In approaching the concept of creating a new small hovercraft operationally capable to fulfil roles in a range of uncertain environments speed, mobility, space and payload all needed to be considered. The issue facing the design and engineering team in accommodating this was to find a way to reduce the weight of the craft which would allow for machinery and payload without endangering the robust structural integrity and performance.
To do this, rebuilding the crafts very foundations, the way a hovercraft's aluminium structure is made was rethought. Typically, marine grade aluminium will be welded together to build a marine vessel's hull but this has severe drawbacks, especially when building hovercraft that draw many similarities to aircraft by needing to create lift. The extreme heat when welding weakens the strength of the aluminium and distorts the entire shape of the hull leading to an overall weaker structural integrity. Welding also increases the aluminium thickness needed to withstand the heat. This adds dramatically to the overall weight used in creating the hull just to keep the structure together. Unfavourable for the standards of the hovercraft we look to make and unfavourable for classification societies.
To overcome restrictive maritime engineering convention the team looked into alternatives that would strengthen the hull whilst decreasing the weight. Adhesive aluminium bonding was found to be a suitable. Despite being widely used in the car manufacturing industry their use on seafaring, marine vessels had not been attempted before. By bonding the hull instead of welding excess weight is cut and the metal's material strength is kept high. For the hovercraft this allows for more payload to be distributed to equipment, personnel and mobility. Despite finding a solution aluminium adhesive bonding was untested in marine environments and for hovercraft, used in tough, often extreme, terrain. Therefore, high requirements were needed to be met to show the hull's new design would survive the environmental challenges.
Through 2 years of testing and development Epoxy adhesive was chosen due to the rigidity and strength the adhesive gave once applied and left to set fully after 7 days. Implemented into the new 995ED Hovercraft design aluminium thinner and bespoke to the crafts requirements were used saving 25% of the original weight. The heat from welding that could distort the structure by as much as 25mm now distorted by less than 1mm.
The 995ED has been the most ambitious hovercraft project to date in looking to improve all aspects of hovercraft design from the electric drive modules and twin azimuthing rotating ducts to the onboard systems control. The vital difference in accommodating these changes has been the lightweight, durable bonded hull. With the experience our design, engineering and manufacturing teams gained from the successful use of aluminium bonding they have been able to speed up the production process and look to implement the technology on other craft and high-speed lightweight boats. With a staff fully capable and confident in understanding the intricacies between both welding and bonding the foundations are laid to execute larger, more complex specialised marine structures with this method.