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Feb 28, 2015, 04:12 PM
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Build Log

EM 11 Orka: 58" Semi Scale


So I was looking for a twin engine plane for my fleet. However, most of the builds I came across had tractor motors and 1800kV motors I had lying around would not be suitable for them. So I thought of building a twin pusher. This configuration does not seem to be that common though and online search to get some ideas produced the EM11 Orka. EM guys have done an amazing job on concept and design. I just loved the airframe and just had to build it.
Search on RC groups yielded no plans, so I set out to do this scale build from scratch.
Now, I don't have any scale building experience so I'm going to call it semi-scale at best and I have no patience like the "real" scale builders so this is going to be a fast and simple build. Also, I only want to use the cheapest and readily available (LHS, DT, Home Depot etc) materials like DT FB, wooden dowels, paint sticks, popsicle sticks, bamboo skewers, and hot glue!
Seems like there are multiple versions of Orka and some versions got retracts as well as T tail. Just to keep the build simple, I'm going with fixed tricycle landing gear with cross tail. Paint scheme is simple enough that I could just use color tape.
Last edited by elewon; Mar 26, 2015 at 09:29 AM.
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Feb 28, 2015, 04:13 PM
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Landing gear


Here is how I built the landing gear:
For the nose gear, I just got the Apprentice nose gear from LHS.
For the main gear, I used a 15" long piece of 1/2x3/4x1/16 aluminum from Home Depot. Just cut the grooves and it will bend easily. Drill holes for wheel axles and attaching it to the fuselage.
For the main wheels I used 60mm foam wheels.
Last edited by elewon; Aug 13, 2015 at 03:00 PM. Reason: Added more pictures
Feb 28, 2015, 04:14 PM
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Pre maiden and maiden


Details on power system:
50g 1800kV motors x2
30A ESCs x 2
9g servos x7
The motors and the ESCs are matched - same make/brand. I'm planning to use a single 2.6AH, 35C battery to provide total current of upto 91A. I'm hoping the current draw would be quite less than this and the battery won't get hot or be all puffed up.

AUW 37oz for wing loading of just over 14oz/sqft
Last edited by elewon; Mar 05, 2015 at 03:00 AM.
Feb 28, 2015, 04:15 PM
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Flight Video


Here is a montage of flight videos

Orka Flights (6 min 24 sec)
Last edited by elewon; Mar 15, 2015 at 02:17 AM.
Mar 01, 2015, 12:43 PM
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so, fuse is almost done, now on to building the wing
Mar 01, 2015, 02:48 PM
TonyS
Very interesting!

TonyS
Mar 02, 2015, 12:47 AM
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beautiful... and really clever:
on tractor planes, one point than suffer a lot on a hard landings and soft crashes is the union between the motor and fuselage or wing (the old firewall): just need a minor fissure and the traction of the motor will do the rest...add the propeller expose and the flight afternoon could end more faster than you want.....
conversely, on pusher planes the last thing will suffer is the motor, even with medium damage on the motor basis, a masking tape is enought to keep the motor in their position....

for sure this plane could be a good and strong trainer...
congratulations
Mar 02, 2015, 11:11 AM
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Thanks for encouraging words. rajazo I agree with you and I prefer pusher planes just for these reasons.
On this build though seems like I'm having some problems with the wing. Scale wing is so slender and thin, it's difficult to fit the ESC in the wing. Didn't realize this before I was about to glue the wing. So need to spend some time thinking about how to fit the ESCs in the wing without creating additional drag.
Mar 02, 2015, 04:05 PM
TonyS
I can't quite determine dimensions. However, to me it appears that the motor nacelles should offer sufficient thickness to perhaps hide the speed control if you mount the circuit board vertically, to either side of the "stick". Certainly the esc should fit sidewise if you change the method of mounting the firewall.

TonyS
Last edited by tonystro; Mar 02, 2015 at 04:06 PM. Reason: trying to clarify....maybe....
Mar 02, 2015, 04:22 PM
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Unfortunately, the firewall is just 1.5"x1.5" and the ESC is 1"x2" plus some more for wires etc. Since I have already glued the firewall etc, for now, I'm thinking of mounting the ESC underneath the wing such that it'll be hidden inside the fuselage. I'm going to have to increase the wire lengths etc but this seems like an easy solution without causing major rework on the wing.
Mar 02, 2015, 08:35 PM
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Looks like longer wires will work. I glued the wing leaving ESCs out. I just velcro'ed them to wing bottom surface and cut a slot in the wing saddle so that the ESCs are in the fuselage. She is looking quite scale like now. So far not bad!
BTW, this is the most complicated wing I have ever built and it's so thin getting it right is quite challenging. I'm also worried about wing loading and airspeed when coming in for landing but then that's where all the fun is .
Mar 05, 2015, 02:57 AM
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Folks, she's all done!
Took her out for the maiden and the maiden flight was uneventful. This is the heaviest plane I have flown but no bad tendencies. I had problems with thrust angle on the motors - too much down thrust but I guess that's a good problem to have on maiden plus I could trim it out just for the maiden.
Flaps worked very well - in the wind she almost hovers with flaps down and it's bit tough to get her to descend. Looks like I need to mix in some down elevator.
Went through 2 batteries and quite nice flyer! With the LEDs wired up, evening flying is going to be a pleasure after the time change!
Very happy with this build.
Mar 05, 2015, 01:41 PM
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Congrats. .. it looks really good.
Please tell more about performance .. flight time, climb capability, rolls and loops, stall conditions. ...


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