Eflite Haw - Test flight with Flap modification

The flap is added to slow down the plane on descend.

Smart looking nose strut.

The A4 Sky Hawk is much faster and needs extra attention to fly.

DX7 Switching 3.3V power supply

DIY a 3.3V switching power supply from a 12V to 5V USB car adapter. My DX7 can now run 40% more air time.

Eflite Hawk Flap Modification

Changsun nose strut with "shock absorbing" spring.

This Hawk flies so nice but needs lots of attention when landing. The relative high speed on landing also makes her bouncing. How nice to add flap to slow her down and avoid stall. Simply adding reflex does not make a good solution for perfect landing.

The flap modification is pretty straight forward by cutting along the aileron to the wing root. A servo can be easily attached to the fuselage and a link control.

OK Model A4 SkyHawk Modification

The fastest model of this class with small wing area and high wingloading.

The relatively easy to stall on banking turn is partly explained by the high pressure at wing bottom is stolen into the cheating hole under the fuselage. Therefore, transparent sheet was added to act as guard to prevent high pressure air sucked into the EDF.

Test flight confirmed no easy stall on high bank angle turn, which happens easily on high bank angle turn from downwind to headwind direction.

She is now back to service and flying experience gives more fun than worry.

Eflite Bae Hawk

Very nice finish and scale The intke is small and the profile helps to reduce drag.

Stock motor runs at 60A @14.2V ~840W.

The fixed landing gear produce much drag. Will be modified to electronic retract soon, after I can handle the landing behaviour of this bird.

Will add flap to make landing more easy. She bounces too much with the stock landing gear.

Maiden flight. No trim in and 70% throttle only. She really needs flap to slow her down.

3 Version of Towerpro Metal Gear 995

Left - old version with overshoot
Right - newer version.
photo from blood keith blog

SAPAC L39 70mm EDF

L39 is a very stable, yet agile aircraft. Their are ample space to install lots of stuff, including battery, lighting, retracts, etc. The L39 has the same wingspan as my 90mm F18.

The wing is detachable and needs close attention. The wing is only secured by a single 2.5mm screw. My friend's L39 has its wing completed detached from the fuselage during hard landing. I strengthen it with 2 additional 3mm screw mounted on the side .

Viper vs A4

Both have similar power and powered by 3300mAh 4s @70A.
A4 is smaller and it accelerates faster.
Viper has flaps that makes it much easier to land at lower speed.

F18 90mm EDF midair collision with 1.5m glider

Midair collision with another glider , results in the nose being sliced. The glider crashed but my F18 land safetly. That is a clean cut and she is fixed right away.

Lucky maiden for my A4 Skyhawk

Harvesting the 3mm EDF fan adapter from old J-power EDF

The stock motor rated at 250W and has to be replaced by current powerful >520W BL. I have to "harvest" the pressed fit adapter from the old motor. This is a very difficult procedure without the right tool. I use 2 piece of 5mm shaft (from Trex 450) and a bearing remover to press against a 3mm steel screw inside the 4mm hole on the adapter.

Happy Easter- unlimited flying everyday

2 incidents result in emergency landing.

This is the second time my rafale suddenly cut out power. Last time results in belly landing without damage. Not having investigate the cause, she was put on air again. While doing a low level inverted flight, the cut in happens again. Luckily, she can be recovered from an inverted roll at 3 feet height and land safely.
The root cause is the Hoffman Magnetic ends its life, despite she was kept at 70A @4s. Luckily my cheap 120A ESC does not burnt and the on board BEC does not lock out.

My F35 somehow sqeak midair after a "pop".

Opening the housing and reveal a 3mm screw was somehow suck into the EDF ?? Where does it come from, after 2 mins flight??

OK Model Type2 70mm EDF

The housing is FG reinforced and is very tought. The design is great to allow more cool air to contact with the inrunner case.

The Type 2 fan is not well balance at first glance. However, I was wrong and find that the vibration is even more significant after static balancing.
I end up leave the stock fan intact and it runs smooth and vibration free.

The Tamazo inrunner is very good quality and the copper wire is wound round stator (Unlike cheap inrunner). The magnet is very strong as well. Unfortunately the case is pinned and is almost impossible to disassemble to take a good look inside.

Don't say "One more flight"

The Hobbywing 40A ESC has a switching BEC board over the FET circuit. The 2 circuit board is soldered together, so increase the difficulty to repair components between.

Capacitor burst on crash. This is easy to be overlooked if the heat shrink is not cut open for investigation after a crash.


The specification of 40A is damn correct. I abuse it at 50A and the metal heat sink melt the heat shrink and shut down the BEC. The FET itself shutdown and protect from overcurrent.

A 50 cent repair.

ChangeSun Electronic Retract Crash resistance

Nose dive crash results in complete destruction of the fuselage. This electronic retract proved to have high crash resistance. Only the servo wire is torn. Look inside the large brushed motor and the metal gears.

Solder the wires and the electronic retract back into services. Note that the worm gear has bearing that gurantee smooth operation. The control board has silicon coating that protect the circuit from water and erosions.