Week 2 of building a 20-foot foam cargo plane for aerial combat at Flite Fest. The elevators got finished, the tail learned to come apart for transport, the wing grew 27 laser-cut ribs and aluminum joiners, the nose got a quick-release latch, and the landing gear got custom 12-inch tires. By the end of the week the pile of disconnected foam finally looks like an airplane — and the weight estimate leaves almost no room to finish it under the 55-pound combat limit.
Flite Fest combat has a strict weight limit, and a 20-foot foam plane eats that budget terrifyingly fast. Every decision this week — how the tail joins, how the ribs are cut, what the joiners are made of — happens in the shadow of that number. It's why parts keep getting ovals cut out of their middles, and why "strong enough" always has to be weighed, literally, against "light enough."
The elevators on this thing are enormous, and they hinge into wood hardpoints glued into the foam so the hinges have something solid to bite. That part of the plan worked. What didn't: one side of the tail had wood exactly where the hinge pockets needed to go, and the Dremel couldn't reach deep enough to clear it. After a lot of unproductive carving, an oscillating saw solved in seconds what the rotary tool couldn't do at all — beveled the wood, seated every hinge cleanly. Lesson worth stealing: on big builds, hinge-line problems are tool-reach problems.
A 20-foot airplane doesn't fit in anything, so the tail was redesigned to be removable: a custom plywood-and-foam insert epoxied into the structure, a central rib, and 3 mm pins passing through wood blocks with collets so the horizontal and vertical tail lock together and can't pull apart in flight. The insert itself got an oval hollowed out of the middle — keep the load paths, lose the grams. That's the whole build philosophy in one part.
The wing panels join through a box spar — layers of wood forming a box that captures a removable aluminum tube set at an angle, which is what gives the wing its dihedral. This is the part of the plane where a failure would be catastrophic, and it got treated that way. It also produced the scariest moment of the week: Gorilla Glue expanding in the box very nearly locked the removable joiner tube in permanently. It came free. One side now slides in and out easily and sits rigid with barely any play; the other is tighter than it should be and gets more fitting work before the wing is trusted.
This week is also where the new CO₂ laser cutter (provided by OMTech — disclosure below) went from unboxed to indispensable. The difference from the little diode laser is night and day: where the diode dug divots and left edges that weren't usable for structure, the CO₂ machine cuts pink insulation foam and foam board cleanly in a single pass. That's what made 27 weight-relieved wing ribs practical — every one precise, every one lightened with cutouts, produced in batches instead of traced and knifed by hand. On a build where every part has to be both strong and light, precision fabrication isn't a luxury; it's how you stay under 55 pounds.
The nose has to come off for transport too, and a fistful of bolts at the field gets old immediately. The fix: printed hook latches — a hook that passes through an inch of foam and locks the nose in place, click-on click-off. The proof-of-concept worked well enough that four of them are going on the final airplane.
A plane this size needs landing gear from another category of aircraft. The answer was to 3D-print custom 12-inch tires (printed on the Bambu Lab H2D, along with the build's bolts and wing nuts). When the airframe outgrows the hobby supply chain, the printer becomes the parts shop.
End of Week 2: the disconnected foam pieces finally assemble into something that is recognizably an airplane. The wing structure is mostly glued together — but it isn't skinned yet, the systems aren't in, and the weight estimate says the remaining budget under the combat limit is razor thin. Skinning the wing, finishing the systems, and the Flite Fest attempt are next — with about two weeks left on the clock.
Disclosure: OMTech provided the laser cutter featured in this video. Hot Wire Foam Factory provided the cordless hot knife and StyroGoo adhesive. Some links are affiliate links — they cost you nothing and support the builds.
| OMTech Maker AF2028-80 CO₂ laser · sponsor-provided | The machine behind the 27 ribs — cuts foam and thin ply cleanly in one pass. omtech.com/ERICROBBRC — code ERICROBBRC for 5% off. |
| Bambu Lab H2D | Printed the 12-inch tires, bolts, and wing nuts. Bambu Lab store · models on MakerWorld. |
| Hot Wire Foam Factory cordless hot knife · sponsor-provided | Clean freehand cuts in EPS foam. hotwirefoamfactory.com |
| StyroGoo foam adhesive · sponsor-provided | Instant-tack grab for foam-to-foam joints. hotwirefoamfactory.com |
Shopping for your own workshop? My tested picks — including laser cutters and 3D printers for RC work — are in the gear guide.
Nothing to correct yet — this write-up matches the video, and the build is still moving. The wing skinning, the finished systems, and the Flite Fest combat attempt land in the next episode. 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 crawling into a massive RC airplane because five days ago this was a giant foam tube and now it's becoming a 20 foot airplane. But it has to survive RC combat, come apart and fit into my truck and stay under 55 pounds or it can't even fly it quite fast. At this size simple parts became problems. Every fix added more weight. When I added it all up I realized I was almost overweight and the first warning started at the tail.
I am having a terrible time trying to put these hinges in here. And to understand why this became such a mess we need to go back in time. The elevator is a large moving flap on the back of the tail. When it moves the controls if the nose goes up or down and on something as large I can't trust that connection to foam alone. They need some solid wood to hold onto.
My original plan was to glue a long strip of wood along the back edge of the trail and cut the hinge slots directly into it. But when I lined up the elevator I realized I had installed that strip too low. The hinges would barely reach the wood. The easy solution would have been to add another large piece of wood above it but just picking it up the tail already was getting kind of heavy. An airplane balances somewhat like a seesaw around the wing.
So the more weight I added to tail the more weight I have to add to the front just to balance it. That means a little unnecessary weight in the tail can eventually cost me. So instead of adding more wood I cut off the original oversized strip and replaced it with a smaller piece mounted higher directly behind the hinge line. That put the strength exactly where the hinge needs it while removing material elsewhere. The hard point was finally in the correct position but I still had to cut a deep straight slot into that wood without destroying the surrounding foam.
I finally struggled and got all those in but these ones here are just driving me crazy. The dremel seemed to work fine at first but the cutting wheel is not that big and it's not able to get deep enough. Oh this is a magic tool right here. I don't know why I didn't try this sooner. And now that we've got that figured out the elevator is looking great so hopefully now we can control this airplane.
Hopefully we can control it well so it doesn't crash into the ground. We wanted to crash into all your airplanes. I'm building this airplane for Flightfest, a four day RC flying festival where people bring everything from small foam airplanes to ridiculous giant projects like this one. And one of the biggest events is a massive aerial combat. This year Flightfest is happening August 6th through 9th in Dayton, Ohio and I hope to see some of you there.
I'll leave a link in the description if you want some more info about it. But before this airplane can survive combat I actually have to get it to date and that means designing the entire plane so I can disassemble it and put it in the back of my truck. That creates a problem with the tail. Permanently gluing everything together would be simple and strong but the complicated tail would be far too large to transport. So the upright part of the tail had to be strong enough to fly, light enough to protect the weight budget and removable enough to fit in the truck.
Set the big rudder on there. This thing looks amazing but I'm deciding how exactly I want to fasten this thing on there. Permanently gluing this vertical stabilizer would have been lighter and simple but it also made the airplane significantly harder to transport. My first idea used Origer Aluminum Tube. Instead I cut a plywood tongue.
Most of the unnecessary center material was removed. The remaining wood carries the load into the horizontal stabilizer while too small steel pins stop the vertical stabilizer from lifting out. And now that I got that figured out it's finally time to start building the wings. The only problem was the wing needed 27 nearly identical ribs. Cutting them all accurately by hand would have taken days and a small error refuted across the wing could distort the entire airplane.
Each way Omtech stepped up in a huge way and sent me over one of their laser cutters. Unfortunately the freight company delayed the shipment after it arrived at a freight terminal an hour away. I decided just to go pick it up myself from there which got to here about a week earlier than scheduled. Hey dear! Oh that's packaging!
Wow not that big of a vehicle. Nope. I'll take you really light. It works! I love it.
Look how clean that is. Now we finally have the last piece of the puzzle that we needed to get this plane in the skies. Oh I love it. It looks perfect. Editor Eric here.
If you're enjoying this video so far it would mean a lot to me if you would hit that subscribe button. I'm trying to hit 100,000 subscribers by the end of the year. I know that's a crazy goal but you guys are awesome. Let's get back to the build. Okay well I think that is the rest of our ribs there.
They look beautiful. This machine does an amazing job. That accuracy meant I could go directly from the airfoil file to repeatable foam parts instead of trying to reproduce every rib by hand. This machine did not just make these ribs cleaner. It made it realistic to finish the swing before flight fell.
And this thing really is a beast with 90 watts of CO2 laser power autofocus in a huge 20 by 28 inch working area and a pass through for oversight projects that I use all the time. Basically everything I need to start manufacturing airplane parts instead of cutting them by hand. And if you've been considering upping your manufacturing game, home techs have a fantastic brand to work with and they make awesome laser cutters. Go check out my link in the description. You use my promo code ericroprc where you can get 5% off your purchase.
You support me along the way. You can see I cut out a little oval here in the middle so that it's strong but it's a lot lighter. Really trying to keep the weight down on this plane. And removing the center from one rib saved very little but repeating that decision 27 times was exactly how this airplane would have to stay light. But you remember the whole transportation problem?
Yeah that one. The completed wing couldn't stay 20 feet wide. So the wing had to separate into three pieces just to leave the garage. That meant the outer six foot panels need removable joiners strong enough to carry the airplane. Carbon fiber tubes would have saved weight but the material I could have tamed before flight festivals were aluminum.
The joiners alone added 3.6 panels. Therefore I built plywood receiver boxes around the aluminum. It's pretty solid. Filled only the spaces needed to stop the tubes from moving or crushing the foam. The fit had to be tight enough to prevent wing movement but loose enough that I could still remove the outer panels.
The question is going to be can I actually slide this bar out or did I accidentally glue it in place? Oh wow nice It's time! It's finally time the moment we've all been waiting for building the wing assembly. We're both upside down. Okay off to a great start.
The spars and aluminum joiners carry most of the bending load. The ribs hold the airfoil shape. That meant the ribs could remain thin and hollow. But the real question is will the wing stay square while the entire structure is assembled? So the glue that I used for this is actually some styro-goo from Hotwire phone factory.
It's got a zero second instant grab so I don't have to clamp anything down. It's honestly been fantastic. And after days of designing cutting individual pieces on the laser cutter, the spars finally looked like a wing. And before we get to building a nose that's easy to assemble in the field and secure at the same time. I've been organizing everything from this build at my website ericrobrc.com.
Check it out in the link in the description below. The tools, materials, weight breakdown, build notes, and files I'm able to share. This site also has free RC guides and tools along with products I designed and sell. I love this hobby and I want to do everything I can to share it with you guys and help you guys get started as easy as possible. So I've tried to organize parts and materials and tools that you'll need to have a good experience the first time.
Anything you purchase through my website helps me out so I really appreciate it. So go check that out and let's get this nose attached. So there it is right there. There's our nose. It's looking fantastic.
Originally thinking we'd take a bolt and put it through right here. I don't really want to have to be unscrewing these bolts all the time. The nose had to remain removable because the fusage already barely fit into the truck. The first plan required more hardware and more field assembly than I wanted. My bamboo lab 3D printer let me test the bolt idea immediately instead of waiting for custom hardware.
It's so nice to be able to manufacture stuff like this. It's just as easy as searching for a simple bolt design on Makerworld, dragging it into the slicer, hitting print, and it'll send it off to the printer to be printed. The first prototype proved the concept would work but it also showed me if there was a simpler solution. So I switched over to the laser cutting module on my H2D and cut out this simple interlocking plate design. I replaced the large bolts with interlocking wood plates.
The nose could slide down into place and use a much smaller secondary latch to keep it from looking back out. That reduced the hardware, aligned the nose automatically, and made installation much faster. We are reporting live from inside of the airplane. I take these parts that I just cut out on the laser cutter. We're going to glue them in place right here on the four corners and that's going to be my mounting positions for the nose.
I got the wood supports glued in up there but I need a way to accurately cut it out. Thankfully my new friends over at Hotwire phone factory hooked me up this week with their cordless industrial hot knife. See how I can cut through this foam. Wow, that thing looks great. Well, that thing works fantastic.
If you want one for yourself, I've got it linked in the description below. I had to open the garage door to clamp the front nose on because it's a little tight in here. This airplane is huge. The airplane now had most of its major structure but it still could not stand on its own. The landing gear needed to support more than 50 pounds, absorb a rough grass landing, and add a little weight as possible.
Since I could not buy a 12-inch foam tire with the exact firmness that I needed for this airplane, I printed one on my Bambu Lab H2D. I just printed them at H2D, just finished. Look at that, looks amazing. The biggest advantage was not merely making the tire, it was being able to change the design and test another version immediately. I printed three versions until I found one soft enough to absorb a landing without collapsing under the airplane.
This was V1, the top one, and then this is V2 and this is V3. Now that we've got the tires all figured out, we need to decide how we're going to attach the tires to the airplane. I bent some aluminum flat bar around the wheel, added a tubular axle. The design stayed in intentionally simple. Every extra brace could make it stronger, but it would also spend more of the weight needed to finish the wing.
Five days earlier, these were disconnected pieces spread across the shock. Now the airplane has working elevators, removable tail surfaces, landing gear, a removable nose, and a structure of a 20-foot wing. It was the most progress I had made since the project began, but every one of those victories has spent a part of that same 55 pound budget. Until this point, I had been weighing individual pieces and trying to keep every design light, but I had not stopped to total the completed structure and all the equipment the airplane requires. 52.6 pounds.
That means we have 2.4 pounds left for the rest of the build, but the outer wings still need ribs, skin, four motor nacelles, wiring, control hardware, cargo doors, there's a lot to add here. But there are obvious places to save weight. Smaller batteries help, but they also cut available capacity significantly. Fiber gas protection can disappear, paints, maybe a thing of the past. Those changes help, but they do not solve the whole problem.
The nacelles now have to be minimal. Every gloopy matters. Even large sections of the fusage may need to be removed from areas that do not carry meaningful loads. The problem is that every pound removed also reduces something, strength, durability, battery capacity, or protection in combat. I spent this entire week adding parts to make this an airplane.
Now I have to decide which parts I can remove. Because if I cross 55 pounds, none of this gets to fly at play fast. The next challenge is removing enough airplane to finish it without removing the parts that make it fly.
