Tig Welding vs Oxygen & Acetelene

I'm setting on a boat in the Gulf of Mexico, surveying for an offshore oil company. I don't have much to do for most of a 12 hr shift except read this forum. Like I said in my first post I'm about to start building a J3 with a Rotec R2800 on it. I've ordered the Wag Aero plans and the North Land CD with all of those neat drawing. I picked the J3 config 'cause I would like to be able to keep the empty wt under the 890 lbs allowed for a 115 HP engine under the ELSA rule (as I understand 'em) Want to go that route so I can operate it under a LSA ticket and fly without a doctor's permission, I aint sick but I don"t like doctors in general though they are alot more useful than lawyers. Like I said before I have put a 10% deposit on the R2800 and don't intend to spend much more 'till that little jewel is paid for and safe inside of my garage. To sort of get the ball rolling, so to speak, I believe I will go see if the Earle M. Jorgensen Company folks in Dallas (I heard about them here) will sell me enough 4130 for me to build some tail feathers. I was a welder a few decades ago before I found plumb bob beside the road and decided to find out what it was good for. I have a Heli Arc machine and an Oxy/Acetelene rig. I'm a little rusty with both of them. I've believe I could put a better weld on with the TIG but I read somewhere that it won't get the joint hot enough to normalize the metal and stress relieve it. The Legend Cub site has some pictures of them fabricating with a TIG but all of the other pictures of construction that I've looked at seem to be gas welded projects. Most of my questions in the first post I've found addressed in one forum or another in this fine web site; in fact I have just about doubled or maybe tripled my knowlege of Cubs by reading stuff here, but I dont find much talk about welding. Let me hear what some of y'all think.

Been discussed a lot. I did a search and found this one.


http://www.supercub.org/phpbb2/viewtopic.php?t=12006&highlight=mig+tig

Seacrane,

You've probably seen this picture on the Rotec site http://www.rotecradialengines.com/0Toby/collectorring.htm. I too was interested in a Rotec powered Cub project once upon a time. There were a number of cool looking tandem radial planes in the 20's and 30's.

I came to realize that a bunch of modification would be necessary to use the Rotec on the Cub frame. Notice in the picture how the engine mount moves the engine UP significantly. This tends to put the engine more in the way of vision (I Know! Radials are always in the way. :lol: ). This mount design just didn't seem as strong as one mounted directly in line with the frame mounting bolts.

Also people seem to recently be having better success with LOWERING the center of thrust compared to the longitudnal axis of the plane.

As to weight and E-LSA, I would NOT build the airplane to be registered as an LSA. Build as a amature built experimental and list the gross weight as, say, 1300lbs. Now you have a plane that you can legally do the maintenance and inspections on (experimental) and by your designation meets the maximum weight requirement to be flown as an LSA (but doesn't have to meet the ~890lb empty weight requirement).

John Scott

experimental cubs

Just had a friend go down in a ch-701 with a rotec r2800 on the nose. Prop stopped but the engine kept running. very low time engine. buyer beware, experimental means experimental! (He and the owner walked away).
Tom

one thing I've always wondered when seeing people build J-3 or PA-11's from scratch is: Why do they keep putting that headache bar in the front??
Why not move the wing spars out like the Super Cub. Makes so much better visibility.

OK so that wasn't your question. So to answer your question, I'd use oxy and put the front attach points for the spars outboard while using it. (cause I don't know how to tig and I dont like the headache bar.

You'd like it Brian, lot easier the oxy/acet. Did you get yours modified?

Back in high school I won a competion (oxy/acet, stick, tig & cutting/fitting) amoung other schools and was awarded a scholarship to a local votec school for welding, this started my "curse" as a "welder" . (welding is neat when done in moderation.....however I don't recomend it to anyone as a full time occupation)
Fast forward 30+ years and I haven't used the old tried & true oxy/acet torch for many years. However I have welded everything from airplanes frames,race cars, LOTS of pipe (amonia-refer) w/ a TIG root pass, boats- even trash dumpsters with a TIG.
There is nothing wrong w/ using a flame, heck.. it worked fine for many years. However folks that tell you, or really believe, a TIG is not worthy simply don't know what they're talking about. For what its worth, all the NICE new frames, tail feathers, gear legs, and other neat airplane parts that come from Big Lake Alaska are all welded w/ a TIG.....

Use what you are most skilled at. I repaired a Taylorcraft fuselage recently for an old guy that didn't want my Tig anywhere near his airplane.I use Tig most of the time but I do enjoy gas welding to keep current on it. Just look at old Pipers, they did a beautiful job on their work.This question is like asking what should you look for in a woman.

I seem to recall back in the seventies, that TIG was not approved for airframes because the temperature contrast across the weld was thought to produce microcracks along the periphery of the weld....it eventually boiled down to preheat if the steel was cooler than room temp....any thoughts on this? My memory is considerably less than reliable....been using a TIG, just preheat every time....

It's 03:30 and I'm back in the survey shack, seas are coming up. Thanks everybody for the opinions and for the links. I think I'm gonna use a little of both welding techniques. Probably stick with gas for the tube to tube structural stuff and use TIG on the tabs and plate re -enforced fitting.
John Scott, your advice is well noted. I'm still a little fuzzy on the FAA regs about homebuilts and I've been pretty concerned about how I was gonna meet the E-LSA weight limit with an engine about 50 lbs heavier than a C65 and at the same time add wing tanks and maybe flaps. I'll study up on this some more but what I understand you to be saying is that the builder declares the gross weight for an Experimental and that any plane meeting the LSA gross weight and max speed requirements can be operated by an LSA rated pilot whether the plane is certified as an LSA or not. I know the R2800 is kinda new and untried but everything would be untried if nobody ever tried it. It probably wouldn't be too good for flying over them trackless Alaskan forests but East Texas has as lot of hay meadows. Besides it will look cool and if looks wasn't important then more people would be flying Aeronca C3 s and Ingred Bergman woulda
been a waitress.

John Andrews

Steve Pierce said:

You'd like it Brian, lot easier the oxy/acet. Did you get yours modified?

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Trent's is over at W Mackey's waiting for fabric, and mine is still sitting in the jig with the new top deck tack welded on. too may other projects ahead of it.

Seacrane said:

John Scott, your advice is well noted. I'm still a little fuzzy on the FAA regs about homebuilts and I've been pretty concerned about how I was gonna meet the E-LSA weight limit with an engine about 50 lbs heavier than a C65 and at the same time add wing tanks and maybe flaps. I'll study up on this some more but what I understand you to be saying is that the builder declares the gross weight for an Experimental and that any plane meeting the LSA gross weight and max speed requirements can be operated by an LSA rated pilot whether the plane is certified as an LSA or not.
John Andrews

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John,

My understanding from the FAA if you are building an airplane is:

If you declare the airplane LSA (or E-LSA) you are bound by the LSA rules - including the empty weight issue and a requirement to attend a 40 hour course on maintenance before you can work on it.

If the airplane is declared an armature built experimental that you happen to set the limitations on from the beginning (gross weight, etc.) that happen to comply with the LSA limitations, you can operate this airplane as a Sport Pilot. There is no requirement about empty weight (other than practical limits) and if you build the airplane you can get the authority right off the bat to maintain the airplane.

As far as practical limits go you would need to think carefully about what you put in the airplane. Makes no sense to build a plane within the LSA weight limit (1320lb wheels) that has an empty weight of 1200lbs. I don't know you, but surely you weigh more than 90lbs? :lol: Even if you do weigh 90, 5 gallons of gas won't get you far!

Weight control seems to be a critical issue with LSA/Sport Pilot to remain legal.

John Scott

Longwinglover said:

Seacrane said:

John Scott, your advice is well noted. I'm still a little fuzzy on the FAA regs about homebuilts and I've been pretty concerned about how I was gonna meet the E-LSA weight limit with an engine about 50 lbs heavier than a C65 and at the same time add wing tanks and maybe flaps. I'll study up on this some more but what I understand you to be saying is that the builder declares the gross weight for an Experimental and that any plane meeting the LSA gross weight and max speed requirements can be operated by an LSA rated pilot whether the plane is certified as an LSA or not.
John Andrews

Click to expand...

John,

My understanding from the FAA if you are building an airplane is:

If you declare the airplane LSA (or E-LSA) you are bound by the LSA rules - including the empty weight issue and a requirement to attend a 40 hour course on maintenance before you can work on it.

If the airplane is declared an armature built experimental that you happen to set the limitations on from the beginning (gross weight, etc.) that happen to comply with the LSA limitations, you can operate this airplane as a Sport Pilot. There is no requirement about empty weight (other than practical limits) and if you build the airplane you can get the authority right off the bat to maintain the airplane.

As far as practical limits go you would need to think carefully about what you put in the airplane. Makes no sense to build a plane within the LSA weight limit (1320lb wheels) that has an empty weight of 1200lbs. I don't know you, but surely you weigh more than 90lbs? :lol: Even if you do weigh 90, 5 gallons of gas won't get you far!

Weight control seems to be a critical issue with LSA/Sport Pilot to remain legal.

John Scott

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If you do ELSA I think you need to decide on the project now if you want it to weigh more than the weight as listed in the specs., essentially so you are grandfathered in. Read through the thread on LAS weight, it is in there somewhere.

Tim

If the aircraft is an Amateur Built, (ie NOT an E-SLA kit), then it will be licensed as Experimental-Amateur Built.
If you make the gross weight 1320 lbs or less when you initially certify it, then you can operate it as a Sport pilot. The BUILDER specifies the Gross Weight when he initially gets the airplane certified.
It will NEVER be a "Light Sport"airplane. It is NOT bound by the LSA standards.
It will always be "Experimental-Amateur Built" not E-SLA.

DaveG

Isn't that what I said?

John Scott