Warped Flat Panel Problems

Discussion in 'Fiberglass and Composite Boat Building' started by pescaloco, Jan 18, 2014.

  1. pescaloco
    Joined: Feb 2006
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    Location: so. california

    pescaloco Senior Member

    Hey Guys

    I am having an issue trying to make my tank lids flat

    hand lay up 1/2 in Corecell foam laminate schedule 1.5oz matt / 1708 cloth / 1.5oz matt Glassed one side and was able to keep the panel flat.
    Glassed the other side after a few days same schedule laminate, kept catalyst ration just above 1 % (VE resin) and the panel warped like a bananna
    why does so much shrinkage occur that the panel warps so badly

    any suggestions on how to laminate a flat panel in this manner

    Thank you
     
  2. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    Maybe try molding them on a contact surface like melamine sheet/glass & do in the same day, wax-release agent - gelcoat- skin-core-skin, maybe some peelply or peelply & vac bag, Demold after a couple of days.My theory is that one side has set to size after cure cycle & your second side has done this outside the firsts & ended up "smaller" so it must bend............... across the 1/2 core.
    I've had a banana panel when I had a neighbor complaint & backed off for a couple a days....... but ended up using it as part of the hard deck for my seawind 24.
     
  3. groper
    Joined: Jun 2011
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    groper Senior Member

    yep - if you want them dead flat, vac bag em both sides in 1 shot - they come out dead nuts flat...
     
  4. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    It is like ply, you must put the layer on each side at the same time to even the stress. If you do one side then the other it has time to move relative to the core part. Timber is just the same as foam in this sense - a little temperature diffrence or moisture and it will move slightly.
     
  5. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    The delay of several days seems to be the cause of the problem, I can't recall having such problems, probably because the flat panel was flipped while still "green" and the other side done the same day. But it is something to be aware of, for sure.
     
  6. pescaloco
    Joined: Feb 2006
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    pescaloco Senior Member

    I will have to do them in one go around

    Thanks to all that replied

    I'm not versed in vacuum bagging but have an understanding of the process
    Using Poly or VE resin is there enough time to glass both sides of a 70 x 21 inch panel, set the peel ply and tape the bag down before the first side is starting to go hard
     
  7. waikikin
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    waikikin Senior Member

    There's a couple more layers of stuff in the bag, some perforated film & some bleeder fabric/vac interface- you need this so there's a a pressure difference across the membrane of the bag, the core if plain sheet should have small holes at 4" centers minimum if your bedding into chopstrand or core bedding putty, should be no issue on laying up that 21" width but you can do the first skin & bed the core with the bag to it & then once gelled(on the part-not the pot) pull the bag on three sides & do the second skin after lunch. No need for massive vacuum esp with styrenated resins, maybe 2- 3-4 psi difference across the membrane.
    Main thing to work fast is to get the resin on the job, do your calcs on quantity & have all materials standing by in order then go for it resin & glass let it soak, bubble bust & move...............to the next.
    Jeff.
     
  8. groper
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    groper Senior Member

    Yep - what jeff said..

    Or you can retard your VE resin- ive never done it with PE tho... i used to get a couple of hours gel time with a VE resin and a few drops of retarder in it...
     
  9. pescaloco
    Joined: Feb 2006
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    pescaloco Senior Member

    Groper thanks,
    I will look into that I have not used retarder


    Waikikin thanks for the break down
     
    1 person likes this.
  10. FishStretcher
    Joined: Oct 2011
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    FishStretcher Junior Member

    I recently had success doing both sides at once. I did a slow cure with AOC vinylester with 0.5-0.8% MEKP. Very fresh resin, and at ~60F ambient. I skipped the separate CSM- that is extra difficulty. I did two layers of 1708 DBM- with the stitched on layer of mat. Lots easier to work with and uses less resin.

    I laminated one side of a 24 x 60" panel, put down peel ply, smoothed on 2 mil home depot poylethylene sheet, flipped it over, and did the other side. Total time 60 minutes. For the 2nd side, I mixed SLIGHTLY hotter to get it to cure in sync (ish) with the first side. It came out dead flat. If I had a real laminating table, then the occasional wrinkle from the poly sheet could have been eliminated by not having the poly sheet. But for under deck bulkheads, it came out great.
     

  11. FishStretcher
    Joined: Oct 2011
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    FishStretcher Junior Member

    Just to be clear, my " laminating table" is a sheet of 4 x 8 OSB over sawhorses then shimmed flat. With 4 mil poly stretched over it. I am not doing cosmetic panels.
     
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