Sandwich panel origami...

Discussion in 'Fiberglass and Composite Boat Building' started by groper, Jun 9, 2012.

  1. groper
    Joined: Jun 2011
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    groper Senior Member

    Ok, i made a bunch of test panels to make sure i could kerf cut my infused panels and fold them into the shape. However now that i have infused a 6m long panel, its too damn stiff to fold!

    Ive cut right thru the top laminate and core with about 1mm of corecell left intact along with the bottom laminate. The bottom laminate left uncut where the kerf cuts are is 2250gsm of warp triax (no fibres running across the cuts, only parralell to the cuts and at 45deg). In a small panel, this was quite easy to bend by hand... this big panel, not so...

    So i thought about heating up the bottom laminate to soften it, then apply pressure to fold it, and finally hold it in place with rachet straps or something whilst it cools down... will this work or is there a better way???? This panel is 20ft x 5.5ft, weighs 66kgs, and i only have myself and the help of my retired, rather elderly father... so man handling it isnt easy... ideas?

    [​IMG]
    [​IMG]
     
  2. groper
    Joined: Jun 2011
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    groper Senior Member

    ok panel has been flipped over so the sides i want to fold up, sag down whilst its supported from the center. Ive taken it outside and tomorro when the sun hits it, hopefully it will heat up enough so that it will soften and bend down under its own weight... then i should be able to wrap some straps around it and pull/hold it in the folded position whilst i glass over the kerf cut area... well thats the plan for now anyways :) tomorrow will tell...
     
  3. brian eiland
    Joined: Jun 2002
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    brian eiland Senior Member

    I'm going to follow your subject thread when I get a bit more time.

    I'm interested in the subject matter for a new project i'm investigating.
     
  4. rawleyjerel@yah
    Joined: Apr 2012
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    rawleyjerel@yah Junior Member

    thats a tough situation!! if that doesnt work try making more cuts inbetween the ones you already have,like a triple cut core! that should give enough flex to allow for bending.
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    You're going to eat up a lot of resin in those saw kerfs, I hope weight savings isn't an issue.
     
  6. groper
    Joined: Jun 2011
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    groper Senior Member

    The kerfs will close up with the fold, not open up... i need to fold it the opposite way its sagging in the photo... ive flipped it over so it hangs the right way now...

    Any one else worked with large folded panels like this? any tips or tricks? i think for teh next one i might just leave out teh core all together and leave it as a single skin laminate in the area i kerfed where i need the fold. then once its in folded into shape, add some foam strips or coremat or whatever i can get in there afterwards... i think this would save all the cutting and make it easier to bend...?
     
  7. gypsy28
    Joined: Mar 2010
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    gypsy28 Senior Member

    Hey Groper, I may have missed it elsewhere but what are the panels gonna be for?

    Cheers
    DAVE
     
  8. groper
    Joined: Jun 2011
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    groper Senior Member

    these panels are the developable part of the bilges of my catamaran hulls... i need to join these to the front sections which have compound curvature, so im molding these separately and join them afterwards.

    just waiting for the sun to hit them this morning.... if this doesnt work, ill have to rout out some more foam and essestially turn it into a single skin laminate, then add some core material back in there after its bent i think?
     
  9. AndrewK
    Joined: Mar 2007
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    AndrewK Senior Member

    I use electric blankets with insulation on top of them to keep the heat in.
    Make a few radiused formers for the shape you want to make sure you have the same radius along the length.
    I also use electric blankets to post cure panels on the table or other smalish parts, just finished one half of my catamaran deck house top. Eelectric blankets on top heat lamps underneath, cured at 65'C for 24hrs. Cheap too as blankets are only 60W.
     
  10. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Any concerns about strength across the bend if the are no fibers running transversly in that area? Or do you later add material for transverse strength?
     
  11. groper
    Joined: Jun 2011
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    groper Senior Member

    No, the bulkhead frames run transversely in the hulls, so a warp triax laminate is fine here...

    well the sun hit it, and this is what happened...
    [​IMG]



    Flipped it over, and now i have the bottom 20ft of 1 hull complete with extra reinforcing for beaching and recessed edges for secondary joining of subsequent topsides, transom and front hull section :) pretty damn fair too...

    [​IMG]

    Whilst i was waiting, i prepared the core for the second hull, infuse that tomorro... twas a good day :)
     
  12. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    So what was the other tool for? Or are you now only using part of it? Jeff.
     
  13. groper
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    groper Senior Member

    heh, yep... the plan (for now) is to only use the front end of it to do the compound curved part... as this rear part was developable, i decided to do it on the table so it came out fair... i could just antifoul it right now, its that smooth... so the direct female mold was a bit of a WOFTM, but you live and learn i guess...
     
  14. tunnels

    tunnels Previous Member

    So cutting part way through did the trick ??how stiff was it to bend the foam and the glass ?? :?:
     

  15. groper
    Joined: Jun 2011
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    groper Senior Member

    Got the other hull laminate stack layed up aswell today, most productive day yet... This time im going to infuse the panel a bit differently... The part of the core that i kerf cut, ive completely removed this time, so i only have a single skin laminate where i need to bend it. This will save me cutting all those grooves. Then i just need to figure out the best way of bonding the core back in this area once its bent, and glassing it over...
     
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