Terry@rigdenage

Aerobat

Specifications

top view of Aerobat

Span: 38" AUW 11.25oz. Wing loading: 5.9oz Sq/ft.
Battery: 7.4V ETEC 1200HD LiPoly (2s1p)
Motor: GWS350c 6.6:1 gearbox. prop GWS10x8. ESC MGM 1210
Radio Muliplex 3/4 Rx, 2 off Hitec Hs55 servos on ailerons and elevator.
Typical duration: 30 Mins of mild aerobatics

Getting started

I wanted a small light and highly maneuvarable aeroplane that could get in out out of small spaces. It needed a good rate of climb and powerful controls. Scale like looks were not important and as I was flying off grass wheels would just trip it up on landing so they were left off. After looking at a few kits and designs in the magazines I fired up the CAD system and set about designing my own.

Its almost all balsa construction with the materials coming entirely from the scrap box (which doesn't seem any emptier). Covering is litespan which looks like tissue but is much more puncture resistant.

The one piece wing has no dihedral so that the leading edge and spars won't need a join saving wieght and complication. That set the span at about 38". I wanted a wing loading of less than 6oz/Sq ft so after estimating the all up wieght at about 11oz I went for a mean chord of 7.25" which gives and area of 275 Sq inches. The wing section is the Eppler 374 which is a bit unusual for an aerobatic aircraft but I wanted plenty of low speed lift for a steep climb out. The Spar is an I beam with 1/8th tapered top and bottom with a 1/16th cross grain web between them in the centre only. The ailerons are full span with the option of mixing in flaps later if required.

The fuzelage is just the minimum sized box to contain all the gear and hold the wing and tail the correct angle and distance apart. The structure behind the wing is open to save wieght. The tail is geodetic and built up from three laminations which resulted in a light but stiff structure.

In the Air

The full throttle the climb out from a hand launch is business like but you can't hang on the prop. I usually throttle down after a few seconds and cruise about. It will loop from level flight on partial throttle, rolls need speed or the second half wanders all over the place. Despite its semi symetrical wing section inverted flight is no problem and it will bunt quite nicely but you need to manage the airspeed with throttle. Stalls are no problem it just drops to the right a little I have tried to induce a snap roll but its far too well behaved to do that . Landings are easy, you just slow it down on the approach and chop the throttle at about knee high and flare out for a greaser.

Modifications

Rudder control added helps coordinate turns and now I can do stall turns

Brushless motor Eflight Park 370 Outrunner with castle creations Pheonix 10 turning an 8x4 prop. Dramatic increase in performance almost unlimited vertical performance and in almost total silence. Weight reduced to 302 g

Flapperons adeed with 4th servo and 8 Ch GWS reciever wieght back up to 320g. After many hours setting up the mixing on the HITEC Optic 6 transmitter I got about 30 degrees throw on the flap function. Early test flights in less than ideal conditions havent shown any change in performance or trim with the flaps down