Hello Everybody,
I have a stock FX79 with 3DR PH and is been flying fine as a fixed wing from a 4s lipo. Now thinking to convert it to a quad plane.
Asking all people who’ve done it earlier, is it better to convert to a 6s setup when converting to a quad plane or is it advisable to stay in 4s itself?
What motors to be used if doing a 6s setup or a 4s setup?
TIA,
Regards,
Adarsh
Hi Adarsh,
You can use either a 4s or a 6s setup as long as the battery can deliver the current needed for hover. For example, the SunnySky motors I used in my FX-79 QuadPlane can run on a 4s setup with 12" props or a 6s setup using 10" props. I have used them on many different setups like 4s Tarot copters, 6s FireFLY6s, and my 4s FX-79.
Good luck!
Thank you Greg, I saw the spec of the SS3508 700kv motor, the specs are rated only for a 4s.
Also, i was thinking of using TMotors 4006 380kv with 15inch props and 6s 10000mah, will this be an over kill for the fx79?
Is there a conversion kit i can purchase from somewhere, were i get the carbon tubes and the motor mounts and everything else needed for the conversion?
Thanks
Adarsh
The motors are rated for 4s when using a 12" prop. When using a 10" prop, the current is reduced so a 6s rating works great.
15" props will work as long as the booms are long enough to clear the props. The idea is shorter props will result in less drag. Depending on your application, the hover periods are usually quite low so you don’t need to make it a super hover machine like a copter.
I’m not aware of any conversion kits for this model.
Cheers!
As of now the pusher motor is the stock 3542 850kv; did you change the pusher also to the 3508 700kv or only the quad?
Thanks
Adarsh
All my parts are in post 1 of part 1 here. I used an upgraded forward power system originally tested on my Volantex Ranger EX. I suspect that the stock power system would work fine on 4s because most of the my flights have the throttle reduced to 50%.
Any updates on the project?
No, we’re still having winter here. I don’t fly much in the snow and cold anymore other than a few float planes. I’m off to Italy in April so maybe I’ll return to flying VTOLs by the end of May.
Cheers!
Thank you @GregCovey
First maiden, in mine garden…
I have vibrations in the engines, yet the propellers are well balanced.
Maybe it is from PID?
do you have an idea ?
Hi Eric,
It looks good except for the vibration. Look into these settings below. Mine are set to 0.25 for both. Try lowering yours a bit from what they are. What are your power system components?
Q_A_RAT_PIT_P
Q_A_RAT_RLL_P
Cheers!
I have same motors of you.
And 4s 6p 3000 li.ion
Esc is T f55A 4in1.
And i have à copy of your config.
How is your Pixhawk mounted? Is it mounted on a vibration dampener like mine?
Also, you are in a small enclosed area which may be blowing the air around. Maybe you can try a hover test in a more open field.
Agree reducing pids and try in a more open place if possible
I finally got a chance to test my FX-79 QuadPlane with the following changes below and it worked great! I haven’t pulled the logs yet to see how the Air Speed sensor did but my new X8R receiver eliminated the nagging “RSSI Low” alarms on my Taranis. The new 4s 8AH packs were bought for my Tarot 680 Pro hexacopter but work great in my FX-79 and weigh 3oz less than my previous dual 4s 4AH parallel pack setup.
Congratulation Greg. What is your Auw and it is interesting to know the amper draw during cruising. Is it still good during strong wind??
Regards
Tony
Hi Tony,
The winds were normal, not strong earlier this week…say 10-15mph (4.5-6.7m/s). During FBWA, the current draw was about 15amps for speeds from 15-24m/s when doing curcuits. The graph below shows flying, then transition to hover, then back to flying again.
I didn’t record what the stock FX-79 wing setup weighed but the added Quad system booms, motors, ESCs, and props weighed and additional 39oz (2.4lb)(1.1kg). My initial Nano-Tech 4s 4AH packs were from my Tarot hexacopter and weighed 15oz (425g) each for a total of 30oz (850g). The Foxtech Hover 1 Folding Landing Gear weigh 17g x 4 or 68g (2.4oz) so it’s pretty much a wash with my new lighter Zippy 4s 30C 8AH Lipo Pack that weighs 27oz (765).
The forward flight power system provides 746 watts at 51 amps using an APC 10x6 e-prop with a 4s Lipo pack. It’s the same power system I have in my Ranger EX plane.
It looks like my analog AS sensor is working so I can try a flight next time with it enabled. I was probably flying faster than I needed to but I am uncertain of the stall speed with quad booms and landing legs.
Here is two flights worth of travel. You can see from the take-off and landing "V in orange that “Mr. Lazy” doesn’t like to walk to the plane. 
Here is one of the two latest flights from above, which was only FBWA flying so you can see the transition color change from orange to yellow on take-off and back to green for landing. The quad rotors put up a roaring sound but the plane always looks nice and stable when returning to QSTABILIZE mode.
Congrats Greg: how your analog AS go? I installed an analog one in my new build not finished yet and concern about analog AS fail reports, now in doubt if I have to change for a digital one before first flight.
