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Author Topic: Micro Jet  (Read 680 times)

Andy M

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Micro Jet
« on: July 30, 2020, 12:18:15 PM »

Looking through my collection of plans on my laptop, looking for my next micro project, I found this nice little jet. I have one already, dayglo orange for visibility, lol, but I wanted a micro version, so a bit of resizing on photoshop produced the size I wanted. 29cm wingspan. Just big enough for me to get the wing from the remaining bit of reclaimed 3mm depron. Not bad considering I have got a delta and wings for the jupiter junior out of the old recycled wing skins already.
 One fuselage side is made from it too, I had a nice new bit for other side and top and bottom. The pic showing parts doesnt include the fin, didnt notice till after I glued it all together. Not many parts for a lovely little plane. Goes together easily and has plenty space up front for different sized batteries to be positioned to get centre of gravity correct. A 100 mah right up front balances perfectly or a 200 further back. I used bamboo blind pushrods, a bit heavier than carbon, but all I have. Tailerons for control. It was under 30g with 200mah cell, prior to painting. I need to weigh it again and see what I have added.
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Andy M

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Re: Micro Jet
« Reply #1 on: July 30, 2020, 12:20:34 PM »

Add some paint......
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Subculture

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Re: Micro Jet
« Reply #2 on: July 30, 2020, 09:10:15 PM »

That'll be a handful!

Andy M

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Re: Micro Jet
« Reply #3 on: July 30, 2020, 10:14:30 PM »

Yip, lol.
 I am hoping my experience of flying the tiny delta will help with this. Even though I lost that one in a barley field in windy conditions. I have test flown the micro jet, again in a wind, and crashed into a tree, it fell out ok, only a muddy nose. It was responsive, I had already turned down the throws and its still a bit sharp.
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Andy M

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Re: Micro Jet
« Reply #4 on: July 30, 2020, 10:25:10 PM »

I thought I should add that I feel much better test flying these little planes if the control  board is inside a fuselage or has some sort of protection. Having said that, I didnt have any damage occur to ones just stuck on top or on the side. They just look delicate. 😁
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Subculture

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Re: Micro Jet
« Reply #5 on: July 30, 2020, 10:32:41 PM »

Something like a cc3d atom would  help draw its teeth- course you have to tune it , and you'd need to decase it to keep the weight down.

Andy M

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Re: Micro Jet
« Reply #6 on: July 30, 2020, 11:49:52 PM »

I will try it again with more space and less wind. The delta was a handful till I got more used to it, dialed the throws down a little and that tamed it. I cant really afford any extra weight on these little planes, even a 2g heavier battery can make a fair difference. I should invest in some new batteries, I only have a few apart from the e-cig cells I have been using on most of these. They still fly but not as long as my friend's nice new ones.
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Andy M

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Re: Micro Jet
« Reply #7 on: July 30, 2020, 11:53:43 PM »

Dummy ailerons and flaps drawn on with fineliner. Same on the underside helps disguise the recycling scars on the wing.
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warspite

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Re: Micro Jet
« Reply #8 on: July 31, 2020, 10:54:09 AM »

Its like a mini tornado - pun intended  :-))
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Andy M

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Re: Micro Jet
« Reply #9 on: July 31, 2020, 06:23:10 PM »

It flies nice, had to add a fair bit of up trim, but flew nice and straight. Does big loops and also tried some rolls, been a while since I have managed any rolls, due to mostly building undercambered wings for a wee while. The motor got warm enough to melt the hotglue, motor moved forward and the prop got stuck to hotglue. Picks off easily though, I need to put in a peg to stop it moving forward and also get some cooling holes cut. I may even cut 10 mm off the motor mounting area of the fuselage so half the motor is out in the breeze. Sounds like a plan.
The micro jet scoots about nicely on half throttle and has impressive full speed performance as well. (I can see how the glue melted, lol.) amazing that a 7mm x 20mm brushed motor can push it up to that kind of speed
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Andy M

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Re: Micro Jet
« Reply #10 on: August 01, 2020, 05:44:09 PM »

Slip on depron tip tanks, tiny fins from ice cream tub plastic. I painted them yellow, thinking that might stop my orange flourescent spray from eating the depron, which is a bit of a pain. I may leave them yellow. Maybe make another set for painting orange.
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Andy M

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Re: Micro Jet
« Reply #11 on: August 30, 2020, 09:56:26 PM »

Here is a short video of it flying, it takes a bit of practice, I have flown it for longer than this.
https://youtu.be/pY1KXQ0mk5A
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Andy M

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Re: Micro Jet
« Reply #12 on: August 31, 2020, 05:09:09 PM »

After a flight the other night, the motor made a strange noise, I went to check the prop was attached properly, found it was loose enough to just fall off, for some reason, so I felt the motor, hot hot hot, I touched the motor shaft, burned my finger,so I have added cooling vents and also shaved the tail end of fuselage where the motor attaches. I have picked all the hotglue off and motor is now held in with 2  3mm strips of fibreglass tape. A good bit of the motor can is exposed each side. I am hoping this helps.
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Andy M

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Re: Micro Jet
« Reply #13 on: September 01, 2020, 04:50:29 PM »

After cleaning dirt off the nose with a wet bit of kitchen roll, I found hardly any damage, couple of bits of embedded dirt and very little actual damaged depron. I have seen this little plane go into the ground pretty hard. Too many times actually, its pretty tricky to fly, especially right after flying planes with undercambered wings. It has a lot of torque roll, which is ok, but trying to get enough trim on the elevons means a lot of drag so I decided to tweak in a bit of up on the left wing trailing edge, this helped a lot. It can fly relatively slowly but the controls become less effective the slower you go. It is happy around half throttle and becomes a little rocket on full power. Amazing little plane, I just need to learn to fly it better, it is small, so I expect it to be twitchy. My friend had a shot, thinking it couldnt be that hard, managed about 20 seconds with some hairy maneuvers then managed to hit himself with it and half tore the wing off. If it didnt have the fibreglass tape 'spar' top and bottom, it would have just torn off. I used tiny amounts of uhu glue and a 1 inch square of fibreglass tape to repair. The motor cooling seems to work, the prop hasnt moved, even after a couple of javelin type landings. Lol.
 I am still amazed that a 33.7g rc plane is even possible! And its fast, tough, cheap, and runs for as long or longer than most glow engined planes I have had.
 Total depron cost is probably 2.30 (The average sheet price for my assorted pack) a motor from dead quadcopter, battery from an e-fag, pushrods from a bamboo blind, with paperclip ends. I have run out of 1mm carbon for pushrods, its lighter than the bamboo. Then 13 for the board which can be moved between models easily. Incredible, and a bit of recycling too. I forgot to mention uhu glue, probably about 10p? I have built at least 10 models from the tube. From a poundshop.
 Removing the cost of the radio bits leaves a 2.50 airframe, more if I use carbon. And they store easier than my 1/4 scale K8 glider! It was considerably more than 2.50 though, its worthy of very careful storage. Lovely kit, I was in two minds whether to cover it or not.
 Anyway, I hope to get better with the micro jet and get a decent flight on video.
 
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Andy M

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Re: Micro Jet
« Reply #14 on: September 03, 2020, 09:36:14 PM »

I got a call from my Mum about the Wltoys F949 boards I had ordered, customs had sent them back and I was issued a refund, no reason given. Waaaaaah. It said I could re order them..... another 2 months odd of waiting time, be winter by then! Just need to make do with what I have and get used to moving boards between models, nothing is ever a big task on these models, especially if its had a board before and the pushrods are already on the model.
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Andy M

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Re: Micro Jet
« Reply #15 on: September 05, 2020, 11:31:40 PM »

Having flown the micro jet I liked the look of it and had fair bit of success considering its twitchyness and tiny size. I decided a bigger version might be more docile.
 I settled on 1.6 times the size of the micro jet, the reason for this figure.... The wing just fitted on my biggest bit of 3mm depron. Anyway, it looks much bigger, and has well over twice the wing area. It did need 4g of 3mm  carbon spar in the wing.
 Tailplane and fin are 3mm depron too.
 Fuselage is mostly 2mm, first photo shows the construction with a socket for wing to slide into, lined top and bottom with 2mm. 6mm bits are used in areas to be rounded. Also managed to use up some dimply pizza tray. I mounted the radio board in a small square of this, trimmed to clear motors on bottom of board and some components. I have hotglued it to this in a few places, away from components. The assembly fits snuggly in a frame of the same material, I am going to use this method in as many of my planes as possible, it works really well and is easily swapped between models. Who needs a 3d printed clip.
 I also have the Syma X7 motor and gearbox mounted on 6mm depron so it can be swapped too. Two pieces of fibreglass tape secure the assembly to the fuselage, much more than it needs. The tailplane isnt glued in its slot, it is held in place by a snug fit and small slots that take 2 tabs on the fin, locking it in place. The fin is a snug fit that doesnt need anything to keep it in place. Thrust from X7 motor unit is around 25g, maybe 30 for a good one. Should be enough.
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Andy M

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Re: Micro Jet
« Reply #16 on: September 05, 2020, 11:32:36 PM »

More photos
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Andy M

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Re: Micro Jet
« Reply #17 on: September 05, 2020, 11:39:37 PM »

Some video to show it flies well, could do with a bit more power, but it flies for ages on a single e cig cell with this motor setup. Also tried tweaking the wing to counter at least some of the torque roll, it transformed it instantly, it was able to turn left easier, I had been holding in loads of left to keep it flying level and there wasnt enough left for turning. All sorted now.
Video of it flying here
https://youtu.be/3ckDpN1YTBg
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Andy M

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Re: Micro Jet
« Reply #18 on: September 05, 2020, 11:47:36 PM »

I just noticed in the picture of the 3 jets, the bottom one is not 12g, its 112g! It is mostly 6mm depron, and quite a bit of it.
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Andy M

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Re: Micro Jet
« Reply #19 on: September 06, 2020, 08:54:58 PM »

A few weeks ago I started dismantling  a quad bodyshell I had built years ago, I discovered I had gone a bit over the top with balsa dust and superglue, big fillets of it holding the gearboxes to the stub wings. It did fly when I built it but it was a lot of bodyshell and pod for the motors to carry, resulting in the 1000mah (so it says anyway) battery lasting only a minute or two max. Ah well I enjoyed building it.
 Its time for its motors to power something new.
  Myself and my friend did tests on various motors, with these ones coming out on top with 50g of thrust! Thats a lot down at these plane sizes. Anyway, after flying the bigger jet with only 25 odd grams of thrust, I decided to put one of these in it. I had to sand off some casing to fit it in the plane, but its in nice, only worry is that the motor is bigger at 10mm, looks huge compared to the 7mm motors we have been using, with it producing nearly twice the power I was worried it would fry the board. It turns out that the board handles it fine, whew. Lol. It could have just burned out first flight.
 The extra power was noticeable right away, speeding things up a bit. Its still not that fast really, but it climbs out better, I even managed a big loop and some slowish rolls. It is a lot more comfortable to fly than the tiny one, especially with the extra power.
 I have to use 3 e cig cells to balance it now, it needed 2 for balancing smaller 7mm motor, so with 8mm motor/gearbox adding 4g extra and a 6g fag cell, its an extra 10g. But its well worth it and doesnt seem to affect flight at slower speeds. All in all its turned out to be a nice flying little plane. The micro one could probably do with some anti torque wing tweaking as well, see if that helps its handling qualities.
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Andy M

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Re: Micro Jet
« Reply #20 on: September 09, 2020, 09:18:48 PM »

I decided to do something about the jet needing 3 e-cig cells to balance it. I drew out a wing with more sweep, it looked about right, only thing was that I didnt have a bit of 3mm white depron big enough, so a quick text to my friend (who bought the last 2 boxes of the assorted depron)
 He got back to me, sorry, he wasnt selling any of his. Ah well, just need to be a superlight grey wing, I have a decent amount of 3mm grey left, its just pretty floppy compared to the white, also I didnt have any 3mm carbon left for a spar.
 A kebab stick spar and two bamboo  leading edges stiffened it up a bit.
 By sweeping the wing back, it now needs only one e-cig cell to balance it, the wing is also a gram lighter than the original one, and slightly bigger area.
 Total weight saving.... 14.3g! Thats massive on this size of plane, the radio board and battery only weigh 12g so its got to give a decent performance boost. I dont expect it to go much faster, if at all, but it should fly on much less throttle. I have still to test it to find the exact balance point but its looking quite close, the single remaining battery can be moved about to fine tune it.
 Weight at the moment is 61.5g, it was 75 odd. 20% of its weight is gone, so my floppy wing will have less weight acting on it. It is pretty flexible, and stiffening it up all adds weight. Will try it like this and see how it goes.
The photo shows a paper template of the wing, will get a photo of the grey depron version soon.
Turns out it still needs 2 e cig cells to balance right, but even at that I have saved over 8g and its noticeable right away.
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Andy M

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Re: Micro Jet
« Reply #21 on: September 10, 2020, 01:26:10 PM »

Here is some video of it with the lighter wing and only 2 cells. Very windy but it shows it can cope with it fine, considering it weighs 61.5g!
I am well impressed with this little 'jet'. Its not blistering performance due to a fairly large fuselage cross section and a tiny motor. It is large compared to my usual 7mm motors, but still a tiddler. The orange 6mm depron version isnt that much bigger and its supposed to get a brushless set up. I am working up to getting that flying now I have tuned my reflexes on the smaller versions.


https://youtu.be/J3p2CEiy19k
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