lipca
13If a sailboat with open sails had a strong fan on the back blowing air into the sails, which way would it go?
Filed Under (Sailboat) by admin on 13-07-2009
Tagged Under : Rear End, Sailboat Sails
Ok, picture this:
A sailboat is on flat, calm water, with no wind. The sails are open. A fan is on the rear end of the sailboat blowing an unlimited amount of air into the sails.
Would the sailboat go forward, or reverse?
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Probably backwards - the fan would provide thrust along the axis of the ship in the reverse direction, some of that thrust would hit the sails, and might be deflected, providing some forward vector, but the fan would be the dominant source of force and would act to back the boat up. (look at an airboat in swamps in FL and Louisiana.
Im not quite sure what you mean by “open sails”, but my guess is that the boat goes nowhere, as the fan and the sails are attached to the same piece of wood; you’d have an area of high pressure trapped between the fan and the sail(s), but this would impart zero momentum to the craft.
forward. If they were in the back blowing towards the sails
sail –> {
______{______] See the { tinng is the sail and the bracket is the fan the fan blows and the boat goes forward.
Hmm the guy above me has a good point. If they are attached it might not go at all.
If the fan was right up against the sails, then it wouldn’t move. If the fan was far enough away, then the boat would probably move backward a little bit.
Let’s say you pour 1000 watts of power into the fan. 200 watts is lost as heat, so 800 watts of power is spent accelerating air forward, imparting an equal thrust to the boat rearward. The air mass carrying that energy heads for the sails. Perhaps a third of that is converted to forward thrust to the boat. The reverse thrust wins easily, and the boat goes backward.