DIY air cushion drawing. DIY hovercraft. Thanks for your attention
Roads are one of the most serious and intractable problems for rural residents, especially during spring floods. All-terrain vehicles on an air cushion are an ideal alternative to any vehicles in such conditions.
What is such a transport?
The ship is not a special means of transportation, the dynamics of which is based on the air flow injected under the bottom, which allows it to move on any surface, both liquid and solid.
The main advantage of such transport is its high speed. In addition, its navigation period is not limited by the conditions environment - you can travel on such all-terrain vehicles both in winter and in summer. Another plus is the ability to overcome obstacles no more than a meter in height.
The disadvantages include a small number of passengers who can be transported by air-cushion vehicles, and a fairly high fuel consumption. This is explained by the increased engine power, aimed at creating an air flow under the bottom. Small particles in the pillow can cause static electricity.
The advantages and disadvantages of all-terrain vehicles
It is quite difficult to say exactly where to start choosing such a ship model, since it all depends on the personal preferences of the future owner and his plans for the purchased transport. Among the huge number of characteristics and parameters, all-terrain vehicles on an air cushion have their advantages and disadvantages, many of which are known either to professionals or manufacturers, but not to ordinary users.
One of the disadvantages of such ships is their frequent stubbornness: at temperatures of -18 degrees, they may refuse to start. The reason for this is condensation in the power plant. In order to increase durability and strength, all-terrain vehicles on an air cushion of economy class have steel inserts in the bottom, which their expensive counterparts do not have. A sufficiently powerful engine may not pull the vehicle up to a rather small bank with a slope of a couple of degrees.
Such nuances are found only during the operation of the all-terrain vehicle. To avoid disappointment in transport, it is advisable to consult with specialists before purchasing it and view all available information.
Varieties of air cushion all-terrain vehicles
- Junior courts. Ideal for active rest or fishing in small bodies of water. In most cases, such all-terrain vehicles are purchased by those who live far enough from civilization and can only get to their place of residence by helicopter. The movement of small vessels is in many ways similar to the latter, however, they are not capable of side sliding at a speed of about 40-50 km / h.
- Large ships. Such transport can be taken already for serious hunting or fishing. The carrying capacity of the all-terrain vehicle is from 500 to 2000 kilograms, the capacity is 6-12 passenger seats. Large vessels almost completely ignore the side wave, which allows them to be used even at sea. It is possible to purchase such all-terrain vehicles on an air cushion in our country - both domestic and foreign vehicles are sold on the markets.
Principle of operation
The operation of the air cushion is quite simple and is largely based on a physics course familiar from school days. The principle of work is to raise the boat above the ground and level the friction force. This process is called “cushioning” and is a time characteristic. For small vessels, it takes about 10-20 seconds, for large vessels it takes about half a minute. Industrial off-road vehicles pump air for several minutes in order to increase the pressure to the desired level. After reaching the required mark, you can start moving.
On small ships, capable of carrying from 2 to 4 passengers, air is pumped into the pillow with the help of banal air intakes from the traction engine. Riding begins almost immediately after the pressure is set, which is not always convenient, since there is no reverse gear in low and middle class ATVs. On larger all-terrain vehicles for 6-12 people, this disadvantage is compensated by a second engine that controls only the air pressure in the cushion.
hovercraft
Today you can meet many folk craftsmen who independently create such a technique. The all-terrain vehicle on an air cushion is assembled on the basis of other transport - for example, the Dnepr motorcycle. A propeller is installed on the engine, which in operating mode blows air under the bottom, covered with a leatherette cuff, resistant to negative temperatures. The same motor carries out the movement of the vessel forward.
A similar all-terrain vehicle on an air cushion with your own hands is created with good technical characteristics - for example, the speed of its movement is about 70 km / h. In fact, such transport is the most profitable for self-production, since it does not require the creation of complex drawings and chassis, while differing in the maximum level of cross-country ability.
All-terrain vehicles on an air cushion "Arctic"
One of the developments of Russian scientists from Omsk is an amphibious cargo platform called "Arctic", which was put into service with the Russian army.
An amphibious domestic vessel has the following advantages:
- Full all-terrain vehicle - transport passes over the surface of any relief
- It can be operated in any weather and any time of the year.
- High carrying capacity and impressive power reserve.
- Safety and reliability provided by design features.
- Compared to other modes of transport, it is economical.
- Environmentally friendly for the environment, which is confirmed by the relevant certificates.
"Arctic" is a hovercraft capable of moving on the surface of both water and land. Its main difference from similar vehicles, which can only be temporarily on the ground, is the ability to operate both in swampy, snowy and icy areas, and in various water bodies.
Hovercraft
This boat is a high-speed vessel capable of moving over the surface of the water and over any flat solid surface: swamp, sand, snow. The idea of \u200b\u200ba hovercraft dates back to the 18th century. But it was only in 1926 that the Russian scientist and inventor Tsiolkovsky developed the principle of movement on an air cushion. And after almost 10 years, engineer V. Levkov designed the first such apparatus. Unfortunately, the project was completely destroyed during the Second World War. The "hovercraft" on the basis of which all modern ships are built was created by the British inventor Cockerell. The first ship, model SR-N1, built in 1959, crossed the English Channel in just 20 minutes. Now boats are used for military purposes, on expeditions to hard-to-reach places, in difficult climatic conditionsas well as an entertainment attraction for tourists.
How the air cushion works
The pillow is formed by the accumulation of compressed air under the bottom of the ship. He lifts the boat over water and land. Thanks to the supplied air, the frictional force is reduced. This allows the unit to move freely over surfaces.
There are several types of air cushion:
- The view in which the air currents, collected by the propeller, freely envelop the bottom around the ship. Strong air currents make the boat hover higher.
- Skeg boats are equipped with narrow hulls - skegs. They save air. Such a vessel can only sail above water.
- Boats with a nozzle view move due to the accumulation of air from special nozzles. The cushion is shielded by water jets from the nozzles.
Also, pillows are divided according to the method of formation:
- The static device is generated by an external fan;
- Dynamic air cushion is a product of the increased pressure in the bottom, which forms when the boat moves over the surface.
Technical capabilities
The technical characteristics of the boat are quite extensive. Such boats are suitable for outdoor activities, and for research expeditions, and for participation in hostilities.
- High speed with low fuel consumption. At a cruising speed of about 60 km / h, the fuel consumption is 20 liters.
- The boat can move on almost any surface: water, sand, swamp, snow, and even on grass and asphalt.
- The average carrying capacity of a passenger boat is 1-1.5 tons.
- Boats can operate at any time of the year and in any weather conditions, even during ice drift.
Landing boat "Kalmar"
With such characteristics, the boat still has limitations of use. Firstly, this vessel cannot overcome solid obstacles over 35 centimeters. For example, a collision with a snag or a log would cost the vessel a drop in bottom pressure or damage to the vessel's flexible rail. Secondly, the boat cannot withstand high waves. This makes it difficult to move and can even sink it. Thirdly, cross-country ability in dense and high thickets can also cause difficulties in movement.
Amphibious boats
Amphibious ships are compact ships, usually propelled by propellers. They are located on top of the case. Thanks to the screw ring nozzles, the noise from their operation is reduced, and the tractive force increases. To make the ship move faster, the amphibian hull is lightweight. It is made of aluminum, and the wheelhouse is fiberglass. The power plant is usually diesel or gasoline and is air-cooled. A light hull with a powerful propulsion system makes the boat fast. The outstanding representatives of amphibious boats are:
- Neptune 3 with Rotax-582UL engine;
- Pegasus 4M - Rotax912 model;
- Khivus-4 with the VAZ-21213 power plant;
- The Cayman is powered by a Subaru engine. Its power is 260 horse power;
- A cheetah with a 3M3-53-11 engine.
Boat "Cheetah"
Development of Russian boats
The development of Russian boats can be roughly divided into several stages. The first stage begins from 1937 to 1940 with the design of boats of the "L" series by engineer Levkov. Unfortunately, the weight of the built and tested ships could not withstand the harsh combat conditions of the 1940-1945 war, and were destroyed.
An important stage in the development of ships is the design idea of \u200b\u200bthe English professor Kokkerel, who in 1955 proposed to inject air using nozzles. In the future, the main designed ships were based on his invention.
The leading shipbuilding bureau "Almaz" became the main place for the development of Soviet air-cushion boats. The first serial boat of the organization, which was created in 1969, was the Skat assault aircraft. Further, it became the basis for modifications of "Murena" and "Omar". In the following years the landing craft "Kalmar" was created.
Landing craft on air cushion "Zubr"
In 1988, the largest high-speed boat in the world "Zubr" was created with a carrying capacity of 150 tons.
All technologies used in the construction of military ships were taken into account in civilian boats. But later, after analyzing all the previous experience in creating floating facilities, the designers came to the conclusion that the project was unprofitable. And it was decided to use more economical diesel engines.
Representatives of civil courts
The boat "Bars" is designed for search and rescue operations and transportation of passengers to hard-to-reach places. It is 6.8 meters long and 3.5 meters wide. The boat can accommodate 6 to 8 people with a driver. It develops a speed of up to 80 km / h. It has one gasoline engine of the M-14V26 model with a capacity of 325 horsepower.
The Gepard hovercraft is a four-seater aluminum craft. Used by rescuers, river police, postal services. The power plant includes a ZMZ-53-11 car engine and two propellers with an annular nozzle, which makes the boat quiet. Develops a speed of up to 60 km / h.
Military court representatives
Landing boats have a military purpose and are designed to land troops, military cargo, weapons in hard-to-reach places. These can be swampy or snowy areas, hidden beaches and coves. Tactical ships can carry out armed strikes and provide fire support to other ships.
Landing boat project 1205 "Skat" - the first serial project of the design bureau "Almaz". The vessel is designed to carry 40 soldiers. The ship is 21.4 meters long, 7.3 meters wide and has a draft of 50 centimeters. The Skat has two gas turbines TVD-10M and one TDV-10. The boat develops a speed of up to 49 knots. The cruising range is 200 miles. The crew of the ship is 4 people. The landing craft is armed with four 30-mm BP-30 "Flame" grenade launchers and two 7.62-mm Kalashnikov machine guns. Also on board is the Kivach-1 radar equipment.
Hovercraft "Zubr"
The Zubr air cushion landing craft is still the largest boat of its kind. It is designed for the release of troops, cargo, as well as for the transport and setting of mines and fire support for other ships. He is able to move on land and swamps, bypass ditches and minefields. The vessel is 57 meters long and 25.6 meters wide. Thanks to five gas turbine engines with a total capacity of 50 thousand horsepower, it reaches a maximum speed of 60 knots.
Armament is:
- Two launchers A-22 "Fire" with unguided rockets
- Two 30-mm AK-630 mounts and an MR-123 fire control system
- Eight sets anti-aircraft missile system "Needle".
The boat hull usually consists of an outer and an inner shell. The outer shell is a 50-degree inclined board without a bottom. They are flat in width and slightly convex at the top. The bow of the boat is rounded. There are open boats and boats with a closed cockpit. Steering and communication equipment is installed inside the cab.
Landing craft have more powerful gas turbine engines different models... For example, the Kalmar has the AL-20K model, and the American LCAC has the Allied-Signal TF-40B. Small passenger boats are equipped with various models of diesel or gasoline engines. These are VAZ-21213, and Subaru, and Rotax and ZMZ-53.
In air cushion boats, propellers are installed on the hull. They are, depending on the size of the vessel: 4, 6 and 9-blades with a fixed pitch. The number of screws varies from 1 to 4.
A padded sheath or "skirt" is flexible enough. These are separate parts, sewn from a dense but lightweight fabric. The canvas is water-repellent and waterproof, does not freeze. Usually rubberized nylon is used.
Anti-noise protection of the vessel is provided by:
- Depreciation of engines
- Availability of elastic couplings
- Exhaust mufflers
- The cabin structure has three layers
- Using soundproofing material between the passenger compartment and the fuel tank compartment.
The body material can be: aluminum and composite. Military air cushion boats are made of durable aluminum alloys. Air cushion passenger boats are made of high-tech and durable composite materials. All fasteners and hardware are made of stainless steel.
Usually small boats are easily repaired by specialists or crew. You can do minor repairs yourself. To do this, you must have a special repair kit on board. Larger ships are repaired by a specially trained team of ship repairmen.
The high speed characteristics and amphibious capabilities of air-cushion vehicles (AHCs), as well as the relative simplicity of their designs, attract the attention of amateur designers. IN last years there were many small WUAs built independently and used for sports, tourism or business trips.
In some countries, for example in the UK, USA and Canada, serial industrial production of small WUAs has been established; ready-made devices or sets of parts for self-assembly are offered.
A typical sports WUA is compact, simple in design, has independent lifting and movement systems, and easily moves both above ground and over water. These are mainly single-seat vehicles with carburetor motorcycle or light automobile air-cooled engines.
Tourist WUAs are more complex in design. Usually they are two- or four-seater, designed for relatively long journeys and, accordingly, have luggage racks, large fuel tanks, devices to protect passengers from bad weather.
For economic purposes, small platforms are used, adapted for the transportation of mainly agricultural goods over rough and swampy terrain.
Main characteristics
Amateur WUAs are characterized by the main dimensions, mass, diameter of the blower and propeller, and the distance from the center of mass of the WUA to the center of its aerodynamic drag.Table 1 compares the most important technical data of the most popular English amateur WUAs. The table allows you to navigate in a wide range of values \u200b\u200bof individual parameters and use them for comparative analysis with your own projects.
The lightest WUAs weigh about 100 kg, the heaviest ones weigh more than 1000 kg. Naturally, the less the device mass, the less engine power is required for its movement, or the higher performance can be achieved with the same power consumption.
Below are the most typical data on the mass of individual units that make up the total mass of an amateur WUA: air-cooled carburetor engine - 20-70 kg; axial supercharger. (pump) - 15 kg, centrifugal pump - 20 kg; propeller - 6-8 kg; motor frame - 5-8 kg; transmission - 5-8 kg; propeller nozzle ring - 3-5 kg; controls - 5-7 kg; body - 50-80 kg; fuel tanks and gas lines - 5-8 kg; seat - 5 kg.
The total carrying capacity is determined by calculation, depending on the number of passengers, a given amount of transported cargo, fuel and oil reserves required to ensure the required cruising range.
In parallel with calculating the mass of the AUA, an accurate calculation of the position of the center of gravity is required, since the driving performance, stability and controllability of the vehicle depend on this. The main condition is that the resultant of the forces maintaining the air cushion passes through the common center of gravity (CG) of the apparatus. It should be borne in mind that all masses that change their value during operation (such as, for example, fuel, passengers, cargo) must be placed close to the CG of the apparatus so as not to cause its movement.
The center of gravity of the apparatus is determined by calculation according to the drawing of the lateral projection of the apparatus, where the centers of gravity of individual units, components of the structure of passengers and cargo are applied (Fig. 1). Knowing the masses G i and coordinates (relative to the coordinate axes) x i and y i of their centers of gravity, it is possible to determine the position of the CG of the entire apparatus by the formulas:
The projected amateur WUA must meet certain operational, design and technological requirements. The basis for creating a project and design of a new type of WUA is, first of all, the initial data and technical conditions that determine the type of apparatus, its purpose, total weight, carrying capacity, dimensions, type of the main power plant, running characteristics and specific features.
Tourist and sports WUAs, as well as other types of amateur WUAs, are required to be easy to manufacture, use readily available materials and assemblies in the design, and complete operational safety.
Speaking of running characteristics, they mean the hovering height of the AUA and the associated obstacle overcoming ability, maximum speed and throttle response, as well as stopping distance, stability, controllability, and cruising range.
In the design of a WUA, the shape of the body plays a fundamental role (Fig. 2), which is a compromise between:
- a) round in plan contours, which are characterized by the best parameters of the air cushion at the time of hovering in place;
- b) drop-shaped contours, which is preferable from the point of view of reducing aerodynamic drag during movement;
- c) sharpened in the nose ("beak-shaped") shape of the body, optimal from the hydrodynamic point of view while moving on the agitated water surface;
- d) a form that is optimal for operational purposes.
Using statistics on existing structures that correspond to the newly created type of WUA, the designer should establish:
- the mass of the apparatus G, kg;
- air cushion area S, m 2;
- length, width and outline of the body in plan;
- engine power of the lifting system N c.p. , kW;
- traction motor power N dv, kW.
- pressure in the air cushion P vp \u003d G: S;
- specific power of the lifting system q c.p. \u003d G: N c.p. ...
- specific power of the traction motor q dv \u003d G: N dv, and also start developing the configuration of the WUA.
Air cushion principle, blowers
Most often, when building amateur WUAs, two schemes for the formation of an air cushion are used: chamber and nozzle.In the chamber scheme, which is most often used in simple designs, the volumetric air flow passing through the air path of the apparatus is equal to the volumetric airflow of the blower
Where:
F is the area of \u200b\u200bthe perimeter of the gap between the support surface and the lower edge of the apparatus body, through which the air comes out from under the apparatus, m 2; it can be defined as the product of the perimeter of the air cushion enclosure P by the gap h e between the enclosure and the supporting surface; usually h 2 \u003d 0.7 ÷ 0.8h, where h is the soaring height of the apparatus, m;
υ is the speed of air outflow from under the apparatus; with sufficient accuracy it can be calculated by the formula:
where P c.p. - pressure in the air cushion, Pa; g - acceleration of gravity, m / s 2; y - air density, kg / m 3.
The power required to create an air cushion in the chamber scheme is determined by the approximate formula:
where P c.p. - pressure behind the supercharger (in the receiver), Pa; η n is the efficiency of the supercharger.
Air cushion pressure and air flow are the main parameters of an air cushion. Their values \u200b\u200bdepend primarily on the dimensions of the apparatus, that is, on the mass and the bearing surface, on the height of soaring, the speed of movement, the method of creating an air cushion and resistance in the air path.
The most economical hovercraft are large-sized WUAs or large bearing surfaces, in which the minimum pressure in the cushion allows a sufficiently large carrying capacity to be obtained. However, the independent construction of a large apparatus is associated with the difficulties of transportation and storage, and is also limited by the financial capabilities of an amateur designer. With a decrease in the size of the WUA, a significant increase in pressure in the air cushion is required and, accordingly, an increase in power consumption.
Negative phenomena, in turn, depend on the pressure in the air cushion and the speed of air flow from under the apparatus: splashing while moving over water and dusting - when moving over a sandy surface or loose snow.
Apparently, a successful design of WUA is in a sense a compromise between the contradictory dependencies described above.
To reduce the power consumption for the passage of air through the air channel from the blower into the cushion cavity, it must have a minimum aerodynamic resistance (Fig. 3). Loss of power, inevitable when air passes through the air duct, are of two kinds: loss of air movement in straight channels of constant cross-section and local losses - during expansion and bending of the channels.
In the air duct of small amateur WUAs, losses due to the movement of air flows along straight channels of constant cross-section are relatively small due to the small length of these channels, as well as the thoroughness of their surface treatment. These losses can be estimated by the formula:
where: λ is the coefficient of pressure loss per channel length, calculated according to the graph shown in Fig. 4, depending on the Reynolds number Re \u003d (υ · d): v, υ - air velocity in the channel, m / s; l - channel length, m; d - channel diameter, m (if the channel has a different circular section, then d is the diameter of the cylindrical channel equivalent in cross-sectional area); v - coefficient of kinematic viscosity of air, m 2 / s.
Local power losses associated with a strong increase or decrease in the cross-section of the channels and significant changes in the direction of the air flow, as well as losses for air intake into the blower, nozzles and rudders constitute the main power consumption of the blower.
Here ζ m is the coefficient of local losses, depending on the Reynolds number, which is determined by the geometric parameters of the source of losses and the speed of air passage (Fig. 5-8).
The blower in the WUA must create a certain air pressure in the air cushion, taking into account the power consumption to overcome the resistance of the channels to the air flow. In some cases, part of the air flow is also used to generate horizontal thrust of the apparatus in order to ensure movement.
The total pressure generated by the blower is the sum of the static and dynamic pressures:
Depending on the type of WUA, the area of \u200b\u200bthe air cushion, the height of the apparatus and the magnitude of losses, the constituent components p sυ and p dυ vary. This determines the type and performance of the blowers.
In the chamber circuit of the air cushion, the static pressure p sυ required to create the lifting force can be equated to the static pressure behind the supercharger, the power of which is determined by the formula given above.
When calculating the required power of the AHU blower with a flexible air cushion enclosure (nozzle scheme), the static pressure behind the blower can be calculated using the approximate formula:
where: R v.p. - pressure in the air cushion under the bottom of the apparatus, kg / m 2; kp - coefficient of pressure drop between the air cushion and the channels (receiver), equal to k p \u003d P p: P vp. (P p - pressure in the air ducts behind the supercharger). The k p value ranges from 1.25 to 1.5.
The volumetric air flow of the blower can be calculated using the formula:
The regulation of the performance (flow rate) of the AHU blowers is carried out most often by changing the rotational speed or (less often) by throttling the air flow in the ducts using the rotary valves located in them.
After the required blower power has been calculated, it is necessary to find an engine for it; most often amateurs use motorcycle engines if they need power up to 22 kW. In this case, 0.7-0.8 of the maximum engine power indicated in the motorcycle passport is taken as the design power. It is necessary to provide for intensive cooling of the engine and thorough cleaning of the air entering through the carburetor. It is also important to obtain a unit with a minimum weight, which is the sum of the engine weight, the transmission between the supercharger and the engine, and the weight of the supercharger itself.
Depending on the type of AUA, engines with a working volume of 50 to 750 cm 3 are used.
In amateur WUAs, both axial and centrifugal blowers are used equally. Axial blowers are intended for small and uncomplicated structures, centrifugal blowers are for WUAs with significant air cushion pressure.
Axial blowers typically have four or more blades (Fig. 9). They are usually made of wood (four-bladed) or metal (multi-blade blowers). If they are made of aluminum alloys, then the rotors can be cast and also welded; you can make them welded from steel sheet. The range of pressure generated by axial four-bladed blowers is 600-800 Pa (about 1000 Pa with a large number of blades); The efficiency of these blowers reaches 90%.
Centrifugal blowers are either welded metal or molded from fiberglass. The blades are made bent from a thin sheet or with a profiled cross-section. Centrifugal blowers create pressures up to 3000 Pa, and their efficiency reaches 83%.
Traction complex selection
Propellers creating horizontal thrust can be divided mainly into three types: air, water and wheeled (Fig. 10).An air propeller is understood as an aircraft-type propeller with or without a nozzle ring, an axial or centrifugal supercharger, as well as an air-jet propeller. In the simplest designs, horizontal thrust can sometimes be created by tilting the WUA and using the resulting horizontal component of the force of the air flow escaping from the air cushion. The air propulsion unit is convenient for amphibious vehicles that do not have contact with the supporting surface.
If we are talking about WUAs moving only above the surface of the water, then you can use a propeller or water jet propeller. Compared to air propulsion, these propulsion devices allow to obtain significantly higher thrust for each kilowatt of power expended.
The approximate value of the thrust developed by various propellers can be estimated from the data shown in Fig. eleven.
When choosing the propeller elements, one should take into account all types of resistance that arise during the movement of the WUA. Aerodynamic drag is calculated by the formula
The water resistance caused by the formation of waves when the WUA moves through the water can be calculated by the formula
Where:
V is the speed of movement of the WUA, m / s; G is the mass of the WUA, kg; L is the length of the air cushion, m; ρ is the density of water, kg s 2 / m 4 (at a temperature sea \u200b\u200bwater + 4 ° С is equal to 104, river - 102);
C x - coefficient of aerodynamic resistance, depending on the shape of the apparatus; is determined by blowing the WUA models in wind tunnels. Approximately, you can take C x \u003d 0.3 ÷ 0.5;
S - cross-sectional area of \u200b\u200bthe WUA - its projection onto a plane perpendicular to the direction of movement, m 2;
E is the wave drag coefficient depending on the WUA speed (Froude number Fr \u003d V: √ g · L) and the ratio of the dimensions of the air cushion L: B (Fig. 12).
As an example, in table. 2 shows the calculation of resistance depending on the speed of movement for an apparatus with a length of L \u003d 2.83 m and B \u003d 1.41 m.
Knowing the resistance to the movement of the apparatus, it is possible to calculate the engine power required to ensure its movement at a given speed (in this example, 120 km / h), taking the efficiency of the propeller η p equal to 0.6, and the efficiency of transmission from the engine to the propeller η p \u003d 0 ,nine:
A two-bladed propeller is most often used as an air propeller for amateur WUAs (Fig. 13).
The blank for such a screw can be glued from plywood, ash or pine plates. The edge, as well as the ends of the blades, which are subjected to mechanical action of solid particles or sand sucked in with the air flow, are protected by a brass sheet metal frame.
Four-blade propellers are also used. The number of blades depends on the operating conditions and the purpose of the propeller - for developing a high speed or creating a significant thrust force at the time of launch. A two-bladed propeller with wide blades can provide sufficient thrust. The thrust force, as a rule, increases if the propeller operates in a profiled nozzle ring.
The finished screw must be balanced, mainly statically, before mounting on the motor shaft. Failure to do so generates vibrations during rotation, which could damage the entire unit. Balancing with an accuracy of 1 g is sufficient for amateurs. In addition to balancing the screw, check its runout relative to the axis of rotation.
General layout
One of the main tasks of the designer is to connect all units into one functional whole. When designing an apparatus, the designer is obliged to provide a place within the hull for the crew, the placement of the units of the lifting and propulsion systems. In this case, it is important to use the designs of already known WUAs as a prototype. In fig. Figures 14 and 15 show the structural diagrams of two typical amateur WUAs.In most WUAs, the body is a load-bearing element, a single structure. It contains the units of the main power plant, air ducts, control devices and the driver's cab. The driver's cabs are located in the bow or in the central part of the device, depending on where the supercharger is located - behind or in front of it. If the WUA is multi-seat, the cabin is usually located in the middle of the vehicle, which allows it to be operated with a different number of people on board without changing its alignment.
In small amateur AVUs, the driver's seat is most often open, protected by a windshield in front. In devices of a more complex design (tourist type), the cabins are closed by a dome made of transparent plastic. To accommodate the necessary equipment and stocks use the volumes available on the sides of the cab and under the seats.
With air engines, AUA control is carried out using either rudders located in the air flow behind the propeller, or guiding devices fixed in the air flow emanating from the air-jet propulsion device. Control of the apparatus from the driver's seat can be of an aviation type - using the handles or levers of the steering wheel, or, as in a car - with the steering wheel and pedals.
In amateur WUAs, there are two main types of fuel systems; with gravity feed and with an automobile or aircraft type gasoline pump. Parts of the fuel system, such as valves, filters, oil system together with tanks (if a four-stroke engine is used), oil coolers, filters, a water cooling system (if it is a water-cooled engine), are usually selected from existing aviation or automotive parts.
Exhaust gases from the engine are always discharged to the rear of the apparatus and never to the pillow. To reduce the noise that occurs during the operation of WUAs, especially near settlements, automobile-type mufflers are used.
In the simplest designs, the lower body serves as a chassis. The role of the chassis can be played by wooden skids (or skids), which take on the load upon contact with the surface. In tourist WUAs, which are distinguished by a greater mass than sports ones, wheeled chassis are mounted, which facilitate the movement of WUAs during parking. Usually, two wheels are used, installed on the sides or along the longitudinal axis of the WUA. The wheels come into contact with the surface only after the lifting system stops working, when the WUA touches the surface.
Materials and manufacturing technology
High-quality pine timber similar to those used in aircraft construction, as well as birch plywood, ash, beech and linden timber are used for the manufacture of WUA wooden structures. For gluing wood, a waterproof glue with high physical and mechanical properties is used.For flexible fences, technical fabrics are mainly used; they must be extremely durable, resistant to weathering and humidity, as well as to friction. In Poland, fire-resistant fabric covered with plastic PVC is most often used.
It is important to cut correctly and ensure that the panels are carefully connected to each other, as well as fastened to the device. To fasten the shell of the flexible fence to the body, metal strips are used, which by means of bolts evenly press the fabric against the body of the apparatus.
When designing a form of flexible air cushion enclosure, one should not forget about Pascal's law, which states: air pressure spreads in all directions with equal force. Therefore, the shell of a flexible barrier in an inflated state must be in the form of a cylinder or a sphere, or a combination thereof.
Case design and strength
The forces from the load carried by the apparatus, the weight of the power plant mechanisms, etc., are transferred to the body of the WUA, and also the loads from external forces, impacts of the bottom against the wave and from the pressure in the air cushion act. The supporting structure of the hull of an amateur WUA is most often a flat pontoon, which is supported by the pressure in an air cushion, and in the swimming mode ensures the buoyancy of the hull. The body is acted upon by concentrated forces, bending and twisting moments from the motors (Fig. 16), as well as gyroscopic moments from the rotating parts of the mechanisms that arise when the AUA maneuvers.The most widespread are two constructive types of buildings for amateur WUAs (or their combinations):
- truss structure, when the overall strength of the hull is provided with the help of flat or spatial trusses, and the sheathing is intended only to retain air in the air path and create buoyancy volumes;
- with load-bearing planking, when the overall strength of the hull is provided by the outer plating, working in conjunction with the longitudinal and transverse set.
The design of the cab and its glazing must ensure that the driver and passengers can quickly exit the cab, especially in the event of an accident or fire. The location of the glasses should provide the driver with a good view: the line of sight should be within the range from 15 ° down to 45 ° up from the horizontal line; lateral vision must be at least 90 ° on each side.
Power transfer to propeller and blower
V-belt and chain drives are the most simple for amateur manufacturing. However, the chain drive is used only to drive propellers or blowers, the axes of rotation of which are located horizontally, and even then only if it is possible to select the appropriate motorcycle sprockets, since their manufacture is rather difficult.In the case of V-belt transmission, in order to ensure the durability of the belts, the diameters of the pulleys should be selected as large as possible, however, the circumferential speed of the belts should not exceed 25 m / s.
Construction of the lifting complex and flexible fencing
The lifting complex consists of an injection unit, air channels, a receiver and a flexible air cushion enclosure (in nozzle circuits). The ducts through which the air is supplied from the blower to the flexible enclosure must be designed taking into account the requirements of aerodynamics and ensure minimum pressure losses.Flexible fencing for amateur WUAs usually has a simplified form and design. In fig. 18 shows examples of constructive diagrams of flexible barriers and a method for checking the shape of a flexible barrier after mounting it on the body of the apparatus. Fences of this type have good elasticity, and due to their rounded shape they do not cling to unevenness of the supporting surface.
The calculation of blowers, both axial and centrifugal, is rather complicated and can only be performed using specialized literature.
A steering device usually consists of a steering wheel or pedals, a system of levers (or cable harness) connected to a vertical rudder, and sometimes to a horizontal rudder - an elevator.
The control can be made in the form of a car or motorcycle steering wheel. Considering, however, the specifics of the design and operation of the WUA as aircraft, more often use the aviation design of controls in the form of a lever or pedals. In its simplest form (Fig. 19), when the handle is tilted to the side, the movement is transmitted by means of a lever attached to the pipe to the elements of the steering cable and then to the rudder. The forward and backward movements of the handle due to its articulation are transmitted through a pusher running inside the tube to the elevator wiring.
With pedal control, regardless of its scheme, it is necessary to provide for the possibility of moving either the seat or the pedals for adjustment in accordance with the individual characteristics of the driver. Levers are most often made of duralumin, the transmission pipes are attached to the body with brackets. The movement of the levers is limited by the openings of the cutouts in the guides mounted on the sides of the apparatus.
An example of the rudder design in the case of its placement in the air flow thrown by the propeller is shown in Fig. 20.
The rudders can be either fully rotary, or consist of two parts - non-rotary (stabilizer) and rotary (rudder blade) with different percentages of the chords of these parts. Any type of rudder section must be symmetrical. The rudder stabilizer is usually fixed to the housing; the main bearing element of the stabilizer is the spar, to which the rudder blade is suspended on the hinges. Elevators, very rarely found in amateur WUAs, are designed according to the same principles and sometimes even are exactly the same as rudders.
Structural elements that transfer motion from the controls to the steering wheels and throttle valves of engines usually consist of levers, rods, cables, etc. The rods, as a rule, transfer forces in both directions, while the cables only work for traction. Most often, amateur WUAs use combined systems - with cables and pushers.
From the editor
Hovercraft are getting more and more attention of fans of powerboat and tourism. With relatively low power consumption, they allow you to achieve high speeds; shallow and impassable rivers are accessible to them; the hovercraft can hover both over the ground and over ice.For the first time, we introduced our readers to the issues of designing small hovercraft in the 4th issue (1965), placing the article by Yu. A. Budnitskiy "Soaring ships". In a brief outline of the development of foreign SVPs was published, including a description of a number of sports and walking modern 1- and 2-seater SVPs. With the experience of independent construction of such an apparatus by a resident of Riga, OO Petersons, the editors introduced V. The publication about this amateur design aroused a particularly great interest among our readers. Many of them wanted to build the same amphibian and asked to indicate the necessary literature.
This year the publishing house "Shipbuilding" is publishing a book by the Polish engineer Jerzy Benja "Models and Amateur Hovercraft". In it you will find an exposition of the basics of the theory of the formation of an air cushion and the mechanics of movement on it. The author gives the design ratios that are necessary for the independent design of the simplest hovercraft, introduces the trends and prospects for the development of this type of ships. The book contains many examples of designs of amateur hovercraft (AHU) built in Great Britain, Canada, USA, France, Poland. The book is addressed to a wide range of amateurs of independent construction of ships, ship modelers, and watercraft. Its text is richly illustrated with drawings, drawings and photographs.
The journal publishes an abridged translation of a chapter from this book.
The four most popular foreign SVPs
American SVP "Airskat-240"
A two-seater sports hovercraft with a symmetrical transverse arrangement of seats. Mechanical installation - car dv. Volkswagen with a capacity of 38 kW, driving an axial four-bladed supercharger and a two-bladed propeller in the ring. The control of the SVP along the course is carried out using a lever associated with the rudder system located in the stream behind the propeller. Electrical equipment 12 V. Engine start - electric starter. The dimensions of the apparatus are 4.4x1.98x1.42 m. The area of \u200b\u200bthe air cushion is 7.8 m 2; the diameter of the propeller is 1.16 m, the gross weight is 463 kg, the maximum speed on the water is 64 km / h.American SVP of "Skimmers Incorporated"
A kind of single SVP motor scooter. The body design is based on the idea of \u200b\u200busing a car camera. Two-cylinder motorcycle motor with a power of 4.4 kW. The dimensions of the apparatus are 2.9x1.8x0.9 m. The area of \u200b\u200bthe air cushion is 4.0 m 2; gross weight - 181 kg. The maximum speed is 29 km / h.Air Ryder British SVP
This two-seater sports apparatus is one of the most popular among amateur shipbuilders. The axial supercharger is driven by a motorcycle, dv. working volume 250 cm 3. The propeller is two-bladed, wooden; powered by a separate 24 kW motor. Electrical equipment with a voltage of 12 V with an aircraft battery. Engine start - electric starter. The device has dimensions 3.81x1.98x2.23 m; clearance of 0.03 m; ascent 0.077 m; pillow area 6.5 m 2; unladen weight 181 kg. Develops a speed of 57 km / h on water, 80 km / h on land; overcomes inclines up to 15 °.Table 1 shows the data for a single modification of the apparatus.
English SVP "Hovercat"
Light tourist boat for five to six people. There are two modifications: "MK-1" and "MK-2". A centrifugal blower with a diameter of 1.1 m is driven by a car. dv. Volkswagen has a working volume of 1584 cm 3 and consumes 34 kW at 3600 rpm.In the modification "MK-1" the movement is carried out by means of a propeller with a diameter of 1.98 m, driven into rotation by a second engine of the same kind.
In the modification "MK-2" for horizontal thrust used car. dv. "Porsche 912" with a volume of 1582 cm 3 and a power of 67 kW. The vehicle is controlled by aerodynamic rudders placed in the flow behind the propeller. Electrical equipment with a voltage of 12 V. The dimensions of the apparatus are 8.28x3.93x2.23 m. The area of \u200b\u200bthe air cushion is 32 m 2, the total weight of the apparatus is 2040 kg, the speed of movement of the MK-1 modification is 47 km / h, the MK-2 is 55 km / h.
Notes
1. A simplified technique for selecting a propeller based on a known resistance value, rotational speed and forward speed is given in.2. Calculations of V-belt and chain drives can be performed using the standards generally accepted in domestic mechanical engineering.
To buy a cat on an airbag you don't have to go through complicated registration procedures. To own such a technique, no special permits are required. Therefore, the sales contract, complete with the vehicle's passport, already allows you to dispose of the cat as your property without any problems.
This type of transport belongs to the category of small vessels and is registered in the State Inspection for Small Vessels (State Inspection for Small Vessels). In order to fully manage your ship, you will have to register the boat and obtain the rights to operate small boats. Both of these procedures are fairly straightforward. Check the list of documents in your department of GIMS. Each department and inspector may have different reception days, and there may also be some unique subtleties in design. Therefore, feel free to go to GIMS, there you are obliged to explain everything in detail. The most troublesome of all of the above is getting medical certificate, when registering management rights. The certificate is needed exactly the same as when obtaining a driver's license.
What happens if the inspector catches you?
If this is a GIMS inspector, then you will not face a large fine. Remember! The inspector can detain the ship and transport it to the impounding yard only if you refused to undergo a medical examination.
An air cushion can also move on the ground. This means that representatives of the ground authorities can contact you. It is important to know that it is strictly forbidden to travel on public roads on the SVP. For violation you face a fine. At the same time, law enforcement agencies have the right to require you to present a confirming document that it is you who are the owner of the airbag boat. To draw up the protocol, the presence of the inspector of the State Inspection Service is required. GIMS branches exist in the number of one branch per region. It is rather problematic to wait for the representative of the State Inspection for Small Vessels while on land.
From this it follows that theoretically you can move on land without any documents and rights, without leaving on roads intended for public use. Therefore, if you decide to check the purchased cat on an airbag in the nearest vacant lot, then you have practically nothing to fear.
Trailer design and is category BE needed
The larger the boat, the larger, and therefore more expensive, the trailer for it. Moreover, for a trailer with a carrying capacity of more than 750 kilograms, you need to open an additional category in your driver's license.
If the weight of the trailer does not exceed 750 kg and the total weight of the vehicle, trailer and cargo does not exceed 3.5 tons, then you can safely transport your boat - everything is legal!
Optional equipment
Depending on where and how you will operate the ship, you need to immediately take care of purchasing additional necessary equipment. Due to the incredible maneuverability of the boat, its owners were more than once stuck in such inaccessible places that they could return later only with the help of a helicopter or other SVP. A walkie-talkie, satellite phone or other means of communication must be with you when it comes to long trips to places where a person rarely steps.
When setting off, remember the moment that the pilots call the "point of no return", when the fuel tanks are exactly half empty. But during the trip, from overwhelming emotions, the owners of the air cushion are often forgotten and often find themselves in unpleasant situations. Consider additional emergency fuel in advance.
Not a single sale of a boat on an air bag is complete without a careful selection of spare parts and a simple, but so indispensable in an emergency, additional equipment.
That's all. Now you are familiar with all the basic nuances of purchasing an airbag boat.
The construction of a vehicle that would allow movement both on land and on water was preceded by an acquaintance with the history of the discovery and creation of original amphibians - hovercraft (WUA), study of their fundamental structure, comparison various designs and schemes.
For this purpose, I visited many Internet sites of enthusiasts and creators of WUAs (including foreign ones), and got acquainted with some of them on the spot.
In the end, the English "Hovercraft" ("soaring ship" - as the WUA is called in Great Britain), built and tested by local enthusiasts, took the prototype of the planned boat. Our most interesting domestic machines of this type were mostly created for law enforcement agencies, and in recent years - for commercial purposes, had large dimensions, and therefore were not suitable for amateur manufacturing.
My hovercraft (I call it "Aerojeep") is a three-seater: the pilot and passengers are arranged in a T-shape, like on a tricycle: the pilot is in front in the middle, and the passengers are next to each other, next to each other. The machine is single-engine, with a split air flow, for which a special panel is installed in its annular channel slightly below its center.
| Hovercraft technical data | |
|---|---|
| Overall dimensions, mm: | |
| length | 3950 |
| width | 2400 |
| height | 1380 |
| Engine power, hp from. | 31 |
| Weight, kg | 150 |
| Carrying capacity, kg | 220 |
| Fuel capacity, l | 12 |
| Fuel consumption, l / h | 6 |
| Overcoming obstacles: | |
| rise, hail. | 20 |
| wave, m | 0,5 |
| Cruising speed, km / h: | |
| on water | 50 |
| on the ground | 54 |
| on ice | 60 |
It consists of three main parts: a propeller-driven installation with a transmission, a fiberglass body and a "skirt" - a flexible enclosure of the lower part of the body - so to speak, a "pillowcase" of an air cushion.
 1 - segment (dense tissue); 2 - mooring cleat (3 pcs.); 3 - wind visor; 4 - side plate for fastening segments; 5 - handle (2 pcs.); 6 - propeller guard; 7 - annular channel; 8 - rudder (2 pcs.); 9 - rudder control lever; 10 - access hatch to the gas tank and battery; 11 - pilot's seat; 12 - passenger sofa; 13 - engine casing; 14 - engine; 15 - outer shell; 16 - filler (foam); 17 - inner shell; 18 - dividing panel; 19 - propeller; 20 - propeller bushing; 21 - drive gear belt; 22 - unit for fastening the lower part of the segment. enlarge, 2238x1557, 464 KB |
Hovercraft hull
It is double: fiberglass, consists of an inner and an outer shell.
The outer shell has a rather simple configuration - it is only inclined (about 50 ° to the horizontal) sides without a bottom - flat almost over the entire width and slightly curved in the upper part. The bow is rounded, and the rear looks like an inclined transom. In the upper part, along the perimeter of the outer shell, oblong holes-grooves are cut, and at the bottom, outside, a cable covering the shell is fixed in eye-bolts for attaching the lower parts of the segments to it.
The configuration of the inner shell is more complicated than the outer one, since it has almost all the elements of a small vessel (say, a boat or a boat): sides, bottom, curved gunwales, a small deck in the bow (only the upper part of the transom is missing in the stern), while as one piece. In addition, in the middle of the cockpit along it, a separately molded tunnel with a can under the driver's seat is glued to the bottom. It houses a fuel tank and a battery, as well as a "gas" cable and a rudder control cable.
In the aft part of the inner shell, a kind of hut is arranged, raised and open in front. It serves as the base of the annular channel for the propeller, and its bulkhead deck serves as an air flow divider, part of which (supporting flow) is directed into the shaft opening, and the other part - to create a propulsive thrust force.
All elements of the case: the inner and outer shells, the tunnel and the annular channel, were glued on matrices of glass mat with a thickness of about 2 mm on polyester resin. Of course, these resins are inferior to vinyl ester and epoxy resins in adhesion, filtration level, shrinkage, and release of harmful substances when drying, but they have an undeniable price advantage - they are much cheaper, which is important. For those who intend to use such resins, let me remind you that the room where the work is carried out must have good ventilation and a temperature of at least 22 ° C.
The matrices were made in advance according to the master model from the same glass mats on the same polyester resin, only the thickness of their walls was larger and amounted to 7-8 mm (for the case shells - about 4 mm). Before gluing the elements, all roughness and galls were carefully removed from the working surface of the matrix, and it was covered three times with wax diluted in turpentine and polished. After that, a thin layer (up to 0.5 mm) of gelcoat (colored varnish) of the selected yellow color was applied to the surface with a spray gun (or roller).
After it had dried, the process of gluing the shell began using the following technology. First, using a roller, the wax surface of the matrix and the side of the glass mat with smaller pores are coated with resin, and then the mat is placed on the matrix and rolled until air is completely removed from under the layer (if necessary, you can make a small cut in the mat). In the same way, the subsequent layers of glass mats are laid to the required thickness (4-5 mm), with the installation, where necessary, of embedded parts (metal and wood). Excessive flaps at the edges are cut off when gluing "wet".
After the resin hardens, the shell is easily removed from the matrix and processed: the edges are turned, grooves are cut, holes are drilled.
To ensure the unsinkability of the "Aerodzhip", pieces of foam plastic (for example, furniture) are glued to the inner shell, leaving only the channels for the passage of air around the entire perimeter free. The pieces of foam are glued together with resin, and attached to the inner shell with strips of glass mat, also oiled with resin.
After manufacturing the outer and inner shells separately, they are docked, fastened with clamps and self-tapping screws, and then joined (glued) along the perimeter with strips of the same glass mat coated with polyester resin, 40-50 mm wide, from which the shells themselves were made. After that, the housing is left until the resin has completely polymerized.
A day later, a duralumin strip with a cross section of 30x2 mm is attached to the upper junction of the shells along the perimeter with rivets, setting it vertically (the tongues of the segments are fixed on it). Wooden runners with dimensions of 1500x90x20 mm (length x width x height) are glued to the bottom of the bottom at a distance of 160 mm from the edge. One layer of glass mat is glued on top of the runners. In the same way, only from the inside of the shell, in the aft part of the cockpit, is a base made of a wooden plate for the engine.
It is worth noting that using the same technology as the outer and inner shells were made, smaller elements were also glued: the inner and outer shell of the diffuser, steering wheels, gas tank, engine cover, wind damper, tunnel and driver's seat. For those who are just starting to work with fiberglass, I recommend preparing the manufacture of a boat from these small elements. The total mass of the fiberglass body with diffuser and rudders is about 80 kg.
Of course, the manufacture of such a hull can also be entrusted to specialists - firms producing fiberglass boats and cutters. Fortunately, there are many of them in Russia, and the costs will be commensurate. However, in the process of self-manufacturing, it will be possible to gain the necessary experience and the ability in the future to model and create various elements and structures from fiberglass.
Propeller-driven installation of an air cushion boat
It includes an engine, a propeller and a transmission that transfers torque from the first to the second.
The engine is used by BRIGGS & STATTION, produced in Japan under an American license: 2-cylinder, V-shaped, four-stroke, 31 hp. from. at 3600 rpm. Its guaranteed service life is 600 thousand hours. Starting is carried out by an electric starter, from the battery, and the spark plugs are powered by a magneto.
The engine is mounted on the bottom of the Aerojip body, and the propeller hub axis is fixed at both ends on brackets in the center of the diffuser, raised above the body. The transmission of torque from the motor output shaft to the hub is carried out by a toothed belt. The driven and driving pulleys, like the belt, are toothed.
Although the mass of the engine is not so great (about 56 kg), its location on the bottom significantly lowers the center of gravity of the boat, which has a positive effect on the stability and maneuverability of the vehicle, especially this one - "aeronautical".
Exhaust gas is directed to the lower air stream.
Instead of the installed Japanese one, you can also use suitable domestic engines, for example, from the Buran, Lynx snowmobiles and others. By the way, engines with a capacity of about 22 hp are quite suitable for a one- or two-seat WUA. from.
The propeller is six-bladed, with a fixed pitch (set on land by the angle of attack) of the blades.
 1 - walls; 2 - cover with tongue. |
The annular channel of the propeller should also be attributed to an integral part of the propeller-driven installation, although its base (lower sector) is made integral with the inner shell of the body. The annular channel, like the body, is also composite, glued from the outer and inner shells. Just in the place where the lower sector joins the upper one, a fiberglass dividing panel is arranged: it divides the air flow created by the propeller (and, on the contrary, connects the walls of the lower sector along a chord).
The engine, located at the transom in the cockpit (behind the back of the passenger seat), is closed from above with a fiberglass hood, and the propeller, in addition to the diffuser, is also a wire grille in front.
The soft elastic cushion of the air cushion boat (skirt) consists of separate but identical segments, cut and sewn from dense lightweight fabric. It is desirable that the fabric is water-repellent, does not harden in the cold and does not allow air to pass through. I used Finnish Vinyplan material, but a domestic fabric such as percale is fine. The pattern of the segment is simple, and you can even sew it manually.
Each segment is attached to the body as follows. The tongue is thrown over the side vertical strip, with an overlap of 1.5 cm; on it - the tongue of the adjacent segment, and both of them in the place of the overlap are fixed on the bar with a special clip of the "crocodile" type, only without teeth. And so along the entire perimeter of the "Aerodzhip". For reliability, you can also put a clip in the middle of the tongue. The two lower corners of the segment, with the help of nylon clamps, are suspended freely on a cable that wraps around the lower part of the outer shell of the body.
Such a composite skirt design allows you to easily replace a failed segment, which will take 5-10 minutes. It will be worthwhile to say that the structure turns out to be operational if up to 7% of the segments fail. In total, there are up to 60 of them on the skirt.
Movement principle hovercraft following. After starting and idling the engine, the unit remains in place. As the number of revolutions increases, the propeller begins to drive a more powerful air flow. Part of it (large) creates propulsive force and propels the boat forward. The other part of the flow goes under the dividing panel into the side air ducts of the hull (free space between the shells to the very nose), and then evenly enters the segments through the holes-grooves in the outer shell. This flow, simultaneously with the start of movement, creates an air cushion under the bottom, raising the vehicle above the underlying surface (whether it is soil, snow or water) by several centimeters.
The "Aerojip" is turned by two rudders, deflecting the "forward" air flow to the side. The steering wheels are controlled from a motorcycle-type two-armed steering column lever, through a Bowden cable running along the starboard side between the shells to one of the steering wheels. The other rudder is connected to the first rigid rod.
On the left handle of the two-armed lever, the carburetor throttle control lever (analogue of the throttle handle) is also fixed.
To operate a hovercraft, it must be registered with the local state small craft inspectorate (GIMS) and receive a ship ticket. To obtain a certificate for the right to drive a boat, you also need to take a course in management.
However, even at these courses, there are still far from everywhere instructors for piloting hovercraft. Therefore, each pilot has to master the WUA management independently, literally bit by bit, gaining relevant experience.