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

AMX JET

AMX ARF kit

The size is bigger than freewing F35
They use the same power system EDF 64mm (92g) with thrust ~600g @28A/ 11.5V( on load 3s) ~ 320W. I doubt this 2040 /130L brushless can withstand such power, without a suitable heat sink. Thrust 1.6-1.9 g/ W
The spray and decal is perfect.
The control surface hinge is not perfect and the hinge tape tends to peel off easily.
The foam is strong in general. The connection between the fuselage and the main wing is relatively weak.
I modify the battery compartment, such that it can accomodate a 3s 2200mAh lipo.
The EDF needed to be taken off and check for loosen screw and imbalance of propeller.
The stock motor foam compartment has some glue spilled over and make it very difficult to remove the motor compartment.
I add 2 additional 2.5mm screw with washer to make sure no vibration can cause propeller striking the duct wall. I also fill the gap of the inrunner and the case with some balsa to reduce vibration.
I am still looking for a heat sink, such that the risk of duct case melt down is minimized.

This AMX (~600g) will fly fast but not that of Freewing F35, which weights only 400g.

AMX EDF housing is much strongly and does not deform easily as the Freewing EDF.

The EDF propeller hub is permantently fixed to the 2.3mm shaft and there is no worry like the GWS fan hub. However, there is no easy way to buy a replacement propeller fan.

Futher benchtesting,
At 24A 3s, the motor rated >300W and run for 2 mins continuously. The motor case temperature keeps at 55 deg cel.(ambient temp 22 deg cel) , thanks to the EDF stream of air. On stopping the motor, the motor becomes hot and rise up to 65 deg cel. I am quite satisfied with the temperature and not worried about it.

Finally, a thin layer of epoxy was added to reduce drag and scratch at the wing and bottom of fuselage.

今日初航, 好大飛, 基本上好細力一拋就上, 完全冇 Freewing F35 咁高難度起飛, 又冇反扭,
隻機顏色好 sharp, 飛到老遠都好易認, 唯上下反轉同色要 小心
Landing 收油 到 1/4 就 乖乖 下降 ,
尾 兩隻 elevator servo 我用了 mixing , 易D set

導風扇葉做模

pending for progress.. Need vaccum pump to get rid of the silicone bubbles...
Link

Freewing F35

This EDF plane is significant smaller in size from most EDF plane, GWS plane, Mirage 2000 .etc.

The stock included EDF 64 5 blades, in-runner brushless with a large heat sink.

No landing gear was designed for this tiny and I am tempted to build a steerable landing gear for her. The decal is superb in appearance.

2 servos for Delta setting of aileron and elevator.

RTF weight ~290g, without lipo. With all the landing gears and extra serovs, it weights 309g.

I put in a 2200mAH 3s lipo that weight 178g. Wing loading will be expected to be high. So landing should be done at relative higher speed.

The stock power system drew 28A@11.7V at full throttle, with thrust ~600g. EDF thrust to power ratio about 1.6g/W.

Thrust tube added- to reduce nose down turbulence due to low pressure zone above elevator , and to reduce exit nozzle 5 4mm. (stock 58mm resulted in high thrust but low terminal velocity)