What do you mean by that term? The post does say this:
What this all means is that you’ve essentially gotten energy from the friction of the wheels against the ground, and turned it into propulsion. The ground friction is providing a way to make the propellor “tack” against the wind. The nature of the mechanism means that the initial acceleration of the cart is slower than a pure sail-driven system, because the way the propeller spins adds resistance to the wheels via the gearing. But ignoring losses to friction, if the wind is constant, it won’t stop it from accelerating—it’ll just slow the rate of acceleration.
At this point, the pure wind force has fallen to 0, because the cart isn’t moving relative to the wind. But the propellor is still producing a force dependent on G, A, and r.
So for the right values of G, A, and r, you’ll still be accelerating.
This seems to equivocate between wind/propellor force and net force.
What do you mean by that term? The post does say this:
(Emphasis added.)
Okay, it does there, but I refer to this part:
This seems to equivocate between wind/propellor force and net force.