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  • Tube Seal Use

    Starting on fuselage, Wondering if any body is using poly fiber tube seal. I am thinking of drilling a 1/8 hole inside of longeron joints the let the tube seal spread to the vertical and horizontal tubes after welding.The method would be to fill one longeron rotate fuselage and let drip into tubes welded at joints and then drain out other longeron . Has anybody done this or is this unnecessary.

  • #2
    Hello Peter. My personal 2 cents worth on this is that if you live by the coast in a salt air environment - it is a good idea to get some of this oil into the lower longerons which is where corrosion mostly happens. Put it in, turn the fuselage upside down and all around so it coats the interior of the longerons well, then drain out excess. If you live in a dry place and keep your plane hangered - I wouldn't worry about it. Mark

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    • #3
      I completed this exercise fairly recently. For me, tubeseal was a humbling experience. Having welded aluminum hydraulic and fuel tanks, I considered myself a decent welder. Tubeseal reveals pinholes that are not visible to 50 plus year old eyes. My problem areas were in the apex of the deep V's and a couple of weld laps. To be clear, weld laps are where weld terminates over completed weld. This was my first fuselage and I learned a lot by little issues like these "almost microscopic" pinholes. The real challenge is positioning to complete welds.

      If I were to weld another fuselage I would do the following:

      go a little further on the overlaps when completing the welds

      Make sure to overlap the deep V's to an excess. These are located above the cargo and over front doors mostly. It might be helpful to weld out a further distance to allow better torch access.

      Take more time where the longerons meet the rudder post. These are tight, busy, and difficult areas to see much less get a torch, filler rod and eyes on. Some preplanning of weld sequence could have helped here before tacking all pieces in that area.

      As usual, Mark's advice is sound. My fuselage was welded in south Louisiana and moved to New Mexico. The difference in corrosion is astonishing. I wouldn't be concerned with tubeseal if I had been in New Mexico from the start.

      I'm not an expert and can only relay my experience so not offering "need to do it this way" advice. I saw no need to pre-drill tubing prior to fitting and tacking. This would be necessary in two tube only T's but I don't recall any. Pre drilling would be necessary if you are only putting oil points in the longerons.

      AGAIN, since my fuselage was welded in 95% humidity I went a little further than most should. I drilled #40 holes in the longerons and injected with a syringe fitted with a needle. Didn't want any bigger hole than was necessary to weld closed . Then I drilled each cross tube on the bottom on the passenger (right) side and top cross tubes on the left. Tubeseal is truly amazing stuff. It revealed a few leaks that I can't explain how it got there! After injecting I welded the #40 fill holes closed. Rotated the fuselage and repaired pinholes as they showed up. Think I had 6 leaks. Tig welding an oily hole is not easy due to contamination. I preheated the weld area with a torch to cook off the oil. Then repaired the weld. Maybe you won't need to do this?

      True confession time. I'm not proud of this but I did have to cheat! Where the lower longerons meet the rudder post and tail spring mount plate I felt I was gonna do more harm than good due to very limited access. I sealed this pinhole that I couldn't even see or find with a bit of JB weld. Worked fine so far through prime/paint and recently completed fabric covering.

      Sorry long winded, hope this is somewhat helpful.
      Thanks too much,
      John Bickham

      Los Lunas, NM Mid Valley Airpark E98
      BH Plans #1117
      Avipro wings/Scratch
      http://www.mykitlog.com/users/index....er&project=882

      Comment


      • #4
        Thanks for sharing your experience. I am sure I will have leaks. My next question would be is it alright to have pre drilled holes located in the center of the longeron joints where the vertical and horizontal tubes come together. That way I would not have to weld up holes after the tube seal , I could fill the top tube and let the tube seal seep through the frame to a drain point. I would then only have to seal a few holes. I am concerned about the strength of the structure with an interior weep hole at the joints. I read somewhere that some aerobatic airframes are pressurised all the time to insure airframe integrity. I am assuming that the airframes have interior holes.

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        • #5
          Years ago I watched Ed Marquart do this process with hot linseed oil. He only did the lower longerons arguing that nearly all of the corrosion he had seen and repaired was on the bottom of the lower longerons in the last bay in the aft fuselage. My guess is that Tubeseal is better then linseed oil. I plan on doing the same to my Patrol as I live in a humid environment. I will not bother with trying to treat the verticals and diagonals. I will try to treat the tail post if its convenient to do so. I've often wondered that if this area could somehow be vented that it might help. It also might let moisture in and be counterproductive.
          Gerry
          Patrol #30

          Comment


          • Mark Goldberg
            Mark Goldberg commented
            Editing a comment
            I thought Tube Seal was/is boiled linseed oil. Charlie Vogelsong once told me that putting the oil in the lower longerons was all that was needed as that is almost always where the corrosion is. I believed Charlie as he was the largest wholesaler in the world of 4130 tubing from the 1960's on through around 2010. Mark

        • #6
          Per the Safety Data Sheet It's 35 - 55% raw linseed oil plus some additional ingredients that I cannot find listed in the SDS.
          Gerry
          Patrol #30

          Comment


          • #7
            I'm not qualified to answer your question if it is ok to drill a couple of holes in the longeron at each cluster. You need a structural engineer for that. I will add to try to weld a test cluster just as you would in the build process. If build as Bob designed you will tack fuselage bottom together and then the top, tacked only. Support in space and then fit and tack verticals and diagonals in. Only after all tubes fitted and tacked do you weld out completely. Point is all these tubes added create more of a outside saddle weld that only seal to the longeron on the very outside welds. The internal intersections are butt joints that have a few tacks. You would have to 100% weld each tube as it is added. It would be a fitting nightmare. Hope I am making sense. Point is you would only need one hole in the longeron at most and 1/8" is overkill IMHO.

            I went with small holes away from the stress points of the clusters. Don't worry about welding closed a few #40 holes. By the time you weld out a fuselage, you should be able to close a #40 hole on less than a minute..

            I truly believe the other 45% additional ingredient is gravity defying pixy dust. This stuff seems to creep uphill in ways that I couldn't believe. It will find pinholes that you can barely see without magnification. Some I had to find with heat. You look for the little string of smoke.

            one of my personal faults in building is overthinking things. Creates unnecessary work in almost all cases and extends the build time to embarrassing length. Pretty sure that 1947 PA-12 that my neighbor let's me fly has gotten by with no holes drilled in clusters. Not a criticism, just relaying my experience.

            Last edited by John Bickham; 12-21-2018, 08:43 PM.
            Thanks too much,
            John Bickham

            Los Lunas, NM Mid Valley Airpark E98
            BH Plans #1117
            Avipro wings/Scratch
            http://www.mykitlog.com/users/index....er&project=882

            Comment


            • #8
              I am thinking about adding a fitting in the lower longerons that I can use to add the Tube Seal but also use to pressurize the tube to check for air leaks, which would indicate a crack. I don't remember where I heard about this trick of pressurizing a tube frame to check for cracks. It was either from aerobatic airplanes or race cars.

              As a final check of my welding, I would make sure that the lower longerons will hold air before sandblasting and painting.

              I haven't done it yet and I may decide not to. Just an idea.

              Comment


              • Sir Newton
                Sir Newton commented
                Editing a comment
                The plan is to add a vacuum gauge to my BH5 airframe. I talked with some in the know P.Eng peoples who will never comment to anything on a professional level. The chat was about a N2 purge on the frame, however the idea was 2nd to applying a vacuum to the system.
                Same idea as double walled storage tanks was to store all sorts of nasty things we do not want leaking on the ground.

            • #9
              I find myself over thinking also and this is an example, You completely understand what I am proposing and the Idea of the outside saddle weld with the weep hole in the longeron. To me it seems the strongest area for a weep hole. But as Mark said just treating the longeron is sufficient and your example of 1947 PA-12 tends to prove it

              Comment


              • #10
                Originally posted by S Lathrop View Post
                I am thinking about adding a fitting in the lower longerons that I can use to add the Tube Seal but also use to pressurize the tube to check for air leaks, which would indicate a crack. I don't remember where I heard about this trick of pressurizing a tube frame to check for cracks. It was either from aerobatic airplanes or race cars.

                As a final check of my welding, I would make sure that the lower longerons will hold air before sandblasting and painting.

                I haven't done it yet and I may decide not to. Just an idea.
                I've heard this also...but as it was explained to me ....if you can pressurize the tube with no leaks....then seal it.....it will rust to a point...but then stop because there is no oxygen left to continue the process...

                heard this 20 years ago...from God knows who...I know nothing of rag and tube so don't use me as a source...just chiming in...

                Comment


                • Sir Newton
                  Sir Newton commented
                  Editing a comment
                  fyi, I am applying a vacuum to my frame. With a gauge to monitor for leaks.
                  Been awhile since I have heard from you.
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