FX707S Albatross

[quorneng]

I recently came across this foam RTF hand launch glider.

Just £20 delivered in the UK and at 1.2m span a bit bigger than a LIDL. Seemed an obvious candidate for a power conversion.
It proved to be very nicely moulded in EPO with a ready to fly weight of 280g. However with two big ball bearings in the nose for ballast removing them would save 83g for a start! Carbon tube reinforcement is provided in the box for both the wing and rear fuselage.
As designed the wing can be split into two for transport and the tail plane and fin are removable. All this requires quite a few bolts and a number of plastic fittings. I was happy to have a 'one piece' removable wing along with fixed tail feathers so most of the fittings and bolts could be dispensed with to save a few grams.
Although nicely moulded all the trailing edges were pretty thick at 3mm.

So, as I had done on my LIDL conversion, I added trailing edge 'extension' to give a fine 1mm edge.

Rather than Depron as I had used before the extensions were printed in LW-PLA. A touch heavier but giving rather better 'ding' resistance.
The moulded wing had modest poly dihedral so as I intended this conversion to be more of a glider than a sports plane I put the ailerons on just the outboard sections of the wing.

Although small by normal RC standards the extension does increase the area by 30%.
A micro 3.7g servo just fitted within the wing section. Fortuitously a slot was moulded all the way to the wing root to hold the servo wire.

With all the other 'moulded in' features (flaps and wing mounted motors are indicated) carefully filled with Depron inserts the completed wing surface starts to match the quality of the original moulded surface.
The weight saved by adopting a one piece wing largely countered the weight of the aileron servos so the converted wing only adds 12g.
Next is the fuselage. This is where the majority of the weight saving is necessary to counter the weight of the battery and motor.
To be continued.

 

[quorneng]

The fuselage involved quite a bit of 'excavation' both to provide sufficient internal space and to save a few more grams.
First some modest foam removal under the wing to provide a flat area for the receiver. Originally there were moulding for the elevator and rudder servos. For the conversion there would be no rudder and the elevator servo would be mounted in the side of the fuselage with long external pull/pull lines to the elevator.

The existing fittings for the the two front and single rear bolts are retained.
A much greater excavation was needed for the cockpit.

As I was going to use a relatively small motor I had to have room to move the battery to achieve a suitable CoG.
For good measure te cockpit canopy was excavated to provide "headroom" for the intended 850 mAh 3s battery.

Note the PLA filament locating pins glued in. One each side and one at the front with a small magnet to hold the rear down
I chose to use a LE2204 1800 kV motor.

23g and just as important on offer from Ali Express!
Next to cut the nose off at a position that gave a sufficient fuselage area for the motor mounting lugs.

One advantage of such a small motor is it only needed 1.3" of the nose to be cut off.
Next the more complex bit to deign and print a motor bulkhead and a cowling to encompass it all.
To be continued.

 

[quorneng]

The printed motor mount is made up of two parts.
The actual motor mounting plate to which the motor is bolted and a nut retaining plate which is glued on one the nuts are in place.

A cut out is included for the motor wires which matches a similar hole in the nose foam leading into the cockpit..
The motor and mount glued onto the nose.

A streamlined printed cowling covers the motor which includes a top air inlet and twin lower outlets.

It may seem a bit odd to rely on glue to hold the motor onto the foam but in a crash it will likely break away with little or no damage to the EPO foam or the motor for that matter..
The 10A ESC is mounted outside wall of the cockpit for cooling as my initial runs showed it got quite warm.

All white is not a good colour for a relatively small RC glider so all the control surfaces are painted a fairly dark purple for contract as well as the nose cowling merging to a tapering stripe on the fuselage underside.

With a 850 mAh 3s it weighs 298g. This is only 18g heavier than as a chuck glider out of the box.
To my surprise it flies really quite well and with its folding prop it behaves like a proper glider power off.
Its maiden flight. My apologies for the quality of the 'hat cam' video.