“SCHEMATICA” CLASS B1

 

Do not rush to condemn such a decision. First try following our arguments, weigh all the “pros” and “cons”. The positive here include extreme ease of manufacture of the fuselage rack, its low weight and sufficient reliability. If we talk about the negative, then, in addition to the insecurity of the harness of the rubber motor from dirt, nothing more substantial to lead will fail… Judgment about external ugliness “schematic” to address the serious impossible to recognize.

 

But the arguments that can tip the scale in favor of the fuselage rails. Will try at least as a first approximation, to determine what is better and what is worse from the standpoint of aerodynamics. Do not think that you can make immediate and unequivocal verdict of the rail. The most important criterion here is the amount of total external so-called wetted surface. Have a tubular fuselage perimeter with a diameter of 28 mm is approximately 88 mm. And the “schematic” design — only 48 mm. Rubber band outside, will add to the value of approximately 25 mm. In total perimeter (and, hence, wetted surface) of the power part of the fuselage in the second case, winning. As for the apparent neurobiochemistry twisted harness rubber, it is necessary to consider that the entire rubber motor hiding in the wind shadow of the boss of the propeller with all the attachment of his folding blades on the angular ends of the hub. By the way, the same can be said about the planning mode, when a propeller blade was folded along the fuselage.

Yes, about the vulnerability of the harness will not argue. But about how scary it is to potential contamination, can be judged by the experience of operation “thoroughbred schematic”. How many breaks resinator on them you had to watch? Indeed, such is practically no. Another thing — the exploitation of models of class B1. Gaps, caused by the accidental touch of a twisted and stretched rubber beam with the front edge of the fuselage tube as much as necessary. In addition, when the “explosive” outburst just rubber motor, as a rule, destroyed itself and the tubular part of the fuselage (assuming that class B1 is designed primarily for students, Kevlar-carbon “tube” into account, not taken). As for the advantages in weight, it is enough to mention that the preform of the hollow profile length 550 mm, glued with epoxy of four pine strips 10×2 mm cross section (this gives the fuselage cross-section 12×12 mm), weighs only 20 GS. We actually use the Assembly from the rails cross-section 10,5×1,5 mm.

 

 

The main geometrical parameters Svobodnaya models with rubber motor class B1.

 

 

 

 

 

 

 

 

 

If you were able to convince you of the necessity of experiments with “schematically” B1 class, I think, would be interesting to understand other innovations that seem overly simple. This applies first and foremost spar of the wing scheme. Classic dvukhpolosnykh spar is replaced with a pine plate — it perfectly fits with foam forehead of the wing. There are more important arguments in its favor. Judge for yourself. When calculating dvuhromovo longitudinal section of the top shelf will inevitably have to increase due to the fact that it works in compression. Namely, in this type of loads of most varieties of wood has strength that is almost two times smaller compared to the tensile strength. In addition, to achieve the necessary rigidity of the wing bending is necessary to enter the wall of the spar, to which, in turn, placed high enough requirements. And this excess labor, and excess weight details. Another thing is the plate longitudinal. Due to the redistribution of loads of layers of wood tensile strength to be considered in the calculations langeronii parts, almost equal to the sum of limits “tensile” and “compression”. That is, even without winning at the elimination of the wall — plate is better! Add the fact that dvukhpolosnykh spar in the manufacture of students will inevitably have inaccuracies of Assembly, nepalee seams and joints will either be peretyagina because of the excess glue and conclusions are undeniable.

constructive difficulties arise when drawing a force diagram of a wing with foam ribs and forehead, edged slats or veneer. I think we managed to find a good solution to this problem. It consists in gluing to the rear plate of the spar two valspeak to increase the reliability of the gluing of the ribs and spar. Of course, support shelves are below the level of the contour of the profile by an amount equal to the thickness of the edging rib sandwich. Besides fullspace very constructive facilitate the binding of headscarves in places of transition Central part of the wing in the “ears”, as well as in the Central section. For your information: the weight of the two pine strips with cross section of 1,5×1,5 mm length 1000 mm is equal to only 2 g.

 

What else to add? Probably worth to remember and about the simplified profiling of the stabilizer. Of course, the final decision about the appropriateness of this approach to the design make you. But it is useful to remember that a profile in the form of a flat plate were successfully used by leading German athletes on horizontal plumage “cool” championship gliders. It is only necessary to consider in the transition from conventional profiling of the stabilizer to a flat that the installation angles of the latter should be approximately 2° more (if is profiled, for example, angle — 2°, then the plate will require zero installation angle).

 

The absence of severe pylon wing stand on this model is easy kompensiruet installation details of any pleasing you form. Profiling of the wing, it seems, will not cause any objections. The location of the keel under the fuselage are chosen from considerations of preservation of extremely lightweight stabilizer for the planting model of high coarse grass. The long nose part of the fuselage obtained from the use of rubber harness small cross-section, designed for long-term promotion scolapasta screw enlarged diameter. There is also a possible arbitrary modification, as to argue on the topic of optimisation parameters-rotor we simply can not risk. In this embodiment, due to the long fuselage and the large value of the distance between the axes of swing of the blades folding they in any case do not go after the engine on the wing. So let’s say the transition to a simple locking system where one of the folding blades rests on the locking pin, after which the spin stops with a clear fixation of the position of the screw. Note that this is one of the rare circuits where the stop screw is associated with the loss of his thrust, and not a decrease in the longitudinal tension harness rubber motor, its torque, or something else that is essentially only inaccurate indirect symptom of the loss of it thrust.

 

The proposed model class B1 is equipped with a rubber motor selected length, providing a slight tension on the harness after his promotion with the rest a few turns. Of course, it is quite possible any known methods of tightening cords, in length considerably exceeding the distance between the points of suspension on their models. Twist the rubber motor is made in the withdrawal of its termination with the rear hook of the fuselage. Thus it is useful to use a simple stop-pin of the rotation shaft of the propeller, which “breaks Sya” when you run the model. By the way, a certain overweight of the shaft and the whole unit front boss associated with our plans further experiments with “schematica-mi” — the original has been promising.

 

V. SHUMEEV,

engineer,

the head of the circle