Long live the hovercraft

Many will have thought that the hovercraft is dead in all but its military guise. However, hovercraft are still being used as a means of commercial transport and have a number of advantages over fast ferries. These include the ability to operate in higher wind strengths when fast ferries have trouble linking up with their link spans in port and the requirement for no port infrastructure apart from a slipway.

Airports around the world, in particular, still use hovercraft to quickly transport passengers downtown. However, many say that the hovercraft should only be used where its unique amphibious capabilities can be advantageous.

There has been considerable interest in the Hoverspeed cross channel hovercraft, (SRN4) which were removed from service by the company in 2000. There have reportedly been a number of consortiums interested in getting these craft back in operation across the English Channel. One of these interested parties has emerged from among Hoverspeed?s own staff. It has submitted proposals to put the existing craft back into service and to build new craft three times bigger. But what will this entail?

Putting the existing craft back into operation should be relatively straightforward as they have been continuously maintained at their current retirement home, the Hovercraft Museum at Lee-on-the-Solent in Hampshire, UK. The Motor Ship understands the major requirement is for new propellers. However, Hoverspeed is unlikely to want to see the craft back in operation in competition with its own fast ferry services.

It is viable to build a big hovercraft, says Anthony Marchant, managing director of design consultants Cetec in the UK. “But it is a question of whether its makes economic sense,” he adds.

He says that there is an attraction to the craft in North America because of their ability to operate in ice. However noise is a problem. “Even with ducted propellers it is not a quiet beast,” says Marchant.

The environmental downside of noise emissions can, in part be compensated for by the hovercraft?s lack of wash when running at speed. Adding in its ability to break ice is another plus for North American operators.

If you do decide to build, the craft are very weight sensitive because of the capital cost and cost per seat ? get the displacement wrong and the craft won?t get over the hump, says Marchant. Construction materials are also a problem. If aluminium is welded you can?t anneal it afterwards, says Marchant. If you stick it or bond it, the ambiguities of the high speed craft code come into play. Marchant believes the “way it should be done” is to build in composites ? but the ambiguities mentioned above make this unlikely.

Phenolics give off smoke and are not particularly friendly on the shop floor. They also trap a lot of moisture, says Marchant. He explains that the way to look at composites in high speed construction is to protect them with insulation, but he says that the room corner test ? the means by which you prove fire resistance ? is “pretty difficult to do and meet”.

One of the big problems with hovercraft building is that nobody orders vessels in any quantity. Yet they are relatively easy to build. They are basically a large flat platform onto which is mounted a structure for housing cars and passengers. “They are one of the better structures to design ? lightweight and robust, something that you can?t design for but have to do by experience,” says Marchant. “I would love to do it ? it sounds so easy.”

So, are we likely to see the cross-Channel hovercraft back in action? Unlikely. Although they were the fastest way across the channel, fast ferries are a lot quieter and have filled the slot. And Hoverspeed is unlikely to want the competition. Perhaps hovercraft should stick to what they are uniquely qualified for ? operating as amphibious vehicles, which is where they are used by military around the world.