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MODELING
S3A class rocket models. Tips for a modeler
Directory / Radio control equipment Of all the classes and types of rocket parachute models, the category S3 is the most "ancient". At the dawn of the emergence and development of rocket modeling, one of the criteria for the competition was the duration of the flight. At that time, it was one of the simple and understandable comparative characteristics of flying rocket models. By the way, even today the flight time is a determining factor in the advantage and technical perfection of models of rockets with a parachute. Yes, and watching in flight models with a large beautiful dome is a pleasure. Since the first rocket model competitions, the S3 category has been invariably present in the program of starts. So, the first world champion in 1972 in models for the duration of a flight with a parachute was the Romanian athlete Ion Radu. Of our compatriots, Alexander Mityurev (1983), Igor Shmatov (1990) and Sergey Karpushov (2004) were the winners of the world championship. boys - Dmitry Lyakh (Ukraine) The Russian "rocketeers" won silver - Pavel Krasnov (boys) and bronze - Sergey Karpushov. The category of parachute models of rockets (S3), depending on the MRD, is divided into four classes. The Champion class for both youths and adults is the S3A class. Requirements for a sports "projectile" such stage - one, body diameter - not less than 40 mm, length - more than 500 mm, starting weight - does not exceed 100 g, engine - one (impulse - no more than 2,5 n.s). The parachute must have at least three lines. Competitions for the duration of the flight with a parachute are held in three rounds. The maximum fixed time in the round is 5 minutes. If several participants after three rounds score the maximum amount of points, additional rounds (no more than two) are held between them to determine the winner. Those who are going to build models of S3A class rockets, among other things, need to know when the flights of their sports "shells" cannot be counted a) the rescue system did not work; b) after the launch, the model flew horizontally, c) the engine or any parts of the model separated, the parachute (parachutes) broke. Over its short history of development, the technical requirements for models have changed and improved. So, until 2000, the minimum case diameter was limited to 30 mm, and since 2001 it has increased to 40 mm, length - up to 500 mm. Of course, this added work to rocket model athletes. I had to develop a different manufacturing technology while maintaining minimal weight characteristics. Indeed, with the same engine (2,5 n s), it was necessary to achieve the same flight altitude as with the largest midsection with a diameter of 30 mm.
One of the first developers of models of the S3 category with a case diameter of 40 mm was the honored trainer of Russia V. Tarasov from Chelyabinsk. With such a model, he became the winner of the All-Russian competition for the Cup of S.P. Korolev in the spring of 2001 and four subsequent ones. In addition, the model is universal: it can also be used in the S6A class. It is made using a widely used technology - fiberglass molding. The body is glued together with the tail cone on one mandrel, the larger diameter of which is 40 mm, and the smaller one is 10,1 mm. The thickness of the fiberglass used is 0.03 mm (two layers). After the resin has dried, the body is lightly sanded. Stabilizer feathers are made of 1,5 mm thick balsa veneer and glued end-to-end with epoxy resin to the motor part of the hull. A thread with a diameter of 0,6 mm is attached to one of the feathers for the suspension of the rescue system and the head fairing. The head fairing is also molded from the same fiberglass. It is conical in shape with a cylindrical skirt 12 mm long. The top of the cone is filled with resin from the inside to a depth of 10 mm. This strengthens the fairing and is a kind of load. The connecting sleeve is machined from foam and glued into the fairing skirt. It also contains the thread of the rescue system, which is connected to the suspension thread.
The parachute of the model is cut out of lavsan film 5 microns thick, the number of lines is 16, the diameter of the dome is 850 mm. Before the flight, a foam plastic wad 40 - 45 mm long, and sometimes two, is inserted into the body. This, as it were, strengthens the hull and helps to keep the rescue system in a certain place without disturbing the centering of the model. Weight of model without parachute and engine - 8 g. Engine - V-2-3 "Volcano-jet" of the author's design and manufacture. It should be noted that this model is a rather complex sports "projectile". Whoever wants to build and take part in competitions for the first time, I advise you to start with a simple and affordable model with a parachute. It can be recommended to those who want to specialize in this class of rocket models. The case 456 mm long is made of two layers of paper 0,13 - 0,15 mm thick on a mandrel with a diameter of 40 mm. After drying, a clip under the engine is glued into its tail section. They grind it out of foam on a lathe, make a hole with a diameter of 10 mm inside - for mounting the engine. Stabilizers (there are three of them) are cut according to a template from a 4 mm thick ceiling foam plate. The front and rear edges are slightly rounded, the side surfaces are coated with PVA glue for rigidity - they are reinforced. They are fastened end-to-end to the body, in its tail section. The head fairing is machined from rigid foam (PVC), its total length is 70 mm. From below, a loop is glued into the end part of the landing skirt of the fairing for attaching the suspension thread of the hull and parachute. Guide rings - two. They are glued on a mandrel with a diameter of 5 - 6 mm and attached to the body. A parachute with a diameter of 600 - 800 mm is cut out of mica paper. Slings (there are 12 of them) 900 - 1000 mm long are fastened along the edges of the dome with paper overlays or strips of adhesive tape. Their free ends are brought together in one knot and tied to a loop on the fairing skirt. Paint the model in bright contrasting colors with nitro paint. The flight weight of the model without MRD is 15 - 17 g, the launch is from a single-pin launcher with a diameter of 5 mm. The model described above can serve as the first sports "projectile" for beginner rocket modellers. A modern, more advanced model of the S3A class was developed several years ago by the now famous athlete from Dubna, Igor Ponomarev. Its body is made of ordinary writing paper (for photocopying) with a density of 80 g/m2. The athlete widely introduces his innovation into competitive practice. Admittedly, he has many followers. He used such hulls to build models of the S6 and S9 categories, with which he repeatedly became the champion of Russia in these categories. I believe that the available technology proposed by I. Ponomarev will be useful to many rocket modellers.
The case - from paper, is made of three elements; conical and two cylindrical. The main cylinder 275 mm long is glued on a mandrel with a diameter of 40 mm, the tail cylinder is 59 mm long, on a mandrel with a diameter of 10,2 mm. Between themselves, the cylinders are connected by a cone 125 mm long. Its narrow part, 40 mm long, is made of two layers of paper. Gluing - overlap, belt width - about 4 mm. The finished case is covered on the outside with two layers of nitro-lacquer. Its mass is 6,5 g. Stabilizer feathers (there are three of them) are cut from a 0,9 mm thick balsa plate. The side surfaces are reinforced with paper and varnished. Stabilizers are glued end-to-end to the body of the engine compartment. Along one of them, an MRD retainer 72 mm long, curved from steel wire with a diameter of 0,5 mm, is fixed on epoxy resin. A parachute suspension thread made of Kevlar is also glued to it. The head fairing is stamped from polystyrene (yogurt jars). Parachute canopy with a diameter of 900 mm - made of metallized lavsan, lines - 16 pcs. Speaking of S3A class rocket models, it is impossible not to take into account the main structural element - the parachute. It is he. more precisely, its diameter is decisive, it is from it that the flight time depends on 80 - 90%. But today, the diameter of parachutes for most participants in this class ranges from 900 - 1200 mm. Material - metallized lavsan film with a thickness of 3 - 5 microns. (This is exactly what is used in large astronautics - it is used to paste over the descent objects of spacecraft). The number of lines - from 12 to 16 pieces. For additional rounds, athletes use parachutes with a dome diameter of about 1,5 meters. Another important component of the successful performance of a rocket modeller should be considered the accounting of the weather situation, the ability to navigate in it. And most importantly - accurately choose the very moment of launch. After all, model flights are not always performed in ideal conditions - with complete calm. And the presence of ascending or descending flows significantly affects the duration of the flight. To determine them, athletes often use all kinds of thermal detectors, installing them at the start point on a long pole. But they do not give a XNUMX% guarantee of finding upstreams for the moment of start. Usually the temperature sensor is installed at a low altitude - about 4 - 5 m, but the model takes off at 250 - 280 m. And if there is a "thermal" at the launch site, it may not always be at the height where the parachute of the rocket model opens. Summing up the above, I want to note that the totality of all the constituent elements of these competitions, their knowledge and their correct application by athletes is the key to a successful performance. Author: V.Rozhkov
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