Pico-Jet Combat

click on pics to see full size

 

Used in original review

Pico-Jet Combat (PJC)
Permax 400 6v motor
Gunther prop
8.4v 1100mAh battery
35A BEC Speed controller
Mini 4ch 35Mhz R/x
Micro servos X2.
All up 700g ready to fly.

  

In brief

An EPP (expanded poly propyleen) delta wing for speed 400/480 motor & suitable r/x & s/c requiring 2 servos & elevon mixing.
Cyno-acrylate (superglue) used entirely during construction.


 

Building

Construction is simple with 3 main parts.
The wing and lower fuselage body are a moulded single piece.
The tail fin which is superglued to the back of the fus' between the wings above the motor housing.
The canopy top cover is held on by a strip of ply hooked under the glued on tail and clever rubber band hooks to hold the nose together.
Motor fitted (thrust line is moulded into the mounting area) wiring is routed through the grooves under the tail. R/C-Line 35amp BEC speed controller hard wired to the motor loom before fitting to ease installation. 35A is a little overkill, but the R/C-Line item is very small and was spare.
Internal tray glued into place and velcro added for r/x. Jeti mini 4 channel reciever installed. Ariel lead fits into a pre cut channel along the wing. Wiring secured with cyno drips at intervals.

  

Mods on the fly

Motor mount lined with 1/64th beech venier and small blocks glued to underside of tail to hold motor for glueing. This allows epoxy to be used to secure the motor. Make sure the motor air vents align with the ducts built into the fuselage sides.
Speed controller wrapped in Flair alu-clad to reduce interference. R/x fitted and wrapped with protective foam & ariel routed though fus' side using control snake inner.

. . . .

  2 hardwood strips (1/4") are glued into the aileron slots for the 2 horns to attach to. 2 MS-X2 servos fitted into the wing cutouts with double sided tape. Wiring needs to be extended to reach r/x along very neat channels in the wings. 2 supplied pushrods fitted and attached to the horns via barrel fittings. Glass tape fitted to tops of wings as directed to protect the hinge area of the elevons. Control surfaces cut out of main moulding using sharp knife or slim fine toothed saw.
Aileron pushrods aligned and secured. Transmitter used has Delta/Elevon mixing and was also set up and trimmed at this point. Servo slots covered with glass tape to minimise dust & water ingress.		  

Wiring tip

When cutting the servo connectors off to fit extensions, cut the wire 3 different lengths at 1cm intervals. When soldered neatly and shrink wrapped this will not cause a bulge in the wiring channel.

. . .

 

Connecting the speed controller to the battery, the propeller was fitted and the motor was tested.
Initial checks looked like everything was fine.
A glide test on the local slope over a large patch of long -impact absorbing- nettles proved the centre of gravity needed adjusting back.Thank the maker for nettles & long live the Velcro strip.
A quick shuffle of ni-cad and foam and another test throw. It still dropped quickly. Balance and C of G checked again ~ OK.
New tactic - a much harder throw. The Pico-Jet glided off into the field.
Powered flight was the next test. Full throttle was making some good wind from the rear, a hefty chuck and the Pico-Jet sank into the nettles like I had fitted a flight box battery to it. ( ~ see the mods ~)
A quick turn coat for the prop and a few laughs later the Pico-Jet was launched from the slope and the nettles were just a memory. It flew in a stable shallow climb, slight trimming to the left required to straighten the flight.

  

Mods on the fly

Gunther props are supplied as tractor props. When fitted as supplied they are facing the wrong way. Pull out the black section, reverse the white blade section and re-fit. A reversed prop appears to be working but is highly inefficient.

. . .

 

Additional notes

With flights of around 6 minutes at full throttle getting some good altitude, gliding can be used to extend flight times.
The first casualty was the Gunther propeller, a dodgey launch and a sudden gust of wind caught the Pico-Jet and as it hit the floor it spun around it's nose and snapped one of the blades off.
How many people asked 'how did you break one of those?' ~ I lost count but eventually found a source of new props.
Put off by a 3 day wait, I picked up a free flight rubber power one piece prop. Pitch unknown but it worked well enough to fly.
After a second Gunther prop departed ~ this time simply detaching from the motor under thrust and whirling away into the long grass ~ a spun aluminium prop adapter was found and an FK 6x3 prop used to replace the 5x4.5 Gunther.
Another concern was the rubber band holding the top on. This was replaced by a single bolt at the rear of the Canopy section, passed thru some snake outer to prevent the foam crushing. A small captive nut was secured to a balsa block and glued above the speed controller. The front is now held down with 2 strips of velcro.

  

Mods on the fly

6 different props have been aquired for testing and a crude thrust measuring device has been found.
A table of these findings along with flight times and percieved speed differences is reported on in the Thrust Test under Articles. (or click here)
Props in list are:
5x4 Gunther (standard)
5x3 Thimble Drome (cut down)
5x??, Bow Tie (band power)
5.5x4.3 Cam speed prop
6x3.5 Windsor prop
6x3 FK (yellow bendy) prop

. .

Forum

Don't forget to visit the Pico-Jet Forum to ask a question, add a suggestion or simply seek tips on flying your Pico-Jet.

The Update.
Completed 30-04-2001

  To Recap
It all started when I bought my Pico-Jet Combat ~ ''Indestructable'' they said. And for the most part they were right. Having assembled the required parts to complete my PJC I set about the clogged up superglue and got to work. The following day Choddy and I went to test fly it. Nice day, mild wind, a hearty throw and the PJC sailed effortlessly into the long nettles. After the laughter had died away we decided the propellor was actually the wrong way round and a quick swap around and another hefty chuck and away it went. Some trim and all was well. A few further flights returned about 6 - 7 minutes of stick time. A few days later, hardly able to wait to show my new toy off, a few mates visited and we headed for Bumpy Green site-2 (electric only)
A swift control surface check and a blast from the motor and I was ready to astonish.
A reasonable launch suddenly turned bad and the Pico-Jet hit the dirt in a dying spin .... .... .... and broke the Gunther Prop.		  
  Yes, they all said it when I tried to buy replacements ''How did you break one of those'' Normally this is a very valid statement and Gunther props are usually very bendy. For some reason mine was not. Having ordered 5 new props (none in stock) from the local model store I was about to leave and wait 3 days for any more Pico-Fun, when I spotted a propellor that bore a striking resemblence to a Gunther. It was a rubber band powered model prop. By all descriptions (including that it looks like a comical bow-tie) this propellor should not fly this model. Well I was determined not to be grounded for 3 days. A small drill later and the bow-tie was ready. It fitted tightly to the motor shaft, it did not slip when held still, it did not fly off (see above & Topic 400 review) and it appeared to work. It needed to be fitted with the built in spinner facing forward.  
  Once again to the test slope, with the long cushioning grass and a harder then needed throw the PJC was away and flying. It was a little sluggish but it was working sufficiently to fly the model. I actually kept this prop for a few weeks having just bought two 9.6V 1300mAh battery packs from Overlander and they seemed to make quite a difference. Being the same size as a transmiter pack and weighing just 200g (the 8.4v 1100NiCad weighs the same) the effect was good, over 10 minutes of powered flight if kept tame and so far my best is about 20mins with use of half power.  


See the results of the testing here

Overall.

  I have now been flying the Pico-Jet for some 8 months, and in that time there have only been a few weeks where I didn't get at least one flight in (some weeks it was just one flight in a day because it was so cold) I even tried to fly it when the gound was covered in snow. It was a freezing cold but clear blue day and the sun was just begining to reach a warming height. I had left the Pico-Jet in my car overnight. Big Mistake. The frozen batteries did not want to play. About half thrust from the NiCads and even less from the Ni-mh cell packs. Having buried the PJC in the snow twice, with just it's tail tip showing (good job it wasn't white) I called it a day and went home, cold and miserable. It did however demonstrate the need for battery packs to be at a reasonable temperature before flying.
More tales of joy and horror to follow.
A movie of the Pico-Jet in flight and doing some of the mad things you would only try with an EPP plane will be made soon.		  

 

Indestructable?

 . .

  I can now conclude my studies of 'indestructable' ~ It is, almost.
So far I have managed to snap the nose off the Pico-Jet twice. Each time I just grabbed the superglue and fixed it back on
The 3rd occaision (which just reopend the old war wound) I used a small diameter dowel, about 3 inches long pushed into the foam each side of the break and cyno'd into place. A sheet of balsa about 30mm x 100mm x 2mm has now been laid into the bottom of the battery bay as the internal plastic tray had lost all ability to stay back together. It also now weight about 725g after all the glue and mods were added.
The tail and wings have both lost the tiny pointed tips but have suffered no other damage at all. Several full power strikes from playing too close to the ground have done nothing to the model. The funniest but so far the softest crash was recently. Flying inverted at fairly high speed, pushed the elevators forward to do an outside loop and the battery fell prey to gravity and overcame the sticking resistance of the velcro holding the lid on.
The battery plummeted to earth and the Pico-Jet floated down spinning like a sycamore seed. The canopy ejection was almost realistic.
Superglue saves the day each time.
I would not have had much flying at all recently except for the PJC, what with a bitterly cold winter and then the foot & mouth disaster.
Glad there are some places I can get a good session from the Pico-Jet at.
My most flown plane this year.		  

 

Comments left by others...
Comment by Lawrence Hamburg on 00000000000000. Rating none

This is a model that flies well, but needs a helper to launch it - I have nearly broke the nose twice in 6 flights, and every time this was due to needing a heftier launch - it is hard to hold. Has anyone found a foolproof way of launching it. Lawrence

Comment by Matt on 00000000000000. Rating none

Yes!! I practiced this with a Bullet on the slopes and now use it on my Picojet, Twinjet and Wattage P-51 Reno Racer all the time. Start with your plane in your left hand and radio in your right(no neck strap) so you have ele/ali controls. Hold the plane up above your head, knock the throttle to full with your side/or what ever you can, now take a few steps forward(into wind) building up your speed to a steady run and then launch with a smooth level throw. This is done in one move. Remember to check it's safe to launch because you'll be advancing down the runway while launching. Also remember to take control of your rudder/trottle as soon as. It's the combined speed of you running and your "throw" that ensures the plane has enough speed/lift to fly. As I said this DOES TAKE PRACTICE more so because your lanching with your left hand unless your left handed(an advantage). Don't just go and try this with your brand new twinjet or something, start easy, say a picocub or an "unbreakable" EPP thing ie a bullet. Most of all don't try too hard to throw your plane, thats when accidents happen, be gentle, that way you'll just land or do a daisy cutter as I've done in the past if its too slow.(no violent throws leading to broken planes). This took me a month from start to finish to perfect. Happy landings!!

Comment by Rob Atkinson on 00000000000000. Rating none

Hi, I've been flying the Picjet for some time and have upgraded to a new Micro-Jet. I need a foldable pusher prop for this model as the keel is only about an inch away from the ground and snags the prop. A slight overslight on Multiplex's part me thinks. Anybody know of a good prop. I will reverse the polariry of the motor to cater for the pusher prop config, but it needs to be a foldable prop. regards Rob Atkinson

Comment by Think on 00000000000000. Rating 5

I have just bough a pico jet, and tryied to fly it with a 400, but the plane dont seem to have much power. could any one tell me what this could be? I use a jamara variator and a gunther prop and a 7 celled pack of 3300

Comment by Bumpy Green on 00000000000000. Rating none

Hi there Mr Think, I would say your prop is on back to front, they come as standard as tractors but you need if to be a pusher. See Speed 400 prop study in Articles. Regards, Bumpy Green

Comment by Pico-Choo on 00000000000000. Rating none

7 cell 3300 ?? Is this using Sub C cells? If yes then this pack may be too heavy for the Pico Jet.

Comment by Think on 00000000000000. Rating none

Thanx pico choo, i changed batteries and put a 480 and it flies perfect.

Comment by Pat on 00000000000000. Rating none

I have just crashed my Picojet for the final time. I was just trying a bit of inverted flight as the nose was going down I pull a bit of up realised my mistake and pushed a LOT of down and the wing and fin tore right off. When you look at the remains the foam is very thin at the fuse to wing fillet area. I am going to miss it.

Comment by Richard on 00000000000000. Rating none

I'm normally a free-flight person and I like CO2, but I am very, very tempted by the elegant simplicity of this range of models. (I'm not interested in lugging fuel and starters, etc. around the countryside.) Only trouble is, the guy in my local model shop won't sell me one! He assures me that I would crash instantly, destroying the 'plane. What's a normal progression route up to a Picojet (or similar)? I'm not very interested in rudder & elevator high-wing monoplanes!

Comment by Steve MACHIN NW9 on 00000000000000. Rating none

I have one of the older grey PICOJET and I have a 480BB Race 7.2v in it.It goes well with a 7/8 cell Sanyo AR pack which fits very nicely in the fuzz.I am currently using a 14/11 CAM prop , however , the motor does get hot but the semi external mount helps.A tip put the prop as far from the T/E as possible and this keeps the noise down which is a little excessive , I think it is because of oscillations over the T/E by the air flow

Comment by Adam McClean on 00000000000000. Rating none

I am getting a pico-jet this christmas and i have had several R/C Aircraft but i am just wondering,what top speed will my pico-jet be capable of with a 480 motor, thanks, Adam.

Comment by John Noble on 20040328202022. Rating 5

Had a PJ Combat for a while now, but never bothered with the 400. I went from the off with a Magnetic Mayhem,7x4 Pusher, 7 Sub c's. Go's like summat crazy! Only thing you got to watch is getting it into a flat spin...can't get it out! And no...it doesn't glide like a brick. It has plenty of wing area.

Comment by Steve MACHIN NW9 on 20040611205301. Rating 4

I have one of the grey foam Pico jets and I fly mine with a MEGA 16/15/4 Brushless and a 6x4 COX Black fixed prop using a variety of battery packs . The best seems to be a 8 cell ARSanyo 800 pack with this it really moves . I made a 1/32 ply sadle at the rear and then held the motor using tin rubber top and bottom ( from a pair of washing up gloves ) and then rubber bands to hold it attached to two hard points ie dowel either side of the saddel. The only grummble that this is a very noisy model which is probably due to the sound box effect of the foam and close proximity of the T.E.to the prop Steve London NW9

Comment by A J on 20050314112110. Rating 2

Use sanyo 1700mah hv-4/5up overlander nimh,flying time 10/15mins

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