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. redreuben
    Joined: Jan 2009
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    Location: South Lake Western Australia

    redreuben redreuben

    Oh that’s so funny, was on my phone in waiting room so what can I say but......Doh !
     
  2. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    I don't get it, what's so funny?
    Were you on any kind of gas in that medical waiting room?
     
  3. redreuben
    Joined: Jan 2009
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    Location: South Lake Western Australia

    redreuben redreuben

    Bluebell;
    I read Austria as Australia
     
  4. Burger
    Joined: Sep 2017
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    Likes: 19, Points: 8
    Location: Australia

    Burger Junior Member

    My gut feeling would depend on my budget.

    For a 35'+ expensive boat, foam. Weight and resale advantages. High cost and build time disadvantages.

    For a smaller simpler boat, ply. Lightest, cheapest, quickest and simplest build.

    Strip planking is not an option for me, way too time-consuming, messy, wasteful, expensive.
     
  5. redreuben
    Joined: Jan 2009
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    redreuben redreuben

    I'm not going to go over it yet again but strip planking need not be painstakingly slow.
    Hint; Nail all the strips on at once (double headed nails) and mass glue the entire hull.
     
  6. Heinrich Poigner
    Joined: Jul 2018
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    Location: Austria

    Heinrich Poigner (He likes boats(and maths))

    Again I might have said this before, but in europe plywood is not as cheap a material as elsewere.
    As far as I know ply and foam do have ridiculously simmilar prices for the same volume and simmilar quality (pleas prove me wrong an show me something affordable if you know something!)
    (follow up question: how about kombinations? (strip+ply))
    is there a usable estimate fore comparing two simmiler parts out of ply+glass and foam+glass by weight? (wall thiknes +-10%)

    also:

    this doesn't seem to be all that complicatet (obwiously with more difficult forms it would be more tedious (but so it would for ply))
    If a boat was designd to be built in ply it will probbably be best to build it that way, if it was meant to be built in foam .... you know where I'm going with this
     
    Last edited: Jul 24, 2018
  7. Heinrich Poigner
    Joined: Jul 2018
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    Location: Austria

    Heinrich Poigner (He likes boats(and maths))

    a thing you reminded me of: I've read that only boats above ~10m(~32-33') would benefit from being built in foam over massiv glass, how come?
     

  8. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    I am building a 10M foam boat, but foam is slower than ply to build, in general terms , and requires a jig, in general terms.

    Now that I have made foam sound less than ideal, foam is generally lighter, absorbs less water, and has 'better' impact resistance.

    Foam generally requires a thicker glass which also uses more resin, so that is a cost adder over ply.

    I was onboard Meadowhawk, a Richard Woods Romany, last weekend and the boat is a foam hull with ply decks. He said he used ply on the decks for speed of build.

    Consider plywood for a moment; for smooth transistions at 8' ends, scarfing is generally done. In foam, butt joins are used and since the glass is thicker; no fairing is generally needed, if you use a jig. So plywood can be harder to use for long panels.

    You have to determine the best course on a design basis, moreso than build.

    Foam has lots of good properties for boats where hull spaces are lived in. Quieter, less condensation...

    I would be very surprised if you ordered materials to build hulls in ply vs foam that the foam would come in lower. I have a feeling you are discounting resin and glass use costs rising for foam builds. Foam, done right, really needs infusion or vac bag. Sure you can hand laminate it, but the properties of hand laminated foam are not the same as vacuum built foam.

    My foam build uses a vac table 10.16M long. Building the table took a couple weeks. Not needed for other methods, but I tell you so you realize it as cost. The materials for the table were around $1000. Ply build table is my cutting table, so the 1k and two weeks are absolute differences. For my foam build a jig was used. The jig cost of materials and cutting was about $2000 and another couple weeks jig setup. Even the teardown of the jig was a day.

    Find the design you like. The options might not be available even. Lean to foam for habitable hulls.
     
    Heinrich Poigner likes this.
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