Make Hovercraft

Make Hovercraft
People get blown away by hovercraft - do they fly, or levitate?

Many schools start projects to build hovercraft to challenge pupils to consider the many aspects of product design. Hovercraft are very weight dependent vehicles, so if they are too heavy, they don't fly, if they are too light, they lack durability and break too easily.

Building a hovercraft is a very challenging task; ofcourse they can be as simple as fixing an electric leaf blower to a circular piece of plywood with a hole in it, but having to plug in a power cable can limit the distance you travel!

Home made hovercraft need a power source - as previously mentioned, but I'll say it again, hovercraft are weight dependent, so using a powerful engine will probably result in the hovercraft design being too heavy. During the Olympics, you will observe that most athletes are sort of thin - it is true that fatter athletes eat more calories so have more power available, but like hovercraft, fatter athletes have more weight to carry, so a lot of the additional energy is used shifting the athletes own weight - same as hovercraft. A successful hovercraft design needs to be durable but lightweight.

There are plans available for hovercraft, but hovercraft construction has to consider many aspects.

Weight versus durability - if hovercraft are too lightweight, they break too easily, but durability cannot allow for the hovercraft design to be too heavy, it is important to get this detail right in the design stage.

Safety - last year in New Zealand, a self build hovercraft project ended in disaster when the hovercraft builder was struck on the head by the fan blades. Some manufacturers cut corners on safety by not fitting a rear fan guard - reason being that fan guards slow the air through the duct - by leaving a fan guard off, they can fit smaller cheaper engines, and get more air through the duct, but there are problems with this approach. Hovercraft need maximum power to start on water, to get over the pressure wave known in hovercraft circles as "The Hump". You need power in reserve to get over hump, so if your hovercraft cannot lift the passenger weight, you will need to call out the lifeboat men for a tow to shore (assuming you have a VHF radio or flares pack, mobiles often do not have signals when you need them out to sea). You need to ascertain what the payload capability of your hovercraft is, before using a hovercraft on water, in case you have to stop and restart - no point taking an auxiliary outboard engine, they don't work on hovercraft!

Some hovercraft manufacturers' up-rate cheaper underpowered engines thus invalidating the engine manufacturer's warranty - engine manufacturers do not want their engines to be modified. The best engine to choose is a lightweight engine with high power to low weight characteristics, and this rules out diesel engines. The Rotax 582 microlight with dual ignition is great, or if you must have a more powerful 4 stroke, try the 120HP Turbo from Weber Automotive.

Some suppliers maintain that 4 stroke hovercraft engines are quieter than 2 stroke engines, and this may be so, but you won't hear the difference because hovercraft noise is largely due to the wind rush caused by the fan blade tips. To make a quieter hovercraft, you need a wide unobstructed duct. The hovercraft fans need to be configured correctly, should you fit 6 or 12 fan blades? What pitch angle should the fan blades be set to? If the blades rotate too fast, they will generate lots of noise, plus, above a certain speed, they can disintegrate, so you need to know what the fan blade rotational speed limit is.

Hovercraft skirts can be as a one piece skirt or segmented, the advantage with segmented skirts being than if one were to break, you only need to replace that section, not the whole skirt, sort of damage limitation. Neoprene coated nylon is used for hovercraft skirts by some suppliers, but this is affected and degraded by UV light (sunlight). Hypalon tears too easily, I prefer polyurethane coated nylon weave if you can get it, I use 375 Gsm, it lasts longer, so more cost effective.

Hovercraft DIY projects appeal to engineers, but it can take a lot of time to complete a hovercraft build project. Hov Pod Hovercraft provides sub assembly hovercraft similar to the bare boat principle allowing you to take advantage of their very durable but lightweight High Density Polyethylene (HDPE) hulls in choice of colour. Sub assemblies require you to purchase and fit the engine and optional extras - this approach might save costs, but training is recommended to purchasers of the Hov Pod LM (Local Manufacture)

Ofcourse you could always just buy a professionally designed factory made hovercraft, they are terrific fun, and for sure, you'll be blown away!

For further information please visit our other websites at http://www.hovercraft-hovercraft.com/ or  http://www.hovpod.com/