I broke out my TIG the other day and did some 'braze welding' with some bronze rods (not to be confused with 'brazing', stupid British English).Oxy Acetylene if on a tight budget; TIG is you can spurge on tools. No MIG, No MIG, No MIG. OA is the classic way.
While I readily admit that I am far from being an expert welder, I have found that its often difficult to get the beautiful weld I always want with a Mig. What I have found is that if you are going to be welding the same thickness of material continually, you will find a setting that lets you weld consistenly. When welding things with different thickness (or extra mass) I try to make my torch place most of the heat in the dominent part and move it as if I'm spreading from the thicker part to the thinner part. In other words, most of the heat is applied to the thick part and a quick weave to the thin part. Even with clusters, due to the thin nature of the material, I would think that only a slight adjustment would be necessary. Obviously anyone wanting to weld this way should make a few similar clusters to practice on before going for the real finished product. Once someone has set their machine up for the thin material, I think they would have minimal problems with making repetitive quality welds. Again, as you mentioned, TIG provides the ability to adjust on the fly while making a weld. OA applies a lot of heat to a large area in order to weld, and may have an effect on material strength after it cools........but there doesn't seem to be any problems caused by doing so.I know Champion, like Citabrias, Decathalons, and Kitfox use MIG. They also had a big learning curve because for years the welds would crack until they perfected the process. Each cluster takes a precise amperage; not a generic get it done amp. One extra tube, one tube thickness change, one diamiter change and it will not weld through to aviation standards. It will look pretty, but be as strong as mud. If you can come up with the perfect amperage everywhere, go for it. With the TIG you can see it in action and that is why you play the foot pedal. Being electric, TIG has the same amperage problems but you can adjust in the fly. Nothing wrong with OA; there will always be more airplanes flying out there with OA. Crush all the rag and tube airplanes including every homebuilt before the 80's and the others might have a chance.
Heat control surely seems easier with the TIG (foot-throttle) with a smidgeon of practice – no doubt about it, and there is a fair amount of carry-over from OA skills… What little I know about `lectronic welding I learned (if you can call it that) stick welding on the old Lincoln buzz-boxes a gazillion years ago – all my boyhood friends grew up on farms and knew how to run a bead before they were out of diapers (I was from town and was always envious).I try to make my torch place most of the heat in the dominent part and move it as if I'm spreading from the thicker part to the thinner part. In other words, most of the heat is applied to the thick part and a quick weave to the thin part. Even with clusters, due to the thin nature of the material, I would think that only a slight adjustment would be necessary...
Going to Oshkosh and already planning on doing that, thanksIf you go to Oshkosh, you can try both OA and TIG, and see what you like. At some point, you will need a torch for heating / bending tube and fittings, so consider that aspect. At Oshkosh, you will also be able to get some experience with wood work, sheet metal work, fabric work and composite work.
Many certified aircraft have been built with TIG without "stress relieving" or "normalizing" the welds.
If you buy OA, be certain that it is an aircraft torch. I have a Victor OA aircraft torch, but an old Smith is really nice.