Definitive Design Choice

Jean-Pierre showed the previous iterations to a group of pilot friends and they felt that the prop rotating around the boom was a good idea and that we should go back to it. So our latest design combines the high wing with the boom going through the prop hub. Spec is still 31 kilos dry.

Another version. The fairing construction is not fully decided. The wheel is a standard 305-mm bicycle rim with 375 mm outer diameter. It's very sturdy and if it breaks you can rebuild it with more spokes or thicker spokes. Conventional controls with a side mounted stick (on right hand) and rudder pedals. The transparent color is fabric, 57 g/m2 (1.7 oz per sq yd). The opaque color is 0.8 mm plywood. 

The previous version had a connection from the feet up to the motor, for this version we chose to remove it because the largest magnitude forces involved are transmitted by the two struts from the pilot's CG up to the wing; there is not really much added value to the super-rigid loop or triangle type arrangement.  

triangular frame

Jean-Pierre suggested that the front bar go down directly between the pilot's legs since the fairing will be rigid enough to support the pilot's feet with the rudder pedals. That way the frame is a triangle. I don't always use the computer; here I just drew it up in pencil. The structural members are boxes made of thin spruce (10x10 mm) with some carbon fiber reinforcement and internal foam stiffeners. The weight of the bare triangle, not counting all the attachments - engine mount, wheel mount, fairing mounts, wing mounts etc - should be 2.7 kilos;

New Design

For this version the weight is still 31 kilos, and the engine is the same 14hp. Cruise speed higher, about 125 km/h. Faired pilot makes radical improvement to efficiency. The skin is 0.8 mm plywood (wing) and 0.4 mm plywood (rear of fuselage, tail, and pilot fairing).  Plywood is glued to foam cores and local carbon reinforcement.

Better Fuselage, Exhaust

I've redesigned the fuselage somewhat to reduce weight, and added the exhaust. The "chair" part of the fuselage will be1mm plywood with foam core.

31 kilo airplane - new layout

With Jean-Pierre we're working on a new layout where the tail is a carbon tube. The motor we are using, the Raket 120, uses a poly-v belt reduction and with this folding prop that is sold as individual blades, we can make a hub so that the prop effectively rotates around the tail boom. I will be posting a more detailed sketch of the engine mount and how the tail boom goes through it.

SPECS

Radne Raket 120 engine, 14 hp

6 m wingspan, 0.7 m chord, 4.2 m2 wing area, NACA 4415, 3 deg dihedral

3 axis with full span flaperons 

Gross takeoff weight 120 kilos

Stall speed 65 km/h

Cruise 110 km/h

VNE 130 km/h

Weight breakdown:

Engine, prop and exhaust 11 kg

Fuselage with controls, tailplanes and undercarriage 10 kg

Wings with struts 10 kg

31 kilo airplane

Here are some preliminary sketches for a 31 kilogram (dry weight) aircraft
The specs are:
Radne Raket 120 engine, 14 hp
6 m wingspan, 0.7 m chord, 4.2 m2 wing area, NACA 4415, 3 deg dihedral
3 axis with full span flaperons 
Gross takeoff weight 120 kilos
Stall speed 65 km/h
Cruise 110 km/h
VNE 130 km/h

Weight breakdown:
Engine, prop and exhaust 11 kg
Fuselage with controls, tailplanes and undercarriage 10 kg
Wings with struts 10 kg

Construction is foam & composite with unidirectional carbon fiber at key locations.