* The centre of the air cushion could be moved inducing a rolling moment.

At one stage in the development HD.2 was fitted with three wheels in order to provide additional control on land but the wheels were not designed to support the weight of the craft.

Wrap-around loop-segment skirt

This was the first hovercraft to use this type of skirt, which had been derived from earlier tests, and has segments the full depth of the cushion. The skirt surrounds the air cushion which is a single-cell plenum chamber without the compartmentation used on earlier craft to give stability in roll and pitch. On HD.2 the peripheral stability is obtained from changes in the cushion area due to deformation of the angled segments of the skirt, as the craft rotates relative to the surface over which it is travelling.

This type of skirt has the great advantage of being easily accessible from outside the craft, even when off-cushion. Individual segments can be detatched and replaced in minutes and a complete new skirt can be fitted within two hours. The skirt material weighs about 1 lb per square yard and is a synthetic weave coated with artificial rubber. In order to reduce the effect of abrasion, delamination and tearing, which frequently occur in a marine environment, segments of a different material are fitted at convenient points on the periphery.

This type of skirt revolutionised hovercraft production from large commercial or military craft down to single seat racers.

Roll Control

The roll control system was initially designed to prevent the craft heeling in a side wind but it has proved to have other valuable uses. At higher speeds the application of roll control induces a sympathetic yawing movement on the craft due to the asymmetric drag from the side segments in the rolled condition and this single control can be used to turn the craft.

Construction

The foredeck and the top of the craft are of a sandwich construction with an expanded PVC core with light alloy facings. Sandwich type material was also used for the bulkheads and the fuel tanks are made of nitrile rubber and are mounted in a box below the plenum top.

Heritage Value

HD.2 is extremely valuable in heritage terms. Its production was largely government funded and many aspects of this craft have been used in subsequent production craft; developments along similar lines still being made today, There is no other craft in the world apart from the first one, the SR.N1, which is currently being stored by the Science Museum, which demonstrates so much in development terms. The craft was the first with the now usual loop segmented skirt which was as important to hovercraft development as the tyre was to the wheel.

Approach to Conservation

Research has been carried out into the correct materials to use for stripping and painting the craft and Courtaulds have provided some materials and funding. This craft was subject to many changes throughout it's working life and it will be preserved in a way sympathetic to the developments it induced. The craft flew on paraffin and unfortunately caught fire on trials, hence the requirement for some restoration work.

Ideal Standard of Care

Since this is a unique craft with a high heritage value it needs to be located in a large building where maintenance access is easy and where it can be professionally restored. It should also be available for public inspection, which has not been possible since it was moved to Portchester.

Present Condition

HD.2 was rescued from an aircraft museum in 1988 and has been stored by the Museum since that time. It is currently in the Portchester barn and is protected from the weather but there is little room to work on the craft and the paint needs to be professionally stripped and replaced.

Area Required for Adequate Conservation Storage

77 m² (11 m x 7 m)
Internal storage: Nil

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