RC India

Hi guys, posting the funjet build thread after a long time of inactivity.
Unfortunately i lost my cell phone with all the build pics on it but still will be posting whatever is left over on my laptop.

For this build i will be using-
- CA 793
- 5 min Epoxy
- SK3 1900kv EDF Inrunner Motor
- 200A HK SS series ESC
- Castel 10A Bec
- Turnigy tgy-90s Mg servos x2
- 6x6 Gemfan (Graupner cam speed 7x7 upgrade later)
- 1300mah 45C 6s x2 Lipo

NOTE :
-For the sk3 motor, the prop bore diameter and to be increased to 6mm (Except cam prop).
-Center the servos before installation.



Build is straight forward.
(http://i1274.photobucket.com/albums/y438/dhruvafreak/Mobile%20Uploads/20150802_14212101_zpslmbyaddx.jpg) (http://s1274.photobucket.com/user/dhruvafreak/media/Mobile%20Uploads/20150802_14212101_zpslmbyaddx.jpg.html)
(http://i1274.photobucket.com/albums/y438/dhruvafreak/Mobile%20Uploads/20150802_15363901_zpsav5qss2c.jpg) (http://s1274.photobucket.com/user/dhruvafreak/media/Mobile%20Uploads/20150802_15363901_zpsav5qss2c.jpg.html)



Servo Mounting:
The mounting gap needs to be incresed for these 90s servos and can be done easily using surgical knife.
Since it's a tight fit for the servos, i have only used .2-.3mm double sided tape for installation.
(http://i1274.photobucket.com/albums/y438/dhruvafreak/Mobile%20Uploads/20150802_15171201_zpsxsfxhsod.jpg) (http://s1274.photobucket.com/user/dhruvafreak/media/Mobile%20Uploads/20150802_15171201_zpsxsfxhsod.jpg.html)



Extra Intake :
During the static thrust and electronics check up procedure i found that the esc and could touch 70C easily so thought
of adding extra air intake vent for cooler system.
Intake is just above the Esc mounting location which is just under the carbon rod.
(http://i1274.photobucket.com/albums/y438/dhruvafreak/Mobile%20Uploads/20150802_153731_zps3k4rhwpf.jpg) (http://s1274.photobucket.com/user/dhruvafreak/media/Mobile%20Uploads/20150802_153731_zps3k4rhwpf.jpg.html)
(http://i1274.photobucket.com/albums/y438/dhruvafreak/Mobile%20Uploads/20150802_153800_zpsurvogrct.jpg) (http://s1274.photobucket.com/user/dhruvafreak/media/Mobile%20Uploads/20150802_153800_zpsurvogrct.jpg.html)
(http://i1274.photobucket.com/albums/y438/dhruvafreak/Mobile%20Uploads/20150802_155754_zpswpepojln.jpg) (http://s1274.photobucket.com/user/dhruvafreak/media/Mobile%20Uploads/20150802_155754_zpswpepojln.jpg.html)



Motor Mount:
Used the stock motor mount but extra 2 holes required for the motor mounting which is done using dremel.

More:
-The full kit was sanded and will be glassed in later stages along with custom vinyls.
-The gap between the carbon rod was filled with epoxy and all the joints were assembled using CA793.
-Couldn't get a metal Motor mount so shall be running the stock one and later CNC mount will be made.
-The front canopy hatch has to be sanded from underneath .7cm for battery placement. CG is proper with both batteries pushed in front.

And now the maiden flight preparation.
I'm using stock vinyl for maiden but will be changed to something more visible in sky.

(http://i1274.photobucket.com/albums/y438/dhruvafreak/20151122_121609_zpsdqly5vgy.jpg) (http://s1274.photobucket.com/user/dhruvafreak/media/20151122_121609_zpsdqly5vgy.jpg.html)






I was slightly nervous about the takeoff. Worrying about the torque roll and take off throttle.
Did a 100% throttle take off with more then 100 degree torque roll.
Anjan Babu a forum member also my roommate helped me in getting the bird in air and as well in building the aircraft.



(http://i1274.photobucket.com/albums/y438/dhruvafreak/vlcsnap-2015-11-22-13h57m13s353_zps96ges9ea.jpg) (http://s1274.photobucket.com/user/dhruvafreak/media/vlcsnap-2015-11-22-13h57m13s353_zps96ges9ea.jpg.html)

(http://i1274.photobucket.com/albums/y438/dhruvafreak/vlcsnap-2015-11-22-13h57m48s773_zpsxiirgoqk.jpg) (http://s1274.photobucket.com/user/dhruvafreak/media/vlcsnap-2015-11-22-13h57m48s773_zpsxiirgoqk.jpg.html)

(http://i1274.photobucket.com/albums/y438/dhruvafreak/vlcsnap-2015-11-22-13h57m57s982_zps3feyjeq1.jpg) (http://s1274.photobucket.com/user/dhruvafreak/media/vlcsnap-2015-11-22-13h57m57s982_zps3feyjeq1.jpg.html)

The maiden video
Almost crashed and did touch down pretty hard
 www.youtu.be/WdikyhCV8d0

Its crazy . . . Couldn't find your plane in the sky

Great save on launch!  {:)}

Dhruva
Try launching with 1/2 throttle open and gradually increase to full and you won't have to deal with so much torque coming in suddenly.
Or throw out the electric  and Switch to turbine - no torque Only thrust !
Then you'll be looking at a real 300KMPH
 ;D

@Satz_flying yes agreed ! I did the second flight and recorded on 4K. 2nd video visibility is amazing if seen on 4K :D

@K K Iyer Thanks sir. That was the most luckiest pull for me :D

@Xantos sir,  Yes sir i did the same on the second flight since i could predict the aircraft. Did the second flight with more alpha chuck and 40% throttle. Still was a rocket. Turbine for sure. Maybe in next few years.

I couldn't give more then 50% on the maiden but on the second flight i did give 100% for few seconds  This one is insane but I get continous turque roll as i increase the throttle. I assume i have to crosscheck the left or right thrust angle.

www.youtu.be/hUgW6V9q3T4

Fantastic! Even without fan.
Looks much better without black tape on nose, and with orange on wing upper.
Wait till Gusty sir sees this video...
We have an edf like this here, but it doesn't seem so fast...

Nice Very Nice ....
Almost like bullet...

What is the orange covering you have done... is it monokote? or vinyl?

@Kk Iyer - Yes sir and the bottom side covered with bright green. Not shown in the picture but in video can be seen.

@rastsaurabh - Thank you :) . Its vinyl.

Well saw your launch of the model.... guess the roll to the left is not just because of the torque but also the way you are throwing it.  The way you are holding leaves very little place for a firm hold to throw the model correctly i.e wit wings level.  Loot at my video of launching a Vortex RC Speedster.  The model is overpowered and flies like a rocket.  Yes all take offs will be at high power settings throttle because this is how you go up and away from the ground in an instant.  My advice an a seasoned aviator is never take off with less power and as far as possible use 100%.  There are more advantages of using 100% power than the disadvantages.
https://www.youtube.com/watch?v=IJg7O9EqFcY

Shobit17, the cause for the left roll is purely anti-torque generated by the motor. I know that because, I couldn't resist the torque roll holding the plane with both my hands while shooting up from just 0-10% throttle. 

I partially agree with what you have to say about the way I was holding the plane, then again, that's where and how you should hold a narrow rounded fuse weighing in at 1.3kg with 50/50 weight distribution. ;D

Completely disagree with your claim that all take-offs should be at full throttle, didn't expect that from a seasoned aviator. Technically, planes go up and away at minimum take-off speeds.

Maybe not much of a rocket, but that thing flew like a blazing rock out from space. ;)

Thanks for the suggestion Shobhit sir, however i wouldn't agree on 100% throttle for takeoff.

Since I'm Pursuing my Aerospace Engineering and i have come across Adverse Yaw condition which acts because of Spiral propwash generated by single engine prop planes.
It causes yaw when they are flown at high power and low speed (takeoff and climbout, for example.) The prop doesn't blow the air straight back, but gives it a bit of a twirl which causes yaw.

And difference in profile drag between the upward and downward deflected ailerons which in case of countering the torque is applied , the difference in lift and thus induced drag between left and right wings which tends to yaw the aircraft in the opposite direction of a roll.

So because of these two reasons the aircraft might just yaw severely under full power and while countering the torque.

I have learned this very hard way while building and testing a Model(.35kg) made to carry payload (1.5kg). I have tried full throttle and have seen the yaw conditions i stated and crashed.

Dear Mr Anjan and Dhruva you may be experts in the fields on which you are commenting.... I am no one to force my advice on you.  Please go ahead and do what you been doing..  

Talking of adverse alieron you... the situation when the adverse alieron yaw develops in an aircraft is absolutely different and not what you are talking off.... You may like to read the highlighted portion in the Lift Coefficient heading.  Thats why it becomes more improtant that your model exits the slow speed regime at the earliest a


For your information please go to wikipedia for adverse alieron you and will find this..........:

Minimizing the adverse yaw
There are a number of aircraft design characteristics which can be used to reduce adverse yaw to ease the pilot workload:

Aileron to rudder mixing
As intended, the rudder is the most powerful and efficient means of managing yaw but mechanically coupling it to the ailerons is impractical. Electronic coupling is commonplace in fly-by-wire aircraft.

Lift coefficient
As the tilting of the left/right lift vectors is the major cause to adverse yaw, an important parameter is the magnitude of these lift vectors, or the aircraft's lift coefficient to be more specific. Flight at low lift coefficient (or high speed compared to minimum speed) produces less adverse yaw.[1]:365

Yaw stability
A strong directional stability is the first way to reduce adverse yaw.[6] This is influenced by the vertical tail moment (area and lever arm about gravity center).

Differential aileron deflection

Illustration of a Differential aileron
The geometry of most aileron linkages can be configured so as to bias the travel further upward than downward. By excessively deflecting the upward aileron, profile drag is increased rather than reduced and separation drag further aids in producing drag on the inside wing, producing a yaw force in the direction of the turn. Though not as efficient as rudder mixing, aileron differential is very easy to implement on almost any airplane and offers the significant advantage of reducing the tendency for the wing to stall at the tip first by limiting the downward aileron deflection and its associated effective increase in angle of attack.

Most airplanes use this method of adverse yaw mitigation due to the simple implementation and safety benefits.

Please check the last three take off pics posted in Reply #1, they're self-explainitary. I don't understand how you could get torque rolls wrong.
BTW, that plane torque rolls in mid air at full throttle and 50% throttle is still a bit much to take off I guess.

god helps you dear Ajnan.... go and do what you feel like....

Thats off topic. Stick to torque rolls.

I don't know why you are offended SIR but i just shared knowledge what i was facing.  :headscratch:

I have been to the wiki page about idk how many times.

And You didn't see yaw because its a pusher model and the wash is not hitting the vertical fins and its 50% throttle . I can do a vertical takeoff with 40%.  :thumbsup:

The model has thrust to wieght ratio is greater then 1 so its practically impossible to hold during hand launch.

Keeping 100% throttle , I'll definitely have max torque during launch since there's no airflow to counter the torque.  :hatsoff:

......Guys.....this is a killer  >:D

 would love to see it being flown by you guys  :thumbsup:

@Bmblb thank you.
Would definitely get to hoskote to fly it. :hatsoff:

well.... I never said that you can not do a takeoff with less than 100% power.  You do not need an airflow to counter it.... you got those two big vertical stabs on your wing to counter any unwarranted instability........... even my model can take off with 50% throttle and it jumps off my hand at full throttle.... it does not mean that 50% throttle is enough for takeoff.....  

Anyway... as i said earlier... I was talking of what is done best to maintain a good quick take off and an early exit from dangerous flight regimes....... if you can manage it at low throttle go ahead and do it... but next time do not blame me for a crash due to compounded effect of torque roll and a tip stall..... and maybe many more thinks like winds compounding the problems on your take off.....

Guys my 2 cents.... ( with simple logics )

Shobit is correct for 100% throttle for LAND takeoffs and is reasonable for obvious reasons.

where as in hand launch scenarios ( which are nearly zero in real world) slow increase of throttle looks better than 100% throttle at an instant.

I may be wrong but as per my exp so far this is what i think stand reasonable.

regds
saurabh

That looks insane Dhruva... i dont know how you manage to fly that.... or infact see it xD  Cant wait for you to give it a "Beach Run" if you get the gist >:)

PS: is it just me or this actually one of the most informative threads in a while? :D

Sir i get ur point bout using 100% throttle ...but as you u see sir its hand launch there is no ground roll the aircraft is already in the air during launch so the matter of escaping  is negligible and the thrust to weight ratio is really high ...another thing sir is the torque generated on the motor on this model is  high...if he happens to use 100% throttle on this model during t/o  the aircraft will just roll and dive into the ground , very little airflow over the wings wont be  able to compensate for the amount of torque generated ...even if full deflection is applied ...correcting an aircraft in such a situation would be disastrous..to avoid the intial surge of torque and also to generate enough airflow to compensate the increasing torque ...keeping the throttle to at minimum for intial climb performance and gradually increasing the throttle to avoid the surge of torquue is a better approach to 100% ...plus this model has wing fence thus taking care of the other problems associated with airflow AND STALLS ...

Saurabh if i may correct here.... a takeoff is always a takeoff.... I am not saying maintain 100%...but it will be desirable to maintain a relatively a high throttle setting. I am saying have a throttle setting to get out of the danger regime (close to ground and in the air say.... 25 mtrs for models)... thereafter you may use the throttle as required....  Shannon your contention of gradually increasing throttle is wrong for many reasons....... I can explain that some other time, if you still need an explanation of how and why of aerodynamics, call me and I will clear the doubts....
Anyway... I am leaving this thread....
best Wishes

With that model and it's thrust to weight ratio, it is pointless and risky to give a conventional hand launch. Hold in your left hand pointing at 60 degrees up, give 70% throttle, and release

I am reminded of an old saying:
"If all else fails, read the instructions"
So I did.
With due respect to all participants on this thread, i'm quoting what the manual says:
The first flight.
Do not attempt to hand glide this model.
The Funjet is designed for hand launching only. Always launch directly into wind.
The model should be launched at 1/2 to 3/4 throttle,
With the wings level and the nose angled up at an angle of 20-30 degrees.
Don't launch the model "downhill" like a glider.

The manual also says "the Funjet Ultra rolls slightly to the left on full throttle"
Regards.

That's one interesting thread to contribute after a long time




Dhruva you are right, BUT not for a pusher like Funjet Ultra. it is for an aeroplane with nose mounted props and where the slip stream modifies the airflow pattern over empennage. See image and co-relate with what your Aerospace Eng professor's taught you

(http://www.rcindia.org/electric-planes/funjet-ultra-6s-300kmph-build-and-maiden-flight/?action=dlattach;attach=718228;image)

Shobit sir

I had written about chuck take off earlier in my thread 4 years ago, it is not 50% 75% or 100%. Thumb rule is just enough so that it slips out of your hand, that's why the pilot needs to hold it and determine how much throttle, later some one else may chuck it.

i understand, it is against the very method we learnt in real flying, believe me, as Nandan said, that's how it work in these Funjet kinds (Having owned and flown quite a few funjets & ultras i can tell you this)


Shannon is spot on

At high power Low speeds even fighter aeroplanes get into torque roll, sometimes it is uncontrollable and crashes. Pilots have lost lives because of this

Read page 92  of this document, worth keeping a copy of this document for all supersonic aerodynamics students

http://www.pixel-architecture.com/web/forum/massilia/MIG-21/DCS%20MiG-21bis%20EN.pdf (http://www.pixel-architecture.com/web/forum/massilia/MIG-21/DCS%20MiG-21bis%20EN.pdf)


KEEP IT COMING

Yes Sir, Agreed.
I meant that only for front mounted single engine prop planes. I did mention it in reply #17  :hatsoff:

Thank you for the Pdf sir. Very informative  :thumbsup:

Believe you me, couple of decades ago, Mossad or CIA would have given their right hand for that document. a lot of it mentioned in that document was enigma for  most western aerodynamicists. In fact One Iraqi pilot defected a MiG 21 to Israel and that's is the firsts time US & ISrael got to see the MiG 21 up close. Legendary & my hero Danny Shapira flew it and landed dead stick

Full account here (nothing short of a Hollywood movie)
http://theaviationist.com/2014/04/28/israeli-mig-21-007/ (http://theaviationist.com/2014/04/28/israeli-mig-21-007/)

Good to see The Boss back!
Dhruva said:
Since I'm Pursuing my Aerospace Engineering and i have come across Adverse Yaw condition which acts because of Spiral propwash generated by single engine prop planes.
It causes yaw when they are flown at high power and low speed (takeoff and climbout, for example.) The prop doesn't blow the air straight back, but gives it a bit of a twirl which causes yaw.

Dhruva, the propwash spiral on the fin produces yaw, but what is adverse about it?

Adverse yaw is when the down going aileron produces more drag than the up going one, producing yaw due to drag opposite to the direction of roll...

See 90 degree roll to the RIGHT in the initial pics?
Reason?

Like I said, without the Fluid Dynamics; just release, don't chuck. Use adequate amount of power and point the nose up so just by releasing your grip the model takes off

KK Iyer Sir , Yes the adverse yaw is only because of the Aileron Drag.

What i wanted to say is in general when a single prop front mounted rc aircraft is hand launched, the prop induced roll and yaw because of the propwash when added to the adverse yaw induced for countering that torque roll gives a huge unwanted yaw which is disastrous.

I came to know about this clearly when me and my team were preparing  for SAE-VIT Payload competition and during final testing one of the aircraft was chucked with full throttle and it just had unwanted yaw and crashed. The Aircraft didn't roll throughout  the flight and the torque compensation was done by the aileron.
So both unwanted yaw made the aircraft yaw and dive.

Sir, the initial pictures are from the maiden flight. I have given 100% throttle to make sure i have a good climb but turned out that I received more than 90 degree Left roll sir. :banghead:


And then in second flight, tried 50% on throttle with more alfa and this time the torque roll was reduced a lot.


Sanjai Rai sir is just right. I can just leave it vertically and it will just go. But sir I'm worried what if it just starts rolling just after leaving from hand and prop could hit the chucker. I have never tried vertical takeoff. :hatsoff:

Since i grew up in free flight days, i used to launch RC models holding them by the fuselage below the wings just aft of the CG.
Then with my electric Spitfire and 60% Curare learnt to hold them above the wing, at knee height, and give a gentle underhand toss at a shallow upward angle with 50-60% power.
Will probably work for you too! (No prop bite danger either)
Similar to what Rai saheb said, except he didn't mention the underhad toss!

(I'm known locally as the 'low throttle guy' who won't use full throttle even for takeoff!
Probably comes from my glider flying background, where one is always alert for a linebreak on tow!
Most of us don't have Gusty sir's exposure.
That MIG he posted climbs 750ft per second..
Hard for me to even imagine, as 5ft/sec was the best i encountered..)

But launching apart, try to find a way to log the actual speed (out of the 300 kmph potential)
One of Gusty sir's friends (in Mumbai?) went over 450kmph some months back...

Tried New Light Wieght Setup which is ultra cheap:
Motor : NTM 1700Kv 6s (Pulling 68A peak with old 1300mah Nano-tech 35C) (15$)
ESC : 80A Blue Esc from Hobbyking (37$)
Prop : 6x6 Apc
Still gotta track the speed but i believe it is 150-200 kmph around.

Check that Low pass at 00:55
www.youtube.com/watch?v=H-5ewKC_qNM

Too good

Very nice  {:)} {:)}

Thank You Saurabh sir and Sanjay sir  :hatsoff:

that was fast n furious  ;D {:)} {:)} {:)}

Thanks Vishal Sir. You shall see it once :D

Hey Dhruv, i'm buying the ultra soon, decided on my power system for now, just stuck on the servos, how are your turnigy metal gear servos holding up after all the speed flights ? Is it necessary to invest in one of those Hitec expensive servos as the company recommends?

Thanks and the speed you got from the above set up is sickkk. :D

Hi , Yes the MG90s are still going great. I have logged around 47 Flights. They have less then a mm slope after all.
They still are going strong and i can ensure you that they wont disappoint you.
I have done full power loops with these absolutely fine. :thumbsup:
Not about the money but one cant wish for any better on this jet.
At last just the peace of mind shall be there while flying   ;D

@dhruvafreak,
Saw your video again today.
You are able to talk while flying this at full throttle!
Wow!
I couldn't even see it.
Had to depend on the sound to anticipate where she'll be next in the video...
Great stuff. Great field.
Regards

Woah!
That is some crazy speed!
Good thing is there are no speeding fines for flying too fast :P

@K K Iyer Sir,
Thank You sir   :hatsoff:
Regular flying the aircraft has reduced the fear i had or maybe the helicopters did   ;D


@Topalle
Thank you buddy. About the fines, we never know  :giggle:


Posting a video (Something crazy)
Tried strapping a camera with 200mw Vtx and have a look.
Although it was not a 100% fpv flight but can say 70%ish it was. My friend recorded via his phone though a 7 inch screen. I was flying visually and using separate screen combined to bailout incase  8-).

www.youtube.com/watch?v=DbBjT0OIciI

@dhruvafreak,
Excellent experiment!
We need Gusty sir's input on why it looks much faster from the ground, than in the onboard view ???

@K K Iyer sir Thank you.
I guess the explanation will include lot of maths with angle and curves :o :giggle:

Gusty sir's input will be great  :)

Awesome!!!