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Thread: Will AVGAS damage wood wing structure?

  1. #1
    Sluggo's Avatar
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    Question Will AVGAS damage wood wing structure?

    Gents,

    A Marquart MA-5 Charger I've been looking at buying had the upper wing tanks rupture due to the installation of motorcycle fuel caps that let air in the tank, but wouldn't let it out (like on my HD, the fuel has an overflow expansion drain line) Thus, after filling the tanks and letting the aircraft sit in the sun, the upper tanks ruptured due to expansion of the fuel inside, letting 10 gallons of AVGAS run back through the upper wing structure and out the trailing edge of the wing, all near the center section, maybe 3 to 4 feet outboard from center (and mostly to the right side, it seems.) Don't know how long the gas took to drain out, how long the wook was soaked in AVGAS.

    The owner couldn't fully answer if any attacking of the rear spar varnish, wood, and other internal wing parts had happened. Further, it seems no inspection has been done to look and see. Access would certainly be difficult, I agreed. But still...

    I think this happed a couple of years ago, maybe less, but the airplane has been flown regularly since this happened. Anyway, I'm wondering if AVGAS attacks wing spar varnish, and/or the wood itself. Are there structural concerns here that would make a purchase unwise?

    Thanks in advance.
    Last edited by Sluggo; 07-11-2018 at 10:19 AM.

  2. #2
    cub builder's Avatar
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    Some of this kind of depends on how well the wood was sealed and what kind of varnish or resin was used to seal it. An additional factor would be how long the wood soaked in avgas. But generally speaking, Avgas isn't typically going to dissolve, solften or otherwise damage a good quality varnish or epoxy. If the Avgas just ran through the upper wing structure, I wouldn't worry much about damage, but of course doing a proper inspection is always a good choice.

  3. #3
    FlyingRon's Avatar
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    I agree with Cubbuilder. Gas shouldn't damage most varnishes or epoxies. Most of it will evaporate likely before it damages unprotected wood. The biggest issues is will leave a stain and smell behind which can be a devil getting rid of.

  4. #4
    Sluggo's Avatar
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    Thanks for the info, gents.

    Yes, I'm pretty sure the gas just ran on out through the trailing edge drain holes. As the plane was parked, I can't see how it could have remained for any large amount of time. Seeing as how this wasn't recent, and the plane has flown many times since, there is no lingering odor...good things.

    Agree, the owner should make an attempt to get as good a look as possible up in there. Don't know if a borescope tool would work or help. Since the plane is due for a condition inspection, this might be a good item to put on the list, and have attested-to in the log.

    Another thing, the Charger does look very well built. Welds look good, many signs of good craftsmanship. So if this is any indication of the builder's attention to detail, I'd be surprised if he went with a poor varnish/sealer.

    I suppose a bigger concern is that, if I buy, I will now inherit two ruptured upper tanks, and the worry/hassle of getting them fixed...and if I sell later, questions like this from a buyer(s) like me! LOL As an aside, I posted a while back about just going with a larger fuselage tank to gain more capacity, and just leaving the wing tanks alone. Otherwise, it looks like a big job to cut, remove, repair, reinstall, and then recover. Not to mention the cosmetic worries once the plane is back together. And I'll admit, all that is beyond my skill set right now.

  5. #5
    DaleB's Avatar
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    If it concerns you, you can do the cut/inspect/repair or have it done for you. Build that into the price if you decide to buy. If it's going to bug you and you don't want to buy a project... wait for the next one to go up for sale.
    Measure twice, cut once...
    scratch head, shrug, shim to fit.

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