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aerojet powered glider filip400 simply the best

selection

My 1st electric aircraft.
Standard 540 size car/buggy motor.
Chosen for its looks and the fact that it is a "wooden" build it yourself thing.

construction

All 1 piece construction. Wings are flat bottomed section veneered white foam with balsa leading and trailing edges, and no spars. Not much strength there then.
The plan shows the aileron servo dropped through the wing centre.
I moved both servos (hitec HS101) just in front of the wing to keep the centre intact, and put some thin ply across the underside of the join inside the fuselage. No dihedral.
The power cells are supposed to drop in/out of a hatch at the bottom for access. I decided to sheet this over, for strength (it lands on this), and slide the cells in from behind.
Having fitted a ply bulkhead at the front of the wings for the cells to butt into under landing stresses, I was left with a rather long route for power from the cells to the motor, around the back of the wing and along the top.
Some heavy gauge single core mains cable reduces the losses, but added extra weight.
I added a fair bit of extra wood up the front too, as it just didn't seem strong enough.
Not keen on BEC speed controllers, I fitted a separate Rx pack (more weight).
I somehow managed to assemble/fit the the tail 0.25" off centre, so the tail ended up 0.5" shorter than it should be.
Fitting the speed controller immediately behind the motor meant putting the Rx in the canopy area to keep them separate (interference).
The long nose and forward mounted servos meant fitting the Rx pack well back. Initially I built the Rx pack inside the tail.

The aerojet with the canopy off.
Left to right - charge connector, 30A blade fuse/holder, chocolate block power connector, 700mAh Rx pack on wire frame, original futaba Rx (all on extra floor above aileron push rods), aileron and elevator servos (hitec HS101), switch, speed controller.

flight

Flew 1st time over at the Wyken nature reserve.
Fitted with the standard 540 motor and a 7x3 folding prop and 6cells/7.2V it was rather underpowered.
Even so, it flew quite smoothly and refreshed my flying reflexes.
After 2 successful flights, we decided on a 3rd. On launch it seemed to have even less power, and my attempts to keep the nose up ended in it landing on its tail, breaking it off just behind the wing.
Later analysis showed that the car radio fuse holder I had used was just not up to the job - they are only rated at 5A and the motor takes about 20A.
This had corroded the contacts and produced a high resistance, killing the power.
I stuck the tail back on, with yet more thin ply across the join. At the same time, I whipped the Rx pack out of the tail and fitted another at the back of the canopy area, on a wire frame above the fuse.
The fuse at this time was a soldered in blade (car type), removeable by chocolate block connector. Later I found suitable blade fuse holders.
In the quest for more power, I gradually fitted larger props, reasoning that an electric motor under heavier load will slow down and draw more current, hence more power.
The flaw in this idea is that there is a limit to how much back emf a motor can generate, determined by the field strength in the permanent magnets.
Eventually the voltage gets stopped by the resistance in the windings leading to heat. That motor went up in a cloud of evil smelling smoke, before the fuse blew.
I decided to try the other route to more power - more volts and high revs. I got a "hotter" buggy motor with fewer turns and a couple of 7cell 8.4V 2000mAh packs.
With a 7x4 prop this produces an impressive whine and a respectable draught, although nowhere near enough for a vertical climb.
The performance now is quite spritely on full power, and it shoots about the sky nicely on 1/2 throttle (see video).
It has to fly fast, because of the high wing loading, and the neutral stability of the no dihedral low wing means it needs constant attention.

A pretty model, although a jet it is not.

retirement

Crunched it a bit sometime 2003 in a heavy landing flying left to right. Broke the tail off again, and creased the nose.
Found the tamiya power connector a bit melted on 1 side, due to a poor connection and the heavy current draw.
I stuck the tail back on, but decided that it was not much fun with such a high wing loading.
Still intact, but in the roof.

statistics

more photos

Me with electric aerojet and powered glider at wolston in about 2002.
Note wheeled flying box containing a car battery for charging.