Brodhead Pietenpol Association

Original Posted By: "David B. Schober"
Mike;Thanks for the quick response. I was aware of the heat zoneand considering the wall thickness involved did not think itwas a issue. I also do not think there are any criticalwelded pieces in the wood frame. Several are formed, thewelding tends to be on the landing gear and tail wheel as Irecall. As I recall, 4130 (Chrome Molly as we called it)tends to work harden, I will pull out my reference books andreview. When you say "gas outfit", are you talking stick orbrazing? Sounds like brazing from the "dying skill" remarkas I agree. My understanding of of stick versus wire feedis with stick you will have to go small diameter due to wallthickness, as a result your stick are shorter and you haveto feed the stringer more. This causes the work surface tohave more "heat /cool" cycles. With wire you tend to havecontinuous heat, the heat spreads over the area more andless stress. Sounds like we are entering the "everyone hasa bellybutton..." (or pick your orifice) arena. I amafraid there will be as many experts on one side versus theother. Personally, if I see a piece is critical from astructural point of view, I will have NDE performed on it.I do not wish to be falling from the sky thinking "... thatwas too much porosity" or " ...t I should make a secondpass"Thanks for your comments, I realize it's my decision and Iappreciate all the information, it gives me more to digest.Bill________________________________________________________________________________

Original Posted By: jmcnarry(at)techplus.com (John McNarry)
I own a gas welding outfit. Traditionally, this kind of equipment has beenused for many years to weld 4130 tubing for aircraft. It works. Gas weldingis also somewhat of a dying skill, with the advent of wire-feed welding.There is a letter from someone apparently knowledgeable in the latest issueof Sport Aviation about wire-feed versus gas welding, in response to anarticle written about the subject in a previous issue. It is worth reading,because it makes good sense.Of great concern to many people is that wire-feed welding doesn't produce aswide a heated zone on each side of the weld, possibly causing more potentialfor metal cracking, because of the affect of changing temper on the steel'scarbon content. The letter's response is very good and very well informed.You must make your own decision, but do it from an informed standpoint. Getcurrent information from truly informed sources about welding 4130 andpotential for heat-affected zones (HAZ). In my opinion (and this is ONLY myopinion) wire-feed welding is just as good as gas, and probably easier tolearn. Just learn to do it right, by practicing on pieces of the SAMEmaterial.I am not a welding expert, only a manufacturing engineer. I'll be welding aWag-a-Bond airframe down the road, but I will probably use my existing gasequipment, since I have it and don't particularly feel like spending moneyfor more welding equipment. The woodwork on the wings comes first, though.This is my opinion, and worth just what you paid for it. Hope it makes youthink, though.Regards,MikePS: I have the same kind of boss, who also notices things like expenditureson airplane parts and services. I used to own a Tri-Pacer, but soon realizedthat if I wanted to completely own my own airplane, I'd have to build it!________________________________________________________________________________

Original Posted By: Martin Montague
Well, just one more man's opinion on gas welding vs. stick welding. I personally would prefer to use gas. If a guy were to use a stick welder (or wire feed welder), I would think you would want to use a torch afterward to heat up the surrounding area anyway so as to stress relieve the weld and the adjacent metal. As long as you are going to heat the area up with the torch why not just gas weld it in the first place? Call me a traditionalist, but I firmly believe there's a reason why gas welding has been the standard for aircraft work for a gazillion years. (I have friends who consider me an old fogey and just love their new wire feed welders, but their haunches aren't hanging on the results like mine).Jim K________________________________________________________________________________