In order to make the conversation as concrete as possible, let us first consider several real models. Clearly defining what the advantages and disadvantages of these typical cars, you will be able to judge the whole school design apparatus of the class F2D.
Recently, with all the multitude of schemes of the fighting was divided into three types: light seleblitie, heavy telephonophobia and mixed construction, occupies a middle place among the first two in mass and strength (durability). But today seleblitie “out of fashion”, are increasingly rare, and the best model are divided only into two types — telephonophobia and patterned. These are shown in figures 2 and 3. And on the ground — stacked Bespalova game created by “explanation” technology leading Soviet athletes.
It should be noted that the choice of the samples given in the article, was intended not so much to introduce with the “versatility”, but to give an idea of the types of developments and at the same time to inform you about some useful things and interesting decisions of individual units.
Bezbileta fighting utimes designed by I. Sakharov. From the point of view of technology and construction sites features does not, is made by using the materials, tools and adhesives (K-153 and PVA), well-known to modelers-the”soldiers”.
In the suspension of the Elevator as pipe-joints used needles from syringes Ø 2,5X0,25 mm. the Central portion of the fixed hinge wound threads with adhesive to the finished node trailing edge, increasing the reliability of the node.
There is no plywood elements. Cream pine edges and flanges of the spar (the cross section of the latter decreases towards the wing tips to 3X5 mm), other parts of lime. Tube fungi for mounting engine mounts are machined from alloy AMG, have the axis of the threaded hole M3, and the outside Ø 4,5 mm. wiring harness assemblies cord external control the curvature of the wire OVS Ø 1.5 mm, wrapped with thread and glued on both wing tips. This allows the destruction of the left console to shift cords on the right and continue on the same model.
Fig. 1. Model for air combat Bespalova design:
1 — the fungus under engine, 2 — power part of (Linden 8 mm) 3 — shelf side member (pine 3X8 mm), 4 — extra spar (lime 3Х15 mm), 5 — axis rocking, 6 — shelf rib (pine 3X8 mm), 7 — thrust (AMG wire Ø 3,5 mm), 8 — lug (Linden 8 mm), 9 — pylon (polystyrene), 10 — half-loop (tin 0.3 mm), 11 — axle steering (OVS wire Ø 2 mm), 12 — the rear edge of the pine (4X5 mm), 13 — Klondike nodes (Linden 4X14 mm), 14 — rail of the junction edges of the gusset plate and the hinge tube threads with glue, 15 — rocking chair (the PCB 2 mm) 16 — nozzles (Linden) 17 — the front edge (pine).
Rib light weight, thickness of profile in the center of the wing 35 mm at the ends is 30 mm. the Forehead is carved from construction foam ball, tight — Mylar film on glue BF-2. The model is supplied with engine CSTOM AND 2.5 K, its mass without fuel 430.
The model is made with balsa, and the following telephonophobia developed by athletes from Denmark, and both can be considered typical representatives of the two main schools of design of modern fighting.
The balsa set in this unit is combined with a foam wing forehead. The result is a quite resilient machine of relatively small mass. Drawings sufficient for the construction of information, so it is possible to dwell only on individual nodes.
Fig. 2. The model, implemented with the use of balsa:
1 — additional spar (balsa 6X34 mm density 15 g/cm3 ), 2 — the power of the Central plate rib (balsa 6X25 mm density 0.15 g/cm3 ), 3 — power of the gusset plate (plywood 1 mm), 4 — spacer tube, 5 — axis rocking (OVS wire Ø 2 mm), 6 — beam flange (pine 3X6 mm), 7 — adapter (balsa 8 mm) 8 — rack (balsa 6 mm thick), 9 — Shoe (balsa 6 mm) 10 — solitaire (balsa 5 mm), 11 — pull steering (piano wire Ø 1 mm), 12 — trailing edge (balsa 5X18 mm), 13 — the wild boar (nylon), 14 — lining (plywood 0,4 mm) 15 — Elevator (balsa 3 mm mild), 16 — wall of the spar (balsa 3 mm, the layers vertically).
The forehead is cut from a foam density of 0.02 g/cm3 . The wing on the scale has a profile NACA 630010, except for the endings. Interestingly solved the ribs, which saves material, reduces the weight of the model and allows you to make these items are more hard compared to conventional “sheet” (in this embodiment, each produzca ribs cut out of balsa wood with a thickness of 6 mm with the same height of section). The model is fitted by a low temperature (due to the low heat resistance of the foam) with a film thickness of 23 microns, under it laid a large rolled-up loops of the cord. This technique is more psychological. Korda, of course, will not prevent the film from breaking in the collision models in the air, but for sure will stop or destroy the propeller of a model of the opponent, then that still will need time to removal of wound on the shaft of the motor wire. Therefore, the pilot-rival turns out to be constrained by fear of losing points for the best models on the earth after the collision of bizovac.
Fighting with teleparallelism wing has a similar profile, with less chords gives the thickness in the center, about 35 mm to 40 mm from the previous car. The surface of the foam parts upholstered in a paper with a specific weight of 25 g/m2 and then varnished, resistant to the components of the fuel mixture. The advantages of such a scheme should include the unique vitality, although such devices are a few others lose weight. The proposed model is a small weight reduction is achieved by cutting a channel in alongaboni of the console. Forehead to enhance the strength of the monolithic left. Original — using two wire loops — axle is mounted on a rocking pine beams through the Central rib. However, it should be noted: the attachment site on regular plywood “tongue” or U-shaped bracket covering the beam, virtually equal in reliability, but it is much easier to perform.
Fig. 3. Model teleparallelism wing:
1 — under engine strut (Linden 13 mm), 2 — spacer (balsa 13 mm thick), 3 — power scarf (plywood 1 mm), 4 — “rod” rib (pine 3X13 mm), 5 — Polonnaruwa (balsa 6mm easy), 6 — beam flange (pine 3X6 mm), 7 — thrust booster (piano wire Ø 1 mm), 8 — pad tail (plywood 0.4 mm), 9 — Elevator (balsa 3 mm lightweight) 10 — pig lining (plywood 0.4 mm), 11 — half of the stabilizer (balsa 3 mm mild), 12 — rocking chair (spartaner 3 mm), 13 — axis bracket rocking (piano wire Ø 0,8 mm, junction to solder in the details 16), 14 — front auxiliary spar (balsa 6 mm thick), 15 — area (balsa dense, full height under engine parts), 16 — tube axis (copper), 17 — safety rope.
Both models are athletes from Denmark equipped “semi-soft” wiring of Elevator drive: rocking with rudder horns connect the two rods of steel wire Ø 1 mm. Thus, one can save controls that work on compression, where a high probability of buckling of the element (thrust) or the start of resonant oscillations under the influence of shocks and vibrations from the engine.
Last time we learned about the basic types of fighting models. And today will try to understand what is the meaning of the design of such devices, and from this point of view to evaluate the proposed development.
First of all, on how to achieve supermaneuverability. The vast majority of athletes believes that it is necessary only to provide a good profiling of the wing, a small load on the supporting surface and to provide a model of effective plumage, as the goal is met. Yes, with the significance of the above factors, you can accept (if you accept many different amendments! But about this — later). However, against this background it is of paramount importance, another factor of four. Mention of it already found in the literature on modeling, however, was of a very flimsy character, were sketchy and unsubstantiated, and more concrete was considered too far from the practice examples.
What will be discussed? On the moment of inertia about the transverse axis of the model. Occasionally this concept is found in the lexicon of athletes, however, based on the real designs, not the slightest degree of specificity it has not reached. Will try today to tie together theory and practice, especially as some complex mathematical calculations and exotic physical laws are not required for this. Enough knowledge on the level of the fifth grade!
Immediately start with a specific example. Take a very good “bouzoukia” and let her “pumped” to find the value of moment of inertia. Such an operation is private in the process of research in the laboratories of aerodynamics.
Fighting suspended or pins stuck in the ends of the stabilizer, either directly for the Elevator, if his loop hanging easy to turn and have the ability to detach the rod from the rudder control horn. Then the nose of the model slightly hung to the side and released. The oscillation amplitude of the suspended game must be limited to a few millimeters, otherwise the test result will impact the amendment related to the air resistance, the damping of the swing wing. “Pumping” is repeated several times, measuring with a stopwatch the time five or even ten to read vibrations. The results of the measurements Srednyaya, and displays the time of one oscillation.
Remains to accurately measure the distance from the point of suspension to the centre of gravity of the model and weigh it. Based on these data, after substituting in the design formula (it is shown in figure 4) we find the desired value. We note that in contrast to the calculations, similar to the aerodynamic calculations, we operate a precise and accurate values of physical quantities and obtain accurate and reliable values, the “fault” which is impossible.
Fig. 4. The scheme of “pumping” fully equipped model air combat and method of calculating the moment of inertia.
So, after “pumping” a specific game (which, incidentally, was created with the knowledge of new patterns) found the moment of inertia, approximately equal to 3*10-3 kg*m2 . A lot or a little? Let’s see.
Suppose the radius of the maneuver of our model is 1 m at a flight speed of 180 km/h, in progress half-loop. In principle, the conditions of calculation are not critical, the important progress of the calculation, and you can check it on other input data. We have the same with a constant angular acceleration (in other embodiments, the acceleration will be even higher) and time to perform the entire maneuver with order 0,032 it turns out that the angular acceleration is equal to about 6000 rad/s. Knowing the moment of inertia of the machine and acceleration, easy to determine the required torque. In our case it is equal to 18 N*m, or about 1.8 kgf*m.
Fig. 5. The main parameters of the model rotation when performing a half loop.
Now it estimates the magnitude of the moment have. By multiplying the velocity head of air (without slipstream and braking of the flow in the center of the wing for the standard atmospheric conditions for velocity head in the helm area is assumed equal to qR =q∞ =0,06 V2 m/s) at the helm area (m2 ) and the lift coefficient in real conditions and not exceeding 1, find the force on the steering wheel. And since the shoulder of the action of this force to the center of gravity of the machine is already known, we get MBP. location. =0,06*502 *0,01*1*0,3=0,45 kgf*m Have a value four times less than required!!!
Of course, to trust fully in the theoretical calculation of aerodynamics should not be. However, even in the best case considering blowing the helm of a high-speed jet from the propeller the ratio of the moments will change a maximum of two times, and MBP. location. will be only half M req. The only possibility to provide the desired maneuverability of fighting only in the moment of inertia (yet we will not even remember that there are many factors that additionally braking the rotation of the apparatus) is to reduce its inertia!
So we got to the main. It remains to find ways to reduce the moment of inertia. To make it easier to understand this question, let’s see what is the moment of inertia of the proposed model. So: the engine mount and the propeller falls of 0.6 kg*m2 (for individual elements of the desired size is easy to find by the formula I=m*R2 , where m is the mass of an element, kg; R as in other cases, the distance from the center of gravity of the element to the center of gravity of the fully equipped model, m) in the frame of the wing — 0.9 kg*m2 , and the Elevator with a mass of only 10 g is too… 0.9 kg*m2 ! It becomes clear — is important, not the mass of the part, and the combination of weight and shoulder to the center of gravity, the shoulder plays a primary role (compare the values for engine and rudder), and the desired reduction in moment of inertia will be achieved only through dramatic relief remote from the center of gravity of the model elements and reduce leverage for heavy parts. At the same time, we note that we thus only affect the potential game to maneuver with a small radius bend in any way without interfering with other characteristics (stability, verosimilmente, etc.). In all calculations the position of design center of gravity remains the same and is determined only by considerations of the stability angle of attack.
Fig. 6. Design allnoconfig stabilizer 50×250 mm, weight up to 6 grams:
1, 6 — edge (pine section 2,5X2,5 mm), 2 intermediate struts-rib (pine section 1,5X2,5 mm), 3 — spouts for the installation of a plywood control horn (Linden thickness of 1.5 mm), 4 — skin, giving the stabilizer diamond-shaped profile (Dacron with a thickness of 15-20 µm), 5 — tail the Central rib (lip thickness of 1.5 mm), 7 — the spar web (pine section 0,8X2,5mm), 8 — beam flange (pine section 2X2 mm) 9 — ending (pine section 2,5X4 mm). Frame stabilizer going on a flat Board-the stocks on plasticized epoxy resin, beam flange and the Central rib elements are mounted after removal from the pile. The span of the edges between the struts is not more than 40 mm.
Fig. 7. Modified engine mount on the spar part of the modern wing.
There are two area with a wall thickness of 1.5 mm, privertyvaem to the back cover of the crankcase. Through them is the M3 screw. The third point of fixation of the motor — angle bracket, preventively to the cylinder head.
Fig. 8. A variant of the model with a reduced moment of inertia:
1 — the scarf joint at the edges, and ending, 2 — leading edge-spar, 3 — rib, 4 — sub power solitaire, 5 — Elevator, 6 — power polonaruwa-beam, 7 — trailing edge, 8 rocking chair 9 — ending.
From the point of view of the inertia it makes sense to split the models into three “zones” — frame, motor, tail section with the Elevator and separately to deal with each.
Capabilities facilitate of the motor when the usual methods of design not so much. So while we assume that the only way to get the maximum dvijenie engine to the wing if desired to facilitate the nose of the motor with a propeller. The shortening of the nose and shaft and the relief of Coca and bearing washer will only benefit agility.
Of course, work on the engine and its installation on the model should be made only in connection with the facilitation of the tail model. Special attention should be given handlebar height. As it turns out, even the classic balsa rudders are heavy, especially given the need to cover loose wood fabrics and paints. Many features has a modern suspension system of rudders, including a number of heavy metal elements. The only valid option seems to be steering the pig plywood, all other, up to the plastic, losing.
The shell can only say that there are many errors in the design will not do. But note that even at first glance, the advantages zernoproduktovy apparatus, where the mass of “frame” as if smeared along the chord, in contrast to composing, which have a concentration of mass in niewygodny zones at the end and the beginning of the wing.
Now, armed with the knowledge of the moment of inertia of a particular model, you will be able to do to understand the advantages of the proposed schemes rumble. Of course, there are many factors affecting the flight characteristics of models of air combat. However, any methods of modification will be meaningless without regard to the laws of the inertia of rotation. By the way, now even in appearance, you will be able to judge potential data is even. Much moved to the edge of the engine, and even enough alignment front, it means that the model is able to quickly turn around! Some are judged on agility, fighting the size of the Elevator… And nothing. The fact that large wheels are usually too heavy and increase the inertia so that they become harmful. If this interferes with another factor — the issue of security efforts in the management system is generally sufficient to rotate large steering planes at the desired angle! But this is a separate conversation, though no less important than the concept of inertia for rotation. Until then, you can say that now in these ratios control the handlebars on the models of leading sportsmen close to the maximum allowable border.
A. DARA, engineer
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Air combat… the Popularity of this class has been and will remain unchanged. Let some say that today to do battle is not so “prestigious” — the whole world goes to RC vehicles, and they are the future of modeling. However, it is sufficient to recall how the number of participants going in competitions at all grades Svobodnaya! No less important is the class F2D (air combat). His “asset” — the accessibility in technology, entertainment performances, a high degree of sportiness. The first quality allows you to cultivate a class F2D almost everywhere, regardless of the availability of materials. But, unfortunately, this factor often determines the possibility of the existence of one or the other asiacruise.