS

What is educational flying model? We are all accustomed to the fact that it is a machine fit only to acquire the initial skills of piloting. In most cases, the training model is built with virtually no requirements for its flight properties. The main thing – to provide the maximum ease of manufacture. Eventually, when the athlete will be accepted for the design of the following models with which it will compete, will be subject to calculations and aerodynamics, and strength of materials, and materials science. But at first – what to suffer, whether… And see the light polulotosa “snags”.

Yes, no doubt, the first experience even for such models you can buy, and they are built really quickly. But… do we need these models? Judge for yourself. Skills acquired, developed some automaticity in a variety of situations control behavior in a General non-volatile device. And then the athlete moves on to modern machinery, demanding and very strict in management, as a rule, created by the best world samples. Here it turns out that all the experience gained in training are useless. The difference in the behavior of the “school” and sports “projectile” is so great that even if the latter remains intact after the first flight, time and effort on mastering it takes no less than for the construction and training with the first model.

So isn’t it better to spend the time on proper design of training models, bringing its flight properties to the standards of aeromodelling equipment, preserving, of course ease of manufacture?

So, try to create a model. First of all, let’s define the basic requirements to design: the maximum simplicity of construction and Assembly and high remotepoint. Please note – there is no mention of the strength of structure. But many novice modelers that she assign a crucial role… and make a major mistake! Attempts to strengthen individual components and parts will inevitably lead to a weighting unit. It characteristics deteriorate markedly increases minimum flight speed. And, as a consequence of the accident at the inept actions of the pilot. In some cases, the desire to enhance the strength leads to the fact that preteenanal model can not handle even the venerable piloting.

Radio controlled aerobatic model, glider:

1 – forward fuselage: 2 – strut; 3 – a beam of the fuselage; 4 – keel; 5 – rudder; 6 – Elevator; 7 – stabilizer; 8 – the stretching of the tail; 9 – flaps; 10-wing; 11 – “ear”; 12 – Aileron

So, in the ideal, as in large aircraft, the strength of all units and parts should be minimal, i.e. such that the model is not destroyed in flight. Only then the flight characteristics will allow you to pass pilot training quickly and without breakage of apparatus, without turning the control in a hard struggle with a naughty model. Note important law: the strength of the whole model is always determined by the strength of a single element – the weakest one! To enhance the individual nodes are pointless, the design should be durable.

Now the requirements for in-flight properties:

– minimum steady flight speed, providing the time for making the correct decisions necessary in the absence of automatism from an inexperienced “pilot”. It would be good to vary flight speed in the widest limits, then learning later it will be possible to continue until the transition to modern sports equipment;

– high resistance and good handling. Sensitivity control can and ideally should be regulated. In addition to a wide range of speeds, it is desirable to have the possibility of significant changes to the load-bearing properties that turn either model into a good glider-soaring leader or flight microplane;

– increased power of the training model, saving the last exit in the unexpected for the novice pilot’s position near land;

– should be good and performance: study “universal” obliged to fly with it.

Might sound that demands too much, they are too contradictory. It is inconceivable to make such an educational model… But still, let’s try!

Selection of main circuit

In accordance with the first condition of flight properties select the type of the model glider. More precisely, the glider, and with a powerful engine, having the management of “GAZ”, which will provide high power models if its mass is not too large, and simple take-off.

Now, about the mass of the machine. The fact that it is not only closely linked to the minimum satisfactory strength, but with the choice of the main dimensions of the training model. Taking the specific load on bearing surface is 25 g/DM², the appropriate stress is very good paritala, and choosing an engine, we can find the total area of the planes.

The motor should be well run in any (even winter) conditions and to provide simple operation of the entire plant. The most suitable micro – KMD-2.5 in serial compression option to control the speed. With the glider, equipped with this engine, it is possible to train all year round, it is sufficient for a small, even aerobatic models, it has a significant resource and keeps stable mode in a wide speed range.

The mass of the plant in combination with the fuel system should be not more than 200 g. still used by modelers four channel proportional side of the domestic equipment radio “Suprana-83” has a mass of about 650 g, which gives the total weight of the equipment along with rods, fixing points and mounting panels 900 – 950

How many grams to take on the design of the airframe?

Let’s see what happens if you take the preliminary calculation of the seemingly fantastic figure, So weigh 500 g championship Svobodnaya priteli the much smaller, flying with only “pedestrian” speeds. We have the same total area of the bearing surfaces, obtained after determining the total mass of the model turns out to be one and a half times more – about 55 DM².

The choice of parameters of elements

Will try to “stack” design in a very unusual frame mass. Suddenly let out! Let’s start with the wing. It weight makes the most significant part of the total.

Based on the fact that we are not worth the task of creating a record apparatus, and the good soaring conditions we provide low specific load on the bearing surface can not chase the high value of elongation. Its reasonable size will not only benefit the reduction of the weight of the wing, but and, accordingly, will maintain the supercritical Reynolds number for the secondary chords of consoles. You can easily pick up a simple execution profile that is fully satisfactory in its quality even at minimum speeds. As for the strength and stiffness of the wing, determine its weight, then these quantities are nonlinear dependent on the elongation at planes the same profile. Reducing it twice, we with proper design can alleviate the wing four times!

And what about narrowing? Tempting, of course, to draw straight planes – they seem much easier to manufacture because of the identical shapes of all the ribs. But the tapered wing is not much harder straight. But increasing the strength of the root parts of the wide and reducing them the stresses of bending make it possible to further reduce the weight of bearing areas by 15-20 percent compared to straight.

Very technologically advanced, well-proven in thousands of models, undemanding to keeping in shape and quite “thick” is the classic profile of Clark-Y. Its relative thickness is about 12 percent. As shown by comparative polars for multiple profiles, for small Reynolds numbers the Clark-Y is almost in no way inferior to fashion “applerock”, at higher speeds the win for the use of the latter is not significant enough to prevail over the technological properties of the classical implementation. And, as a rule, the advantage in aerodynamics affects profiles E-series only on part of the polars. Before us is the task of design is not fiber to the soaring leader and microplane-universal.

The solution to the aerodynamic wing will complete the introduction of mechanization across the trailing edge, providing the possibility of turning the soaring leader in flight (!) apparatus and task the angle of transverse “V” to increase the sustainability of the model. To the design of planes back when talking about building a training model.

From the point of view of aerodynamics, the fuselage is an element, only connecting the wing with the stabilizer. Assuming that the fuselage of our system a significant effect on these characteristics will not have due to the small cross-section, we will look for only its constructive solution. The same applies to the tail feathers. Here only it is necessary to consider the load transferred from the stabilizer and fin to the fuselage. If we can get rid of the torque, it will be possible to facilitate, for example, to make the keel of the two vertical surfaces of the square symmetrically over the stabilizer installed on the axis of the beam of the fuselage and underneath.

Model description

First briefly about how are calculated the elements of the glider on the strength. Of course, fully explain the methodology on the pages of the magazine is simply unthinkable due to the large volume of material. It is advisable to just mention the conditions adopted in the calculations. Is: the maximum flight speed of 120 km/h (!) and the minimum value of the radius changes the trajectory corresponding to 8 times the overload is equal to 15 m! Conditions are extremely hard, such a characteristic is not for a glider, and for a good aerobatic microplane. But we are designing universal learning model, capable of flying and “acrobat”, and like a soaring leader.

We begin the story with the most important element of the wing. A considerable elongation of providing high quality value and a small rate of descent of the model with the soaring leader, even with a large contraction of consoles has given rise to enormous bending moments in the root sections at high speeds. Under these conditions a good combination of Flexural strength and torsional stiffness could give a solution with a rigid bearing shell. But the bulk of these consoles would have been excessive, and we would not have been able to stay within the allotted boundaries of the mass.

The decision gives the experience of designing light expense of building a traditional model aircraft. The rigid framework of the rules “taught” athletes to create a very lightweight wings sufficient strength and stiffness. Set consoles, similar to what is used on gliders and rezinomotornaya models, and we apply. Two-shelf side member with the wall will allow the wing to withstand the maximum loads under the most drastic evolutions, the torsional stiffness will give a series of diagonal ribs or struts in the root parts of the consoles. Section shelves of the spar variables corresponding to local bending moments in various sections of the supporting planes.

An important question arising upon the drawing of any new model, – on the necessity of introducing a Central contact of the wing. Typically, the solution connector is used with a significant size of the device, it facilitates transport and manufacturing wings. However, the weighting associated with the separation of bearing areas for the most loaded area is very large, not to mention the nodes of the joint and the connecting pins or plates-bagineti. Split down the center of the wing more difficult to assemble and manufacture, not easy to ensure perfect symmetry of the installation of the consoles relative to the fuselage. The docking station reduces the reliability of the model as a whole – a lot of accidents training apparatuses are caused by destruction of the connecting elements of the wing and fuselage, the decoupling is not accurately made of the node, or its deformation, leading to the displacement of the planes.

Wing design:

1 – Central panel; 2 – a beam; 3 – borders of the flap; 4 – filler flap; 5 rear panel edges; 6 – rear flange; 7 – rib; 8 – oblique rib; 9 – spar; 10 – ending flaps; 11 rib joint; 12 – guide pin; 13 – the wing tip; 14 – toe, 15 – panel; 16 – wall front edge; 17 – flange
 

The design of the stabilizer:

1 – ending 2 – ending steering; 3 – the rear edge of the steering wheel; 4 – filler; 5 – edge of the steering wheel; 6 – the rear edge of the stabilizer Assembly; 7 – boss; 8 – solitaire; 9 Central rib; 10 – rib; 11 – semi-rib; 12-spar; 13 – front edge

Model hog:

1 – bracket; 2 – biscuit 3 – termination rod; 4 – retainer; 5 – hinge

The wing strut:

1 – polkas; 2 – deflector; 3 – bandage; 4 – screw M3

So, I decided that the wing training model will be solid. But how to transport “circuits” with a length of about 2.5 m? Need connector. We’ll move it in a less loaded area. Will the detachable “ears”, in this embodiment, the maximum size of the dismantled plane will not exceed polurama. This will facilitate the glider and to make the model universal. Need “pure” soaring leader? Please! Enough to increase the angle of transverse “V” on the detachable elements and to lower the flaps. Speed the glider will give a locking of the flaps in the neutral position, a small rise will transform the former soaring leader in a good “pilotage” – properties of PLANO-convex profile with a raised flap close to the properties of symmetric. But the dismantling of the “ears” will make the model very close in flight characteristics to the microplane. Shortening the wing will reduce the load on the Central part of the spar, therefore, will not be afraid to display the unit on the highest speeds and sharp turns. In this embodiment, the reversible previously only on the ground, the flaps must be translated into control in flight as the ailerons with a small deflection angles. The possibility of correction of the average angle of their installation (as flaps) is maintained only for the ground conditions.

Will continue to work on the construction of the frame of the wing. The case for the trailing edge. The requirements of minimum weight with sufficient strength meets T-shaped “beam” that is collected from the two rails. Such use of us, it also makes it easy to place the hinge the flaps and ailerons.

To improve the aerodynamics of the model requires the profile of the wing as close to theoretical. When soft the skin this can be achieved only by increasing the number of ribs with the mandatory installation of the nasal floor near the ribs, that will weight the glider. The decreasing of the mass of each of them literally fractions of a gram will help within the given takeoff weight of the apparatus.

Ribs are cut from light grades of polystyrene (e.g. ceiling panels of thickness 3-6 mm). The edging will take all the load. Such ribs are well joined with the T-shaped trailing edge, in the area of spout them useful to strengthen the paste over both sides with paper.

It should be noted, adaptability and cross charm set. You will not have to experience the difficulties associated with the manufacture of the ribs for a trapezoidal wing – for all consoles with any narrowing of the technology alone. First of all, cut the templates of the root and end sections of the wing lowering the contour corresponding to the thickness of the “working shell”. With some heated by electric current of a wire from a foam block cut the workpiece. By “scope” it is equal to the total thickness of all ribs and half ribs to one console plus losses for the next sawing into its individual parts. Using the remaining after cutting the foam pieces back profile, the clamps, sheathed billet lime or birch veneer in epoxy resin (the layers of wood – just across the wingspan!). If you want to increase the thickness of the “skin”, use several layers of veneer sheets, thick plate may not follow the contours profepa on the most curved parts of the nose rib.

After complete curing of the resin workpiece is sawn into individual parts thin circular lime or converted industrial wirelesscom. Rib through one shortened, forming a nasal polonaruwa, followed pasting of areas of intersection with the front edge of the paper.

Wing Assembly is carried out by conventional methods. The only requirement is to provide maximum symmetry of the left and right consoles. The stabilizer design is similar to the planes of the wing, some of its elements only in reduced cross-sections.

The drive system of the ailerons and flaps are not shown on drawings – it all depends on the type of the applied equipment and servos. In any case, we should strive to place cars in the volume of the center section. This will help to get rid of unnecessary nodes in the intersection of actuator and the difficulties associated with preregulatory management on accidental discharges of the wing. And the fuselage will be possible to design smaller and lighter. Ideally, in the center section houses all the servos and receiver in the fuselage is mounted a power supply unit and the drive control gas engine. Thus further reduced the weight of the fuselage and reduces the influence of vibrations of the plant on the reliability of onboard equipment.

Plating of bearing surfaces-Mylar film of medium thickness. On top of it privacyrelated long staple (micuenta) paper. The result is durable, resistant to protopam and impact plating of sufficient stiffness and roughness. Steering elements upholstered in thin Kraft paper on the PVA glue and finished the two-component parquet puck.

In the forward part of the fuselage the engine and some components of the apparatus. Note: the shorter this part, the less load will occur at the points of fastening to the wing and the harder it will be. Therefore Prorsum fuselage with minimal removal forward, assuming a small mass tail of the model. The midsection of the fuselage is compressed to the limit, a plywood Board, sealed with a light longitudinal frames and set, almost round the engine, tank and side part of the apparatus.

It remains to decide which will be the tail part of the fuselage. There are many options, the best is… bestuality! Its function takes on a fork-lift beam. It combines such advantages as lightness, extraordinary ease of fabrication and remotepoint. Each shoulder beam is a square tube made up of four pine slats of variable section. In the transverse direction, the tail portion is fixed relative to the wing by a pair of braces from wire rope with a diameter of 0.5 mm, the nodes of intersection of the beam with the fuselage and wing is split with the impact model.

Control linkage to the rudder of the tail – rope, it is easy to hide inside the hollow of the shoulders of the beam. But at first, when the probability of accidents is sufficiently large, it is better to leave the cables outside. This will facilitate the readjustment of the system after repairs. Ending the conversation about governance, we need to warn modelers from trying the drive flap. Their large area causes Peavine even at low speeds of control efforts, often exceeding the capacity servos. Chassis model was not provided.

A. MOSOVSKY, head of airmodelling mug