Svp do-it-yourself drawings assembly homemade. DIY amphibious boat
The high speed characteristics and amphibious capabilities of air-cushion vehicles (AHCs), 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, 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 is easy to move both above ground and over water. These are mainly single-seat units with carbureted 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 travel and, accordingly, have luggage racks, large fuel tanks, devices to protect passengers from the 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 characteristics 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 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 also complete operational safety.
Speaking about the running characteristics, they mean the hovering height of the AUA and the ability to overcome obstacles associated with this quality, the maximum speed and throttle response, as well as the 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 terms of 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 fence 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 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 air cushion 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 driving 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 for 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 on 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 is the diameter of the channel, m (if the channel has a non-circular cross-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 channel cross-section and significant changes in the direction of the air flow, as well as losses for air suction 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 supercharger 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 scheme 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 an AHU blower with a flexible air cushion enclosure (nozzle circuit), 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) 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 when power up to 22 kW is required. 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 intensive engine cooling and thorough cleaning of the air entering through the carburetor. It is also important to obtain a unit with a minimum mass, which is the sum of the mass of the engine, the transmission between the supercharger and the engine, and the mass of the supercharger itself.
Depending on the type of ATP, 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 elements of the propeller, 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 the WUA movement, 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 sea water temperature of + 4 ° С it 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 numbers 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 the transfer from the engine to the propeller η p \u003d 0 ,9:
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. At the same time, 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 AVPs, 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 covered with a dome 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, AUA control is carried out using either rudders placed 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 device from the driver's seat can be of an aviation type - with the help of 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 pressure in an air cushion, and in the sailing mode provides the hull buoyancy. The body is acted upon by concentrated forces, bending and torsional 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 to the maximum, 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 a pumping 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 superchargers, both axial and centrifugal, is rather complicated and can only be performed using special 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 an aircraft, the aviation design of controls in the form of a lever or pedals is more often used. 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, 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 - fixed (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 body; the main load-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 the rudders.
Structural elements that transfer movement 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 editorial board
Hovercraft are getting more and more attention of lovers of powerboat sports and tourism. With a relatively low power consumption, they allow you to achieve high speeds; shallow and impassable rivers are accessible to them; the hovercraft can hover both above the ground and above the ice.For the first time, we introduced readers to the issues of designing small hovercraft in the 4th issue (1965), placing the article by Yu. A. Budnitskiy "Soaring ships". In a short sketch 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 Benya "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 "Airscat-240"
A two-seater sports hovercraft with a transverse symmetrical 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 connected to 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 total 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 design of the case 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.English SVP "Air Ryder"
This two-seater sports apparatus is one of the most popular among amateur shipbuilders. An axial supercharger is driven into rotation 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 of 3.81x1.98x2.23 m; clearance of 0.03 m; rise 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 gross 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 translational speed is given in.2. Calculations of V-belt and chain drives can be performed using the standards generally accepted in domestic mechanical engineering.
Once in winter, when I was strolling along the banks of the Daugava, looking at the snow-covered boats, I had a thought - create an all-season vehicle, i.e. an amphibianwhich could also be used in winter.
After much deliberation, my choice fell on a double hovercraft... At first, I had nothing but a great desire to create such a structure. The technical literature available to me summarized the experience of creating only large SVPs, and I could not find any data on small devices for walking and sports purposes, especially since our industry does not produce such SVPs. So, one could only rely on one's own strength and experience (about my amphibious boat based on the motorboat "Yantar" at one time it was reported in "KYa"; see No. 61).
Foreseeing that in the future I might find followers, and if the results are positive, the industry might also be interested in my apparatus, I decided to design it on the basis of well-mastered and commercially available two-stroke engines.
In principle, an air-cushion vehicle experiences significantly less stress than a traditional planing boat hull; this allows the design to be made lighter. At the same time, an additional requirement appears: the body of the apparatus must have low aerodynamic resistance. This must be taken into account when developing a theoretical drawing.
| Basic data of amphibious hovercraft | |
|---|---|
| Length, m | 3,70 |
| Width, m | 1,80 |
| Board height, m | 0,60 |
| Air cushion height, m | 0,30 |
| Hoisting unit power, l. from. | 12 |
| Traction unit power, hp from. | 25 |
| Payload, kg | 150 |
| Total weight, kg | 120 |
| Speed, km / h | 60 |
| Fuel consumption, l / h | 15 |
| Fuel tank capacity, l | 30 |
1 - steering wheel; 2 - instrument panel; 3 - longitudinal seat; 4 - lifting fan; 5 - fan casing; 6 - traction fans; 7 - fan shaft pulley; 8 - engine pulley; 9 - traction motor; 10 - muffler; 11 - control flaps; 12 - fan shaft; 13 - bearings of the fan shaft; 14 - windshield; 15 - flexible fence; 16 - traction fan; 17 - traction fan casing; 18 - lifting motor; 19 - lifting engine muffler; 20 - electric starter; 21 - battery; 22 - fuel tank.
I made the set of the case from spruce slats with a cross section of 50x30 and sheathed it with 4 mm plywood on epoxy glue. I did not use fiberglass, fearing an increase in the weight of the apparatus. To ensure unsinkability, I installed two watertight bulkheads in each of the side compartments, and also filled the compartments with foam.
A twin-engine scheme of the power plant was chosen, i.e. one of the engines works to lift the apparatus, creating an excess pressure (air cushion) under its bottom, and the second provides movement - creates a thrust horizontally. The lifting engine, based on the calculation, was supposed to have a power of 10-15 liters. from. According to the main data, the engine from the Tula-200 scooter turned out to be the most suitable, but since neither the mountings nor the bearings satisfied it for design reasons, a new crankcase had to be cast from an aluminum alloy. This motor drives a 6-blade fan with a diameter of 600 mm. The total weight of the lifting power plant, together with mounts and an electric starter, is about 30 kg.
One of the most difficult stages turned out to be the manufacture of a skirt - a flexible cushion enclosure that wears out quickly during operation. A commercially available canvas cloth 0.75 m wide was used. Due to the complex configuration of the joints, about 14 m of such cloth was required. The strip was cut into pieces with a length equal to the length of the bead, with an allowance for a rather complex shape of the joints. After giving the required shape, the joints were sewn together. The edges of the fabric were attached to the body of the device with 2x20 duralumin strips. To increase wear resistance, I impregnated the installed flexible fence with rubber glue, to which I added aluminum powder, which gives an elegant look. This technology makes it possible to restore a flexible barrier in case of an accident and as it wears out, similar to building up the tread of a car tire. It should be emphasized that making a flexible fence not only takes a lot of time, but requires special care and patience.
The assembly of the hull and the installation of the flexible fence were carried out in the upward position of the keel. Then the hull was cut out and a lifting power unit was installed in the 800x800 shaft. The control system of the installation was brought up, and now the most crucial moment has come; testing it. Will the calculations be justified, will a relatively low-power engine lift such an apparatus?
Already at medium engine speeds, the amphibian rose with me and hovered at a height of about 30 cm from the ground. The lift capacity was enough for a warmed-up engine to lift even four people at full speed. In the very first minutes of these tests, the features of the apparatus began to emerge. After the appropriate centering, he freely moved on an air cushion in any direction, even with a small applied force. The impression was that he was floating on the water surface.
The success of the first test of the lifting unit and the hull as a whole gave me wings. Having secured the windshield, I proceeded to install the traction power plant. At first, it seemed advisable to take advantage of the extensive experience in the construction and operation of snowmobiles and install an engine with a propeller of a relatively large diameter on the aft deck. However, it should be taken into account that with such a "classic" version, the center of gravity of such a small apparatus would significantly increase, which would inevitably affect its driving performance and, most importantly, safety. Therefore, I decided to use two traction motors, completely analogous to the lifting one, and installed them in the aft part of the amphibian, but not on the deck, but along the sides. After I fabricated and assembled a motorcycle-type control drive and installed relatively small-diameter traction propellers (“fans”), the first version of the hovercraft was ready for sea trials.
A special trailer was made to transport the amphibian behind a Zhiguli car, and in the summer of 1978 I loaded my vehicle onto it and delivered it to a meadow near a lake near Riga. This is an exciting moment. Surrounded by friends and curious people, I took the driver's seat, started the lift motor, and my new boat hung over the meadow. Started both traction motors. With an increase in the number of their revolutions, the amphibian began to move through the meadow. And then it became clear that many years of experience in driving a car and motorboat is clearly not enough. All the previous skills will not work. It is necessary to master the methods of controlling a hovercraft, which can spin endlessly in one place, like a whirligig. With increasing speed, the turning radius also increased. Any irregularities in the surface caused the apparatus to turn.
Having mastered the control, I directed the amphibian along the gentle bank to the surface of the lake. Once above the water, the device immediately began to lose speed. The traction motors began to stall one by one, filled with spray that escaped from under the flexible air cushion railing. When passing overgrown areas of the lake, the fans sucked in reeds, the edges of their blades crumbled. When I turned off the engines, and then decided to try to start from the water, nothing came of it: my apparatus was still unable to escape from the “hole” formed by the pillow.
In general, it was a failure. However, the first defeat did not stop me. I came to the conclusion that with the existing characteristics for my air cushion vehicle, the power of the traction unit is insufficient; that is why he could not move forward when starting from the surface of the lake.
During the winter of 1979, I completely redesigned the amphibian, reducing the length of its hull to 3.70 m and its width to 1.80 m. I also designed a completely new propulsion system, completely protected from both splashes and contact with grass and reeds. To simplify the control of the unit and reduce its weight, one traction motor is used instead of two. The powerhead of a 25-horsepower Vikhr-M outboard motor with a completely redesigned cooling system was used. A closed cooling system with a volume of 1.5 liters is filled with antifreeze. The engine torque is transmitted to the “propeller” shaft of the fans located across the apparatus by means of two V-belts. Six-blade fans draw air into the chamber, from which it escapes (simultaneously cooling the engine) behind the stern through a square nozzle equipped with control flaps. From an aerodynamic point of view, such a propulsion system, apparently, is not very perfect, but it is quite reliable, compact and creates a thrust of about 30 kgf, which turned out to be quite sufficient.
In the middle of the summer of 1979, my apparatus was again transported to the same meadow. Having mastered the controls, I directed him to the lake. This time, finding himself above the water, he continued to move without losing speed, as if on the surface of ice. Easily, without hindrance, overcame shallows and reeds; it was especially pleasant to move over the overgrown areas of the lake, there was not even a foggy trace left. On the straight section, one of the owners with the Vikhr-M motor went on a parallel course, but soon fell behind.
The described apparatus aroused particular surprise among fans of ice fishing, when I continued testing the amphibian in winter on ice, which was covered with a layer of snow about 30 cm thick. There was real expanse on the ice! The speed could be increased to maximum. I did not measure it exactly, but the experience of the driver suggests that it was approaching 100 km / h. At the same time, the amphibian freely overcame deep traces from motonart.
A short film was shot and shown by the Riga TV studio, after which I began to receive many requests from those wishing to build such an amphibious vehicle.
Hovercraft is a vehicle capable of traveling both on water and on land. Such a vehicle is not at all difficult to make with your own hands.
This is a device where the functions of a car and a boat are combined. The result is a hovercraft (hovercraft) with unique cross-country characteristics, without loss of speed when moving through the water, due to the fact that the hull of the vessel does not move through the water, but over its surface. This made it possible to move through the water much faster, due to the fact that the frictional 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 can not move on any surface without any problems. It needs a soft sandy or earthy soil, without stones or other obstacles. The presence of asphalt and other hard substrates can damage the bottom of the boat, which creates an air cushion when moving. In this regard, "hovercraft" are used where you need to swim more and ride less. If on the contrary, it is better to use the services of an amphibious vehicle with wheels. The ideal conditions for their use are difficult-to-pass swampy places, where no other transport, apart from a hovercraft (hovercraft), will be able to pass. Therefore, SVPs have not become so widespread, although rescuers from some countries, such as Canada, for example, use such transport. According to some reports, SVPs are in service with NATO countries.
How to purchase such transport or how to make it yourself?
Hovercraft is an expensive form of transport, the average price of which reaches 700 thousand rubles. Transport of the "scooter" type costs 10 times cheaper. But at the same time, one should take into account the fact that factory-made transport is always of better quality compared to homemade products. 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 direction associated either with fishing, or hunting, or with special services. As for home-made SVPs, they are extremely rare and there are reasons for this.
These reasons include:
- Quite high cost as well as expensive service. The main elements of the apparatus wear out quickly, which requires their replacement. Moreover, each such repair will result in a pretty penny. Only a rich person will allow himself to buy such a device, and even then he will think once again whether it is worth contacting him. 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.
- A working product creates a lot of noise, so you can only move around with headphones.
- When moving against the wind, the speed drops significantly and the fuel consumption increases significantly. Therefore, home-made SVPs are rather a demonstration of their professional abilities. The ship not only needs to be able to manage, but also to be able to repair it, without significant expenditure of funds.
DIY SVP manufacturing process
Firstly, it is not so easy to assemble a good SVP at home. To do this, you need to have the ability, desire and professional skills. Technical education will not hurt either. If the last condition is absent, then it is better to refuse to build the apparatus, otherwise you can crash on it at the very first test.
All work begins with sketches, which are then transformed into working drawings. When creating sketches, it should be remembered that this apparatus 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, in practice, an air vehicle, although it is very low to the surface of the earth. If all conditions are taken into account, then you can start developing 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 reaching a decent speed that no boat can reach. This is when you consider that the boat and the 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, in comparison with driving a conventional motor boat, does not fit in any way. The specificity is associated not only with the presence of high speed, but also with the way of movement.
The main nuance is associated with the fact that when cornering, especially at high speeds, the ship skids heavily. To minimize this factor, it is necessary to lean to the side when cornering. But these are short-term difficulties. Over time, the control technique is mastered and on the SVP one can show miracles of maneuverability.
What materials are needed?
Basically, you will need plywood, polystyrene 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 cloth, special glue and more. This set can be ordered on the official website, paying 500 bucks for it. The kit also includes several options for drawings for the assembly of the SVP apparatus.
Since the drawings are already available, the shape of the ship should be tied to the finished drawing. But if you have a technical education, 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 polystyrene, 5-7 cm thick. If you need an apparatus for transporting more than one passenger, then another such sheet of foam is attached from below. After that, two holes are made in the bottom: one is intended for the air flow, and the second is for providing the cushion with air. Holes are cut with an electric jigsaw.
At the next stage, the lower part of the vehicle is sealed from moisture. For this, fiberglass is taken and glued to the foam with epoxy glue. In this case, irregularities and air bubbles can form on the surface. To get rid of them, the surface is covered with polyethylene, and also a blanket on top. Then, another layer of film is laid on the blanket, after which it is fixed to the base with tape. It is better to blow air out of this “sandwich” using a vacuum cleaner. After 2 or 3 hours, the epoxy will harden and the bottom will be ready for further work.
The top of the body can be of any shape, but take into account the laws of aerodynamics. After that, they begin to attach the pillow. The most important thing is that air flows into it without loss.
The motor pipe should be made of styrofoam. The main thing here is to guess with the dimensions: if the pipe is too large, then the thrust that is necessary for lifting the hovercraft will not work. Then you should pay attention to the mount of 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 kind of engine do you need?
There are two options: the first option is to use a Universal Hovercraft engine, or use any suitable engine. It can 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 in the kit), since they require careful balancing and it is quite difficult to do this at home. If this is not done, the unbalanced blades will destroy the entire engine.
How reliable can an SVP be?
As practice shows, factory hovercraft (SVP) have to be repaired about once every six months. But these problems are insignificant and do not require serious costs. Basically, the pillow and the air supply system fail. In fact, the likelihood that a homemade device will fall apart during operation is very small if the "hovercraft" is assembled correctly and correctly. For this to happen, you need to hit an obstacle at high speed. Despite this, the airbag is still able to protect the device from serious damage.
Rescuers working on such devices in Canada repair them quickly and competently. As for the pillow, it is really possible to repair it in a conventional garage.
Such a model will be reliable if:
- The materials and parts used were of proper quality.
- The device has a new engine.
- All connections and fasteners are secure.
- 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 the data of a good designer are present. Although this is not an indicator for putting children behind the wheel of this vehicle. This is not a car or a boat. Managing an SVP is not as easy as it seems.
Taking this factor into account, you need to immediately start making a two-seater version in order to control the actions of the one who will sit behind the wheel.
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 amphibious vehicles on air cushion (WUA), study of their basic structure, comparison of various designs and schemes.
To this end, I visited many Internet sites of enthusiasts and creators of WUAs (including foreign ones), and got acquainted with some of them in person. In the end, for the prototype of the conceived boats() took the English "Hovercraft" ("soaring ship" - as the WUA is called in the UK), built and tested by local enthusiasts.
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 device is on air cushion (I call it "Aerojip") - 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. The boat-AVP consists of three main parts: a propeller-driven installation with a transmission, a fiberglass hull and a "skirt" - a flexible enclosure of the lower part of the hull, so to speak, a "pillowcase" of an air cushion. Aerojip 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 of it. 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 practically 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 deck is a bulkhead as an air flow divider, part of which (supporting flow) is directed into the shaft opening, and the other part is used to create a propulsive thrust force.
All elements of the body: the inner and outer shells, the tunnel and the annular channel, were glued on matrices made 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 the release of harmful substances during 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 shells of the case, 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 the 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". It is recommended to use 2-3 layers of glass mat for the manufacture of the sides of the hull, and up to 4 layers of the bottom.
In this case, it is necessary to glue in addition all the corners, as well as the screw-in points of the fasteners. After the resin has hardened, 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 are attached to the inner shell with strips of glass mat, also oiled with resin. After the outer and inner shells are made 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 body is left until the resin has completely polymerized. A day later, a duralumin strip with a 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.
On top of the runners, one layer of glass mat is glued. 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, rudders, gas tank, engine casing, wind deflector, tunnel and driver's seat.
For those who are just starting to work with fiberglass, I recommend preparing the production boats precisely 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 specialist firms that produce fiberglass boats and boats. Fortunately, there are many of them in Russia, and the costs will be commensurate. However, in the process of self-production, it will be possible to gain the necessary experience and the ability to further model and create various elements and structures from fiberglass. Propeller-driven installation.
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. at 3600 rpm. Its guaranteed service life is 600 thousand hours.
Starting is carried out by an electric starter, from the battery, and the work of the spark plugs is from 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 led out into the lower air stream. Instead of the established Japanese one, you can also use suitable domestic engines, for example, from the Buran, Lynx and others snowmobiles. By the way, engines with a capacity of about 22 liters are quite suitable for a one- or two-seater WUA. from.
The propeller is six-bladed, with a fixed pitch (set on land by the angle of attack) of the blades. 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 it with 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. Soft elastic “Aerodjip” guard (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 quite suitable. 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 is 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 "Aerojip". 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 design of the skirt allows you to easily replace a failed segment, which will take 5-10 minutes. To the point it will be said that the structure turns out to be operational in case of failure of up to 7% of the segments. In total, they can be placed on a skirt up to 60 pieces.
The principle of movement of "Aerojip" is as follows. After starting the engine and idling, the machine 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. Rotation of the "Aerojip" is carried out by two rudders, deflecting the "forward" air flow to the side.
The rudders are controlled from a motorcycle-type double-arm steering column, through a Bowden cable running along the starboard side between the shells to one of the rudders. Another 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 gas handle) is also fixed.
For operation hovercraft it must be registered with the local state inspectorate for small boats (GIMS) and receive a ship ticket. To obtain a certificate for the right to drive a boat, you must also pass a training course on how to operate a small boat. However, even at these courses, there are still far from everywhere instructors for piloting hovercraft.
Therefore, each pilot has to master the management of the WUA independently, literally bit by bit, gaining the appropriate experience.
Aerojip hovercraft: 1-segment (dense fabric); 2-mooring cleat (3 pcs.); 3-wind visor; 4-side segment fastening strip; 5-handle (2 pcs.); 6-propeller guard; 7-ring channel; 8-rudder (2 pcs.); 9-rudder control lever; 10-door access to the gas tank and battery; 11-seat of the pilot; 12-passenger sofa; 13-engine casing; 14-engine; 15-outer shell; 16-filler (foam); 17-inner shell; 18-split panel; 19-propeller; 20-propeller hub; 21-drive toothed belt; 22-node for securing the lower part of the segment
The theoretical drawing of the body: 1 - inner shell; 2-outer sheath
The transmission diagram of the propeller-driven installation: 1 - the output shaft of the engine; 2-drive toothed pulley; 3 - toothed belt; 4-driven toothed pulley; 5 - nut; 6-distance sleeves; 7-bearing; 8-axis; 9-hub; 10-bearing; 11-distance sleeve; 12-support; 13-propeller
Steering column: 1-handle; 2-arm lever; 3-rack; 4-bipod (see photo)
Steering diagram: 1-steering column; 2-Bowden cable, 3-unit for attaching the braid to the body (2 pcs.); 4-bearing (5 pcs.); 5-steering panel (2 pcs.); 6-arm arm-bracket (2 pcs.); 7-tie rod steering panels (see photo)
Flexible fencing segment: 1 - walls; 2-cover with tongue
It all started with the fact that I wanted to do a project and involve my grandson in it. I have a lot of engineering experience behind me, so I did not look for simple projects, and so, one time watching TV, I saw a boat that was moving due to a propeller. "Cool stuff!" - I thought, and began to wool the vastness of the Internet in search of at least some information.
We took the motor from an old lawn mower, and bought the layout itself (it costs $ 30). It is good in that it requires only one motor, while most of these boats require two engines. From the same company, we bought the propeller, propeller hub, air cushion cloth, epoxy, fiberglass, and screws (they all sell in one set). The rest of the materials are pretty commonplace and can be bought at any hardware store. The final budget slightly exceeded $ 600.
Step 1: Materials
Materials you will need: foam, plywood, whale from Universal Hovercraft (~ $ 500). The kit contains all the little things you need to complete the project: blueprint, fiberglass, propeller, propeller hub, air cushion fabric, glue, epoxy, bushings, etc. As I wrote in the description, about $ 600 was spent on all materials.
Step 2: making the wireframe
We take polystyrene (thickness 5 cm) and cut out a rectangle 1.5 by 2 meters from it. These dimensions will provide a buoyancy of ~ 270 kg. If 270 kg seems small, you can take another sheet of the same type and attach it to the bottom. Use a jigsaw to cut two holes: one for the incoming air flow and the other for inflating the pillow.
Step 3: Cover with glass fiber
The lower part of the case must be waterproof, for this we cover it with fiberglass and epoxy. In order for everything to dry properly, without irregularities and roughness, you need to get rid of air bubbles that may arise. For this, you can use an industrial vacuum cleaner. Cover the fiberglass with a layer of film, then cover with a blanket. The cover is needed to prevent the blanket from sticking to the fiber. Then cover the blanket with another layer of film and glue it to the floor with adhesive tape. We make a small cut, put the trunk of the vacuum cleaner into it and turn it on. We leave in this position for a couple of hours, when the procedure is completed, the plastic can be scraped off the fiberglass without any effort, it will not stick to it.
Step 4: The bottom of the case is ready
The lower part of the case 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 detailed, we did not have any problems at this stage. I will only note that the plywood disc is temporary, and will be removed in the following steps.
Step 6: motor holder
The design is not tricky, it is constructed from plywood and bars. Fits exactly in the center of the boat hull. Fastened with glue and screws.
Step 7: propeller
The propeller can be purchased in two types: ready-made and semi-finished product. Ready-made is usually much more expensive, and buying a semi-finished product can save a lot. And so we did.
The closer the propeller blades are to the edges of the air outlet, the more efficiently the latter works. Once you've decided on the clearance, you can grind the blades. As soon as the grinding is completed, it is imperative 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 leveled, but not by cutting the ends, and grinding. Once the balance is found, a couple of coats of paint can be applied to keep it in place. For safety, it is advisable to paint the tips of the blades white.
Step 8: air chamber
The air chamber separates the flow of incoming and outgoing air. Made from 3mm plywood.
Step 9: Installing the air chamber
The air chamber is attached with glue, but you can also use fiberglass, I prefer to always use fiber.
Step 10: guides
The guides are made from 1mm plywood. To give them strength, cover with one layer of fiberglass. It is not very visible in the photo, but you can still notice that both guides are connected together at the bottom with an aluminum bar, this is done so that they work synchronously.
Step 11: shape the boat, add the side panels
The outlines of the shape / contour are made on the bottom, after which a wooden plank is attached to the outlines along the outlines. Plywood of 3 mm bends well, and lies right in the shape we need. Next, we attach and glue a 2 cm beam along the upper edge of the plywood sides. Add the crossbeam and set the handle to act as the rudder. To it we attach the cables extending from the guide blades installed earlier. Now you can paint the boat, preferably several layers. We chose a white color, with it, even with prolonged direct rays of the sun, the body practically does not heat up.
I must say that she swims briskly, and it pleases, but the steering surprised me. At medium speeds, turns are obtained, but at high speed, the boat first skips to the side, and then, by inertia, it moves back for a while. Although I got used to it a little, I realized that tilting the body towards the turn and slightly slowing down the gas can significantly reduce this effect. It is difficult to say the exact speed, because the boat does not have a speedometer, but it feels quite good, and after the boat there is still a decent track and waves.
On the day of the test, the boat was tested by about 10 people, the heaviest weighed about 140 kg, and she withstood it, although he certainly did not manage to squeeze the speed that was available to us. With a weight of up to 100 kg, the boat goes briskly.
Join the club
learn about the most interesting instructions once a week, share yours and participate in the sweepstakes!