On the BillRM matter, can we all agree he's clearly a troll?
Correct. Full stop.
Despite being nearly illiterate, he does understand some scientific concepts; but he seems to lack the ability (or willingness) to supplement what he already knows with new information. His inability to think outside of the box is punctuated by his unwillingness to try.
I think the problem people are having "getting" this particular solution is the false dilemma of perpetual motion (energy from nowhere.) This machine accomplishes no such thing. If we take friction out, for understanding's sake, it's really just a series of simple machines, with basic equations.
If the normal "sail" area of that prop operates at 50% efficiency (arbitrary guess); then let's observe the twin purposes of the prop (it acts as a sail, and a propeller.) The problem with a standard sail, is obviously that as the vehicle approaches wind speed; the propulsion becomes negligible, so catching more wind wouldn't really do any good. Now consider that a fixed windmill with a 10 times larger "sail" area would be able to harness 10 times the power. In order to counteract the acceleration problem with the fixed sail; the propeller version takes, say, 1/3 of the wind's power and converts it to power that blows directly back at the wind. Now if the entire apparatus operates at 50% efficiency; you still have well more than doubled your effective propulsion.
Once conceived, all the engineers had to work out was the proper ratios.
They now could indeed increase the sail performance by a factor of 10 times between the relative sail area AND the propulsion they converted from the wheels (minus friction of course.) Providing they could build an apparatus they could safely operate; the ability to exceed wind speed is a mathematical certainty.
Basically, just a slightly more complicated than the simple machine pulley example I drew above. BillRM won’t get it, because BillRM doesn’t want to get it. As is his norm, he’ll continue to forward red herring after red herring while boldly calling others fools as he remains blissfully ignorant of the fact that he’s again displaying his ignorance.