J-power F-4 Phantom Mini EDF 幽靈式戰鬥機

Again, J-power make a superb EDF warplane. This F4N is even easier to installed then my AMX. Even the tai elevator is pre-installed. However, the factory left the front wheel steering installation for you.

I found the rear landing gear is designed too far back from the C.G. Therefore, I reversed the gear base mount to make it lies closer to the C.G. to make take off easier.

The tail horizontal fin is a bit thin/weak if one intended for a decent fast EDF. I will definitely strengthen the elevator if it can fly fast.

This is the first time I can see pin hinges are used in a small EDF . This reduce the load on the servo and is slop free.

There are 4 magnets for the canopy latch. I think that is too much and I relocate 2 magents to the rear ESC compartment latch.

Exit nozzle diameter = 3.7cm. Two exit nozzle area = 21.5 mm sq
Intake duct diameter = 64mm. Fan Sweep Area= 26.85 mm sq
Exit Area = Exactly 80% of FSA (Good factory design !)

Nemesis rebuilt

The last major crash resulted from using an empty A123 pack. I was so stupid to miss one uncharged A123 in my car. I commit double fault as my routine includes checking the pack voltage . My Nemesis took off as usual but at a longer take off distance. After the second loop, I felt it losing power. Thanks to the strong sidewind, it stalls on turning and hits the ground heavily. Luckily, the wings are intact and the motor compartment just sheared off from the fuselage.

Repair session 1
Major compartment is repaired by using 3mm wooden board. Since the original is badly damaged. Some measurement are estimated. This is the most im portant part as the landing gear, front firewall compartment and side board are all attached here.

Front and back pieces are joint together temporarily with CA and wooden tongue depressor. Precise measurement are made to ensure the same level of vertical and horizontal orientation.

J-power Blue Angle

1. Out of the box: Very attractive painting. Package is not in heavy duty foam packing.


2. Like most EDF motor set, the motor wires are a bit short. It is necessary to tidy up the 3 wires coming at the back of the EDF.


3. Since this is made of EPO material, which is too smooth to adhere, I sand away the paint at the contact area that need stronger bond.


4. The landing gear archoring is a new design. It can be detached and ready for hand launch in seconds, without using a philip screw.


5. The stock EDF comes with an outrunner (400DH size). Inside fuselage thrust test ~ 625g @ 30A x 11.8V. Power ~360W. Thrust to weight ratio > 1:1. I did some benchtest with 1500mAH and 2200mAh. My 1500mAH 20c cannot hold the voltage well at 30A, and quickly drop the voltage <10.5v>
6. Complain about the aluminium motor hub is slightly off center and this produce noticeable vibration. I routinely add some balsa/CA to the space between the motor and the motor housing to minimize vibration.
   


7. RTF weight : without lipo ~ 360g. The battery compartment has enough room to handle 3s lipo 1300- 2200mAh (needs to cut some EPO in the middle, takes a few seconds)


8. Servo extension cables are all included and makes assembly without much problem.


9. 2 Exit nozzle of size 3.6cm diameter . 64mm EDF, FSA ~27 cm sq, 90% FSA divided by 2 nozzle, and each nozzle is expected to have diameter of around 4 cm. I have to cut some plastic from the rim of the exit nozzle as some redundant plastic overhang and slightly obstructs the duct.
   


10. I like the hinge as the EPO molding itself made a very good slop free hinge. One need to warm up the hinge by flexing it a dozen of time.
11. Servos are pre-installed and there is no centering issue. J-power's series seem to adopt 2 servos Y-wired configuration to solve the mechanical difficulty in EDF
12. Assembly takes 2 hours to finish.

Maiden it. Excellent in striaght line level flight. Needs more travel in roll. Factory recommended CG is correct.
The front landing gear is 1 inch longer and the F18 tends to bounce back to air on landing. Watch end of my video as I cut it 1 inch shorter and solve the problem.

Aerodynamic calculator

Wing CG