foam core vs cedar strip vs ply

Discussion in 'Fiberglass and Composite Boat Building' started by Heinrich Poigner, Jul 3, 2018.

?

What would you decide by "gut" feeling?

  1. Foam

    75.0%
  2. Cedar

    25.0%
  3. Plywood

    0 vote(s)
    0.0%
  1. Heinrich Poigner
    Joined: Jul 2018
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    Location: Austria

    Heinrich Poigner (He likes boats(and maths))

    I was wondering how much weight could be saved when using foam instead of cedar (or ply) in a onetime build (without molds).
    I'm thinking about a 6-8m long, 2-2.5m wide and somewhere between 500-700kg
    somewhat quicker daysailer or cruiser (probably tailorable).
    Are there any special things to worry about?
    regards
    Heini :D
     
  2. fallguy
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    fallguy Senior Member

    If you want to build without moulds; how would you do so with foam or strip?

    I am not familiar with any strip boats not made on a mould or strongback at least.

    Foam boats would require some type of jig at a minimum or same.

    Plywood stitch n glue is the only thing I have heard of that is done sans moulds.

    I suppose a foam panel could be stitched and glued, but I have not seen it done.

    I am just a builder and not a designer and don't have the breadth of experience as many of the posters here; so I could be wrong.

    I recommend you build stitch n glue plywood.
     
  3. Heinrich Poigner
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    Heinrich Poigner (He likes boats(and maths))

    Yes right, I can't just suspend midair.
    I ment that I would'nt want take in akount one of those smoth female molds where a kapable builder could implement all those great things as honeycomb, integratet foam coars, Balsa and so on ...

    (and since I'm planing to build this a few years down the road after hopefully finishing my degree ... I guess "mere" stitch&glue might not satisfy my ego by then:p)
    (I hope nobody deems this last bit insulting)
     
  4. redreuben
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    redreuben redreuben

    Fall guy,
    Perhaps the op would be referring to female grp production moulds ?
     
  5. fallguy
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    fallguy Senior Member

    Fair enough, but important to be clear. Not too many home builders would build a production mould, so my brain didn't go there.

    I am building a developable panel foam/epoxy boat in a female jig.

    I recommend you develop a list of requirements first; speed, accomodation, trailer or moored, etc. The more comprehensive the list; the better.

    Then find a boat plan to suit.

    All the methods you describe can be used to build great boats.

    Some are easier than others.
     
  6. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    I would vote for all three,
    but that's not an option so I didn't vote...

    It really depends on the boat.

    Then I voted.
    For foam because hardly anyone is using it and it is much feared and misunderstood.
    Viva la Foam!
     
    fallguy likes this.
  7. Heinrich Poigner
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    Heinrich Poigner (He likes boats(and maths))

    I guess the two main criteria are that I can get it out the door (3x3m) and that it trailerable since the next puddle where I could even think about splashing it is like an hour away without reasonable storage there
     
  8. Heinrich Poigner
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    Heinrich Poigner (He likes boats(and maths))

    Also how light of a hull could you expect at such measurements to still be within the error of a construction over jigs after applying those masses of fairing compound?
    (without ballast, rig, people, ...)
     
  9. redreuben
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    redreuben redreuben

    Heinrich, I just noticed your in Australia, bonus !
    Forget cedar here the price has gone ridiculous however Pawlonia or Kiri is cheaper lighter and more pleasant to work with.
     
  10. Heinrich Poigner
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    Heinrich Poigner (He likes boats(and maths))

    @redreuben
    :D:D:D
    please read it again it is the most cliche mishap (tip I'm realy realy landlocked and the closest resonable/fun option is the Hungarian sea ;))

    but still gona look into the other options you sugested
     
  11. fallguy
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    fallguy Senior Member

    I am not certain you ought to expect an answer.

    Find a boat you like that you can build first. Not all designs have all options, and modifying designs to your preferred options is not easy.

    Foam is lighter, but to pin how much without a design would be a leap. For smaller boats, the amount of weight difference in absolutes will not be high. I have not seen a lot of small boat plans in foam; perhaps for that reason. The cost of foam and the ease of building smaller boats in ply is somewhat hard to beat. Doesn't mean it isn't done.

    All generalizations, but ply is hard to beat for small monocoque hulls.
     
  12. BlueBell
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    BlueBell Ahhhhh...

    Fallguy,
    With all due respect ( and then some ) I couldn't disagree more.
    I love foam construction.
    There is still a place for me for stitch and glue but I may never build another.
    Engineering the forces, loads and behaviour are challenging but this is my future.
    Cheers
     
  13. Heinrich Poigner
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    Heinrich Poigner (He likes boats(and maths))

    But please consider that in central europe the price comparison of foam-ply is currently the other way round (especialy anything one would want to build with)
    Its been ment more from a design perspective instead of looking at plans to build
     
  14. fallguy
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    fallguy Senior Member

    I just said I haven't seen lots of small boat plans in foam and hypothesized a reason that it is simplicity to build.

    I didn't say ply was better.

    I am building in foam.
     

  15. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    I simply, and respectfully, disagree, okay?
     
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