Personal Hovercraft Plans
Choosing the engine
Personal Hovercraft Plans – If you looking for personal hovercraft plans and are trying to decide what engine to use, you need to be aware that hovercraft are very weight sensitive so any hovercraft design has to take weight into consideration.
Particularly when starting from on-water, hovercraft create a pressure wave called The Hump – so on-water payload is crucial and determined by available power. If you choose an engine that is too powerful, these tend to be heavier than less powerful engines, so much of the power is counteracted by the weight. If the engine is not powerful enough, then the hovercraft will have problems getting over Hump, and you may have to call out the emergency services to help you get back to land. Generally, hovercraft can lift 50% more weight when starting on land – so if buying a personal hovercraft, make sure you know what the on-water payload is, some suppliers fudge on-water payload.
I think the old scat hovercraft used the Rotax 503 air-cooled engine which is no longer in production. Hov Pod switched from Hirth engines to Rotax about 5 years ago, and fit the very popular Blue Top 582 water-cooled engine. Rotax engines are 2-stroke microlight engines that offer high power to low weight characteristics. Microlight pilots trust their lives with these engines, which are highly reliable, with twin ignition systems.
Some folk may suggest that 4 stroke engines are quieter than 2 stroke engines, and as well they might be, but that is academic in this case, since the majority of the noise generated by a hovercraft is created by the air rushing past the tips of the spinning fan blades. If you want a quieter hovercraft, ironically, more powerful engines can push more air through a wider duct for greater air thrust efficiency – the pitch of the fan blade can shove more air through at a lower fan rotation speed. Lower fan blade speed equals less noise, so less powerful engines can make hovercraft noisier by having to spin the blades faster, all very confusing. More powerful engines push more air at lower fan rotation speed, less powerful engines cannot manage the fan pitch angle handled by more powerful engines.
Rotax also produce 4 stroke engines, but they are a little expensive so I prefer the Weber Automotive 120HP Turbo engine. Ships with full computer diagnostics. 4-stroke engines are heavier than 2 stroke engines, so although you have more power, you will not see any notable improvement in top end speed, though we see more lifting capacity when starting on water – the turbo provides power to get over Hump carrying 325 Kgs, and acceleration is much better than the Rotax 582 – however, the Rotax will lift 275 Kgs on water and is a really good engine.
If you buy a hovercraft, make sure that the supplier is providing full warranty, some hovercraft manufacturers modify smaller cheaper engines and invalidate the engine supplier’s warranty – engines are designed to have some power in reserve, they don’t like to live life on max revs all of the time. Neither do I!