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Thread: Lift Strut Fairings

  1. #21
    Senior Member HighWing's Avatar
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    Default Re: Lift Strut Fairings

    Thanks for the explanation. Your comments prompted me to dig out the sample I had made and check it once again. I suspect the two experiences might be akin to the old apples and oranges idea. In my application the use of the foam was primarily as an adhesive with some to added structural stiffness. The foam would have been encapsulated in fiberglass, microballoon filler, primer and top coat. My current set-up omits the fiberglass and replaces it with aluminum sheet with the primer and top coat. The whole object being an aerodynamic reshaping of the round lift strut.

    I did a little research on the sprayed on roofing. UV is a big issue as the foam is very susceptible to UV damage and the top coating is critical to protect the foam. It is sprayed on and has to be able to adapt to the daily movement of the foam as it cycles from the heat of full sun to the cool of the night. Then the object is as a weather resistant roof with a thermal barrier added in. The typical lift strut is typically in the shade of the wing and those cyclic temperature swings shouldn't be as critical an issue.

    The final thought, though is the advice that I got that it was the foam that was corrosive. My test piece fully dispels that idea as the area in question has been in full contact with untreated steel for almost 18 years with no hint of corrosion. One thing I did notice this time was that the foam does not stick as an adhesive to the unprimed steel, but does adhere quite strongly to the portion that was primed. I am able to scrape the foam residue from the steel with a fingernail. If the foam roof coating was sprayed onto bare metal without a primer, it could allow it to lift due to the cyclic daily temperature shifts and possibly allow capillary water flow between the steel roof and the foam - really bad.
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  2. #22
    Senior Member Dave S's Avatar
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    Default Re: Lift Strut Fairings

    Interesting observations.....what I get from this is the occurance of corrosion does not necessarily mean the material under which corrosion occurs is "corrosive". More a matter of delamination between the substrate and coating (like on the roof deal) allowing oxygen and moisture to work its magic to turn steel back into iron ore and aluminum back into bauxite.

    Much of corrosion prevention is sealing a surface with a coating that will not delaminate (meaning the correct coating plus correct surface prep) to prevent moisture/oxygen from coming in contact with the substrate.

    I recall working an a certified aircraft where a novel covering (razorback) was laid directly over a bare aluminum sheet with no surface prep - we had a lot of white dust & corrosion craters under that as the razorback works like a wick and did not exclude either moisture or air and there was no other coating to prevent nature from taking its course.

    Some things aren't corrosive, they just don't prevent corrosion.

    Sincerely,

    Dave S

  3. #23
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    Default Re: Lift Strut Fairings

    I know it's an older thread.....anyone use anything different to glue the lift strut fairings on besides hysol? It appears that snapping them together will hold them in place so I am thinking that using expensive Hysol may not be necessary. Anyone ever use Gorilla glue adhesive or a quality construction adhesive from Home Depot?

  4. #24
    Denalifox's Avatar
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    Default Re: Lift Strut Fairings

    Quote Originally Posted by Jerrytex View Post
    I know it's an older thread.....anyone use anything different to glue the lift strut fairings on besides hysol? It appears that snapping them together will hold them in place so I am thinking that using expensive Hysol may not be necessary. Anyone ever use Gorilla glue adhesive or a quality construction adhesive from Home Depot?

    I used Gorilla construction adhesive. Haven't flown it yet but those things are on there solid.
    S7 STi O-320 currently flying

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