Airplanes deploy revers thrusters when landing which are basically just shaped metal shields that move into place behind the engines to provide reverse thrust and slow the plane.

But adding a fan on a sailboat is seen as stupid and doesn’t work.

  • bitteroldcoot@piefed.socialEnglish
    15·
    3 days ago

    Size matters. Airplane engines create a huge trust. A simple house fan does almost nothing.

    A jet engine can blow a car end over end. A house fan just barely causes some paper to move.

    • gastroglizzy@piefed.socialEnglish
      44·
      3 days ago

      No fan of any size will ever push the sail on the boat it’s mounted to; that’s not how physics works.

      • remon@ani.social
        52·
        3 days ago

        You might want to check your physics because that’s pretty much exactly how a propeller works …

      • CarbonIceDragon@pawb.social
        1·
        3 days ago

        It can be, as long as the sail is set up in such a way that incoming air is deflected backwards to some degree rather than at a right angle to the fan (such as with a curved sail). Consider a still boat in still air (thus with no net acceleration in any direction to start). You push some air forwards towards the sail, then the sail deflects that stream of air outwards and slightly backwards. This means the combined fan-sail system (the ship taken as a whole) is taking in initially still air, and that air ends up with a net momentum backwards, so there must be push forwards. This is very inefficient compared to doing away with the sail and pointing the fan the other way, so theres no reason to do it in practice, but it doesn’t violate conservation of momentum or anything because the ship isn’t a closed system.