Vacuum bagging fins question

Discussion in 'Techniques' started by DM1975, Oct 10, 2018.

  1. Oct 10, 2018 #1

    DM1975

    DM1975

    DM1975

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    I have fins cut from 1/8” ply that I’m wonting to fiberglass using a Foodsaver. I’ve already profiled the fins on both sides and was wondering what I should do to prevent any warping under pressure? I’ve watched John Coker’s video on laminating fins but I’m not sure what to use to back the fins with to avoid warping since they are profiled on both sides. Would it be ok to bag them without something backing them?
     
  2. Oct 10, 2018 #2

    JimJarvis50

    JimJarvis50

    JimJarvis50

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    My favorate method for laminating fins is to use a couple of tiles to provide pressure on both sides. Ideally, you want to have the tiles extend past the fins by at least an inch but not much more than that. If you then use relatively thick bagging material, it won't get pulled between the tiles far enough to contact the edges of the fins (i.e., don't use stretchy bagging material for this). If there are areas of the tiles that are not supported, then you can make some supports from your fin material and a little fiberglass so that the tiles won't crack. Both sides of the fin need to be laminated at the same time. Doing one side and then the other will result in a warped fin. With this approach, your profiling of the fin won't matter.

    Jim
     
  3. Oct 10, 2018 #3

    DM1975

    DM1975

    DM1975

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    Thanks. A couple questions if you don’t mind. Are the supports basically just pillars supporting the edges of the tile? Also, what holds the glass to the fin along where the airfoil taper back?
     
  4. Oct 10, 2018 #4

    JimJarvis50

    JimJarvis50

    JimJarvis50

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    Yes, just pillars. I'm not sure what a foodsaver will do with respect to vacuum, but I know that with a high vacuum, the tiles can be broken. I had an unsupported part of a tile - maybe four inches? - and the vacuum cracked that. Like a gun shot.

    This method just works for flat fins. When I do it, I start with a flat fin, laminating the entire fin, and then sand in the profile I want (removing the lamination from the profiled area). I envisioned doing essentially the same thing for your fins. Laminate the flat part and sand off anything that covers or sticks to the profiled section. If your fins have a large portion of their area that is profiled, then you probably need a different method. I still think you will want a method that does both sides at once, as I am aware of a number of examples where people tried one side at a time and failed. It's sort of a rule of thumb not to do that.

    By the way, I typically cover the fiberglass with a layer of peel ply and one layer of breather. I also cover the tiles themselves with a layer of parchment paper. I would then do tip to tip over the laminated fins. If you aren't following up with the tip to tip, then you might use perforated film instead of peel ply to get a smoother surface.

    Jim
     
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  5. Oct 10, 2018 #5

    DM1975

    DM1975

    DM1975

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    Thanks. I’m thinking that maybe if I double up the absorber that under pressure it’ll be enough to compress the cloth to the fins.
     
  6. Oct 14, 2018 #6

    DM1975

    DM1975

    DM1975

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    I used a couple of different layers of used bleeder cloth under new cloth to help with the profiled fins. Seems to have worked well.
    C35A6BBE-A686-482B-93C0-5A02A4FAF3C9.jpeg 1B54BA17-62C5-4A29-BBBB-280CB8CCCDA5.jpeg
     

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