RC India

Here's my first scratch-built bird.

It's a single-aileron coro.
It turned out to be much heavier than was planned; couldn't take-off. Gonna reduce the weight and try again.
 
The hinges were made using gell-refills and metal strings. I tried using plastic and tape hinges on prototype wings, but wasn't too happy with their working.   

I would greatly appreciate suggestions for rectifying/modifying dimensions & weight.

Dimensions :::

Chord: 9
Span : 36
Aileron : 17X2.25
Elevator: 11x2.5
CG: 2.7 behind leading-edge

Power setup:::

BLDC: A2836-8
ESC : 30A
prop: 10x5E
LiPo: 3S, 1000mAH, 22C
3 x Power HD Servos (HD-1900A)
 
Building materials:::

Wings: 4mm coroplast (+ kebab sticks)
Fuselage stick: wood (1486mm x 30mm X 6mm)
Motor-mount: aluminium (2mm)
hinges : empty gell refills + steel threads

Pics...

nice build swapnil,do you maiden it yet?

Sorry, no maiden yet.
I'm reducing its weight right now. It gathers enough speed after a 4 metre run but doesn't take-off. If weight reduction doesn't work, I'm gonna try converting the flat-wing to a flat-bottom airfoil.
 

i had tried the same type of plane which is my first plane,had same experience but it never take off,stopped it right there and tried other plane,then the blu baby(i had some problems with foam wing),then now trying moss,all i want to say is never ever give up,keep trying and keep the spirit,make sure the c.g is correct and when you test glide it,it should glide smoothly which mean that your plane is ready to fly,all the best  :thumbsup:

Harsha, I'm not gonna give up on it and start with another plane. Thanks for your suggestions. I'll surely test-glide it first when I'm done modifying it.

 

Here are the vids of aileron and elevator throws. Is the mechanism for aileron movement effective? I've not seen something like this in any of the 'scratchbuilt' threads I've been through so far. Waiting for comments from seniors on this.



http://www.youtube.com/watch?v=uXBwtNpe-CI




http://www.youtube.com/watch?v=D5OVKUGtmDc

What is the all up weight? Also could not see the horizontal fin. just photo missing or what?

Yep, where is the vertical fin/stabilizer ?  That would be a key factor for the stability of a model with this type of design.

@Pankaj: AUW is more than what was desired. Reducing it right now...


The vertical stab will be added soon, the bird's still in its construction phase. I'm currently working on reducing the AUW. (Wonder if I should put it on a diet :P )

Anwar sir, I'm using a single aileron as it is easier with the type of hinge I'm using (Also, www.foamflyer.info has loads of planes with single ailerons). Should I have gone with the regular twin ailerons?   
 

IMHO, with the span and chord being 36 x 9, anything above 600gms all up would not be suitable for a newbie as it would result in a high wing loading and thereby increasing the stall speed

Whats that going through the tail wing does`nt look like servo, is it an LED ??

Are you referring to the tail-wing in the video or in the pic?
Either way, it's not an LED, I haven't used one. I think you saw a bolt tip...  ???

Preferably, remove all landing gear, its just useless weight when the plane is in the air. Also, the fuse can be thinner (is it plywood?) Could try out thin frame sticks from a picture framing shop. Remove all bolts and simply use rubber bands with double sided tape or plastic ties or to hold the servos.

The wings seem to be drooping in one of pics, will be good to include some dihedral.

Hmm.. can't do without a landing gear. Even though it's useless in air, I'd rather damage a couple of wheels than a prop or wing. Gonna remove as many nut-bolts as possible and use tape, hot-glue, cable-ties etc. Thanks for the tips! :) 


The pics were taken with the reinforcements removed. The wing gets a curved dihedral (like that in an Easystar) with 0.5mm steel fibres in the flutes.

The plane was tail-heavy. Moved the main wing 1.5 in behind original leading edge. Also reduced the fuselage-tail area by half.

Built a new landing gear. It's a lot lighter than the previous one, though not as sturdy...

Swapnil, please check this out first.

Sir, I replied to that in #16...

hi,

Just sharing my experience with 4mm CORO, although being a new bee.

First i tried to make a UC wing but the wing got twisted due to leading edge folding
- First time wing folden
- second time , went to right without any of my control...broke everything.

Second , Tried to make a MOSS . it flew but it was very fast and every landing i would break the prop or motor mount

Last : Bought a GWS beaver... Nice docile .

So my advise for making coro plan on flat wing would be to go for Extra 300 ,  there was a very recent post on the same.

from where did u buy the beaver ?

Modified the tail-gear....
It's much lighter now.  ;D

Changed the fuselage-stick. New one has half the area and weight.
Removed most of the nut-bolts.

Wonder if I should remove the tail-gear completely.  ???

Added flat-bottom thermo aerofoil to the flat coro wing. Also, the wing now has a 3^o dihedral.

And now it's a high wing too!

What is the current weight of the a/c?

It must be around 800 gm or less...

you still need to lose weight i guess. Because i also tried to make a coro a/c one it had no extra parts to it, not even wheels still it didnt fly, but again the thrust to weight ratio was bad, i really suggest you find out the thrust to weight ratio. Because of the motor setup i have i know that the assembly alone doesnt have a 1:1 thrust to weight ratio. Thats why i used depron and "airfoil".

Check out http://www.rcgroups.com/forums/showthread.php?t=1377724 for a discussion on Flat Wing Aerodynamics vs Airfoil

Power to weight ratio = 243/1.76 = 138 Watts per pound.

Thanks for the link!

According to one of the people i discussed this matter (long time back) 138W per pound is comfortable.
Also find out the wing loading using this http://adamone.rchomepage.com/design.htm
And compare with http://en.wikipedia.org/wiki/Wing_loading (you'll have to change the units)
What values come?

Attached pic of the wing loading (weight taken as 700g).

The cubic loading comes out to be 8.73 oz/cu.ft. And the range for  trainer/ sport type models given on the website is 7 to 9 oz/cu.ft.

Thanks for the links again!  :thumbsup:

here's the wing loading data...

Hi swapnil!

Great Build! isn't the airfoil too flat in the front??? I think it could be rounded a lil more??

I know, but the the airfoil base is made of coro and can't be rounded. Also, it's a close-up shot, it looks O.K in real.

 :salute: :salute: all the best for the flight! 

Happy Landings!  :)

Thanks!
It's rainy/ windy here all the time these days. Hope to maiden it soon.
And thanks for the advice, I'm not much into maths or deep-study of aircrafts.
Just wanna fly! :)

hey swapnil. I just remembered a great idea, which i used to do. It really helps.
Remove the break-able parts of the a/c, replace with equivalent weights, now if u want to find something of the equivalent weight, use a 30cm ruler, place your known weight on one side and a dead weight on the other, and try to balance everything keeping 15cm as the pivot. u can use cells, tubes or anything as dead weights.
Now strap all the dead weight on the 1/3 line and launch it (gently). u can tape the elevators up a bit, and its your choice where u want to land it, ground, grass or any person's hands.
This will accomplish one very important thing if the battery fails, will the a/c land safely or will it fall like stone. You will also be able to see how the airfoil effects the flight.

Really good idea, will certainly try it. Can't do it right now as I don't have enough space indoors and everything's wet outside.
Thanks and keep the tips coming!  :)