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Thread: Corrosion X in building a metal homebuilt.

  1. #21

    Guys, thanks for the input. I believe I will take
    Ron Wanttaja's advice and prime spars and skin joints. Once I paint, I will go the Corrosion X route. I will be little bitty and want to be seen.

  2. #22

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    martymayes I believe that you are correct about the polyurethane paint. About 1977 we has a Cessna 180 painted with that stuff and about 6 months we had an unbelievable amount of filiform corrosion . It had no corrosion with the factory paint . It looked like worms all over the C-180 . This was in Florida where there is high temps, high humidity and salt air .

  3. #23

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    Metals corrode according to the galvanic series. Those high on the scale are most reactive when coupled with materials lower on the list. Magnesium is very high and gold is lowest. All other engineering materials are in between. Aluminum is below magnesium so if these two are in contact with an electrolyte (water, especially salt water), the mag corrodes first. If you look at alum alloys like 6061 or 2024, the 6000 series has mag as alloying constituent. Since mag and alum are close on the galvanic series, there isn't too much activity. With 2000 series, the alum is coupled with copper as alloying element, which is lower on the scale, so the reactivity is higher. Therefore, 2024 has higher galvanic activity and corrodes easier. So you have to protect 2000 series more than 6000 series. By cladding the reactive alum alloy with pure alum ( cladding) you reduce the galvanic activity at the surface and hopefully reduce corrosion.

  4. #24

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    Quote Originally Posted by rwanttaja View Post
    Then again, there was a run of Cessnas in the '70s where the company scrimped on the anti-corrosion prep; these have suffered a lot of corrosion.

    Case in point. Take a look at these three homebuilts:

    The blue single-engine one in the middle is the Wickham "A" ("Bluebird") that first flew in 1955, and the twin in the foreground is the Wickam "B", which flew about 1967. Both are all-metal, 2024, I believe. Though they might have been 7075. The third airplane is some obscure wooden type. :-)

    Anyway, the designer/builder of the first two was Jim Wickham, a configurator for Boeing Commercial Airplanes. It was his opinion that airplanes built from aluminum did not need additional corrosion protection, and neither of his airplanes were primed.

    The Bluebird (single-engine) was restored in the ~90s. Didn't hear of much anti-corrosion work needed. However, the Bluebird was an active airplane through most of its life, and was mostly hangared, I believe. The A&P who does my Condition Inspections did the restoration (and he parks the plane across the hangar row from my Fly Baby).

    The Model B (twin) was donated to a museum in ~1980, who parked it outside for 10-15 years until a chapter member bought it. He found massive corrosion in the wings.

    So....it's basically a crapshoot. If I were building something from 2024, *I* would prime the thing. And as Falcon21 says, if you apply Corrosion X during construction, don't expect to be able to paint the outside of the airplane. That stuff will weep through various holes (as it's designed to) and ruin any chance for paint adhesion on the outside.

    I like Bob's recommendation for Zinc Phosphate.

    Ron Wanttaja
    I did a Google search to see if there were ever plans for the wickham B didn't see anything

    just double checking here if wickham ever made the plans public or donated them to a museum or university?


    thanks
    Michael

  5. #25
    rwanttaja's Avatar
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    Quote Originally Posted by North_roll View Post
    I did a Google search to see if there were ever plans for the wickham B didn't see anything

    just double checking here if wickham ever made the plans public or donated them to a museum or university?
    Wickham never made his plans public; don't know what happened to most of them. May have donated them to Seattle's Museum of Flight or the Aeronautical department at the University of Washington.

    At the time of his death, his wife donated his partially-completed Wickham Model F to the local EAA. I believe the plans came with it. Parts (most of the fuselage and partially-completed wings) are stored in the hangar where EAA 441 meets, don't know where the plans are. Some of the members of EAA 26 and 441 are looking into completing the aircraft, so they probably have them. It was designed for two Mazda rotary engines.

    The guy who owns the Bluebird also now owns the Wickham Model C "Sunbird", a small single-seat cantilever-wing airplane made of wood. VW-powered. The Wickham D and E were similar. Wickham sold the D before it was even completed. He was performing spin testing with the Wickham E (Sunbird II) and ended up having to bail out. He was 68 at the time.

    Interesting guy. I found a write-up about him, that I did for my chapter newsletter about 14 years ago. It's attached.

    Ron Wanttaja
    Attached Images Attached Images

  6. #26

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    Quote Originally Posted by rwanttaja View Post
    Wickham never made his plans public; don't know what happened to most of them. May have donated them to Seattle's Museum of Flight or the Aeronautical department at the University of Washington.

    At the time of his death, his wife donated his partially-completed Wickham Model F to the local EAA. I believe the plans came with it. Parts (most of the fuselage and partially-completed wings) are stored in the hangar where EAA 441 meets, don't know where the plans are. Some of the members of EAA 26 and 441 are looking into completing the aircraft, so they probably have them. It was designed for two Mazda rotary engines.

    The guy who owns the Bluebird also now owns the Wickham Model C "Sunbird", a small single-seat cantilever-wing airplane made of wood. VW-powered. The Wickham D and E were similar. Wickham sold the D before it was even completed. He was performing spin testing with the Wickham E (Sunbird II) and ended up having to bail out. He was 68 at the time.

    Interesting guy. I found a write-up about him, that I did for my chapter newsletter about 14 years ago. It's attached.

    Ron Wanttaja

    Thanks for for the info, the article is a very good read. I looked up the Seattle flight museum. Once they open their doors again I'll give them a call and see if they have the plans. Sometimes you get lucky with this sort of thing.


    im already involved with a few building projects, but I'm learning Solidworks and digitizing old plans like these would be good practice. Start with the rudder... Then elevator...etc...may never finish but it's good practice .

    Every year someone on some aviation site asks....what about an experimental twin??...
    now we have somewhere to point them...hopefully someone with a good nose for this will uncover those plans..


    thanks
    Michael
    Last edited by North_roll; 06-19-2020 at 02:52 PM.

  7. #27

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    The best anti corrosion to use is Corban 35 made by ZIP Chemical . Boeing uses it on all of their aircraft and airlines use it where needed at their overhauls . It can be be bought is spray cans or bulk to spray or brush . Sky Geek has the best price. You Tube it . I use it on my A/C .

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