In this clip we can see a model of a car-boat with a sail.
(Explicit links. Whole version: https://www.youtube.com/watch?v=zp1KzGQdouI. Parts: https://www.youtube.com/watch?v=jhem8Z9ujPE, https://www.youtube.com/watch?v=7g1Gz-62dHQ)
Facts are (for the first video):
- sail is flat (thus both sides are equally long)
- sail is at 35º respect motion line
- wind comes from ahead: the model sails close-hauled
- the wind impacts only on the winward side of the sail
- leeward side has 0 wind (telltales are down)
- the car moves forward
My hypothesis is that the effect propelling the car is only "air deflection on windward side".
Because there is no wind on leeward, no net effect occurs on that side (Bernouilli, differences of pressure, difference or airflow speed, whatever).
Although, of course, "leeward side" effects occur in real situations and they do contribute to planes lift / boat propulsion, their contribution is not necessary for motion/lift as the video shows.
Am I correct?
Does anybody know of any video demonstrating wing lift / sail propulsion in realistic models (not just lightweight papers) exclusively due to effects occurring on the leeward side?