RC India

Now that the sweepstakes fever is over, thought i'd complete a project started for last year's sweepstakes:

The story started here last year:
 http://www.rcindia.org/electric-planes/5th-sweepstakes-sunbird-adiboy/msg178569/#msg178569

The tail feathers were easy, fuselage not too hard.
But the wing?
All i can say is that if you went by the so called instructions, you would NOT end up with wings!

Here are some pics:

The wing area is a little over 2.5sqft.
Would you believe the weight after. 2 coats of Wonderwood on the fuselage?
Wing loading is going to be under 6oz/sqft
As compared to nearly 16oz/sqft for my similar size Pilatus B4
Hope to fly both tomorrow to compare...

Superb build sir looks like the bird of time glider, hope she sails as magnificently as her too. :thumbsup:

Which one should i fly tomorrow? :headscratch:
They are about the same size, but one is 360gms, the other >960gms...

That is so beautiful!

 {:)} {:)} {:)}
waiting for flight video Iyer Sir.

-learner

But how come so much difference in weight iyer sir...

Pretty birds sir  :salute:

All the best for the maidens

Beautiful Bird Sir  {:)} {:)}

Great Job  :thumbsup: :thumbsup:

Thanks Tarneil, Ashwin, learner, Nirmal, Rai saheb and Col.

Must shamefacedly admit to the following mistakes:
1. In my hurry, forgot that the fin/rudder had just been pressed into place, but had not been glued
2. As usual for my maidens, it was tail heavy
3. As usual for my maidens, it was underpowered, due to habit of not using full throttle..
 :banghead: :banghead: :banghead:

Result - after hand launch, she climbed with great difficulty, right into the power lines.

Lesson: Cheap ply dihedral brace is useless. Replaced with hardwood (window baton)

Perhaps not having your regular buddy adds to mistakes. With my dad on 24hours oxygen now, either I or RC Aunt have to be at home if the other is away. So golf nearly shut down, not enough motivation to go so far alone. RC down to about once a month or so.
But
Only 3 more days till Sunday. Hope maid agrees to stay for 2 hours...

woww.. superb build Iyer sir  {:)} {:)} {:)}  :hatsoff:

Iyyer Sir, if you are in a hurry to maiden that beautiful bird early, we can meet up.Will have company.
Im planning to fly this Saturday too...early morning(Sunday flying as usual). Let me know if that suits you...would be treat watching it fly!!

Here's a short video, of a home landing.
https://m.youtube.com/watch?v=E13LZBCEe6I

Inspired by posts of dhruvafreak and bmblb...

A home landing is some thing cherished by glider pilots, as it is the last flight of the day, and you can roll right up to the hangar after landing...

(Any IITK guys listening?)
Those who soloed on VT-GDD (Schweizer 2-22) and then progressed to VT-GDE (Schweizer 1-26) under Capt V V Nanda, Sanjay Atrishi, Rakesh Rastogi or Umesh Chandra in the late 70s- early 80s...

 .....so graceful......and what an enviable place to fly  ;D

Very nice, sir  {:)} {:)}

Now I must build a power glider. Corro, 60" + + span  >:D

Nice build sir

@bhanu Prakash,
Hum to aapka pinewood Cessna build dekh rahe the.
Aapko ye thread Kaise mila?
Regards.

Excellent build iyer sir :salute: :salute: :salute:

Forgot to upload video of flights after trimming completion.
Strong left roll corrected partially by removing (nearly imperceptible) warp in left wing, and by adding a small trim tab (1"x2"x1/4" depron). (No ailerons, only rudder, elevator, throttle)
Had looping tendency at over half throttle despite 2 washers downthrust.
Moved cg back gradually to remove up trim in elevator.
Was not enough.
Finally solved by mixing 5% down elevator into throttle!
(Had 10% initially, but that pulled the model down on launch...)

See if you can spot where i cut throttle (at about 22 seconds).
How high? 200-250 ft?
Thereafter in lift!

www.youtube.com/watch?v=C96oiT0ndgE

Here is a pic of the wing joiner/ dihedral brace to make the wing two piece to fit in a small car.

Sir, how do you ensure that the joiners don't slip out during fight? Is there some sort of locking mechanism inside?

@intorc,
There's no force pulling the wing halves apart in normal flight.
So the rubber bands that hold the wing to the fuselage are enough to hold both halves together.

May be a silly question but does it also apply in swept wings too?

 air to wings friction pulls wings back if you use the common spar perpendicular to cetre line
then there might be no problem.

Iyer Sir....you have just the right place to SLOPE !!! overlooking your flying field !

need I say more ! ;D

Unless its a jet, i expect a cellotape on the wing joint would be enough.
In olden times, we used to stick a pin into the top spar of each wing, and connect with a small rubber band...

There is an ongoing discussion in RC Groups about the power needs of the Sunbird.
Copying my today's RCG post here, as may interest RCI members building a Sunbird.
(Pics/video excluded as already available in this thread)

How much power for Sunbird...
Hi,
I thought my Sunbird was pretty. Till I saw the others in this thread.

Mine is 450gms/16oz. Rudder, elevator, throttle. No ailerons.
Two piece wing with 6" hardwood dihedral brace/joiner.
Has an Emax 2805 with a 5-6" prop label, indicating it is 2840kv.
However, must be a 1600kv, as near full throttle (fearfully reaching 150+ watts) indicated 15000+ rpm on 3s and a 6x3 prop that has an HY logo.

Soldered parallel JST and XT60 connectors to ESC, to enable use of 2&3 cell.
Used a 1000mah 3s to avoid tail heaviness.
Balances at spar, about 40-45mm from LE.

Easy take off at half throttle. About 50- 60watts. 9-10,000rpm.
Or about 50 fps.
Above half throttle, a tendency to loop!
Corrected presently by mixing 5% down elevator into top half of throttle range!
Bet no one tried that before

So the lessons i learnt:
1. 60watts is enough for a nice climb
2. CG could be moved aft 10-20mm behind spar (and decalage reduced, and down elevator mixing to throttle removed). Will try on Sunday if weather permits.

Here's a pic, and a brief video. See if you can spot power cut at about 22 seconds, rest in lift!

Here's a pic and the video anyway, to save you the trouble of going back to page 1  ;D

https://m.youtube.com/watch?v=C96oiT0ndgE

450 gms at that wingspan  {:)} {:)}. Awesome build sir. Looking beautiful. Must surely be a pleasure to fly. The shape of the Wing always deterred me from getting one for me. Wondering no build issues you encountered.

Great stuff, Iyer saheb


Now you know who inspired the Fournier ;)

Haven't come across anyone in RCI flying the Hobbyking Sunbird, so most of my posts on the subject have been on RCG!

In case there is someone here flying a Sunbird, he/(she) may find this useful  ;D

Since there is no instructions booklet, just some pictures, CG location has to be guessed at.
So far I'd been flying with CG 45mm from LE (just ahead of spar)
Following inputs in RCG, moved CG back to 55mm this Sunday.
The improvement is amazing.
No more tendency to drop nose in turns. Absolutely flat glide hands off and power off.
So nice that RC Aunt (who hadn't flown RC in over a year), snatched the Tx from me!
Till I snatched it back after 8 minutes!
The video is however only 30seconds, ended by our dog who considers the iPad a competitor for attention, and so hates it...
https://m.youtube.com/watch?v=D0u9BclArQE

Sunbird with GPS and altimeter. No audio vario though...

Tomorrow, hope to get data on
1. Altitude
2. Upwind/ downwind ground speed via GPS

Results from last Sunday:

Well, there's some good news, and some bad.

The good news is that the altimeter showed that reaching 400ft is easy.

Now the bad news.
1. Flying the model, and reading the data display can't go together.
I'm 63, wear -7 glasses and bifocals. Once I focus on the display, i lose sight of the model completely. Needed shouts from wife and friends to locate it again...

2. Ground speed as per GPS varied from 46 to 72kmph. Didn't sound right...

3. Had a temp sensor, so taped it to the ESC (12a, 1a BEC). Noticed the temp display climbing rapidly. At 57 deg C (ambient 28C) I decided to land urgently. Found that the ESC's plastic wrapping had melted and peeled off...

4. Removed all sensors and hub. Had no difficulty flying. No heating, nothing.

The question now is:
How much power are the hub and 3 sensors drawing? (GPS, Alt, Temp). Are they (and 2 x 9gm servos) cooking the 1a BEC? Rx voltage even showed 4.9 instead of the usual 5.0!

Lessons learnt:
1. Need separate power supply for hub/sensors
2. Need full time copilot to monitor display (and toggle between 3 screens) to get any useful data

Regards

Edit: meanwhile waiting for sanjayrai55's Griffin to be completed... ;D

Iyer sir, you are much more than 63 ;)  Wisdom of a 100 and that stuff

It has been so long since I flew an Orange Box (nearest approximation to the Griffin I can think) that I have quite forgotten what one is supposed to do  ;D

Decided to fly the Sunbird, the only fixed wing airplane I registered with Dgca.

Mostly flown by RC Aunt.

Today she said she can hear a sound.
Which wasn’t there before.

Checked that prop is balanced. It was.
Removed the motor, washed it in water, dried it and oiled it.

I guess the front bearing is suffering from dust intake.

I think it’s time to replace the bearings. Has had 50 or more flights.

Can someone please tell me what size the bearings on an eMax2805 are, and where to get them?

Miniature bearings are difficult to get. Nagdevi Street in Bombay is the only one I know of; you would need to take the sample. Or if you know ID/OD/Height and type of bearing (eg Single Race, one side metal shield) you can cross-reference

Much easier to replace the motor!

In most cases a good cleaning and oiling works for unshielded bearings

If you let me know ID/OD/Height I might have lying around. I got some assorted sizes a few years ago

I remember my first scratch built. It was a fusion of the flight test tiny trainer (940mm wing span) and an avispad (ruggedness) with an aspect ratio of 5:1 chord:span. The final AUW of the plane was/is 780-90 grams. Had real trouble flying it , broke around 10-15 props until I could fly it for at least 3-4 minutes at full throttle and as a cherry topping, the airfoil turned out to be a symmetrical one (the boons of using corro) although I wanted it to be a clark y. I still use that wing on a much lighter fuse, goes vertical at times ;). The thing learnt : wing loading/CWL matters a lot. 450 grams for sunbird is just awesome. Bearing could be greased and you may find bearings of coaxial helicopters at novelty bazar in Indore, not sure about the sizes though.
 
last time I flew it by using a 1000mah 3s lipo and that old wing with the yellow fuselage. the flight time was very low and the battery felt like jelly after the flight.