"Andy Burns" wrote in message
o.uk...
ThinAirDesigns wrote:

We subtract the 1/2hp that the prop needs to produce its 10lbs of
thrust from the 1.0hp that the wheels can produce from that same 10lbs
and you have 0.5hp left over for the system losses.

Thanks for the numbers and your skateboarder examples, I think I can grasp
it now, but I'd hate to have to explain it down the pub from scratch ...

You won't explain it from that description as its rubbish.

I can imagine it being done by moving the sail (propeller blades) in such
away that they are effectively tacking across the wind as they would on a
land yacht going sideways but that isn't what is being claimed here.
They are claiming they can develop thrust by removing energy from the
vehicle and that gives the vehicle more energy to make it faster, which is
just daft.