RC India

Good afternoon
I got one last depron sheet left before i leave for my college, so i decided to make one more a/c.
I had lots of options, SEPECAT Jaguar, PAK-FA, JSF, etc.
Since i had only one sheet left so i took the safer route and decided to make a F22

Since it is not an exact replica, i am taking the liberty to call it YF-22  :giggle:

The whole project was supposed to start on 18july but i couldnt resist so i started building the a/c my way. I seriously feel that F22 even though is a wonderful a/c to build, it has become quite a cliche, so keeping that thought aside i started building one.

Electronics are the same as always except the motor
Motor : Aeolian C2822-KV1200
ESC   : RCFORALL DY 18 AMP ESC
Battery : RCFORALL 11.1V 1000 mah
Servos 2 nos : RCFORALL DY 0204 : 9 gms

X- Motor mount from RCBazaar.
Prop : 8x6 EF
Depron: 12mm (that i got from Mr Dhiraj)
Adhesive:5min Epoxy and Double sided tape

The major problem i faced last time were the vibrations, so i decided to buy a good motor mount and not make one myself.

waiting for some pictures....

The actual build will start on 17th july, so till then i decided to make a mockup using standard cardboard to decide what to cut and where to cut.

My maxim is not to use plans so i only used the blueprints available online, scaled to my use and drew on cardboard and cut

Pic 1 : Shows the belly of the wing, with the desired position of the prop. The brown tape holds the air intake and the white tape helps me decide the contour of the fueslage.

Pic 2 : Shows the silhouette of the prop, expected CG, side panel of fuselage and the expected height of the motor mount.

Pic 3 : Shows the completed section of the fuselage. The bottom will have an opening for repairs.

Pic 4 : Shows the position of the vertical stabliser.

Pic 5 : Shows the position of all electronics.

Pic 6 : Shows the position of all electronics. another angle, the nose will be made of layers of depron and will support the base of the fuse and maintain proper distance between the wing and bottom of the fuselage.

Pic 7 : Shows the bottom and the open air intakes as opposed to the first design, because a closed intake would become a bluff body.

Pic 8 : Shows the Rear of the the aircraft. It has an opening. The reason for that is that if it had been closed then the air sucked in by the prop though the intakes would get stuck in the closed rear section and would affect the structural integrity of the a/c. The opening can also act as a nozzle and increase the velocity of the air coming out :)

Depron build will be done after 18th July

how did you select his motor
what is he AUG

you need a higher RPM and a small prop

You choice of 1200kv motor and 8x6 prop is not a standard config for a Pusher Jet. Go for a 2200Kv motor with a 6x4 sports prop.
Is that material Biofoam ?

If you have not frozen the plan, I would rather suggest you to religiously follow the F-22 plan by RcPowers.com or  even better http://rc.tomhe.net/f-22

I chose this motor because i have built two a/c having similar dimensions and they have flown very well, another reason i got this motor is because it has greater thrust than the other configuration.

Thank you for the plans, but i'd rather make my own because i enjoy building more than flying.

I do not want to spend anymore on electronics for the time being, thats why i am not changing the motor.

I do intend to buy http://www.rcdhamaka.com/index.php?main_page=product_info&cPath=100_93&products_id=760 that is EMAX CF2805, someday.

I'll still try with the current configuration first. If i run into problems, i will then post and diagnose accordingly.

Weight as of now im not aware because i still need to get the motor and the mount.

what material is this, to me i seems like some kind of hardbord or something like that, i may be wrong.

all the best!!!!

cheers
Ashish

the material is the cheap cardboard. I only used it so that i could make templates for converting to depron. This model is not meant to fly, its only for getting the ratios and the feel of the aircraft and to find the design problems which i may face if i work on depron directly.
The main reason i did this was because i was getting anxious to start but i couldnt start before 18thjuly, and the major problem with such scratch builds is that some problems cant be visualized until they are actually faced with no matter how good one can visualize.

@ashish - thank you sir, i am really gonna need it :) as i always do.

I was having some concerns about the CG of the a/c so i decided to calculate it myself.
Earlier i had assumed it but i wanted to be sure, so i did research and calculated it myself.
As it turns out i was pretty close but not good enough.
Pic "F-22 cg 2": Shows the calculation of the CG.
Now with reference to "Pic 5" I will move everything towards the rear by a few inches to get the CG right.

Hey, using cardboard templates seems like a good idea!

How exactly did you do that? Any set of formulae?

the new cg too is too far forward. cg aft of 20% mid chord is the right place to start with, your nose is too short thats why the problem, should have gone with the janes pic. plan view, all the best, at the outset i can tell you , it may not fly well,  :thumbsup:, prove me wong

How much did the depron cost you per sheet? And what was the shipping cost and time?

Depron were 12mm sheets, quantity 4
Total cost= 880+760(shipping)+30(bank trans. Charges) =1670
I paid on 8thJun, He dispatched on 8thJun and i got it on 13thJun
Dtdc tracking id D05776318

Hmm...that's a bit costly. The base price is okay but the shipping charges seem too much. I'm gonna see if it's available locally.

@augustinev :
Sir i dont want plans, there is no fun for me to build from plans.
Your skepticism fascinates me, now i am all the more excited to do the build (not to prove you wrong), but to see it first hand what the problem looks like.
I am only here to see how and why they fly.
And even if it crashes, i will still have the comfort of saying that i built it.
Thank you for your diagnosis, would you please elaborate the nature of problems i may face.
The only point of worry is that chennai is too windy and not only that there are cross winds and the runway is either too windy or there is flying going on or its night when the flying has stopped.

@Swapnil:
Yes the shipping costs are steep. I tried to ship my own depron from dehradun to chennai once during my semester vacations and the shipping came to Rs.1000. Its all about the volumetric weight.
It is always better to find it locally but dehradun is a dump :), so i hv settled with dhiraj.

Step 1. Extrapolate the leading edge and the trailing edge.
Step 2. Draw the major chord(red)  on either side of the minor chord(green)
Step 3. Draw the minor chord(green)  on either side of the major chord(red)
Step 4. Join the extended chords diagonally
Point of intersection is the MAC
Step 5. Extrapolate the MAC point towards the leading edge
Step 6. take its projection on the center line of the a/c.

Correction : MAC is not a point it is a chord.
Correction : Step six is incorrect

Cool!!!  {:)}
Thanks man!  :thumbsup:
I got a couple of books on aeronautical engg. but never opened them.  >:( ;)

Good Luck with your plane!

Hey, check this out:
http://www.rcindia.org/for-sale/depronbiofoam-for-sale-(5mm-only)/msg32324/#msg32324

At the given rates you could have got your depron sheets for :Rs: 653!

LOL. I also "should" get in the habit of reading books.

foamybuilder is sending by indian postal service. thats why naa (i guess).
What would you prefer indian postal service or dtdc? Its depron what if it gets manhandled?
dtdc can also manhandle it.
Check out
Check reply #17's http://www.rcindia.org/for-sale/depronbiofoam-for-sale-%285mm-only%29/msg32324/#msg32324 pdf
it says Volumetric Weight (in kg) = (Volume in cm3) ÷ 6000

Dtdc also says in http://www.dtdc.in/subpages/services/Volumtric_Weight.html
VOLUMETRIC WEIGHT(AIR) = LENGTH (IN CMS) X WIDTH (IN CMS) X HEIGHT (IN CMS) / 6000

Now all that needs to be done is to tally the postage charges for which i was charged and the postage charge according to the formula

Go through the whole thread, people who bought it seem satisfied...

thats good to know people are satisfied.
Next time i will ask for complete shipping details.

I was just thinking about the validity of the method i just for finding the CG that this method should work for a rectangular wing also.
But if done in a rectangular wing the point of intersection would be the center of the wing which is incorrect.
So i did some more research and found out this
I found out the MAC correctly and did a mistake after that.
The dashed line passing though the MAC is correct "but" its projection on the center line of the a/c was incorrect.
Now what needs to be done is that the CG needs to be around 30% of the MAC line so now, did the necessary corrections.
I am going for a region of 40% to 30% for the cg in my ac.

@augustinev: problem fixed for now
Thank you sir for the heads up.

I was gonna ask you the same thing.
So, for a rectangular wing the CG needs to be around 30% of the MAC line, right?
Is this the standard procedure for all types of wings?

@Swapnil
Yes as it turns out CG needs to be around 30% of the MAC.
This procedure should work for all planforms as it is working for rectangular, trapezium or tapered planforms.
I made an error in terminology earlier "MAC line" is incorrect, MAC is already a line, its the chord, it is just MAC

I returned from Bangalore today evening.
Couldn't resist till morning so i have started building the a/c.
I have changed the proportions just a little bit, increased the wingspan.
Attached are two pics-
Pic 1: Pattern of the parts that can be cut out from this sheet, along with the motor mount. ( the motor mount is kept only for show, its position will be decided after the structure is complete.
Pic 2: Kind of Stencil for the vertical stabilizers. I shall cut them out place them in the fuselage, align them using this stencil and glue them together and remove the stencil gently.

Pic 1:Assembled body, except all electronics.
Pic 2:Electronics bay. The motor and battery will be covered, only the servos will be showing. I could have hidden that in the bay itself, but i wanted to maintain all the weights in a region instead of the line. The cover will rest on bottom of the vertical stabilizers and will be removable for easy access.

I need a sharper blade :P this needs a replacement desperately

Waiting for the stores to open will get the soldering wire and setup the gold connectors.
Pic : Electronics bay.

really nice one!!!! wat thicknees foam hav u used... i think its too thick....... more than 5 mm...

since u have pretty big prop, be sure to care that while landing it should not touch ground, otherwise it will damage ur motor mount support!!!!

@ashJR7202:
Thank you :)
the foam is 12mm thick. when i ordered the foam i was not sure for what thickness would be suitable so i settled for this assuming that it would be the strongest.
the prop sticks out around 3.5inches below the belly, i shall try to be careful in landing it.

Build is complete.
The motor and battery will remain exposed.
I have to do some sanding along the edges
I am thinking of a paint scheme as just a black border along all the edges, and some numbers on the tail.

Now just waiting for the wind to stop, it is VERY windy outside.

completed within a day..omg

hi,

nice effort, but i suggest you see the 6mmflyrc.com for details.

regds


http://www.parkjets.com/f-22-tomhe/

Waiting for the winds to stop, now also waiting for the sun to rise :P
I decided to put some decor on the a/c with my quintessential logo just to pass the time.
The a/c is good to go. i just need to connect those two wires coming on the top of the fuselage.
I also took the liberty of making a facade just under the motor with paper.

Also, it is not a pusher-type model.

As it turns out, i changed the configuration because of which the cg has moved way back because of which i have to put some dreaded balast.
Here's hoping for the best.

There is a thin line between theory and practical.
The theoretical CG i calculated was correct. The practical design which i speculated pushed the CG back making the a/c tail heavy.
Since i made a mock earlier i am glad i only ran into one problem which i think is a bargain atleast for my third build.
If i didnt learn from each build then i wouldnt have anything to build the next time.

I was able to make this a/c from all the remaining depron i had. So now i still have one full depron sheet which is untouched. So i'll make one more, but only after test flying my yf-22.

After reviewing http://www.windfinder.com/forecast/chennai_madras_airport i came to a conclusion that the winds will not calm down anytime soon.
Ergo, i decided to go now.
I already knew that the a/c was too tail heavy so i had made the necessary adjustments before going.
After reaching the field i very cautiously launched the a/c at 75% throttle. It rose, looped at 8ft and then i cut the throttle and crash landed it.
Obviously the culprit was the misaligned CG.
So i returned and decided that instead of adding a ballast i should reposition the battery.
Had a very successful glide test.

I could not sit idle so i decided to film this glide test to check and confirm the CG.

http://www.youtube.com/watch?v=8VgRV-rf6Os

Confirming to ashJR7202's warning and my beginner skills.
I damaged the place where the motor was mounted.
So i shifted the motor above the a/c.

Also the battery's wire is getting loose from inside, which is troublesome and i have to helplessly place the battery on the nose to get the correct CG.

The motor is pulling the a/c but something isnt making sense. Gotta figure something out.
The problem was no matter what i did the a/c was pitching up. But now after shifting the motor up, i think that issue has gone, because earlier the major part of the prop was below the a/c. Now i guess the forces are balancing.

Aesthetics have taken a back seat.
I shall not give up. I have 9more days at home gotta make the best of it.
Can i please get some more blessings here. I could use a little.

I was thinking about what all could be going wrong and i realized one more thing i was doing wrong.
According to me, I strayed from the BASICS. I didnt put airfoils on the aircraft.
So i added a KF-2, with the hope of easing the burden on the motor and control surfaces.

I stayed up all night so that i could go to the field and fly at 0530hrs.

Flight 1 - I launched the a/c and the motor shut off 2feet away.
Flight 2 - I launched the a/c and the motor shut off 2feet away, nose broke
Flight 3 - Fixed the nose, checked the wires for loose connections, launched. The motor seemed to pull the a/c out of my hand but couldnt manage to make it fly.
Flight 4 - The motor seemed to pull the a/c out of my hand but couldnt manage to make it fly. Crashed and broke the nose completely.

Now I will put the motor in place of the cockpit and fix the cg and try again.
I think a 135W motor is under powered by just a fraction, it would have flied if it was a 180 or 200W motor.

Never the less, lets see what happens after replacing the motor

Finally it flew but not for long, a rogue wind came, the a/c nosedived and the motor's shaft broke.
Which scared the bejesus out of me.
So i am closing this chapter on a the following conclusion that it did FLY.
I am still under the trauma of the broken shaft, thank god i had a bad motor whose shaft i replaced, but it was scary.

I am not too excited because
1.there is no video proof that it flew. the a/c didnt come in the camera's field of view  :banghead:
2.Trauma of a broken shaft.

Learnt a lot though and that was the the actual reason for the build so i would call it a success.

Congrats!  :thumbsup: