The unsatisfactory condition of the highway network and the almost complete absence of road infrastructure on most regional routes forces us to look for vehicles operating on different physical principles. One such means is a hovercraft capable of moving people and cargo in off-road conditions.
Hovercraft carrying sonorous technical term“Hovercraft” differs from traditional models of boats and cars not only in its ability to move on any surface (pond, field, swamp, etc.), but also in the ability to develop decent speed. The only requirement for such a “road” is that it must be more or less smooth and relatively soft.
However, the use of an air cushion by an all-terrain boat requires quite serious energy costs, which in turn entails a significant increase in fuel consumption. The operation of hovercraft (hovercraft) is based on a combination of the following physical principles:
- Low specific pressure of the hovercraft on the surface of the soil or water.
- High speed movement.
This factor has a fairly simple and logical explanation. The area of contact surfaces (the bottom of the apparatus and, for example, the soil) corresponds to or exceeds the area of the hovercraft. Technically speaking, the vehicle dynamically creates the required amount of support thrust.
Excessive pressure created in a special device lifts the machine from the support to a height of 100-150 mm. It is this cushion of air that interrupts the mechanical contact of the surfaces and minimizes the resistance to the translational movement of the hovercraft in the horizontal plane.
Despite the ability for fast and, most importantly, economical movement, the scope of application of a hovercraft on the surface of the earth is significantly limited. Asphalt areas, hard rocks with the presence of industrial waste or hard stones are absolutely unsuitable for it, since the risk of damage to the main element of the hovercraft - the bottom of the cushion - increases significantly.
Thus, the optimal hovercraft route can be considered one where you need to swim a lot and drive a little in places. In some countries, such as Canada, hovercraft are used by rescuers. According to some reports, devices of this design are in service with the armies of some NATO member countries.
Why do you want to make a hovercraft with your own hands? There are several reasons:
That is why SVPs have not become widespread. Indeed, you can buy an ATV or a snowmobile as an expensive toy. Another option is to make a boat-car yourself.
When choosing a working scheme, it is necessary to decide on a housing design that optimally meets the given technical conditions. Note, do-it-yourself hovercraft with assembly drawings homemade elements it is quite possible to create.
Specialized resources abound with ready-made drawings of homemade hovercraft. An analysis of practical tests shows that the most successful option, satisfying the conditions that arise when moving on water and soil, are pillows formed by the chamber method.
When choosing a material for the main structural element of an hovercraft - the body, consider several important criteria. Firstly, it is simplicity and ease of processing. Secondly, small specific gravity material. It is this parameter that ensures that the hovercraft belongs to the “amphibious” category, that is, there is no risk of flooding in the event emergency stop vessel.
As a rule, 4 mm plywood is used to make the body, and the superstructures are made of foam plastic. This significantly reduces the dead weight of the structure. After gluing the external surfaces with penoplex and subsequent painting, the model acquires its original features appearance original. Polymer materials are used to glaze the cabin, and the remaining elements are bent from wire.
Making a so-called skirt will require a dense, waterproof fabric made of polymer fiber. After cutting, the parts are sewn together with a double tight seam, and gluing is done using waterproof glue. This ensures not only a high degree of structural reliability, but also allows you to hide the installation joints from prying eyes.
The design of the power plant assumes the presence of two engines: marching and forcing. They are equipped with brushless electric motors and two-blade propellers. A special regulator carries out the process of managing them.
The supply voltage is supplied from two rechargeable batteries, the total capacity of which is 3,000 milliamps per hour. At the maximum charge level, the hovercraft can be operated for 25-30 minutes.
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It all started with the fact that I wanted to do some project and involve my grandson in it. I have a lot of engineering experience behind me, so simple projects I wasn’t looking, and then one day, while watching TV, I saw a boat that was moving due to the propeller. "Cool stuff!" - I thought, and began to scour the Internet in search of at least some information.
We took the motor from an old lawn mower, and bought the layout itself (costs $30). It is good because it requires only one motor, while most similar boats require two engines. From the same company we bought the propeller, propeller hub, air cushion fabric, epoxy resin, fiberglass and screws (they sell them all in one kit). The rest of the materials are quite commonplace and can be purchased at any hardware store. The final budget was a little over $600.
Step 1: Materials
Materials you will need: polystyrene foam, plywood, kit from Universal Hovercraft (~$500). The kit contains all the little things you will need to complete the project: plan, fiberglass, propeller, propeller hub, air cushion fabric, glue, epoxy resin, bushings, etc. As I wrote in the description, all materials cost about $600.
Step 2: Making the frame
We take polystyrene foam (5 cm thick) and cut out a 1.5 by 2 meter rectangle from it. Such dimensions will ensure buoyancy of a weight of ~270 kg. If 270 kg seems not enough, you can take another sheet of the same type and attach it below. We cut out two holes with a jigsaw: one for the incoming air flow and the other for inflating the pillow.
Step 3: Cover with fiberglass
The lower part of the body must be waterproof, for this we cover it with fiberglass and epoxy. In order for everything to dry properly, without unevenness and roughness, you need to get rid of any air bubbles that may arise. For this you can use industrial vacuum cleaner. We cover the fiberglass with a layer of film, then cover it with a blanket. The covering is necessary to prevent the blanket from sticking to the fiber. Then we cover the blanket with another layer of film and glue it to the floor with adhesive tape. We make a small cut, insert the trunk of the vacuum cleaner into it and turn it on. We leave it in this position for a couple of hours, when the procedure is completed, the plastic can be scraped off from the fiberglass without any effort, it will not stick to it.
Step 4: Bottom Case is Ready
The lower part of the body is ready, and now it looks something like the photo.
Step 5: Making the Pipe
The pipe is made of styrofoam, 2.5 cm thick. It is difficult to describe the whole process, but in the plan it is described in detail, we did not have any problems at this stage. Let me just note that the plywood disk is temporary and will be removed in subsequent steps.
Step 6: Motor Holder
The design is not tricky; it is made of plywood and blocks. Placed exactly in the center of the boat hull. Attaches with glue and screws.
Step 7: Propeller
The propeller can be purchased in two forms: ready-made and “semi-finished”. Ready-made ones are usually much more expensive, and buying a semi-finished product can save a lot of money. That's what we did.
The closer the propeller blades are to the edges of the air vent, the more efficiently the latter works. Once you have decided on the gap, you can sand the blades. Once the grinding is completed, it is necessary to balance the blades so that there are no vibrations in the future. If one of the blades weighs more than the other, then the weight needs to be equalized, but not by cutting the ends, or by grinding. Once the balance is found, you can apply a couple of layers of paint to maintain it. For safety, it is advisable to paint the tips of the blades in White color.
Step 8: Air Chamber
The air chamber separates the flow of incoming and outgoing air. Made from 3 mm plywood.
Step 9: Installing the Air Chamber
The air chamber is attached with glue, but you can also use fiberglass; I always prefer to use fiber.
Step 10: Guides
The guides are made of 1 mm plywood. To give them strength, cover them with one layer of fiberglass. It’s not very clear in the photo, but you can still see that both guides are connected together at the bottom with an aluminum strip, this is done so that they work synchronously.
Step 11: Shape the Boat and Add Side Panels
The outline of the shape/contour is made on the bottom, after which a wooden plank is attached with screws according to the outline. 3mm plywood bends well and fits right into the shape we need. Next, we fasten and glue a 2 cm beam along the upper edge of the plywood sides. Add cross beam, and install the handle, which will be the steering wheel. We attach cables to it extending from the guide blades installed earlier. Now you can paint the boat, preferably applying several layers. We chose white; even with prolonged direct sunlight, the body practically does not heat up.
I must say that she swims briskly, and this makes me happy, but it surprised me steering. At medium speeds turns are possible, but at high speed The boat first skids to the side, and then, due to inertia, it moves backwards for some time. Although, after getting used to it a little, I realized that tilting my body in the direction of the turn and slightly slowing down the gas can significantly reduce this effect. It’s difficult to say the exact speed, because there is no speedometer on the boat, but it feels quite good, and there is still a decent wake and waves left behind the boat.
On the day of the test, about 10 people tried the boat, the heaviest weighed about 140 kg, and it withstood it, although of course it was not possible to achieve the speed that was available to us. With a weight of up to 100 kg, the boat moves briskly.
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The high speed characteristics and amphibious capabilities of hovercraft, as well as the comparative simplicity of their designs, attract the attention of amateur designers. In recent years, many small WUAs have appeared, built independently and used for sports, tourism or business trips.
In some countries, such as the UK, USA and Canada, serial industrial production small WUAs; We offer ready-made devices or kits of parts for self-assembly.
A typical sports AVP is compact, simple in design, has lifting and movement systems independent from each other, and can be easily moved both above ground and above water. These are predominantly single-seat vehicles with carburetor motorcycle or light air-cooled automobile engines.
Tourist WUAs are more complex in design. They are usually two- or four-seater, designed for relatively long trips and, accordingly, have luggage racks, large-capacity fuel tanks, and devices to protect passengers from bad weather.
For economic purposes, small platforms are used, adapted for transporting mainly agricultural goods over rough and swampy terrain.
Main characteristics
Amateur AVPs are characterized by main dimensions, weight, supercharger diameter and propeller, the distance from the center of mass of the airborne vehicle to the center of its aerodynamic drag.In table 1 compares the most important technical data of the most popular English amateur AVPs. The table allows you to navigate a wide range of values of individual parameters and use them for comparative analysis with your own projects.
The lightest WUAs weigh about 100 kg, the heaviest - more than 1000 kg. Naturally, the smaller the mass of the device, the less engine power is required to move it, or the higher the performance can be achieved with the same power consumption.
Below are the most typical data on the mass of individual components that make up the total mass of an amateur AVP: air-cooled carburetor engine - 20-70 kg; axial blower. (pump) - 15 kg, centrifugal pump - 20 kg; propeller - 6-8 kg; motor frame - 5-8 kg; transmission - 5-8 kg; propeller ring-nozzle - 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 cargo transported, fuel and oil reserves necessary to ensure the required cruising range.
In parallel with calculating the mass of the AVP, an accurate calculation of the position of the center of gravity is required, since the driving performance, stability and controllability of the device depend on this. The main condition is that the resultant of the forces supporting the air cushion passes through the common center of gravity (CG) of the apparatus. It is necessary to take into account that all masses that change their value during operation (such as fuel, passengers, cargo) must be placed close to the CG of the device so as not to cause its movement.
The center of gravity of the device is determined by calculation according to the drawing of the side projection of the device, where the centers of gravity of individual units, structural components of passengers and cargo are plotted (Fig. 1). Knowing the masses G i and the coordinates (relative to the coordinate axes) x i and y i of their centers of gravity, we can determine the position of the CG of the entire apparatus using the formulas:
The designed amateur AVP must meet certain operational, design and technological requirements. The basis for creating a design and construction of a new type of WUA is, first of all, the initial data and technical specifications, which determine the type of apparatus, its purpose, total weight, carrying capacity, dimensions, type of main power plant, driving 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, as well as complete safety of operation.
Talking about driving characteristics, imply the hovering height of the AVP and the ability to overcome obstacles associated with this quality, maximum speed and throttle response, as well as the braking distance, stability, controllability, and range.
In the design of the AVP, the shape of the body plays a fundamental role (Fig. 2), which is a compromise between:
- a) round contours, which are characterized by the best parameters of the air cushion at the moment of hovering in place;
- b) teardrop-shaped contours, which is preferable from the point of view of reducing aerodynamic drag when moving;
- c) a hull shape pointed at the nose (“beak-shaped”), optimal from a hydrodynamic point of view when moving along a rough water surface;
- d) a form that is optimal for operational purposes.
Using statistical data on existing structures that correspond to the newly created type of WUA, the designer must establish:
- weight of the apparatus G, kg;
- air cushion area S, m2;
- length, width and outline of the body in plan;
- lifting system motor power N v.p. , kW;
- traction motor power N motor, kW.
- pressure in the air cushion P v.p. = G:S;
- specific power of the lifting system q v.p. = G:N ch. .
- specific power of the traction motor q dv = G:N dv, and also begin developing the AVP configuration.
The principle of creating an air cushion, superchargers
Most often, when constructing amateur AVPs, two schemes for forming an air cushion are used: chamber and nozzle.In a chamber circuit, most often used in simple designs, the volumetric flow rate of air passing through the air path of the device is equal to the volumetric flow rate of the supercharger
Where:
F is the perimeter area of the gap between the supporting surface and the lower edge of the apparatus body, through which air exits from under the apparatus, m 2 ; it can be defined as the product of the perimeter of the air cushion fence P and the gap h e between the fence and the supporting surface; usually h 2 = 0.7÷0.8h, where h is the hovering height of the apparatus, m;
υ - speed of air flow from under the apparatus; with sufficient accuracy it can be calculated using the formula:
where R v.p. - pressure in the air cushion, Pa; g - free fall acceleration, m/s 2 ; y - air density, kg/m3.
The power required to create an air cushion in a chamber circuit is determined by the approximate formula:
where R v.p. - pressure behind the supercharger (in the receiver), Pa; η n - supercharger efficiency.
Air cushion pressure and air flow are the main parameters of the air cushion. Their values depend primarily on the size of the apparatus, i.e. on the mass and bearing surface, on the hovering altitude, the speed of movement, the method of creating an air cushion and the resistance in the air path.
The most economical hovercraft are large air-cushion vehicles or large load-bearing surfaces, in which the minimum pressure in the cushion allows one to obtain a sufficiently large load-carrying capacity. However, independent construction of a large-sized apparatus is associated with difficulties in transportation and storage, and is also limited by the financial capabilities of the amateur designer. When reducing the size of the AVP, 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 device: splashing while moving over water and dust when moving over a sandy surface or loose snow.
Apparently, a successful WUA design is, in a sense, a compromise between the contradictory dependencies described above.
In order to reduce the power consumption for the passage of air through the air channel from the supercharger into the cushion cavity, it must have minimal aerodynamic resistance (Fig. 3). The power losses that are inevitable when air passes through the channels of the air tract are of two types: losses due to the movement of air in straight channels of constant cross-section and local losses during expansion and bending of the channels.
In the air tract of small amateur AVPs, losses due to the movement of air flows along straight channels of constant cross-section are relatively small due to the insignificant length of these channels, as well as the thorough treatment of their surface. These losses can be estimated using the formula:
where: λ - pressure loss coefficient per channel length, calculated according to the graph shown in Fig. 4, depending on the Reynolds number Re=(υ·d):v, υ - speed of air passage in the channel, m/s; l - channel length, m; d - channel diameter, m (if the channel has a different round section, then d is the diameter of the equivalent area cross section cylindrical channel); v is the 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 air flow, as well as losses for air suction into the supercharger, nozzles and rudders constitute the main costs of supercharger power.
Here ζ m is the local loss coefficient, depending on the Reynolds number, which is determined by the geometric parameters of the loss source and the speed of air passage (Fig. 5-8).
The supercharger in the AVP 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 device in order to provide movement.
The total pressure created by the supercharger is the sum of static and dynamic pressure:
Depending on the type of AVP, the area of the air cushion, the lifting height of the device and the magnitude of losses, the components p sυ and p dυ vary. This determines the choice of type and performance of superchargers.
In a chamber air cushion circuit, the static pressure p sυ required to create lift 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 an AVP supercharger with a flexible air cushion enclosure (nozzle design), the static pressure behind the supercharger can be calculated using the approximate formula:
where: R v.p. - pressure in the air cushion under the bottom of the apparatus, kg/m2; kp is the pressure drop coefficient between the air cushion and the channels (receiver), equal to k p =P p:P v.p. (P p - pressure in the air channels behind the supercharger). The k p value ranges from 1.25÷1.5.
The volumetric air flow rate of the supercharger can be calculated using the formula:
Adjustment of the performance (flow rate) of AVP superchargers is carried out most often - by changing the rotation speed or (less often) by throttling the air flow in the channels using the rotary dampers located in them.
After calculated required power supercharger, you need to find an engine for it; Most often, hobbyists use motorcycle engines if power up to 22 kW is required. In this case, 0.7-0.8 is taken as the design power maximum power engine indicated in the motorcycle passport. It is necessary to provide 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 consists of the weight of the engine, the transmission between the supercharger and the engine, as well as the weight of the supercharger itself.
Depending on the type of AVP, engines with a displacement from 50 to 750 cm 3 are used.
In amateur AVPs, both axial and centrifugal superchargers are used equally. Axial blowers are intended for small and simple structures, centrifugal blowers are intended for air pumps with significant pressure in the air cushion.
Axial blowers typically have four blades or more (Figure 9). They are usually made of wood (four-blade blowers) 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 structure from steel sheet. The pressure range created by axial four-blade superchargers is 600-800 Pa (about 1000 Pa with a large number of blades); The efficiency of these superchargers reaches 90%.
Centrifugal blowers are made of welded metal construction or molded from fiberglass. The blades are made bent from thin sheet or with a profiled cross section. Centrifugal blowers create pressure up to 3000 Pa, and their efficiency reaches 83%.
Selection of traction complex
Propulsors that create horizontal thrust can be divided mainly into three types: air, water and wheel (Fig. 10).Air propulsion means an aircraft-type propeller with or without a nozzle ring, an axial or centrifugal supercharger, as well as an air-breathing propulsion unit. In the simplest designs, horizontal thrust can sometimes be created by tilting the AVP and using the resulting horizontal component of the force of the air flow flowing from the air cushion. The air propulsion device 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 a propeller or water-jet propulsion can be used. Compared to air engines, these thrusters make it possible to obtain significantly more thrust for every kilowatt of power expended.
The approximate value of thrust developed by various propulsors can be estimated from the data shown in Fig. eleven.
When choosing propeller elements, one should take into account all types of resistance that arise during the movement of the propeller. Aerodynamic drag is calculated using the formula
Water resistance caused by the formation of waves when the WUA moves through water can be calculated using the formula
Where:
V - speed of movement of the WUA, m/s; G is the mass of the AVP, kg; L is the length of the air cushion, m; ρ - density of water, kg s 2 / m 4 (at temperature sea water+4°C is 104, river - 102);
C x is the aerodynamic drag coefficient, depending on the shape of the vehicle; is determined by purging AVP models in wind tunnels. Approximately we can take C x =0.3÷0.5;
S is the cross-sectional area of the WUA - its projection onto a plane perpendicular to the direction of movement, m 2 ;
E is the coefficient of wave resistance, depending on the speed of the airfoil (Froude number Fr=V:√ g·L) and the ratio of the dimensions of the air cushion L:B (Fig. 12).
As an example in table. Figure 2 shows the calculation of resistance depending on the speed of movement for a device with length L = 2.83 m and B = 1.41 m.
Knowing the resistance to movement of the device, it is possible to calculate the engine power required to ensure its movement at a given speed (at in this example 120 km/h), taking the propeller efficiency η p equal to 0.6, and the transmission efficiency from the engine to the propeller η p = 0.9:
A two-blade propeller is most often used as an air propulsion device for amateur AVPs (Fig. 13).
The blank for such a screw can be glued together from plywood, ash or pine plates. The edge, as well as the ends of the blades, which are exposed to the mechanical action of solid particles or sand sucked in along with the air flow, are protected by a frame made of sheet brass.
Four-bladed propellers are also used. The number of blades depends on the operating conditions and the purpose of the propeller - for developing high speed or creating significant traction force at the moment of launch. A two-bladed propeller with wide blades can also provide sufficient traction. The thrust force, as a rule, increases if the propeller operates in a profiled nozzle ring.
The finished propeller must be balanced, mainly statically, before being mounted on the motor shaft. Otherwise, when it rotates, vibrations occur, which can lead to damage to the entire device. Balancing with an accuracy of 1 g is quite sufficient for amateurs. In addition to balancing the propeller, check its runout relative to the axis of rotation.
General layout
One of the main tasks of the designer is to connect all the units into one functional whole. When designing a vehicle, the designer is obliged to provide space within the hull for the crew and placement of lifting and propulsion system units. It is important to use already known AVP designs as a prototype. In Fig. Figures 14 and 15 show the design diagrams of two typical amateur-built WUAs.In most WUAs, the body is a load-bearing element, a single structure. It contains the main power plant units, air ducts, control devices and the driver’s cabin. The driver's cabins will be located in the bow or central part of the vehicle, depending on where the supercharger is located - behind the cabin or in front of it. If the AVP is multi-seat, the cabin is usually located in the middle part of the device, which allows it to be operated with a different number of people on board without changing the alignment.
In small amateur AVPs, the driver’s seat is most often open, protected in front by a windshield. The devices have more complex design(tourist type) cabins are covered with a dome made of transparent plastic. To accommodate the necessary equipment and supplies, the volumes available on the sides of the cabin and under the seats are used.
With air engines, the AVP is controlled using either rudders located in the air flow behind the propeller, or guide devices mounted in the air flow flowing from the air-breathing propulsion engine. Control of the device from the driver's seat can be of an aviation type - using handles or steering wheel levers, or as in a car - with a steering wheel and pedals.
There are two main types of fuel systems used in amateur AVPs; with gravity fuel supply and with an automobile or aviation type fuel pump. Fuel system parts, such as valves, filters, oil system with tanks (if a four-stroke engine is used), oil coolers, filters, water cooling system (if it is a water-cooled engine), are usually selected from existing aircraft or automobile parts.
Exhaust gases from the engine are always discharged into the rear of the vehicle and never into the cushion. To reduce the noise that occurs during the operation of WUAs, especially near populated areas, automobile-type mufflers are used.
In the simplest designs, the lower part of the body serves as the chassis. The role of the chassis can be performed by wooden runners (or runners), which take on the load when in contact with the surface. In tourist WUAs, which have a larger mass than sports ones, they are mounted wheeled chassis, which facilitate the movement of WUAs during stops. Typically, two wheels are used, installed on the sides or along the longitudinal axis of the WUA. The wheels have contact with the surface only after the lifting system stops operating, when the AVP touches the surface.
Materials and manufacturing technology
For the production of AVP wooden structure They use high-quality pine lumber, similar to that used in aircraft construction, as well as birch plywood, ash, beech and linden wood. For gluing wood, waterproof glue with high physical and mechanical properties is used.For flexible fencing, technical fabrics are predominantly used; they must be extremely durable, resistant to weathering and humidity, as well as friction. In Poland, fire-resistant fabric coated with plastic-like polyvinyl chloride is most often used.
It is important to perform the cutting correctly and ensure careful connection of the panels to each other, as well as their fastening to the device. To fasten the shell of the flexible fence to the body, metal strips are used, which, using bolts, evenly press the fabric against the body of the device.
When designing the shape of a flexible air cushion enclosure, one should not forget about Pascal's law, which states: air pressure spreads in all directions with the same force. Therefore, the shell of a flexible fence in an inflated state should have the shape of a cylinder or a sphere or a combination of both.
Housing design and strength
Forces from the cargo transported by the device, the weight of the power plant mechanisms, etc. are transferred to the body of the AVP, and also loads from external forces, impacts of the bottom on the wave and pressure in the air cushion. Basic structure The hull of an amateur AVP is most often a flat pontoon, which is supported by pressure in the air cushion, and in the swimming mode provides buoyancy to the hull. The body is subject to concentrated forces, bending and torque moments from the engines (Fig. 16), as well as gyroscopic moments from the rotating parts of the mechanisms that arise when maneuvering the AVP.The most widely used are two structural types of hulls for amateur AVPs (or combinations thereof):
- truss structure, when the overall strength of the hull is ensured with the help of flat or spatial trusses, and the skin is intended only to retain air in the air path and create buoyancy volumes;
- with load-bearing cladding, when the overall strength of the hull is ensured by the outer cladding, working in conjunction with the longitudinal and transverse structure.
The design of the cabin and its glazing must allow the driver and passengers to quickly exit the cabin, especially in the event of an accident or fire. The location of the windows should provide the driver with a good view: the observation line should be within the range of 15° down to 45° up from horizontal line; lateral visibility must be at least 90° on each side.
Power transmission to propeller and supercharger
The easiest ones for amateur production are V-belt and chain drives. However, a chain drive is used only to drive propellers or superchargers whose rotation axes are located horizontally, and even then only if it is possible to select the appropriate motorcycle sprockets, since their manufacture is quite difficult.When V-belt transmission To ensure the durability of the belts, the diameters of the pulleys should be selected as maximum, however, the peripheral speed of the belts should not exceed 25 m/s.
Design of the lifting complex and flexible fencing
The lifting complex consists of a blower unit, air channels, a receiver and a flexible air cushion enclosure (in nozzle circuits). The channels through which air is supplied from the blower to the flexible enclosure must be designed taking into account the requirements of aerodynamics and ensure minimal pressure loss.Flexible fencing for amateur WUAs usually has a simplified shape and design. In Fig. 18 examples are shown design diagrams flexible fencing and a method for checking the shape of the flexible fencing after its installation on the device body. Fences of this type have good elasticity, and due to their rounded shape they do not cling to uneven supporting surfaces.
The calculation of superchargers, both axial and centrifugal, is quite complex and can only be done using special literature.
The steering device, as a rule, consists of a steering wheel or pedals, a system of levers (or cable wiring) connected to a vertical rudder, and sometimes to a horizontal rudder - the elevator.
The control can be made in the form of a car or motorcycle steering wheel. Taking into account, however, the specifics of the design and operation of the AVP as an aircraft, they often use the aircraft 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 through a lever attached to the pipe to the elements of the steering cable wiring and then to the rudder. The forward and backward movements of the handle, made possible by its hinged design, are transmitted through a pusher running inside the tube to the elevator wiring.
With pedal control, regardless of its design, it is necessary to provide the ability to move either the seat or the pedals to adjust in accordance with individual characteristics driver. Levers are most often made of duralumin, transmission pipes are attached to the body using 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 design of a rudder in the case of its placement in the air flow thrown by the propeller is shown in Fig. 20.
The rudders can be either completely rotary, or consist of two parts - a fixed part (stabilizer) and a rotary one (rudder blade) with different percentage ratios of the chords of these parts. The cross-sectional profiles of any type of steering wheel must be symmetrical. The steering stabilizer is usually fixedly mounted on the body; The main load-bearing element of the stabilizer is the spar, to which the rudder blade is hinged. Elevators, very rarely found in amateur AVPs, are designed according to the same principles and are sometimes even exactly the same as rudders.
The structural elements that transmit movement from the controls to the steering wheels and throttle valves of engines usually consist of levers, rods, cables, etc. With the help of rods, as a rule, forces are transmitted in both directions, while cables work only for traction. Most often used in amateur WUAs combined systems- with cables and pushers.
From the editor
Hovercraft are increasingly attracting the attention of lovers of water-motor sports and tourism. With relatively little power input, they allow you to achieve high speeds; shallow and impassable rivers are accessible to them; A hovercraft can hover both above the ground and over the ice.For the first time, we introduced readers to the issues of designing small hovercraft back in the 4th issue (1965), publishing an article by Yu. A. Budnitsky “Soaring ships”. A brief outline of the development of foreign hovercrafts was published, including a description of a number of sports and recreational modern 1- and 2-seater hovercrafts. The editors introduced the experience of independently building such a device by Riga resident O. O. Petersons in. The publication about this amateur design aroused particularly great interest among our readers. Many of them wanted to build the same amphibian and asked for the necessary literature.
This year, the Sudostroenie publishing house is releasing a book by Polish engineer Jerzy Ben, “Models and Amateur Hovercraft.” In it you will find a presentation of the basic theory of the formation of an air cushion and the mechanics of movement on it. The author provides the calculated ratios that are necessary when independent design the simplest SVP, introduces trends and development prospects of this type ships. The book provides many examples of the designs of amateur hovercraft (AHVs) built in the UK, Canada, USA, France, and Poland. The book is addressed to a wide range of fans of self-building ships, ship modellers, and watercraft enthusiasts. Its text is richly illustrated with drawings, drawings and photographs.
The magazine publishes an abbreviated translation of a chapter from this book.
The four most popular foreign hovercrafts
American hovercraft "Airskat-240"
Double sports hovercraft with a transverse symmetrical arrangement of seats. Mechanical installation - car. dv. Volkswagen with a power of 38 kW, driving an axial four-blade supercharger and a two-blade propeller in a ring. The hovercraft is controlled along the course using a lever connected to a system of rudders located in the flow behind the propeller. Electrical equipment 12 V. Engine start - electric starter. Dimensions of the device are 4.4x1.98x1.42 m. Air cushion area - 7.8 m 2; propeller diameter 1.16 m, total weight - 463 kg, maximum speed on water 64 km/h.American hovercraft from Skimmers Inc.
A kind of single-seat hovercraft scooter. The housing design is based on the idea of using car camera. Two-cylinder motorcycle engine with a power of 4.4 kW. Dimensions of the device are 2.9x1.8x0.9 m. Air cushion area - 4.0 m 2; total weight - 181 kg. Maximum speed - 29 km/h.English hovercraft "Air Ryder"
This two-seater sports apparatus is one of the most popular among amateur boatbuilders. The axial supercharger is driven by the motorcycle engine. working volume 250 cm3. 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 is electric starter. The device has dimensions of 3.81x1.98x2.23 m; ground clearance 0.03 m; rise 0.077 m; pillow area 6.5 m2; empty weight 181 kg. Develops a speed of 57 km/h on water, 80 km/h on land; overcomes slopes up to 15°.Table 1 shows the data for a single-seat modification of the device.
English SVP "Hovercat"
Light tourist boat for five to six people. There are two modifications: “MK-1” and “MK-2”. A centrifugal supercharger with a diameter of 1.1 m is driven by the vehicle. dv. Volkswagen has a displacement of 1584 cm 3 and consumes power of 34 kW at 3600 rpm.In the MK-1 modification, movement is carried out using a propeller with a diameter of 1.98 m, driven by a second engine of the same type.
In the MK-2 modification, a car is used for horizontal traction. dv. Porsche 912 with a volume of 1582 cm 3 and a power of 67 kW. The apparatus is controlled using aerodynamic rudders placed in the flow behind the propeller. Electrical equipment with a voltage of 12 V. Dimensions of the device 8.28 x 3.93 x 2.23 m. Air cushion area 32 m 2, total weight of the device 2040 kg, speed of modification "MK-1" - 47 km/h, "MK-2" - 55 km/h
Notes
1. A simplified method for selecting a propeller according to known value resistance, rotational speed and translational speed are given in.2. Calculations of V-belt and chain drives can be performed using standards generally accepted in domestic mechanical engineering.
The quality of the road network in our country leaves much to be desired. The construction of transport infrastructure in some directions is inappropriate for economic reasons. Vehicles operating on different physical principles can cope perfectly with the movement of people and goods in such areas. It is impossible to build full-size hovercraft with your own hands in makeshift conditions, but large-scale models are quite possible.
Vehicles of this type are capable of moving on any relatively flat surface. It could be an open field, a pond, or even a swamp. It is worth noting that on such surfaces, unsuitable for other vehicles, the hovercraft is capable of developing a fairly high speed. The main disadvantage of such transport is the need for large energy costs to create an air cushion and, as a consequence, high consumption fuel.
Physical principles of hovercraft operation
The high cross-country ability of vehicles of this type is ensured by the low specific pressure that it exerts on the surface. This is explained quite simply: the contact area of the vehicle is equal to or even greater than the area of the vehicle itself. In encyclopedic dictionaries, hovercraft are defined as vessels with a dynamically created support thrust. 
Large and small hovercraft hover above the surface at a height of 100 to 150 mm. Excessive air pressure is created in a special device under the housing. The machine breaks away from the support and loses mechanical contact with it, as a result of which the resistance to movement becomes minimal. The main energy costs go to maintaining the air cushion and accelerating the device in the horizontal plane.
Drafting a project: choosing a working scheme
To produce a working hovercraft mock-up, it is necessary to select a body design that is effective for the given conditions. Drawings of hovercraft can be found on specialized resources where patents with detailed description different schemes and ways to implement them. Practice shows that one of the most good options for media such as water and solid soil, it is chamber method formation of an air cushion. 
Our model will implement a classic two-engine design with one pumping power drive and one pushing one. Small-sized hovercraft made by hand are, in fact, toy copies of large devices. However, they clearly demonstrate the advantages of using such vehicles over others.
Vessel hull manufacturing
When choosing a material for a ship's hull, the main criteria are ease of processing and low specific gravity. Homemade hovercraft are classified as amphibious, which means that in the event of an unauthorized stop, flooding will not occur. The hull of the vessel is cut out of plywood (4 mm thick) according to a pre-prepared pattern. A jigsaw is used to perform this operation. 
A homemade hovercraft has superstructures that are best made from polystyrene foam to reduce weight. To give them a greater external resemblance to the original, the parts are glued with penoplex and painted on the outside. The cabin windows are made of transparent plastic, and the remaining parts are cut out of polymers and bent from wire. Maximum detail is the key to resemblance to the prototype.
Air chamber dressing
When making the skirt, dense fabric made of polymer waterproof fiber is used. Cutting is carried out according to the drawing. If you do not have experience transferring sketches onto paper by hand, you can print them on a large-format printer on thick paper and then cut them out with regular scissors. The prepared parts are sewn together, the seams should be double and tight.
Self-made hovercraft rest their hull on the ground before turning on the supercharger engine. The skirt is partially wrinkled and placed underneath. The parts are glued together with waterproof glue, and the joint is closed by the superstructure body. This connection ensures high reliability and makes the installation joints invisible. From polymer materials Other external parts are also made: the propeller diffuser guard and the like.
Power point
The power plant contains two engines: a supercharger and a propulsion engine. The model uses brushless electric motors and two-blade propellers. They are remotely controlled using a special regulator. The power source for the power plant is two batteries with a total capacity of 3000 mAh. Their charge is enough for half an hour of using the model.
Homemade hovercraft are controlled remotely via radio. All system components - radio transmitter, receiver, servos - are factory-made. They are installed, connected and tested in accordance with the instructions. After turning on the power, a test run of the engines is performed with a gradual increase in power until a stable air cushion is formed.
SVP model management
Hovercraft, made by hand, as noted above, have remote control via VHF channel. In practice, it looks like this: the owner has a radio transmitter in his hands. The engines are started by pressing the corresponding button. Speed control and change of direction of movement are made by joystick. The machine is easy to maneuver and maintains its course quite accurately.
Tests have shown that the hovercraft confidently moves on a relatively flat surface: on water and on land with equal ease. The toy will become a favorite entertainment for a child aged 7-8 years with sufficiently developed fine motor skills of the fingers.
What is a hovercraft?
Technical data of the device
What materials are needed?
How to make a case?
What engine do you need?
DIY hovercraft
A hovercraft is a vehicle that can travel both on water and on land. It’s not at all difficult to make such a vehicle with your own hands.
What is a hovercraft?
This is a device that combines the functions of a car and a boat. The result was a hovercraft (hovercraft), which has unique cross-country characteristics, without loss of speed when moving through water due to the fact that the hull of the vessel does not move through the water, but above its surface. This made it possible to move through the water much faster, due to the fact that the friction force of the water masses does not provide any resistance.
Although the hovercraft has a number of advantages, its field of application is not so widespread. The fact is that this device cannot move on any surface without any problems. It requires soft sandy or soil soil, without stones or other obstacles. The presence of asphalt and other hard bases can render the bottom of the vessel, which creates an air cushion when moving, unusable. In this regard, “hovercrafts” are used where you need to sail more and drive less. If on the contrary, then it is better to use the services of an amphibious vehicle with wheels. Ideal conditions their application is in difficult to pass swampy places where, except for a hovercraft (hovercraft), no other vehicle can pass. Therefore, hovercrafts have not become so widespread, although similar transport is used by rescuers in some countries, such as Canada, for example. According to some reports, SVPs are in service with NATO countries.
How to purchase such a vehicle or how to make it yourself?
Hovercraft is an expensive type of transport, the average price of which reaches 700 thousand rubles. Scooter-type transport costs 10 times less. But at the same time, one should take into account the fact that factory-made vehicles are always of better quality compared to home-made ones. And the reliability of the vehicle is higher. In addition, factory models are accompanied by factory warranties, which cannot be said about structures assembled in garages.
Factory models have always been focused on a narrowly professional area related to either fishing, hunting, or special services. As for homemade hovercraft, they are extremely rare and there are reasons for this.
These reasons include:
- Enough high cost, as well as expensive maintenance. The main elements of the device wear out quickly, which requires their replacement. Moreover, each such repair will cost a pretty penny. Only a rich person will afford to buy such a device, and even then he will think again whether it is worth getting involved with it. The fact is that such workshops are as rare as the vehicle itself. Therefore, it is more profitable to purchase a jet ski or ATV for moving on water.
- The operating product creates a lot of noise, so you can only move around with headphones.
- When moving against the wind, the speed drops significantly and fuel consumption increases significantly. Therefore, homemade hovercraft is more of a demonstration of one’s professional abilities. You not only need to be able to operate a vessel, but also be able to repair it, without significant expenditure of funds.
DIY SVP manufacturing process
Firstly, assembling a good hovercraft at home is not so easy. To do this you need to have the opportunity, desire and professional skills. A technical education wouldn't hurt either. If the last condition is absent, then it is better to refuse to build the apparatus, otherwise you may crash on it during the first test.
All work begins with sketches, which are then transformed into working drawings. When creating sketches, you should remember that this device should be as streamlined as possible so as not to create unnecessary resistance when moving. At this stage, one should take into account the fact that this is practically an aerial vehicle, although it is very low to the surface of the earth. If all conditions are taken into account, then you can begin to develop drawings.
The figure shows a sketch of the SVP of the Canadian Rescue Service.
Technical data of the device
As a rule, all hovercraft are capable of achieving decent speeds that no boat can achieve. This is when you consider that the boat and hovercraft have the same mass and engine power.
At the same time, the proposed model of a single-seat hovercraft is designed for a pilot weighing from 100 to 120 kilograms.
As for driving a vehicle, it is quite specific and does not fit in with driving a regular motor boat. The specificity is associated not only with the presence of high speed, but also with the method of movement.
The main nuance is related to the fact that when turning, especially at high speeds, the ship skids strongly. To minimize this factor, you need to lean to the side when turning. But these are short-term difficulties. Over time, the control technique is mastered and the hovercraft can demonstrate miracles of maneuverability.
What materials are needed?
Basically you will need plywood, foam plastic and a special construction kit from Universal Hovercraft, which includes everything you need to assemble the vehicle yourself. The kit includes insulation, screws, air cushion fabric, special glue and more. This set can be ordered on the official website by paying 500 bucks for it. The kit also includes several variants of drawings for assembling the SVP apparatus.
How to make a case?
Since the drawings are already available, the shape of the vessel should be linked to the finished drawing. But if you have a technical background, then, most likely, a ship will be built that is not similar to any of the options.
The bottom of the vessel is made of foam plastic, 5-7 cm thick. If you need a device to transport more than one passenger, then another sheet of foam plastic is attached to the bottom. After this, two holes are made in the bottom: one is intended for air flow, and the second is to provide the pillow with air. Holes are cut using an electric jigsaw.
At the next stage, the lower part of the vehicle is sealed from moisture. To do this, take fiberglass and glue it to the foam using epoxy glue. At the same time, unevenness may form on the surface and air bubbles. To get rid of them, the surface is covered with polyethylene and a blanket on top. Then, another layer of film is placed on the blanket, after which it is fixed to the base with tape. It is better to blow the air out of this “sandwich” using a vacuum cleaner. After 2 or 3 hours, the epoxy resin will harden and the bottom will be ready for further work.
The top of the body can have any shape, but take into account the laws of aerodynamics. After this, they begin to attach the pillow. The most important thing is that air enters it without loss.
The pipe for the motor should be made of styrofoam. The main thing here is to guess the size: if the pipe is too large, then you will not get the traction that is necessary to lift the hovercraft. Then you should pay attention to mounting the motor. The motor holder is a kind of stool consisting of 3 legs attached to the bottom. The engine is installed on top of this “stool”.
What engine do you need?
There are two options: the first option is to use an engine from Universal Hovercraft or use any suitable engine. This could be a chainsaw engine, the power of which is quite enough for a homemade device. If you want to get a more powerful device, then you should take a more powerful engine.
It is advisable to use factory-made blades (those included in the kit), since they require careful balancing and this is quite difficult to do at home. If this is not done, the unbalanced blades will destroy the entire engine.
How reliable can a hovercraft be?
As practice shows, factory hovercraft (hovercraft) have to be repaired about once every six months. But these problems are insignificant and do not require serious costs. Basically, the airbag and air supply system fail. In fact, the likelihood is that homemade device will fall apart during operation, it is very small if the “hovercraft” is assembled competently and correctly. For this to happen, you need to run into some obstacle at high speed. Despite this, the air cushion is still able to protect the device from serious damage.
Rescuers working on similar devices in Canada repair them quickly and competently. As for the pillow, it can actually be repaired in a regular garage.
Such a model will be reliable if:
- The materials and parts used were of good quality.
- The device has a new engine installed.
- All connections and fastenings are made reliably.
- The manufacturer has all the necessary skills.
If the SVP is made as a toy for a child, then in this case It is desirable that data from a good designer be present. Although this is not an indicator for putting children behind the wheel of this vehicle. This is not a car or a boat. Operating a hovercraft is not as easy as it seems.
Taking this factor into account, you need to immediately begin manufacturing a two-seater version in order to control the actions of the one who will sit behind the wheel.
How to build a land hovercraft
We owe the final design, as well as the informal name of our craft, to a colleague from the Vedomosti newspaper. Seeing one of the test “take-offs” in the publishing house parking lot, she exclaimed: “Yes, this is Baba Yaga’s stupa!” This comparison made us incredibly happy: after all, we were just looking for a way to equip our hovercraft with a rudder and a brake, and the way was found by itself - we gave the pilot a broom!
This looks like one of the silliest crafts we've ever made. But, if you think about it, it is a very spectacular physical experiment: it turns out that a weak air flow from a hand-held blower, designed to sweep weightless dead leaves from paths, is capable of lifting a person above the ground and easily moving him in space. Despite its very impressive appearance, building such a boat is as easy as shelling pears: if you strictly follow the instructions, it will only require a couple of hours of dust-free work.
Helicopter and puck
Contrary to popular belief, the boat does not rest on a 10-centimeter layer compressed air, otherwise it would already be a helicopter. The air cushion is something like air mattress. Polyethylene film, which covers the bottom of the apparatus, is filled with air, stretched and turns into something like an inflatable ring.
The film adheres very tightly to the road surface, forming a wide contact patch (almost over the entire area of the bottom) with a hole in the center. Air under pressure comes from this hole. Over the entire contact area between the film and the road, a thin layer of air is formed, along which the device easily glides in any direction. Thanks to the inflatable skirt, even a small amount of air is enough for a good glide, so our stupa is much more like an air hockey puck than a helicopter.
Wind under the skirt
We usually do not publish exact drawings in the “master class” section and strongly recommend that readers use their creative imagination in the process, experimenting with the design as much as possible. But this is not the case. Several attempts to slightly deviate from the popular recipe cost the editor a couple of days of extra work. Don't repeat our mistakes - follow the instructions carefully.
The boat should be round, like a flying saucer. A vessel resting on a thin layer of air requires perfect balance: with the slightest defect in weight distribution, all the air will come out from the underloaded side, and the heavier side will fall with its entire weight on the ground. The symmetrical round shape of the bottom will help the pilot easily find balance by slightly changing his body position.
To make the bottom, take 12 mm plywood, use a rope and a marker to draw a circle with a diameter of 120 cm and cut out the part with an electric jigsaw. The skirt is made from a polyethylene shower curtain. Choosing a curtain is perhaps the most important stage at which the fate of the future craft is decided. Polyethylene should be as thick as possible, but strictly uniform and in no case reinforced with fabric or decorative tapes. Oilcloth, tarpaulin and other airtight fabrics are not suitable for building a hovercraft.
In pursuit of the strength of the skirt, we made our first mistake: the poorly stretching oilcloth tablecloth was unable to press tightly to the road and form a wide contact patch. The area of the small “spot” was not enough to make the heavy car slide.
Leaving an allowance to let more air in under a tight skirt is not an option. When inflated, such a pillow forms folds that will release air and prevent the formation of a uniform film. But polyethylene tightly pressed to the bottom, stretching when air is pumped, forms a perfectly smooth bubble that tightly fits any unevenness in the road.
Scotch tape is the head of everything
Making a skirt is easy. It is necessary to spread polyethylene on a workbench, cover the top with a round piece of plywood with pre- drilled hole for air supply and carefully secure the skirt with a furniture stapler. Even the simplest mechanical (not electric) stapler with 8 mm staples will cope with the task.
Reinforced tape is a very important element of the skirt. It strengthens it where necessary, while maintaining the elasticity of other areas. Please pay Special attention to reinforce polyethylene under the central “button” and in the area of the air supply holes. Apply the tape with a 50% overlap and in two layers. The polyethylene must be clean, otherwise the tape may come off.
Insufficient reinforcement in the central area caused a funny accident. The skirt tore at the “button” area, and our pillow turned from a “donut” into a semicircular bubble. The pilot, with his eyes widened in surprise, rose a good half meter above the ground and after a couple of moments fell down - the skirt finally burst and let out all the air. It was this incident that led us to the mistaken idea of using oilcloth instead of a shower curtain.
Another misconception that befell us during the construction of the boat was the belief that there is never too much power. We sourced a large Hitachi RB65EF 65cc backpack blower. This beast of a machine has one significant advantage: it is equipped with a corrugated hose, with which it is very easy to connect the fan to the skirt. But the power of 2.9 kW is clearly too much. The polyethylene skirt must be given exactly the amount of air that will be sufficient to lift the car 5-10 cm above the ground. If you overdo it with gas, the polyethylene will not withstand the pressure and will tear. This is exactly what happened with our first car. So rest assured that if you have any kind of leaf blower at your disposal, it will be suitable for the project.
Full speed ahead!
Typically, hovercraft have at least two propellers: one propulsion propeller, which gives the vehicle forward motion, and one fan, which forces air under the skirt. How will our “flying saucer” move forward, and can we get by with just one blower?
This question tormented us right up until the first successful tests. It turned out that the skirt glides so well over the surface that even the slightest change in balance is enough for the device to move by itself in one direction or another. For this reason, you only need to install the chair on the car while it is moving, in order to properly balance the car, and only then screw the legs to the bottom.
We tried the second blower as a propulsion engine, but the result was not impressive: the narrow nozzle produces a fast flow, but the volume of air passing through it is not enough to create even the slightest noticeable jet thrust. What you really need when driving is a brake. Baba Yaga's broom is ideal for this role.
Called yourself a ship - get into the water
Unfortunately, our editorial office, and along with it the workshop, are located in the concrete jungle, far from even the most modest bodies of water. Therefore, we could not launch our device into the water. But theoretically everything should work! If building a boat becomes a summer activity for you on a hot summer day, test it for seaworthiness and share with us a story about your success. Of course, you need to take the boat out onto the water from a gently sloping bank at cruising throttle, with the skirt fully inflated. There is no way to allow it to sink - immersion in water means the inevitable death of the blower from water hammer.
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The prototype of the presented amphibious vehicle was an air-cushion vehicle (AVP) called “Aerojeep”, a publication about which was in the magazine. Like the previous device, the new machine is single-engine, single-propeller with distributed air flow. This model is also a three-seater, with the pilot and passengers arranged in a T-shape: the pilot is in the front in the middle, and the passengers are on the sides, in the back. Although nothing prevents the fourth passenger from sitting behind the driver’s back - the length of the seat and the power of the propeller engine are quite enough.
New car, except improved ones technical characteristics, has a number design features and even innovations that increase its operational reliability and survivability - after all, an amphibian is a waterfowl. And I call it a “bird” because it still moves through the air both above water and above land.
Structurally, the new machine consists of four main parts: a fiberglass body, a pneumatic cylinder, a flexible fence (skirt) and a propeller unit.
When talking about a new car, you will inevitably have to repeat yourself - after all, the designs are largely similar.
Amphibious Corps identical to the prototype both in size and design - fiberglass, double, three-dimensional, consisting of inner and outer shells. It is worth noting here that the holes in the inner shell in the new device are now located not at the upper edge of the sides, but approximately in the middle between it and the bottom edge, which ensures a faster and more stable creation of an air cushion. The holes themselves are now not oblong, but round, with a diameter of 90 mm. There are about 40 of them and they are located evenly along the sides and front.
Each shell was glued into its own matrix (used from the previous design) from two to three layers of fiberglass (and the bottom from four layers) on a polyester binder. Of course, these resins are inferior to vinyl ester and epoxy resins in terms of adhesion, filtration level, shrinkage, and the release of harmful substances upon drying, but they have undeniable advantage in price - 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.
1 – segment (set of 60 pcs.); 2 – balloon; 3 – mooring cleat (3 pcs.); 4 – wind visor; 5 – handrail (2 pcs.); 6 – mesh guard of the propeller; 7 – outer part of the annular channel; 8 – rudder (2 pcs.); 9 – steering wheel control lever; 10 – hatch in the tunnel for access to the fuel tank and battery; 11 – pilot’s seat; 12 – passenger sofa; 13 – engine casing; 14 – oar (2 pcs.); 15 – muffler; 16 – filler (foam); 17 – inner part of the annular channel; 18 – running light; 19 – propeller; 20 – propeller hub; 21 – drive toothed belt; 22 – attachment point for the cylinder to the body; 23 – attachment point of the segment to the body; 24 – engine on motor mount; 25 – inner shell of the body; 26 – filler (foam); 27 – outer shell of the housing; 28 – dividing panel for forced air flow
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 housing shells - about 4 mm). Before baking elements with work surface the matrix was carefully removed all roughness and burrs, and it was covered three times with wax diluted in turpentine and polished. After this, it was applied to the surface with a spray (or roller) thin layer(up to 0.5 mm) red gelcoat (colored varnish).
After it dried, the process of gluing the shell began using the following technology. First, using a roller, the wax surface of the matrix and one side of the glass mat (with smaller pores) are coated with resin, and then the mat is placed on the matrix and rolled until the air is completely removed from under the layer (if necessary, you can make a small slot in the mat). In the same way, subsequent layers of glass mats are laid to the required thickness (3-4 mm), with the installation, where necessary, of embedded parts (metal and wood). Excess flaps along the edges were trimmed off when gluing “wet”.
A - outer shell;
b – inner shell;
1 – ski (tree);
2 – sub-motor plate (wood)
After making the outer and inner shells separately, they were joined, fastened with clamps and self-tapping screws, and then glued along the perimeter with strips of coated polyester resin the same glass mat 40 -50 mm wide from which the shells themselves were made. After attaching the shells to the edge with petal rivets, a vertical side strip made of 2 mm duralumin strip with a width of at least 35 mm was attached around the perimeter.
Additionally, pieces of resin-impregnated fiberglass should be carefully glued to all corners and places where fasteners are screwed in. The outer shell is covered on top with gelcoat - a polyester resin with acrylic additives and wax, which gives shine and water resistance.
It is worth noting that smaller elements were glued using the same technology (the outer and inner shells were made): the inner and outer shells of the diffuser, steering wheels, engine casing, wind deflector, tunnel and driver's seat. A 12.5 liter gas tank (industrial from Italy) is inserted inside the housing, into the console, before fastening the lower and upper parts of the housings.
inner shell of the housing with air outlets to create an air cushion; above the holes there is a row of cable clips for hooking the ends of the scarf of the skirt segment; two wooden skis glued to the bottom
For those who are just starting to work with fiberglass, I recommend starting to build a boat with these small elements. The total weight of the fiberglass body including skis and strip of aluminum alloy, diffuser and rudders - from 80 to 95 kg.
The space between the shells serves as an air duct around the perimeter of the apparatus from the stern on both sides to the bow. The top and bottom of this space are filled construction foam, which provides optimal cross section air channels and additional buoyancy (and, accordingly, survivability) of the device. The pieces of foam plastic were glued together with the same polyester binder, and they were glued to the shells with strips of fiberglass, also impregnated with resin. Next, from the air channels, the air comes out through evenly spaced holes with a diameter of 90 mm in the outer shell, “rests” on the skirt segments and creates an air cushion under the device.
To protect against damage, a pair of longitudinal skis made of wooden blocks are glued to the bottom of the outer shell of the hull from the outside, and an under-engine wooden plate is glued to the aft part of the cockpit (that is, from the inside).
Balloon. New model The hovercraft has almost twice the displacement (350 - 370 kg) than the previous one. This was achieved by installing an inflatable balloon between the body and the segments of the flexible fence (skirt). The cylinder is glued from a lavsan-based PVC film material Uipuriap, produced in Finland, with a density of 750 g/m 2 according to the shape of the body in plan. The material has been tested on large industrial hovercraft such as Chius, Pegasus, and Mars. To increase survivability, the cylinder can consist of several compartments (in this case, three, each with its own filling valve). The compartments, in turn, can be divided in half lengthwise by longitudinal partitions (but this version of them is still only in the design). With this design, a broken compartment (or even two) will allow you to continue moving along the route, and even more so to get to the shore for repairs. For economical cutting of material, the cylinder is divided into four sections: a bow section and two feed sections. Each section, in turn, is glued together from two parts (halves) of the shell: lower and upper - their patterns are mirrored. In this version of the cylinder, the compartments and sections do not match.
a – outer shell; b – inner shell;
1 – bow section; 2 – side section (2 pcs.); 3 – aft section; 4 – partition (3 pcs.); 5 – valves (3 pcs.); 6 – lyktros; 7 – apron
A “liktros” is glued to the top of the cylinder - a strip of Vinyplan 6545 “Arctic” material folded in half, with a braided nylon cord inserted along the fold, impregnated with “900I” glue. “Liktros” is applied to the side bar, and with the help of plastic bolts the cylinder is attached to an aluminum strip fixed to the body. The same strip (only without the attached cord) is glued to the cylinder and from the bottom in front (“at half past seven”), the so-called “apron” - to which the upper parts of the segments (tongues) of the flexible fence are tied. Later, a rubber bumper bumper was glued to the front of the cylinder.
Soft elastic fencing"Aerojipa" (skirt) consists of separate but identical elements - segments, cut and sewn from dense light fabric or film material. It is desirable that the fabric is water-repellent, does not harden in the cold and does not allow air to pass through.
I again used Vinyplan 4126 material, only with a lower density (240 g/m2), but domestic percale-type fabric is quite suitable.
The segments are slightly smaller in size than on the “balloonless” model. The pattern of the segment is simple, and you can sew it yourself, even by hand, or weld it with currents high frequency(TVS).
The segments are tied with the tongue of the lid to the seal of the balloon (two - at one end, while the knots are located inside under the skirt) along the entire perimeter of the Aeroamphibian. The two lower corners of the segment, using nylon construction clamps, are suspended freely from a steel cable with a diameter of 2 - 2.5 mm, encircling the lower part of the inner shell of the body. In total, the skirt accommodates up to 60 segments. A steel cable with a diameter of 2.5 mm is attached to the body using clips, which in turn are attracted to the inner shell by leaf rivets.
1 – scarf (material “Viniplan 4126”); 2 – tongue (material “Viniplan 4126”); 3 – overlay (Arctic fabric)
This fastening of the skirt segments does not significantly exceed the time required to replace a failed element of the flexible fence, compared to the previous design, when each was fastened separately. But as practice has shown, the skirt is operational even when up to 10% of the segments fail and their frequent replacement is not required.
1 – outer shell of the housing; 2 – inner shell of the body; 3 - overlay (fiberglass) 4 - strip (duralumin, strip 30x2); 5 – self-tapping screw; 6 – cylinder line; 7 – plastic bolt; 8 – balloon; 9 – cylinder apron; 10 – segment; 11 – lacing; 12 – clip; 13-clamp (plastic); 14-cable d2.5; 15-extension rivet; 16-eyelet
The propeller installation consists of an engine, a six-bladed propeller (fan) and a transmission.
Engine– RMZ-500 (analogue of Rotax 503) from the Taiga snowmobile. Produced by Russian Mechanics OJSC under license from the Austrian company Rotax. The engine is two-stroke, with a petal intake valve and forced air cooling. It has proven itself to be reliable, quite powerful (about 50 hp) and not heavy (about 37 kg), and most importantly, a relatively inexpensive unit. Fuel - AI-92 gasoline mixed with oil for two-stroke engines (for example, domestic MGD-14M). Average fuel consumption is 9 – 10 l/h. The engine is mounted in the rear part of the vehicle, on a motor mount attached to the bottom of the hull (or rather, to the sub-engine wooden slab). The motorama has become taller. This is done for the convenience of cleaning the aft part of the cockpit from snow and ice that gets there through the sides and accumulates there and freezes when stopped.
1 – engine output shaft; 2 – driving toothed pulley (32 teeth); 3 – toothed belt; 4 – driven toothed pulley; 5 – M20 nut for axle fastening; 6 – spacer bushings (3 pcs.); 7 – bearing (2 pcs.); 8 – axis; 9 – screw bushing; 10 – rear strut support; 11 – front supra-engine support; 12 - front braced biped support (not shown in the drawing, see photo); 13 – outer cheek; 14 – inner cheek
The propeller is six-bladed, fixed pitch, with a diameter of 900 mm. (There was an attempt to install two five-bladed coaxial propellers, but it was unsuccessful). The screw bushing is made of cast aluminum. The blades are fiberglass, coated with gelcoat. The axis of the propeller hub was lengthened, although the same 6304 bearings remained on it. The axis was mounted on a stand above the engine and secured here with two spacers: a two-beam one in the front and a three-beam one in the rear. There is a mesh guard in front of the propeller, and rudder feathers at the rear.
The transmission of torque (rotation) from the engine output shaft to the propeller hub is carried out through a toothed belt with a gear ratio of 1:2.25 (the drive pulley has 32 teeth, and the driven pulley has 72).
The air flow from the propeller is distributed by a partition in the annular channel into two unequal parts (approximately 1:3). A smaller part of it goes under the bottom of the hull to create an air cushion, and a larger part goes to generate propulsive force (traction) for movement. A few words about the features of driving an amphibian, specifically about the start of movement. When the engine is idling, the device remains motionless. As the number of its revolutions increases, the amphibian first rises above the supporting surface, and then begins to move forward at revolutions from 3200 - 3500 per minute. At this moment, it is important, especially when starting from the ground, that the pilot first lifts the rear part of the device: then the rear segments will not catch on anything, and the front segments will slip over uneven surfaces and obstacles.
1 – base (steel sheet s6, 2 pcs.); 2 – portal stand (steel sheet s4.2 pcs.); 3 – jumper (steel sheet s10, 2 pcs.)
Control of the Aerojeep (changing the direction of movement) is carried out by aerodynamic rudders, hingedly attached to the annular channel. The steering wheel is deflected using a two-arm lever (motorcycle-type steering wheel) through an Italian Bowden cable going to one of the planes of the aerodynamic steering wheel. The other plane is connected to the first rigid rod. A carburetor throttle control lever or a “trigger” from a “Taiga” snowmobile is attached to the left handle of the lever.
1 – steering wheel; 2 – Bowden cable; 3 – unit for fastening the braid to the body (2 pcs.); 4 – Bowden braided cable; 5 – steering panel; 6 – lever; 7 – traction (rocking chair is not shown); 8 – bearing (4 pcs.)
Braking is carried out by “releasing the gas”. In this case, the air cushion disappears and the device rests with its body on the water (or skis on snow or soil) and stops due to friction.
Electrical equipment and instruments. The device is equipped battery, tachometer with hour meter, voltmeter, engine head temperature indicator, halogen headlights, ignition switch button and pin on the steering wheel, etc. The engine is started by an electric starter. It is possible to install any other devices.
The amphibious boat was named “Rybak-360”. It passed sea trials on the Volga: in 2010, at a rally of the Velkhod company in the village of Emmaus near Tver, in Nizhny Novgorod. At the request of Moskomsport, he participated in demonstration performances at the festival dedicated to Navy Day in Moscow on the Rowing Canal.
Aeroamphibian technical data:
Overall dimensions, mm:
length………………………………………………………………………………..3950
width…………………………………………………………………………………..2400
height……………………………………………………………………………….1380
Engine power, hp…………………………………………….52
Weight, kg……………………………………………………………………………….150
Load capacity, kg…………………………………………………………….370
Fuel capacity, l…………………………………………………………….12
Fuel consumption, l/h……………………………………………..9 - 10
Obstacles to be overcome:
rise, hail…………………………………………………………….20
wave, m………………………………………………………………………………0.5
Cruising speed, km/h:
by water……………………………………………………………………………….50
on the ground………………………………………………………………………………54
on ice……………………………………………………………………………….60
M. YAGUBOV Honorary Inventor of Moscow
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