So How does it work?

The concept uses the 'inclined rig principle'. This in NOT a new idea and people have been playing around with the idea since the 1930's.

The traditional sailing concept

The 'inclined rig' principle

Instead of needing forces (usually static weight) to counteract the heeling moment generated by the rig, the inclined principle eliminates the heeling moment by realigning the forces. With no heeling moment, there is no need for a heavy craft, so the boat can be light and the lifting surfaces (sail and keel) can be high aspect (efficient) and pull far greater forces.

Three of the current main competitors (Monofoil, Trampofoil and Sailrocket) use this principle. Macquarie uses a more traditional vertical rig, while the windsurfers fall somewhere in between.

The key to success of using the inclined rig is the practical configuration of the craft and how the various lifting surfaces deal with the rapid accelerations. Getting a craft to operate at a steady speed is relatively simple. Getting a craft to operate at a range of speeds, from zero to 50+ knots, through violent accelerations, while maintaining a stable course, elevation and pitch, is far more complex.

The majority of Windjet's research went into this evaluation, with hundreds of small balsa models, to overcome a number of hurdles.

The craft that we produced is far from the ultimate design that we identified. Instead, it's design criteria was a stable platform, on which to evolve the rig and water foils, while getting some high speed experience. The biggest problems are often unforeseen and only begin to occur when nearing the final 10% of the boats potential, so it is very valuable to get some high speed experience before building the final itteration.

During Weymouth Speed Week

Powered by the option of a solid rig or a kite, the Windjet water craft has great practical flexibility. It can sail on both tacks, upwind and downwind while being able to run in substantial waves, giving it some long distance potential. Planing on it stepped hulls, it accelerates smoothly (but rapidly!) up to 30+ knots. Above 40 knots, it can support and control itself aerodynamically. In theory the craft becomes clear of the water at top speed apart from the keel foil which remains submerged in order to carry the side forces. We are working in partnership with Naish Kites, arguably the best kitesurfing kites in the world, to evolve a kite specifically for this purpose.

Weighing in at 160 kg, the craft can pull over three times its own weight, which means becoming airborne is a real issue if you get it wrong. However it is designed to recover, as has already been proven in a couple of initial airborne adventures!

Leaving the workshop

Sailing in Light winds in Weymouth Harbour