Tuesday 25 November 2014

Ultra light slope soarer

The design for this lightweight aerobatic slope soarer was inspired by DLGs or discus launch gliders.
It will work in anything over 5kn on a decent slope and in 10kn it will work on any slope.

The rudder and elevator are operated by a pull line acting against a torsion spring.

This unique system means the servos can be forward in the fuselage and there are no pushrods going to the tail.

The trick is to make a torsion spring strong enough to operate the control surface against the airflow

but not so strong as to overpower the servo.

The 0.4mm SS wire provided as pushrods for the Versus DLG turns out to be perfect.

Wingspan - 1.5m (65") Armin wing
Length - 104cmm (38")
Flying weight (500mAh LiPo) - 410g
TGY 9018MG servos x 2 (elevator and rudder)
HXT900 servos x 2 (ailerons)


6mm depron
43 micron laminating film
60 micron clear packing tape
2 x Skyshark P4X spars (7.6mm x 820mm)
- Wing spar 820mm
- Tail boom 700mm
150lb Kevlar kite line (pull line)
0.4mm SS wire (torsion springs)
Soft packing foam (nose cone)
4mm CF rod (wing tie down bars)

Overview and build video

Aerobatics in 10kn

Testing with dihedral and no ailerons

New Stuff iron-on film - EZload laminate - GBC Australia

UPDATE March 2015: On really hot days the rudder and elevator servos have moved out of position as the glue softened. I have added more foam packing and glue to fix them securely. The trailing edge of the wing has also popped open twice. I removed the ailerons, re-glued then taped the join, then reattached the ailerons. In the original build, by cutting out the ailerons from the wing, I removed too much of the glue holding that join. 

Wednesday 12 November 2014

1.65m (65") Twin Boom pusher

This twin boom pusher is similar to the 1.3m Depron Spectre, however it has a straight 1.65m (65") x 190mm depron Armin wing and twin rudders.

1.3m Depron Spectre and 1.65m Twin Boom pusher

Initially it was designed it as a 1.8m light-wind slope soarer but didn't perform as well as I wanted. The longer tail booms and larger wing span made it too flexy and delicate. I was also comparing the performance to a motorless Phoenix 2000, which is a sensational sloper.
Shortened tail booms and wingspan stiffened up the airframe nicely and the addition of a motor fuselage turned it into an excellent FPV cruiser and medium wind FPV sloper. It tracks well in a straight line and has a decent glide angle but is quite agile like the Spectre.

Instead of using packing tape to cover the depron I used document laminating film, often referred to as New Stuff in the RC world. It is ironed on with a warm iron before bending the airfoil and fuselage, and works very well. It's tougher and easier to apply than packing tape.

See the depron wing build and Spectre overview videos for the basics, and the Spectre post on this blog.

Additional strengthening ...

6x1mm CF strip glued along the front of the elevator.

Heat bent UPVC brackets for the rudder to elevator joins.

I used twin rudder servos rather than one servo and a long vulnerable connecting pushrod between the rudders. Full length wing spar made from 2 Skyshark P4X spars joined with an internal CF rod joiner and epoxy. 

Wingspan - 1.65m (68")
Chord - 190mm (7.5")
Length - 100cmm (36")
Airframe weight - 840g
Flying weight (2200mAh LiPo) - 1040g
Motor - Turnigy 2836 1100kV (260W)
ESC 30A Plush
Prop - 10 x 6"
Twin rudders
TGY 9018MG servos x 2 (ailerons)
HXT900 servos x 3 (elevator and rudders)

I can email the Sketchup file if required

Initial slope soaring tests