Successful Maiden OK-Model L39 with Change Sun retract

OK Model fiberglass L39 and SAPAC foamy L39

Fiberglass OKmodel L39 and Jpower A4

OK Model stock setting is buggy launch, but I install X-flight ChangeSun servoless electronic retract and shock absorbing strut. My setting flying weight is 1540 g with 3300mAh lipo. Power ~ 900W@ 48A.

The servoless retract works perfectly and really done its job! No more hopping and bending gear wire!

Mistake to let it take off

My P51 has problem of smooth running at high throttle. Initially I thought it is the problem of my cheap ESC (though it has been no prolem in previous 10 flights). After changing to Hobbywing 40A ESC, the BL can run smooth. However, pre flight check with a clamp meter showed 50A (previously 35A). So stupid that I reassure myself that it is ok.
Eventually, power lost mid-flight after 1 min in the sky. Luckily I can still have control and the plane landed safely.
Air-crash investigation revealed the BL is burnt. My hobbywing ESC does not burnt despite the high current surge! Take a closer look revealed a piece of 2x2mm debris inside the bell, with scratch mark on the magnet, and melted copper wire on the stator.

Likely either the copper wire loosen and expose itself to the magnet causing local short circuit. Or some debris got between the stator and the magnet, and plucked the copper wire out.

Metal shock absorbing landing gear from X-flight

2 sets of spring is provided to adjust the load you want.

I add a piece of rubber to shield away dust and for addition shock dampening.

Just another tricopter

95% completed. Power by three 250W brushless with 10" c/cw propeller. The propellers have very poor balance and needs lot of hardwork to make it viration free.

KDS flymentor is used as the 3 axis stabalizer.

Hobbymate HB 3650

Appraise by some flymate for its power. This motor has relatively short stator. Magnet looks like neodym, but it isn't. Built is very similar to Z-power series.

Bearing size 11x5x11. 8 pole 12 slot outrunner. Weight 160g.

OK Model L39 fiberglass

The OK model L39 has a stock 70mm EDF , with thrust measured ~ 1kg at 48A x 4s (almost 700W) . Thrust to Watt ratio 1.4/W. Without lipo , my L39 with all the gears and lighting weight almost 1140g.

Pending for 555 timer to make them flash. Using PIC (program from rc-cam) for control of the flash is also anoter option.

X-flight electronic retract. Almost tailor made snap in for a 70mm EDF . The wing root is deep enough to install the electronic retract.

Hobbywing 40A

international rectifier

IRFH7932TRPBF

MOSFET, 30V, 25A

They are a total of 4 FET in each phase. Therefore the ESC is able to handle 50A below 70 deg cel.

Prodesign F18 90mm EDF

Realistic cockpit with instrument dashboard.

Prodesign fiberglass F18 with fixed landing gears. Very scale and nice design and built.

The intake is smooth and the decal is superb.

Will maiden her after upgrade with the ChangeSun electronic retract and shock absorbing strut.

75A 6s ESC with BEC

LM2596 - spec 40V to 5V, 3A switching BEC . Regret that the IR2101S pulse driver has max Vcc of 25V only, otherwise 7s can be used.

FDD 8896 FET x 6 , spec: 30V, 35A(max 95A each!) ; tota 35Ax3= 105A

Rebrand by many seller.

Starmax 90mm EDF

GI Joe : " Request permission to take off"

Stock landing gear length reduced by 2cm. No more problem with retracting gear.

Power ~ 1,100W at 6s 50A. Speed ~ 140kph only. With exit nozzle diameter reduced.

Plan to use 7s to gain more speed.

X-flight twin 70mm EDF Rafale

Very nice looking rafale with modified single 70mm EDF. Hoffman Magnetic at 4s x 70A ( limit of my lipo) ~ 1,000W. Certainly, at 1,400W it can fly even more ballistic!

My DIY is simple to make and cheap. What you need is

1) 3mm collars x 2

2) M3 screw and washer

3) A rectangular piece of fiber glass.

4) rubber band or propeller O-ring

The tension is set to ~2-2.5G . My rafale weights 1.4kg and the tension is set to ~ 3kg. The landing gear is all intact , even with hard landings.

L39 with front gear light

Installed a high power LED. The result is superb!

A DIY 3.7V regulator is used, with 700mA current drawn.

Will add red and green LED on th wings soon.

KDS flymentor 3D

The CCD unit.

3 axis gyro.

Will be installed in my new VTOL.

Solar panel lipo charger

The nice looking specification:
5.5V @ 500mA
Autocut overcharge/discharge of 2200mAh single cell lipo.

The unit can be charged also with a 5V source from a USB (some computer cannot deliver sufficient power)

Open the unit and found the stock lipo inside was crappy, and likely to be a used lipo . Testing and found the lipo only hold 10 % of the original capacity, and only hold voltage ~4.0V (should be 4.2V) with a lipo charger.

Reinstall with some better quality lipo and upgraded to 4400mAh.