Double taper spar

[Simon Chaddock]

After a bit of trial end error I have elected to go for a single servo link to both elevators and rely on 'flexible' horns to account for the changes in geometry over the full travel.

Maybe not mechanically perfect but it is simple, light and it works!

Now for the fuselage 'pod' and motor.

[riverlandgirl.]

The best engineering solution is the one that does the job properly, in the cheapest and simplest manner..... looks perfectly logical to me.

[Simon Chaddock]

In this pusher design the wing pylon is in effect a short piece of wing so it is built like one with a balsa/Depron/balsa box spar.

Clad in 3mm Depron with the beginnings of the forward fuselage.

.

At this stage the forward fuselage is well over lenght. It will be trimmed once the battery has been positioned to achieve a suitable CofG.

Edited By Simon Chaddock on 01/09/2012 23:34:13

[Simon Chaddock]

The wing positioned on the pylon.

The aileron servo wires have to be 'threaded' through the pylon before the wing can be finally glued in place.

I am beginning to think that tail moment might be rather small.

With the motor mounted on the wing trailing edge it should atlast be possible to establish the battery position and the nose length adjusted appropriately.

[Simon Chaddock]

The 1500kV Blue Wonder (although they are now all chrome) and fairing with a 7x6 prop.

The fuselage nose nearing completion.

At this stage it weighs 7.9oz (223g). It should weigh just under 12oz with a 1500mAh 3s.

Although the motor only takes 10A at full power the 20A ESC is completely buried so has a finned heat sink protruding into the slipstream.

Nearly there!

[Simon Chaddock]

Just about calm enough for the maiden but proved a real handful, it needed full down trim to achieve anyhting like contrlled flight!

CofG too far back at 30%? Possibly so a 10mm plug was added to the nose to allow the battery to be moved forward.

It also gave a bit more room for the deans connectors.

Although the CofG was now 26% it still needed full forward trim to fly much above the stall speed.

Rather than move the battery further forward I decided to reduce the wing incidence but it is permanently fixed.

The rather drastic solution was to remove a section ahead on the wing pylon spar and add a section aft to 'bend' the wing mounting reducing the wing incidence by a couple of degrees.

The result all glued up.

The joys of own desigh!.

[Simon Chaddock]

The final issue with this plane was with the ESC. I could not programme the brake on, so I was stuck with a fast windmilling prop that really took the edge of the glide performance.

The ESC was a cheap 'no name' job so had no instructions.

It went through a cycle of no less than 16 programming beeps but unlike many other brands the brake on was not set by the first beep, or the second! Soft start on three & motor direction reversed on 4. Then things got very untidy with I suspect motor timing. From then on the motor would not run properly.

The only 16 step ESC programme I found was for a Hobbyking range but motor reverse was not on 4 so it was not relevant.

Nothing for it but to replace the ESC with a Mystery 20A and I made sure the brake was "on".

At least now it performs properly and looks very elegant in the air even if the roll rate can only be described as "sluggish" . The 1500kV Blue Wonder driving a 7x3.5 only draws 10A at full power yet gives an almost vertical climb.

With a 1500Mah 3s it should have a 'still air' endurance approaching an hour.