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Thread: Tanks and fabric questions

  1. #1

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    Default Tanks and fabric questions

    Well today was an interesting day.

    I completed painting a small fabric patch on the right wing in prep for mounting the wings to the fuselage.

    These are 2005 vintage wings/tanks built under the builder assist program at SkyStar, covered and painted with Aerothane.

    We decided to slosh the right tank for possible release agents and contamination. Mixed a 50/50 solution of acetone and avgas. While sloshing we had a significant leak at the finger strainer fittings. The solution wetted the fabric along the leading edge in the tank bay and some of the lower rib lines, before we could get it cleaned up some of the paint blistered.

    Several questions:

    Does anyone have a recommended sealant for the fittings, as I'm not too impressed with the Permatex used by Skystar.

    These tanks don't have the sump quick drain fittings. Can/should they be added?

    The slosh solution damaged the paint (soaked thru from the back side), but I doesn't seem too have much effect on the polytac/polybrush/fabric bonds. Is this a problem?

    Thanks in advance for any feedback you can give.

  2. #2
    Senior Member Dorsal's Avatar
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    Default Re: Tanks and fabric questions

    "These tanks don't have the sump quick drain fittings. Can/should they be added?"
    Tom, Are you saying there is no fitting or no hole, I have the same vintage setup and the threaded holes should be there. If they are just still covered over this may explain your leaking.
    Just asking.
    Last edited by Dorsal; 04-14-2013 at 04:12 AM.
    Dorsal ~~^~~
    Series 7 - Tri-Gear
    912 ULS Warp Drive

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    Red face Re: Tanks and fabric questions

    Dorsal,
    Thanks for the hint! Yep I found them.

    Now that I've found them, I'm surprised they don't have any reinforcement or grommets around them???

    I also noted comments from other posts about adding drain grommets in the wings and elevator. These were not installed either and as I've said, that's a little surprising with the fabric painted by the factory....

    Live and learn...
    Last edited by Tom T; 04-14-2013 at 10:06 AM. Reason: mistakes

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    Default Re: Tanks and fabric questions

    Hey all, I continue to learn from this mistake.

    I searched the posts and didn't find any info specific to my issues so here's what I have to date.

    As Dorsal pointed out the drains holes were in the tanks, I just plain missed them due to not having built the wings or done the covering (failure to read closely enough )

    The wonderful tech support at PolyFiber responded today (Sunday) and indicate the solution didn't do any fabric damage .

    It did blister the paint on the wing and we are now discussing options to repair the finish as well as areas for additional grommets....

  5. #5
    Senior Member HighWing's Avatar
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    Default Re: Tanks and fabric questions

    Question. Are the tanks of that vintage the new ethanol resistant Vinylester resin? I don't recall when they were introduced. If they are - no issue. If not did the rinse remove a sloshing compound.
    Lowell Fitt
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  6. #6

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    Default Re: Tanks and fabric questions

    Highwing,
    These are the earlier which are not Ethanol resistant...
    Thanks for the info

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    Senior Member t j's Avatar
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    Default Re: Tanks and fabric questions

    I also noted comments from other posts about adding drain grommets in the wings and elevator. These were not installed either and as I've said, that's a little surprising with the fabric painted by the factory....
    Chenk your builders manual fabric section to see if you really need...and want...to install drain gromets. In my manual anyhow, it is left up to the builder. It mentions that the factory at that time just used the point of a soldering iron to melt 1/8th inch drain holes in the fabric.

    I made a templet out of a small scrap piece of thin sheet aluminum. With a step drill, drill a hole the size you want to make in the fabric. Place it on the fabric where you want to make the hole and poke the needle nose soldering tip through.
    Tom Jones
    Classic 4 builder

  8. #8
    Senior Member HighWing's Avatar
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    Default Re: Tanks and fabric questions

    I agree with tj. Gromets are not necessary, but drain holes are a very good idea.

    On another note. The tanks are built up in female molds. Any releasing agent would be on the outside. My thinking on the rinse recommended in the service letter.would be to just remove any uncurred resin. I know that Polyester resin is oxygen inhibited. What that means is that the surface resin in contact with air will not cure. Not sure about the Vinyl ester resin, but I suspect the need for the rinse is caused by uncured resin on the internal surfaces, but it is definitely not release agent. One of the guys here at Sun N Fun has a friend who built a Rans S-7 who had plans to put a diesel engine in it so put large fuel filler necks that accommodate Jet A nozzles. He said that he could put his hand into the tank and if the tank had ethanol containing mogas, the surface was rubbery. And then when filled with avgas, the surface would harden right up.

    Hate to mention it, but I wonder if the 50% acetone rinse removed any liner. I think the earlier tanks came with a Kreem liner - someone correct.me. When re Kreeming acetone can be used to remove the old Kreem.
    Lowell Fitt
    Goodyear, AZ


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    Default Re: Tanks and fabric questions

    Lowell,
    Thanks again for all the additional information.

    My tanks have not been kreemed, as far as we can tell. We can see the resin inside the tanks thru the filler and don't see any kind of coating.

    You make a good point on not having release agent inside the tank. We were really trying to ensure a clean tank and no fiber release to plug filters, etc.

    Fortunately we can get good non-ethanol mogas here (don't know how long though), so I'm resisting a tank coating/liner to protect from ethanol. I may reconsider that now.

  10. #10
    Senior Member Dorsal's Avatar
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    Default Re: Tanks and fabric questions

    I have the same gen tanks, no cream and used a pure acetone rinse. The inside of the tanks were sticky before the rinse and not after. As documented in earlier threads I had lots of brown stuff in the first rinse but clear by the third.
    Dorsal ~~^~~
    Series 7 - Tri-Gear
    912 ULS Warp Drive

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