Svp hovercraft. Cargo-passenger hovercraft hovercraft. The need of government agencies

Hovercraft Jeyran and Bison SVP (hovercraft)

Ideas often appear long before they can be implemented. And it happens that the embodied ideas stand alone, ahead of their time. Such was the fate of flying ships - hovercraft.
Simply put, a hovercraft (hovercraft) is an inverted saucer under which air is pumped: as a result, the structure rises, and if you place an air propeller on the side, it also moves. Lack of friction on the surface - allows you to reduce resistance. Soviet tests of flying boats have been going on since the 30s in secrecy. Vladimir Levkov was engaged in the work.

the first combat flying hovercraft L5

The first model of Levkov resembled exactly an inverted plate, more precisely, a basin: in the center there was an electric motor with a screw that pumped air, and the “vessel” was torn off the floor, hovering in the air. After several experimental machines, the first combat flying boat, the L5, appeared in 1937. On its bow and stern there were two M-45 aircraft engines of 850 horsepower each. The boat "squeezed" about 130 kilometers per hour (at full speed, not a single torpedo will catch up) and calmly moved over water and land, despite the weight of eight tons. The test results showed its superiority over torpedo boats, but also revealed disadvantages: overheating of the engines, low stability (that is, the low ability of the ship, unbalanced, to return to its original position). But the main thing is a small separation of the hull from the surface, because of which the car could not overcome even a low obstacle.

British hovercraft SR-1

Only one detail was missing. And found her, as often happens, a layman. The Englishman Christopher Cockerell, an electronics engineer, opened a small boatyard in 1950. Improving his boats, he wanted to reduce their drag by using air "lubrication". He was the first to use the method of creating an air cushion: when the air does not flow freely under the bottom from the fan, but is forced by narrow nozzles located around the perimeter. The separation of the body from the surface reached 300 mm - five times higher than that of Levkov. According to this scheme, Saunders RO built the SR-1 KVP (hovercraft), on which the British crossed the English Channel in 1959 ... and ... became the pioneers in the creation of a hovercraft. Our Soviet tests of flying boats, which have been going on since the 30s, were conducted in secrecy, confusing bystanders - as a result, the whole world recognized Kokkerel as the father of hovercraft.
After Levkov passed away, all of his materials ended up in the Almaz Central Marine Design Bureau in Leningrad. Development continued, but only on the initiative of the Central Design Bureau itself - until Cockerel announced itself. Keeping up with the British was a matter of honor - besides, the military leadership was well aware that the high-speed and amphibious qualities of SVPs were promising for use in amphibious naval operations.

BY THE PRINCIPLE OF WORK, SVP IS DIVIDED INTO THREE TYPES

• Chamber circuit: a centrally located fan blows air under the domed bottom into a special chamber that prevents air leakage.
• Nozzle scheme: the cushion is created by an air flow from an annular nozzle formed by a central part with a flat bottom and a "skirt". An air curtain around the ship's perimeter prevents air from escaping from under the pillow.
• Multi-row nozzle scheme: the cushion is formed by rows of annular circulation nozzles, each of which has a different level of generated pressure.

How hovercraft work

The movement of hovercraft is provided by:

• - propellers
• - horizontal nozzles, air into which is supplied from lifting fans
• - by trimming the hovercraft in such a way that the traction force appears.

During the arms race, the greatest danger was posed by American aircraft carriers. Of course, attack cruisers and nuclear submarines with cruise missiles existed to counter the aircraft carrier groups. But even the most powerful ships had few chances without capturing the straits and the adjacent coast. The Almaz designers were instructed to develop a hovercraft that could land armored vehicles and marines at high speed. As they say, the most important task of which is to capture and hold the Bosphorus Strait, for the Black Sea Fleet to enter the operational space (probably this was the case during the Soviet era). By that time, the Central Design Bureau had only experience in creating a small experimental boat MS-01 with a displacement of 20 tons - it was required from him to switch to a ship with a displacement of 350 tons. In parallel with the design work, research was going on: it was necessary to master new technologies and materials, develop transmissions, fans, light gas turbine engines. There have not yet been methods for calculating the speed, stability, maneuverable elements, the method of forming an air cushion - nozzle or chamber - has not been chosen.

Landing ships project Jeyran the world's first serial hovercraft, landing on the Volga coast

The braking system of the SVP, like the traction system, is "tied" in the air. To improve the stability of the vessel, vertical stabilizers are used, the same as on airplanes. For the first time, it was decided to use flexible rubber fences invented in England and designed to increase the seaworthiness and amphibiousness of the ship. After testing models built according to two different schemes, the Jeyran was developed: an air-cushion ship for landing two tanks on an unfurnished coast - no one else in the world has ever had such a thing. In 1970, the ship was delivered.

landing on the Volga coast from the Kalmar-type DKVP

AMPHIBIAN LANDING KVP "JEYRAN"

• Armament: two 30-mm AK-30 mounts
• Airborne capacity - 4 PT-76 tanks and 50 marines or 2 medium tanks and 200 infantry
• Displacement - 360 tons
• Speed ​​- 48 knots (over 100 km / h)
• Cruising range at full speed - 300 miles. Crew -21 people.

Almost at the same time, the Skat assault boat appeared: it carried 40 paratroopers in full gear, moved at a speed of 50 knots, and easily walked in rough seas of five points. At that time, an aggravation of the situation on the Soviet-Chinese border began, and "rays" were used not only in the Baltic and the Black Sea, but also on the Amur. In addition, four boats were converted to rescue astronauts in case they land on Lake Issyk-Kul.

Stingray landing hovercraft project 1205

The study of the capabilities of air-cushion ships stimulated the emergence of new models: the landing squid, the KVP fire support of the Killer Whale, the Murena, which combined the functions of the Squid and Killer Whales.

The landing of the landing is that the near Serna, the distant Squid

But in terms of seaworthiness and the amount of equipment transported, there was still no equal to "Jeyran". The accumulated potential made it possible to talk about the development of this project with an increase in capacity, speed, weapons and overall reliability.

"ZUBR" - THE WORLD'S ONLY AMPHIBIAN SHIP WITH IMPACT WEAPONS.

BISON LANDING SHIP ON AIR CUSHION PROJECT 12322 photo

This is how the idea of ​​the Zubr appeared - the world's only amphibious ship with shock weapons, which was handed over to the Navy in 1988.
Hovercraft bison designed to receive from the shore (not even equipped) amphibious assault forces with military equipment, transport by sea, landings on the enemy coast (one "bison" delivers a battalion of marines to the shore, which can "without getting their feet wet" immediately join the battle) and fire support landing troops. For this vessel, which calmly overcomes ditches, trenches and swamps, up to 70 percent of the total length of the coastline of the seas and oceans of the world is open.
OUTSTANDING THIS SHIP makes it a unique combination of payload, amphibiousness and speed. On tests, it was accelerated to 70 knots (about 130 km / h). At high speeds, the flexible fence breaks down, and the ship "bites its nose", but in this case, there is a blocking of critical modes in terms of speed and turning radius. Management requires such care and precision that "ZUBRE" NO STEERING - THE COMMANDER FULFILLS HIS RESPONSIBILITIES.

Bison photo, landing

Launching any ship is a difficult and time-consuming process. For example, the Zubr's characteristic screws are enclosed in attachments, which increases the thrust by one and a half times. And the nozzle - a construction sawn out of plastic with a diameter of 7 meters - is quite slender. In the first tests, they broke: for the required addition in thrust, the gap between the propeller and the nozzle must be very small, and if the propeller vibrates, it may cause interference. Imagine how long it took to finish this seemingly simple knot.

SCREWS "Zubr" - a dangerous combination of power and fragility, 10 thousand horsepower, diameter 7 meters

In terms of technical potential and tactical and technical elements, "Zubr" still has no equal in the world, and therefore is in demand by foreign customers. This often requires the creation of "export" modifications: for example, in the case of Greece - because of the need for tropicalization. So we can say that the development of the project continues. In the early 2000s, a "bison" built for Greece was tested, the ship accidentally crushed ... a truck. He served as a lighthouse on the shores of the Gulf of Finland, but because of the extinguished headlights, it turned into an invisible obstacle.

Armament of the Bison two 30-mm installations

Hovercraft Bison SVP

• Armament:
• - to destroy aircraft and ship missiles - two 30-mm AK-630M installations ("metal cutters");
• - to destroy coastal fortifications - two MLRS MS-227 (sea analogue of the Grad rocket system),
  Airborne capacity:
• - 3 T-80 tanks and 80 marines
• -10 armored personnel carriers or 360 infantry
• Displacement - 550 tons
• Full speed - 60 knots. Carrying capacity - 150 tons
• Engine power - more than 50 thousand liters. with
• Cruising range at full speed - 300 miles. Crew - 27 people.

One of the differences from foreign ships is a welded structure. The first hovercraft (according to aviation traditions) were made riveted, but their operation at sea showed the unreliability of such a connection. Although with a welded structure, the risk of cracking is higher. Due to the high power on such ships, the vibration level is increased: three engines of 10 thousand horsepower only for movement, two more engines of the same power work as superchargers. 50 thousand "horses", and all this in a displacement of 550 tons! One can imagine how high their power-to-weight ratio is in comparison with conventional ships.

Photo MLRS MS-227 marine analogue of the rocket system "Grad"

High-temperature gas turbine gear units were created to drive propellers, blowers and other consumers. The air purification system ensures long-term operation of gas turbines at sea salinity up to 30 ppm.
The lack of direct contact of the steering gears with water in the hovercraft makes it difficult to maneuver and makes the vessel dependent on the weather. Therefore, various control schemes have been developed, including aerodynamic and jet rudders (jet nozzles), variable pitch propellers.

Zubr project 12322 small landing ship Evgeny Kocheshkov and Mordovia, landing

Alas, in the modern Russian military doctrine, such a powerful ship has not yet been used - apparently, Tohovercraft Jeyran and Bison SVP ahead of its time. However, hovercraft are in high demand in the global arms market.

A logical prospect for amphibious SVPs is Zubra-class ships for inland seas and landing craft for large landing ships. But there are other areas of their application.
SVP SPEED is ideal for "mosquito fleet" - maneuverable warships. When it became possible to place torpedoes and missiles on small ships, the light boat became dangerous for large warships. It cannot be booked, which means that the salvation from enemy fire is speed. At the same time, it is difficult to make a high-speed small displacement ship. So, THE FIRST ATTEMPTED TO SUPPLY TORPED AND ROCKET BOATS ON THE AIRBAG: "clean" torpedo bombers were then at a dead end (they could not approach a large ship within a salvo range), and the missile carriers could not keep up with the growth of missiles.
There are also developments of "anti-submarine" SVPs, but they have not yet been implemented: today the main thing is not to destroy the submarine, but to find it. And this requires a powerful sonar system, that is, additional weapons.

The amphibious compartment of the ship, inside view

There are civil customers - of course, their interest concerns more utilitarian ships. Another feature is all-season. Amphibious ships can also walk on ice - it is even easier for them (when moving above water, a response pit is created under the pressure of the ship, which gives resistance). This is especially useful on freezing rivers and marshes of Siberia.
When the small boat "Breeze" was shown on television, customers - the developers of Siberian oil, who find it difficult to get to the oil fields - flocked to the Central Design Bureau "Almaz".

landing ship bison pr 1232.2 1989

Let's not forget about the amateur fleet: hovercraft amphibians are a versatile off-road vehicle that is often used for hunting and fishing. With them there is no need to moor - go ashore, turn off the engine and go ashore, and you can launch the ship from almost any shore.

Photo conveying the scale of the ship, For ships weighing about 100 tons, the power-to-weight ratio is 25-35 kilowatts per ton, for even heavier ones - 15-20 kilowatts

A similar situation is at the gas and oil fields in the Barents Sea. It is not out of place to recall the huge coastline in the North: the revival of the Northern Sea Route is associated with a very complex issue of moving goods to the coast. Almaz, on the basis of its amphibious ships, has already designed reloading boats for the Northern Sea Route: such a boat approaches the side, the cargo is lowered onto it, and soon it finds itself on the shore.

The landing party did not even wet their feet, with them there is no need to moor - go ashore, turn off the engine and go ashore, and you can lower the ship from almost any shore

It WOULD LIKE hovercraft are versatile. What is holding back interest in them? The obstacles to flying ships are energy and economic in nature. With the same mass as the displacement vessel, the AIR CUSHION APPARATUS DEMANDS MORE FUEL CONSUMPTION - BECAUSE IT SHOULD MOVE NOT ONLY FORWARD, BUT ALSO UP. Engines for KVP are powerful and light, which means they are expensive, low-resource, and difficult to manufacture. There are conventions in the production of any equipment, but the use of hovercraft is advisable only where these conventions are overridden by advantages - speed, amphibiousness, and the absence of an underwater part.
AIRBAG EFFECT is applied in other areas as well. The Americans have designed a "flying" transatlantic passenger ship, car manufacturers are creating cars on the VP. And the London Institute of Orthopedics uses a bed for patients with severe burns, who "lie" on an air cushion.

Hovercraft are being built by Russia, England, Japan, USA, France. Hundreds of such ships carry millions of passengers on scheduled services in the English Channel, the Irish Sea, the Mediterranean coasts of France and Italy, Canada, the United States and the Caribbean, as well as Japan and Australia. Most of the hovercraft have a capacity of up to 100 passengers, but since 1968 the 5K4 type vessels have been in operation, accommodating 254 passengers and 30 passenger cars. These vessels cross the English Channel in 40 minutes.

The Hovercraft company handed over to the customer a cargo and passenger hovercraft, built under the supervision of the River Register, in the small size category * 3.

Appointment. The cargo-passenger amphibious hovercraft of the "Neptune 23GrPasMl" type is designed to carry cargo in the amount of no more than 1700 kg or passengers in the amount of 6 people and cargo no more than 1250 kg.

Acceptable areas of operation. The vessel can be operated in coastal sea areas and inland water basins. Operational limitations - wave height of 1% coverage up to 1.2 m, distance from the shelter no more than 11 km (6 miles). The place of refuge is any piece of land, bay, ship in the roadstead, where the ship can hide from bad weather.

Operation period. The vessel can be operated all year round. Surface type: - on the water surface without depth limitation; - in shallow water, including at zero depth and shallows; - on a frozen and snow-covered surface of water bodies, in the absence of hummocks along the route that exceed the height of the air cushion; - on ice slush and floating ice; - on a watered marshy surface and in rare thickets of reeds with a height that does not obstruct the view for driving. It is allowed to exit and move the vessel on unconstrained areas of the flat coast. When driving on ice or snow-covered surface of water bodies, there is no restriction from the place of refuge.

Temperature conditions. Operation is permitted at an outdoor air temperature from minus 40 ° C to plus 40 ° C.

Wind restrictions. The wind speed is limited to 12 m / s.

Time of day restrictions. The vessel can be operated both in daylight and in the dark. When operating in the dark, additional lighting is installed (headlights-high beam spotlights).

Architectural and constructive type. SVP amphibious type with a two-tier flexible fence around the entire perimeter, a separate lifting and propulsion system with two double centrifugal blowers and two variable pitch propellers in aerodynamic nozzles, with aft engine compartment, with simplified hull shapes, with five watertight bulkheads.

Norms and Rules. Hovercraft was developed for compliance with the requirements of the "Guidelines for the Classification and Survey of Small Vessels" R.044-2016 of the Russian River Register and "Technical Regulations on the Safety of Inland Water Transport Facilities" Resolution of the Government of the Russian Federation of 12.08.2010 N 623 (as amended on 30.04.2015) ...

Main dimensions:

Payload composition for the carriage of cargo and passengers:

Fuel consumption. Fuel consumption when driving in calm water with an operating load at a speed of 40-45 km / h is about 30 l / h. The specific consumption under these conditions is 0.6-0.8 l / km.

The location of the cargo. The cargo is placed on the deck. The deck is located between the saloon and the fuel compartment. The deck measures; length 4.0m, width 2.0m. The possibility of covering the deck with an awning is provided. The deck is equipped with cargo securing brackets. The deck has an anti-slip surface and it is possible to increase the width of the cargo area by hinged sections. The total deck area will be 4 × 4sq.m. In the area of ​​the deck on the hinged sections, a removable railing is installed.

Travel speed. Hovercraft with an average, operational load has in calm calm weather: maximum speed on water - 65 km / h maximum speed on an ice surface 75 km / h Operating speed. The operating speed on water is 40-45 km / h, on a dense snow-covered surface 50-60 km / h.

Amphibious qualities. The amphibious qualities of the hovercraft are provided by the separation of the body from the screen due to the holding of an air cushion under the body by a flexible fencing. Lift height depends on blower (engine) speed, load and travel trim angle. The maximum achievable height of the air cushion is about 0.75 m. The height of the air cushion is measured from the supporting solid surface to the bottom of the hull.

Flexible fencing. To form an air cushion on the ship, a flexible fencing is provided along the entire perimeter. Two-tier flexible fencing, consisting of an upper tier - a receiver and a lower tier - removable elements. In a flexible fence, an internal contour is provided, consisting of longitudinal and transverse inflatable keels. The material of the flexible fence is a rubberized fabric based on nylon textile.

Frame. General information. As the material of the main body, set, foundations, sheet and profile rolled products from aluminum alloys are accepted. Flat products are used of the Amg5M brand, GOST 21631-76. Profile rolled products of the Amg6M or D16T grade in accordance with GOST 8617-75.

The felling. General information. The deckhouse is made of fiberglass and has an aerodynamically streamlined shape. The deckhouse is made of a three-layer structure, the middle layer of which is insulation. The outer layer is made of fiberglass based on polyester resin with reinforcing material made of fiberglass. The middle layer is made of tiled foam. The inner layer is made of fiberglass, pasted over with sewing - pile fabric.

Main engines. It is planned to install two Cummins automobile diesels of ISF2.8 brand as main engines - four-cylinder in-line vertical cylinders, turbocharged, with intercooled charge air, with common rail fuel injection. The maximum permissible speed is 3200 rpm. The main characteristics of each engine: maximum power, kW (hp) - 110 (149.6); number of cylinders, pcs. - 4; volume of cylinders, l - 2.8.

Fuel system. The fuel system consists of two fuel tanks with a capacity of 200 liters each.

Transmission. The hovercraft has two power units that distribute engine power to the supercharger and to the propeller. The power unit includes flat-toothed drive belts, pulleys with shafts mounted in bearings. The hovercraft has two independent transmissions on the left and right sides, each of which on its side transmits torque from the power unit to the propeller and the supercharger. The transmissions include cardan drives.

Movers. As propellers on the hovercraft, two variable-pitch propellers in aerodynamic fixed nozzles are provided. The support unit of the variable pitch propeller and the reverse mechanism are located in the pylons of each nozzle. The propeller blades are made of fiberglass coated with aramid fabric (Kevlar). The angle of rotation of the propeller blades is controlled by electric pedals and controlled by direction indicators installed in the control panel.

Air cushion blowers. Two twin centrifugal blowers are provided as air cushion blowers. The air cushion blowers operate separately, each on its own side. The blowers are mounted on shafts supported on both sides by self-aligning bearings. The material of the blowers is fiberglass with the addition of carbon and aramid fabrics (carbon and Kevlar).

Transportation. Transportation by road is provided without restrictions in the size of 2.5 m. Shipment is provided in 40HC container. At the same time, the dismantling of the side hinged sections, nozzles with rudders hung on them and the propeller pylons is carried out. Disassembled products are shipped separately in a 40-foot container or by road.

At the end of the 19th century, many engineers and inventors began introducing new ship designs into practice. It soon became clear that the best way to overcome the natural resistance of the water and, therefore, increase the speed of the vessel, is to eliminate the friction of the vessel's hull against the water by lifting it entirely above its surface during movement. In addition, for the convenience of passengers, it was necessary to develop vehicles that exclude the possibility of constant impact of waves on the ship's hull.

The first experiments carried out by such inventors as Porter, Hans, Deneson, Tomamhul, Forlanini, Crocco and others, marked the birth of two completely new types of ships - hovercraft and hydrofoils. The hovercraft rises entirely above the surface of the water through the action of either a static or dynamic air cushion. The HVC moves due to the difference in hydrodynamic pressure arising on the upper and lower planes of the hydrofoil during its movement through the aquatic environment. Both types can be technically implemented on different ships, so it is not surprising that disagreements often arise when assigning SVP and UPC to a certain class. Nevertheless, each project has its own distinctive features.

Hovercraft

There are two main types of apparatus using the proximity of the supporting surface. Some of them move above the surface, with the help of a static air cushion they themselves create, while others, when moving, receive aerodynamic lifting force like an aircraft, but a dynamic air cushion is formed under the hull.

There are two schemes for the formation of a static air cushion:

1. Chamber, when air is supplied directly to the dome space;
2. Nozzle when it is fed through nozzles located around the perimeter.

In the chamber scheme, the simplest from the concepts of the proximity effect of the support surface. Air is pumped directly into the bell-shaped or inverted pudding bowl under the dome, where it creates a compressed air cushion that lifts the boat above the surface to a predetermined hover height. Air is supplied to the dome space in a volume sufficient to compensate for its losses as a result of leakage from the bottom of the vessel. Modern chambered air-cushion vessels have a flexible canopy of elastic material that sags between the hull and the surface to provide greater clearance over obstacles or waves.

Modern hovercraft

Among the vessels created according to this scheme, it should be noted the SVP with skegs, in which the air cushion is held by rigid side walls or keels and transverse flexible fences in the bow and stern and the SVP of the "Naviplan" type designed by Bertin and the "Terraplan" platforms, which have a multi-chamber formation scheme air cushion, consisting of many dome-chambers, each of which is equipped with a light flexible enclosure. Due to the relative simplicity of the design, ships with a chamber air cushion formation scheme, equipped with a flexible fencing, were preferred by enthusiasts of light hovercraft, especially those who are engaged in the design and construction of such devices at home.

There is a type of SVP, in which the air cushion is formed according to a nozzle scheme, developed on the basis of the original principle put forward by Christopher Cockerell. In this case, an air cushion is created and held by continuously supplied jets of air, which are ejected through nozzles located along the outer perimeter of the base of the ship's hull. Flexible barriers, which are equipped with this type of ships, can have the form of an extension, either only the outer walls of the air ducts, or both internal and external.

Depending on the principles of aerohydrodynamic layout, ekranoplanes are made according to the “flying wing” and airplane schemes. In the first case, the body of an ekranoplan is usually a low aspect ratio wing, on the sides of which end washers-floats are installed. When moving as a result of the high-speed air pressure, an aerodynamic lift is generated on the wing. The hull and the entire glider, including the tail unit of an ekranoplan made according to the airplane scheme, as a rule, resembles an ordinary one or two hull seaplane (flying boat). The main feature of an ekranoplan, which distinguishes it from an aircraft, is that its aerodynamic and structural configuration provides the ability to fly the vehicle at a low altitude from the screen (water or ground surface).

At the same time, the aerodynamic quality is significantly increased, which in turn leads to a decrease in fuel consumption and thereby to an almost double increase in the flight range and payload of the ekranoplan. The advantages of flying using the proximity effect were proven 50 years ago. Then this effect helped the pilots of the first civil aircraft to increase the flight range when crossing the regions of the South Atlantic. During the Second World War, pilots of the Royal Air Force and the British Transport Aviation often resorted to his "services" when returning to their native shores, especially if the fuel was running out or the plane was damaged.

One of the leading designers of this class of vehicles is Dr. Alexander Lippish, the “father” of the delta wing and the creator of the fastest fighter during the Second World War - Me-163. A characteristic feature of the design of the Aerofoilboat X-112A ekranoplan, made according to the aircraft scheme, is that by using an inverted V-shaped wing, it was possible to eliminate keel instability - one of the main problems for everyone who flew close to the surface, especially on aircraft with conventional wings, at the time of approaching the surface. A normal phenomenon in aviation is a shift in the center of pressure towards the tail of the vehicle, which leads to a tilt of the nose when moving. Dr. Lippisch's design is different.

Hovercraft ekranoplan

Its ekranoplan, thanks to a well-chosen tail assembly and wing shape, demonstrates reliable flight stability. Its stability is such that, if necessary, it can fly over the screen or free flight at almost any height, and then return to the flight mode above the screen. This allows him to overcome high banks, coastal or port facilities, river meanders, bridges, etc. However, when leaving the zone of action of the screen, the economic advantages of the ekranoplan are lost, since for free flight and maintaining altitude, it is necessary to increase the power of the engines, and thereby also the fuel consumption.

Flexible fences

If flexible fencing had not been invented, the idea of ​​creating a hovercraft would hardly have progressed far from the stage at which it was treated as just an interesting technical novelty. Thanks to the use of flexible barriers, the height of the air cushion at a given lift has increased tenfold and the size of ships intended for operation in rough seas has decreased by 75%. The resulting economic benefits are perhaps best illustrated by comparing the dimensions of the flexible barreled vessels with the non-boarded vessels that would be required to service a line across the English Channel, where wave heights often exceed 2 m. a clearance of 2.2-2.4 m, the required dimensions and engine power would be approximately 700-800 tons.

The use of fencing on the modern SR.N4 hovercraft allows its weight to be reduced to 200 tons. In addition, for a larger vessel without flexible fencing, the engine power would be 54.4 thousand liters. s., that is, four times more than the four gas turbines "Marin Proteus" at the SR.N4 hovercraft provide. The leading firms in the design and manufacture of flexible fencing for hovercraft are FPT Products Limited, a subsidiary of British Hovercraft Corporation, Hovercraft Development Limited, and Eyvon Rubber Company. After the first tests of the simplest types of flexible fencing in the form of a rubber cavity, British Hovercraft Corporation in 1965 decided to switch all research activities to the development of a type of fencing, based on the so-called two-tier flexible fencing with segmented elements.

In such a system, compressed air from the lift system blowers first enters the flexible receiver, and then through the nozzles into the area under the bottom of the vessel, which leads to the formation of an air cushion. At the base of the flexible receiver, below each nozzle, there is an open-ended segment element through which air is directed inward towards the center of the air cushion zone. Initially, segmented elements were used to eliminate spatter and reduce drag when driving on the open sea. But they significantly prevent wear and tear on the entire flexible fence, and because they can be easily replaced, they help to reduce operating costs.

Drawing of flexible fencing on SVP

Initially, the height of the segmented elements in relation to the height of the entire flexible barrier was approximately 30%, over time this ratio increased to 50%. In accordance with the initial designs, vessels such as SR.N4 and SR.N6 were operated with a 1.5 ° stern trim, with a slightly raised bow, which reduced the possibility of a sharp decrease in speed in the event that the bow of the flexible barrier "raked" water. As a result of this mode of operation, the aft segment elements had significantly more wear than the bow ones. They withstood operation for 100 hours, while the nasal ones - about 500 hours.

Largely thanks to research undertaken by British Hovercraft Corporation and British Rail on the SR.N4 and SR.N6 ships, a new tapered flexible boom was introduced in 1972. Its height at the bow end was increased by approximately 75 cm, which made it possible to maintain the necessary trim of the vessel, and then it decreased to normal at the stern end. This meant that the vessel was now sort of “planted” on a fence designed with a 1.5 ° C stern trim. As a result of this improvement on both ships, there was a significant reduction in wear on the segmented flexible boom at the aft end. A noteworthy feature of the flexible barriers, designed by British Hovercraft Corporation, is the presence of stability nozzles in them, which improve the stability of the vessel.

The SR.N6 has two stability nozzles installed in the form of a flexible container:

1. Longitudinal keel;
2. Bisected crosswise.

On the much larger SR.N4, the airbag is divided into three compartments as the longitudinal stability nozzle is installed from the stern only to the transverse nozzle. Due to the division of the air cushion into compartments, a relatively high stability is achieved against pitching and rolling, which in turn prevents unnecessarily prolonged contact of the fence with the water surface. Under certain unfavorable conditions, the bow of the flexible guard can come into contact with the water surface, due to which the braking is gradually increased, and then a "burying" by the nose can occur. Failure to anticipate this will result in a sharp decrease in boat speed, known as “plowing,” and this can result in severe loss of stability and possibly overturning moment.

Since the outer edge of the bow of the flexible guard is stretched towards the center of the vessel (referred to in terminology as “bending”), there is a sharp decrease in the stabilizing moment of pressure in the air cushion. As the trim angle increases, the stern tends to rise above the surface, creating too much clearance. An abrupt significant drop in speed occurs, and in small vessels, in addition, the danger of overturning increases, under the influence of passing waves, which increase the pitching angle.

In order to facilitate the solution of the problem of "bending" and "plowing", the British Hovercraft Corporation proposed to raise the line of attachment of the flexible barrier on the vessel SR.N4MK.2 and boat VN.7. In the first one, the anti-bending system is attached to the bow of the flexible guard. This system provides the necessary resistance to the action of the water surface and prevents "buckling" and "plowing". The bow flexible guard on the VN.7 boat deforms when it comes into contact with water, thereby delaying the occurrence of "bending" and providing a restoring moment. Vessels of the SR.N4 type are operated at wave heights of more than 1 m and a speed of 50 knots and more.

Hovercraft - "SVP"

The contact of the flexible barrier with the surface of the water, under such operating conditions, causes increased loads, similar to those experienced, for example, by car tires during off-road cross-country. The degree of wear of the segmented elements of the flexible barrier can be shown on the example of the experience of Hoverlloyd Limited, which uses three SR.N4 vessels for transportation between Ramsgate and Calais. Every year each hovercraft of this company is in operation for 4000 hours and during this time wears out 1500 segment elements. Their cost is the main expense item in the operation of the hovercraft, to which, of course, should be added, also the remuneration of specialists in the repair and replacement of segment elements.

Currently, research is underway on the properties of various materials and their processing technologies, which would improve the wear resistance characteristics of segment elements. Wear occurs mainly at high speeds. It reaches the highest level when the average sea state and the speed of the hovercraft are 50 knots. With a quieter sea surface, the impact of water on the segmented elements is less significant, therefore the degree of wear is reduced. The same thing happens with stronger waves, when the speed of the hovercraft is reduced to 30-40 knots. One method of solving the problem of developing better materials for flexible fencing is to use lighter, more flexible fabrics. There is evidence to support the theory that due to their flexibility, such materials have less braking effect when in contact with water.

One of the leading projects based on this theory is the Tilting Sectioned Flexible Fence developed by Hovercraft Development Limited. This type of flexible fencing is fitted to such hovercraft as HD.2, VT1 and VT2 from Vosper Thornicroft, EM.2 and many other new vessels that are under construction or are already in operation. This fencing is also used in industry, including for the equipment of heavy lifting platforms weighing up to 750 tons, transport and hovercraft trailers. Such a flexible fence consists of large open-type transversely dissected elements - segment elements connected to the body by means of an open loop. The cushion is not divided into separate compartments and since there are no obstacles to the air flow, when moving between the loop of the flexible barrier and the air cushion, the ratio of pressure levels in them is almost the same and therefore the loss of internal energy is negligible.

For the manufacture of flexible fences, a thin fabric is used and as a result of the low level of its inertia, a smooth movement of the vessel is ensured. Due to the fact that the segmented elements of the flexible fence occupy a significant part of its entire height, this system allows the vessel to overcome high waves and obstacles. Another advantage of using this system is that the bottom body on which it is applied has a surface that is tapered from the bottom to the sides. Thus, when the vessel is devoid of an air cushion, the internal connection points of the segment elements can be reached without resorting to jacks, which greatly simplifies the maintenance and maintenance of the flexible boom.British Hovercraft Corporation has concluded that the most suitable materials for manufacturing flexible fences are those in which the fabric is based on nylon, or terylene topped with natural rubber or neoprene rubber.

The tests were carried out on fabrics made of various materials, including glass, cotton, synthetic fibers and even steel, but the results were unsatisfactory. It turned out that steel and glass are unable to withstand the incessant impact of waves, and cotton fabrics and fabrics made of artificial fibers do not have sufficient abrasion resistance and cannot withstand long-term use. At the initial stage of the development of the flexible fencing system, substances such as RVK nitrile and polyurethane were also used for the flexible receiver. Flexible barriers make up about 15% of the total weight of the 10-ton SR.Nh GVG1 and 10% of the 200-ton SR.N4.

Military hovercraft

Also, to improve the operational and mass indicators, such sizes of flexible fences are usually chosen that meet the necessary requirements for the operation of the vessel. The width of the flexible barrier, as a rule, corresponds to the highest wave height in the area of ​​the sea where this vessel is to operate. Tests have shown that to ensure the stability of the vessel, the width of the flexible barrier should not exceed 15-20% of the width of the air cushion.

The overwhelming majority of hovercraft are capable of operating in conditions in which the wave height is at least twice the height of the flexible barrier, especially if the waves are long and can be overcome without the base of the hovercraft bow in contact with them. The largest manufacturer of SVPs in France is SEDAM, which holds a license to manufacture the devices of the "Naviplan" and "Terraplan" series under Bertin's patents. A feature of these projects is the use in them of the system of a plurality of injection chambers proposed by Bertin, for which the air comes from the blower of the lifting system, either separately for each one, or for entire groups of chambers.

The chamber has a separate flexible enclosure into which air is supplied through a nozzle. In turn, all of them are surrounded by a single peripheral flexible fence along the perimeter of the SVP body. The Perisell model, one of the latest developments in the field, combines the features of a flexible fence with segmented elements and a Bertin chamber system. In it, instead of a fringe or segmental elements at the base of a flexible container, separate large chambers are placed. This design has advantages over the segmented flexible boom system in terms of stability in hover stop mode. The SES-100A was one of the first SVPs to use this new type of flexible fence.

Power plants

The power armament of the hoisting and moving systems of the hovercraft depends on the composition of the equipment adopted in each specific project of the hovercraft size, the environment in which the ship will be operated and on the required tactical and technical indicators. In addition, there are other factors that should be taken into account by both those who build the SVP and those who exploits them.

Among them:

• Engine power;
• Mass of the vessel;
• Fuel consumption;
• Service life before overhaul;
• Estimated cost of ownership;
• Possibility of providing spare parts;
• The scale of the supply resources available to the manufacturer of engines for hovercraft.

The power plants of modern hovercraft can include various types of engines - from converted radio-controlled, outboard, motorcycle gasoline engines, to four Rolls-Royce Marin Proteus gas turbines with a capacity of 3600 hp used on the SR.N4. with. (2600 kW) each. Among these extreme examples is the 200 hp Chrysler V8 car engine. with. (147 kW) on a six-seat hovercraft SH-2 by Sealand, three water-cooled diesel engines of the Cummins system on the HM-2 ships of Hovermarine and a gas turbine with a capacity of 900 hp. with. (660 kW) "Marin Gnoum" on 58-seater sea passenger ferries of the SR.N6 Mk.1 series.

To date, no manufacturer has provided orders for engines for hovercraft to such an extent that it would be possible to justify the design of special systems for this purpose. Therefore, as the propulsion systems of the hovercraft, at present, conventional standard designs are used, in which, as far as possible, the improvements necessary for operation in sea conditions are applied. In such engines, most parts and assemblies must be tested for resistance to corrosion, which is the inevitable consequence of exposure to salt-saturated sea air.

A gas turbine vessel designed for offshore operation is fitted with thick, loosely woven metal or plastic fiber filters that are placed in the engine air intakes to remove water and particulate matter from the air. As an additional measure against the ingress of salt and sand particles into the engine, air intake for the engine, directly from the blower chamber of the lift system, is commonly used.

Soviet passenger hovercraft

On most ships weighing 8-10 tons or more, manufacturers prefer to install a gas turbine engine that has the best power-to-speed ratio and mass per unit of power (kg / hp). However, many transport workers in developing countries would choose, instead of a gas turbine engine, a conventional diesel engine, since its operation, fuel supply and maintenance of components are cheaper. In addition, it is much easier to find a qualified diesel engineer than a gas turbine engine.

Although some of the modern high-speed light diesel engines are quite acceptable for small passenger and combat aircrafts, weighing up to 25 tons, still the main engines for larger ships remain various gas turbine models developed on the basis of aviation. Designed for the needs of the US Navy, the 2000-ton SES-class apparatus will be equipped with six LM-2500 gas turbines by General Electric with a capacity of 20 thousand liters each. with. (18.4 MW) each. Two of these transmit power to the lift system blowers, and four to the jet propulsion system. These turbines are among the most powerful gas turbines in the world, however, four times as much power will be required to power the propulsion devices alone on the next generation SES-class ships, the total mass of which will be about 12.5 thousand tons. It is calculated that these ships, while overcoming the hump of resistance to movement at a speed of 42 knots, will need a capacity of about 515 thousand liters. with. (290 MW).

High travel speed and long range can be achieved with a significant amount of power. Factors such as increased requirements for the quality of fuel and its high cost forced the United States government to start exploring the possibility of using it in large skeletal KVP nuclear power plants. Much of the research to date has been conducted in Cleveland, Ohio, at the National Aeronautics and Space Administration (NASA) Lewis Research Center, led by Frank I. Rom.

Nuclear propulsion systems developed by NASA for use on SES-class spacecraft must be identical to systems designed for aircraft. In the reactor, surrounded by a casing and a protective baffle system, a liquid (for example, helium) is heated under high pressure, which is piped into a heat exchanger located between the ramjet engines and the compressor of a typical turbofan engine. In this case, the engine can run on thermal energy supplied through a heat exchanger or as a result of fuel combustion in conventional chambers.

To ensure absolutely safe operation of the reactor, various protection measures were considered in detail. The shell surrounding the reactor is designed in such a way as to completely prevent the release of nuclear fission products, which could occur in the event of a serious accident or destruction of the reactor. And the materials chosen for the manufacture of the protective screen should, according to the project, not only withstand impact from contact, but also evenly distribute the heat accumulated during melting. Since the cost of nuclear fuel is only about one-third or one-sixth of the cost of chemical fuel, there are significant savings. Now it has become possible to build reliable reactors designed to operate without loading for 10 thousand hours.

Military small hovercraft

Another attractive feature is that large ships of the SES class, the mass of a nuclear power plant, will be less than 10% of the mass of the entire ship, equal to 5-10 thousand tons. NASA experts believe that over time it will be possible to achieve a reduction operating costs, up to two cents per ton-mile. They argue that, in theory, an entire fleet of 1,500 to 10,000-ton SES-class vessels will need to be built, which will be used to transport 10% of the world's cargo turnover. Moreover, this 10%, according to the theoreticians' calculations, should be “assigned” to the SVP precisely because it will be possible to reduce the cost of their freight, down to two cents per ton-mile. The prospect of operating such vessels looks even more attractive than these figures show, given the possibility of the emergence of new trade routes, which will no doubt arise in connection with the low cost, plus a much higher speed of transportation.

Lifting systems

The lift system blowers are tasked with providing the hovercraft with air for its air cushion. Blowers are often thought of as the heart and lungs of these vessels, as the TDS is essentially a blowing system designed to lift and move certain loads. The blower continuously delivers a significant amount of compressed air below the bottom of the boat, where it dissipates and forms an air cushion, which then lifts the boat off the surface and keeps it stable. The amount of air entering the cushion should be sufficient to replenish the air that flows outward along the perimeter of the SVP. Currently, there are mainly two types of blowers in use. As a rule, the larger the vessel, the greater the air flow rate into the cushion and the higher the pressure in it, although much depends on the design, weight and purpose of each individual apparatus.

The smallest modern amphibious passenger hovercraft requires an air cushion pressure of 10-15 lb / ft 2 (44-66 kg / m2) and an air flow rate of 100-200 ft 3 / s (2.8-5.6 m 3 / s), and the largest hovercraft - 60-70 lb / ft 2 (260-310 kg / m 2) and air flow up to 27,000 ft 3 / s (760 m 3 / s).

Lifting systems:

• Axial;
• Centrifugal.

Although the use of a mixed system, combining features of both types, was also successful in some cases. An axial supercharger, like a conventional aircraft propeller, drives air in a direction parallel to the axis of rotation, while a centrifugal supercharger captures air between the blades and then expels it through centrifugal acceleration outward in a radial direction. Axial blowers are mainly used in vertical duct systems. They direct the air flow downward, directly into the air cushion.

The relative simplicity of their design and the availability of construction have led to the fact that they are willingly used by manufacturers of small hovercraft with a chamber cushion formation system, especially by amateurs who build ships outside the factory. But due to the relatively low air flow rates, these blowers have to be operated at high speed, which leads to an increase in noise levels. Since on large ships the air must be distributed over the entire length and width of a rather extended receiver before entering the cushion, in this case there are significant advantages of a centrifugal blower. It provides a higher level of static pressure at a lower rotational speed, and also allows for increased air flow in the cushion. The centrifugal blower is simple in design, easy to install, and durable and reliable in operation.

Hovercraft scheme

Nevertheless, in their indefatigable pursuit of greater comfort and efficiency, the designers did not lose sight of the possibility of using several axial superchargers with variable pitch of the impeller blades on ocean hovercraft, and not only to provide air flow control of the lifting system, but also as means for controlling the horizontal movements of the vessel. An analysis of the entire spectrum of wave forces was carried out, after which it became obvious that, theoretically, in the low frequency zone, where most of the wave energy is found, it is quite possible to neutralize horizontal displacements by changing the pitch of the impeller, similar to how the pitch of the propeller is changed in aviation. ... The research results give reason to hope that the horizontal acceleration can be reduced by more than four times, and the movement of the vessel will meet the standards of comfort.

Movers

There are very few types of propellers that have not been tested on hovercraft, from sails to propellers and from propellers to water jets. The propulsion unit is selected taking into account the purpose of the vessel and the technical and operational indicators that it must possess. Air propellers of one type or another are usually installed on amphibious hovercraft, while water jets or propellers are more suitable for vessels designed to move exclusively over the water surface. Let us list the types of propulsion devices currently in use or proposed for use in the future.

Air propellers

• Air propellers;
• Propellers in the nozzle;
• Air-jet turbofans;
• Gas turbine jet sails.

Water propellers

• Propeller screw;
• Water cannon;
• Paddle wheel.

Movement in contact with the ground

• Wheels;
• Crawler;
• Pushing with hands;
• Towing by tractor;
• Horse towing;
• Helicopter towing.

Hovering over the rails

• Air propeller;
• Gas turbine jet turbofan;
• Linear induction motor.

Despite the abundance of proposed alternatives, more than 90% of modern hovercraft move with the help of propellers, and most of the rest of the vehicles use propellers or water jets. However, it seems that the tendency to use hydrodynamic propellers or hybrid systems is increasing, since if we calculate the propulsion system for a 10,000-ton skeg hovercraft, which should have a speed of 100 knots, it turns out that it will need to be installed on it, or 10 propellers with a diameter 18.3 m each, or 10 direct-flow turbofan propellers with a diameter of 10.5 m. with a diameter of 3.7 m each.

In other words, as the size of ships increases, the use of propellers in many cases is impractical due to the size of the propellers themselves and their foundations, while the use of hydrodynamic systems, with equal engine power, provides the specified characteristics, with quite real dimensions. A decrease in the diameter of the propellers leads to a drop in their efficiency due to a decrease in the mass of the air jet, which causes an increase in the required engine power.

Despite the fact that propellers are unacceptable as propellers for large hovercraft due to their size and number, they remain the most effective type of propulsion device for hovercraft, at speeds of 150 knots and above. However, with regard to technical and operational characteristics, propellers are inferior to water jets and propellers when operating at low speeds.

Hovercraft

Tests of another type of air propeller for a hovercraft - a propeller in a nozzle showed that such a propulsion device provides better technical performance at low speeds, but the nozzles themselves significantly increase the total mass of the vessel, and at a speed of more than 100 knots they increase drag, which significantly reduces the efficiency of the propeller. For a large high-speed vessel, perhaps the most promising is a system that uses direct-flow turbofan propellers at high speeds, in combination with semi-submerged supercavitating propellers, providing a speed gain of up to 70-80 knots and overcoming a hump of resistance.

The most important advantage of a direct-flow turbofan propulsion device is that, while the technical and operational characteristics are comparatively the same as for the propeller, the diameter of the fan impeller is twice as small. In addition, it is significantly lighter, has less noise and can be configured with a variety of different installations. With the development in the aircraft industry, the concept of wide-body airbus aircraft in the coming years will become possible, the production of various ramjet turbofan engines with a capacity of up to 40 thousand hp. (30 MW). SES class hovercraft have rigid side keelskegs, which are ideal designs for the location of water jet propellers or propellers and their drives.

Since the lower parts of the skegs are submerged in the water, providing stability and contributing to steady movement on the course, the thrusters are usually installed in the aft part of the skegs. The design speed of 100-ton vessels with US Navy SES-100A and SES-100B skegs was 70-80 knots. The SES-100A is the first water-powered hovercraft to achieve such high performance, and the SES-100B is the first semi-submerged supercavitating propeller to reach 80 knots.

Undoubtedly, both systems have significant potential for further development, but it is unlikely that the speed records they set can be surpassed in the near future, thanks to the use of more resistant types of metals and improved design. Nevertheless, the loss of their efficiency is almost inevitable. The use of a partially submerged supercavitating propeller with a drive in the transom of the skeg on the SES-100B was a new approach to solving the problem, since there was no need to install the propeller shaft, support legs and bearings, which created additional drag during movement. The efficiency of this type of propeller turned out to be the same as the efficiency of a completely submerged propeller, and the thrust and torque arising on it were proportional to the disk area of ​​the submerged propeller.

Propeller-driven installation on hovercraft

Among experts on marine propulsion there is an opinion that the creation of such supercavitating propellers with the help of which it is possible to achieve a speed of 100 knots or even more is a very real task. There are projects of wedge-shaped propellers, the profile of the blades of which has a sharp leading edge and a square trailing edge, which leads to the occurrence of cavitation on the upper surface and its disappearance far below, under the zone of rotation of the blades.

Another idea is a supercavitating marine propeller with variable blade curvature. If implemented, the same effect is expected as the use of variable pitch propellers on airplanes. By setting a certain curvature of the propeller blades, the helmsman could provide an optimal amount of thrust for the initial stage of reaching the air cushion, for movement at medium or highest speeds. The Hamilton Standard variable curvature propeller has blades that are segmented in the central part so that individual adjustment of both blade parts is possible.

Above 45 knots, the use of supercavitating propellers becomes essential. Even during the first tests of boats, on the hydrofoils of the US Navy, it was discovered that at a speed of 45-50 knots, the RSN-1 bronze stern propellers were eroded on both sides and needed to be repaired or completely replaced after 40 hours of operation. Since then, alloys have been used in which more resistant metals are used. The demand for titanium and its alloys is especially great, since they have high strength, high levels of cavitation and corrosion resistance. The first ships on which the improved propellers were installed were the HS Denison and the 320-ton AGEH-1 Plainview, which has two four-blade titanium propellers with a diameter of 1.5 m each.

Water-jet propellers

The use of a water jet as a ship propulsion system is one of the oldest technical concepts. The first patent for such a propulsion device was received by the British Thugood and Hayes in 1661. In 1775, this propulsion device was tested by Benjamin Franklin, and in 1782, James Ramsey first used it on a passenger ferry on the Potomac River, between Washington and Alexandria. The efficiency of the jet propulsion unit is lower than that of the propeller, so the work on its creation was not carried out intensively enough. For many years, the scope of water jet propulsion was limited to relatively inexpensive pleasure craft and amphibious combat boats, until in 1963 Boeing announced the creation of a gas turbine experimental vessel "Little Skirt".

The interest shown by Boeing in this type of propulsion system is mainly explained by the desire to create additional opportunities for the design of new ship propulsion systems as opposed to the supercavitating propeller and the extremely expensive Z-shaped transmission system, the use of which at the SPK during operation at high wavelengths was considered the only acceptable one. Little Skirt, equipped with a double suction centrifugal pump, achieved a high efficiency of the propulsion system, equal to 0.48, at a speed of 50 knots.

Hovercraft - "KVP"

Largely due to the interest shown by Boeing in water-jet propellers, the US Navy decided to consider such a propulsion device as an alternative option, using it on the SES-100A type hovercraft, for comparison with a supercavitating propeller. Although the program of research and testing of water-jet propellers ended with the creation of easy-to-use and reliable installations, difficulties arose due to cavitation in tubular connections and pumps, as well as the need to create water intakes with a variable area. Twisting of water intakes, rolling and pitching, as well as mechanical combination of water intakes in order to avoid cavitation, at speeds up to 80 knots - these are the problems that are constantly being studied in order to create a project for a skeg SVP with a movement speed of more than 100 knots.

Recently, considerable efforts have been directed to the study of another, long-known type of marine propulsion system for hovercraft - this is a paddle wheel. Its main propagandist is Christopher Cockerell. He is currently working on the creation of a water-rowing propulsion system that follows the contour of waves with a large surface area. It is specially designed for hovercraft. Thanks to the use of the “flange” design, the 20-foot (more than 6 m) paddle wheel, once installed on ships sailing the Mississippi, has been reduced to a modern design with a diameter of only 5 feet (about 1.5 m).

To support the propulsion of a 2,000 ton vessel, the total area of ​​the submerged blades must be at least 150 square feet (14 m 2). Christopher claims that his wheel can provide this area with a blade immersion depth of just 2 feet (60 cm), with the total width of all the components being in the order of 75 feet (about 23 m). The wheels will be positioned behind the boat on special levers, allowing them to follow the contour of the waves. Height sensors located in front of the wheels will generate impulses for the steering system. Of course, this is a very ingenious development with unique advantages. Among its attractive properties, it should be noted low noise level, shallow draft, the possibility of easy access to all units during maintenance.

Suggested reading:

Hovercraft - soaring ships - represent a fundamentally new means of water transport, which has a high cross-country ability and high speed. For them, speeds in excess of 200 knots are available; their operation is possible not only on shallow rivers with access to a gentle bank, but also in swamps, over ice, etc. Soaring vessels are of considerable interest both for water-motor sports enthusiasts and for tourists.

The design and construction of hovercraft is more complex than conventional displacement or planing boats. However, the experience of building small hovercraft by individual amateurs (both in the USSR and abroad) shows that this work is available not only to specialized design organizations and enterprises.

The main issues of design and construction of small hovercraft are considered below, and some theoretical issues are presented in a simplified form. The practical coefficients given in the article are derived on the basis of data obtained as a result of tests of domestic and foreign experimental vehicles, including an experimental hovercraft built (under the guidance of the author) by students of the Odessa Institute of Marine Engineers.

There are several ways to form an air cushion, but the experience of operating hovercraft is still insufficient to confidently give preference to any one of them. There are only approximate limits of soaring heights and speeds for which one or another scheme can be recommended.

Methods for creating an air cushion

Chamber way of creating an air cushion... As shown in fig. 1, the bottom of ships of this type is a dome, which is a chamber into which a fan blows air. The increased pressure in the chamber creates a lifting force. The equilibrium position of the apparatus occurs when the resultant of the pressure forces balances the weight forces, and the fan performance compensates for the outflow of air from under the dome.

However, the chamber scheme in this form cannot be applied to the vessel, since it does not provide one of the main seaworthiness qualities - stability. This drawback of vessels built according to the chamber scheme can be eliminated by the device of side floats (Fig. 2), as in a catamaran, or by sectioning the bottom (Fig. 3) with longitudinal walls (along the sides and at least one in the gap between them) with simultaneous installation cross clap.

Thanks to the installation of longitudinal walls - "knives" and a pop (1, 2 in Fig. 2), the energy consumption for creating a pillow is significantly reduced. However, knives at high travel speeds cause significant resistance to movement, therefore, this type of vessel is designed for travel speeds not exceeding 40-60 knots.

In fig. 4 and 5 show apparatuses with a chamber air cushion formation scheme (the characteristics of a number of apparatuses are given in Table 1).

Nozzle method for creating an air cushion... The air from the fan flows through the corresponding channels to the nozzle arranged along the perimeter of the vessel (Fig. 6). The annular nozzle is designed so that air is directed under the bottom of the vessel at an angle to its center, forms an area of ​​increased pressure and creates an air curtain.

The power spent on creating an air cushion is less for ships of this type than for similar ships with a chamber scheme (without knives). Stability is provided only at small angles of inclination (up to 2 °), therefore, to improve stability at large angles of roll, two rows of nozzles or a sectioned bottom (with baffles or longitudinal and transverse nozzle devices) are arranged.

The nozzle scheme is preferable for vessels with complete separation from the water surface and with higher speeds than with a chamber scheme (up to 60-80 knots).

In fig. 7-13 show apparatuses having a nozzle scheme.

Air Wing Ships... In ships of this type - ekranoplanes - the lifting force is created on the air wing due to the high-speed pressure of the oncoming air flow (Fig. 14). These vessels can also have a combined method of creating an air cushion: the lift of the vessel without movement is created by fans, and when a certain speed is reached, the fans are turned off, and soaring is carried out on the wings.

The lift of the wing at the support surface is much greater than at a distance from it. The soaring height of aircraft on air wings is provided such that it exceeds the height of the wave crests, and the speed is sufficient to create a lifting force that provides the indicated soaring height. The speed range of these vessels is from 60-70 to 250-300 knots.

Recently introduced air-wing aircraft are simpler than the first two types or ships with a combined design. Their total energy consumption for lifting and movement is less, and the possibility of achieving high speeds is much greater.

In fig. 14 and 15 show apparatuses of this type. They represent a wing inclined to the horizon at an angle of 10-15 °, with side fences (washers). In the front part of the wing there is a propeller, the axis of which is also tilted. The propeller blows air under the wing, which makes it possible to raise the boat above the water surface while at rest. When moving, the hover height reaches 10-15% of the wing chord.

The inclination of the vehicle in the longitudinal direction is carried out by a special rudder installed in the plane of the wing. Agility is provided by vertical rudders.

At present, the exact calculation of ships of this type has obviously not been theoretically developed, but the simplicity of their designs allows, in most cases, to carry out experiments on models on their own and to obtain the basic initial data for calculations.

Some of the basic theoretical considerations and practical data required for the design of hovercraft, discussed below, will only apply to chamber and nozzle types.

Apparatus "Chaika"

The completion of the "Chaika" apparatus was completed at the end of the summer of 1963. Its tests above the ground (in the courtyard of the Institute) showed satisfactory qualities in terms of controllability, stability and speed. However, the too low hover height - only 4-5 cm - and the overheating of the engine above the fan did not allow testing it in the sea conditions of the autumn period.

It was supposed to be finalized in 1964, but the absence of a more powerful engine (for a fan to increase the soaring height) caused the termination of work on the conversion of the "Chaika" into a ship. The search for new ways began.

In the winter of 1963-1964. a new project was developed and a model of a more promising variety of air cushion vehicles with low power engines was tested - a vessel on an air wing.

In spring, together with the students, we built such a single-seat apparatus and carried out some tests of it not only in the yard, but also at sea. We have made sure that on the basis of the same two IZH-60k motors, it is possible to obtain significantly higher characteristics, and in particular, a speed of the order of 100-120 km / h with a hovering height of 20-25 cm.

Structurally, the new ekranoplan apparatus is designed in the form of a catamaran with a wing-shaped deck. At the end of the refinement and testing, which will obviously take place in the spring or summer of 1965, we will tell you more about this device.

Selection of the main characteristics of the vessel

Hover height... One of the main tasks in the design of a hovercraft is the choice of a rational hover height. The soaring height determines the passability of the vessel over a hard surface that has certain irregularities, and, naturally, should exceed their height.

Movement on an agitated water surface can be carried out both in the conditions of the ship's hull hovering above the wave crests, and when the hover height is less than the wave height. In the latter case, the movement is accompanied by the impact of waves on the ship's hull, which leads to a loss of speed. The decrease in speed will be the greater, the more the wave height exceeds the soaring height; if the wave height exceeds the soaring height by 1.5-2 times, the speed loss can be 20-30%. Operation of hovercraft is possible even in conditions when the wave height exceeds the soaring height by a factor of 4 or more, but the loss of speed in this case will be quite significant (about 50%).

Achieving a soaring height that would provide movement over the crests of waves at a significant height will require large energy costs, which increase with increasing soaring height. For this reason, hover altitude should be chosen moderately, limiting the area and sailing conditions.
Minimum hover height to ensure normal operation of small craft in good weather:

• for small rivers and lakes 3 cm;
• for large rivers and lakes 5 cm;
• for coastal sea navigation 8-10 cm.

When choosing the soaring height, it should be borne in mind that 0.6-1.0 liters must be spent to lift every 100 kg of the weight of a small vessel to a height of 1 cm. with. the power of the motor driving the fan.

Shape and dimensions of the vessel... The minimum energy costs for lifting the vessel (for a given hover height, apparatus weight and cushion area) can be obtained with a minimum bottom perimeter. This is because the air leakage from the air cushion is proportional to its perimeter. Of all the geometrical figures, the circle satisfies this condition to the greatest extent.

However, when determining the resistance to movement of the vessel, it can be determined that an increase in the ratio of the length of the vessel to its width (L / B) is desirable in order to reduce the resistance to movement.

The optimal shape of the bottom in plan can be obtained by varying it. Usually the L / B ratio ranges from 2-2.5.

To ensure the normal operation of hovercraft over a rough water surface, their bows are shaped like the bows of conventional ships.

Stability assurance... As you know, the stability of a vessel is called the ability to return to the original straight position, from which external forces brought it out.

The stability of hovercraft is achieved in other ways than for displacement vessels. As already noted, special devices are needed for this purpose. On ships with a common dome chamber, these are side floats that lean against the water when tilted, or dividing the dome part into compartments with plates (knives) in the longitudinal direction and slaps in the transverse directions; on ships with a single-circuit nozzle cushioning scheme, this is usually the device of the second row of nozzles.

As in the case of displacement vessels, lowering the center of gravity - the CG of the vessel or raising it, respectively, leads to an increase or decrease in the stability of the apparatus.

The trimming of the vessel in the hover mode without a stroke is ensured by placing the vessel's CG and the center of pressure of the air cushion on the same vertical line. With well-provided stability of the vessel, some displacement of the CG relative to the center of pressure does not lead to a significant trim, but it can strongly affect the value of resistance to movement (both in the positive and in the negative direction). According to some experts, in order to reduce the wave resistance hump, the CG should be displaced into the nose by 2-3% L.

Agility and braking... Ensuring the normal maneuverability of hovercraft is a very difficult and insufficiently studied problem. Air rudders are usually used to ensure the turnability of small vessels. Sometimes the rotation is carried out by tilting the apparatus or by deflecting air jets, or by changing the operating mode of two propellers of an adjustable pitch.

Braking is carried out by propellers of adjustable pitch, by tilting the apparatus or by directed air flow. A sufficiently fast braking when driving over the water surface can be carried out when the fan motors and propellers are stopped.

Splashing... One of the main disadvantages of hovercraft is large splashing, which impairs the view from the wheelhouse, especially at low speeds, increases the resistance of the vessel to movement and requires sealing the electrical equipment of the engines, installing filters on carburetors, etc. At high speeds, spray remains behind the stern and do not bring significant trouble.

Reduction of spatter formation can be achieved by reducing the pressure in the cushion, which is associated with an increase in its area or a decrease in the weight of the vessel (there is no spatter formation when the pressure in the cushion is less than 10 kg / m 2).

The spatter generation of chamber vessels is generally less than comparable nozzle vessels. The smallest splashing can be achieved with air-wing vehicles.

Body design... The structure of the hull must provide sufficient strength to the vessel with a minimum weight. It should be noted that the structural units of the hulls of hovercraft are more reminiscent of the structures not of a ship, but of an aircraft.

The thickness of the cladding made of aluminum alloys on currently built vessels weighing up to 30 tons does not exceed 1.5-2 mm, on vessels weighing up to 10-15 tons only 0.7-1.5 mm. As a rule, thicker sheets are installed in the bow and on the bottom, taking the impact of the waves. It should also be borne in mind that during the operation of a hovercraft, shock waves can lead to sharp braking and, consequently, the appearance of large inertial forces. In this regard, the fastenings of various parts and assemblies with a large mass must be sufficiently strong.

The following basic requirements are imposed on the material for the manufacture of the case:

• the lowest possible ratio of specific gravity to strength;
• water and air tightness;
• corrosion resistance;
• ease of processing and assembly of structural units.

Materials that meet these requirements can be: aluminum alloys; plastics reinforced with glass or cotton fabrics; waterproof plywood and others.

To obtain a simple and lightweight body, a frame-type structure covered with cotton fabric or plastic film may be of particular interest. To make the fabric waterproof and durable, it should be impregnated with epoxy or polyester.

The weight of the body of air-cushion vehicles, per 1 m 2 of plan area, ranges from 10 to 30 kg.

Determination of the power required to create an air cushion

Chamber way... For devices with a chamber-type pillow creation scheme, energy costs are associated with free air leakage from under the bottom along the entire perimeter of the vessel or in its part, if there are fences in the form of side knives, bow and stern slams, etc. (Fig. 16).

The fan performance must be equal to the air flow. Air flow or fan performance for a chamber circuit:

where S is the area of ​​the passage through which the air comes out from under the bottom, m 2;
v - air outflow speed, m / sec.
Air passage area:
where P is the perimeter of the vessel along the lower edge of the dome, m;
h c - jet height, m.

Since when exiting from under the dome the jet narrows, the jet height is slightly less than the hover height h and can be taken as h c - 0.7 ÷ 0.8 h.

The outflow rate can be determined with a sufficient degree of accuracy by the formula for the free outflow of air from the vessel, i.e.:

where P is the overpressure under the dome, kg / m 2;
g - acceleration of gravity, m / sec 2;
y - specific gravity of air, kg / m 3.

Then the fan performance will be determined as:

and the power spent on lifting:

where η B is the efficiency of the fan.

Nozzle method... Apparatus with a nozzle air cushion formation air flow rate (Fig. 17) is relatively less than that of apparatus with a chamber design.

Determining the power required to create a given hover height, fan characteristics, and other design inputs for the nozzle method is a more complex problem.

For approximate calculations of the power spent on lifting, you can use the formula:

With a two-circuit nozzle scheme, the required power should be increased by about 20%.

Choice of motor and fan

After establishing the required fan power, you should proceed to the selection of the engine. The main requirements that should be imposed on the engines of hovercraft:

1) minimum engine weight per 1 liter. with.;

2) reliability of operation in conditions of intensive splashing.

With capacities up to 30 liters. with. the basic requirement (minimum relative weight) is met by motorcycle engines. However, it should be borne in mind that the operating conditions of these engines on motorcycles and on an air cushion boat differ significantly both in the nature of the engine's operation and in the conditions for its cooling. Therefore, when using a motorcycle engine, the calculated one should not be considered the maximum power, but the power at which its long-term operation can be carried out (approximately 0.7 ÷ 0.8 N max).

It is necessary to ensure intensive cooling of the engine during its operation and good filtration of the air entering the cylinders through the carburetor.

To obtain the minimum weight of the entire installation, the problem of choosing the type of engine must be solved in a complex, simultaneously with the choice of the transmission from the engine to the fan and the fan design. It is known that a change in the fan speed leads to a corresponding change in the structural dimensions and weight at the same performance.

One of the main structural elements of a hovercraft is a fan, so the choice of its size and design must be made with particular care. As mentioned earlier, the required performance of the fans for ships with a nozzle circuit is 30-40% less than for ships with a chamber circuit at the same hovering height. This circumstance makes it possible to use smaller fans for nozzle circuits, which is an additional advantage of the nozzle circuit.

Determination of the main elements of fans for hovercraft is carried out by the methods described in the specialized literature, and usually does not cause difficulties.

At present, mainly axial fans are used to create an air cushion, however, fans of other types can also be used with success.

The location of the fans is determined by the need for uniform pressure distribution over the bottom area and weight trimming. They are usually positioned symmetrically with respect to the CG of the area of ​​the pillow or on a vertical axis passing through it.

Noteworthy are fan circuits that use the high-speed head of oncoming air. In some cases, when using such schemes, the fans receive a horizontal axis of rotation and are located with an offset towards the nose. Despite the tempting application of this scheme, it should be borne in mind that it is very difficult to solve such a problem. Fans in the parking lot and while driving will work in different conditions, and this can entail a significant complication of their design and lead to the need to use rotary blades in order to maintain a constant efficiency value when operating conditions change, without which the advantage of such a scheme can be reduced to zero.

Particular attention should be paid to ensuring the durability of the fan and its attachment to the case. When designing and manufacturing a fan, remember to balance it. Insufficient balance can lead to severe vibration and even damage to the fan and related structures.

The design characteristics of the fan should be selected taking into account the air cushion design. For the chamber circuit, the performance Q can be found using the formulas given above, and the head And can be taken equal to the pressure in the chamber P. For the nozzle circuit, the fan performance and pressure should be determined taking into account the losses in the air ducts.

Static pressure behind the fan:

where k B is a coefficient that takes into account the pressure loss in the air ducts. For ships with a nozzle scheme, k B = 0.6 ÷ 0.7.

Then the performance will be determined by the formula:

Choice of parameters of the nozzle device

The main characteristics of the nozzle device, which are decisive for choosing the optimal parameters of the air cushion, are:

1) air cushion pressure P;

2) angle of inclination of the nozzle Θ (see fig. 17);

3) nozzle width t.

The air cushion pressure for small devices ranges from 80-100 kg / m 2.

The optimal angle of inclination of the nozzle 0opt can be selected according to the graph (Fig. 18) depending on the ratios h / t and t / D O, where D O is the equivalent diameter:

The ratio of the soaring height to the width of the nozzle is usually taken in the range from 2 to 3.

Hovercraft Movement Resistance

Wave resistance... A ship hovering above the water creates a depression in it (Fig. 19), the depth of which depends on the air pressure under the bottom. When such a vessel moves, the deepening of the water surface moves with it and creates systems of transverse and diverging waves, the pattern of which is similar to the wave formation of a displacement vessel of the same shape. Thus, hovercraft, like displacement vessels, experience wave drag.

As the speed of movement increases, the pattern of wave formation changes. At the beginning of the movement, the wave resistance grows quite intensively, and then falls just as rapidly. With Froude numbers:

exceeding 0.7, the characteristic impedance decreases sharply. It follows from this that the horizontal thrust of the propellers should ensure that the maximum wave resistance is overcome, and the design speed should be higher:

The approximate wave impedance of a rectangular vessel with different aspect ratios can be determined by the formula:

Having made calculations using the specified formula, it can be established that the characteristic impedance decreases with decreasing aspect ratio.

Air resistance. Air resistance to the movement of hovercraft is one of the main types of resistance. To determine the value of air resistance, you can use the formula:

To accurately determine the value of the coefficient C x, special model tests of the ship in a wind tunnel are required. Its value can be approximated in the range of 0.3-0.5, and for vessels with a streamlined shape it will be closer to 0.3.

Impulse loss resistance... In hovercraft operation, air is entrained by the fan and carried along with the boat. This circumstance leads to losses, called impulse resistance.

The impulse loss impedance for devices that do not provide for deflection of air jets into the stern can be determined from the expression:

where Q is the fan capacity, m 3 / sec; V - travel speed, m / sec.

In reality, the oncoming air flow during the movement of the hovercraft deflects the air jets coming out of the nozzles into the stern. In most devices, the deflection of the jets is provided for by the design, which makes it possible to obtain an additional horizontal stop, the value of which can be determined approximately from the expression:

Even if we do not take into account the resistance to the loss of momentum and the additional thrust of the deflected jets, this will not lead to significant errors in the design of ships with relatively low soaring heights; therefore, all this calculation can be practically omitted.

Movers

The creation of a stop for the movement of hovercraft is carried out in various ways (propellers, water propellers, air thrusters, etc.). The choice of the type of propulsion device should be determined as a result of the design study in order to obtain the most economical apparatus.

Despite the variety of propulsion devices used, some regularities can be established. So, for ships weighing up to 0.7 tons, movement is usually carried out by tilting the ship in the desired direction or by deflecting the air stream in the nozzle device with special deflecting blades. In this way, a speed of 5 to 30 knots can be obtained, and a higher speed limit can be reached in vessels with a higher cushion height, since this will allow for a greater inclination.

On ships of considerable size with a chamber scheme and side knives, water propellers are successfully used. Since the presence of side knives limits their maximum speed (20-30 knots) and prevents the ship from going ashore, the installation of water propellers, providing a high efficiency at these speeds, turns out to be the most expedient.

On ships with complete separation from the water and weighing more than 1 ton, in most cases, propellers are installed as propellers. This is due to the desire to ensure the possibility of operating the devices in shallow water, on shallows and with access to the shore. In addition, the design speeds of vessels with complete separation from the water (due to their low drag) can be obtained significantly higher (60-100 knots and more). At these speeds, the efficiency of the propellers can be even greater than that of the water propellers, while at lower speeds the propellers are inferior to the water propellers.
Let's calculate (approximately) the components of the weight load.

1. Weight of the case (we take 20 kg per 1 m 2 of the pillow area) P k = 20 · S = 20 · 4 = 80 kg.

2. The weight of the fan motor is 50 kg.

3. Fan weight 20 kg.

4. The weight of the propeller engine is 30 kg (it is assumed that the engine will work "on a straight line" with the gearbox and clutch removed).

5. The weight of the propeller is 5 kg.

6. The weight of the foundations for the fan motor is 8 kg.

7. The weight of the foundations for the propeller engine is 12 kg.

8. Protection of propellers 3 kg.

9. Steering device 7 kg.

10. Gas tanks and fuel lines 5 kg.

11. Governing bodies 5 kg.

12. Seat weight 5 kg.

13. Fuel weight 20 kg.

14. Loading capacity (2 persons) 140 kg.

Total: 400 Kg.

Literature

• Benois Yu. Yu., Korsakov V.M., Hovercraft, Sudpromgiz, 1962.
• Letunov V.S., Hovercraft, "Sea Transport", 1963.
• Korytov N. V., X alfin M. Ya., Calculation of energy characteristics of hovercraft, "Sudostroenie", No. 9, 1962.

In the mid-seventies of the last century, domestic shipbuilders from the Almaz Central Marine Design Bureau took up a new theme of a skeg-type hovercraft. Ultimately, this work resulted in the construction of two small missile ships of project 1239 "Sivuch". The ships Bora and Samum are capable of accelerating to 55 knots and moving in waves of up to eight points. Combined with anti-ship missiles on board, the sailing qualities of the Sivucha make them a formidable naval one.

MRK hovercraft "Samum"

It is worth noting that in the early stages of the development of Project 1239, two options for the scheme of future ships were considered. They were a "classic" hovercraft and a skeg-type ship. Both of them had their pros and cons, so it was decided to test the prospects of both schemes in practice. First of all, the possibilities of a skeg-type hovercraft were considered. This topic at that time was not very well studied and therefore aroused particular interest. To study the running characteristics of such ships in the second half of the seventies, a self-propelled model "Ikar-1" was built. She was a small boat, at the same time resembling a flat-bottomed ship and a catamaran. The central part of the bottom was flat, and two skegs were lowered into the water along the sides - special panels of a special shape that made a catamaran out of the boat. When moving, air entered the space between the water, the bottom and the skegs, which partially took on the weight of the boat. The model was tested and, according to the results of the analysis of the collected information, a larger boat "Ikar-2" was built.

When testing the second experimental watercraft, some problems disappeared, but others manifested themselves with renewed vigor. So, during the acceleration of the boat, the air entering under the bottom often reached the propellers. Under certain circumstances, this led to the so-called. overshoot - an impulse increase in the propeller and engine speed due to the abrupt transition of the propeller from water to air. Sometimes this led to the activation of the motor protection systems and the shutdown of the latter. Also, a lot of trouble for the engineers was caused by the ingress of air into the technological intake openings, for example, into the kingstons of the engine cooling system. It was originally planned to solve both problems with additional high and long keels on the skegs. Already the first trial "races" with them showed the futility of such an idea.

General view of a possible modification of the hovercraft skeg

It took a long time to find a solution to the problem, but the result was worth it. The found method to exclude the ingress of air on the propellers and in the kingstons ultimately significantly influenced the final appearance of the domestic hovercraft of the skeg type. The designers of "Almaz" suggested limiting the air supply under the bottom depending on the speed of movement. At low speeds, a small amount of air had to enter the space between the bottom of the boat and the water, and when the maximum speed was reached, the maximum possible. In addition, the propellers were placed on the outer surfaces of the skegs, outside the volume of the air cushion. Thus, the highest dynamic unloading and power plant characteristics were achieved. As a result of all the measures taken, the experimental boat "Ikar-2" with a displacement of slightly less than 50 tons could move in waves of up to three points at a speed of about 30 knots. At the same time, despite the force of the waves, the boat went confidently and gently. In the future, the system with the regulation of air supply under the bottom passed to new ships of the skeg type.

The information obtained during the Ikara-2 tests was actively used in the development of project 1239. For example, the Bora and Samum ships have a system for regulating the air supply under the bottom. Depending on the travel mode and the required characteristics, the bow and stern openings between the skegs can be closed with special flexible fences. Thus, the Sea Lions can move as a simple catamaran, as a vessel with dynamic support by means of an incoming air flow, and also as a “classic” hovercraft.

Simultaneously with work on the hydrodynamic appearance of the ship, Almaz was developing a power plant for Project 1239. As a result of analyzing numerous options, a combined scheme with diesel and gas turbine engines was chosen. As a result, the ships of the Sivuch project are equipped with six engines of several types at once. For economical propulsion, the ship has two M-511A diesel engines with a maximum power of up to 10 thousand horsepower each. Two other diesel engines - M-503B (2x3300 hp) - are designed to pump air under the ship's bottom while moving at high speed. The latter is provided with the help of two gas turbine engines M-10, with a capacity of up to 20-23 thousand hp. Diesel engines M-511A transmit torque to the propellers at the stern of the ship, and M-503B engines are connected to the injection turbines. Gas turbine engines, in turn, drive two propellers, placed on special rotary columns in the stern of the ship. With an economical course, the columns rise above the water and are located in an upright position. In the case of switching to high-speed mode, the columns are lowered into the water and gas turbine engines are started.

MRK hovercraft "Bora"

It is argued that the original system of skegs and fences in combination with the architecture of the power plant gives the ships of the project 1239 the ability to move in one of 36 modes, conventionally divided into three groups. These are the modes of the catamaran, and two variants of the hovercraft. With the help of only M-511A diesel engines, the Sivuchi are capable of moving at speeds up to 18-20 knots. For acceleration to high speeds, it is necessary to use injection diesel engines and gas turbine engines. When the entire power plant is turned on at full power, the ships of the project 1239 can accelerate to 55 knots. At the same time, however, the cruising range is reduced by more than three times in comparison with the economical course. Interestingly, among the 36 operating modes of engines, propellers and a skeg hull, there is even one that allows the ship to move only with the help of injection diesel engines. With the front and open rear air cushion fencing closed, the ship can move at a speed of up to three knots only due to the outflow of air injected under the bottom, even against the wind.

Small missile ships of project 1239 "Sivuch" are undoubtedly one of the most interesting and promising pieces of equipment of the Russian Navy. Due to their high running data, they are able to perform some actions that are inaccessible to other ships. For example, there is information about trial anti-missile and anti-torpedo maneuvers. According to reports, the Sivuchi, due to their high speed, under a certain set of circumstances, are capable of disrupting the guidance of anti-ship missiles and evading torpedoes.

However, despite all the advantages, the Sivuchi and other ships of the skeg type have one big drawback. There are too few of them. In view of the high prospects of skeg-type hovercraft, work continues on the creation of new projects of such technology. At present, the Almaz Central Marine Design Bureau is studying the possibilities of creating new skeg ships for various purposes. For example, the possibility of continuing the development of the ideology of high-speed missile ships or placing a helicopter (helicopters) on the ship is being considered. For the latter, it is proposed to remove the lowering columns from the propulsion system and use only aft propellers or water-jet propellers placed on skegs.

Another area where skeg-type hovercraft can find application is the landing of assault forces. According to the skeg scheme, it is possible to build landing boats and small landing ships. Due to its structure, such equipment will be able to quickly approach the coast and, if necessary, carry out the landing of troops in close proximity to land. With the use of injection engines, such a ship or boat will be able to approach the shore and "sit down" on the bottom, using skegs as supports. In this case, both the landing of an assault force and a more effective use of weapons are possible. In theory, skeg-type ships can be used for a wide variety of purposes. This is an attack on enemy ships with missile weapons (project 1239), and landing or fire support of an assault force, and even rescuing victims of shipwrecks or other similar incidents.

In the nineties, the Almaz design bureau, using the developments in Project 1239 and related research programs, created a purely civilian hovercraft of the skeg type. The RSES-500 project was a high-speed ferry designed to operate in cargo and passenger transportation in the Baltic Sea or other similar waters. Unfortunately, the economic problems of the nineties did not allow bringing the RSES-500 project even to the stage of laying the first experimental vessel. Perhaps, in the coming years, design work will be resumed and some sea carriers will buy a new ferry.

Currently, skeg-type hovercraft have good prospects in their sector. Due to certain technical limitations, such equipment cannot have a large displacement, but in the “sector” of up to a thousand tons, no other class of floating craft can compete with it. According to research and theoretical calculations, a vessel or ship with a displacement of about a thousand tons, using gas turbine engines and a multi-mode skeg-type air cushion, is capable of reaching speeds of about 100 knots. Of course, the price of such a speed will be huge fuel consumption, but in some areas of transportation and military affairs, this can be considered an acceptable price for high performance.

It is noteworthy that Russian scientists and engineers have the world's largest experience in creating skeg-type ships, and also possess a number of interesting know-how. In the near future, these ideas and solutions may prove useful in the commercial market. However, so far there is no information about the plans of domestic shipbuilders regarding the creation of commercial hovercraft of the skeg type. The situation is approximately the same with warships of this class. I really would not like the existing developments on this topic to be forgotten and no longer be of use.

Based on materials from sites:
http://flotprom.ru/
http://oborona.ru/
http://flot.sevastopol.info/
http://bora-class.info/
http://almaz-kb.ru/