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Thread: PA-18-135 GW Upgrade Questions / Welding Covered A/C

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    PA-18-135 GW Upgrade Questions / Welding Covered A/C

    I recently purchased a 1952 PA-18-135. I would like to install Borer's STC SA292AL to increase the GW to 1750# for training purposes.

    I've sent to Karen Byerly for the STC. FYI her Cell number is 907-317-7732 and she asked me to post that information here. She also told me that she consults with Steve at Atlee for technical issues, so if some day in the future, you can't get in touch with her, maybe try him. But for now, she's happily selling the STC's and talking about her Dad.

    My cub is on the left (blue) and an image from SC.org is on the right. I believe I'm missing the four tubes required for this STC.
    Has anyone installed these tubes without recovering the fuselage? I've read a few posts suggesting that one could cut the fabric around the weld locations. Has anyone successfully done this?

    Second question, I'm assuming that I have the non-heavy chane. But this machine came off the line as a sprayer and then was sent back for seats. So I'm wondering if maybe it got the heavier gear install. How can one tell for certain?

    Thanks!


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  2. #2
    mike mcs repair's Avatar
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    you just clamp in the tubes with ms27405.pdf clamps (old number AN741-?) or such... might have to get a little creative at the clusters and move just off them...

    small fabric hole
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  3. #3

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    Quote Originally Posted by mike mcs repair View Post
    you just clamp in the tubes with ms27405.pdf clamps (old number AN741-?) or such... might have to get a little creative at the clusters and move just off them...

    small fabric hole
    Thanks Mike. I'll check the STC when I get it. Unless I'm mis-understanding you, I'm thinking that it will require welding, not clamps?

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    mike mcs repair's Avatar
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    Quote Originally Posted by tklenke View Post
    Thanks Mike. I'll check the STC when I get it. Unless I'm mis-understanding you, I'm thinking that it will require welding, not clamps?
    Interpret the last sentence about “up to the installer” to your advantage


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  5. #5
    Steve Pierce's Avatar
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    Not betting my IA on clamping those tubes in. You will have to cut enough fabric to weld around the tubes. The cabane needs 5/16" bolts vs the lower gross 1/4".
    Steve Pierce

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    Captain Ron's Avatar
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    Quote Originally Posted by tklenke View Post
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    Is that an alternate to safety cables between the cabane and the top gear fitting? How common is that? Looks similar to the Cub Crafters SB about adding reinforcement plates at that location.

  7. #7

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    Quote Originally Posted by Steve Pierce View Post
    Not betting my IA on clamping those tubes in. You will have to cut enough fabric to weld around the tubes. The cabane needs 5/16" bolts vs the lower gross 1/4".
    Just got the STC from Karen Byerly today. It specifically says "weld" so no clamping allowed. Also the cabane, struts, bungies and associated hardware get replaced.

    So back to the original question. Has anyone done welding on the SC without removing the fabric? Sounds like cutting holes around the weld areas and patching per AC 43.13 is doable, but would love to get the experience / description from someone who has actually done it.

  8. #8
    mike mcs repair's Avatar
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    PA-18-135 GW Upgrade Questions / Welding Covered A/C

    Quote Originally Posted by tklenke View Post
    It specifically says "weld" so no clamping allowed.

    .
    Not true. You are just bracing the center of tubes in that bay. You would need a field approval to technically change that step.... if that bothers you.



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    skywagon8a's Avatar
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    Quote Originally Posted by tklenke View Post
    Has anyone installed these tubes without recovering the fuselage? I've read a few posts suggesting that one could cut the fabric around the weld locations. Has anyone successfully done this?
    DO NOT CUT OUT A BIG PIECE OF FABRIC. Instead make a single cut with a razor blade starting at the location you wish to weld. Make 3 or 4 cuts so that you can fold back the fabric like opening an envelope. This will give you a big opening enough to weld. If you have a asbestos cloth to catch sparks all the better. After the welding is done, cut the edges back a small amount, close the envelope, stitch the points together, stick on untreated tapes over the cut, heat to shrink over the cut area, finish to suit. You could also stitch the cut with a baseball stitch and then tape. This is described in AC 43.13-1B
    https://www.faa.gov/regulations_poli...cumentid/99861

    Have a fire watch observer standing by while the welding is being done.
    N1PA
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    We had to shorten one of the vertical members of the greenhouse structure that was built too high during rebuild. Didn’t catch it until assembly and decided to fix it at a later time. Razor blade, foil and asbestos blanket like Skywagon said.

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    I used a surplus fire fighter shelter once without the tin foil thinking that would work. The sparks will burn through! I should have known better as my buddy that donated it said you have to shake them if you deploy them. Lesson learned. Not all blankets are created equal.
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  12. #12
    Herc's Avatar
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    Does anyone have suggestions on a good shop in wasilla, willow, big lake, or anchorage area that can install the borer gross weight STC for me with the fabric on? Looking at a time frame before July 30th. This is the last piece of the puzzle for me in order to install my new engine. Any help would be greatly appreciated!

    Thanks
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  13. #13

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    PA-18-135 GW Upgrade Questions / Welding Covered A/C

    If you look at the drawings for that STC you will have your answer. Lots of new tubing welded into the fuselage. Fabric needs to be removed.


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    Last edited by Trimcable; 05-07-2021 at 06:27 AM. Reason: I misread. Thought it was the PA-12. Sorry, not familiar with the Borer STC for the PA-18.

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    Herc's Avatar
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    I understand the fabric needs to be cut in those locations. Maybe I wasn't clear with my request. This is a covered aircraft so I'm looking for a shop that will cut the fabric, install the tubing, and patch the fabric. Just wanted to be clear that they wouldn't be working on a bare fuselage

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    I edited my reply right after I posted it. Unfortunately it's in fine print at the bottom of the reply. The Borer gross weight increase for the PA-12 has so much welding in the fuselage that the only way to do it is with a bare fuselage. I'm guessing on the PA-18-135 there is a lot less tubing to replace or add. Good luck with your modification.
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    Crash, Jr.'s Avatar
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    Quote Originally Posted by Herc View Post
    I understand the fabric needs to be cut in those locations. Maybe I wasn't clear with my request. This is a covered aircraft so I'm looking for a shop that will cut the fabric, install the tubing, and patch the fabric. Just wanted to be clear that they wouldn't be working on a bare fuselage
    I'd suggest Charlie Center out in Wasilla or Big Lake area. In Birchwood you've got Precision Plus and in Anchorage you can't go wrong with Dan's Aircraft or ACME Cub Training.
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  17. #17
    Herc's Avatar
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    Thanks Crash. I'll get in contact with them today
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    Here's a couple of shots from our recent GW upgrade on my PA-18. Find a small welder who doesn't mind spending 8 hrs on their back inside the fuselage. It was a bitch. Match the tube thickness to the existing would have made it easier. I bought the lightest tube the STC allows and that made the welding more challenging.

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  19. #19
    Herc's Avatar
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    Thank you for the pictures Tom

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    When welding, get either pieces of copper or aluminum bar to clamp to the tubes either side of the area needing to be welded. This will act as a heat sink to draw the heat away where fabric is.


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    Herc's Avatar
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    I'd like to get quotes from some shops around town. if it ends up being too expensive I'll weld the supports in myself and have my IA do the fabric repairs. I'm a pipe fitter by trade and know a damn good pipe welder that can tig it. Was just hoping i could get it done while I'm gone at work

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    Hi there! Close quarters mods are indeed a bitch but TIG has made them quite doable. If all we had still were oxy torches this thread would be moot, but in any case, if you do end up doing the work yourself, wet rags are your friend. Copper does work great but getting it clamped in place on round tubes can be a pita and eats up time. Damp rags are quick, more water can be applied from a squirt bottle if needed etc. Just don’t have them so wet they weep water on your new welds and flash cool them. That will create its own set of problems.
    May your work go smoothly!


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    Heat issues aside, we found that because of the locations of the tubes, you simply have to cut out the fabric so you can get sufficient access all around the weld. Not sure how your mileage could vary. Was really not a big deal to patch. Unless you want it to look perfect...in which case...I think lots of spraying and sanding in your future!

  24. #24
    Steve Pierce's Avatar
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    Are the three 3/8" tubes not installed in your fuselage under the battery box? A lot of the 135 Cubs had them from the factory.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

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    Quote Originally Posted by Steve Pierce View Post
    Are the three 3/8" tubes not installed in your fuselage under the battery box? A lot of the 135 Cubs had them from the factory.
    If you look at the first post, on the left (blue ceconite) is my 1952 PA-18-135 before the upgrade. 1952. Apparently they started putting those tubes in after my serial number.
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  26. #26
    Herc's Avatar
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    They aren't in mine either. 1951 sn 18-823

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