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Thread: covering fuel tank

  1. #1
    Senior Member Flybyjim's Avatar
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    Default covering fuel tank

    I am covering the wings and the instructions say to not attach the covering to the fuel tank, why? I did find a couple posts about this and it seems some have glued the fabric to the tanks. Can someone here explain the pros and cons about this issue?

  2. #2
    Senior Member Dave S's Avatar
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    Default Re: covering fuel tank

    Jim,

    Might be good to review the section on covering the wing beginning to end. Assuming you are using polyfiber (I have no experience with the other covering systems) the top of the wing tank fabric is secured around the edges with poly tac to glue it in place; but, this is proceeded by treating the top of the tank with polybrush (and make sure enough is used) which will become the bonding agent for the fabric after shrinking when additional polybrush is worked into the fabric.

    This procedure allows the fabric to slip and flatten out perfectly before it is bonded with additional polybrush after shrinking. The end result is a really smooth and solid surface over the tank top.

    If glue (polytac) were used prior to shrinking on the top of the tank, the fabric would not likely flatten out or shrink properly.
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  3. #3
    Senior Member 109JB's Avatar
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    Default Re: covering fuel tank

    This was a picture posted in the facebook Kitfox group and is the reason why you do the polybrush coats on the top of the wing tanks as described in the build manual. The polyfiber manual also talks about precoating plywood surfaces with polybrush before covering with fabric. I see the top of the tank as a similar issue to a solid plywood wing like a Bellanca Viking. A note that one of the posts in the Facebook post mentioned that Dan Denny recommended using a 50/50 mix of polybrush/polytac instead of just polybrush. I have no confirmation of this last bit.

    93777265_10107519219860305_5631167270014156800_o.jpg
    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox 3/4 1050 - Rotax 582 (Back Flying and sold)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)
    Glasair 1 FT (Waiting to start)

  4. #4
    Senior Member Flybyjim's Avatar
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    Default Re: covering fuel tank

    Very interesting photo, thanks for sharing, could be a problem. I am not using polyfiber on this project but have used it on another project so I understand the different properties of poly-tac and polybrush. I am using the Superflight covering process so I will see what they have to say about the tank adhesive.
    Those of you who used Stewert system what was your process. How about the prepainted covering system, how was this handled with their system?

  5. #5
    Senior Member Delta Whisky's Avatar
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    Default Re: covering fuel tank

    Jim - I used the Stewart Systems' process and began by applying the glue around the edges and on the main ribs and to an "imaginary" rib down the center of the tank. Then installed the fabric but used the Stewart technique to finish gluing to the edges only. Then a "light shrink" - enough to make the fabric flat i.e, no wrinkles. Then I glued to the ribs including the false rib on the tank. Then the several iterative steps to a full shrink. Because the Stewart Systems first coat of the sealing and primer steps is a thinned glue to the entire fabric surface, I'm guessing that the fabric over the tank (outside the false rib) did enjoy some level of adhesion to the tank.

  6. #6
    Senior Member efwd's Avatar
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    Default Re: covering fuel tank

    Jim, I assume the prepainted is a reference to Oratex. For that product you apply the glue over the entire tank and you apply glue to the under side of the Oratex. After 24 hour of dry time the fabric is applied and heat with a felt pad is used to activate the glue only around the edges of the tank and pressed firmly down. Now, what your left with is possibly a wrinkled mess over the top of the tank. Fabric is still uncut over the fuel hole. Is that what its called? Anyhow, after the perimeter is curred you return with your heat gun and your felt pad. as you heat the fabric it shrinks tighter but as long as you don't press it down you can proceed to remove the larger loose hills and valleys in the fabric. Once your comfortable with how the fabric is laying, heat it up and press it down. You have to ensure that you have brought the temp up high enough to activate the adhesive but not melt the fuel tank. It isn't difficult. Once you press the fabric to the tank, it is locked down.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  7. #7
    Senior Member 109JB's Avatar
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    Default Re: covering fuel tank

    Whatever process you use you should follow the recommended procedure for covering solid surfaces, just like a plywood skinned wing. Every system will have their own method. I am not familiar with Superflite but as an example Stewart Systems shows how to cover a solid panel here and it is glued, but the glue is applied through the fabric.

    John Brannen
    Morris, IL
    Sonerai IIL (Single Seat)
    Kitfox 3/4 1050 - Rotax 582 (Back Flying and sold)
    Kitfox IV 1050 - Rotax 582 (sold)
    Kitfox IV 1200 Speedster - Rotax 912 UL (project)
    Piper Twin Comanche (Sold)
    Glasair 1 FT (Waiting to start)

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