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Thread: Epoxy primer inside spars

  1. #11
    Senior Member jiott's Avatar
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    Default Re: Epoxy primer inside spars

    I primed the inside, and outside too, of my spars because I figured someday I may want to put floats on it. Kitfox factory recommended priming the inside for float application, especially near salt water.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  2. #12
    Senior Member Dave S's Avatar
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    Default Re: Epoxy primer inside spars

    I would promote the idea that doing something (paint, alodine, corrosion proofing/sealer), with the inside of the spars (as well as the outside like where many builders epoxy prime them) is important for long term service given that the most susceptible part of the assembly is precisely where little can be done with it inspection or repair wise. Where the insert contacts the inside of the spar tube is the most likely place for corrosion to start. I regard corrosion prevention/corrosion proofing to be critical in the long run - if a plane will be around for many years. Corrosion in lap areas in old aluminum airplanes is not unheard of - usually the little raised "donuts" around a rivet holding aluminum skin to an aluminum rib, or spar capstrips, or skin overlaps or similar lap areas is where it ends up.

    Corrosion will eventually turn all aluminum into bauxite, from whence it came - some things speed up the process like electrolytes & moisture. Some things retard the process like sealing the surface to keep oxygen, moisture and electrolytes away from the surface (at least till it gets a scratch).
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  3. #13
    Senior Member colospace's Avatar
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    Default Re: Epoxy primer inside spars

    Dustin, I used Corrosion-X inside my spars. Living in the low humidity of Colorado, I'm thinking that is sufficient although I will probably renew it at each condition inspection. I also soaked the inside of my lift struts with linseed oil early on.
    - Gary
    S7 SuperSport Tri-gear
    w/Rotax 912, Oratex, Dynon

  4. #14
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    Default Re: Epoxy primer inside spars

    So just a bit of added info. Unless you remove the oxide layer on the inside (or outside) of the spars before you paint, the adhesion of the paint to the surface is debatable. Alumiprep or something similar should be used before you apply the primer, as this gets rid of the oxide layer and any oils or other contaminants from the extrusion process. I used alumiprep and then alodined the spar internals using the tennis ball method. The alodine has enough chromium in it to give corrosion protection against most nasties, such as salts etc. FWIW.
    David
    SS7 Builder

  5. #15
    Senior Member Delta Whisky's Avatar
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    Default Re: Epoxy primer inside spars

    colospace - I'm liking the idea of using corrosion X or Boe shield - how did you apply it? Special spray rig? Tennis ball?

  6. #16
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    Default Re: Epoxy primer inside spars

    Here's another strong statement from someone qualified only in offering an unsolicited opinion: The spars will last a lifetime without any additional protection inside or outside, ocean environment or whatever. I guarantee it!

  7. #17
    Senior Member ken nougaret's Avatar
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    Default Re: Epoxy primer inside spars

    With this and your previous post, i have to ask, is this an inside joke that I am not aware of?
    SS7 O-200 Whirlwind

  8. #18
    Senior Member colospace's Avatar
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    Default Re: Epoxy primer inside spars

    Quote Originally Posted by Delta Whisky View Post
    colospace - I'm liking the idea of using corrosion X or Boe shield - how did you apply?...
    I taped the outer ends closed and sprayed what seemed to be a healthy dose of Corrosion-X into the inboard ends. I put rags beneath the outer ends to catch excess that eventually dripped out. The Corrosion-X is supposed to create something of a fog that coats all surfaces.
    - Gary
    S7 SuperSport Tri-gear
    w/Rotax 912, Oratex, Dynon

  9. #19

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    Default Re: Epoxy primer inside spars

    Quote Originally Posted by David47 View Post
    So just a bit of added info. Unless you remove the oxide layer on the inside (or outside) of the spars before you paint, the adhesion of the paint to the surface is debatable. Alumiprep or something similar should be used before you apply the primer, as this gets rid of the oxide layer and any oils or other contaminants from the extrusion process. I used alumiprep and then alodined the spar internals using the tennis ball method. The alodine has enough chromium in it to give corrosion protection against most nasties, such as salts etc. FWIW.
    You did alumiprep first then alodine and that was all? No primer?

    Thanks all for the replies.

    Scott

  10. #20
    Senior Member bbs428's Avatar
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    Default Re: Epoxy primer inside spars

    I prepped the inside spars with white vinegar slosh for about 5-10 min. I used gorilla tape on the ends.
    Held the wing above my head and rocked it all about. Kinda like the "truffle shuffle" but you don't giggle your fat - just the wing.
    Good workout... not. Best to bribe a family member to do it. Lol.
    A fresh water rinse, a hair drier dry job and then an Alodine slosh for 5-10 min.
    Finished with another slosh of fresh water. Done.
    Somebody said that carrier pilots were the best in the world, and they must be or there wouldn't be any of them left alive. — Ernie Pyle

    Brett Butler
    Flying: 1998 Model 5 Outback, 912ul Zipper 110hp, G3x avionics, ss7 upgrades

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