Design of typical frame:
1 — the hull skin (around the perimeter of the bogus Reiki 2X5 mm, consistently driven toward each other and mounted on the assembled frame on epoxy adhesive), 2 — frame (plywood with a thickness of 1.5 mm), 3 — power stringers (Linden cross section of 4X4 mm, after Assembly of the frame to malcovati), 4 — supporting stringer (lip section 3X3 mm), 5 — keel (plywood 2 mm, starting from SHP. No. 4 and then — the fake rake 10X12 mm — after linking of the propulsion system and deadwood to facilitate), 6 — Midel’veys (Linden 3X6 mm).
Scheme of a two-position engine speed control for power less than 50 watts.
Install a spark quenching element.
Is used to reduce sparking in the brush mechanism (requirements for the suppression of noise does not satisfy).
The advantage of this unit is sufficient for multiple runs with constant speed capacity and low internal resistance. The mass of the power supply does not exceed 210 g, propulsion — 70-80 g. the mass of the boat should be in the range of 150 g. This is the real value for a small simple model, the main thing — do not overdo the thickness of the layer of finish and color. If the boat is more heavy, it will not match the prototype on the lees (the rules stipulate the need for a parallel water line, the water level on the fixed copies sludge through the midsection should not exceed the scale value by more than 10%). In an extreme case it is permissible to increase the displacement of up to 490 g (the model itself — 210 g). In this case, the boat will still remain within the rules for the number of copies rainfall. However, the required speed will be achieved at the limit engine power.
But there are two other methods to achieve speed stability, with some reserve capacity. No, it is not an increase in the number of batteries or switching to batteries. Enough to attach to the plastic motor housing two magnets from small furniture latches, as not only to increase capacity — improve efficiency of the electric motor! To fix the magnets in any way. It is only important to place them. The fact that their objective — to strengthen and stabilize the magnetic field of the stator (in serial engine supplied with steel magnet, which loses much of its properties at a small overload, not restoring them), so the magnetic field of the additional magnets should be with the main field. The position of the extension — perpendicular to the ground slats of power, the orientation of the magnet with the long side along the axis of the shaft. Another way of achieving reserve capacity with simultaneous reduction of the weight of the boat — using AA batteries. The mass of each is about 14 g, on Board a light model of them placed up to 10 pieces. The best option is two zaparoleny unit with 4 batteries in each. However, the capacity of AA batteries is considerably less than the 343, so you have to ensure that they were fresh, and often enough to replace them for stability speed.
The greatest interest of the proposed prototype of the boat is for larger copies. Scale 1:10 will increase the copy length to 720 mm and a displacement of up to 1.45 kg (the upper limit in accordance with the assumptions of the rules — 1,59 kg). Scale speed microcodable will be equal to 50 m : 16 s = 3.1 m/s. it should be noted that the large model and looks much more refined, and the production is somewhat simpler — don’t need “jewelry” skills.
However, there are problems of a different kind. More than three times as large mass scale and increased speed produces a much more severe demands on the propulsion system. If based on the absence of batteries, the only other possibility:
use a round battery No. 373 (R20). The weight of each does not exceed 105 g (depending on version can be 95 g), but the capacity of freshly source — over 3.2 Ah! While these elements have a low internal resistance. Short-circuit current of such a battery comes to values, 18 And! This means that the capacity of the power supply will be mostly spent on overcoming the internal resistance of the circuit and the source, and work of running of the engine. The desired speed is increased the model can be obtained with the installation of eight batteries 373 that when unit weight of about 800 g leave sufficient reserve mass for everything else. What is particularly interesting: the rules allow not only increasing the displacement within a small range, but the same (up to 10% of scale) decline. A light vessel will be easier to get in current mode. However, this way can be recommended only for RC models in their extreme relief. For competition in the class EK is better to use boats with a maximum draft. Given the almost flat bottom of the copy it will be stable enough at the rate only when moving in the transition from displacement to planing mode. Then the stability of the exchange rate will have a beneficial effect keeled the contours of the nose. Power for such a regime to want more, but the problem is not that complex. It is sufficient to set “spark” is already known engines with additional magnets. The power supply of the items No. 373 is designed to work exactly this powerful “machine”.
A few words about the fairly common among novice modelers mistake. It is used as a power source running the engine flat batteries. This option is valid only for slow-moving models! But the transition to battery with small internal resistance is fraught with large possibility to increase the useful capacity or relieved of the power supply.
Combining two engines into one is performed in different ways. The simplest option is the lengthening of a single shaft (it is still necessary for this copy) and landing him behind the main anchor of exactly the same second. Remain, however, two brush unit and added the need of fixing the second magnetic system, but the latter should not present a problem even for beginners.
A more professional approach would require the installation of double modified motor, made on the basis of DI-1-3, or other such motors. With the technique of carrying out of similar works you can explore the articles, published in “M-K” No. 5 of 1979 and 11 in 1980.
It is necessary to dwell on another possible variant copies for scale 1:10. This RC boat for speeches in class F2A (copies of vessels from 700 to 1000 mm). This difficulty will meet more. This suppression of interference from the electric motor, and more stringent limits on mass — I will have to look for a reserve for equipment (light kit “Suponer” with two servo amplifiers and servo steering, with reduced and lightweight receiver housing and powered by AA batteries has a total mass of about 450 g). And you can find it only by facilitating the boats and improving the efficiency of the engine with the appropriate selection of the characteristics of the power supply. More will be added and the problem of adjustment of turns of the screw, at least for a “full course” — the “middle course” for “stop”. But this job is for modelers already acquired some experience in ship modeling.
And while it remains to wish a good erased with a proposed copy in the class EK. Do not forget in the heat of preparation for her first competition, an open boat without a human driver will look at the course at least funny! Spend a few hours at a time to “fill” up and “captain”.
A. DMITROV, design engineer
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