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Thread: TIG Welding a Fuselage-Insight needed

  1. #1
    EAA StaffEAA Staff / Moderator Charlie Becker's Avatar
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    TIG Welding a Fuselage-Insight needed

    I've started the finish welding on my fuselage. Here is my setup:
    Lincoln Precision TIG 185
    Set at 48 amps
    20 CFH on the flow meter
    1/16 2% thoriated tungsten
    1/16 welding rod (ER80
    7 seconds postflow
    I'm generally using a gas lens.

    Any tips or tricks for TIG welding the clusters, especially the acute angles.

    If you want to see my project, it is a super cub clone: www.facebook.com/piratecub
    Sonex flight testing complete. Building a Super Cub clone, check it out at www.facebook.com/piratecub

  2. #2
    Aaron Novak's Avatar
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    For the tight corners you may need to break the 1D tungsten stickout rule of thumb and go more like 1.5D. Gas lens is a good idea, if you are going to push more stickout you may want to go to a 3/32 tunsten to help cooling and decrease the flowrate to prevent pulling it atmospheric air. Shut all the doors, dont breathe too hard and remember to always weld with the grain ( i.e. if it was a 90 deg tee you weld from the tee section to the lap section in 4 segments). Dont shortchange the size of the reinforcement and avoid convex welds and dont start and stop 15 times per weld, stray arc scars are great places for crack initiation. I (and every welding engineer and metalurgist I work with ) would temper the critical weldments as well ( engine mount, landing gear, wing and strut attach ). Oh and a blunter ( I know its not a real word) grind angle on the tungsten can help prevent arc wander. Have Fun!!
    -Aaron

    -P.S. if you get into some heavier areas and need a REAL tig welder you can use my Dynasty300 .......(Sorry.....I had to...)

  3. #3
    Chad Jensen's Avatar
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    Excellent info for those of us that are new to (TIG) welding...thanks!
    Chad Jensen
    EAA #755575

  4. #4

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    Welding Tips

    Charlie, this is the best site for welding tips Iv'e seen...
    http://www.weldingtipsandtricks.com/index.html

  5. #5
    Chad Jensen's Avatar
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    Cool website Jack!
    Chad Jensen
    EAA #755575

  6. #6
    Aaron Novak's Avatar
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    Word of caution, many of those online welding sites are copy and pasted bits and pieces from some highly questionable sources. There are sources of data that are many times biased, uneducated or unexperienced. From my experiences working in engineering, typically they are as follows.

    1-Welding Equipment Suppliers. Remember they survive by selling equipment, many times the testing is biased or non-existent.
    2-Authors. Especially those that never worked in engineering, but like to give hard and fast advise on every aspect of welding ( many times highly opinionated ) or very wild and broad claims.
    3-Welding consultants. Remember , they dont have to deal with the aftermath of their suggestions.

    So who can you trust?? Usually the best source of information is an independent person, not connected with any company that makes a profit by welding equipment sales, that has or is working in a current engineering field. It helps if this person or source is also a hobbyist in the same areas you need advise in. Why? Because they tend to highly educate themselves on the particular subject and have access to information you will NEVER find on google. Engineering texts are a great source of information, however pay attenting to many of the AWS texts as they are not as unbiased as you may think, check the authors. The ASM handbooks are a great start, as are the plethora of doccuments available in the nasa archives.

  7. #7
    AllenR's Avatar
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    20 CFH on the argon seems kind of high. You'll waste a lot of gas. I used 12-15 CFH for my whole Skybolt fuselage and aluminum fuel and smoke tanks. Don't be afraid to pull out that tungsten as far as you need to reach into the acute corners. If you're not getting enough argon around the weld, it won't even weld- just a bunch of sparks. Use a gas lens ALWAYS. Turn off the fans. Be sure you see the filler melt into the surrounding material as you run your bead. Everything else sounds perfect. I have the same setup, I love it.

  8. #8
    EAA StaffEAA Staff / Moderator Charlie Becker's Avatar
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    Ok, here are a few photos of what I've welded so far.
    IMG_0931.jpgIMG_0922.jpgIMG_0928.jpgIMG_0929.jpg
    Sonex flight testing complete. Building a Super Cub clone, check it out at www.facebook.com/piratecub

  9. #9
    Aaron Novak's Avatar
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    Hey Charlie,
    What I am seeing is fairly inconsistent penetration, inconsistent fillet size, marginal shielding and some lack of heat control. The weld fillet is generally the size you should be aiming for. I also see some undercutting in areas, some spots where you touched the tungsten to the weld pool. ( remember if you "snag" a tungsten you need to grind out the area where it touched, imbedded tips of tungsten can be crack initiation points ). I know you really dont want to hear this, but I think seriously doing some helmet time with flat stock will help you. Butt, Tee and lap welds perfected in flat stock will make an easier transition to clusters. Is what you did unsafe? I dont know, If I was the instructor looking over your shoulder I would have had you do a lot more practice parts and sectioned them so you can see how your terchnique influences the weld quality beyond external "looks". If you would like someone to look over your shoulder I can run up the hangar sometime, let me know.
    -Aaron

  10. #10
    AllenR's Avatar
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    Whoa, way too harsh. Charlie is too nice a guy so he probably won't reply but I will. First of all, are the welds perfect? No. Do they need to be as perfect as the TIG welds on P&W turbine blades. No. Are they more than serviceable for an experimental. Yes. My only issue with the welds is that you're using a little too much heat (move along faster) and the bead needs a little more filler rod. Otherwise they are OK. If a builder insists on perfection on his airplane, he will never finish.

    Practice never hurts, but it will take 500 hrs. practice before you approach a stage of perfection that's just not needed. So finish weld small parts like rudder pedals, etc, so that if you're not happy with the weld, you can easily and cheaply build another. On the fuselage, you will start finish welding at the tail and move your way forward so by the time you get to the high stress areas north of the pilot station you will be pretty damn good.

    Forum members should refrain from super critical posts since they do nothing more than shut people down from sharing. If you have a real concern, private message the person. Certainly, if you live in the same town just call them up. Just my $.02.
    Allen Rice

    Skybolt
    RV9A
    Pietenpol

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