Intro: Homemade Aircraft for Under $1000 (FlugTag Style)
I am an Aerospace engineer and a pilot, and when the RedBull FlugTag came to my town, it was the perfect opportunity to put all my skill to use. This instructable walks you through the entire process of building your very own plane. You don't have to design it the same way we did, in fact just about anything will technically fly if you get it going fast enough. The aircraft described here is actually a Ground Effect Vehicle. This means that it's designed to fly a maximum of the wingspan from the ground. The advantages of this are that it's very safe, very slow and requires a very small power supply. If you live in the desert or anywhere near water then this is perfect. Add a bigger power plant and you can escape ground effect and go as high as your engine will allow you.
While you can source some of the materials form your local hardware store, others will be nearly impossible to source locally or they will cost you much more. You can probably build everything by yourself, but it's going to take even more time and most of the fun in this is the teamwork. We spent 3 months building the first version, but with this instructable, you should have a working plane in less than 160 hours of work. (That's about a month if you make do this full time by yourself.) Actual cost of the materials for the plan is about $500 but you might need some tools. Cost of the power plant can be $500 to $10,000 depending on how fast you want to go. Or just use it as a glider for free.
Step 1: Order Your Supplies
You're going to need several key items:
- 1" T6061-T6 Extruded Aluminum Tubing (Online Metals)
- 3/4 T6061-T6 Extruded Aluminum Rod (Online Metals)
- PIC Foam (Lowes or Home Depot)
- Rubbing Alcohol (Walmar)
- Gorilla Glue (Lowes or Home Depot)
- 3M 3050 Tape (Lowes or Home Depot)
- Loctite Spray Adhesive (Lowes or Home Depot)
- 4x8x1/4" Luan Plywood (Lowes or Home Depot)
- 3mm Lamination Film (Amazon)
- T-Rex Packing Tape (Walmart)
- Various nuts, bolts and screws that you can get at your local hardware store. (Lowes or Home Depot
For the tubing, you want T6061 extruded aluminum tubing. You can get 2024 since you don't need to weld anything but it's much more expensive. You can get thin wall, but it's more expensive. At $12.50 per 8' section this is the best value and it's insanely strong. https://www.onlinemetals.com/merchant.cfm?pid=2285...
For the foam, nothing comes close to PolyIsocyanurate board. It comes in 1/2" and up sizes but you want the 1/2" stuff. 2 sheet's glued together with Super 77 weight 20% more than a sheet of 1" but increase strength by 40%. The blue and pink stuff is just filler. It might be easy to cut, but it's flimsy and a waste. You want the silver coated stuff that is usually painted on one side.
Rubbing Alcohol (91%) is will remove that paint and make both sides shiny silver. This takes a few ounces off and also makes your aircraft look like it's made of all aluminum. Bonus!
Gorilla Glue is amazing stuff. It is actually very similar to the foam, expanding into every crevace and securely bonding all of your parts.
3M 3050 Tape is usually sold as air conditioning ducting tape, but this thin and lightweight tape puts duct tape to shame. It's easy to work with and super strong.
Loctite Spray adhesive is for laminating layers together. It's fast, strong, foam safe and easier to work with that Super 77.
The Luan plywood is thin, light, and flexible. When bonded to foam, it's incredibly strong.
3mm Lamination film will serve as your covering. You can use Monokote if you have an unlimited budget, but the clear film is easy to work with and is very strong. It's also easily patches with packing tape.
Packaging tape. To patch holes. You could use anything, but this is an airplane. Use the best.
There is very little hardware. Most of the plane is glued together but you'll want piercing 1 1/4" screws from home depot. A few pieces of 1 1/2" hurricane strap and maybe some screw eyes to run your control lines and tow connections.
Step 2: Gather Your Tools
- Heat Gun (Harbour Freight)
- Lamination Iron (Amazon)
- Razor Blades
- Hack saw
- Tape Measure
- Chalk Line
Yeah, you can get power tools and all sorts of fancy stuff, but we found that a simple razor blade was all you needed to cut the foam. And a Hack saw works just fine. If you have a Dremel tool or a disc sander, it might come in handy.
Step 3: Start Cutting
We spent about 200 hours on our plans, doing designing weights and balances to ensure everything was just right. Building models in CAD, printing them out and testing them. Use the template above to cut out your airfoils. You'll need 24 of them. We went with a heavy lifter airfoil that had a 12" chord and was 6' in length. Both the canard and the main wing used the same airfoil to simplify things. We found that making the airfoil out of luan and then using that as a template sped things up a lot. You can use a Dremel tool as well, but it makes a MESS. Be prepared with a mask if you intent to use power tools. For the leading edge, use a 8" wide piece of foam (that you should have leftover from each set of 6 ribs). For the trailing edge, you want a 12" wide piece. Your blocking pieces will be as per the plans. The canard and center section of the rear wing will match, but the wing extension will vary slightly.
Step 4: Assemble!
You could just put it together with all that painting on your foam board. But if you are willing to put in a little effort, it's worth it. We found that putting on a pair of gloves, getting a rag and putting a spray bottle head on a bottle of 91% isopropyl alcohol make quick work of this next step. Just spray down the foam, wait about 60 seconds and wipe off the paint with firm pressure. Cleanup with some paper towels and you'll have shiny aluminum board on both sides!
Once that cleaned up, you can start assembly. Test fit everything to ensure your spacing is right and that everything is square. Like a house, if you don't have a square foundation, your whole house is going to be crooked. In a house this means that your OCD might kick in, in a plane it means you'll fly crooked and crash. Spend the time to get this step right.
You can cut out everything at once, but unless you have an enormous shop, it's easiest to work with one section at a time. First you'l want to glue the leading and trailing edges on. Spray with water, coat with a very thin layer of glue (that stuff expands about 5:1), fit together and immediately cover with 3M 3050 tape. The tape keeps the glue in the joint, making for strong and good looking connections. After that dries in about 4 hours, put on the bottom aluminum tubing, but don't glue it in place yet. Then insert your blocking, adding water and gluing as you go. Wear gloves because that glue doesn't come off easily. I ruined several pairs of pants before I got good at it. As soon a you're done fitting it all together, tape everything up, then use clamps, straps or heavy weights to hold it all together as best you can.
Once all that is together you'll immediately notice that it's strong, REALLY strong. But it's about to get a whole lot stronger. You want to cover all foam edges with 3M 3050 tape. The main reason is that it will give your covering something strong to stick to, but it also makes the foam stronger and keeps out moisture. This is important, because the one main drawback of PIC over XPS (the pink foam) is that it's NOT waterproof. It will actually absorb a lot of moisture meaning that it will add weight and could mold or even rot. But it also just looks a lot better than un-taped seams.
Now that everything is taped you can build your fuselage. Cut and assemble as per the plans. You'll be attaching the fuselage to the wings with hurricane strap. This 1 1/2" wide galvanized steel is usually used to keep roofs from blowing away, but if you cut it into 8" section with a hack saw, sand it down, drill a few holes and it makes a very strong joint that can be easily adjusted and replaced if there if ever damage to the plane. We tried 3D printed connectors but they were heavier than the steel and not near as strong. Glue the fuselage together with the same water, glue and tape technique.
Step 5: Wiring and Power
At this point you have to make a decision. How are you going to use your aircraft? If this is a glider, then you can skip this step. If this is a lake flying ground effect machine then you can probably go electric only. If you want to fly to 1000' or higher, you're probably want to go with Gasoline Engines. You can do ducted fans, jets, maybe even Ionic propulsion. At this point that bit of engineering is up to you as it is outside the scope of this instructable and I'm testing various thrust systems right now. We pulled it behind a boat and a quad, even an electric scooter. It glided down hills and ultimately won us the RedBull Flugtag so you know it actually flies. But how you power yours is up to you.
Step 6: Cover It
Now that everything is together it's time for the covering. This is probably the most tedious process and you'll probably space this out over several sessions. If you do this during the winter, you'll be much more comfortable because it makes a LOT of heat.
Wrap the coating over the entire wing from trailing edge over the leading edge and back again. Use a bit of packing tape to hold things tight. Then use your heating iron to adhere one side to the rib pull tight and then seam the other side. The tighter you get it, the less work you'll have to do with the head gun later. You want each seam to overlap the rib, going down and seaming the excess to the rib itself when you can and overlapping the next rib by about and inch. The film will stick well to itself, just go slow and ensure it turns completely clear to know that you have it hot enough.
Once the plane is completely covered, or each section if you want, then you can start shrinking. There are cheap heatguns and there are good heatguns. If you want to burn 1000 little holes in your plane and patch them with packing tape, go for the cheap one. Or spend $30 and get a good one. The lamination film turns clear at 300 F and you'll put a whole through it at 340 F. It takes about 100ms for that to happen. Go slow, keep the gun about 8-12 inches away, at an angle and turn the heat to about 750F with the fan on high. This will give you plenty of time not to burn through. But you probably still will burn a few holes. Just be patient, you can keep shrinking so just let it cool and keep going back over it until it's tight. It will get drum tight and perfectly clear when you are done. You also will probably warp your wing in the process, but you can fix that later. You can patch the holes with more film but the T-Rex tape is fast and strong.Once you're done it will look like a plane!
Step 7: Final Assembly Touches
Now you have to put it all together. You'll use 3/4 in step bit with an extension to drill 4" into each end of the main wing center section and the two wing extension. Wallow it out well by moving the bit around. Then cut the 3/4" solid rod into 7 1/2" pieces. Fit the sold rod into the 1" tubing. It should insert smoothly. If it's not easy to put the rods in and out, then keep drilling and moving the bit around to widen the hole.
You add the winglets and rudder, bolting them on as per the plan. Then the rudders install between the wing extension and the main wings. Put the rods in and drill a 1/8" hole through the tubing and rod. (Try no to poke and holes in your plane while you're at it!) Then put a 1 1/4" screw into each hole to keep everything together.
Square it up, check your angles and use the heat gun to shrink and straighten out anything. This process can take a while so be patient. You now have a working aircraft!
Step 8: Go Fly!
OK, at last you can find out if all your hard work was worth it. You should have a aircraft that weighs around 120 lbs plug engine and landing gear. We started out testing behind a boat but that was a total failure. We then put it on another boat, used 2' leads tied to all 4 corners and pull the plane with a 2nd boat. That worked great and we found that 18 mph was the perfect speed to lift a person and plane into the air. But the real success came with the zip line. We used a 3/16" galvanized steel aircraft cable pulled between two trees across my lawn for 275' at a 6 degree angle. Using turnbuckles we go the line as tight as possible. Connecting the plane to two pulley and the pilot to 1, we were able to perform repeated tests in a safe and controlled way.
Adding wheels we rolled it off hills with just a sandbag in it and had good results. Just make sure that you have solid landing gear or water under you. Our aircraft yielded a 3:1 glide ratio pulling off 81' from a 25' fall in the 2017 RedBull Flugtag. Maybe you can do better? I know we're going to keep trying!
You can read more a tnflugtag.com and follow our us on Facebook at @tnflugtag.com
I'm working on making a complete build process video but it's going to take a while to compile several hundred hours of footage. You can see a lot of stuff on Facebook at @tnflugtag or tnflugtag.com A highlights reel and a complete build video are forthcoming.
This was an early testing video: https://www.facebook.com/tnflugtag/videos/140558703197331/
The notorious lake crash: https://www.youtube.com/watch?v=_Hx-dwXilTY&t=9s
Zipline Testing: https://www.youtube.com/watch?v=5b5VmThmSuE
Just our flight: https://www.facebook.com/tara.holancinhart/videos/10214275566030003/
The official RB video: https://www.youtube.com/watch?v=dppeL1F9oA4