How to Aliexpress foam glider conversion to 3 channel radio-controlled plane. RC. DIY


we have purchased a launch glider made
with foam in Aliexpress these gliders have a wingspan of 48 centimeters and a
fuselage length of 46 centimeters they can be found for a price of 3 euros the
weight of the plane is 52 grams if we remove the cabin the weight is 35 grams
we prepared a first version of the plane with a brushed motor of 85 by 20
millimeters in a propeller of 55 millimeters this motor have a thrust of
23 grams using a three point seven volt battery we use a fly sky receiver in an
ESC for DC motors with a maximum amperage of 10 amps we place the motor
in pusher configuration that is placed behind the wing and pushing forward we
tilt the motor shaft so that the thrust line passes through the center of
gravity of the aircraft which is usually located in the first quarter of the wing
thus we avoid that the airplane has an accused tendency to pitch down we
prepare a support for the motor using a piece of extruded polystyrene the plane
as it is has a natural tendency to yaw to the right to correct this effect we
placed a small rudder made with extruded polystyrene taken from a food tray we
apply to the rudder a fixed angle of a few degrees to the left
this corrects the adverse yaw of the plane finally we apply a dihedral angle
by tensing the wings with a thread the dihedral angle improves the lateral
stability of the aircraft and correct the tendency of the aircraft to go into
a spin the final weight of the aircraft is 70 1.5 grams then the thrust to
weight ratio is 0.32 the wing load is 1.8 kilograms per square metre the cubic
wing load is 9.0 next we see some images of the flight of the plane in the next step we add a 3.7 gram
weight servo to control the yaw of the plane so we changed the three point
seven volt battery for a seven point four volt 500 milliamp hour battery
which weighs 30 grams we prepare a twin-engine plane that supports the
weight provided by the new battery we use a pair of identical motors of type
and 30 with propellers of 75 millimeters these motors connected in parallel to
the 7.4 volt battery provides a maximum thrust of about 40 grams the rudder has
been placed in a lower height so that the very center of its surface is
located almost at the same height as the aircraft’s center of gravity this will
cause the plane to rotate in a horizontal plane when the rudder is
apply if the barycenter were very high the plane would turn in an inclined
plane affecting its stability to improve the aerodynamics of the airplane we
cover the battery with the cabin the cabin has been previously hollowed out
to reduce its weight in addition we place the receiver plus the esc in a
hollow of the fuselage all cables are carefully attached to the fuselage so
that they do not disturb the air flow the final weight of the aircraft is one
hundred and fourteen point five grams then thrust to weight ratio is 0.35 the
wing load is now 2.9 kilograms per square meter the cubic wing load is now
fourteen point six now we see some images of the flight of the plane we have bought a different model of
glider it is a more optimized model in terms of weight and dimensions this
model without the cabin weighs 29 grams compared to 35 grams that weighs the
previous model without the cabin the wings of this model are polyhedral which
is very good to give the necessary dihedral angle this is done by tensing
the wings with a thread we have modified the design to mount a three-channel
airplane adding a channel to handle the elevator therefore we will have a better
control over the altitude of the plane since the new servo and rudder add extra
weight to the plane we have changed the battery to a lighter one of 350 miliamp
hour and 21 grams of weight taking advantage of the oversized vertical
stabilizer we have included the rudder inside it we have detected that the
adverse yaw of the previous models was due to the lateral decentering of the
tail in addition the tail buckles exaggeratedly when the rudders are
applied therefore we have added threads to anchor and center the tail in order
to avoid these problems we have also reduced the thickness of the vertical
stabilizer with a cutter so that the transition with the rudder is smooth
built the plane with all the necessary elements we have a final weight of 105
grams and a thrust to weight ratio of 0.38 flight autonomy is about three
minutes as we see in the video there is an improvement in lateral stability
thanks to the polyhedral wings in the next step we go back to the pusher motor
configuration the pusher motors usually pose a problem as they produce the yavi
aircraft due to the effect of the slipstream on the vertical stabilizer
this is usually avoided by placing a twin tail another way is to tilt the
motor down and ensure that the slipstream affects the vertical
stabilizer as little as possible since we are using a plane with classic empenage we have tilted down the motor the tilt of the motor also produces another
typical problem on the one hand if we place the motor horizontal and raised
with respect to the center of gravity for having room to the propeller we have
a Down pitching moment that we have to counteract with the elevator positioning
the elevator out of the zero angle will increase the drag force reducing the
lift to drag ratio of the aircraft the solution that is usually used is to tilt
the motors so that the thrust line go through the center of gravity creating a
null pitching moment however this solution has a drawback as there is a
vertical component of the thrust force that opposes the lift force the options
with respect to the inclination of the motor are to to leave it horizontal and
lose lift to drag ratio because of a greater force of drag
or to tilt it and lose lift-to-drag ratio because of a lower lift force as
we have already mentioned we have decided to tilt the motor to avoid the
yaw do to the effect of the slipstream on the vertical stabilizer the chosen
inclination is 22.5 degrees we are using an N60 motor with a three-blade
propeller with three inches in diameter this set produces a maximum thrust of 70
grams however since we have tilted the engine by 22 degrees the maximum thrust
available is only 65 grams this issue is another of the disadvantages of tilting
the motor because we lose thrust the body of the plane has been reinforced
with wooden sticks EPP foam resists compression well but not traction it
tends to break not when it hits but when it bounces and decompresses the violent
decompression of the foam after the impacts is avoided with the chopsticks
in the following tests we noticed that the airplane does not have enough power
to fly losing altitude constantly we have changed the angle of inclination of
the motor decreasing it to 15 degrees this is done not to obtain a greater
thrust but to lower the vertical force downward exerted by the motor several
modifications are performed on the plane the motor is better anchored to the foam
body to avoid the loss of energy due to vibrations the propeller is centered as
best as possible to also avoid such vibrations the rudder surface has also
been decreased so that the yaw is softer when turning again we have changed the
500 milliamp hour battery to a lighter one of 350 miliamp hour and 21 grams of
weight the weight of the plane is now 105 grams
leaving the thrust-to-weight ratio at 0.62 the final images of the plane are
shown

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