float plane down thrust
03-11-2016, 08:32 AM
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float plane down thrust
just wondering,.....on a high wing float plane, should the down thrust be reduced or eliminated in interest of not driving the front of the floats into the water during takeoff ?.
03-11-2016, 08:59 AM
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Seems to me that most float planes have the nose of the floats a little below the center of level flight. I think this it to aid in breaking the suction of the water on the floats by increasing the angle of incident.
03-11-2016, 05:44 PM
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yes, nose of floats a bit low, to increase angle of attack. the idea of placing step just behind the cg is for the same reason, as speed increases lift rotates the plane and lifts the front half of the floats increasing angle of attack. the floats act like a "stepped hydro" in this attitude, giving two small spots of contact with little friction and will break free of surface tension easier.
float nose low is different dynamically than down thrust. nose low produces an upward line of thrust which is helpful in getting the plane off the water. down thrust actually counter acts the float nose low incidence or angle of attack, effectively promoting the plane to stay on the water surface.,....hence the question.
look at a sea plane or flying boat and notice the angle of thrust their engines are set at. the greater the area of surface contact, the greater that angle of thrust must be, to pull the hull out of the water before enough lift is generated to fly the plane. the reason is to minimize take off run.
float nose low is different dynamically than down thrust. nose low produces an upward line of thrust which is helpful in getting the plane off the water. down thrust actually counter acts the float nose low incidence or angle of attack, effectively promoting the plane to stay on the water surface.,....hence the question.
look at a sea plane or flying boat and notice the angle of thrust their engines are set at. the greater the area of surface contact, the greater that angle of thrust must be, to pull the hull out of the water before enough lift is generated to fly the plane. the reason is to minimize take off run.
