LIGHTWEIGHT MANUFACTURING
propellers with a variable pitch, larger diameter, reduced noise, while efficient and high power-weight diesel propulsion has replaced gas turbines, with increased use of composites.
WHAT MORE MATERIAL ADVANCES DO YOU FORESEE? Marine aluminium still currently provides the greatest build material for long lasting, robust hovercraft hull design to survive challenging environments. As adhesive bonding allows us to offer increased payload we continue to develop this for larger structures. Aluminium will remain the most effective build material. We are starting to introduce composites into the craft but these do not form part of the structural integrity. On the 995ED most of the topside structure that you see is GRP and has been CRP for some projects. The GHL-patented mixed flow fan is now manufactured from carbon fibre.
HOW CAN PROPS BE MADE BETTER? The propellers on a hovercraft have always been the main source of noise. The noise produced by the props correlate to the tip speed of the blades. Reducing the tip speed would lower the noise level but as a result of this, the thrust generated would be sacrificed. A prop design that does not sacrifice thrust but also produces less noise would be extremely beneficial on a hovercraft. Any reduction in weight would also be advantageous as weight is the single most important variable in hovercraft design and operations.
ARE LUBES IMPROVING IN MARINE ENVIRONMENTS? Yes, recently we have worked with one of our propeller suppliers to change the grease and lubricants that are used on the hub of the propeller. The new improved grease should equate to a longer lasting product in the marine environment.
WHAT’S THE LATEST IN MARINE DIESELS? Tier 4/IMO III marine engines are the latest diesel engines in the marine industry producing the least amount of toxins into the atmosphere. Tier
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The 12000TD is the word’s newest passenger hovercraft, operating with Hovertravel in the UK
4 engines are fitted with Selective Catalyst Reduction (SCR) amongst other technology to reach the latest guidelines set out by the IMO.
WHAT OPTIONS ARE THERE FOR ALTERNATIVES? Griffon already manufacture a diesel- electric hovercraft, the 995ED. Unique to this model are its two standard power modules each containing a diesel engine driving an integral lift fan and electric generator. Alternative fuel options such as
biofuel, compressed air, alcohols and others are constantly monitored by the design team but this technology is currently impractical for hovercraft use. The weight, power and cost penalties are too great compared to traditional fuels but this sector will most definitely evolve in the years to come. Looking to the future, new technology
to allow for fully electric hovercraft is approaching; we are working to ensure we are ready to utilise this.
WHERE ARE WE WITH MARINE BATTERIES? Batteries are entirely feasible in terms of technology readiness, but less so when it comes to hovercraft operations. The current energy per unit weight (kWh per kg) in modern batteries only allow for extremely time-limited hovercraft expeditions, therefore conventional diesel engines remain superior for power to weight ratios.
Although this sector is rapidly evolving and a fully electric hovercraft could very much be viable in the coming 3-10 years.
WHAT ABOUT FUEL CELLS? Whilst hydrogen fuel cells have plenty of advantages such as very low vehicle emissions other than water vapour and a high fuel economy, this technology is still incredibly expensive. It also requires extremely high
pressure, on-board hydrogen storage which is difficult in a vehicle such as a hovercraft that is constrained by volume and weight. Hydrogen is expensive to transport and there is no infrastructure in place to refuel a hydrogen vehicle. This is also another technology that we expect to rapidly evolve and become viable in the near future. Unlike other maritime transport,
hovercraft do not require the same level of infrastructure to operate. Rather than relying on dredged channels, docks or pontoons, they can fly over the undisturbed marine environment to land on unprepared beaches or slipways. Whilst still reliant on diesel engines
for lift, when accounting for the wider picture hovercraft allow for environmentally-sensitive operations. We continue to incorporate the latest technology and innovations to ensure our hovercraft range is as green as possible and compliant with environmental regulation. ●
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