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  1. #1
    LargeScale88's Avatar
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    Sig Koverall Application Process

    Hi everyone. I'm just finishing an airplane up and I've decided to cover it with Sig Koverall and nitrate dope. Having not used this covering for several years, I'm a litte rusty on the process, so I just wanted to clarify the standard process for putting this stuff on properly.

    Ok, heres what I can remember:

    1. Apply 2 coats of unthinned nitrate dope to framework (except ribs, attatch cloth to ribs after shrinking the cloth)
    2. Lay cloth down, apply two more unthinned coats to secure the cloth to the framework
    3.Thinthe nitrate dope about25 thinner and 75 nitrate, using sig thinner
    4. Apply 2-3coats to seal the cloth and fill the weave
    5. ApplySig supercoat and color to finish off the model, orstart painting right on top of nitrate dope to fuel proof it

    Can someone maybe correct me on number 1, I read and watched a video and they both stated not to attatch the cloth to the ribs until after its shrunk, and the reason being so the cloth can shrink the way it wants to, and if its tacked down, it could be "restricted" and put an unwanted warp or twist into the wing.

    Thanks much!

    Jason

  2. #2

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    RE: Sig Koverall Application Process

    In step 1 you can apply the nitrate to the ribs as well as long as in step 2 you only adhere the Koverall to the perimiter of the framework. Shrink and then dope the whole surface. By doing the ribs, you will get better adhesion.

    Paul
    Gosh, model airplanes are not a matter of life and death - they are more important than that!

  3. #3

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    RE: Sig Koverall Application Process


    ORIGINAL: LargeScale88

    Hi everyone. I'm just finishing an airplane up and I've decided to cover it with Sig Koverall and nitrate dope. Having not used this covering for several years, I'm a litte rusty on the process, so I just wanted to clarify the standard process for putting this stuff on properly.

    Ok, heres what I can remember:

    1. Apply 2 coats of unthinned nitrate dope to framework (except ribs, attatch cloth to ribs after shrinking the cloth)
    2. Lay cloth down, apply two more unthinned coats to secure the cloth to the framework
    3.Thinthe nitrate dope about25 thinner and 75 nitrate, using sig thinner
    4. Apply 2-3coats to seal the cloth and fill the weave
    5. ApplySig supercoat and color to finish off the model, orstart painting right on top of nitrate dope to fuel proof it

    Can someone maybe correct me on number 1, I read and watched a video and they both stated not to attatch the cloth to the ribs until after its shrunk, and the reason being so the cloth can shrink the way it wants to, and if its tacked down, it could be "restricted" and put an unwanted warp or twist into the wing.

    Thanks much!

    Jason
    1. I use 50/50 thinned dope, both for prepping the structure and on top of the covering. The comment about connecting to the ribs after shrinking means to adhere the perimeter first, then shrink out any wrinkles, then go back and adhere (dope) the ribs. This allows the fabric to "move" when shrinking.

    2., 3. 4. Again, I use 50/50 thinned, but I paint with latex, and I want the fabric to show. If I were making a "non fabric" look, I would fill the weave more. I use laquer thinner from Lowes or Home Depot with nitrate dope. Don't use it with butyrate or Stix-It, however.

    I also use SIG Stix-it on the structure perimeter and any areas I need axtra adhesion, such as wing tips, edges, etc. Stix-It is billed as a heat sensitive adhesive, which it is, but I think of it as "super dope". When I have the Stix-It on the framework, I can go back an touch up the adhesion with just thinner, if needed. Also, it is a good idea to "rub in" the dope as you apply it, just helps make a more positive bond.

    In general, I keep in mind that this product has no adhesive on the covering, I need to apply the adhesive to the framework. The principal in this technique is to apply dope over the covering so that it bleeds thru and combines with the dope already on the frame. When you apply the dope over the covering, at the perimeter edges, be sure to dope past the edge of the structure. This assures the fabric has a little fill to it so when you go to trim it, it cuts cleanly. Cutting the dry fabric gives lots of frizzy edges that you do not want.

    I have heard people say Koveral is a lot of work. There is a lot to do, but if you enjoy doing it, there is a lot to enjoy!

    So, enjoy!

    Sometimes, things are exactly as they appear to be.

  4. #4

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    RE: Sig Koverall Application Process

    A number of people use water based polyurethane now with good results. The advantage is that it is low fumes so you can use it in a fairly confined space. The disadvantage is that subsequent coats do not rewet the ones underneath once they are dry, so fixing mistakes could be harder.
    No kid, I said break ground and fly into the wind!

  5. #5

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    RE: Sig Koverall Application Process

    I tested the WB Puly and found it isnt fuel proof for glow. Was disappointed in that.
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  6. #6
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    RE: Sig Koverall Application Process

    You absolutely should apply dope to the ribs, especially if you have cap strips. If you don't the dope will get drawn through the fabric into the bare wood and leave pinholes where the ribs or cap strips are. Speaking from experience on this one. Also, at least 3 coats, better is 4 coats nitrate on the bare wood. I very lightly sand after 2nd and 4th coat.
    For a kit you are, and to a kit you shall return.

  7. #7

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    RE: Sig Koverall Application Process

    The poly isn't supposed to be a fuel proof top coat. It's just used as an adhesive instead of nitrate dope. You still have to prime and paint the model when using water based poly.
    No kid, I said break ground and fly into the wind!

  8. #8
    LargeScale88's Avatar
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    RE: Sig Koverall Application Process

    Thanks everyone!

    I've read stuff about the Polyurethane not being that good, but also read is very good (never hurts to try though!).

    Jason

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    RE: Sig Koverall Application Process

    As an adhesive for the Koverall, WBPU is good enough. As a topcoat, it stinks on anything but an electric.
    No kid, I said break ground and fly into the wind!

  10. #10
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    RE: Sig Koverall Application Process

    I curious to how to apply Koverall onto the fuselage or any area that is solid? I will be using the nitrate dope and koverall on mine but I can't find anything on how to apply it to the fuselage. Do you guys have any other tips on using this stuff?

  11. #11

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    RE: Sig Koverall Application Process

    After you have applied the coats of dope to the solid area, you pretty much paint the fabric on. Start with dry fabric, and go from one end to the other with a wet brush. The surface tension of the liquid will cause the fabric to stick, and you're done
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  12. #12
    LargeScale88's Avatar
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    RE: Sig Koverall Application Process


    ORIGINAL: DJokr

    I curious to how to apply Koverall onto the fuselage or any area that is solid? I will be using the nitrate dope and koverall on mine but I can't find anything on how to apply it to the fuselage. Do you guys have any other tips on using this stuff?
    Exactly what RV7garage said, no need to do any shrinking at all. You only shrink the cloth with an open bay wing or a non-sheeted fuselage.

    Correct me someone if I'm wrong

    Thanks

    Jason

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    RE: Sig Koverall Application Process

    Wrinkles can form on solid surfaces. They will shrink out with a heat gun.
    Sometimes, things are exactly as they appear to be.

  14. #14
    LargeScale88's Avatar
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    RE: Sig Koverall Application Process


    ORIGINAL: RCVFR

    Wrinkles can form on solid surfaces. They will shrink out with a heat gun.
    I always thought that once you apply the dope if the cloth is smooth on the surface you won't have to worry about wrinkles?

    Thanks for the correction

    Jason

  15. #15

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    RE: Sig Koverall Application Process

    All solid surfaces are not flat. Some are round, some are compound curves. Your advice to DJokr was that only open bay covering needs to be shrunk tight. Not so, at least from my experience. Your experience may differ.
    Sometimes, things are exactly as they appear to be.

  16. #16
    LargeScale88's Avatar
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    RE: Sig Koverall Application Process


    ORIGINAL: RCVFR

    All solid surfaces are not flat. Some are round, some are compound curves. Your advice to DJokr was that only open bay covering needs to be shrunk tight. Not so, at least from my experience. Your experience may differ.
    Correct!

    I say experiment with different methods until you find what works best for you.

    Jason

  17. #17
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    RE: Sig Koverall Application Process

    I'm glad you brought up the curved surface, I didn't think about that. So what I'm gathering here is: You can shrink if you need to on a solid surface but it's not necessary, but in cases of curved and compound curves you will most likely have to, depending on how much curve is there. This is what I'm working on but I have another model ( Chin model Cessna 337) that is a lot more detailed when it comes to covering. I plan on using the Koverall on it too. This is the reason I'm asking, I want to learn how to cover on this model before I try it on the 337. Thanks to all that have responded.



    Any tips on areas like this? This is where the aileron will be.


  18. #18

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    RE: Sig Koverall Application Process

    If you want the Koverall to really stick then use SIG Stix-It or similar. I 'burnish' it thru the fabric and into the wood with acid brushes. Dope works very well but takes a little longer. Here is a Fokker Drl wing covered with just one piece of Koverall. The top, bottom, tip, aileron and center section cutouts and center fairing were covered- one piece. It took some doing but is possible. I think you could just about cover a bowling ball with it!

    For your wing it is much easier if you remove the hinges.

  19. #19

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    RE: Sig Koverall Application Process

    If your hingesare glued into the wing at this point, you can cut a piece of koverall just large enough to cover the trailing edge verticalsurface. Cut slits in thekoverall to allow the hinges to protrude, and dope the koverall down. Trim it before covering the top and bottom of the wing. Your fabric covering on the top and bottom of thewing can overlap the trailingedge fabric that is doped down.

    Joe
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  20. #20
    DJokr's Avatar
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    RE: Sig Koverall Application Process

    The hinges aren't glued in, I just forgot to take that one out before I took the pic. I was talking about the corner and the surrounding area.

  21. #21

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    RE: Sig Koverall Application Process

    I would still do the same thing. I would cover the trailing edge of the wing in front of the aileron and follow the rib out to the end of the rib at the end of the aileraon bay. Dope it down and tim it back to the balsa edge.

    Joe
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  22. #22

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    RE: Sig Koverall Application Process

    There is a lot of good info here but aI'm confused on one step - shrinking.

    Is the shrinking done as a separate, independant step (say, by using water, like we used to do with silkspan) or is it the application of the thinned dope that does the shrinking and filling together.

    Sorry to ask an anal question,

    Bob
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  23. #23
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    RE: Sig Koverall Application Process

    Hi Bob,

    The Koverall is shrunk using heat from a heat-gun or iron. I generally seal / glue it around the edges then shrink it with a heat-gun, then dope the entire thing with a 50% dope 50% thinner mix. When you do that with something like a wing, the dope will bleed through and adhere to the ribs.

    Thanks,
    Russ

  24. #24

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    RE: Sig Koverall Application Process

    Thanks, Russ. I didn't know that it was heat shrinkable.

    Bob
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  25. #25

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    RE: Sig Koverall Application Process

    Koverall is a polyester fabric, so it will shrink with heat like any other polyester material will. The plastic film coverings are polyester too for the same reason.
    No kid, I said break ground and fly into the wind!


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