Aluminum Structure RC Plane


Elite member
The title basically says it all; I want to build an RC airplane completely out of aluminum. At first glance, the idea seems reasonable. Real airplanes are made out of aluminum on a regular basis. However, if you look at it more closely, a few big problems appear. First, aluminum is dense. While it has a strength to weight ratio similar to balsa, it is much thinner making it highly prone to buckling. It is also less rigid. Second, it blocks radio signals. Third, it is hard to find aluminum that is thin enough to use in an RC plane but still in structural shapes like tubes or I-beams and when you do find it, it is very expensive. A few people have built working RC planes from aluminum, but they have largely been big and heavy or used a hybrid structure with aluminum and another material. Yesterday, I came up with a solution to the third problem I listed, and I don't think the first two problems are insurmountable. That solution is aluminum foil and a battery spot welder.

The frame in the picture is completely made from aluminum foil of the type that might be found at a Dollar Store or any other grocery store. The members are aluminum tubes made by spot welding aluminum foil wrapped around a dowel and then joined using spot welding. The frame is for a high wing single engine airplane similar to a Piper Cub or Aeronca Champ with a 35" wingspan (you can see my hand for scale). The aluminum tubes are a bit heavier and a bit weaker than balsa of the same size and are especially weak in bending but are definitely usable for an RC model. The full frame weighs in at 18 grams right now, which is definitely acceptable. One point of concern is the joints at the corners of the tubes. These are fairly brittle, but I don't think they are much weaker than the CA joints in a balsa model, so I think they fit with the theme of this technique being similar to but a bit worse than balsa in terms of strength. And one benefit of the technique is that it is pretty quick and easy. It takes some practice to reliably get the spot-welded joints, but once I got it down, it only took me a couple of hours to do this.

The picture above shows how I made the tube by wrapping aluminum foil around a dowel, clipping it, and then spot welding it in place.

Therefore, the remaining problem is how to leave the receiver unshielded. I have read on a couple of places, that thin aluminum doesn't block enough radio signal to cause problems when working with modern receivers, so I may try a shielded range test first just to see, but I think my best bet is a 3D printed fairing out the bottom of the aircraft where I can put the receiver. Another concern is fatigue. Aluminum is prone to becoming brittle and cracking after many loading cycles, and especially in the already brittle joints, this could quickly lead to failure. However, I think I should hopefully get a couple flights out of it, if it works at all, and after that I can happily retire it as one of the crazier things I have tried to do. If this technique produces a usable product, then I will probably want to try to build more airplanes using it, just for the cool factor, so to make the joints last longer they could additionally be reinforced with epoxy after welding and at that point they would probably outlast the rest of the plane.