hofer

Hi guys,
Just completed my Hokusei RayBird 70 with a GS contra drive !
Set up as follows :

- 5s/5000mah
- GS 50-63 Motors specified with 500KV
- two MGM compro TMM 8026 X3 ESC`s
- front prop : 14x8.5 APC pusher
- rear prop : 14x10 APC shortened by around half an Inch
- spinner and prop fixing is self made out from two TruTurn "EXTRA" 2 1/4" Units
- the drive unit is fixed with flex mounts
- distance between the two props could be brought up to the max : 38 mm ( 1 1/2" )
- the flex mount and the distance between the two props are essential to achieve a smooth operation !

Bench tests show +/- 40A per Motor - total 1400 watts - 4900gramms of thrust ( 49N or 11 Pounds ), perfect for this ship weighing in at 2750 gramms ( 6 Pounds ) !

The airplane has received numerous modifications to bring it up to the standard set by my Naruke Asyuler 70 !
Flight tests are imminent ( once the temps rise above 10 degrees Celsius over here ! )
see you
Hans

flywilly

My Feedback: (121)

HANS,
Looks great! What modifications did you make? There is a substantial difference in price between the two airplanes! I have both, still in the boxes. I have assembled a Hokusei Zeque which flew well and was nicely made for the price. Looking forward to hearing your flight report and a comparison to the Naruke Asyuler.
-Will

hofer

Hi Will,
O.k., here some info to this model and its set up :
- first, I spent some hours with the iron to straighten out the flight surfaces and bring all the flight controls nicely in line
I also made some carbon servoframes to house my futaba midsize 9650 servos
Then I used my own linkiage parts throughout ( linked the rudder via pull-pull )
- second, I did the same with the fuse and also here, I reinforced all the accessible joints with semi fuid ZAP
- third and most time consuming , I glued the nose to the fuse and reinforced that nose with with some carbon strips ( see pics )
Of course, the front ring of the nose had to brought to zero side thrust for the contra
then, as you see in the pics, the whole nose section was airbrushed to resemble the original design
Such a flush and permanently fixed nose does distinguish the Asyuler and now my RayBird from the usual screwed on versions of the many other ARF`s !

The addition of a nice carbon landing gear and a nice tailwheel summs up the mods
All in all, it has been quite some hours spent into the completion of that model and I still think it does hardly meet Asyuler standards !
The price for the Asyuler is high, but you will have the nicest kit in that 5s class, for sure !

Well, looking forward to that contra feeling and I am eager like you are to see how it compares to the beautifully flying Asyuler !
I keep you informed !
see you
Hans
-

hofer

Hi,
Well, thought I would post a video of the contra test run here.
The unit runs pretty smooth and the noise level seems moderate ( it runs even better in the plane with those flex mounts ).

http://www.youtube.com/watch?v=YfwvFHSnyl4 see you
Hans

rcflyer4fun

Must be a fun plane to fly?? How does it fly?

hofer

Hi,
Well, not yet flown - but I will keep updated on this one !

cmoulder

I am not (yet) a contra user.

However, just a suggestion based upon everything I have ever seen and read: Add some significant fences to the stabs to improve yaw stability. Maybe also a strake from the rear fuselage to the top of the fin.

I have heard stories firsthand of some very good Pattern designs becoming nearly impossible to fly when converted to contra without the addition of some aero devices to the empennage.

Good luck with the maiden!

hofer

Hi Bob,
Well, I know about all the posts concerning Contra drives
And yes, flight caracteristics might be different here
Anyhow, RayBird has an extremly large fuselage side area and the vertical stab itself is also pretty large !
Furthermore, my set up is not quite as progressive as Brenners and Seba`s in the 10s class - it uses proportionally smaller prop dias and higher RPM`s !
A scaled down 10s set up from Brenner or Seba for 5s would have to use 16x16 props driven at lower RPM`s, but such props props and the required big dia - short stator motors are not on the market !
I really do hope to reach neutural flight without all these additional spoilers that get common nowadays - I just like "clean " ships !

Looking forward to the first flights - let`s hope that we will have a winner here !
see you
Hans

cmoulder

Looking forward to your results. It will be interesting to see how many mAh's used for a typical flight..

I have been hoping for some time that the dual-motor configuration can be made practical as I am not a fan of gears and belts, and the consequent increase in complexity and maintenance.

mups53

My Feedback: (41)

Very cool!!!!

hofer

Hello,
Maidened my Contra drive RayBird today !
Now, how does it fly ?
Easily said - it flies very good in every aspect - the conta drive performing exactly according expectations - far enough Performance - the noise is typical for a contra ( louder than single prop for sure ! )
All in all, after flying a Wind 50 and an Asyuler 70 as well, all that I can say is that, in my opinion, all the modern pattern planes fly veeery alike in every aspect even though they might be powered by an outrunner with folding prop( Wind ),
an inrunner with fixed prop(Asyuler) or even such a contra drive in the RayBird !!
I can also not see any notable difference in powerconsuption for a typical flight Routine !
I honestly could presently not decide on which of these 3 planes I would choose to fly in competitions, such close they are !

see you
Hans

Alex Voicu

Congratulations for your maiden flight, very nice work!

It will be interesting to see how reliable this contra motor is; i have a GS Model E63-72 contra motor i recently tested but i'll run it on the bench for a long time before installing it in my new 2m plane.
3000W max power at 40 deg C heat in the summer puts a lot of stress on the motor, so i need to make sure it's reliable first.

Thanks for sharing your experience with this motor, please keep us updated.

hofer

Hi Alex,
Yes, I know about your GS motor for the full size class.
I do wonder though if your motors are able to turn the big 21 or 22" square props at the desired low RPM (+/- 3500) - that requires quite some torque ! Probably you will have to compromise here and go for something like 17 to 19 " dias turning at 5000RPM
I would have liked to turn 16x16 props at +/- 3700RPM on my 5s set up, but I guess the motors would refuse ! There are no such sized Pusher props available as well.
With my current 14x8.5 front and cut down 13.2x10" on the back turning at +/- 6500 RPM, the noise level during the verticals ( say more than 70% power ) is pronounced !
Flight speed on the other hand is just perfect !

During the next flights I will optimize the throttle curves and motor switching frequences inbetween the front and rear motor to achive that desired zero torque feeling throughout the whole powerrange.
A little bit of finetuning required here, but I still believe that the two Motor, two ESC approach has potential !


Keep you updated on my experience !
Hans


PS: have you ever looked at those Tigermotors (G-series) itended for quadcopters, to be used for such a low RPM, high dia application for full size F3A planes ?
These motors have exactly the desired layout - big Diameter/short Stator giving high torque !

Alex Voicu

I made 2 tests, one with 5S battery for each motor and one with 10S battery, props APC 20.5x20.5 front, 20x22.5 rear. On 5s, the power is not enough for a 2m plane (only around 1800W), but on 10S it exceeds 4000W, so i will have to limit my throttle curves.
The factory says it's safe to run the motor at 10S, as long as i'm not exceeding the rated power.

Here's a video of the 5S test:

http://www.youtube.com/watch?v=J99YsvlpeaU Fiala makes some nice propellers (both tractor and pusher in any size needed): http://www.vrtule-fiala.cz/shop/inde...id=6&Itemid=53

I looked at some multicopter motors from Dualsky and Tigermotors, but most of them are not powerful enough. Did you find one with the required characteristics?

rcflyer4fun

That's a very Beautiful plane! It looks big and probably flies big too.

hofer

Hi,
Yes, I really like this RayBird ! And no, it is not big - Standard 5s plane at 1500x1400mm ! AUW 2800 gramms

To Alex :
I am thinking of the following Motors for a 10 s Flyer :http://www.globe-flight.de/T-Motor-U8-13-135KV
This one driven with 10s on a 22x22" prop could work fine ! I think the Motor weighs around 240 gramms !
At 135 KV it would turn nicely at around 4000 RPM delivering +/- 1400 watts
I see you
Hans

irishlisle

Can you Guys tell me where I can buy a GS Contra motor online-Thanks

Alex Voicu

I contacted GS Models by e-mail at [email protected]
They were very helpful and agreed to manufacture a custom motor for me with the desired kV.

Their website seems to be down at the moment. Here's a link i found though:
http://www.aliexpress.com/item/GS-E6...tml#magnet-ads

irishlisle

Thanks Alex