WASP - an RC lightweight plane by RaavHimself

Last crawled date: 2 years, 11 months ago

This is a work in progress. You are invited to participate and share
Files are also in STEP format so you can build upon them.
Files include motor pods for all the versions of the plane created. Also the parts for the two tails (V and normal are included)
Believe it or not, I didn't know anybody who had got sick with COVID until my girlfriend did,  and now I am stuck at home for the next ten days, so I have have plenty of time to write my story here, and fortunately and most important, I'm healthy. So enjoy.
I don't know if the problem is that I'm a terrible pilot or a terrible builder, but I have had my fair share of 50 hour builds followed by 5 second flights. If the maiden flight is also the final one, and that happens more often than not, it's a moment to reconsider what you're doing. and how you're doing it.
So 3D printing planes looked like a good idea, at least theoretically. Planes basically get done by themselves and geometries are always perfect, right?  Not, so. Not for me, at least.
Those thin walled one perimeter parts are difficult to produce, so failed prints and rejections are a normal, printing takes forever, postprocessing and glueing is not so fast neither that easy and the final result, though beautiful, is everything but resilient.
So I've decided I'm making my own design and here are the constraints it will have to accomplish:
1-Fast and Easy to build
2-Cheap, Very cheap
3-Survivality- Must be resilient, hardy, endurable
4-Small enough and big enough for whatever
5-Easy to work with, adjust and setup
6-Design must be easy to modify
Well, that's a lot, I guess, isn't it? But at least I'm not asking it to be pretty. So I thought I might as well look for advice here and publish the design I am working on. Maybe something nice can be done 'with a little help of my friends'...
Of all the constraints I have set for the design, the one most confusing is number four. Small enough and big enough for what? Small enough to be flown indoors and big enough to be flown outdoors. Small enough so it can be taken to the field riding a motorbike instead of a car, big enough so it can carry an FPV set aboard,... I suppose you get the idea and you're thinking about a certain size. So did I. I could do with detachable split wings, but has to be a pretty small plane, mainly because small planes survive crashes better, I guess.
As I have basically very little idea about plane designing, or aerodinamics, or the Reynolds number, or any of that things that you people are familiar with,  I am relying in the following ratios that were given to me by someone whom I believe is wiser than me. He said:
 "the aspect ratio would be 5:1 so the chord would be a fifth of the wingspan.The fuselage would normally be 75% of the wing spanNose to leading edge is around 20%
Trailing edge of wing to horizontal stab 20% (of which the horizontal stab area would be 20% of the wing).
The Vertical stab is usually 1/3 or 33% of the horizontal stab area etc etc"
Obviously, the worrysome part is the "etc, etc" that hints there are a huge number of aditional things that I should know but I don't. Anyway, I'm going on with what I have. The design should be easy to modify, shouldn't it?
So here I go:
1st iteration
Wingspan 50 cm - Weight 55 g incl Batt (18 g)
Surfaces - Wing 500 x 90 mm Tail 2 units x 80 x 60 mm - 90º
Main Fuselage is a 300 mm rod
Design is a mixed construction of 3D printed parts, carbon fiber rods and foamboard. Originally I intended to usesome thin foam from disposable dishes or trays but I guess they have been banned for environmental concerns or something, because I can't find them anymore. Everything disposable is made out of paper or plastic, and the foam I find (like the one in McDonalds foam boxes) is just too small. I don't even have 3 mm foam board. I will use 5 mm instead. I hope I will find something more suitable later.
When my girlfriend has seen it, she has said "it looks like a wasp". It really doesn´t, but as I need a name to write in the TX menu, this one sticks.
Printed with PETG. Wheel Tire with TPU
Rods are Carbon Fiber 2 mm and 1 mm
Surfaces are 5 mm Foamboard though they shouldn't be.
I am using an RX brick with two 1g servos and a built in 3A DC ESC. First thing I`ve learnt is that servos are perhaps too small. I have made everything work perfectly but it has required a very fine adjustment of the control rods and perfect hinges. I've made the control rods with .5 mm piano wire and 1 mm CF
]The RX brick has also brought alongside the V tail, because it's easy, convenient, I've never tried one and why not.
Motor is brushed 8.5 x 20 mm. Motor, gearbox (aprox 6:1?) and prop (135 mm diam, no more data) come from an old HUBSAN 502 Drone, All these parts that can be found easily as spares in Aliexpress.
Battery is a 250 mAh 1S
Landing Gear is 1 mm piano wire
After the first Flight Test
It lacks power. A little problem here because although the Hubsan dron worked with 2S batteries, the brick works with max 5 volts, so I cannot raise the voltage of the motor without burning the brick. I need a buck converter and another DC ESC that can handle more volts
2nd iteration
wingspan 50 cm weight 80 g including batt (24 g)
No buck converter for the moment. I changed the motor for a brushless 1103  with a 3018 two blade prop
Had to throw in a 12A ESC with a 5V BEC to feed the brick.
Batt is 350 mAh 2S
It's a pitty because I liked the old arrangement of the gearbox. I'll try to go back to it because I guess that a bigger slow rotating propeller will help making it a slow flier, but this is just an intuition.
After the first Flight test
Well, it's got power enough to fly. Climbs with ease.
I had it in the air maybe a full minute before I crashed it into the only rock that was around.
Truth is that I crashed it because of bad piloting. I did not set any low rates nor expo in the TX and the plane was overreacting all the time. I though it wouldn't be so bad with such small control surfaces, but... Maybe the CG was behind where it should be and that's why the plane was so touchy.
At least it flies.
3rd iteration
WingSpan 51 cm Weight 95 g incl batt (24 g)
Surfaces - Wing 500 x 90 mm Tail 140 x 60 mm + 65 x 60
Main Fuselage is a 300 mm rod
New airframe, but it's not that the other one is broken or anything. Easier to make a new one than to disassemble the other.
I have changed the wing supports, so wing now is held in place with elastic bands instead of glued. I hope I don't crash into the same rock again, but if I do, this time I don't want to glue the wings again.
I have abandoned the brick and installed a micro 8 ch RX
I have installed 1,5 g servos that look much stronger than the ones in the brick
I have abandoned the V tail and put a normal elev + rudder instead
I have also installed ailerons in the wings
Power plant, I bought an ESC for a DC motor and a buck converter to feed the RX and the servos so I can have 8V in the motor and not smoke the rest of the gear
I have installed again the Hubsan brushed motor with the gearbox and the 135 mm prop
I have also installed an FPV combo (Eachine TX03)
Batt is 350 mAh 2S
Something strange while testing. It looks like the ESC does not work well. I'd say that the motor goes from zero to full power with nothing in between. It's the first time I install a DC ESC, so I am not sure about it. Also, I am not sure if the prop rotates as fast as it should with a 2S batt, If anybody can give some advice about this ESC I'll be grateful. It's the one in the picture.
I have already seen a couple of things that I'd like to change, like putting the rudder hinge in the same side as the servo and mounting the aileron servos on the top of the wing instead underneath it (i don't know if I'll change that one)
Of course you'll see in the pictures that the wiring is all loose. I will fix it all when I deal with the rest of the issues
And now that's it. No more flight tests until I can get out of my house
On the bright side, last time I went to in the supermaket I found some trays made of black foam that look good for my purposes. On the dark side, they come filled with mushrooms and I have calculated that I need at least five trays to make the wings and the tail and I really don't know if I like mushrooms that much...