Friday, 13 June 2014

Pusher with polyhedral

I have never tried a 3 channel rudder elevator throttle plane so thought I'd give it a go using the orange slim wing and pusher fuselage.

RET planes need some wing dihedral to enable turns due to the lack of ailerons.

I fixed the ailerons in place and removed the servos. This simplifies the plane greatly, the wing is just a wing, no servos or wires, apart from rudder and elevator.

The CF spar was removed and a bent 200mm x 10mm diam ali tube inserted to set the dihedral. The wing extensions were hot glued in place at the desired polyhedral angle. The wing seems to be strong enough without a CF spar.

I increased the rudder area, but after the maiden reduced the throws for smoother control.

The 1500mm x 200mm wing and flying weight of 630g gives a wing loading of about 21 g/sq dm (7oz/sq ft) which is great for gliding and slow flying.

This plane is a delight to fly, so slow and steady. If I had started with something like this the learning process would have been much quicker. I can trim it to fly hands off in big lazy circles and it takes care of itself.



Wingspan - 1.5m (59")
Chord - 200mm (8")
Elevator servo - TGY 900 9g
Rudder servo - TGY 500 5g (stronger servo might be safer)
Motor - Turnigy 2822/14 1450kV
Prop - 7 x 4.5"
Airframe weight - 520g
Flying weight - 630g with 1300mAh LiPo (gives 20 min slow flying)

Sketchup Plans










Friday, 6 June 2014

Albatross 2m sloper

Before the Red Sloper came this 2m wingspan sloper. It actually started life as a motor glider but a dodgy ESC connector stopped that project from being fully realised. I'll revisit it soon.

I call this one the Albatross for obvious reasons.

The orange plane is the pusher trainer with a 1.5m polyhedral no-aileron wing adapted from the slim wing. I'll post about that one when we get a nice calm day to do a proper maiden.

The depron I use comes in 1000mm x 700mm sheets so I can make the 2m wing in 2 halves.

I used 3 Skyshark spars all up, 2 joined with a 10mm x 150mm ali tube for the main spar and another spanning the join closer to the leading edge. The spar layout is visible in this shot of the wing on an earlier version of the fuselage.

The wing has full span ailerons operated by TGY 9018MG metal gear micro servos. Total chord is 200mm including the 35mm ailerons. That gives a 10:1 aspect ratio.

I suspect 40 to 45mm ailerons would have been better to give a faster roll rate for some aerobatics but they are fine for smooth cruising.

Airfoil thickness is 23mm, formed by using a 3mm strip of depron over the main spar, giving an 11.5% airfoil.

The tail is just a little scaled up from the Red Sloper but basically the same shape.

Horizonal stab is 460mm wide x 90mm deep tapered to 70mm at the ends plus a 50mm elevator.

Vertical stab is 220mm high x 130mm at the base tapered to 60mm at the top plus a 50mm rudder.

Elevator servo, hidden inside the fuselage, is a TGY 9018MG and rudder servo is HXT 900.

Fuselage is a 1000mm long x 70mm square tube tapered towards both ends for looks, weight saving and aerodynamics.

Weight is 650g without battery and balance weights and 830g flying weight.








The big wing makes for an excellent light wind slope soarer which also works well in strong winds. It's smooth and languid in the air, not so aerobatic, but a delight to cruise along the ridge.


UPDATE: I made the nose removable so I could swap to a motor pod. Just have to pull off the tape around the join and re-tape the motor pod on. The motor glider version is 730g without battery and 925g flying weight.

It took some decalage adjustment to smooth out the tendency to loop up under power. I needed to tilt the wing forward by sticking about 8mm of packing under the rear mounting area. Then it tracked level and glided much better.