1) PROBLEM STATEMENT :

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2 TABLE OF CONTENT: 1) PROBLEM STATEMENT 2) HOVER THEORY 3) ELEMENTS OF A HOVERCRAFT 4) DESIGN CONSEDERATIONS 5) ELECTRONIC EQUIPMENT 6) HOVERCRAFT BUILD 7) TROUBLESHOOTING

3 1) PROBLEM STATEMENT : To design a remote controlled hovercraft or ACV(air cushion vehicle) that will be tested for speed, maneuverability and handling on various terrains like sand, mud, water, gravel, concrete. Further details are provided on the website

4 2) HOVER THEORY : WHAT IS A HOVERCRAFT? A hovercraft is an amphibious vehicle that can move with equal ease on both land and water or any other terrain. It is also known as an ACV (air cushion vehicle). How does a hovercraft work? A hovercraft works on the air cushioning effect of air trapped at high pressure underneath the hull which seeps slowly through a flexible surface known as skirt.the pressure due to this trapped air is responsible for lifting the craft a few inches above the ground.

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6 3) ELEMENTS OF A HOVERCRAFT : MAIN PARTS OF A RC HOVERCRAFT : HULL It is the main body of the craft which acts as a base for attaching other parts of the hovercraft

7 LIFT SYSTEM The lift system consists of a fan or propeller attached to a motor or an engine,which provides air for filling the cavity underneath the craft (called as plenum chamber) and also for filling the skirts. THRUST SYSTEM THRUST SYSTEM It is the same as the lift system with a difference that it propels the craft forward by the virtue of reaction force applied by the air. The propeller used for generating thrust is generally provided with a duct to increase the velocity of air and hence to increase the thrust.

8 THRUST FAN LIFT FAN SKIRT

9 SKIRT It is the flexible wall that is attached all around the periphery at the bottom of the craft.the skirt prevents the pressurized air from escaping from the plenum chamber. CONTROL SYSTEM This consists of a set of rudders that steer the craft by directing the air from the thrust system toward either left or right which consequently steers the craft.

10 RUDDERS

11 4) DESIGN CONSIDERATIONS : WEIGHT Light weight materials must be used for construction,but at the same time the model must have good strength. PRESSURE IN PLENUM CHAMBER Lift force= pressure x area of the craft Sufficient pressure must be generated so that lift force > weight of the craft MOMENTS As rotating parts are involved.the unbalanced moments particularly due to the lift fan must be balanced to avoid spinning of the craft POWER SYSTEM For lift fan generally motor- propeller system having static thrust > 0.4x(weight of the hovercraft) will generate hover, provided skirts are properly attached. SKIRT DESIGN a bag skirt is generally preferred as it is easy to build and gives good performance DUCT DESIGN The duct although do not have much effect on thrust due to propellers,they must be used for safety from propeller blades. In design a duct should have a decreasing area towards exit, such that velocity of air,leaving the duct increases and hence thrust increases

12 5) ELECTRONIC EQUIPMENT: MOTORS; DC motors used for rc models are categorized as BRUSHED DC MOTORS BRUSHLESS DC MOTORS Of these two motors brushless motors are generally preferred because of High power to weight ratio Low maintenance

13 ELECTRONIC SPEED CONTROLLERS (ESC) These are used for controlling the speed of the motor. They are generally classified on the amount of current they can handle eg. A 30 amp esc can handle 30 amperes of current draw and will burn if current exceeds this value. So while choosing an esc for brushless motor the max. current draw of motor should not exceed the rated value of esc used.

14 BATTERIES: Li-po or lithium polymer batteries are used because of High discharge rates Light weight High charge retaining capacity Li-po batteries are rated by the amount of charge they can store and the discharge rate and the voltage eg. A 11.1v,2000mAh,20C battery can provide 2 amperes of current for two hours at 11.1 volts and the maximum current can be C rating x mah rating i.e. 20 x 2amp= 40 amp

15 RECEIVER/TRANSMITTER : Receiver and transmitter are used to control the electronic equipments on the model. A receiver or transmitter is categorized by no, of channels and frequency of operation. The no. of channels define how many equipments can be controlled through the transmitter A three channel radio is suitable for running a hovercraft

16 SERVO A servo is a kind of electronic actuator that rotates by only a fixed angle,like 45 degrees, from the neutral position. It can hold it s position at an angle and is used in rudder mechanism for the model A 9gram servo is ideal for rudder mechanism

17 BRUSLESS MOTOR SETUP: choosing the right motor Lift motor- a high kv motor is generally used with a 6-7 propeller. Thrust motor-a low kv motor is generally used with a 9-11 inch propeller. Suggested motor setups: Lift motor EMAX CF amp esc +7 x6 propeller EMAX BL2210/25+ 20amp esc+8 x4 propeller Turnigy kv + 10 amp esc + 7 x3.5 propeller Thrust motor Turnigy kv + 20 amp esc +10 x 4.7 propeller Hobbyking 800kv +12 amp esc +10 x6 propeller Turnigy kv+20 amp esc +11 x4.7 propeller Batteries 11.1v batteries with rating from 1800mAh to 2700mAh and a discharge rate of 25-30C I recommended. A 3mm prop saver or prop adapter should be used for attaching the propeller to the motor shaft Prop adapter

18 6) HOVERCRAFT BUILD MODEL UH10F Materials used: Plywood ;thickness -2mm Thermocol Aluminium plate Glue gun or fevitite Polythene Garbage bags (black coloured) Building the hull: The hull is built by sandwiching thermocol sheet in between two plywood sheets using fevicol. The duct (hole ) at the front is for the lift fan

19 MOTOR MOUNT : Aluminium plate is used; DRILL HOLES FOR SCREW MOUNT SECTIONS ATTACHED

20 Now the parts of the mount are joined using nuts and motor is mounted Motor mount for the lift motor is also made using aluminium plate

21 Hull with the motors attached lift fan motor mount

22 BUILDING THE DUCT : Thermocol is used for making the duct. A 9 thick block of thermocol is formed into the required shape by sanding using a sand paper. The thermocol duct is reinforcrd by wrapping thin cotton cloth dipped in diluted fevicol tightly around the duct. REINFORCED THERMOCOL DUCT THRUST MOTOR AND PROPELLER

23 RUDDERS : rudders are made using coro sheets and cycle spokes Coro sheet Passing a spoke through the coro Hinge for rudder

24 Four bar mechanism for synchronizing rudder movement ATTACHING THE SERVO : Completed rudder RUDDER CLEVIS SPOKE SERVO CONTROL HORN

25 SKIRT : The skirt is a bag type skirt made using garbage bag as an alternate any thin airtight material can be used The skirt is basically a round balloon type structure that gets inflated when lift motor is switched on. For inflating the skirt a fraction of air from the lift fan should be directed into the skirt SKIRT (inflated) For step by step skirt construction refer the following link ://

26 SKIRT CUTOUT Join at bottom of the craft SKIRT COMPLETE D Join at the top of the craft

27 ATTACHING THE SKIRT AND DUCT : Glue gun is used for attaching the skirt and duct to the hull,alternately fevitite or any epoxy based glue can be used. skirt is attached using transparent tape. BATTERY CASE DUCT PLENUM CHAMBER PROPELLER SKIRT

28 AIR FLOW FOR INLATING THE SKIRT AIR FLOW FOR LIFT THIS COMPLETES THE BUILD

29 7) TROUBLESHOOTING : CENTRE OF PRESSURE AND CENTRE OF GRAVITY : The centre of pressure is basically the geometric centre of the plenum chamber.but the lift is in general contributed both by thrust due to motor and the pressure force,such that the point where total lift force acts gets shifted towards the lift motor. The centre of pressure and the point of action of lift force must coincide for leveled hovering The line of action of lift force is fixed for a model, the C.G. can be adjusted by moving the battery. INSUFFICIENT TURNING: Increase the rudder area or the servo throw. NO HOVER: Check if the skirts are fully inflated The skirt should allow a minimum amount of air leak from the plenum chamber. check for any rapid air leaks Insufficient power of the lift motor UNCONTROLLED SPIN: Provide a slight rudder trim in direction opposite to spin

30 WHERE TO BUY: RC stuff is available at following sites which deliver in 3-4 days alternate building material Depron foam (BIOFOAM)- available at some stationery shops around ramkote crossroad,hyderabad Coroplast (sunpak or sunboard) SOME USEFUL LINKS:

31 For any queries contact- RAHUL RATHORE rathorerahul345@gmail.com Ph. : There is nothing that cannot be achieved by firm imagination