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Some Covering Notes

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  • Some Covering Notes

    Just sprayed the final color coat on the fabric this AM so thought I would put out some notes while everything is fresh. First time covering with time spent at both the Stits and Stewart's seminars at Oshkosh. Both were useful but the Stewart's one more informative on the taping and rib stitching portion. I was undecided after Oshkosh but chose the Stits process because I mentioned my plans to a friend and he donated some extra Stits chemicals from his last project. First piece of fabric went on 2SEP and final color coat applied on 31OCT.

    Materials for the Stits process(I was given a good bit of fabric so don't have an accurate amount for that):
    1.5 Quarts of Poly Tac
    3 Gallons of Poly Brush(one basically for applying tapes and the first brush coat, other two for the two spray coats)
    5 G Poly Spray(make sure to use a stir stick to get the solids off the bottom into suspension. Hardware store shaking doesn't do it. Six coats(three cross coats) is a lot of spraying)
    2 G of color(Poly tone for me, one for the fuselage and one for the other surfaces but it takes 2G to apply 2 coats to all the fabric surfaces.)
    Nominally 3G of reducer. Being in Arizona, I used the high temp reducer and sprayed when I knew I could keep everything in the 75 to 85F range for four hours or so(I.E. early morning or 7 PM at night)
    2 rolls 2" tape(It was pretty straight forward to heat form it around the edges so didn't need bias tape)
    1 roll 3" tape
    1 roll 1" tape
    3 yards of lightweight fabric for reinforcing. I cut a bias tape from this to cover the vertical fin down past the intersection to the top former.
    2.5 G MEK
    2Q of Denatured Alcohol for initial cleaning of fabric between coats.
    Tack rags to clean just before spraying

    Lessons/tricks learned from my first time fabric experience:

    Be very careful to keep the Poly Brush thinned when putting the brush coat on over tapes. It thickens in the can as you progress if you aren't religious at keeping it covered which means it doesn't self level as well. Ridges don't iron out completely and also don't easily sand out during the Poly spray steps. Most imperfections in the Poly brush disappear but not all and the ones that do show through are difficult to get rid of in the later stages.

    Careful wet sanding if there is structure close in behind the fabric. If you are applying a bit of sanding pressure and the fabric hits a hidden tube you will sand off a bit more coating over the tube leaving a depression in the Poly spray coat. It takes a lot of careful Poly spray application and sanding to build it back up and blend it in. The book is clear about staying away from rib stitching but the new lesson learned is to always push in on the fabric to see if there is anything close behind it before sanding.

    Stir the Poly Spray often as the aluminum powder settles out fairly quickly.

    I used the SuperFlight rib stitch knot as it was the easiest I found.

    I put bottle caps over the horizontal stabilizer attach points prior to shrinking the fabric so it could more easily slide over them. Shrank to 250 and cut the fabric as required.

    I used a DevilBiss Finish Line 4 HVLP gun with a 1.3 tip for all coats.

    I used Milton V style airline connectors on the air supply system.

    I covered the fuselage in three pieces(bottom, left, right) with a seam down the top former. Not recommended by the Stits book(definitely a must have) but seems to work just fine. One might replace the top former with a 3/8" or so tube welded to the standoffs to feel better about being "By the book".
    Last edited by BTAZ; 02-17-2017, 10:57 AM.

  • #2
    Great info, BTAZ! It is much appreciated as always.

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    • #3
      Good stuff, thanks for sharing. I wish more builders would report in their notes like this.

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      • #4
        Thanks. great info.

        "I put bottle caps over the horizontal stabilizer attach points prior to shrinking the fabric so it could more easily slide over them. Shrank to 250 and cut the fabric as required."

        Could you explain this a little more.

        Doug
        Scratch building Patrol #254

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        • #5
          The Stits book explains that you can shrink the fabric to 250 over most protrusions before cutting it. I had the front stabilizer mount bolted to the fuselage and of course the rear one is welded in. I put bottle caps(smoothly taped in place) over the ends of these tubes so the fabric could easily slide over the tube end as required when shrinking.

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