ChangeSun 90mm motor fan unit

Motor fan unit using outrunner 1900kv. Running at 6s with amp drawn 70A, the thrust is over 2.6kg. Almost 1.6g/W in benchtesting. My F18 now make a speed record of 180 km/hr.

Quadtwirl gyrotor revived !

My old quadtwirl is revived after its maiden 2 years ago. The torsional weakness is now solve with a piece of 1cmx 1cm balsa running along the fuselage.

Motor now upgraded from 100W to 250W outrunner that runs at 3s/ 20A with a 11x4.7 propeller. THe elevator will be mixed as Delta to provide more roll control. If I were to strengten the rotor, I would insert CF rod + tapes need the rotor blade root.

SAPAC F16 with 70mm EDF

Now redo the power system with 70mm EDF at 700W. EDF unit from OK Model Tahmazo 3600kv inrunner. Speed now getting close to satisfaction. Needs to reduce the exit nozzle to get extra speed.

Bae Hawk shortened nose gear

Shortening the front nose gear makes her never bouncing on landing.

The wire needs some dremel to lock the control arm in position. Now she lands like sticking a magnet !

SAPAC 70mm EDF revive

Very agile and predictabel control F16. Recently upgraded from 400W EDF to 800W. The performance is excellent.

Lightex film is ironed onto the wing, to reduce drag. Lightex on foamy is suprisingly good in reducing drag.

With OK Model inrunner EDF, this F16 flies like composite model.

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.

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.

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

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.

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.

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.