I built a two-sheet foam board flying wing from plans I found online, and it refused to fly. Four attempts. Endless CG changes. A dead motor and ESC. I seriously considered quitting the hobby. The real problem turned out to be something I'd stared at the whole time — and the fix took one evening. If your plane keeps nose-diving no matter where you put the battery, this write-up is for you.
| Attempt | What happened | What I blamed |
|---|---|---|
| 1 | Nose-dived straight into the asphalt driveway | CG + loose battery |
| 2 | Didn't crash immediately. Still nose-diving hard | CG (nose heavy?) |
| 3 | Technically a flight — super pitchy, barely controllable, hard crash | CG, again |
| 4 | Briefly flew, then unstable crash; electronics ripped off | Honestly? No idea anymore |
| 5 | Flew. Smooth, trimmed, low passes, even a (very slow) roll | The real fix: removed the under-cambered trailing edge + added reflex |
The plans looked simple: a two-sheet foam board flying wing. Cut here, glue there, wooden spar for strength, electronics in, done. The build genuinely did go smoothly — wings cut and joined, fins on, motor pod, servos wired for the elevons, control rods hooked up. It went so well I decided to spend a few extra hours on a paint job before it had ever flown. Blue base coat, white streaks, black tips. Because everything was going perfectly and it was obviously going to be the best-flying plane ever, right?
Then I launched it, and it nose-dived straight into the asphalt.
Every RC builder knows the reflex: it nose-dived, so it must be nose heavy — move the CG. I strapped the battery down better and moved the CG. Then moved it again. Flight three "kind of flew," which gave me just enough hope to keep digging, but it was so pitchy it was barely controllable.
I spent more time than I'd like to admit on the CG question, including several long conversations with our favorite virtual helper, Chad. First we decided the CG was way off and moved it forward. Then, after I described the wing shape in more detail, we decided it should go way back instead — at one point my battery was 7½ inches behind the leading edge, about halfway back on the chord, which the math said was crazy. Every hand launch ended the same way: release, nose-over, catch it or eat it. By the end I'd moved the CG in a full circle back to roughly where I'd started, and I didn't trust anything anymore.
The lesson hiding in there: when moving the CG in both directions doesn't fix a pitch problem, the CG probably isn't your problem. CG errors respond predictably — too far forward flies stable but dives and needs constant up-elevator; too far back is twitchy and stall-prone. A plane that pitches down hard at every CG position is telling you something aerodynamic is forcing the nose down. Mine was. I just couldn't see it yet.
Right when I was ready for another attempt, the motor and ESC quit entirely. The only spare ESC in my bin had no built-in BEC — meaning nothing to power the receiver and servos — so I soldered in a separate external BEC and put new connectors on the motor. It was a whole thing, but it worked, and honestly it's a skill worth having: an external BEC is a totally normal setup on bigger planes anyway. If you've never wired one, my free Wiring Designer has external-BEC hookups built in — it'll draw you the exact diagram, opto-ESC cases included.
When the motor and ESC quit mid-project, my only spare had no built-in BEC — nothing to power the receiver and servos — and the fix meant soldering in an external BEC and new connectors. A spare with a BEC already on board turns that whole evening into a five-minute swap.
The spec that matters: "with BEC" — the built-in regulator that feeds your receiver and servos. No BEC, no control power, no flight.
If you end up flying an opto/no-BEC ESC anyway, you'll be wiring an external BEC — the Wiring Designer draws that exact hookup, opto cases included.
After flight four ripped the electronics off the airframe, I stepped away for the weekend. Ran the numbers through another CG calculator — which said my original CG had been about right. So if the CG was right, what was forcing the nose down?
Then I remembered a clue: earlier, adding more reflex to the elevons had helped a little. I looked closely at the wing and finally saw it — the plans had built in an under-cambered section about 5 inches deep along the trailing edge. The rear of the wing curved downward. In effect, my wing was flying with flaps permanently deployed: all that downward curvature at the back of the wing produces a strong nose-down pitching moment, and on a flying wing there's no tail to fight back.
So I tore the trailing edge apart, spread it open, and removed the under-camber to make the back of the wing flat. Now air flowing off the wing runs straight onto the elevons instead of being deflected downward first. I re-rigged the control surfaces with a bit of reflex, did a quick repaint, and headed to the field. Flight five: after one pushrod tweak (my initial reflex was too much — it ballooned), it flew. Really flew. Three mistakes high, trimmed out, smooth low passes, and the slowest aileron roll I have ever seen in my life. But it worked.
Sight down the wing from the tip. On a conventional plane, some under-camber (a concave lower surface) is fine — a tail is there to balance the pitching moment it creates, and slow flyers use it on purpose. On a flying wing, downward curvature near the trailing edge is poison. Symptoms: the plane noses over on every launch regardless of CG, it gets slightly better when you add up-elevon trim, and it feels like it's fighting you nose-down at speed. If moving the CG doesn't change the character of the problem, check the airfoil, not the battery position.
Reflex is the opposite of camber at the trailing edge: the last bit of the airfoil (or the elevons at neutral) angles slightly upward. A cambered wing naturally wants to pitch nose-down; a conventional plane cancels that with its horizontal tail pushing down way back on a long lever arm. A flying wing has no tail — so the back of the wing itself has to do the tail's job. That little upward curl is the "tail," built into the wing. This is why every flying wing you'll ever see flies with elevons resting a few degrees above neutral, and why my under-cambered trailing edge — reflex's exact opposite — made the plane unflyable.
On a conventional plane, the tail sits on a long moment arm, so pitch stability is generous — the conventional 25–30%-of-chord CG range has plenty of slop in it. A flying wing's entire pitch authority lives in a few inches of elevon at the back of the same surface generating the lift. The CG typically needs to sit around 15–20% of the mean aerodynamic chord, and the flyable window is a fraction of an inch on a plane this size. That's why the CG rabbit hole was so believable — flying wings really are CG-sensitive. Mine just happened to have a second, bigger problem stacked on top. When you design your next wing, get the CG computed rather than guessed — the Airplane Designer does it from your dimensions in about a minute.
Rock bottom on a project is real — you pour hours in and it just won't work. But every one of those failed flights taught me something I now can't un-know: read the airfoil before you blame the CG, test-glide before you paint, and keep a spare ESC with a BEC in the bin. The next flying wing might even fly on the first try. Might.
Spot something off? Tell me and I'll fix it.
Auto-transcribed from the video, so expect the odd mis-heard word. Here so you can search or skim what was said without watching.
This is me seriously considering quitting the RC plane hobby for good. After I found some plans online for a two-sheet RC wing, I thought this is going to be a piece of cake. Cut here, glue there, cut there, glue here, throw in a wooden spar for strength and add some electronics and it's ready to fly, right? I was sort of mistaken. So I got the wings cut out, started gluing them together, added in the wing spars and joined the two halves together.
Then it was time to cut out and install the fins. Next was the motor pod, motor, ESC and receiver. Once that was done, I wired up the servos for the elevons and connected the control rods. At that point, this plane was ready to fly. Alrighty, so I decided I want to put a coat of paint on the plane here.
So this is kind of what I've got going on. I've got this taped off so that this will get painted. I think I'm going to do all blue here and then I'm going to peel this off and it's going to have like white streaks through it. I think it'll be pretty cool. And you copy this onto the bottom side.
And then when I, after I paint the blue layer, I'm going to tape this off right here and put black tips on the tips there. And then I'm going to paint this black here as well. So I think it's going to be pretty cool in the end, pretty simple and we're going to see how it turns out. Hey, just finished building the plane and thought, this is going so well. Why not throw a coat of paint on there while I'm at it?
So I spent another few hours painting it. But hey, it's fine because everything's going so perfectly and it's going to be the best flying plane ever. Right? So I launched it for the first flight attempt and it knows I've straightened to the asphalt driveway. Great way to start a new build.
It's like we're at the move our center gravity a little bit and we're at the attach our battery a little bit better. So let's make some improvements and try this one more time. It's fine. I've come across this before. So I installed a better battery strap and get ready for flight two after adjusting the CG.
This time it doesn't crash immediately. So that's an improvement, but it's still nose diving a lot. It must be nose heavy, right? The plane is still intact. So I adjust the CG again and get it ready for flight three.
And this time it kind of blew. That gave me a little hope. Keep on going. But it was super pitching and very, very hard to control. We can technically call this one a flight, but barely.
Ouch. And I definitely need to work on those landings. It's like so pitchy. Well, we're going to have to look into that. That's why this is an experiment, guys.
Let's see what we can do to find out. Let's go get the wreckage. Oh, no. Well, there's a little bit of a damage there, but not too, too bad overall. I think it was a pretty hard hit.
So honestly, I was surprised how well it's intact. Okay, back to the drawing board. It's got to be a CG problem. I spent way more time trying to figure out where the CG should go than I would like to admit. And these are moments where you feel like you just hit rock bottom with a project.
You poured so much time into it and just can't get it to work. But the joy that comes in the morning when the sun finally rises on your project, that's what makes this all worth it. After several long conversations with our favorite virtual helper, ChadGPC, we determined the CG was way off. I adjusted it way forward. I gave more details about the wing shape.
And after even more back and forth, we decided the CG needs to be moved way back instead. At this point, I didn't even know what was going on. But I had to try something. So I moved the CG forward again. I ran the plane, pushed me into the air, and every time I released it, no zod right into my hand again.
So I moved the center of gravity back further. As you can see, my battery is way so backwards. So we're about seven and a half inches back from the leading edge of the wing, which is about halfway back, which seems crazy for the math. But I think maybe it'll work. Now the CG was basically right back where I started.
So we might as well try another flight again. And of course, something else had to go wrong. The motor and ESC I was using died. I guess we're trying again in the morning. Before the next flight, I swapped out the motor and ESC.
The only ESC I could find didn't have a built-in BEC, which meant it wouldn't power the receiver and servos. So I had to solder in a separate BEC and also solder connectors onto the motors. That was the whole thing. But finally, as the sun rose, I was ready for flight four. I pushed my center of gravity back further, and I also have a bunch of deflection on my elevators, all of them.
So hopefully that'll help get us in the air. It's time. Okay, it's flying. It didn't immediately crash, so good progress. Oh boy, okay.
That was a flight. But it still didn't last long. Another unstable crash. This plane was back on the ground, and I was back at square one. And electronics ripped off, so that's not ideal.
But it's all fixable. I was over it. I had tried everything, or at least it felt like I had. So I sat on it for the weekend, not literally, but I've been trying to think through this whole center of gravity problem, and I went online and did another calculator, and it said the center of gravity should be about where I had it in the beginning. So I'm not really sure that it's actually the center of gravity that's the problem.
I think more so of what's causing my problems here is the fact that we've got this weird under camber five inch section here that is throwing everything off. So I think what I want to do is I want to remove that. I want to take that and make it like go up or do something to make it so that it's not existing, causing problems. I stepped away and cleared my head and started thinking, remember, and I added more reselects to the elevons before it actually helped a little. I took a closer look at the wing and sure enough, there was this under camber section near the back.
They were acting like flaps. It made sense. They were forcing the nose down and destabilizing the plane. So I decided to tear the whole wing apart. I spread the trailing edge open and removed the unwanted camber.
Just maybe this was the thing that could push it over the edge from being a not very effective paperweight to becoming everything I've been dreamed of in RC Airpoint. So you can see I got our control surfaces all hooked back up. I added some reflex into them so that it actually just helps the plane to fly straight and do not pitch down. So that's kind of what we're going for. I'm really excited about this new flat bottom.
You can see that the air is going to come off of here and it's going to go straight onto the elevator, which is what we want. It's not really going to get to this surface here. So I think that'll be a lot, lot better. So we're going to see how it goes. I got to stick the motor back on here and then we can get our electronics tight up.
I'm going to do a quick paint job and get these fins back on. And I think I'm going to just see you out of the field. Alrighty, so we got the wing back out here and I got it all kind of put back together. Here we go. Flight attempt number five.
Let's see how it does in the air. That's what we're really here for. Well, that's not a good start. It's supposed to fly, but after a quick adjustment to the push rods to reduce the reflex of the elevons. Nice, nice, nice.
Yeah. It flies. Yes. And it flies pretty well too. I took it up through mistakes.
I trimmed it out and brought it back down for some blow passes. I wanted to do this gospel and flight section today to give you some encouragement. Sometimes these builds don't go how I planned crashes, bad CG or just things I didn't expect. But just like in life, perseverance matters. Galatians six nine says, let us not grow weary and doing good for the proper time.
We were really good. We were really good. We were really good. We were really good. We were really good.
We were really good. We were weary and doing good for the proper time. We were reparvest if we do not give up, whether it's flying or faith, just keep showing up and don't quit. How about some aerobatics? That was, well, the slowest roll I've ever seen in my life.
But hey, it worked. And most importantly, it flew really well. I'm so excited that it finally flew and even more excited how much I learned from this journey and how I can take those hard learning lessons and hopefully build my next flying wing with more confidence and maybe even get it right on the first try. Like and subscribe if you want to follow along with my RC journey and see more RC adventures. And I'll see you in the next one.
Adios. I'm sure it'll be fine, right?
