Hovercraft Design and Construction Thesis.pdf

YILDIZ TECHNICAL UNIVERSITYNAVAL ARCHITECTURE AND MARITIME FACULTY DEPARTMENT OF NAVAL ARCHITECTURE AND MARINE ENGINEERING GRADUATION THESIS HOVERCRAFT DESIGN AND CONSTRUCTION 100A2036 MUSTAFA ÇAĞRI ARDIÇ ADVISER ASST.PROF.OKTAY YILMAZ ISTANBUL, 2015 İSTANBUL, 2011 1 FOREWORD I would like to express my sincere thanks to Asst. Prof. Dr. Oktay YILMAZ who enables me to work on this topic. His guidance and motivation leads me to learn the present topic and finish the thesis on time. December, 2015 Mustafa Çağrı Ardıç 2 ACKNOWLEDGEMENTS I would like to give my very special thanks to Associate Prof. Dr. Yüksel PALACI, Prof. Dr. Abdi KÜKNER, Prof. Dr. Hüseyin YILMAZ, Associate Prof. Dr. Seyfettin BAYRAKTAR and Prof. Dr. Ahmet Dursun ALKAN for their guidance, support and encouragement for my project. December 2015 Mustafa Çağrı Ardıç 3 ... 23 3........................................................... 9 GRAPH LIST .......................1 Commercial .....3 1700 – 1900: The Genesis of Air Cushion Vehicles .. 22 3................ 20 CHAPTER 3 ..........................................................................................................................1.............................................................1..................... 23 4 .......4 1900 – 1950: The Evolution of Air Cushion Vehicles ................................... 22 3................................................................................................................................................................................. 2 ACKNOWLEDGEMENTS.................................................1...............1 Water: The Ancient Highway...............................................................................................1............................................................................................................................................................... 22 3............ CONTENTS FOREWORD .................................... 11 ABBREVIATIONS LIST ........ 14 1 INTRODUCTION..... 18 2...................... 22 3................1 Passenger Ferry ......... 16 2...... 22 3 APPLİCATİON OF HOVERCRAFT .... 16 2 HISTORY OF HOVERCRAFT .. 3 CONTENTS......................................................................................................................................................... 13 CHAPTER 1 ............. 16 2............................ 23 3............4 Logistical Support & Cargo Carrying ......................................................................................................3 Oil Spill Response Craft........................................................................... 7 TABLE LIST ................................5 Engineering Support ................................................................................................................................................ 12 ABSTRACT .............................................................................................................................................................................................................................................................................................................. 10 SYMBOL LIST .......................................................................................................................................................................................................................................................................2 Hydrographic & Seismic Surveys .................................................................................................................................................................. 4 FIGURE LIST ............................... 14 CHAPTER 2 ......................1...............................................................................2 Breaking the Water Barrier ........................................................................................................................................................... 16 2................................. ..........................................................................................4........3................... 24 3..................................................................4............................. 26 3................3 The Loop and Segment (or Bag and Finger) Skirt ................4............................4 Airport Crash Rescue .............................................. 48 5......................................... 45 5..........................4................................................................................................................. 35 CHAPTER 5 ............................5 Border Control ..........48 5..4............................................................................................................ 24 3..................4 The Inflated Loop (or Bag) Skirt .......................................3............................................................................................................................... 49 5.............................................................3............................1 ..........2..........................................................................................2........................................1................................................................................................1 PRESSURE AND LIFT ..1.............2 BODY DESIGN ................. 24 3....................................1..........4........................................3..............................................................................3 DRAG ....2 Logistics/Troop & Vehicle Carrier .............. 28 4............................ 31 4..........................................2...............2 Flood Rescue.............................4 SKIRT DESIGN...........................5 Ice Rescue .......................................1 Description..............................................1.................................. 37 5 DESIGN PROCESS ................................................4...3 Fast Attack & Amphibious Assault.....................1 The Inflated Loop (or Bag) Skirt ....................................................................5 Skirt Material.............3......................... 24 3..................................................1.................4................................................. 27 CHAPTER 4 ................1......................................................48 5........2 Rescue Applications.......3 Military ..........................................................................................................................1......................1............................................ 26 3.................................................................................................................................... 37 5....................................................................48 5............................................ 28 4 HOW DOES A HOVERCRAFT WORK ... 37 5...3 Mobile Medical Clinics..1 The Skirt&Stability ......................................................................................1........................... 26 3.......................... 32 4.... 47 5...............................4............... 41 5.............2 BUOYANCY................................... 25 3............... 44 5...............2 GENERAL SETTLEMENT...................................................................................................49 5.............................. 28 4....... 37 5...................4......................1 DATUM ............... 25 3........ 25 3................................................................................................ 48 5..............1 Skirt Charecteristics ..................4 Range Patrol ............................3 WEIGHT AND POWER ESTIMATIONS.......................1 Search & Rescue (SAR) ......................................1 Mine Counter Measures ..........................1..............................51 5 .......1 Skirt Characteristics ..................................... 25 3......................4...............2........2..................3................................................1 Skirt Characteristics ..................................................................................................2 The Segmented (or finger) Skirt ..................................... 48 5....................................................................................2.1 SIZE ESTIMATIONS ....................... 37 5.............................3....4 THRUST ............1....... ........................6.............4 Total Pressure (Pt) ....................... 53 5.5......................................................................................................3 Velocity Pressure (Pv) 𝑷𝒗 = 𝟏𝟐𝝆𝒗𝟐 ...................... 61 5.................................................................................5 LIFT SYSTEM............. 62 5....................... 51 5...................................................................................................................................................................... 58 5...... 53 5...........................................................................................5............................... 66 CHAPTER 6 ..........................................................1 What is thrust ? ...................6 Fan Solidity .................................................................................... 59 5........................................ 71 8 CONCLUSION .................................................................... 67 6 MATERIALS ..............5............................................................................................... 65 5..............6..........................5 Estimation of Fan Pressure Requirements .................... 61 5................................ 71 References .......................6......................................................5.......................5.................................................... 61 5........................................4 Static and Dynamic Thrust .................................................6 PROPULSION SYSTEM ....................................................................................................5 Calculating Duct Areas...................6.................................6....................................................... 72 CURRICULUM VITAE . 54 5..........................................................2 Static Pressure (Ps) ................................................. 68 CHAPTER 8 .....................5..... 73 6 ................................................................................................................................................................................................................2 Momentum Drag ...............................................................................3 Net Thrust ...................................6............................................................................. 53 5....................................................... 67 CHAPTER 7 .................................................................................................... 68 7 COST ANALYSIS ....................1 Definition of Pressure . .................. 25 Figure 3 12 ............................................ 15 Figure 2 1 (3)......................................................................................................................................................................................... 28 Figure 4 2 Figure 4 3 ................................................................................................................................................................................... 32 Figure 4 7 ............................................................................................................... 46 Figure 5 8 (14).......................................................................................................................................................... 35 Figure 4 11 ............................................................................................................................................................ 27 Figure 4 1 (7)................................................................................................................................... 14 Figure 1 3 Figure 1 4................................................................................ 22 Figure 3 2 ................ 23 Figure 3 5 ........... FIGURE LIST Figure 1 1 Figure 1 2..................................................................................................................................................................................................................................................... 49 Figure 5 11 (14)..................................................................... 42 Figure 5 4 .............................................................................................................................................................................................................................. 26 Figure 3 15 ............................................................................................................... 26 Figure 3 14 ......... 20 Figure 3 1 .................................................................................................................................................................................................................................................................................................................................................................................................... 33 Figure 4 8 ......................................................................... 43 Figure 5 6 ........................................................................................... 30 Figure 4 4 (7)........................... 31 Figure 4 6 ........................................................................................................................................................................................ 30 Figure 4 5 (7)... 42 Figure 5 5 .............................................................................................................................................................................................................................................................................................................................. 26 Figure 3 13 .............................................. 47 Figure 5 9 (14)............................................................................................. 23 Figure 3 6 ................................................................................................ 22 Figure 3 3 ............................................................................................................................................................................................................... 25 Figure 3 10 ............................................. 15 Figure 1 5 Figure 1 6............................................................. 52 7 ................................................. 34 Figure 4 10 ................................................................................. 49 Figure 5 10 (14)........................... 50 Figure 5 12 ......... 23 Figure 3 4 ......... 36 Figure 5 1 (13).................................................................................................................... 40 Figure 5 2 .............................................................................................................................................. 24 Figure 3 7 ......................................................................................................................................................................................................................................................................................... 24 Figure 3 9 ................................. 41 Figure 5 3 ................................................................................................................................................................................................... 18 Figure 2 2 ........................................................................................................................................................................................................ 34 Figure 4 9 (7).......................................................... 25 Figure 3 11 ......................................................................................................................................................................................................................................................... 43 Figure 5 7 (14)...................................................................................................................................................................................................... 24 Figure 3 8 .................................................................................................................................................................................................................................................... ...................... 66 Figure 5 15 (19)............................ 65 Figure 5 14 . 66 8 ................................................................................Figure 5 13 ....................................................................................................................................................................................................................................................... ........................................................................................................... TABLE LIST Table 5 1 ................................................................................................................................ 44 Table 5 5 (14) ........ 64 Table 6 1 ............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................. 59 Table 5 9 (19) (20) ................ 50 Table 5 6 (17) .... 67 Table 7 1 ........................... 60 Table 5 10 (19) (20) .......................................................................................................... 39 Table 5 4 ................... 70 9 ............................................................................................. 56 Table 5 7 .................................................................................... 38 Table 5 2 ..... 39 Table 5 3 ............................................................................................................................................................................................. 58 Table 5 8 ........................ .................... 40 Graph 5 2 ............................................................................................................... GRAPH LIST Graph 5 1 ........................................................................................................................... 45 10 ....... SYMBOL LIST L Length B Beam D Depth V Velocity F Force Cd Drag Coefficient P Pressure A Area W Weight V Volume Vd Discharge Velocity PL Loop Pressure R Radius of the inner circle r Radius of the outer circle Ps Static Pressure Pa Atmospheric Pressure 𝜌 Rho Pv Velocity Pressure Pt Total Pressure Ve.Vesc Escape Velocity Vol Total Volume of Air Lost Ae Escape Area Dc Discharge Coefficient Q Flow Tg Gross Thrust Qd Quantity of Air at the Discharge Tn Net Thrust 11 . ABBREVIATIONS LIST ACV Air Cushion Vehicle GEM Ground-Effect Machine 12 . Oktay Yılmaz With the changing world. 13 . In this hovercraft project. I combined at least two vehicles to operate in any emergency case. money and most importantly the lives of the people. on snow. cheap to produce. Prof. the requirements of the people are changing very rapidly. on ice. at sea. time. in desert. Each winter especially the people in Eastern parts of our country and suffer from harsh weather conditions as well as heavy geographical conditions. Dr. The hovercraft can be used in all weather conditions and almost in all geographical conditions. It is totally a domestic production. but the main goal is to make the hovercraft a domestic production. ABSTRACT HOVERCRAFT DESIGN AND CONSTRUCTION Mustafa Çağrı Ardıç Department of Naval Architecture and Marine Engineering Advisor Asst. It was a subject which was never studied by anybody else before. It has the ability to manoeuvre on land. That is what made me to prepare a thesis about hovercrafts.Technological products are designed to meet the requirements of the people and to facilitate their lives. Almost in all new inventions the main aim is to design something which can make radical changes while saving energy. My goal is to produce a vehicle with high quality. Because most surfaces are uneven. 6-9 inches [15. A multi-blade fan forces air under the hull of the hovercraft.86 cm] in most cases. The hovercraft lifts off the surface it's resting on when the lift air pressure is greater than the total weight of the hovercraft divided by the area of the lift air cushion. Hovercraft also use air to move forward. Often. This creates a wall that traps the lift air. short grass. creating forward thrust. water. ice. additional height is needed so the craft can travel without getting the bottom of the hull caught on anything (1). Sometimes called an air-cushion vehicle or ACV or GEM (ground effect vehicle). a circular enclosure called a thrust duct is built around the propeller. can drive like a car but will traverse ditches and gullies as it is a flat terrain.24 – 22. Many hovercraft use an engine with an airplane-type propeller or multi-blade axial fan to push air behind the hovercraft. a hovercraft rides on a cushion of air instead of wheels to go over many surfaces. Figure 1 1 Figure 1 2 Because the hovercraft only puts a very small pressure on the surface it’s riding over. It then hovers just above the surface. By using a thrust duct built 14 . To increase the clearance between the bottom of the hovercraft and any uneven surfaces. snow. it can easily be flown over mud. CHAPTER 1 1 INTRODUCTION A Hovercraft is a vehicle that flies like a plane but can float like a boat. or pavement. a flexible fabric skirt is attached to the bottom outside edge of the hull. creating a high-pressure region called the lift air cushion and making the craft float. sand. giving the hovercraft a smooth ride and allowing it to clear obstacles. forcing the hovercraft to rise higher above the surface. similar to the effect that moving a long lever is easier than moving a short lever. forcing the hovercraft to change direction. Rudders are made with a symmetrical airfoil profile to minimize air drag and increase their efficiency.3175 cm] of the inside face of the duct. The rudders are mounted behind the thrust duct to put them directly in the flow of the thrust air. In the following handouts we will investigate the science behind what makes a hovercraft work . the thrust output of the propeller can be increased by 10-15%. (2) Figure 1 5 Figure 1 6 15 . Circa: 1993) The thrust determines how fast the hovercraft can go and how steep a grade (like a boat ramp) it can climb (1). (Fowler. some as many as 5. Figure 1 3 Figure 1 4 Steering a hovercraft is accomplished using rudders. the thrust air is deflected left or right. Their position also gives them a mechanical advantage in turning the hovercraft. As the rudders turn. Most hovercraft use at least 2 rudders.so the tips of the propeller travel within 1/8 inch [0. similar to those on an airplane. one ship with six or eight men could carry as much as 50 wagons attended by hundreds of men and 400 horses .2 Breaking the Water Barrier Throughout history.1 Water: The Ancient Highway The growth of civilization occurred within view of – and in many ways because of – our seas and rivers. In 1775 Adam Smith. and the earliest cities were located on seashores or rivers. Without a means of water transportation. the first economist. Water travel requires less manpower than overland travel and can accommodate far greater loads than wagons. ground and air transport vehicles have dramatically and continuously increased their speed. The superiority of water transport over ground transport was so apparent to even the earliest civilizations that canal building was one of mankind's earliest engineering achievements. animals or more recent ground transport vehicles (2). mankind has been intent upon finding ways to transport larger loads and to increase the speed of load movement. In his analysis of why some nations are more prosperous than others. 2. ancient mariners could not have explored the world or traded goods. Such is not the case with 16 . Since the beginning of human history. Civilizations that mastered ship building and sailing inevitably prospered as centers of trade. recognized the importance of water transportation in his revolutionary book An Inquiry into the Nature and Causes of the Wealth of Nations. we have been shaped by our ability to carry goods and people across water – our most ancient highway.and concluded that communication across water has always been the least expensive form of transportation. Smith examined the advantages of water over ground transportation . From their inception. CHAPTER 2 2 HISTORY OF HOVERCRAFT 2. culture and power. 0) This is a huge number. When a load is moved via water. the entire hull has to be lifted off the surface. The density of water is 815 times the density of air. the various resistances increase as the velocity times itself.) Among them. because they have to contend with the strong resistance of water – the water barrier. this results in drag (resistance) when movement commences. One method of describing transport efficiency is the movement of a specific load over a specific distance in a specific time. and the energy needed to affect an increase in speed rises as the energy cubed. which reduces wave production and surface parasitic drag. especially during the last three centuries. In a quest to break the water barrier. transport efficiency is the movement of a specific load multiplied by the speed at which it can be moved.vehicles that travel across water. many vehicles have been invented. The only way to improve the lift-to-drag ration of a boat is to lift the boat's hull and load completely out of the water. the air cushion vehicle has the best lift-to-drag ratio of any device that travels across water when speeds exceed 35 mph (2). A boat has a lift-to-drag ratio about ten times lower than a steel wheel rolling on a steel rail. the resistance of the water increases exponentially. Another way to think of this problem is to consider the lift-to-drag ratio. Speed equals distance divided by time. As a ship increases speed. The majority of the modern inventions are based on the idea of lifting the water displacement hull. hydrofoils and air cushion vehicles. It is an old idea to pump air under a ship's hull in order to reduce resistance. to improve the lift-to-drag ratio and decrease the resistance of water. causing huge increases in power to achieve only small gains in speed. (The hovercraft is one type of air cushion vehicle. One factor that creates the water barrier is water density. therefore. or energy multiplied by itself three times (the exact power is 3. 17 . but the obvious and simple approaches to this idea do not work. or lifting the load-carrying device out of the water. The load has to float or be lifted by the water. These include hydroplanes. and is the first detailed technical description of a flying machine of any type. a Swedish designer. 2. 18 . because Swedenborg soon realized that a human could not sustain the energy needed to power the oars. philosopher and theologian. proposing the principle of air lubrication. who was the Chief Constructor of the Royal Netherlands Navy. Swedenborg's man-powered air cushion platform. As with many other forms of transportation. ideas easily date back to ancient Greece. Figure 2 1 (3) In 1865. J.3 1700 – 1900: The Genesis of Air Cushion Vehicles When it comes to flying machines. This is not the case with air cushion vehicles. William Fronde of the British Admiralty sent a letter to B. The first recorded design for such a vehicle was in 1716 by Emanuel Swedenborg." His manually operated device required the would-be pilot to use oar-like scoops to push air under the vehicle on each downward stroke in order to raise the hull out of the water. A working model of the design was never built. Daedulus Hyperboreus. significant progress had to wait until a lightweight motor was developed in the nineteenth century. His concept required a source of energy far greater than any available at that time. resembled an upside-down boat with a cockpit in the center or a "flying saucer. Tideman. Swedenborg's design appeared in the fourth edition of Sweden's first scientific journal. basically a circular aircraft. includes an idea that led to the first suggestion for sidewall air cushion vehicles." a train that rode on small hover skirted pads using water under pressure. The Modern System of Naval Architecture. He filed a number of patents involving air-lubricated hulls through 1877. California USA. M. I. Ward of San Francisco. and also appears on page 109 of J. His theory was that if a vessel's hull were designed with a concave bottom in which air could be contained between the hull and the water. Gustaf de Laval. Taylor. Vol. however. 1865.W. In the mid-1870s. In 1876. published in 1933. The 19 . was first proposed in 1868 by the French engineer Monsieur Louis Girard. A working example was operated in 1886 for 900 miles in the LeJouchere Park.C. US Patent 608757. John B. de Laval was not successful with his experiments. James Walker of Texas was granted US Patent 624271 in which channels along the underside of boats contained air that would be captured in the adjacent channel as it tried to escape. He received US Patents 185465 and 195860 for his "aerial machines. including railways. improved upon Girard's ideas and constructed a sliding railway at London's Crystal Palace in 1891. Information on this ship can be found on pages 33-34 in the book Speed and Power of Ships by Admiral D. The concept of a "sliding railway. it would create significantly less resistance. British Patent 5841 details a ship built with de Laval's ideas. in 1882 but because the method for retaining the cushion of air was not yet resolved. Air lubrication has been applied to many industrial processes and applications. no one had yet discovered a practical solution to the problem of how to keep a cushion of air trapped so it could not escape below a vessel." The first patent for air lubrication in Great Britain was issued to another Swedish engineer. obtained in 1897 by Culbertson.The letter is on display at the David Taylor Model Basin in Washington D. but wheels would push the device along. After Girard was killed in the Franco-German war. so the technology required to power his inventions still did not exist. one of his assistant engineers. suggested an aluminum platform with rotary fans to drive air down and backwards. the British engineer Sir John Thornycroft built a number of ground effect machine test models based on his theory that an air cushion system would reduce the drag of water on boats and ships. Scott Russell's book. In addition. In 1888. Barre. The internal combustion engine had not yet been invented. lubricating the hull with air from stem to stern." (2) 2.London News hailed the invention as "a marvelous invention … a singularly original contrivance for enabling trains to run by means of waterpower at speed hitherto undreamed of … something which may eclipse the electric motors. and after imaginations were fostered by the development of the airplane. As the airplane evolved as a viable vehicle after the renowned Wright Brothers flight in 1903. more attention was paid to the fact that additional lift was created if an airplane flew close to land or water. creating a "funnel effect" or cushion of air. This became known as ground effect. or hydrodynamic drag. 20 . naval architects patented several designs intended to solve the problem of water resistance. became a reality. which would raise it slightly above the water. Figure 2 2 Realizing that pressurized air reacts against the surface of water and enables a vessel to skim over the water rather than through it. the engine.4 1900 – 1950: The Evolution of Air Cushion Vehicles Experiments with air cushion vehicles began in earnest after a suitable power source. Onboard fans would force compressed air into a chamber beneath. Dagobert Muller von Thomamhul. and scientists and innovators began exploring the ground effect/air cushion effect in earnest. which used fans to pump air beneath the hull to form a lubricating air cushion. an Austrian engineer. in turn. 21 .World War I brought the development of the airplane as a military weapon which. At that time. fostered technological interest. Various forms of air cushion craft began to evolve after the first working example was demonstrated in 1916. designed and built an air cushion torpedo boat for the Austrian Navy. Further development was abandoned when World War I destroyed the Austrian Navy and the empire (3). (4) 22 .1 Passenger Ferry Conventional passenger craft often have to slow down on waterways because of the amount of wash or wake they produce at speed. Figure 3 2 Hovercraft can operate in areas which are inaccessible to conventional craft. tidal estuaries etc.2 Hydrographic & Seismic Surveys Hovercrafts can be equipped with hydrographic and seismic survey equipment and also hovercraft allows the operator to carry out studies in the shallow water areas. CHAPTER 3 3 APPLİCATİON OF HOVERCRAFT 3. Much time is saved since the craft is not restricted by tidal considerations.1 Commercial 3.1. which authorities and environmentalists consider as highly important. Journey times are also reduced. Figure 3 1 Hovercraft can travel on rivers.1. Hovercraft produce virtually no wash or wake at high speed. opening services that before were inaccessible. (4) 3. hovercraft safely extend the areas for seismic surveys. which cannot be navigated by conventional vessels. normally inaccessible by any other means. they can offer an essential emergency rescue service. Figure 3 5 Not having to rely on harbors. cable and pipe laying in shallow water and marginal terrain.1. Hovercraft can be based on unprepared beach or shore line. such as booms or skimmers. (4) 3. can be fitted.3. The hovercraft is able to reach the area at high-speed.5 Engineering Support Hovercraft are used across the globe in an engineering support role. Unlike conventional craft that churn up surface oil with their propellers making it more difficult to Figure 3 3 recover. therefore limiting the threat of further contamination or damage. the hovercraft air cushion allows the craft to hover over any oil spill with limited contact with the oil. safe working platform to which all oil spill response equipment. They can carry a range of equipment. (4) 23 . (4) Figure 3 4 3.1.3 Oil Spill Response Craft Hovercraft offer a stable.4 Logistical Support & Cargo Carrying Hovercrafts are able carry tremendous amounts of weight. The main cabin can also be configured for crew or passenger carrying. When not providing support to offshore equipment. Hovercraft can provide a round-the-clock solution.1. from drilling rigs and survey equipment to military vehicles and cranes. Wherever there are difficulties in providing vital ship to shore services for engineer work such as dredging. stored and safely deployed. 2.2 Rescue Applications 3. shallow and tidal areas. (5) 24 . Many SAR operators. Hovercrafts play vital role in SAR.2. sand-banks or frozen seas and lakes. there are various of countries using hovercraft for SAR including the UK Royal National Lifeboat Institution (RNLI) and Figure 3 7 Coastguards from Canada to Kuwait. (5) 3. secure and spacious cabins which can be kitted out with the latest medical equipment to suit your requirements.3 Mobile Medical Clinics In order to get a medical clinic and supplies to some of the remotest and inaccessible corners of the globe. have found the Griffon range to be a vital asset to their operations by performing a variety of roles. or on mud- flats. Hovercraft offer clean. Hovercrafts are the only vehicle able to provide high speed casualty response and medical evacuation in a flood rescue role. (5) 3. all of which use these craft for flood rescue. including Coastguards from Figure 3 6 Canada to Kuwait. Their ability to perform rescues on tidal mud plains is unique.3. forming an Figure 3 8 ideal mobile medical clinic. Yet these terrains are ideal hovercraft territory. medical evacuation and disaster relief. the hovercraft can be the only solution.1 Search & Rescue (SAR) Around in-shore. it is virtually impossible for conventional boats to provide a comprehensive search and rescue service.2.2 Flood Rescue Truly amphibious vehicles. as well as immobilised vessels. hovercrafts are often the only craft capable of providing rescue services in these areas. thus providing the quickest method to rescue a Figure 3 10 victim of the ice. (5) 3.3 Military 3. (5) 3. Since the craft's air cushion and flexible skirt absorb most of an exploding mine's shock wave. can operate over mines with impunity in deep or shallow water.1 Mine Counter Measures Hovercraft. at the same time as limiting the risk to the rescuer.3. they can Figure 3 11 be deployed more safely and cost-effective as mine hunter/killers than conventional boats. acoustic or magnetic signatures.2. (6) 25 .5 Ice Rescue A hovercraft offer an ideal solution for ice rescue. however hovercraft can travel at speed over ice and snow.3.2. Ice rescue is difficult with normal vehicles. Dundee Airport (UK).4 Airport Crash Rescue When airports are surrounded by difficult terrain. Equipped with full fire fighting and life saving equipment. since they produce virtually no pressure. with their low pressure cushion design. Singapore Changi Airport. Shannon Airport (Eire) and Liverpool airport (UK). There are a lot Figure 3 9 of Airports currently operating rescue hovercraft include Auckland International Airport. these unique amphibious high speed craft will deal with almost any emergency scenario. Rio de Janero International Airport. 3.3.2 Logistics/Troop & Vehicle Carrier Hovercraft have the ability to deliver troops and equipment rapidly across a beach, regardless of the state of tide or nature of the surface, which means the troops and equipment will disembark safely on to dry land. The Saudi Arabian Border Guard and Swedish Amphibious Battalion (left photo) 8100TD Figure 3 12 is configured to carry a 4x4 vehicle. Hovercraft range can be configured for carrying cargo and vehicles up to 22.5 tonnes, as well as being configured to carry differing levels of weaponry and ballistic protection to suit a clients requirements. (6) 3.3.3 Fast Attack & Amphibious Assault At high speed the craft produce virtually no wake. A wake leaves significant signature at night, particularly if it also induces phosphorescence. Not being constrained by shallow water, mud or even land, a hovercraft is an ideal tool for fast attack. (6) Figure 3 13 3.3.4 Range Patrol As seen in the photo on the left, the Belgium Army Griffon 2000TD hovercraft has been adapted for drone recovery in a designated firing range area. This area comprises of open sea, surf and a wide stretch of muddy beach, an area generally inaccessible by any other craft. Figure 3 14 Hovercraft can generate an extensive recce capability, moving from offshore to shore and deep into the land via a riverine network. They will also, over an extended and unsupported period, deploy and recover foot-borne 'recce patrols' (6) 26 3.3.5 Border Control With their high speed and amphibious capability, hovercraft are uniquely suited to areas where it is difficult or impossible to operate conventional boats or vehicles. With the very shallow water around some of India's extensive coastline and offshore islands, this Griffon 8000TD (left), with a top speed Figure 3 15 of 50 knots and armed with a half-inch machine gun, has proven to be the ideal craft for policing / customs duties for the Indian Coast Guard. (6) 27 CHAPTER 4 4 HOW DOES A HOVERCRAFT WORK 4.1 PRESSURE AND LIFT Lift air, like other gasses, is considered to be a fluid because it takes the shape of the container surrounding it. In the case of a hovercraft, the air takes the shape of the bottom of the hovercraft, the inside edges of the skirt, and the surface it's hovering above. The fan that blows air under the bottom of the hovercraft keeps pushing more and more air below the hovercraft, thus increasing the pressure in the air cushion. The pressurized air cushion exerts a force on its container (the bottom of the hovercraft, the skirt, and the surface the hovercraft is resting on). When the force this pressurized air exerts on the surface grows to equal the weight of the hovercraft, it becomes buoyant (like a boat in water) and begins to float on air. When a hovercraft hovers, it will lift as high as the skirt’s designed shape will permit. Lift air begins escaping through the gap between the bottom of the skirt and the surface it's over. The size of this gap will be large enough so that the same amount of air escapes through the gap as is pushed in by the fan, keeping the pressure inside the air cushion constant. Usually, this air gap will be 0 to ½ inches [12.7 mm] between the skirt bottom and the surface and is called daylight clearance. Figure 4 1 (7) 28 F=P·A The lift force is therefore the air pressure inside the air cushion multiplied by the area enclosed by the hovercraft skirts. In the integrated type hovercrafts. Static pressure is the pressure of a stationary region of air.Pressure is defined as the force exerted on a surface per unit area of the surface. only one propeller is used to provide both lift and thrust air. while dynamic pressure is the pressure of air that is in motion. A separate propeller mounted on the back of the hovercraft is responsible for driving the hovercraft forward. A multi-bladed fan is used for lift because it's better (more efficient) at pumping pressure than a propeller with just two blades. the lift air is more static. At the cushion center. you will obtain a different value than if you were to measure the pressure further inside the cushion. Static pressure is what lifts the hovercraft. 29 . In the case of hovercraft. there are two forms of pressure that can be measured: static pressure and dynamic pressure. The sole purpose of the fan is to maintain the pressure inside the air cushion under the hovercraft. Pressure = Force ÷ Area P=F÷A In order to calculate the lift force of a hovercraft. Other hovercraft designs have separate lift and thrust systems. If you measure the pressure of the lift air cushion by placing a manometer (a device that measures pressure) just under the skirt. we solve this equation for the force. so you could be measuring dynamic and static pressure at the same time. This is because the air is moving rapidly out of the bottom of the skirt. By placing this splitter just after the propeller. a portion (usually 1/3 of the total air supply) is forced by the propeller and directed down into the air cushion by the splitter in order to maintain the pressure inside the cushion. as shown above. the lift air is divided by a splitter usually located at the bottom of the thrust duct. (8) (9) 30 . propelling the hovercraft forward. The rest of the air is forced behind the hovercraft. Figure 4 2 Figure 4 3 Figure 4 4 (7) In the integrated hovercraft. A diagram of the various paths the intake air travels in an integrated type of hovercraft is shown below. The water has to go somewhere else when it is pushed out of the way. making the water level rise. This is because your body is now taking up some of the space where the water used to be. What keeps the hovercraft from sinking as well? The answer to this comes from one of the oldest established principles in the history of science: Archimedes’ Principle or the Law of Buoyancy.2 BUOYANCY We assumed that the hovercraft was hovering above solid ground. of the force is equal to the weight of the water that would have filled the space that is now taken up by the boat. part of the boat goes beneath the surface of the water and pushes the water out of the way. The boat floats in the water because this upward buoyant force is equal to the downward weight of the boat. the level of the water rises. According to Archimedes’ Principle. ‘When a body is immersed in fluid at rest it experiences an upward force or buoyant force equal to the weight of the fluid displaced by the body’. your hand would sink into the water. Notice when you get into a bathtub. What happens when the hovercraft travels over water ? In order to lift the hovercraft. so it goes up. this results in a buoyant force that pushes up on the boat. When a boat is placed in water. You’ve just displaced that amount of water. The magnitude. The same thing happens with boats. Archimedes’ Principle says that a buoyant force will push upwards on you when you’re in the water. the pressurized air must now push against the surface of the water. If you tried pushing your hand into a sink full of water. and the strength of the force will be equal to the weight of the water that you pushed out of the way when you got in. 31 . or strength. Figure 4 5 (7) 4. or the weight density of water. the weight density of water is about 9806 Newtons per cubic meter ( N/m3).54 cm].9 N/m2] of pressure in the lift air cushion. you can see that you create a small dimple in the water. we know that for every 5. Hovercraft do the same thing. there are forms of friction which come into play. because the hovercraft itself doesn’t actually displace any water. we need to know the weight of a certain volume of water that is displaced. or form drag. the most familiar being wind resistance. Weight Density = Weight ÷ Volume The weight density of water is about 62. A cubic foot is a unit of volume equal to the volume inside a box whose sides are 1 ft long. Drag occurs in several forms.3 DRAG A hovercraft is able to glide or slide easily because there is so little contact friction with the surface it's hovering over. and these frictional forces are usually called drag. the water underneath the hovercraft is depressed one inch [2. In fact. When a hovercraft travels over water. causing some of the water to be displaced. it acts a little differently than a boat.2 lb/ft2 [24. except they create a larger depression in the water. Still. It is the pressurized air inside the lift air cushion that pushes down on the water. If you blow into a sink full of water.In order to do calculations using this principle. which is created by the hovercraft having to push aside air as it 32 . In SI units (System International).42 pounds per cubic foot ( lb/ft3). (8) (10) Figure 4 6 4. in effect. When traveling above planning speed. At this point the hovercraft will accelerate rapidly. As the hovercraft starts moving forward. Wave drag (called hump drag at low speeds) occurs when lift air under the hovercraft pushes down on the surface of the water. While wind resistance is always present. Some of the water is displaced from under the hovercraft. and impact drag. the hovercraft will reach a speed where it's moving faster than the wave and "climbs" over it.3 km/h] and above. Called planning speed. the depression moves with it and forms a small wave in front of the bow. The hovercraft is. Eventually. according to Archimedes’ Principle. 33 . This effect increases more and more as the hovercraft’s speed increases. The moment before planning speed is reached. The total weight of the water displaced is equal to the weight of the hovercraft and pilot. Figure 4 7 A hovercraft operating over water is subject to three other forms of drag not experienced on solid surfaces: wave drag.moves forward. This causes the bow (front of hovercraft) to rise and the stern (back of hovercraft) to sink a little. it becomes much more of a problem at speeds of 30 mph [48. As the hovercraft increases speed. creating a depression in the water. the bow wave increases in size. Streamlining the shape of the hovercraft decreases the wind resistance. resulting in higher top speeds. it is commonly referred to as "getting over the hump". trying to fly "uphill". the lift air under the hovercraft doesn't have enough time to depress the surface of the water and the wave drag decreases dramatically. skirt drag. wave drag is at its greatest. (8) (11) 34 . Figure 4 8 Wave drag caused by depression in the water’s surface by the air cushion Skirt drag occurs when the skirt contacts the surface of the water. This is worse when running over small waves. Figure 4 9 (7) Impact drag happens when the skirt or hull strikes large waves on turbulent water or other objects. such as ice flows or ridges. the noise produced by both the engine and the propeller. One way to increase the efficiency of a propeller is by surrounding it with a circular enclosure called a thrust duct. Unfortunately. as well as the rest of the hovercraft. When designing propeller systems for hovercraft. efficiency is a big concern. The air. This causes the propeller. In a small hovercraft. Engineers try to get as much output work as possible for the least amount of input work. The propeller exerts a force on the air when it pushes it behind the hovercraft. Efficiency is the ratio of how much work is produced divided by how much work is put into the system. to be accelerated forward. The heat produced by the engine. 35 . and the vibrations you can feel in the hull are just some examples of wasted energy that isn’t being used to produce thrust. How does forcing air behind the hovercraft produce forward thrust? Newton’s third law: Every action has an opposite and equal reaction.4 THRUST A hovercraft moves by using air to create forward thrust. you can never get out as much work as you put in. exerts a force back on the propeller in the opposite direction. In order to produce forward thrust (the output). a properly built thrust duct can add a 10%-15% increase to the total thrust output. we must power the propeller with a fuel-driven engine (the input). Figure 4 10 4. in turn. compared to a non-ducted propeller. The propeller on the back of the hovercraft forces air towards the rear. 8 – 35.8 N/kW.79 – 26. so it is unable to produce as much thrust at higher speeds.8-20. Figure 4 11 To function properly. and push it out of the rear of the duct. the air will move from the back of the blade (higher pressure) to the front of the blade (lower pressure). The closer the propeller tips are to the wall of the duct. it is for that particular situation you tested the craft in. compress it. thrust can be calculated by multiplying the mass of the hovercraft by its acceleration.7 cm] long. Remember that for a fan or propeller. the more efficient they become. If there is too much space between the thrust duct and the propeller tips. When you calculate a particular thrust. The propeller tips should be no more than 1/8 of an inch [0. (8) (12) 36 . This allows the propeller or fan to pull air into the thrust duct. It’s harder for the propeller to accelerate air that’s already moving fast. According to Newton's second law. A typical propeller can produce 4 . so does the speed of the air that enters the thrust duct. or 23. the thrust force decreases as forward speed increases! This is because as the speed of the hovercraft increases.69 N] of thrust per horsepower. with the propeller positioned 7-8 inches [17. Air resistance caused by the air dragging against the walls of the thrust duct as it is blown back will increase as the length of the thrust duct increases.3175 cm] away from the inside wall. The length of a thrust duct is also important. This reduces the fan or propeller efficiency because it causes turbulence.3 cm] behind the front bell mouth edge of the duct. A typical duct is 18 inches [45.6 lb [17. A hovercraft is affected by different drag forces depending on the surface it's flying over. a thrust duct must be of an aerodynamic shape and smooth on the inside. causing the thrust output to decrease. • In case of engine malfunction vehicle needs to buoyant above the water. seas while developing effective mobility with a hovercraft. with thrust duck and axial fan.1 SIZE ESTIMATIONS 5. 5. i commenced with gathering worldwide datum.1 . 5. • Because vehicle is multi terrain vehicle. I started collecting datum in order to embody my project. 37 . and beam less than 2 meters.1. • Cockpit for operator. • Have a body length of less than 4 meters. • The vehicle must have minimum Cd (Drag Coefficient).2 BODY DESIGN Cheap and reliable. especially could work in winter conditions in different geographical locations such as rough terrains.1 DATUM • Ability to work in all harsh weather and climatic conditions. The hovercraft that i want to inspect is in personal usage/conventional usage category . CHAPTER 5 5 DESIGN PROCESS I start examining samples that exist in the world because it is an untouched subject in Turkey. • The main body should have the ability to carry 300 kg+ minimum.My goal was to develop a design that could withstand the harsh weather and climate conditions. First of all i began with categorizing the use of hovercraft. • Integrated lift and thrust system. it needs to be water proof. deserts. I aim to create a high quality visual design. snow. Now i have got some datum to start my design. 0-4. After that. dimeonsions that i have chosen has given on the table below. Data gathering process started with over 70+ personal usage hovercraft with the dimensions of between 0-10 for length.5 for beam. L (LENGHT ) 3035 mm B (BEAM) 1524 mm D (ESTIMATED DESIGN DEPTH) 350 mm Mai Main Structural Body Height+Skirt Height (DESIGN VELOCITY) 5 m/s (18 km/h) Table 5 1 38 . i calculated the L/B ratio.94804. ‘alias’ R which is 1. According to my constrains. Table 5 2 Table 5 3 39 . 00 2.00 L (Boy) 6.8063x + 0. 12.00 3.00 B (Genişlik) Graph 5 1 Now i have achieved something to concentrate on and applied a design method to improve it.00 5.3119 10.00 4. 1.00 Linear (Series1) 2.The method is applied to create an iterative and continuos features to design spiral. Figure 5 1 (13) 40 .00 Series1 Linear (Series1) 4.00 8.00 y = 1.00 - . Because axial fan needs to be located in the center of the thrust duck it needs to be risen from the base level of hovercraft. 5.To meet vehicles power need.there is a cockpit and cockpit lever which is inside the cockpit and connected to the rudder behind the thrust duck. therefore engine must be fitted above from the base level. Axial fan is directly connected to engine via shaft.2 GENERAL SETTLEMENT Hovercrafts propulsion system feeds both lift and thrust (integrated propulsion system). There is a feed hole which is supposed to meet the air that skirt needs and there is another gap designed to move air to the loop. Finally . Hovercrafts views are given below. A thrust duck surrounds axial propellers in order to increase efficiency. There is an engine mount plate beneath the engine. Figure 5 2 41 . there is an axial fan system. Figure 5 3 Figure 5 4 42 . Figure 5 5 Figure 5 6 43 . 69037 kilograms. This is why expected power range is high. which is 7. estimated weight is between 200-350 kilograms.This means we need 1 hp for every 7.) Table 5 4 44 .69037. With these datum P/W (hp/kg) ratio has been calculated. So vehicle needs power between 26-45 hp. According to general arrangement.5.3 WEIGHT AND POWER ESTIMATIONS Weight and power estimation process started with combining datum. (I need to remind that most of these hovercrafts are in highs-speed category. over 70+ datum between 130-4700 kg for weight and 8-385 hp for power have been analyzed. use a skirt of one sort or another for their suspension system so that the power required to lift the craft can be minimized. All modern hovercraft –big and small.2 P/W (hp/kg) 0. 45 . Give adequate stability.25 0. 4. 0. Return to its original shape after having been deformed. Have the ability to conform or contour efficiently over obstacles so as to keep to a minimum loss of cushion air. 3.4 SKIRT DESIGN Skirt is the most important part of the hovercraft and extremely related to stability.15 Series1 Linear (Series1) Linear (Series1) 0. Contain the cushion of air beneath the craft at the required hover height.1 0. Offer little resistance to the passage of obstacles through it.1233 0.3 y = -9E-06x + 0. 2. 5.05 0 0 1000 2000 3000 4000 5000 W (kg) Graph 5 2 5. (15) Why have a skirt ? 1. 6. But we will dealt with three main types which are widely for conventional/personal use hovercrafts. There are several major designs of hovercraft skirts. (a) The loop (or bag) skirt (b) The segment (or finger) skirt (c) The loop and segment (or bag and finger) skirt Each of these types of skirt are shown below. (14) Figure 5 7 (14) 46 . Each has its own merits. arrows show path of airflow. Have the ability to absorb a large proportion of the energy which is produced on impacts or collisions with obstacles greater than hover height or cushion depth. when the skirt crumples up as the edge of the craft drops. All three designs use the movement of the center of pressure on the collapse of the skirt to provide stability. Be relatively simple to make and fit to a craft. i. the effective contact point where the skirt touches the ground moves. To do so i need to give brief informations about these three types of skirts. Figure 5 8 (14) How should a skirt be? 1.The initial cost of making the skirt may not be very low but it is important that once made and fitted the skirt can be cheaply maintained. Therefore extra cushion area and thus more lift is provided at that side. One part of the skirt should not drag on the ground whilst another is couple of cm’s above the ground.e. 3. This stiffness is derived from two main sources: 1. 2. moving the center of lift pressure over and tending to raise the craft to restore it to a level position. Be tailored so that it is even in height above the ground all the way around the craft. The loop skirt employs an inflated bag surrounding the air cushion. (14) 47 .5.4. Now I must decide upon the type of skirt material which i will use. 5. This is shown below. 2.1 The Skirt&Stability The stability of a hovercraft is dependent upon the pitch (fore and aft) and roll (side to side) stiffness of the air cushion. Have a long operating life. Able to easily mantained on site without the need to lift or jack-up the craft. 4. Have a low maintenance cost. the pressure of the bag providing stability. It is not limited by obstacles. (14) 5. The skirt gives a very smooth ride and is not limited by obstacles up to cushion depth.4. Usually it gives fairly high drag over undulating surfaces.1.1 Skirt Characteristics This type of skirt fairly simple to design and construct but gives a harder ride than the segmented type and has more limited obstacle clearence.1. .2 The Segmented (or finger) Skirt 5.3.1. i consider affordability.Over undulating surfaces. The inflated loop skirt is very stiff in roll and pitch.1.the loop and segment skirt gives a very smooth ride. stiff grass can reduce the performance of the loop and segment skirt compared to a loop design. Because my first problem is to finance the project.4. It’s roll and pitch stiffness is a little less than for pure segments and as with the latter system it has low drag.Long.5.1 Skirt Characteristics The segmented skirt is simple to design and construct. (14) According to these informations most relaible type of skirt for my design is The Inflated Loop (or Bag) Skirt.If the craft is left afloat the skirt can not fill with water.Easy to attach . ideal for a cruising hovercraft which is required to operate over high speeds due to its poorer stability when compared to the inflated loop skirt. The segmented skirt also has very low drag characteristics and this is particularly noticeable when travelling over obstacles or waves. therefore.4.2.Cheap . It does not hold water within the skirt when floating off cushion.4.particularly water.1. Repair work can also be carried out easily and quickly if quick release attachments are used.It is. (14) 5.1 The Inflated Loop (or Bag) Skirt 5.1 Skirt Charecteristics The most difficult skirt to design and construct.4.1. depending upon the pressure differential between the loop and the air cushion.3 The Loop and Segment (or Bag and Finger) Skirt 5.Inexpensive to maintain 48 .the loop and segment design offers various advantages.1.4. however.1 Description The inflated loop consists essentially of a tube of material (similar in a way to a car inner tube) which is inflated at a slightly higher pressure than the air cushion beneath the craft.The full-flow system (shown below) feed all the lift air into the skirt and from there through small holes in the inner skirt wall into the cushion. Even small tears in this of skirt can . Figure 5 10 (14) How to Calculate the Skirt Cross-section 49 .4 The Inflated Loop (or Bag) Skirt 5.4.4.1.4. The size of the scoop is about %10 of the total lift fan area. The no-flow system (shown below) pressures the loop via small scoops at the tip of the lift fan. By controlling the number and size of the holes it is possible to alter the pressure differential between the loop and the air cushion. lead considerable losses of skirt pressure which in turn could result dangerous instability.1. Figure 5 9 (14) 2. The skirt is sealed and does not have any exit holes since most of the air is fed directly into the cushion. This can be achieved in one of two ways: 1 .Not let’s expand The Inflated Loop (or Bag) Skirt 5. the radius of the outer circle (r) and the inner (R). but the poorer the undulating surface performance of the skirt.0 1. Figure 5 11 (14) The radius of the inner circle (R) is calculated by multiplying the outer radius (r) by a factor given in the table overleaf. In order to calculate the factor i must decide what pressure differential between the loop pressure and the cushion pressure i will use.5:1 3.6:1 2.53 1.3:1 4.5 1. (14) Pressure Differential Multiplying Factor PL / PC R/r 1. The higher the ratio the greater the stability. To do this one must first calculate the height of the skirt.66 1.2:1 6.8:1 2.43 1.0 1.The first is to design the cross-section.4:1 3.7:1 2. For simplicity it can be assumed that the ground contact point of the skirt (GC) is directly below the outer edge of the body. The cross-section of the inflated loop skirt is composed of two radii.25 Table 5 5 (14) 50 . which should be about 1/8 of the width of the craft. This choice is based upon the degree of stability required. Rot proof – able to stand up to immersion in salt and fresh water and then long periods in dry conditions. High tear resistance – the material. Low weight – usually between 113. High abrasion resistance –particularly for operations over concrete. 51 . Flexibility –to form a good air seal to the ground.5 Skirt Material After i have decided to use the inflated loop (or Bag) type skirt. 1. once torn by a stake or root. now i need to calculate the amount of air which is escaping from the gap between skirt and the ground. cheap and reliable materials. sandy beaches. tarmacadam. Non-absorbent.Based upon information given above. to not to lose both from stability and surface performance i have decided to choose multiplying factor 3. must not ‘run’. 4.does not soak up water or liquids which might damage material.3-283 grammes/m2. 7. 6. 5. 3. now i need to decide to use suitable. 5.4.5 LIFT SYSTEM After these steps. Non-porous material will provide fairly airtight seal. 2. (14) According to information given above i have decided to use rubber. The major requirements for skirt material. 5.0. This air has the same amount of volume with the air which is forced to move to the loop + skirt.1. 𝑇𝑜𝑡𝑎𝑙 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐻𝑜𝑣𝑒𝑟𝑐𝑟𝑎𝑓𝑡 𝐶𝑢𝑠ℎ𝑖𝑜𝑛 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 = 𝐴𝑟𝑒𝑎 𝑜𝑓 𝐻𝑜𝑣𝑒𝑟𝑐𝑟𝑎𝑓𝑡 𝑇𝑜𝑡𝑎𝑙 𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐻𝑜𝑣𝑒𝑟𝑐𝑟𝑎𝑓𝑡 𝑖𝑠 𝑎𝑝𝑝𝑟𝑜𝑥𝑖𝑚𝑎𝑡𝑒𝑙𝑦 300 𝑘𝑔′𝑠 𝐴𝑟𝑒𝑎 𝑜𝑓 𝐻𝑜𝑣𝑒𝑟𝑐𝑟𝑎𝑓𝑡 = 3.860 𝑚2 = 13.524 𝐴𝑟𝑒𝑎 𝑜𝑓 𝐻𝑜𝑣𝑒𝑟𝑐𝑟𝑎𝑓𝑡 = 4.291 ⁄𝑓𝑡 2 = 635. Green Highlighted Area: Hull of the Hovercraft Red Highlighted Area : Hover gap Blue Highlighted Area : Ground The air which is forced to go under the hovercraft must have same amount of pressure with the hovercraft so hovercraft can hover.035 × 1.62534 𝑘𝑔⁄ 𝑙𝑏 𝐶𝑢𝑠ℎ𝑖𝑜𝑛 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 = 64.62534 𝑚2 300 𝐶𝑢𝑠ℎ𝑖𝑜𝑛 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 = 4.628 𝑃𝑎 52 . Figure 5 12 Definition of the picture. 22 the density of air in 𝑚2 at sea level and v = velocity of air in 𝑠𝑒𝑐 When wind exerts a force on an object (e.Assuming that the vehicle is designed to hover just 3mm (hover gap) off the floor.3 Velocity Pressure (Pv) 𝑷𝒗 = 𝟏⁄𝟐 𝝆𝒗𝟐 𝐾𝑔⁄ 𝑚⁄ Where 𝜌 (Rho) = 1. (16) 𝑃𝑠 = 𝑃𝑎 − 𝑃𝑜 5. the total are through which the air will escape (Ae) is.003 𝑇𝑜𝑡𝑎𝑙 𝑎𝑟𝑒 𝑡ℎ𝑎𝑡 𝑎𝑖𝑟 𝑤𝑖𝑙𝑙 𝑒𝑠𝑐𝑎𝑝𝑒 = 0.118 × 0.5.5.118 𝑚 𝐻𝑜𝑣𝑒𝑟𝑔𝑎𝑝 = 0. At the point where the flows separate. (16) 5.2 Static Pressure (Ps) For the purpose of fan and air movement engineering.g.000 Pascals (Pa).0273 𝑚2 To calculate the volume of air passing through the hover-gap we need to consider some basic principles of air movement. The wind will flow around both sides of the object.This form of pressure can be particularised as absolute pressure. around chimney) the pressure on the windward side is greater than that on the opposite side.524) × 2 𝑃𝑒𝑟𝑖𝑚𝑒𝑡𝑒𝑟 𝑜𝑓 𝐻𝑜𝑣𝑒𝑟𝑐𝑟𝑎𝑓𝑡 𝑓𝑟𝑜𝑚 𝑡𝑜𝑝 𝑣𝑖𝑒𝑤 = 9.035 + 1.003 𝑚 𝑇𝑜𝑡𝑎𝑙 𝑎𝑟𝑒 𝑡ℎ𝑎𝑡 𝑎𝑖𝑟 𝑤𝑖𝑙𝑙 𝑒𝑠𝑐𝑎𝑝𝑒 = 9. This is called the stagnation point.1 Definition of Pressure Atmospheric air experiences a pressure from the weight of air above it. At sea level this is 1 Bar or 100. there is a point where the velocity is zero. Static pressure is positive when above atmospheric pressure and negative when below. 𝑃𝑒𝑟𝑖𝑚𝑒𝑡𝑒𝑟 𝑜𝑓 𝐻𝑜𝑣𝑒𝑟𝑐𝑟𝑎𝑓𝑡 𝑓𝑟𝑜𝑚 𝑡𝑜𝑝 𝑣𝑖𝑒𝑤 = (3. static pressure can be considered as the difference between the absolute pressure of the point under consideration and atmospheric pressure.5. From the velocity pressure formula (𝑃𝑣 = 1⁄2 𝜌𝑣 2 ) it will be seen that if v=0 the Pv=0 (16) 53 . (16) 5. So equation B can be re-written as (Eq C) Pt2=0+636 Pa and (Tot. As Pt = Ps + Pv any change is Ps results in an opposite change in Pv.628 Pa.=Vel.5. Press. Hence (Eq A) Pt1=636+Pv1 (where the suffix represents the conditions within the cushion) When the air leaves the cushion (Eq B) Pt2=Ps2+636 (where the suffix 2 represents the conditions outside the cushion) As stated above when the air leaves the system all of the static pressure is converted to velocity pressure. These principles are also true for air flowing in a duct. Press. In a ducted air system. Due to friction the duct offer a resistance to the flow of air and the air exerts a static pressure on the walls of the duct. the static pressure falls to zero. at the stagnation point where the velocity pressure falls to zero the static pressure will rise to equal the value of the velocity pressure thereby exerting a force on the object. the fan imparts a total pressure (Pt) rise.628 Pascals. The wind however has velocity and therefore a velocity pressure.) Equation A can be re-written as (Eq D) Pt1=636 Pa +0 (Tot Press.) 54 . Press. This is static pressure exerted on the floor and walls of the plenum formed under the skate. i. When the air leaves the end of the duct it has only velocity pressure which is equal to the pressure. Velocity pressure is always positive. Because the air is flowing through the duct it also has velocity pressure. which is then constant throughout the system.4 Total Pressure (Pt) As the wind is flowing through the atmosphere without exerting force on anything the static pressure will be zero. (16) Applying this to my design: The Cushion Pressure (Pc) is 635.5. So Ps=635.=Stat.e. When it meets an object as above. To do so i need another source.This ignores any velocity pressure within the plenum. (16) To verify this result i need to compare my calculations.289 x 0. 55 . The final conclusions will therefore render answers slightly higher than would be expected in real situations.289 𝑚⁄𝑠𝑒𝑐 1.22 𝑣 2 2×636 And transpose to arrive at 𝑉𝑒 = √ = 32. They have been simplified and take no account of turbulent airflow.22 This is the escape velocity (Ve) of the air where it escapes through the hover-gap at a given cushion pressure (Pc). frictional losses. Knowing that Velocity pressure (Pv2) = 1⁄2 𝜌 𝑉 2 I can re-write equations B and C to form 636 = 1⁄2 1. or variations in air density. The Volume of air lost (Vol) = Escape Velocity (Ve) x Escape Area (Ae) Vol = 32.881 𝑚3 𝑠𝑒𝑐 This value is the same amount that we need to provide for lift. but as this tend to be very low in comparison with the cushion or static pressure. neglecting it makes very little difference to the final calculation.0273 = 0. The calculations above are based on ideal airflow. 1 32.289 As we can see from the calculation above. 32. 56 . the ratio is unacceptable. Table 5 6 (17) According to HOVERHAWK calculator. we see huge difference among velocities.289 − 20.299 %=| 𝑥 100| = %37. so that the pressure is simply atmospheric pressure and the pressure difference due to height is neglected. 𝑉𝑒𝑠𝑐 = 0. Dc is the discharge coefficient and ρair is the density of air.61 𝑥 32.696 One step further for escaping air volume.299 New ratio. Therefore our formula becomes.0273 = 0. The discharge coefficient comes from the flow modeled by that of an orifice leading to an approximated Dc of 0. %=| 𝑥 100| = % 3 19. (18) 2𝑥𝑃𝑐𝑢 𝑉𝑒𝑠𝑐 = 𝐷𝑐√ 𝜌 Where Vesc is the exit velocity of the air in m/s.5𝐿√𝑃𝑐 𝑓𝑡 3⁄ 𝑚3⁄ Where Q is the flow 𝑠𝑒𝑐 𝑠𝑒𝑐 L is the craft length in feet. The Volume of air lost (Vol) = Escape Velocity (Ve) x Escape Area (Ae) Vol = 19. 𝐿𝑎𝑑𝑒𝑛 𝑊𝑒𝑖𝑔ℎ𝑡 = 𝑃𝑐 𝑇𝑜𝑡𝑎𝑙 𝐴𝑟𝑒𝑎 For craft having a typical platform (i.e.696 𝑚⁄𝑠 19.metres 𝑙𝑏⁄ 𝑘𝑔⁄ Pc is the cushion pressure in 𝑓𝑡 2 𝑚2 57 .537 𝑚3 𝑠𝑒𝑐 Applying separated systems lift calculations.I need to evaluate orifice effect.61 (18) Now i calculate in line of formula given above. an estimate of the airflow requirement may be obtained from the following equation: (14) 𝑄 = 3. The velocity is assumed to be zero at an arbitrary distance from the craft.289 = 19.696−20.696 x 0. length approximately twice craft width). 5 Estimation of Fan Pressure Requirements The static pressure requirement from the fan will depend upon the type of skirt fitted to the hovercraft.2𝑃𝑐 For a no-flow pressurised loop skirt.5 times the cushion pressure.860 𝑚2 = 13. 𝑃𝑠 = 1. the fan pressure requirement is the skirt pressure.613 𝑚 ⁄𝑠𝑒𝑐 air to plenum chamber in order to lift the vehicle.2 to 1. where most of the lift air is fed directly into the cushion and only a small amount is taken off at a higher pressure into the loop itself. (14) 5. 58 .This equation gives a minimum flow to be aimed for providing the craft has an efficient skirty system. where the air is fed into the cushion via the loop. the fan pressure requirement can be regarded as equal to the cushion pressure (Pc) For a full flow pressurised loop (or bag) skirt.5 × 10 × √13. (14)  My system has no-flow pressurised loop skirt.291 ⁄𝑓𝑡 2 Skirt Type no-flow pressurised loop skirt Table 5 7 𝑄 = 3. which is normally 1.5. the fan pressure requirement is the cushion pressure.291 𝑓𝑡 3⁄ 𝑚3⁄ 𝑄 = 127.613 𝑠𝑒𝑐 3  So my engine must transfer 3. therefore Pc=Ps Craft Length 3035 mm (10 feet) Cushion Pressure 𝑘𝑔⁄ 𝑙𝑏 64.6 𝑠𝑒𝑐 = 3.5𝐿√𝑃𝑐 𝑄 = 3. For an ‘open’ skirt of the pure segment or loop and segment type where the lift air is dumped directly into the plenum chamber. ’ (14) According to information given above.7 kg) of thrust per 1 bhp used).690 lb (37. (A typical multi-bladed ducted fan will give 4-6 lbs (1.521 lb (300 kg) Thrust Needed 82.6 PROPULSION SYSTEM Because of the amphibious possibilities inherent in the hovercraft principle the apparently most obvious choice of propulsion system is the air propeller and many early craft were propelled by existing aircraft propellers. This thrust figure should be doubled for racing craft.375 kg) Table 5 8 59 .4 kg) of laden craft weight.6 kg) for every 400 lbs (181.8-2. ‘The static thrust of the propulsion system should be more than 50 lbs (22.5. Total Weight of the Vehicle 661. (15) According to my power estimation graph my vehicles power requirement is between 26-45 hp. Table 5 9 (19) (20) 60 . If the air at the inlet already has some momentum.6. I will give a brief information about the thrust components and thrust. this difference is referred to as ‘momentum drag’ (Dm) 𝐷𝑚 = 𝑄𝑑 𝑥 𝑉𝑜 𝑥 𝜌 Where: Vo=the ‘Free stream Velocity’ (19) 5. The basic equation for Gross thrust is .6. i am going to calculate my own gross thrust for comparison. the fan is unable to increase its velocity by the same amount. 𝑇𝑔 = 𝑄𝑑 𝑥 𝑉𝑑 𝑥 𝜌 Where : Tg=Gross thrust (exclusive of drag or losses) Qd=Quantity of air at the discharge Vd=Discharge velocity (Efflux velocity) 𝜌 (𝑟ℎ𝑜) = 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝑎𝑖𝑟 (19) 5.2 Momentum Drag A thrust far works by taking still air from in front of it and using the fan blades to increase its pressure and velocity.3 Net Thrust The Net Thrust (Tn) is the gross thrust less the momentum drag (Dm) Therefore Net thrust is given by : 𝑇𝑛 = (𝑄𝑑 𝑥 𝑉𝑑 𝑥 𝜌) − (𝑄𝑑 𝑥 𝑉𝑜 𝑥 𝜌) Which can be rewritten as: 61 .31 𝑚⁄𝑠𝑒𝑐 . 5.According to chart discharge velocity is 25.1 What is thrust ? Thrust is the force applied by the volume (mass flow) of air passed at the discharge of the fan. To verify this datum.6. 81 𝑥 (𝑉𝑑2 )]⁄ 82. the losses must be taken into the equation.664 𝑥 𝑉𝑑 𝑉𝑑 = 21.e.4 Static and Dynamic Thrust Static thrust is the measured thrust with the craft stationary and is equal to the gross thrust. For Dynamic thrust. with the free stream velocity=zero.82 %=| 𝑥 100| = % 2. Vo’.664 𝑥 𝑉𝑑 𝑥 𝑉𝑑 𝑥 𝜌 𝑄𝑑 = (0.46)2 𝑥 𝜋 𝑥 𝑉𝑑 = [0.35 21. i.) 62 .309 − 21. (Free stream velocity). Assuming a still day.309 As we can see from the equation. 21.309 𝑚⁄𝑠𝑒𝑐 (19) Note: These calculations are for separated lift systems so i need to compare my result with red highlighted velocity.6. 𝑇𝑛 = 𝑄𝑑 𝑥 𝜌 𝑥 (𝑉𝑑 − 𝑉𝑜) The quantity of air (Qd) can be calculated from 𝑄𝑑 = 𝐴 𝑥 𝑉𝑑 Applying these to my design. i ignore wind and other conditions which affect the ‘Free Stream Velocity. 5. Note: In these calculations. So the static thrust figure will not alter (except from the effect of losses due to any additional obstructions etc.4482 𝑄𝑑 = 0. 𝑇𝑔 = 𝑄𝑑 𝑥 𝑉𝑑 𝑥 𝜌 𝑄𝑑 = 𝐴 𝑥 𝑉𝑑 𝑇𝑔 = 0. my calculation is extremely accurate. To from any useful reference it must be measured in still air conditions. Momentum drag will also be zero. the air some distance in front of the fan will have zero velocity.690 4. 81 𝑥 (𝑉𝑑 − 10)2 ]⁄ 82. Adapt this to my design.690 4.4482 𝑉𝑑 = 31.664 𝑥 (𝑉𝑑 − 10 )2 𝑥 𝜌 = [0.309 𝑚⁄𝑠𝑒𝑐 Applying this discharge velocity to table in order to find Thrust.g. (19) 𝑇𝑔 = 0. 63 . 10 𝑚⁄𝑠 the losses must be calculated and substracted from the static thrust. Rewriting the formulas for 10 𝑚⁄𝑠 headwind.If the free stream velocity is greater e. Table 5 10 (19) (20) 64 . First i applied my discharge velocity to find the total thrust which is highlighted in dark yellow. the lift area could be calculated and subtracted from the fan area. To find the percentage used for thrust. but in practice this does not happen because the outer portion of the blade is moving at a higher velocity. which reduces the Figure 5 13 volume.6.5 Calculating Duct Areas On an integrated lift design. An ideal fan blade would produce the same pressure and volume of air from infinite points along its length.09 𝑚⁄𝑠𝑒𝑐 . 1. the discharge from the fan is divided. After finding total thrust (175 lb) I applied this value to integrated lift table at the bottom of the chart.10 65 . (82. According to Modified Thrust table highlighted in purple.690 to 174) 5. my designs discharge velocity is supposed to be 35. 4. but this rarely gives accurate results. So my engine specification needs to be 3300 RPM with 6 Bladed fan with 30° pitch. So in 10 𝑚⁄𝑠𝑒𝑐 headwind the fan thrust our thrust need has more than doubled. pressure and load produced at the tip. 3. (19) 3. 2. Twisting the blade along its length corrects this to some degree by allowing the end of the blade to run at a shallower pitch. Part of the lower portion of the fan is used to provide lift and the rest provides thrust. This technique works well for a particular amount of twist in a blade rotating at one specific speed.67 𝑥 100 ≅ %20 16. It produces the cushion much earlier than the 6-blade fan and in the midrange fan speeds produces a greater volume of air which may be useful when negotiating undulating surfaces at lower speeds. It produces more thrust and almost the same lift volume as the other fan. the 9-blade fan might be better choice. If the craft were to be used for cruising and generally at lower speeds. According to information given above i have chosen 9 bladed fan.92 cm Splitter Length=78.6 Fan Solidity The solidity of the fan is percentage of the disc space. which is filled with blade but the term is generally used to refer to the number of blades fitted as a fraction of the total possible.08=23.08 cm h2=46-22. The greater the solidity of the fan the more power it will absorb and hence for a given amount of power. If the craft were to be used for racing or for ultimate performance the 6-blade fan would be the obvious choice.6. the pitch must be of a shallower angle or the rotational speed reduced.58 cm 5. (19) 66 . Figure 5 14 Figure 5 15 (19) So h1=22. The low speed performance would be immaterial. 00088265 965 19 19 low density wood 18335 348365 0.4 low density wood 69540 445056 0.05817 0.00483 9.00285521 419 38 38 medium density wood 15922 605036 0.00034747 3035 38 6 plywood 115330 691980 0.00891577 1524 610 3 plywood 929640 2788920 0.00147218 533 406 3 plywood 216398 649194 0.00068 4.01592 0.01254 0.00278892 2420 356 3 plywood 861520 2584560 0.00016646 864 813 3 plywood 702432 2107296 0.2164 0.00012166 254 229 3 low density plywood 58166 174498 0.0021073 2250 854 6.11533 0.03657 0.0064 0.9215 0.4 plywood 1921500 12297600 1.0104 0.95174 0.97192 0.70243 0.00054855 114 6 7 medium density wood 684 4788 0.05791 0.1694E-05 2438 15 15 low density wood 36570 548550 0.00069673 2445 19 19 low density wood 46455 882645 0.00044506 425 38 32 low density wood 16150 516800 0.00111325 1016 483 3 plywood 490728 1472184 0.00052875 610 114 6.18438 0.86152 0.08924 0.00060504 838 152 3 plywood 127376 382128 0.00023826 127 38 19 low density wood 4826 91694 0.37108 0.00023302 2426 76 3 plywood 184376 553128 0.00034837 914 406 3 plywood 371084 1113252 0.0001745 485 184 3 plywood 89240 267720 0.0122976 Table 6 1 67 .788E-06 372 254 3 plywood 94488 283464 0.0005168 330 38 19 low density wood 12540 238260 0.00258456 1249 762 3 plywood 951738 2855214 0.12738 0.06954 0.74359 0.03525 0.00318 6.00069198 337 19 19 low density wood 6403 121657 0.09449 0. CHAPTER 6 6 MATERIALS BOY EN KALINLIK ALAN HACİM ALAN HACİM Malzeme (mm) (mm) (mm) (mm^2) (mm^3) (m^2) (m^3) 2438 305 3 plywood 743590 2230770 0.49073 0.01615 0.01834 0.00038213 2350 15 15 low density wood 35250 528750 0.92964 0.00223077 2438 1219 3 plywood 2971922 8915766 2.00055313 965 38 19 low density wood 36670 696730 0.03667 0.00026772 1022 76 3 plywood 77672 233016 0.00064919 127 25 19 medium density wood 3175 60325 0.0325E-05 102 102 16 pine 10404 166464 0.00028346 1524 38 6 plywood 57912 347472 0.04646 0.07767 0. 00 TL WOOD BRACING FIN 2 10.00 TL STEEL OR ALUMINUM BRACKET LEFT 1 0.00 TL WOOD RUDDER BRIDGE UPPER 2 10.50 TL PLYWOOD 3 mm FRONT INFILL 1 15.75 TL PLYWOOD 3 mm SKIRT ATTACHMENT STRIP F/R 2 31.25 TL FOAM 51mm HULL FOAM BLOCK 5 1 26.17 TL PLYWOOD 3 mm MAIN DECK PANEL 1 1 36.75 TL PLYWOOD 3 mm SKID MOUNT SIDE 2 31.00 TL WOOD SKIRT MOUNT SIDES 2 10.75 TL PLYWOOD 3 mm SKID MOUNT FRONT 1 15. CHAPTER 7 7 COST ANALYSIS PRODUCT PART AMOUNT COST PLYWOOD 3 mm MAIN DECK P3 1 36.50 TL WOOD SUPPORT 2 10.30 TL FOAM 51mm HULL FOAM BLOCK 3(LF) 1 26.00 TL PLYWOOD 16 mm ENGINE MOUNT 1 36.00 TL WOOD RUDDER BRIDGE LOWER 2 10.34 TL PLYWOOD 3 mm COCKPIT TOP 1 36.17 TL PLYWOOD 3 mm COCKPIT SIDE 2 72.30 TL 68 .00 TL WOOD STRINGER TOP 2 10.50 TL PLYWOOD 3 mm SKIRT ATTACHMENT STRIP SIDE 2 31.30 TL FOAM 51mm HULL FOAM BLOCK 4 1 26.50 TL FOAM 51mm THRUST DUCT 1 26.17 TL FOAM 51mm HULL FOAM BLOCK 1 1 26.00 TL WEDGE WEDGE 4 PLYWOOD 3 mm SEAT BACK 1 15.30 TL PLYWOOD 3 mm AIRBOX BACK 1 15.30 TL FOAM 51mm HULL FOAM BLOCK 6 2 52.00 TL PLYWOOD 3 mm AIRBOX INFILL 2 31.17 TL PLYWOOD 3 mm MAIN DECK PANEL 2 1 36.00 TL WOOD NOSE BLOCK 1 5.50 TL WOOD SKIRT MOUNT FRONT 1 5.17 TL WOOD ENGINE POST 1 0.75 TL PLYWOOD 3 mm AIRBOX SIDE 2 31.30 TL WOOD STRINGER BOTTOM 2 10.75 TL PLYWOOD 3 mm AIRBOX TOP 1 15.00 TL FOAM 51mm HULL FOAM BLOCK 2(RH) 1 26.00 TL WOOD SKIRT MOUNT REAR 1 5.60 TL PLYWOOD 3 mm STIFFENER 1 36.17 TL STEEL TUBE 1" STEERING STICK 1 6.00 TL STEEL OR ALUMINUM BRACKET RIGHT 1 0. 5 or Ø5/16" x 2 12.40 TL FOAM 51mm RUDDER 2 52.56 TL ∅8mm x 63.50 TL ∅19mm WOODEN DOWEL 4 20 TL 127mm LONG ∅6.05ml 6 TL 69 .75 TL NEOPRENE COATED NYLON SKIRT FRONT 1 10 TL NEOPRENE COATED NYLON SKIRT SIDE 2 20 TL ALUMINUM FERRULE 2 NEOPRENE COATED NYLON SKIRT REAR 1 10 TL HOVERCRAFT ASSEMBLY 1 EXPLODED 12.80 TL ALUMINUM LANDING SKID 4 ALUMINUM FRONT HANDLE 1 ALUMINUM HAND THROTTLE 1 STEERING SUB-ASSEMBLY 1 16mm PINE STEERING BLOCK 1 10 TL STAINLESS AIRCRAFT STEERING CABLE 1 21 TL STAINLESS AIRCRAFT THROTTLE CABLE 1 21 TL ALUMINUM FRONT ATTACHMENT 1 CONTROL ASSEMBLY 1 PLYWOOD 3 mm DUCT BASE 1 15.37 TL 2.5" UNF BOLT ∅8mm or Ø5/16" UNF NUT 2 2.5mm x 38.5" UNF BOLT ∅6.988.00 TL NYLON Æ19mm SPACER ID 10mm LONG 2 36.5 hp motor 848 TL 1.09 LEAF 1 1 TL THICKNESS(13 GAUGE) SAE 30 OIL 0.1 or Ø1/4" x 3 6 TL 1.75 TL CARDBOARD OR PLYWOOD SKIRT CORNER 0 PLYWOOD 3 mm BODY BASE 1 15. ALUMINUM RUDDER TIE BAR 1 WOOD RUDDER ARM 2 10.60 TL 40 X 40 X 2 STEEL OR SCREEN 1 18.00 TL ALUMINUM 3 PINE LAMINATION PROPELLER 1 STEEL OR ALUMINUM PROP HUB 1 RUDDER SUB-ASSEMBLY 1 THRUST DUCT ASSEMBLY 1 ENGINE MOUNT SUB-ASSEMBLY 1 HULL ASSEMBLY 1 BODY ASSEMBLY 1 NYLON STRAP PURCHASED HANDLE 4 72.5mm or Ø1/4" UNF NUT 3 2 TL HINGE . 43 TOTAL TL Table 7 1 70 . GLUE EPOXY 1GAL 6 TL 3/4 x #18 NAILS 1 OZ.D.496.5mm Ø3. Ø921mm or Ø36-1/4 x 1/2" 1/2" PLYWOOD 2 1-1/4" SHEET ROCK(DRY DUCT ASSEMBLY 32 20 TL WALL) SCREWS PULLEY 4 NEOPRENE ADHESIVE HARRAD 628 473 mL 20 TL PULLEY WEDGE 1 1/2 x @ 30° 4 1/4-20x3 HEX Z GRADE 5 16 13 TL BOLT 1/4-20 NC HEX Z NUT 16 2 TL 8-32 x 3 [M4 x 0.8mm HOSE CLAMP 1 2 TL 1/2 x #6 200 BOLTS ? NUTS ? FENDER WASHERS 30 20 TL FIBERGLASS (FINE) CLOTH 8YDS 125 TL FIBERGLASS (COARSE) CLOTH 12 YDS 180 TL 2 x 1-5/8" 14 GLUE CONTACT CEMENT 1 PINT 6 TL 25mm or WIDE STRAP 1" NYLON 40in 20 TL STRING ABOUT Ø1/16" OR NYLON 60 FT. STEEL 4mm I. 16 TL Ø1. CABLE CASING 9245 mm 5 TL 1/16in AIRCRAFT CABLE STAINLESS STEEL 364in 8 TL Ø50.07] NUT 16 2 TL 2.07 x 76] 16 13 TL BOLT 8-32 NUT [0.0mm x 25mm or Ø1/8"x1" COPPER 6 TUBING URETHAN FOAM EXPANDING FOAM SEALANT 12 OZ. producing prototypes and test it on harsher conditions. net thrust. it is possible to produce a vehicle with such high technology by extremely low budget. general arrangement. engine decision phase. lift calculations. in all geographical locations while saving energy time and money. The failure of the operation can lead to irreversible consequences such as injuries. The next phase of my project is. I have designed cheap. i aimed to design a vehicle which could operate under every possible condition. splitter plate location. skirt calculations. manoeuvrable. sustainable. 71 . thrust calculations. In light of these I started my project with the conceptual design phase. losses and fatalities. I aimed this hovercraft to work in extreme conditions. skirt material. number of fan blades. power estimations. I have achieved my goals. They mostly stem from the difficulties in transportation or using the wrong vehicles in different geographical conditions. In this project. fan decision phase and finished with materials and cost analysis. reliable vehicle. gross thrust. I have calculated the escape velocity. flow rate. I have seen that. CHAPTER 8 8 CONCLUSION There are major problems and shortcomings in rescue operations. size estimations. com/applications/commercial.aspx. Marine Hovercraft Technology. Calculator.org. basım yeri bilinmiyor : Maverick Publications. The Hoverclub of Great Britain.griffonhoverwork..htm.org/infoinstructors/guide4. http://www. TRILLO. [Çevrimiçi] 10.discoverhover. http://www. Lift Calculations.org/infoinstructors/newguides/guide19-drag. 20. http://www.html. [Çevrimiçi] 18. P. http://www..edu/3541471/Hovercraft_-_Project_Work .org/infoinstructors/guide7. Hovercrafting As a Hobby. http://www. 8. J.academia.htm. Fan Performance Chart – Multi-Wing 900/6-12/5Z/PAG.aspx. [Çevrimiçi] 7.aspx. 9. 2004. [Çevrimiçi] 6. LIGHT HOVERCRAFT HANDBOOK. 19. 15.T. http://www. http://www. http://www.griffonhoverwork. 4. 2. London : LEONARD HILL.org/. http://www. FitzPatrick. Thrust Calcuations.discoverhover. 1971. [Çevrimiçi] World Hovercraft Organization. Factor: Piece for a Jigsaw III . 1974. HOVERHAWK Hovercraft Air Cushion.discoverhover. [Çevrimiçi] 72 .htm. Perozzo. London : s. [Çevrimiçi] 12.com/lcalc.discoverhover.htm. http://www.n. Hovercraft Club of Great Britain. [Çevrimiçi] 14.worldhovercraft. Benini. P.org/infoinstructors/guide5. http://www. 16.globalspec. 17. Ltd. 21.neoterichovercraft. [Çevrimiçi] 5.discoverhover. 1995.com/applications/military-and-paramilitary. http://www. [Çevrimiçi] 13.com/reference/25982/203279/part-1-introduction-to-shipbuilding.FitzPatrick.hoverhawk. [Çevrimiçi] 11. ROBERT L. http://www. Hovercraft Club of Great Britain.html.com/applications/rescue. The A. References 1. James.griffonhoverwork. [Çevrimiçi] 3.com/general_info/historyof. 1992 Foreign Language : English.com 73 . CURRICULUM VITAE PERSONAL INFORMATION Name Surname : Mustafa Çağrı Ardıç Date of birth and place : 11.05. Italian E-mail : mcagriardic@gmail.