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MODELING
Flying boat. Tips for a modeler
Directory / Radio control equipment In the literature on aircraft modeling, not much attention is paid to radio-controlled models of seaplanes, although, as practice shows, many enthusiasts prefer them to purely "land-based", considering "waterfowl" more interesting both for manufacturing and for piloting. Many of them also refer to the ease of use of such models compared to those equipped with a wheeled chassis - after all, for "land" it is far from possible to find a large enough area with an asphalt or concrete path for takeoff and landing. While a suitable aquadrome - a pond, lake or river - is not so difficult to find. In addition, experts say that takeoff and landing from the water are much easier. We bring to the attention of readers a radio-controlled model of a flying boat, designed for an engine with a displacement of 2,5 to 4 cm3. It should be borne in mind that you can install a KMD-2,5 type motor on a mini hydroplane assembled using balsa, but a heavier model made from linden and pine will require a more powerful engine. Another obstacle to the creation of models of floatplanes and flying boats has always been the design of takeoff and landing devices that are in contact with water during takeoff and landing. Indeed, creating good gliding bodies of floats or boats is not an easy problem: they have to glide on smooth water, and in light ripples, and in waves, without burrowing into the water, without making jumps and retaining the ability to plan. However, it is not necessary to "reinvent the wheel" at the same time - all these problems have long been successfully solved by ship modellers who create racing models of the F3 or FSR type: the hulls of these gliders are almost ready-made takeoff and landing devices for seaplane models. And one more thing: other "land pilots" claim that seaplane models can only land on water. However, numerous experiments show that both float planes and flying boats land quite safely not only on water, but also on grass, snow, and even asphalt. The aerodynamic scheme of the flying boat model is a high-wing aircraft with a high-mounted engine. The wing has an asymmetric biconvex R-II-14% profile with high load-bearing characteristics, which works well at high angles of attack.
To control the model, two channels are used: one - in roll, to drive the ailerons, and the other - in pitch, to drive the elevator. In principle, it would be possible to use the third channel to drive the aerodynamic rudder, connecting it also with the hydrodynamic one - when the flying boat moves along the hydroaerodrome, this will allow you to effectively control the model. Structurally, the seaplane model consists of a bearing part (it includes a carrier beam, a wing, an engine with a propeller and a fuel tank, as well as a keel and a stabilizer) and a landing gear - a boat.
The supporting beam of the model is a composite structure, which is a foam blank, reinforced in its front part with a pair of balsa cheeks and pasted over with two layers of fiberglass. In its middle part, from below, a rectangular niche is cut out for the steering machine of the radio control system of the model. From below, two cylindrical holes are drilled in the beam and reinforced with plastic bushings - docking pins connecting the carrier beam and the boat are fixed in them. By the way, good bushings are obtained from felt-tip pens or ballpoint pens. I also note that it is best to cut holes in the foam using a home-made drill from a metal tube of a suitable diameter - you only need to cut teeth on one side of it using a triangular file; drilling holes in the foam follows through a jig of 5 mm plywood. The finished beam is sanded, puttied and painted with auto enamel of a suitable color.
The boat of the model also has a composite construction. To begin with, a blank is cut out of the packaging foam in accordance with the theoretical drawing of the case. Further, it is carefully divided into parts so that it is possible to glue amplifiers from 3 mm balsa plates into the hull - frames, transom and redan boards, as well as longitudinal bulkheads at the rear of the boat. In addition to the amplifiers, lime bosses with M3 threaded nuts glued into them should be glued into the hull - they are designed for deck fastening screws. Further, the hull of the boat is pasted over with two layers of fiberglass, and the deck part of the boat is only primed with epoxy. After the resin has cured, the hull is sanded, primed, and longitudinal ribs pre-cut from linden and fitted to the hull are fixed on it, and docking beech pins are installed, with the help of which the boat hull and the supporting beam of the model are connected. At the end, the body is painted with auto enamel.
The deck of the boat is glued out of epoxy resin and three layers of fiberglass directly over the finished hull - you just need to cover it with the so-called "food film" (food products are usually packed in this). The thinnest film will allow not only to protect the hull of the boat during rather "dirty" work on pasting the deck with fiberglass, but will also make it possible to easily separate the pasting from the hull. When forming the deck, it is necessary to make a 5 mm overlap on the sides of the boat, which will increase the tightness of the hull. After the resin has cured, the deck is sanded, primed and painted. To reduce the resistance to the movement of the boat through the water, its surface after painting should be carefully sanded, covered with another layer of enamel and then polished. The joint between the deck and the hull of the boat should be as tight as possible - to ensure this, a bead of self-hardening silicone sealant should be applied along the side line, put on top of it with a "food film", and then the deck should be fixed with screws. After the sealant has cured, the film is removed - and a completely reliable seal will appear between the deck and the hull of the boat. The wing of the model is V-shaped, of a classical design, it is assembled using a two-shelf spar made of pine slats with a section of 4x12 mm with foam filling of the inter-shelf space. Ribs - balsa, cut from plates 3 mm thick (in the absence of balsa, they can be made from lime 2 mm thick or foam plastic 5 mm thick).
As already mentioned, the wing has an angle V \u10d XNUMX ° - to ensure it, each of the spar shelves will have to be glued with epoxy "on a mustache" from two rails in the simplest slipway from a pair of even boards, ensuring that the required angle V is maintained. In the central part of the wing there is a motor mount made of birch bars 10 mm thick; between the shelves of the spar in this part of the wing, a clip-on rail is glued. The streamlined fuel tank is soldered from 0,3 mm thick tinplate. The ailerons are balsa, each of them is suspended from the wing on three loops (they are pieces of nylon tape) sealed in slots in the ailerons and trailing edges of the wing. The aileron drive horns are made of 0,5 mm thick duralumin sheet. They are fastened to the ailerons with the help of brackets made of aluminum wire with a diameter of 1 mm, sealed in the holes of the ailerons. The control rods connecting the horns and the steering machine are made of duralumin knitting needles with a diameter of 2 mm. The wing covering is made of lavsan film, the technology of covering the models with the help of Moment glue and a small electric iron. The horizontal plumage is assembled on epoxy glue from balsa slats 6 mm thick. The profile of the stabilizer is flat, rounded in its front part. The wing skin is made of lavsan film. The elevator is all-balsa, on the stabilizer it is fixed in the same way as the ailerons on the wing - with the help of three loops of nylon tape. The elevator horn is made of a piece of steel wire with a diameter of 2 mm - on one side M2 is cut on it, and on the other, a ring with an inner diameter of 2 mm is bent. The horn is attached to the elevator using two nuts and two washers.
Keel - all-balsa, cut from a plate 6 mm thick. It is fixed on the carrier beam with epoxy glue. When assembling the model, it should be taken into account that the aerodynamic focus (it is located at a distance of about 25 percent of the wing chord from its leading edge) must not only coincide with the center of gravity of the model, but also with the edge of the front step of the boat. This allows the model to steadily go on planing during takeoff and move along the hydroaerodrome without "pecking" and soaring. The control of the position of the center of gravity should be carried out in the process of manufacturing the model, correcting it, if necessary, by lightening or loading certain elements of the model, as well as changing the location of the receiver and batteries. Before flying, make sure that the model is properly sealed. Additionally, it is recommended to protect the receiver and servos from moisture with a rubber glove or a balloon shell - the rods and connecting wires are passed through punctures in the rubber. You should also seal the onboard power switch - the easiest way to do this is with a pharmacy fingertip, pulling it over the outer part of the toggle switch. The receiver and batteries are fixed in the compartments of the boat using a strip of foam rubber. By the way, batteries should not be sealed due to the release of gases and heat. And yet - for the KMD-2,5 engine, a propeller with a diameter of 180 mm is quite suitable. Experienced pilots categorically advise against using wooden propellers on seaplane models - during unsuccessful landings, when the propeller hits the water, it literally grinds into chips. According to admirers of naval aviation, piloting a hydroplane model is a great pleasure for the "pilot" - takeoffs from the water surface and landings on it are especially good. "Land travelers", however, say that being a "pilot" of a flying boat is much more difficult than a classic radio model. However, the opinion of adherents of hydroaviation is more valuable here - they believe that the retraining process is not too complicated, and the skills of taking off and landing on water are acquired in just a few flights. Moreover, the runway of a hydroaerodrome, as a rule, is smooth, wide, and long, and on a pond or lake you can always choose the most favorable direction for takeoff and landing - towards the wind. So, the engine is started and the takeoff direction is chosen. Please note that when taking off, you should orient the model perpendicular to the waves - they are usually located perpendicular to the direction of the wind. When moving through water, do not make sudden movements with the rudders - this can lead to the capsizing of the flying boat. A correctly centered model will easily enter the redan, followed by separation from the water surface, holding and, finally, takeoff! Author: I.Sorokin
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