UK patent GB2508660

Advantages of the WindFly Rig

No heeling moment is applied to the boat

This page provides a summary of the advantages of the WindFly Rig relative to a conventional sail rig. A more rigorous analysis is provided in the documents available on the download page. 

No heeling moment is applied to boats that use the WindFly Rig. The WindFly Rig can be mounted on a boat in such a way that leeway is eliminated. Boats using the WindFly Rig are able to plane upwind as well as downwind. The WindFly Rig can be fitted to commercially available 'off the shelf' boats in place of the outboard motor. The WindFly Rig takes approximately the same time to rig as a conventional sail rig.

In short, boats that use the WindFly Rig are:

  • Fast

  • Safe

  • Practical

  • Comfortable

  • Fun

 

The WindFly Rig ensures that the line of action of the force from the kite (or wing) acts directly though the centre of the keel. Therefore no heeling moment is applied to the boat.

  • Ballast can be reduced or omitted

    • ... lighter boat, less resistance

    • ... for a lighter boat planing is practical for 'standard' yachts and dinghies, if they have a suitable hull form

  • No wind induced heel

    • ... no heel resistance

    • ... better comfort

  • Less prone to knock down and capsize in heavy weather

  • A very large kite or wing may be used to provide a larger drive force

  • Narrower hulls are possible for displacement craft

    • ... added resistance in waves is reduced

    • ... better motion with reduced pitch and roll due to waves and reduced slamming in heavy seas

    • ... improved self righting capabilities are possible

 

  • Faster

  • Much faster

  • Faster

  • More comfortable

  • Safer

  • Faster

  • Faster

  • More comfortable

  • Safer

No leeway

 

A combined ‘keel-rudder’ can be used to steer the boat and also resist the sideways component of the load from the kite or wing. There is no requirement for leeway of the entire vessel to generate lateral loads on a fixed centreboard or keel and so balance the sideways wind load: Leeway can be eliminated.​

  • The boat travels through the water along the axis of the hull

    • ... more direct course

    • ... less resistance as no vortex shedding as the water flows across the hull

  • A deep V hull form can be adopted without increasing resistance due to vortex shedding as water flows across the hull

    •  ... a deep V hull form reduces pounding in waves

    • ...  a deep V hull form improves course keeping in heavy seas further contributing to a more direct course

  • Faster

  • Faster

  • More comfortable

  • Faster

Plane downwind, plane upwind

 

The drive force can be applied at approximately constant location and inclination relative to the hull.  There is no difference in the operation of the WindFly Rig whether the boat is travelling downwind or upwind.​

  • Plane upwind as well as downwind

  • Much faster

Fits to 'off the shelf' motor boat hulls

 

If the rig is appropriately proportioned the drive force may be applied at approximately the same location and inclination relative to the hull as the drive force applied by an outboard motor.​

  • Mount in place of the outboard motor on 'off the shelf' hulls 

  • Practical

Rigging time

 
  • The WindFly Rig takes approximately the same time to rig as a conventional sail rig.

  • Practical