Tangent

For some time now I have been looking for a more precise 3D type aerobatic aircraft. For those of you who know about electrics, finding a combination of power to weight ratio that will do this (especially 3D), is a very difficult task. To have a decent size aircraft to fly outside (not indoors) and to stand up to windy conditions requires many cells and larger super efficient motors with speed controllers to suit. My parameters at this stage seem to be a little too far ahead for me, but during this investigative period, I heard about a reasonably priced aerobatic / pattern model - The Tangent.

It did not take me long to have a look at one at a hobby shop and then take it home. The fuselage is fiberglass with Depron foam wings laminated around a polystyrene core. Simple clear instructions and enough photos make building a breeze. Included in the kit is a motor with gearbox combination. Instructions are designed around using a specific size NiMh battery pack, however I had recently discovered the latest Hecell 1100 NiMh which I have been using in my foam ME 163, so in the interests of cost saving and having things more modular, I reconfigured the aircraft to suit. A couple of nights work, and it was ready for first flights.

Performance was to say the least very ordinary, with the most awfully noisy gearbox. I persisted for a couple of flights and then decided to find a much more powerful and quieter motor/gearbox setup. Enquiries to club members got me info via the internet of the combination of Model Motors Mini Axi AC12/15/16 brushless motor combined with a GWS 2.8:1 gearbox swinging an 8 X 6 prop. Eventually all components were procured and with some Dremel work on the firewall, I eventually had the new combination fitted.

The motor has a rating of 3800rpm per volt, so with this power potential I made up a 6 and a 7 cell pack to compliment the existing 8 cell pack to do my testing. I marked the placing of each pack on the wing ensuring that I could easily change packs to their positions and remain with the correct C of G. The long and the short is that I am only flying with an 8 cell pack and drawing around 12 amps static. The other pack configurations would fly the aircraft easily but not at the performance I require.

The aircraft is hand launched with no wheels for landing. Not long ago I came in for a landing, however the propeller was absolutely vertical and as it came in the propeller caught on the ground and broke as well as bending the gearbox shaft, which is only 2mm diameter. I replaced the propeller and straightened the shaft and flew again. Unfortunately the same problem has cropped up again twice with the bent shaft and now I am looking for another more robust gearbox to rectify this problem.

Flying 6 to 7 minutes of flat out gives very good speed and torque performance with loops, rolls, climbs and most aerobatic maneuvers easily possible. (Limited only by my flying ability or inability).

Specifications.

• Total weight 525 grams (Including batteries)

• Battery pack 170 grams

• Motor alone 48 grams

• Servos 2 x JR 371 (Aileron and Elevator)

• Propeller 8 X 6 APC

• Electric Speed controller 18 Amp

This has been a worthwhile project with the airframe ability making me work much harder to become a better aerobatic pilot. Through all of this the aircraft has so far been very forgiving and easy to recover from any attitude. I am slowly changing the C of G further back to achieve the best possible for myself. There are a number of these types of aircraft at the club and I urge those with the resources to look at a different power setup to totally transform their airframe. Questions and comments readily accepted.

Good Luck and Good Flying

Colin Kahn

*** 10 January, 2010 10:26 PM +1000 ***

Last updated 10 January, 2010

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