Almost all manufacturers of small hovercrafts describe their
machines using various parameters like engine power, fan
diameter, maximum payload and so on. All these informations are
very useful but say nothing about one of the most important
ability of hovercraft - the ability to start from water with
full load. This ability is described by two parameters: TOH-1
(time over hump with pilot only) and TOH-MAX (time over hump
with full load). During normal water operation a hovercraft
rides on top of the water surface rather than in the water. When
starting up from a stop on water, a hovercraft transitions from
displacement mode (the air cushion generates a “soft” depression
in the water – rather than the damaging “hard” depression caused
by a displacement boat) to full hover mode (flying above the
surface) at a speed known as "hump speed" (usually around 18-20
km/h for most craft). See videos and graph for H37:
This effect does not occur when traveling from land onto water.
Hovercrafts are machines for activities on water or in mixed
mode-land and water. All another technical parameters can be
wonderful but if your hovercraft can't start from water with
full load nothing can help you!- design, engine, fan diameter,
all these informations are in this case useless.
So if you have decided to buy a hovercraft ask the dealer about
video with full start sequence from velocity 0 km/h (after
engine was stopped for minimum 5s!) to the velocity of minimum
30 km/h. Why we should to examine time for increasing the
velocity to 30 km/h?. It's sometimes difficult to recognize
exactly the time point of transition from displacement mode to
full hover mode. If the hovercraft can achieve 30 km/h we can be
sure that it is “over hump”.
The second, but not so critical parameter is the ability achieving
a maximum declared speed.
A buyers guide to Cruising Hovercraft of the HOVERCRAFTCLUB of Great Britain
-Theory and design of Aircushion Craft, Liang Yun, John Wiley
& Sons Inc, NY 2000.