Pico-Jet Combat by Multiplex

23 Mar 07 - Brushless motor and LiPo battery pack test flown.

Mulitplex Pico Jet Combat Multiplex Pico-Jet Combat Multiplex Pico Jet Combat

N of launches / Time 87 15 hour 20 mins Figures left include all motor/battery combinations
Wingspan 35.2 " 0.895 m
Wing Area 320 in 20.6 dm
Flying Weight 1 lb. 11 oz 0.79 kg 1 lb. 10 oz 0.75 kg 1 lb. 6 oz 0.65 kg
Wing Loading 12.6 oz/ft 38.3 g/dm 11.9 oz / ft 36.4 g/dm 10.2 oz / ft 31.2 g/dm
Wing Cube Loading 8.4 - Between the Trainer and Aerobatic 8.0 - Between the Trainer and Aerobatic 6.9 - Trainer
Motor Mulitplex Permax 450 Turbo Mulitplex Permax 480 7.2v HiModel CF2812 brushless, 1534 RPM/v
Propeller Aeronaut Elektro Glas 6" x 5" (White) Graupner CAM 5.5" x 4.3" APC-E 7" x 5"
Batteries 8 Sanyo 800AR 8 Sanyo 800AR or 2700mAh NiMH
Click here to see static tests
Airpower Models 3S1P 2000 mAh LiPo (18C) pack
Speed Controller RC Line MSC-30B - 30A - 5 to 10 cells - BEC & Brake HiModel HM-18A-S1.1 - 18A - 2 to 4 LiPo - BEC, Brake & Melody unit
Receiver Hitec HFS-04MI - PPM - 5 channel - 35 MHz
Servos Elevons - 2 x Graupner S3103
Static motor parameters 14800 RPM @ 13.4A, 8.5V = 114W
Estimated output power 65W/lb.
With 8 Sanyo 800AR cells
14000 RPM @ 11.4A, 8.8V = 100W
Estimated output power 35W/lb.

With  8 Sanyo 2700mAh NiMH
13700 RPM @ 10.5A, 8.0V = 84W
Estimated output 32W/lb.
Note
: With these cells the motor runs for 16.5 minutes at full power on the bench

12150 RPM @ 16.0A, 10.85V = 174W
Rod Badcock's thrust calculator gives an output power of 120W at the propeller (70% efficient) which gives 84 W/lb.
Flight performance This is a very nice model that handles very well. Climb out is at a comfortable 20 at a good speed. The Pico-Jet is quick and rolls very quickly. Loops can be completed from prolonged level flight (even outside loops). It also glides very well and long flights (>10 mins) can be made with full power climbs and glide descents. With 8 Sanyo 800AR cells - Climb out is slightly shallower than with the 450 Turbo motor, but it is lighter and glides slightly better. All other flight performance is much the same.

With 8 Sanyo 2700mAh NiMH - Climb out is significantly shallower, but all manoeuvres can be completed. The main difference is the flight duration, which is about 20 minutes.

Stunning performance, will maintain a vertical climb indefinitely and duration is estimated as 20 minutes.

27 Mar 07 - I completed the 1st first in the new configuration today.   The performance is superb with the Pico-Jet maintaining speed in a vertical climb.  I flew for 11 minutes and discharged the pack to find 1000mAh remaining.  A flight duration of 20 minutes is therefore possible, however, I will set the timer at 13 minutes to maximise the pack life.

7 Jan 07 - The old ferrite 480 motor was starting to lose performance making flying the Pico-Jet less pleasurable.  Therefore I have just fitted a brushless motor and Lithium Polymer power pack to increase performance and reduce weight.  As you can see above the weight reduced by an amazing 100g, which is around 13% of the original weight.  Combined with the increase in power from 35W/lb to 84W/lb performance should be much more exciting.  The front of the propeller is also now 48 mm (1.9") from the trailing edge of the wing, hopefully this will keep the noise reasonable.

15 Oct 00 - I have now been using, on and off, a pack of 8 Sanyo 2700mAh NiMH cells. These cells are exactly the same size as 800AR cells, but weigh about 6g (0.2oz) heavier per cell. Climb out is slow, but duration   is superb at about 20 minutes. Once height is gained the power can still be reduce and the model cruises really well. Click here to see a static comparison between the 2 cell types.

10 Jul 00 - I wanted the 450 Turbo motor for the resurrection of the Aztec 2 Step+. I bought a Multiplex Permax 480 motor & Graupner CAM 5.5" x 4.3" propeller to fit in it's place, which is the recommended motor & what most people are using. The 480 motor is lighter than the 450 Turbo, but it is a very small difference. Overall, with a smaller propeller and lighter propeller adapter the weight saving is 1 oz. (40g).

14 May 00 - I had seen the original version of this model (Expanded Polystyrene (EPS) foam) about and after discussing it with others decided I should have one, just for fun. The Combat version has recently been launched (pun intended) and is made from Expanded Polypropylene (EPP) foam. EPP foam is much more resilient than EPS and more suitable to flying from rough surfaces. Another advantage (as far as I was concerned) is the Combat model does not come with motor and propeller (unlike the standard version). This allowed me to use any motor I fancied without wasting the motor that would have been supplied.

I started assembly on Friday 12 May 00 @ 23:00 and completed on Saturday 13 May 00 @ 17:00. This period also included a modification to the design, sleeping, eating, shopping and going down the flying field. The construction is very straight-forward and produces a very nice model.

I know of a few people that have broken the model when pulling high negative g (outside loop or similar). In light of comments I had received, I incorporated a modification during the build. This was to install a carbon sheet spar (from some offcuts I bought) into the top surface of the wing. If you look carefully on the 2nd photograph above you can just see the slot emerging from the fuselage towards the decals on the wing. This reinforces the fuselage for negative g manoeuvres, which is known shortcoming of the design.

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