[caconym_]

I don't know if your explanation is simple or obvious either, except maybe in a very hand-wavey sense that may or may not correspond to the truth.

The sailboat thing isn't really an analogy—it's a direct comparison, and the operating principle is the same. There are a lot of resources explaining the phenomenon of "apparent wind" and how it's possible for a sailboat's downwind velocity component to exceed the environmental wind speed. If you understand vectors at the level of a college freshman, you can understand how that works; you don't have to be a sailor. From there, the "cylinder Earth" thought experiment provides the intuitive leap to the operating principle of this dead-downwind vehicle.

They do touch on the concept of a faster-than-the-wind VMG downwind, but they probably should have emphasized it more in the explanation.

[newnewpdro]

Introducing sailboats doesn't simplify explaining anything in my experience, they just pollute the mental model with more complexity.

There's value in the ground vehicle model for explaining to someone how sailboats can travel faster than the wind propelling them. But I don't think sailboats are a useful teaching aid in the opposite direction; explaining how the ground vehicle works.

So unless the goal is to teach specifically about sailing, I feel it's best to leave it out entirely. Except maybe at the end as a passing mention like "BTW, this is how sailboats manage to sail faster than the wind as well."

[caconym_]

I have to disagree, because a sailboat is a pure manifestation of the model that must be understood to understand how this vehicle works: a foil held at a fixed angle in a moving fluid, constrained to move only along a straight line at a fixed angle wrt. the motion of the fluid.

Understanding this vehicle requires heaping more complexity (the spiral motion) onto that same model, so in fact I think a sailboat is a great teaching aid here, as it's a clean waypoint on the journey to full understanding. Sailboats also exist, and have non-controversially demonstrated the surprising ability to sail with a downwind VMG higher than the environmental wind speed, which will help skeptics to engage with the problem.