I made one more mod before starting the other wing. I noticed that the unused flap could be anchored to the winglet to make it more solid. I made a small balsa insert and glued it using Foam-Tac. Now the flap corner and winglet are secured together. Once you paint it, it is hard to see.
This last picture shows the placement of my second joiner tube.
Greg,
Here is a good way to improve the performance of a flying wing - install an actual bird on it to improve stability 
Paul
p.s. Photo from an event called “Pecan Patch Fly-In” in Georgia USA.
LOL! That is funny. I needed that…thanks, Paul!
This was a low wind test with the modifications to strengthen the wing extensions. When flying from 15-23mph in low wind, as shown below, the FX-79 flies great! However, when speeding up, it still has a tendency to tuck so my modifications did not seem to work.
I plan to re-mount the quad booms next and try another test with Q_ASSIST_SPEED set to 15. Perhaps if I keep the FX-79 flying at a reasonable speed then the Q_ASSIST_SPEED feature can be set to keep it from stalling.
The two motors were replaced and the quad booms are getting re-mounted on the FX-79. It will be interesting to see if it works better as a QuadPlane using slower speeds. If not, then this project will be concluded.
I recently bought an E-flite 2m Opterra. It is a beautiful design! Most people don’t know the designers but I have reviewed many of their models in the past and was present in Toledo when George Hicks won the first indoor flying championship. It was a long time ago!
The Opterra wing is not a flat bottom design like the FX-79. It is semi-symmetrical like my Zagis and FF6 wings. This design is made to glide well and be efficient in the air. I will likely make an APM Plane Fall/Winter project out of it, adding the retracts so it can take-off from the flying field.
I re-mounted the quad booms after testing the FX-79 as a normal wing. The FX-79 Buffalo QuadPlane Flight Test 2 was successful! After transitioning to FBWA mode, I throttled back to less than half and the wing flew fine in 5-10mph winds. This was a promising performance so I will plan to test it again.
Looking good and promising. Looks like you need to enable the brake (if available) to prevent the front props from freewheeling during FBWA.
Good luck.
Will you be posting your final PID / settings after it’s all tuned?
I’m still using the PIDs posted in the July 4th .param file above. I have only changed the two Flight Modes back to using QSTABILIZE and QHOVER since the quad booms were re-mounted.
I can post them again soon since I realize their is a time limit on this forum for keeping files.
Cheers!
My latest config file.
BuffaloQPconfig2.param (16.0 KB)
My only changes are these flight modes for QuadPlane.
FLTMODE1,17 (QSTABILIZE)
FLTMODE2,18 (QHOVER)
FLTMODE3,5 (FBWA)
FLTMODE4,7 (CRUISE)
FLTMODE5,12 (LOITER)
FLTMODE6,0 (MANUAL)
Thanks for the file.After watching the video, I’m impressed! As I have all the parts ready to go, I’m going to start the build. I sure wish there was a way to eliminate the possibility of it ever tucking, either aerodynamically or with the FC setup. I could see this as my main platform otherwise. Perhaps some aero engineer will stumble upon this wing and figure it out for us?
Given the successful test, but the possibility of tucking, what is your plan for the quad? Do you feel the cause, and a fix would ever be found? I sure hope so as I was so exciting by the project I purchased 2 79’s!
There are ways to reduce or eliminate the tucking. You should be able to read about it on-line. For me, it requires excessive tinkering. The FC has proven that it cannot handle the tuck (maiden flight) but you could use it to keep the plane at a lower speed with the aid of an air speed sensor. The FX-79 appears to have lots of lift which allows it to fly slow. I am not sure what the stall speed is with the added quad booms.
My immediate plan is to re-test it to gain more confidence. I may also install the landing gear set previously posted over the winter months.
My current focus has been on the Ranger EX, Opterra, and Nimbus 1800. All different designs using APM. The Ranger EX requires no hand toss but a road or mowed field to take-off and land. It can carry multiple cameras. The Opterra requires a hand-toss and needs to land in field. The Nimbus VTOL can take-off and land in a small clearing. It also easily breaks down into small sections. Compared to my FireFLY6, the Nimbus VTOL uses half the motors, half the ESCs, and breaks down more easily. The FX-79 doesn’t break down as much but it does have a nice square shape with the quad booms attached which eases the storage.
The second (and 3rd not videoed) test of the Fx-79 Buffalo QuadPlane was also successful. I kept the throttle to 50% or less after the initial transition from QSTABILIZE to FBWA. The video shows a double transition about mid flight. I have good control in both hover and forward flight modes.
We flew four APM planes, two VTOLS and two planes. One of each type (VTOL or plane) had an Air Speed sensor and performed noticeably better in CRUISE and LOITER modes. I am convinced that the AS sensor provides a much quicker response to wind changes than just using GPS speed indication.
Looking good! The transitions look smooth.
I concur. It really simplifies tuning the transitions and general performance in all flight regimes. I think it helps tremendously in achieving to tune for maximum efficiency, as well.
Good luck.
Thanks, rollys!
I see the US stock of FX-79s is back and there is a sale on the China stock for $109.
Hey Greg I’m doing the same to my fx 79 can I please ask what outputs did you use for the quad motors and then the fx 79 motor on the Pixhawk
Hi Jesse,
I’m using standard APM servo outputs from the Wiki. My quad layout is set up as an H-frame using outputs 5-8.
The elevon setup is here and the quadplane frame setup is here.
Do you activate brake ESC ?
Hi Axwan,
No, I never use brake and just let the prop free spin.
Use the “here” link above to jump to the new section of this thread on the VTOL forum.
Cheers!
