|Construction / tuning
This is now the 3rd conversion of a Fox that I made. The goal was to
create a mini Hotliner / Pylon Racer - so the plane needed to be enforced
to withstand the G-forces.
1) Mark balance point
Assemble the plane - throw it and observe if it flies with the lowest
sinking rate possible. Add weight as need be (front or back). Once it flies
well - mark the balance point on the underside of the main wings
2) Carve out the cockpit
See on the picture on the side.
3) Fixing of the motor
In my case I used an 10 mm dia aluminium rod that I sharpened at one
end. Bz resting the fuselage on its belly I started to drill with my alu rod
the whole for the motor - parallel to the work surface! Like this I achieve
the neede slight down angle of the motor and also a slight right angle!
Once the whole came through to the carved out cockpit I could insert the
motor (dia 12 mm) - that was a very tight but perfect fit! No glue for further
fixing needed! GREAT!
4) Ailerons & wings
Cut out the ailerons from both wing sides (in my case they measure 2cm
x 14 cm)
Cut (or sand) the aileron rudders at a 45 degree angle (towards to wing)
to allow free movement.
Attach the aileron rudders with tape to the wings
Carve out a trench for the reinforcement CFK or GFK rod (I used a
soldering pen). Insert the rod and glue it with Cyan glue.
As I decided to use two servos on the ailerons to help trimming I
positioned the servos on the underside of the wings, marked the
position and cut on three sides through the wing. Then I flapped it open
and cut with a very sharp knife all away except approx 1 mm of foam. That
piece I glued back in place. Like this I got a very neat surface and a
perfect nest for the servos on the underside!
Glue in the servos (with a drop of hot glue in my case).
Next burn a trench with the soldering pen (approx. 1 mm deep) from wing
tip to wing tip. Insert the correctly sized CFK or GFK rod and glue it in
place with cyan glue.
Now you are ready to insert the wing into the fuselage and glue the wing
in place (before measure if the distance from wing tip to top of the rudder
fin is the same on both sides).
5) Receiver & battery bay
First I cut out the battery bay under the wing - but it turned out to be at the
end the place for the receiver as otherwise I could not achieve the proper
balance point of the plane!
Measure the space needed and cut out the foam accordingly.
Use the alu rod to carve a connection between this receiver compartment
and the cockpit!
In order to be able to get out from the tight space the battery (or later the
receiver) I drilled a hole from the other side of the fuselage so that I could
push through (out) the receiver. (On the picture the original battery is
Enforce first the elevator wing with a CFK rod. In my case I glued it on the
end of the elevator wing! This keeps it stable and makes a perfect hinge
point for the elevator rudder.
As a rudder I did not cut out part of the elevator wing, but used a piece of
balsa that was sanded into shape. the result was an extended elevator
wing and additional weight in the tail (and that is why I had to exchange
the planned spaces for the battery and receiver). In addition the tape I
used was far too big!
Next I cut out under the elevator wing a space for the servo and cut with
the balsa knife a slit from the servo until the cockpit for the extension
cable. I used a regular servo extension cable and where the connector
lied I had to carve out a bit more foam.
Now I inserted the cables carefully with the help of a screw driver!
After a servo test I closed the slit (where the cables were resting) with
cyan glue. Actually I also inserted a 1 mm CFK rod to strengthen the
The cable ended in the cockpit - ready to be connected with the receiver.
At the end glue the elevator wing in place - carefully measuring the
distance from elevator tip to wing tip on both sides!
7) Final assembley and steps
Now it was time to balance the plane again... and that is when I found out
that the weight of the additional balsa wood as elevator and the tape
made the plane be tail heavy. So I had to exchange the original position
of receiver and battery. But, fortunately, that was not a problem.
Then I fixed the rudder horns (cut from old servo horn) with glue on each
rudder and connected them with the servos. Due to the short distance
between servo and rudder I could use 0,8 mm steel rods directly.
The hood over the cockpit was secured with two small magnets.
Finally the prop was fixed and the entire RC programming started glued
in the hood and a screw in the fuselage as an anchor.
Having had experience with the Fox before I immediately programmed a
50 % expo to avoid too nervous flying at the beginning.
Now it was time to take a first flight....
Duing a wonderful clear November moring in 2010 I took this little plane
to its first spin.
The first try ended in the ground - in-runner was pushed into the cockpit
and the prop holder was slightly bend. But.... I did not wanted to give up
(a big mistake) and continued again ... a bit further the battery back, the
elevator a couple of clicks up.. and off again... yeah, I had some more
vibrations, but what shall...
The fox was flying...
After 1 minute the plane got slower and slower... so I emergency
landed... smoke came from the motor which was so hot I could not touch
it. It melted the foam it was stuck in and had spun in the fuselage...
The motor was terminally damaged!
The motor was replaced with a 15 g AEO outrunner with 50 W and a 7" x
4 "prop - and .... now the plane flies again. But not anymore a hotliner...
but still fast enough.
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