Foam Board Opterra Flying Wing

[Hineybadger]

I decided to build the foam board version of the E-flite Opterra Flying Wing. This is my first wing plane I've built. I opted to go with a 50mm EDF to mix it up a little. My build is roughly scaled down 45% from the actual model. Maiden will be conducted later this afternoon. Video to follow.

 

[clolsonus]

Careful with the CG on that, it looks like you have a lot of the heavy stuff (motors and servos) pretty far aft. There are online CG calculators for flying wings that can be super helpful ... and my personal experience is to start on the forward range of what they suggest because the aft range (for me) has been pretty unflyable -- stall/spin/unstable. If you get the CG in a good safe spot I think it should fly great. I have a sonic 64 (molded foam flying wing with edf) and it is one of my favorite models.

 

[CappyAmeric]

With the EDF mounted high and aft, be ready for weird a pitch moment

 

[L Edge]

Do you have any up thrust or side thrust with the EDF?

 

[CappyAmeric]

Do you have any up thrust or side thrust with the EDF?

"Side" (yaw) thrust, no. "Up" thrust - (pitch), possibly, sometimes a lot.

 

[L Edge]

"Side" (yaw) thrust, no. "Up" thrust - (pitch), possibly, sometimes a lot.

If you look at his third picture of his design, the exhaust tube looks like it is pointed down which would give him a nose down pitch. (bad)

 

[Hineybadger]

If you look at his third picture of his design, the exhaust tube looks like it is pointed down which would give him a nose down pitch. (bad)

Yes, it was real bad every time I tried to fly it. Gonna relocate the EDF and build a straight out thrust tube and re-fly.

 

[Hineybadger]

Careful with the CG on that, it looks like you have a lot of the heavy stuff (motors and servos) pretty far aft. There are online CG calculators for flying wings that can be super helpful ... and my personal experience is to start on the forward range of what they suggest because the aft range (for me) has been pretty unflyable -- stall/spin/unstable. If you get the CG in a good safe spot I think it should fly great. I have a sonic 64 (molded foam flying wing with edf) and it is one of my favorite models.

The total weight was 540 grams. It nose dove on every flight attempt. Gonna relocate the motor and work on the wing a little to see if it will eventually fly. This is the first flying wing I've ever attempted to build. Not as easy as all my other builds.

 

[Hineybadger]

With the EDF mounted high and aft, be ready for weird a pitch moment

Yep weird it was. Straight down to the ground every time.

 

[Hineybadger]

Do you have any up thrust or side thrust with the EDF?

I had straight down to the ground thrust. Gonna relocate the EDF and build a new "straight" thrust tube.

 

[Hineybadger]

So the maiden flight is below. Got some work to do. This is my first flying wing so I expected some trials and lots of errors. But I do love a good challenge.

Update: I did reposition the EDF before the flight but it still just nose dove ever flight attempt. This build was roughly half the size of the actual E-flite Opterra. Thinking maybe the control components are too heavy for this small of a build. Should have probably used small servos and enlarged the elevons. But what do I know? I just enjoy the challenge of design, build and fly/crash ......

 

[CappyAmeric]

Yep weird it was. Straight down to the ground every time.

My experience is that wings have a very light wing loading with little pitch authority. That means that if you have a thrust line above or below with the thrust arm even an inch or two, the pitch moment can't be overcome. Angling the EDF might help, but I suspect you need a elevator mounted far enough back to provide a counter pitch moment.

 

[Ryan O.]

Make sure to add some reflex to the elevons as well, and good luck with the redesign!

 

[L Edge]

So the maiden flight is below. Got some work to do. This is my first flying wing so I expected some trials and lots of errors. But I do love a good challenge.

Update: I did reposition the EDF before the flight but it still just nose dove ever flight attempt. This build was roughly half the size of the actual E-flite Opterra. Thinking maybe the control components are too heavy for this small of a build. Should have probably used small servos and enlarged the elevons. But what do I know? I just enjoy the challenge of design, build and fly/crash ......

Did you play with some up elevator trim to see what happens?

 

[Hineybadger]

Did you play with some up elevator trim to see what happens?

Yes. I had it trimmed up.
I actually put it on a semi-flat Bermuda grass soccer field and it would not lift off. It would just cruise around on the grass.

 

[Hineybadger]

My experience is that wings have a very light wing loading with little pitch authority. That means that if you have a thrust line above or below with the thrust arm even an inch or two, the pitch moment can't be overcome. Angling the EDF might help, but I suspect you need a elevator mounted far enough back to provide a counter pitch moment.

Part of my redesign is going to be lowering the EDF to where the EDF's center point is inline with the height of the elevons. Gonna see what happens without adding a thrust tube first. This should at least be a good start for developing straight center thrust.

 

[skymaster]

Did you test glide it. your last picture shows that your model has a shape fron the back to the front and it kind of looks like an eagle. very nice

 

[L Edge]

Part of my redesign is going to be lowering the EDF to where the EDF's center point is inline with the height of the elevons. Gonna see what happens without adding a thrust tube first. This should at least be a good start for developing straight center thrust.

So that means part of the EDF will hang below the wing on landing. How are you going to protect the spinning blades from small stones or clumps of grass, etc, from damage or destroying them? Ask me how I found out.

 

[Hineybadger]

Did you test glide it. your last picture shows that your model has a shape fron the back to the front and it kind of looks like an eagle. very nice

That's exactly what my wife said. And no I did not test glide it and yes I always normally do. Total error on my part.

 

[Hineybadger]

So that means part of the EDF will hang below the wing on landing. How are you going to protect the spinning blades from small stones or clumps of grass, etc, from damage or destroying them? Ask me how I found out.

I have 3 little plastic skids I placing underneath the wing that will give the EDF clearance from the ground.