Hovercraft

Hovercraft is an amphibious vehicle. It is supported by cushion of slightly pressurized air.  It is a craft which is capable of travelling over land, ice and other surfaces. It consists of blowers that can produce large volume of air. Hovercraft runs above the surface because of pressure difference between below the hull and above the hull. Below the hull has high pressure and above the hull has low pressure. Due to this, it will move above the running surface. The hover fans have engines which power the fans. These fans will blow the air towards the underneath of hover craft which causes to lift off to ground. Depending on the power of engines and size of hovercraft, it can lift seven feet into air.

                                                                                                                                   Hovercraft

Basic Principle of Hovercraft

The basic principle of the hovercraft is that moving an object from the ground using air, then it requires less force to move the object. Because the object does not have any contact with the ground, then the surface tension will get reduced. So it is easy to move the object. The friction is also reduced in case of smoother surface. If the surface contains rocks or any other obstacles, then it may cause slow down the vehicle, or even damage occurs in the air cushion vehicle.

To work efficiently, the hovercraft have skirts which is made up of fabric surrounding their bases. These skirts help to keep the pressurizing air from escaping.  

The first practical design for hovercraft invented by British in the year 1950 to 1960. In 1955, the scientific principle behind hovercraft was first demonstrated by Sir Christopher Cockerell.  It has several applications such as disaster relief, military and survey applications and also used for passenger service.  It can be used to transport people and equipments through rough terrains. So it can be utilized in military organizations.  It can be used in water transport instead of boats in order to carry large number of passengers.

Main Parts of hovercraft

• Hull: - It supports whole weight of craft.
• Skirts: - Skirts are airbags inflated by air. It is attached around the craft. It holds air under the craft to form air cushion.
• Lift fan: - Air is pumbed under craft between skirt spaces to create air cushion.
• Propeller:- It enables the forward motion of craft. It is fitted at the top of craft.
• Cabin: - Passengers sit in cabin.

                                                                                                                            Main parts of Hovercraft

Design

It can be powered by one or more engines.  It needs engine power to produce air current which causes the movement of craft.  Small craft have only one engine. In case of vehicles with several engines, one engine is used to drive the fan. The main responsibility of the engine is to lift the vehicle. It is by forcing high pressure air under craft. The skirt under vehicle will be inflated which causes to rise above the surface. Inorder to propel the craft, thrust (forward motion) is provided by additional engines. i.e. it needs two separate engines for forward motion and to create the pressurized air cushion. Some hovercraft has one large engine which performs both tasks. It directs some air to the skirt and the balance air passing out of the back and it will push the craft forward. The larger engine produces single air stream which is split into trust and cushion.

Working principle of Hovercraft

The main working principle is that the craft is lifted by air cushion. At the top of the craft, fans are fitted. These large fans sucked the air into underneath of craft. This air is used to inflate the skirt. When the weight of craft and pressure equals, then the crafts lift up. The air will escape through the edges of skirt. To compensate this air loss, constant air is feeding into the craft. Thus the crafts will lifts up.

                                                                                             Working of Hovercraft

The propeller drives the air down to the hollow skin. The rubber skirt is inflated by air. This air escapes through holes which provides cushion of air under the hover craft. Once lifted, thrust is created to move the craft in forward direction.

Working of hovercraft

The two main principles of hovercraft are lift and propulsion. Lift allows the movement of craft through air cushion. The movement is achieved by the flow of air from top to bottom of craft. To maintain the craft’s stability, a proper amount of air must flow. If the air flow directed under the craft is too high, then the craft will hover too high above the ground. If the air flow directed under the craft is too low, then the craft will remain on the ground. The source of this airflow is a fan and it can be used for lift and thrust. The fan is not a normal fan. Because a normal fan does not blow air straight back. It spins the air in spiral shape. So here uses turbines or stationary blades. It can un-spin the air. 

The stability of hovercraft depends on shape of the body. The stability is high for larger area of base. The speed will increases for longer and narrow shapes. But the stability decreases. The hovercraft with round ends has stability and speed. As stability increases, the speed will decrease. 

The hovercraft will float on a cushion of air which is float due to the force under craft by fan. This is the reason for rising or lifting of craft. The lift amount is depending on the size of craft.

Amount of total weight that can raised by hovercraft = cushion pressure * area of hovercraft

To make the craft function more efficiently, the escaping air from cushion must be limited. So the air is preserved in the hovercraft skirt. The skirt is fabric material which makes the cushion deep and clears the obstacles. The skirt has variety of styles which is in bags or in segments.

The hovercraft has skirt around the body. Air from the top of craft will passes through the chamber and to the skirt produces air cushion. Thus the hovercraft will lift from the surface.

Making of an homemade Hovercraft

Method 1

Materials Required

• Paper cups and plates
• Hot glue stick
• Marker
• Motor
• AA Batteries
• Propeller. It must be fit inside the mouth of paper cup. Otherwise plastic or cardstock is cut to the particular sixe and connected with the motor.
• Connecting wires

Step 1

Take a plastic cup and cut the cup into half lengthwise.

Step 2

Take the paper plate. Place the half part of the paper cup on the paper plate. Then take a marker and trace the cup on the plate.

Step 3

Create a flap by cutting through the trace.

Step 4

The flap is bend back. Place the half cup on the plate and cover the hole. By using tape, the cup is fixed at plate.

Step 5

The propeller is connected with motor and fixed at the mouth side of glass. Place it as close to the mouth side of paper cup. Then only the wind maintains at sides of cup. The propeller is slightly bent to pass the wind into and outside the cup. Make two holes on the paper cup and put two wires through the holes and connect to the motor.

Step 6

Take two batteries and connected in series position. That is the negative of battery is connected to the positive of battery and fix it with tape.

Connect the connecting wires on the positive and negative side of battery.

Place this on a smooth surface. Turn the motor ON. Then it will move in the particular direction.

Method 2

Materials required

• Compact Disc
• Pop top up cap of water bottle or liquid soap bottle.
• Thin cardboard
• Balloon
• Pushpin
• Hot glue gun
• Scissors

Step 1

Take a sports bottle cap (cap from water bottle) and put 2 to 6 holes near the centre using push pin or small nail.

Step 2

Take the compact disc and fix the cap on the top of compact disc and cover the centre hole of compact disc using hot glue gun (little as possible). The cap and compact disc must be air tight to keep air from escaping.

Step 3

A thin cardboard is used to make a collar for the cap by bending or curving it.

Step 4

The hovercraft must place on a clean smooth surface.

Step 5

Inflate the balloon and open part must be twisted and pull it through the collar and fix the open end of balloon on the cap. Make sure the pop top closed. 

Step 6

Let the air out of balloon. Put the craft on smooth surface and pop the top open.

If the hovercraft will not spin or slide easily, then put some large holes in the sports bottle cap. Then the hover craft will slide or spin easily.