(Alpha Jet) by AFF

19 Oct 07 - Elevator joiner replaced.

AFF Alpha-Jet AFF Alpha Jet AFF Alpha Jet AFF Alpha Jet AFF Alpha Jet AFF Alpha Jet

No of launches / Time 23 3 hours 13 mins  

<─ All flights included in these figures

Wingspan 35.4 " 0.90 m See left
Wing Area 287 in² 18.5 dm² See left
Flying Weight 1 lb. 13¼ oz 829 g 1 lb. 13½ oz 837 g
Wing Loading 14.7 oz / ft² 44.8 g/dm² 14.8 oz / ft² 45.2 g/dm²
Wing Cube Loading 10.4 - just over Aerobatic (Great for a fast jet) 10.5 - just over Aerobatic (Great for a fast jet)
Motor Mega ACn 16/15/3 HXT 2835 (380S) 3900kv Brushless
Ducted Fan Unit

WeMoTec 480 Mini-fan

See left
Batteries 2 x 3S1P Tornado 12C 2200mAh LiPo See left
Speed Controller Jeti JES 500 - 6 to 12 cells - 50A - BEC - Brake See left
Receiver Webra Nano S6 - 6 channel - PPM - 35MHz See left
Servos Elevator - Hitec HS-55 See left
Ailerons - Hitec HS-55 See left
Static motor parameters  3S2P Tornado 2200mAh LiPo gives 29436 RPM @ 10.31V drawing 24.2A, input power 250W = 137W/lb. 3S2P Tornado 2200mAh LiPo gives 31584 RPM @ 9.85V drawing 31.9A, input power 315W = 170 W/lb.
Flight performance Flies very well, and gives flights of well over 10 minutes.  Climbs can be at about 45° and virtually all non-rudder aerobatics can be completed. Flies very much as with the Mega ACn 16/15/3

19 Oct 07 - I replaced the elevator joiner with a piece of hard wood and also moved the control horn onto one of the elevator surfaces.  If the joiner were to fail again I should have 1/2 the elevator under control.

15 Sep 07 - Test flown today and flies as well as before.  I realised I had forgotten to put the rear duct back on, which should improve the performance.  About 3 minutes into the flight elevator control was lost and severe flutter of the elevator surfaces had occurred.  Fortunately the damage is slight and can easily be repaired.

14Sep 07 - Just fitted the a HXT 2835 3900 RPM/V motor which should give a little more speed and power.

27 Aug 07 - Last time I tried to fly the Alpha-Jet the motor wouldn't turn over properly.  I have just stripped the motor out and measured the windings, one is open circuit.  I will have to get a replacement motor.

21 Jan 06 - I have finally completed the re-motoring of this model.  It was a lot more complicated than I expected due to the increased weight of the motor.  This caused the CofG to move considerably rearwards.  As the battery pack was almost at the forward limit I could get the CofG to an acceptable position.  I tried a number of ideas and eventually decided that the only solution was to move the fan forward by one hole (19mm).  Having cut the new aperture for the fan and re-mounted it, I found that I could afford to reduce the battery pack weight by 100g and still have the required CofG position.  I therefore decided that the 1700 cell pack (395g) would be replaced by two 3S1P Lithium Polymer (LiPo) packs which would weigh 150g each.  I bought two 12C Tornado 2200mAh LiPo packs and modified the nose aperture to allow them to be fitted.  The enlargement required to the battery slot meant that the balsa was even thinner at the front of the slot.  To restore the strength at this weak point, I cut a slot top and bottom and glued a carbon strip in each.   The model now has a slightly larger frontal area because of the width of the packs, but the power has almost doubled and it is 60g lighter - should be fun.

29 Jun 03 - First flight completed.  I was a little disappointed with the performance as the model is underpowered.  I will fly it a bit & then probably fit a different motor.   The model is fitted with a Graupner Speed 480 Race in a WeMoTec 480 Mini-fan running on 8 Sanyo CP-1700 through a Jeti JES 500 speed controller.  The static tests 22200 RPM @ 8.7V drawing 15.5A, input power 135W = 67W/lb.  The flying weight is 890g (1 lb. 15½ oz.) giving a wing loading of 15.7 oz / ft² (47.8 g/dm²) and a WCL of 11.1 - Aerobatic / Scale (Great for a fast jet)

14 Feb 03 - I completed construction today and applied all the stickers I'd made. The tail flags were taken from photographs of the Belgian display aircraft, loaded into Paint Shop Pro and manipulated to fit the semi-scale outline of the model. They were then printed onto white inkjet labels and covered in Fablon before fitting. The silver stripes on the wings are cut from 'Sky Sheen', a holographic self adhesive film that is sold by Gordon Tarling. I will probably add more markings after the first flight.

11 Jan 03 - I started construction this morning, the kits is CNC cut and is extremely well cut. The fuselage is made from 10mm balsa and is cut to finished shape with only small tabs holding it in place (and these are cut to about 3/4 depth). I decided not to fit 2 aileron servos, but use 2 Hitec HS-55 servos instead of the recommended Graupner C261's. The fuselage had 2 apertures cut for suit the Graupner servos, which needed to be slightly enlarged for the Hitec HS-55s. I also robbed the Webra receiver from my Twin-Star as it is much more suitable for this model.

1 Jul 02 - The construction is entirely from CNC cut balsa, which will very quickly produce an extremely light structure. I might modify the design slightly to fit two aileron servos as this allows more options.

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