10cc 3D gasser --- An exercise with a VH Sabre-X 51" and a Evolution 10GX

[Enterprise]

Once data started to come back on the 10GX on other forums I learned that this motor likes big props unlike a glow motor. Joe and myself started to kick around the idea of doing a full on 3D airplane with this motor, more for the novelty I think than the actual flight experience as an electric is superior in every area except flight time (even cost). Based on the weight of the components you could pack a 4s 5000 into this plane and get long flights and still be lighter if you could get it to balance. I am fully prepared to utterly fail in this endeavor, but I intend to document the journey.

http://www.horizonhobby.com/products/10gx-10cc-60-cu-in-gas-engine-EVOE10GX

The first step was to pick a airframe to use. The data available to me said that 7lbs of thrust was realistic with a 13x6 prop which meant that to get good 3D performance I need to be in the 4lb range. All the old 40 size glow planes like the old Goldwings were advertised in the 5 to 5.5 lbs range which probably means 6 and this was not going to work. Since .25 size glow planes went the way of the Gold standard, I started to look at electric conversions. Since I knew it was going to be porky I wanted one with a big wing area and enough space in the fuse to house the components. I seriously considered a 3DHS 51" slick since that had been done with a glow conversion by JClark, but this Value Hobby aircraft had a much larger wing and was basically half the price. Another major factor was the way the motor box attached which made the addition of a firewall very basic.

http://www.valuehobby.com/51in-sabre-x-arf.html

After doing some more research I learned that the recommended servos were trouble prone so I ordered Solar D658s from Hobbypartz. These servos did not come with mounting hardware and a last minute scramble on ebay found some JR mini hardware for little money.

http://www.hobbypartz.com/33p-solarservo-d658.html

Since vibration is a major concern with this airframe I elected to try a Hyde mount. A side benefit was it helped get the needed spacing on the cowling despite the weight penalty.

http://www.centralhobbies.com/Engines/mounts/hydmnts.html

Since weight is the major enemy on this project I am using a Tech Aero IBEC to power the ignition. I use these on all my gassers.

http://www.tech-aero.net/ultra-ibec

I decided I did not feel like converting a 6oz glow tank so I just got a Fourtitude 8oz tank

http://www.3dhobbyshop.com/Fourtitude-8-OZ-SQUARE-TANK-W-line-mount_p_16016.html

After opening the ARF I realized that I wanted to mount the motor inverted and this led to ordering a Jtec wrap around Pitts. They are on backorder and I might end up using the stock muffler for a bit for break in and such.

http://jtecrc.com/evolutionwraparound.htm

I will try to keep this as organized as I can and update the first few posts so that one does not need to wade through the whole tread.

 

[Enterprise]

Weight discussion

I weighed everything going into the model and have notes on this to compare it to a electric setup.

Airframe weights (in grams)
fuselage 251
canopy 60
cowl 74
spar 40
gear 79
hardware pack 100
vert stab 6
rudder 31
horizontal stab and elevator 62
wing 117 x2
aileron 42 x2

Airframe total 1021 grams

Radio gear
servo 26 each 4 for electric and 5 for gas.
RX w/ telemetry 27

Electric setup
motor mount provided in kit 38
motor 160
ESC 68
battery 312

Electric setup total 1730 grams + prop and spinner. Appoximately 3.85 lbs AUW.

Gas setup
10GX with prop 448
Hyde mount 58
Beam mount 61
fuel tank 36
ignition unit 97
IBEC 22
RX battery 89
throttle servo tray 6
Jtec muffler (I forgot to weight it before I installed it)
reinforcement wood 84
jtec muffler 56

Gas setup total from weighted components 2135 (4.7 lbs) + spinner

Total weight of finished plane is 2300 grams (5.07 lbs) weighed on the same scale dry.

This weight gain is wiring, zip ties, fuel tubing, glue, velcro, and all the other little things one never thinks of. I could assume at least half of this weight would also be added to a electric so the weight difference is close to a pound, maybe less. I am also not sure I added in the my ignition tray which was not super light.

 

[Enterprise]

How the ARF came out the box





First I added triangle stock.



then I added dowel and some bracing pieces.



I had to build a platform for the ignition box after. This is mainly a balance decision. I drilled lightening holes to save some weight.



Here it is with the Hyde mount on. The fuel tank will be detailed later. I made the firewall by laminating two sheet together to get the thickness for the M3 blindnuts used in the mount. I epoxied it onto the front seen earlier in the dowel shot.



All mocked up. I used some washers to get the right and down thrust. It appears to be 2 degrees right and down from the electric mount, but that will have to be a tuning item later.



Installed with new beam mount for additional spacing. Hall sensor is routed back to the ignition box. Also I hooked up the temp sensor like Pete from horizon showed, looped around the spark plug.



Throttle instillation. I had to go in one notch on the arm to get end points to be close to 100.



I hung the fuel tank from the battery tray. This way I can see the fuel level from the outside and also I can route the fuel lines better. It is possible to put it on top, but it is very tight. Another benefit is having this mass more centered on vertical CG



Ignition module on it's mount. I also hooked up the RPM sensor to the TM1100.



Cowl spacing. I think this will enough to allow the Hyde mount to work.



This a picture of the fuse inverted to show the ignition, wiring, and throttle box.



Final Engine installation from the bottom of the cowl. You can see the temp sensor and the Jtec pitts.



I did z bends instead of the EZ connectors on the push rods and only did one one the rudder as I had binging over a certain amount of rudder throw.



Finished plane at the club's show and tell night.



Here is where I had to install the battery in the tail. 1900 LiFe and it balances with no fuel. I might redo the tail wheel which will add a little weight and hopefully it will have a good 3D C of G.

 

[Enterprise]

Build Vidoes:

After I tuned the engine, here is the first run ups on the plane. I purposely did this without the wings to see what the vibrations would do. The elevator servo screw backed out, so I replaced the phillips head M3 with a socket cap screw and put in thread lock.

[video=youtube_share;y1hYb7dTTXQ]http://youtu.be/y1hYb7dTTXQ[/video]

 

[Enterprise]

Finished photos

 

[Enterprise]

Maiden Flight.

[video=youtube;63pyLgdvmIA]http://www.youtube.com/watch?v=63pyLgdvmIA[/video]

 

[Enterprise]

End of project review.

Even though the project did yield a airplane capable of 3D flight, it was not a raging success. The last time out with the plane I realized that the wing loading was still a bit too high and had to be flown fast most of the time unless you brought it into a hover. Harrier was not a easy maneuver with the plane.

With only 7lbs of thrust, the airplane must end up around 4lbs. This airframe was very light with a lot of wing area, so I am not sure where I could have made different choices that would have yielded better results. I have talked to Ben and Cody about using a 3DHS airframe, and the 57 Extra seems to be the choice. Based on my recent experience with the 15cc project I think I could come out around 5lbs, but with more wing area and better designed airplane for fast flight. I think that would be the logical next attempt in this arena.

For now I am going to put the airframe in the attic and use the gear in some sport flying airplanes. The airframe is still very flyable and will only be stripped of the power plant and servos. It did not show any signs of vibration fatigue and survived despite most predictions and did have a number of incidents.

I can see myself getting another one of these Sabres and doing it up electric per spec and having a fun time with it's intended purpose, low and slow 3D under 4lbs!

 

[hone]

Sub'd. Looks like a fun little project

 

[Feral]

+1 subd

 

[Ohio AV8TOR]

Subd as well, Is this your first use of a Hyde mount? I used them back in the day with a YS91 and the do reduce vibration to the airframe but the motor does shake more than normal. Make sure that you have enough clearance in the cowl ring to the front of your motor or you will need the nose ring. Mine shook more than I would like.