Homemade SVP from inflatable boats. DIY amphibious boat
High speed characteristics and amphibious capabilities of vehicles moving on air cushion(WUA), as well as the relative simplicity of their designs, attract the attention of amateur designers. AT last years many small WUAs 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; 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 propulsion systems, and easily moves both above ground and above water. These are predominantly single-seat vehicles with carburetor motorcycle or light automotive engines air cooling.
Tourist WUAs are more complex in design. Usually they are two- or four-seater, designed for relatively long journeys and, accordingly, have trunks, large-capacity fuel tanks, and devices to protect passengers from bad weather.
For economic purposes, small platforms are used, adapted to transport mainly agricultural goods over rough and swampy terrain.
Main characteristics
Amateur WUAs are characterized by the main dimensions, weight, diameter of the supercharger and propeller, distance from the center of mass of the WUA to the center of its aerodynamic drag.In 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 of individual parameters and use them for comparative analysis with your own projects.
The lightest WUAs have a mass of about 100 kg, the heaviest - more than 1000 kg. Naturally, the smaller the mass of the apparatus, the less engine power is required for its movement, or the higher performance can be achieved with the same power consumption.
Below are the most characteristic data on the mass of individual components that make up the total mass of an amateur WUA: an 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 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, the given amount of cargo carried, the fuel and oil reserves necessary to ensure the required cruising range.
In parallel with the calculation of the mass of the AWP, 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 air cushion support forces pass through the common center of gravity (CG) of the apparatus. At the same time, it should be taken into account 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 device so as not to cause it to move.
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, structural units of passengers and cargo are applied (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, it is possible to determine the position of the CG of the entire apparatus by the formulas:
The designed amateur WUA must meet certain operational, design and technological requirements. The basis for creating a project and design of a new type of WUA are, first of all, the initial data and technical conditions that determine the type of device, its purpose, gross weight, load capacity, dimensions, type of main power plant, running characteristics and specific features.
From tourist and sports WUAs, as, indeed, from other types of amateur WUAs, ease of manufacture, the use of easily accessible materials and assemblies in the design, as well as complete safety of operation are required.
Speaking about driving characteristics, they mean the height of the AWP and the ability to overcome obstacles associated with this quality, maximum speed and throttle response, as well as the length of the braking distance, stability, controllability, and cruising range.
In the WUA design, the hull shape plays a fundamental role (Fig. 2), which is a compromise between:
- a) contours that are round in plan, 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) a pointed nose ("beak-shaped") hull shape, optimal from a hydrodynamic point of view during movement on a rough water surface;
- d) the 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 apparatus G, kg;
- air cushion area S, m 2 ;
- length, width and outline of the hull in plan;
- lifting system engine power N v.p. , kW;
- traction motor power N dv, KW.
- pressure in the air cushion P v.p. =G:S;
- specific power of the lifting system q v.p. = G:N c.p. .
- specific power of the traction motor q dv = G:N dv, and also start developing the configuration of the AWP.
The principle of creating an air cushion, superchargers
Most often, in the construction of amateur WUAs, two schemes for the formation of an air cushion are used: chamber and nozzle.In the chamber circuit, which is most often used in simple designs, the volume flow of air passing through the air path of the apparatus is equal to the volume flow of air of the blower
where:
F is the area of the perimeter of the gap between the support 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 outflow from under the device; with sufficient accuracy, it can be calculated by the formula:
where P c.p. - air cushion pressure, Pa; g - free fall acceleration, m/s 2 ; y - air density, kg / m 3.
The power required to create an air cushion in a chamber circuit is determined by the approximate formula:
where P c.p. - pressure after the supercharger (in the receiver), Pa; η n - the efficiency of the supercharger.
Air cushion pressure and air flow are the main parameters of an air cushion. Their values depend primarily on the dimensions of the apparatus, i.e., on the mass and bearing surface, on the hovering height, speed of movement, the method of creating an air cushion and resistance in the air path.
The most economical hovercraft are large-sized or large bearing surfaces, where the minimum pressure in the cushion allows a sufficiently large load-carrying capacity to be obtained. 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 an amateur designer. With a decrease in the size of the WUA, a significant increase in air cushion pressure is required and, accordingly, an increase in power consumption.
In turn, negative phenomena depend on the pressure in the air cushion and the rate of air flow from under the apparatus: splashing while moving over water and dusting when moving over a sandy surface or loose snow.
Apparently, the successful design of the WUA is, in a certain 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 supercharger into the cavity of the pillow, it must have a minimum aerodynamic resistance (Fig. 3). The power losses that are inevitable during the passage of air through the channels of the air path are of two kinds: the loss due to the movement of air in straight channels of constant cross section and local losses due to expansion and bending of the channels.
In the air path of small amateur WUAs, losses due to the movement of air flows along straight channels of constant cross section are relatively small due to the insignificant length of these channels, as well as the thoroughness of their surface treatment. These losses can be estimated using 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=(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 a cylindrical channel equivalent in cross-sectional area); v - coefficient of kinematic viscosity of air, m 2 / s.
Local power losses associated with a strong increase or decrease in the cross section of the channels and significant changes in the direction of the air flow, as well as losses for air intake into the blower, nozzles and to the rudders, are the main costs of the blower power.
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 supercharger in the AUA 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 form a 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 the air cushion, the height of the apparatus and the magnitude of the losses, the constituent components p sυ and p dυ vary. This determines the choice of type and performance of superchargers.
In a chamber air cushion scheme, 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 above.
When calculating the required power of an AVP blower with a flexible air cushion guard (nozzle circuit), the static pressure downstream of 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 - 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 value of k p ranges from 1.25÷1.5.
The blower air volume flow can be calculated using the formula:
The regulation of the performance (flow rate) of the AVP blowers is carried out most often - by changing the rotational speed or (less often) by throttling the air flow in the channels with the help of rotary dampers located in them.
After the required power of the supercharger is calculated, it is necessary 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 of the maximum engine power indicated in the motorcycle passport is taken as the calculated power. It is necessary to provide for intensive cooling of the engine and thorough cleaning of the air entering through the carburetor. It is also important to obtain a unit with a minimum mass, which is the sum of the mass of the engine, the transmission between the supercharger and the engine, as well as the mass of the supercharger itself.
Depending on the type of WUA, engines with a displacement of 50 to 750 cm 3 are used.
In amateur WUAs, both axial superchargers and centrifugal superchargers are used equally. Axial superchargers are intended for small and simple structures, centrifugal - for AVP with significant pressure in the air cushion.
Axial superchargers typically have four or more vanes (Figure 9). They are usually made of wood (four-blade) or metal (superchargers with a large number of blades). If they are made of aluminum alloys, then the rotors can be cast, and welding can also be applied; it is possible to make them of welded structure from steel sheet. The range of pressure generated 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 a welded metal structure or molded from fiberglass. The blades are made bent from a thin sheet or with a profiled cross section. Centrifugal superchargers create pressure up to 3000 Pa, and their efficiency reaches 83%.
Choice of traction complex
Propulsors that create horizontal thrust can be divided mainly into three types: air, water and wheeled (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-jet propulsion. In the simplest designs, horizontal thrust can sometimes be created by tilting the AWP and using the resulting horizontal component of the force of the air flow flowing from the air cushion. The air mover is convenient for amphibious vehicles that do not have contact with the supporting surface.
If we are talking about WUAs that move only above the surface of the water, then you can use a propeller or a water jet propulsion. Compared to air propulsion, these propulsion units allow you to get much more thrust per 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 propeller elements, all types of resistance that occur during the movement of the WUA should be taken into account. Aerodynamic drag is calculated by the formula
The water resistance due to the formation of waves when the WUA moves through the water can be calculated by the formula
where:
V - WUA movement speed, m/s; G - WUA mass, kg; L is the length of the air cushion, m; ρ - water density, kg s 2 / m 4 (at a temperature sea water+4°C is equal to 104, river - 102);
C x - coefficient of aerodynamic resistance, depending on the shape of the device; is determined by blowing WUA models in wind tunnels. Approximately, you can take C x =0.3÷0.5;
S - cross-sectional area of the WUA - its projection on a plane perpendicular to the direction of movement, m 2 ;
E - wave resistance coefficient, depending on the AWP speed (Froude number Fr=V:√g·L) and the ratio of air cushion dimensions L:B (Fig. 12).
As an example, in Table. 2 shows the calculation of resistance depending on the speed of movement for a device with a length of L = 2.83 m and B = 1.41 m.
Knowing the resistance to 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), assuming the efficiency of the propeller η p equal to 0.6, and the efficiency of transmission from the engine to the propeller η p \u003d 0 ,9:
As an air propulsor for amateur WUAs, a two-blade propeller is most often used (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 mechanically affected by solid particles or sand sucked in together with the air flow, are protected by brass sheet fittings.
Four-bladed propellers are also used. The number of blades depends on the operating conditions and the purpose of the propeller - for the development of high speed or the creation of significant thrust at the time of launch. A two-blade propeller with wide blades can also provide sufficient thrust. Thrust is generally increased if the propeller runs in a profiled nozzle ring.
The finished screw must be balanced, mainly statically, before being mounted on the motor shaft. Otherwise, it will vibrate when it rotates, which may cause damage to the entire machine. Balancing with an accuracy of 1 g is quite sufficient for amateurs. In addition to balancing the screw, its runout relative to the axis of rotation is checked.
General layout
One of the main tasks of the designer is to connect all the aggregates into one functional whole. When designing the apparatus, the designer is obliged to provide a place for the crew, placement of units of the lifting and propulsion systems within the hull. At the same time, it is important to use the designs of already known WUAs as a prototype. On fig. Figures 14 and 15 show structural diagrams of two typical amateur-built WUAs.In most WUAs, the body is a load-bearing element, a single structure. It contains the units of the main power plant, air channels, control devices and the driver's cab. The driver's cabs are located in the bow or central part of the apparatus, depending on where the supercharger is located - behind the cab or in front of it. If the WUA is multi-seat, the cabin is usually located in the middle part of the vehicle, which makes it possible to operate it with a different number of people on board without changing the alignment.
In small amateur WUAs, the driver's seat is most often open, protected in front by a windshield. In devices of a more complex design (tourist type), the cabins are covered with a transparent plastic dome. 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 control of the AVP is carried out using either rudders placed in the air flow behind the propeller, or guide devices fixed in the air flow flowing from the air-jet propulsion unit. The control of the device from the driver's seat can be of an aviation type - using the handles or levers of the steering wheel, or, as in a car, the steering wheel and pedals.
In amateur WUAs, two main types of fuel systems are used; with gravity fuel supply and with an automotive or aircraft-type gasoline 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 aviation or automotive parts.
Exhaust gases from the engine are always discharged to the rear of the vehicle and never to the pillow. To reduce the noise generated during the operation of WUAs, especially near settlements, automobile-type silencers are used.
In the simplest designs, the lower part of the body serves as a chassis. The role of the chassis can be performed by wooden skids (or skids), which take on the load when in contact with the surface. In tourist WUAs, which are heavier than sports WUAs, wheeled chassis are mounted, which facilitate the movement of WUAs during stops. Usually two wheels are used, mounted on the sides or along the longitudinal axis of the WUA. The wheels have contact with the surface only after the cessation of the lifting system, when the AUA touches the surface.
Materials and manufacturing technology
High-quality pine lumber similar to those used in the aircraft industry, as well as birch plywood, ash, beech and linden wood are used for the manufacture of wooden structure WUAs. 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 exceptionally durable, resistant to atmospheric influences and humidity, as well as to friction. In Poland, fire-resistant fabric covered with plastic-like PVC is most often used.
It is important to perform the correct cutting and ensure that the panels are carefully connected to each other, as well as fastening them 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 the form of a flexible air cushion fence, one should not forget about Pascal's law, which states that air pressure is distributed in all directions with the same force. Therefore, the shell of the flexible barrier in the inflated state must be in the form of a cylinder or a sphere, or a combination thereof.
Housing design and strength
Forces are transferred to the WUA hull from the load carried by the vehicle, the weight of the mechanisms of the power plant, etc., as well as loads from external forces, impacts of the bottom against the wave and pressure in the air cushion. 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 floating mode ensures the buoyancy of the hull. The hull is affected by concentrated forces, bending and torsional moments from the engines (Fig. 16), as well as gyroscopic moments from the rotating parts of the mechanisms that occur during the AWP maneuvering.The most widely used are two constructive types of buildings for amateur WUAs (or their combinations):
- truss construction, when the overall strength of the hull is ensured by flat or spatial trusses, and the skin is intended only to hold air in the air path and create buoyancy volumes;
- with load-bearing plating, when the overall strength of the hull is provided by the outer plating, working in conjunction with the longitudinal and transverse framing.
The design of the cab and its glazing should ensure the possibility of a quick exit of the driver and passengers from the cab, especially in the event of an accident or fire. The location of the windows should provide the driver good review: line of sight must be between 15° down and 45° up from the horizontal line; side view must be at least 90 ° on each side.
Power transmission to propeller and supercharger
The simplest for amateur manufacturing 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.In the case of V-belt transmission, to ensure the durability of the belts, the diameters of the pulleys should be chosen as maximum, however, the circumferential speed of the belts should not exceed 25 m/s.
The design of the lifting complex and flexible fencing
The lifting complex consists of an injection unit, air channels, a receiver and a flexible air cushion guard (in nozzle schemes). 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 fences of amateur WUAs usually have a simplified form and design. On fig. 18 shows examples of design schemes of flexible barriers and a method for checking the shape of a flexible barrier after it has been mounted on the body of the apparatus. Fences of this type have good elasticity, and due to the rounded shape they do not cling to the unevenness of the supporting surface.
The calculation of superchargers, both axial and centrifugal, is rather complicated and can only be performed 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 - an elevator.
The control can be made in the form of an automobile or motorcycle steering wheel. Considering, however, the specifics of the design and operation of the WUA as an aircraft, the aviation design of the controls in the form of a lever or pedals is more often used. In its simplest form (Fig. 19), when the handle is tilted sideways, the movement is transmitted by means of a lever fixed on the pipe to the elements of the steering cable wiring and then to the rudder. The movements of the handle back and forth, possible due to its hinged fastening, are transmitted through the pusher, passing inside the tube, to the wiring of the elevator.
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 openings in the cutouts in the guides mounted on the sides of the apparatus.
An example of the design of the rudder in the case of its placement in the air flow thrown by the propeller is shown in Fig. twenty.
The rudders can either be fully rotatable or consist of two parts - fixed (stabilizer) and rotatable (rudder blade) with different percentages of the chords of these parts. Rudder profiles of any type must be symmetrical. The rudder stabilizer is usually fixed to the body; main bearing element The stabilizer is a spar to which the rudder blade is hinged. Elevators, very rare in amateur WUAs, are constructed on the same principles and sometimes even exactly the same as the rudders.
Structural elements that transmit movement from controls to steering wheels and engine throttles 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, amateur WUAs use combined systems - with cables and pushers.
Editorial
Increasingly, fans of water-motor sports and tourism are paying more and more attention to hovercraft. With a relatively small power consumption, they allow you to achieve high speeds; shallow and impassable rivers are accessible to them; hovercraft can hover above the ground and above the ice.For the first time, we introduced readers to the issues of designing small SVPs back in the 4th issue (1965), placing an article by Yu. A. Budnitsky “Soaring Ships”. A brief outline of the development of foreign SVPs was published, including a description of a number of sports and recreational modern 1- and 2-seater SVPs. The editors introduced the experience of independent construction of such an apparatus by Riga resident O. O. Petersons in. The publication of this amateur design aroused especially great interest among our readers. Many of them wanted to build the same amphibian and asked for the necessary literature.
This year the publishing house "Sudostroenie" publishes a book by the Polish engineer Jerzy Ben "Models and amateur hovercraft". In it you will find a presentation of the fundamentals of the theory of the formation of an air cushion and the mechanics of movement on it. The author gives the calculated ratios that are necessary for independent design the simplest SVP, introduces the trends and prospects for the development of this type of vessels. The book contains many examples of the designs of amateur hovercraft (AHVs) built in the UK, Canada, USA, France, Poland. The book is addressed to a wide range of fans of self-construction of ships, ship modellers, water motorists. 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 hovercraft Airskat-240
Double sports SVP with a transverse symmetrical arrangement of seats. Mechanical installation - automob. dv. "Volkswagen" with a power 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 a system of rudders placed in the stream behind the propeller. Electrical equipment 12 V. Engine start - electric starter. The dimensions of the device are 4.4x1.98x1.42 m. The air cushion area is 7.8 m 2; propeller diameter 1.16 m, gross weight - 463 kg, maximum speed on water 64 km / h.American SVP firm "Skimmers Incorporated"
A kind of single SVP scooter. The body design is based on the idea of using a car camera. Two-cylinder motorcycle motor with a power of 4.4 kW. The dimensions of the device are 2.9x1.8x0.9 m. The air cushion area is 4.0 m 2; gross weight - 181 kg. The maximum speed is 29 km/h.English hovercraft "Air Ryder"
This two-seat sports apparatus is one of the most popular among amateur shipbuilders. The axial supercharger is driven by a motorcycle, dv. working volume 250 cm 3 . Propeller - two-blade, 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 apparatus has dimensions of 3.81x1.98x2.23 m; ground clearance 0.03 m; rise 0.077 m; pillow area 6.5 m 2; 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 of a single modification of the apparatus.
English SVP "Hovercat"
Light tourist boat for five or six people. There are two modifications: "MK-1" and "MK-2". The centrifugal supercharger with a diameter of 1.1 m is driven by a car. dv. "Volkswagen" with a working volume 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 was used for horizontal thrust. dv. "Porsche 912" with a volume of 1582 cm 3 and a power of 67 kW. The apparatus is controlled by means of aerodynamic rudders placed in the stream behind the propeller. Electrical equipment with a voltage of 12 V. The dimensions of the apparatus are 8.28x3.93x2.23 m. The air cushion area is 32 m 2, the gross weight of the apparatus is 2040 kg, the speed of movement of the modification "MK-1" is 47 km / h, "MK-2" - 55 km/h
Notes
1. Simplified method for propeller selection based on known drag, RPM, and speed forward movement given in .2. Calculations of V-belt and chain drives can be performed using the standards generally accepted in domestic engineering.
Good day to all. I want to present to you my SVP model made in a month. I apologize right away, the introduction is not quite the same photo, but also related to this article. Intrigue...
Retreat
Good day to all. I want to start with how I got into radio modeling. A little over a year ago, for the fifth anniversary of the child gave a hovercraft
Everything was fine, charged, rode until a certain point. While the son, secluded in his room with a toy, decided to put the antenna from the remote control into the propeller and turn it on. The propeller shattered into small pieces, did not begin to punish, since the child himself was upset, the whole toy was damaged.
Knowing that we have a Hobby World store in our city, I went there, and where else! They didn’t have the propeller they needed (the old one was 100mm), and the smallest one, which was 6’x4’ in the amount of two pieces, forward and reverse rotation. Nothing to do took what is. Having cut them to the desired size, I installed them on a toy, but the thrust was no longer the same. And a week later, we had ship modeling competitions at which my son and I were also present as spectators. And that's it, that spark and craving for modeling and flying caught fire. After that, I got acquainted with this site and ordered parts for the first aircraft. True, before that I made a small mistake by buying a remote control in a store for 3500, and not a PF in the region of 900 + delivery. While waiting for a package from China, I flew a simulator through an audio cord.
Four aircraft were built during the year:
- Sandwich Mustang P-51D, span-900mm. (crashed on first flight, equipment removed)
- Cessna 182 ceiling and styrofoam, span-1020mm. (beaten, killed, but alive, equipment removed)
- Plane "Don Quixote" from the ceiling and polystyrene foam, span-1500mm. (broken three times, two wings re-glued, now I fly on it)
- Extra 300 from the ceiling, span-800mm (broken, awaiting repair)
- built
Since I have always been attracted to water, ships, boats and everything connected with them, I decided to build a SVP. After digging around on the Internet, I found the site model-hovercraft.com and the construction of the hovercraft Griffon 2000TD.
Building process:
Initially, the case was made from 4mm plywood, sawed everything out, glued it together, and after weighing, abandoned the idea with plywood (weight was 2.600 kg.), And it was also planned to glue it with fiberglass, plus electronics.
It was decided to make the body of expanded polystyrene (insulation, further penoplex) glued with fiberglass. A foam sheet 20 mm thick was cut into two 10 mm thick foam.
The case is cut and glued, after which it is pasted over with fiberglass (1 sq.m., epoxy 750gr.)
The superstructures were also made of expanded foam 5mm, before painting, I went through all the surfaces and parts of the foam with epoxy resin, after which I painted everything with acrylic spray paint. True, in several places the penoplex was a little eaten up, but not critical.
The material for the flexible fencing (hereinafter referred to as the SKIRT) was first chosen rubberized fabric (oilcloth from a pharmacy). But again, due to the large weight, it was replaced with a dense water-repellent fabric. According to the patterns, a skirt for the future SVP was cut and sewn.
The skirt and body were glued together with UHU Por glue. I put the motor with a regulator from the "Patrolman" and tested the skirt, the result pleased. The rise of the SVP body from the floor is 70-80mm,
I checked the ability to move on carpet and linoleum, I was satisfied with the result.
The fencing-diffuser of the main propeller was made of foam glued with fiberglass. The rudder was made from a ruler, bamboo skewers glued with Poxipol.
All available means were also used: rulers 50 cm, balsa 2-4mm, bamboo skewers, toothpicks, copper wire 16kv, scotch threads, etc. Small details were made (hatch hatches, handles, handrails, searchlight, anchor, anchor line box, life raft container on a stand, mast, radar, wiper leashes with wipers) for more detailed model.
The stand for the main motor is also made from ruler and balsa wood.
Navigation lights were made on the ship. A white LED and a red flashing LED were installed in the mast, since the yellow one was not found. On the sides of the cabin, red and green running lights are installed in specially made housings for them.
Lighting power is controlled via a toggle switch by a HXT900 servo machine.
Separately, the traction motor reverse block was assembled and installed using two limit switches and one HXT900 servo machine
Lots of pictures in the first part of the video.
Sea trials were carried out in three stages.
The first stage, running around the apartment, but due to the considerable size of the vessel (0.5 sq.m.) it’s not very good, so it’s convenient to ride around the rooms. There were no issues, everything went smoothly.
The second stage, sea trials on land. The weather is clear, the temperature is +2...+4, the side wind across the road is 8-10m/s with gusts up to 12-14m/s, the asphalt surface is dry. When turning downwind, the model skids very strongly (there was not enough strip). But when turning against the wind, everything is quite predictable. It has good straightness of travel with a slight rudder trim to the left. After 8 minutes of operation on asphalt, there were no signs of wear on the skirt. But still, it was not built for asphalt. It's very dusty from underneath.
The third stage is the most interesting in my opinion. Water tests. Weather: clear, temperature 0...+2, wind 4-6m/s, pond with small thickets of grass. For the convenience of video shooting, I switched the channel from ch1 to ch4. At the start, breaking away from the water, the ship easily went over the water surface, slightly disturbing the pond. Steering is quite confident, although, in my opinion, the rudders should be made wider (the width of the ruler was 50 cm). Water splashes do not even reach the middle of the skirt. Several times he ran into grass growing from under the water, overcame the obstacle without difficulty, although he got stuck in the grass on land.
Fourth stage, snow and ice. It remains only to wait for the snow and ice to complete this stage in full. I think it will be possible to reach by snow top speed on this model.
Components used in the model:
- (Mode2 - throttle LEFT, 9 channels, version 2). V / h module and receiver (8 channels) - 1 set
- Turnigy L2205-1350 (suction motor) -1pc.
- for brushless motors Turnigy AE-25A (for blower motor) -1pc.
- TURNIGY XP D2826-10 1400kv (marching engine)-1pc
- TURNIGY Plush 30A (for main engine) -1pc.
- Poly composite 7x4 / 178 x 102 mm - 2 pcs.
- Flightmax 1500mAh 3S1P 20C -2 pcs.
- airborne
Mast height min: 320mm.
Mast height max: 400mm.
Height from surface to bottom: 70-80mm
Full displacement: 2450gr. (with battery 1500 mAh 3 S 1 P 20 C -2pcs).
Power reserve: 7-8min. (with a 1500 mAh 3S1 P 20 C battery, it sank earlier on the main engine than on the pressure one).
Video report on construction and testing:
Part one - the stages of construction.
Part two - tests
Part three - sea trials
A few more photos:
Conclusion
The SVP model turned out to be easy to manage, with a good power reserve, it is afraid of strong side winds, but it can be handled (requires active taxiing), I consider a reservoir and snowy expanses to be an ideal environment for the model. Not enough battery capacity (3S 1500mA/h).
I will answer all your questions about this model.
Thank you for your attention!
Hovercraft allows you to move on water and on land. In this article we will look at how to make it yourself.
Hovercraft - what is it
One of the ways to combine a car and a boat was a hovercraft, which has good cross-country ability and high speed of movement on water due to the fact that its body does not sink under water, but, as it were, slides on its surface.
This method allows you to move economically and quickly, since the sliding friction force and the resistance force of water masses are, as they say, two big differences.
But, unfortunately, despite all the advantages of a hovercraft, its scope on the ground is limited - it can not move on any surface, but only on fairly soft ones, such as sand or soil. Asphalt and hard rocks with sharp stones and industrial waste will simply tear up the bottom of the vessel, rendering the air cushion unusable, and it is thanks to it that the SVP moves.
Therefore, hovercrafts are used mainly where you need to swim a lot and drive a little, otherwise amphibious vehicles with wheels are used. SVPs are not widely used today, but in some countries rescuers work on them, for example, in Canada, and there is also evidence that they are in service with NATO.
Buy a hovercraft or make your own?
Hovercrafts are quite expensive, for example, an average model costs about 700 thousand rubles, while the same scooter "scooter" can be bought 10 times cheaper. But of course, by paying money, you get factory quality, and you can be sure that the ship will not fall apart right under you, although there have been such cases, but the probability here is lower than for a homemade one.
In addition, manufacturers mainly sell "professional" hovercraft for fishermen, hunters, and all kinds of services. Amateur boats are extremely rare, and mostly they are handmade products, due, again, to their low popularity among the people.
Why hovercrafts haven't won more love
Main reasons:
- High price and expensive service. The fact is that the parts and functional units of the SVP wear out very quickly and require replacement, and the purchase and installation also cost a lot of money. Therefore, only a rich person can afford it, but even for him it is very inconvenient to take a broken ship to a repair shop every time, since there are only a few such workshops, and they are mainly located only in major cities. Therefore, as a toy, it is more profitable to buy, for example, an ATV or a jet ski.
- Because of the screws, they are very noisy, so you can only ride with headphones.
- You can not swim and ride against the wind, because the speed is greatly reduced.
Amateur hovercraft have been and remain only a way of displaying their design abilities for those who can maintain and repair them themselves.
DIY manufacturing process
Making a good hovercraft is not easy, but if you think about it, then most likely you have either the ability or the desire, but please note that if you do not have a technical background, forget about this idea, because your hovercraft will crash on the first test drive.
So, you should start with a drawing. Design your SVP. How do you want to see it? Rounded like the Soviet MI-28 helicopter or angular like the American Alligator? Should it be streamlined like a Ferrari, or Zaporozhets-shaped? When you answer these questions for yourself, start creating a drawing.
How to catch more fish?
For 13 years of active fishing, I have found many ways to improve the bite. And here are the most effective ones:- Cool activator. Attracts fish in cold and warm water with the help of pheromones included in the composition and stimulates their appetite. It's a pity that Rosprirodnadzor wants to ban its sale.
- More sensitive gear. Read the relevant manuals for the particular type of tackle on the pages of my website.
- Lures based pheromones.
The figure shows a sketch of the SVP, which is in service with the Canadian Rescue Service.
Vessel Specifications
An average homemade SVP can reach a fairly high speed - which one - depends on the mass of passengers and the boat itself, as well as on engine power, but in any case, with the same engine parameters and weight, an ordinary boat will be several times slower.
Regarding the carrying capacity, we can say that the single-seat hovercraft model proposed here is able to withstand a driver weighing 100-120 kg.
You will have to get used to the control, since it differs significantly from a conventional boat, firstly, because there are completely different speeds, and secondly, fundamentally different ways of moving.
The faster the SVP moves, the more it skids on turns, so you need to lean a little to the side. By the way, if you get used to it, then you can “drift” well on a hovercraft.
Necessary materials
All you need is plywood, styrofoam and a special kit from Universal Hovercraft, designed specifically for self-taught engineers, containing everything you need.
Insulation, screws, air cushion fabric, epoxy, glue, and more are all included in the kit, which you can order from their official website for $500, plus it comes with multiple blueprint options.
Case manufacturing
The bottom is made of foam, 5-7 cm thick, for one person, if you want to make a vessel for two or more passengers, then attach another sheet of the same from below. Next, two holes need to be made in the bottom: one for air flow, and the second for inflating the pillow. You can use a jigsaw.
Next, you need to isolate the lower part of the case from water - fiberglass is ideal for this. Apply it to the foam and treat with epoxy. But bumps and air bubbles can form on the surface, to prevent this, cover the fiberglass with plastic wrap, and cover with a blanket. Put another layer of film on top, and tape it to the floor. To blow air out from under the resulting "sandwich", use a conventional vacuum cleaner. The bottom of the hull will be ready in 2.5-3 hours.
The upper part of the body can be made arbitrary, but we should not forget about aerodynamics. Making a pillow is easy. It is only necessary to correctly fix it, and synchronize it with the bottom - that is, to make sure that the air flow from the engine passes through the hole into the pillow without losing efficiency.
Make a pipe for the motor from styrofoam, do not miscalculate with the dimensions so that the screw enters it, but the gap between its edges and the inside of the pipe was not very large, as this will reduce traction. The next step is to install the holder for the motor. In fact, this is just a stool with three legs that are attached to the bottom, and an engine is placed on top of it.
Engine
There are two options - a ready-made engine from Yu.Kh. or homemade. You can take it from a chainsaw or a washing machine - the power they give is enough for an amateur SVP. If you want something more, you should look at the motor from the scooter.
Hovercraft with minimal cash outlay and shallow knowledge in the field of creating hovercraft.
The assembly of the SVP was carried out at the department of the Saratov State Technical University by its students. Photos and videos were taken with the HTC Mozart camera.
Project idea
This kind of crazy idea was reduced to creating a model of a hovercraft controlled by a radio signal. This SVP is capable of flying over small obstacles (as ekranoplanes of B or even C class do). There are plans to install a vision system that will notice obstacles and help overcome them. This system will also be able to identify similar SVPs and follow them. In case of successful completion of the project, a group of SVPs will emerge with the ability to manage only one of the vessels.
Necessary materials and equipment
To create a hovercraft, the following materials and equipment were required:
penoplex - 2 (3) pieces (500 or 750 rubles)
polystyrene - 2 shputs of 1.5 meters (total 900 rubles)
double-sided adhesive tape made of fabric - 1 piece for 50 rubles.
glue "Titan" - 1 piece 80 r.
medical oilcloth - 1 (3) pieces 100 rubles (300 rubles)
speed controller - 2(3) pieces 2540 rubles (3810 rubles)
engine - 2 (4) pieces for 3110 rubles (6220 rubles)
battery - 2 pieces for 2360 rubles.
propeller - 2 (7-10) pieces 300 rub. (600 rubles)
servo drive - 1 piece, given to the authors for free
6-channel radio control - got 1 set free of charge
As a result, 15070 rubles were spent. with the maximum use of materials. As you can see, the budget is small and it can even be reduced to 9940 rubles.
SVP assembly process
First, all the missing materials were purchased: 2 batteries, 2 engines, as well as 2 sets of propellers, glue, adhesive tape, foam plastic. And the authors had 6-channel radio equipment at the department.
Penoplex was unmistakably chosen as the main material for the SVP hull due to its lightness, strength and convenience in giving a variety of shapes.
The creators found that the engine with the use of speed controllers, even without an air cushion, when working at 50%, perfectly lifted the hull into the air.
The holder for the engine was cut out of the used case. power supply.
The skirt was made from a single piece, a slit was made in the middle (cut pieces of film to create a skirt did not fit).
The skirt was made according to the following principle:
The further process of gluing the bottom of the SVP skirt is described in the picture and video:
The tail section of the vessel was made of polystyrene.
As a result, it turned out:
The remains of the hull were used to create a second motor.
All components of the SVP were screwed to the foam with long self-tapping screws. They hold on very tightly.
Completing the work on the foam, all the irregularities and shortcomings were hidden, containers for the sulfur line and batteries were cut.
The rudders and skin were also made of polystyrene.
The system that turns the steering wheel was created from the parts left over from the old manipulator.
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), the study of their fundamental structure, comparison of various designs and schemes.
For this purpose, I visited many Internet sites of WUA enthusiasts and creators (including foreign ones), got acquainted with some of them in person. In the end, for the prototype of what was conceived boats() took the English "Hovercraft" ("hovering ship" - as the WUA is called in the UK), built and tested by local enthusiasts.
Our most interesting domestic machines of this type for the most part were created for law enforcement agencies, and in recent years, for commercial purposes, they had large dimensions, and therefore were not very suitable for amateur production.
My device is air cushion(I call it "Aerojeep") - three-seater: the pilot and passengers are arranged in a T-shaped pattern, like on a tricycle: the pilot is in front in the middle, and the passengers behind are side by side, one next to the other.
The machine is single-engine, with a split air flow, for which a special panel is installed in its annular channel a little below its center. The boat-AVP consists of three main parts: a propeller unit with a transmission, a fiberglass hull and a "skirt" - a flexible fencing of the lower part of the hull - so to speak, a "pillowcase" of an air cushion. Corps "Airjeep".
It is double: fiberglass, consists of inner and outer shells. The outer shell has a rather simple configuration - these are just inclined (about 50 ° to the horizontal) sides without a bottom - flat almost across the entire width and slightly curved in its upper part. The bow is rounded, and the back has the form of an inclined transom.
In the upper part, along the perimeter of the outer shell, elongated holes-grooves are cut out, and at the bottom, a cable enclosing the shell is fixed in eyebolts from the outside for attaching the lower parts of the segments to it.
The inner shell is more complicated in configuration than the outer one, since it has almost all the elements of a small vessel (say, boats or boats): sides, bottom, curved gunwales, a small deck in the bow (there is no only the upper part of the transom 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 the fuel tank and battery, as well as the gas cable and the rudder control cable. In the aft part of the inner shell, a kind of poop is arranged, raised and open in front.
It serves as the base of the annular channel for the propeller, and its deck-bridge-separator of the air flow, part of which (supporting flow) is sent to the shaft opening, and the other part to create propulsive thrust.
All elements of the hull: the inner and outer shells, the tunnel and the annular channel, were glued on matrices of glass mat about 2 mm thick on polyester resin. 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 an 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. 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 casing shells, about 4 mm).
Before gluing the elements, all roughness and scratches 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 sprayer (or roller).
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 the side of the glass mat with smaller pores are smeared 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, a small slot can be made in the mat).
The subsequent layers of glass mats are laid in the same way to the required thickness (4-5 mm), with the installation, where necessary, of embedded parts (metal and wood). Excess flaps along 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 for the bottom.
In this case, additionally glue all the corners, as well as the places where the fasteners are screwed in. After the resin has hardened, the shell is easily removed from the matrix and processed: edges are turned, grooves are cut, holes are drilled. To ensure the unsinkability of the Aerojeep, pieces of foam (for example, furniture) are glued to the inner shell, leaving only channels for air passage around the entire perimeter free.
Pieces of foam plastic are glued together with resin, and strips of glass mat, also lubricated with resin, are attached to the inner shell. After separately manufacturing the outer and inner shells, they are joined, fastened with clamps and self-tapping screws, and then connected (glued) around the perimeter with strips of the same glass mat 40-50 mm wide coated with polyester resin, from which the shells themselves were made.
After that, the body is left until the resin is completely polymerized. A day later, a duralumin strip with a section of 30x2 mm is attached to the upper joint of the shells around the perimeter with rivets, setting it vertically (the tongues of the segments are fixed on it). Wooden skids measuring 1500x90x20 mm (length x width x height) are glued to the bottom of the bottom at a distance of 160 mm from the edge.
One layer of glass mat is glued on top of the runners. In the same way, only from the inside of the shell, in the aft part of the cockpit, a base of a wooden plate is arranged under the engine. It is worth noting that the same technology used to make the outer and inner shells also glued smaller elements: the inner and outer shells of the diffuser, rudders, gas tank, engine cover, wind deflector, tunnel and driver's seat.
For those who are just starting to work with fiberglass, I recommend preparing the manufacture boats from these small elements. The total mass of the fiberglass body, together with the diffuser and rudders, is about 80 kg.
Of course, the manufacture of such a hull can also be entrusted to specialist firms producing fiberglass boats and boats. Fortunately, there are many of them in Russia, and the costs will be commensurate. However, in the process self-manufacturing will be able to gain the necessary experience and the opportunity in the future to model and create various elements and structures made of fiberglass. Propeller installation.
It includes an engine, a propeller and a transmission that transmits torque from the first to the second. The engine used is BRIGGS & STATTION, produced in Japan under an American license: 2-cylinder, V-shaped, four-stroke, 31 hp. at 3600 rpm. Its guaranteed motor resource is 600 thousand hours.
The start is carried out by an electric starter, from the battery, and the operation of the spark plugs is from a magneto. The engine is mounted on the bottom of the Aerojeep hull, and the propeller hub axle is fixed at both ends on brackets in the center of the diffuser raised above the hull. The transmission of torque from the output shaft of the engine 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), but 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 machine, especially such an “aerofloating” one.
Exhaust gases are led into the lower air stream. Instead of the installed Japanese one, you can also use suitable domestic engines, for example, from snowmobiles "Buran", "Lynx" and others. By the way, for a single or double WUA, smaller engines with a capacity of about 22 hp are quite suitable. With.
The propeller is six-blade, with a fixed pitch (angle of attack set on land) of the blades. An integral part of the propeller installation should also include the annular channel of the propeller, although its base (lower sector) is made integral with the inner shell of the housing.
The annular channel, like the body, is also composite, glued from the outer and inner shells. Just in the place where its lower sector joins the upper one, a fiberglass dividing panel is arranged: it separates the air flow created by the propeller (and, on the contrary, connects the walls of the lower sector along the chord).
The engine, located at the transom in the cockpit (behind the passenger seat), is closed on top with a fiberglass hood, and the propeller, in addition to the diffuser, is also a wire grill in front. Soft elastic fencing "Aerojeep" (skirt) consists of separate, but identical segments, cut and sewn from a dense lightweight fabric.
It is desirable that the fabric is water-repellent, does not harden in the cold and does not let air through. I used a Finnish-made Vinyplan material, but a domestic percale-type fabric is fine. The segment pattern is simple, and you can even sew it by hand. Each segment is attached to the body as follows.
The tongue is thrown over the side vertical bar, with an overlap of 1.5 cm; on it is the tongue of the adjacent segment, and both of them, in the place of overlap, are fixed on the bar with a special clip of the “crocodile” type, only without teeth. And so on the entire perimeter of the "Aerojeep". 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 wrapping around the lower part of the outer shell of the housing. Such a composite design of the skirt allows you to easily replace a failed segment, which will take 5-10 minutes. It would be appropriate to say that the design turns out to be efficient if up to 7% of the segments fail. In total, they are placed on a skirt up to 60 pieces.
The principle of movement of the "Aerojeep" is as follows. After starting the engine and running it for Idling the device remains in place. With an increase in the number of revolutions, the propeller begins to drive a more powerful air flow. Part of it (large) creates propulsion and provides the boat with movement forward.
The other part of the flow goes under the dividing panel into the side air ducts of the hull (the free space between the shells up to the very bow), and then through the slots in the outer shell it evenly enters the segments.
Simultaneously with the start of movement, this flow creates an air cushion under the bottom, lifting the apparatus above the underlying surface (be it soil, snow or water) by several centimeters. The rotation of the "Aerojeep" is carried out by two rudders, deflecting the "forward" air flow to the side.
The rudders are controlled from a two-arm motorcycle-type steering column lever, through a Bowden cable running along the starboard side between the shells to one of the rudders. The other steering wheel is connected to the first rigid rod. On the left handle of the two-arm lever, the carburetor throttle control lever (analogue of the throttle grip) is also fixed.
For operation hovercraft it must be registered with the local State Inspectorate for Small Vessels (GIMS) and receive a ship's ticket. To obtain a certificate for the right to drive a boat, you also need to take a course in managing a small boat. However, even these courses are still far from having instructors for piloting hovercraft.
Therefore, each pilot has to master the management of the WUA on their own, literally bit by bit gaining relevant experience.
Hovercraft "Aerojeep": 1 - segment (dense fabric); 2-mooring duck (3 pcs.); 3 wind visor; 4-side strap fastening segments; 5-handle (2 pcs.); 6-protection of the propeller; 7-ring channel; 8-rudder (2 pcs.); 9-rudder control lever; 10-access hatch to the gas tank and battery; 11-pilot's seat; 12-passenger sofa; 13-engine casing; 14-engine; 15-outer shell; 16-filler (polystyrene); 17-inner shell; 18-dividing panel; 19-air screw; 20 - propeller bushing; 21-drive toothed belt; 22-knot for fastening the bottom of the segment
Theoretical drawing of the hull: 1 - inner shell; 2-outer shell
Scheme of transmission of a propeller installation: 1 - output shaft of the engine; 2-leading toothed pulley; 3 - toothed belt; 4-driven toothed pulley; 5 - nut; 6-distance bushings; 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 scheme: 1-steering column; 2-Bowden cable, 3-braid attachment to the body (2 pcs.); 4-bearing (5 pcs.); 5-steering panel (2 pcs.); 6-double-arm lever-bracket (2 pcs.); 7-connecting rod steering panels (see photo)
Flexible fencing segment: 1 - walls; 2-lid with tongue