Wrapped foam plank

Discussion in 'Materials' started by Owly, Jun 6, 2018.

  1. redreuben
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    redreuben redreuben

    750 each side. You’ll have different resin usage depending on the laminating technique. These figures are comparing panel properties, like for like but yes I would think you could go a bit lighter on the inside of a hull. I’d be inclined to go triaxial outside and biaxial inside. Both run fore and aft. Double bias tape under bulkhead landings perhaps ?
     
  2. Owly
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    Owly Senior Member

    All afternoon while driving &c, I pondered the Kelsall material and his compound curves using darts in the foam. No matter how I look at it, I cannot imagine the glass / resin layup on the outside only where the compound curve is to be made being able to expand and shrink. whatever ability it has to do that will be extremely small.

    I looked at mdf with a melamine surface, which some designers recommend for giving a smooth surface for a layup. It's flexibility is extremely minimal. It's really suited only to a flat table. Plywood or OSB with a very smooth linoleum over it would seem to give an extremely good unbroken surface for the full needed length and width with no seams. A surface that could be bent and twisted smoothly with stringers under the plywood, to a desired shape for a hull side with no compound curves. I like the idea of the wrapped plank construction for a single curve sheet side. An alternative might be to use a narrow glass tape between each plank if such a tape were available in a bias tape at so narrow a width. The diagonal wrap however gives the desirable bias orientation of fibers for the application. My inclination is that if I wanted a compound curved bottom with rounded corners, it would realistically need to be planked and finished by hand. The bottom however is a relatively small panel on a cat.
    I've been wondering if one can reasonably "rebate" an area of foam along the edge of an infused panel to a depth that allows for the glass plies of the seam. The thought is that if one made the sides, and fitted and shaped the bottom in place, the plies on the bottom would lay over the plies on the side at the seam area and be close to flush due to the rebate. The resin could be hand laid and vacuum bagged. Making and finishing a shaped bottom would take far more time than making and assembling both sides in their entirety........ There clearly are advantages to having some shape to the bottom due to the inherent stiffness.

    H.W.
     
  3. fallguy
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    fallguy Senior Member

    Formica can take curves. It hs different names in Canada and elsewhere.

    Linoleum or vinyl stick to epoxy like you wouldn't believe, ime.
     
  4. redreuben
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    redreuben redreuben

    Your planking idea has reminded me of the trimaran Balina/Bullfrog/Verbatim/Australia’s Child.
    When Ian Johnston built it from strip planked balsa, he cut the balsa into 1 metre planks and the butt jointed them with epoxy to full length before stripping. The idea being to limit water wicking along the length should they be exposed.
     
  5. redreuben
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    redreuben redreuben

    Owly, what have you got against wood strip for the curvy bits ?
     
  6. redreuben
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    redreuben redreuben

  7. fallguy
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    fallguy Senior Member

    Your math is wrong.
    750g/m^2 is 22 ounce fabric at 60% of the layup is 36.67 ounce per yard each side or 8.15 ounces per square foot both sides or 16.29 pounds for 4x8 plus 12mm foam core at say 7. Total is 23.5 pounds or so.

    Its late. I could be off. Corrections welcome. Iphone math is always subject to errors at this hour for me.
     
  8. fallguy
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    fallguy Senior Member

  9. redreuben
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    redreuben redreuben

    Off the top of my head I haven’t looked at the site for a while.
    Female batten moulds, 1 layer of 4mm ply, stringers, glass, furniture, turn, glass outside and fair.
    Interesting but sounds heavy.
    Basically a glass hull with a 4mm core.
     
  10. Niclas Vestman
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    Niclas Vestman Junior Member

    I think the 750gsm quoted from KHSD, was glas only, + whatever resin is needed. So + another 1500gsm hand layup total för both sides.
     
  11. redreuben
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    redreuben redreuben

    If you can get 1:1 ratio over foam your a better man than me !
     
  12. Niclas Vestman
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    Niclas Vestman Junior Member

    Nahh.... pretty sure that's not the case. I'm just way more of an hopeless optimist ;-) Just taking a guess, and trying to get the guesstimate inside the ballpark.
     
  13. fallguy
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    fallguy Senior Member

    Oops, I used vac.

    Who wouldn't?
     
  14. redreuben
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    redreuben redreuben

    Fallguy; so you bagged a wet laminate over foam ?
    And what fibre/resin ratio were you able to get ?
    Epoxy or VE ?
     

  15. fallguy
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    fallguy Senior Member

    I get 35% resin to total (epoxy resin plus glass). It scares me a little to run that well, but those are my numbers.

    It will help a bit with the hand taping I run with mat backed tapes. Those are resin gulpers, but hold their shape well. Running 32' joins doesn't afford a snaky biax tape.
     
    Dejay and Niclas Vestman like this.
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