RC India

Here is my anther coro build.. After success full build of 50" Coro trainer,
This time I Made a pusher One... My own dimensions But Looks from another Small plane from rcgroups..

Electronics used

motor : turnigy 2826 2200kv
prop   :5x5E
Lipo    : 900mah 3s
Esc     : 35A
WS     : 35"
fuse    : Thermocol with tissue covering
Spars   : carbon rod 4mm for tail, 3mm as wing spars

overall weight  350gms
Done glide test, and going to maiden soon...

 {:)} {:)} {:)} {:)} {:)} {:)} {:)} {:)} {:)} {:)} :salute: :salute: :salute: :salute: superb looking bro all the best

arun
nice build, look at basic aerodynamics thread,

line joining Leading to trailing edge is the chord line, you chord line is negative 3-4 deg. she will go nose down badly. you need to rectify that

Thanks yaar actually i need to give some more support to the wings currently working on that..
 :) :) :)

Sir Are you pointing me about the fuse chord is a bit facing upwards?
Done The glide test Right now didn't find any Nose heavy feeling..
I will check it out and Try to adjust thanks for The critics sir.. :)

Added some support for the wings and tail...  8-)
Not its more stable...  ;D ;D

Arun

I think what Gusty sir is trying to explain is that your wing and horizontal stabilizer are not parallel. You have a negative angle of incidence which would give the plane in powered flight a nose-down tendency. Frankly I can not make out from the pictures, but look at it from the back with one eye, model as far away as you can hold, and from side-on. If this condition exists, you would be well advised to correct before flying.

That's my 2 cents worth!  :discuss:

Nonetheless,  :goodjob:

Sir as I am using  CF tube as the fuselage when i place it in ground the cf tube will twist a bit with the weight of the wings and thats what happend in that picture..  But when i keep it in hand the wing is parallel to the tail.. >:( >:(
Anyway i am gonna fly it... :( afetr the support the wings are much stable now...

Good Luck, all the best. Looking forward to the video

Thanks a lot sanjay sir Its really windy here in kerala,
Dont know will update soon after the maiden..  :thumbsup:

This is what i meant by wing is sitting at -ve incidence, though it might appear that the wing is straight, it is not, because the chord line along which the lift will act is a line joining the LE radius to TE radius. See image. like i said read further on Basic AD thread

See image

another question

is she balancing at 25% chord?, to me it appears all your mass appear to lie behind 25% and not much really ahead. not to mention the Tail Volume.

Sir I got you now  :)
After the installation of extra support the wings are more straight now..
But sir i am getting CG about 30%-35% chord and i have added the lipo in the very nose part to get good balance and as it is about +50gms weight... :)
My intention was to Add some weight in the nose after the glide test but the glide test went fine as i never expect..  :giggle:

Use Single coro technic for the wing stated earlier by me with the jointing procedure.
(http://www.rcindia.org/electric-planes/coro-wing-design-new-try/?action=dlattach;attach=649221;image)
If you are making it as puller (Rudder and elevator as nose and wing at back), then the wing produce lift, else when the plane forwards, it will move the air upward and it just go downward. Else to produce lift, you have to give elevator trim and it will fly like hovering. ;D

Here is the thread
http://www.rcindia.org/electric-planes/coro-wing-design-new-try/

Please please read the basic aerodynamics thread as adviced to save costly electronics.
Commercial airplanes are tilted 5-15 ^O maximum. So, it will look odd.

Kalyan Da, the process is very elegant but that is too cambered. It will create more drag, it will cause the flow to separate downstream and since the leading edge is sharp(unlike an actual airfoil), it may also cause leading edge flow separation.

At very high speed and at high angle of attack, the sharp edge will generate vortices producing lift even at those extreme angles(that is fighter planes have sharp leading edges). But at low speed, a smooth airfoil will give better results.

Arun, you should follow rcpilotacro's suggestions. That leading edge looks more like a leading edge flap in this configuration.

@kalyan sir: Sir saw your design, will make another wing like your's...
Thanks for your help..  :)

Sir actually i have rectified the Chord line already as rcpilotacro sir, But decided to make a new wing as of kalyan sir's design, It looks more good for me too now.. It was build just for a fun two days before...
I would have maiden but it was too windy here which saved my electronics.. :)
Thanks for your help rohith sir

hello Kalyan ji,

I understood the technique to bend coro.... what should be the ideal under-cambered wing aerofoil shape.....is it similar to the aerofoils ---- upper surface only... and what should be the angle of incidence.
 
Is the attached image fine...

The single coro wing will be equivalent with the flat bottom wing with the top simulated as shown in the picture, just with some less drag and less strength, less weight. Moreover, the sharp square leading edge sometimes starts flapping and so the leading edge is to be rounded with clear tape(or any other method). I made 24" wingspan 400Gm AUW with 1/2" folded to achieve rounded leading edge and flies grate.

Only a THIN AIRFOIL can be considered equivalent to its camber line and infact this is what is done in the Thin Airfoil Theory to calculate the lift and other airfoil parameters. However, thick airfoils cannot be replaced by camber lines.

But the thin airfoil theory does not take into account the viscosity of the fluid and hence does not predict flow separation. Also a camber line airfoil will produce lower lift than its equivalent airfoil.

Take an example of a symmetric airfoil whose camber line is straight line, now look at the lift vs angle of attack values for a flat plate, then look at the lift vs angle of attack of the symmetric airfoil(in this case the NACA 0012). You can clearly see that the flat plate gives a maximum Cl of about 0.7 whereas the symmetric airfoil gives you about 1.2. Also the flat plate starts stalling at about 8 degrees angle of attack whereas the airfoil goes upto about 11 degrees.

Therefore, since the flow begins to separate earlier for the flat plate, it is going produce much MORE DRAG than its equivalent airfoil(at zero angle of attack though, the flat plate will have lower drag).

Therefore IMHO, a camber line is never an equivalent of the corresponding airfoil, it is always better to have an airfoil otherwise we would be seeing camber lines in all the planes around us.

Hello rohit,

Understood the point you made... can you give an ideal ( practical) under-cambered aero foil for a slow fly plane and top view of wing.

Well, a clark y airfoil(google it!) is always a safe bet. It has very good performance at the Re at which model aircrafts fly. So you can use that. If you want to build a slow flying plane, then you should have wings with AR(wingspan/chord) about 8-15. The larger the AR the better(look at pictures of glider wings and you will understand).

Also try to keep the wing loading(Weight of the airplane/wing area) low for better glide performance and to have a lower stall speed so that you can fly at lower speeds without stalling.

Then the AR of the horizontal tail should be around 3-4(always keep it less than the wing), lower aspect ratio wings stall at higher angle of attacks. Hence even if your wing stalls, you will still have control of the tail. There are lots of details that follow, one needs to read a lot.(Ofcourse it was easy for me, because I had taken Airplane performance and design in my previous semester. :D)

here is the Clark y aeroplane

http://www.rcindia.org/gas-glow-nitro-planes/50cy-scratch-built-50-cc-high-winger/


read this too

http://www.rcindia.org/rc-general-topics/basic-aerodynamics-for-rc-flying/msg115570/#msg115570

Reylonds Number (http://en.wikipedia.org/wiki/Reynolds_number)

AR=Aspect Ratio= span/mean chord  or span²/wing area

read http://en.wikipedia.org/wiki/Aspect_ratio_(wing) (http://en.wikipedia.org/wiki/Aspect_ratio_(wing))


Rohit  KISS ;D


http://en.wikipedia.org/wiki/KISS_principle

Thanks rohit for the explanation.

The data and the graph as actual. From your wind tunnel experiment surely.

Too much of homework by teacher's........
well as a good student I will read and then ask questions.....

But clark y aerofoil is not under camered or just eleminating bottom makes is do the job. I thought an under chambered wing gives slow speed .

No KalyanDa, the first graph is from the book of Anderson, second one I googled. we haven't tested flat plates, however I have written Matlab codes for the pressure distribution around many airfoils(including flat plate) but to save time I googled those graphs.


This is not true. First of all building an undercambered airfoil will be more difficult than building a flat bottomed airfoil, secondly how fast your plane flies depends on how much thrust(i.e the power system) you apply not the airfoil. I mean, if I were to attach a Rolls Royce turbojet engine( ok its way too exaggerated  :giggle: :giggle: but bear with me) to your model plane, then will it matter, what airfoil you put? That plane is going to shoot past you. The undercambered airfoil will have more drag but that doesn't necessarily mean slow speed!

Ok, I must now stop, otherwise I might overcomplicate things and unnecessarily bombard you with too much information which would infuriate our aerodynamics guru rcpilotacro.  :giggle: I therefore request rcpilotacro to take charge from here. I must guide you to his aerodynamics thread which, I feel, you should go through. Here it is : http://www.rcindia.org/rc-general-topics/basic-aerodynamics-for-rc-flying/

I get what u say but ideally if I have 2 planes with same engine same wing span same chord but one Clark y with flat and one under cambered then what will be difference in flight. Simple question.

Hmm. The undercambered airfoil will produce more lift than the clark y airfoil but it will stall faster than the other one.