PU Foam & Fiberglass House Boat

Discussion in 'Fiberglass and Composite Boat Building' started by williamchill, Sep 8, 2013.

  1. williamchill
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    williamchill Junior Member

    Firstly thank you for taking the time to look at this thread. It's my first!

    I've never built a boat before, but I'm willing to do allot of research, I have built wooden moulds before and I have allot of experience with PU foam and a little experience with fibreglass.

    I like the idea of a house boat made from foam and fibreglass as I'm familiar with these materials. The rest is total mystery at the moment.

    The only costings I have is for the PU foam, 1 Metric Ton costs 3,400 USD, 1 metric Ton of PU foam can make 15 cubic meters, 1 cubic meter weighs 40kg

    How thick the foam needs to be for a house boat pontoon I don't know how to calculate, I guess the weight of the boat will influence the amount of foam needed?

    What weight of fibreglass I would need, and how many layers I guess depends on the strength I want?

    Im guessing to have a house boat that doesn't move around too much I'm going to want some weight.

    So my research starts...

    Any ideas or advice is most welcome!
    Will
     
  2. rwatson
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    rwatson Senior Member

    This density PU doesnt seem suitable.

    If its not closed cell, its a potential water sodden trap.

    Do you have more detail on the structure of the foam you intend to use. ?
     
  3. williamchill
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    williamchill Junior Member

    rwatson, thank you for you fast reply, I currently stock the below specification but I can buy in other specifications I welcome your comment!

    Specifications
    Fireproof polyurethane foam
    
High closed-cell rate,
    Good water-proof 
thermal insulation
    
High compressive strength

    General description
    The product is a mixture consisting of polyether polyols, silicone stabilizer, flame retardant and catalys, using HCFC-141b as foaming agent. It is a light yellow liquid at room temperature. It has been developed to produce B1 (GB8624-1997) class fire resistant outer wall spraying thermal insulation polyurethane foam in conjunction with polymeric MDI.

    Foam Characteristics
    Apparent core density = kg/m3 ≥35
    Initial thermal conductivity = W/(m.k) ≤0.023
    Closed-cell rate = %≥90
    Substrate adhesion = KPa ≥150
    Tensile strength = KPa ≥200
    Water absorption= %≤4
    Dimensional stability (48h)% 80°C≤2.0 / -30°C≤1


    What is it about this density you don't like, I can order up a higher density if its more rigidity your advising?

    Thank you again!
    Will
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    My arithmetical skills may be lacking, but that isn't right, is it ? Anyways, it sounds like near enough to 1kg/cu ft (some would consider such mixing of metric and impereial measure a hanging offence) :p That could not be considered a structural foam density, 2kg/cu ft has some claims to sufficient integrity to have some structural applications, but it is pretty marginal at best. But it starts to have some worthwhile resistance to water absorption.
     
  5. williamchill
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    williamchill Junior Member

    1 Cubic Meter is 35.3146667 Cubic Feet so yes your right the foams weight is 1.13kg per cubic foot.

    However the tensile strength is 240 KPa so it pretty hard = 240 kilopascals = 34.8090571 pounds per square inch (Similar to mild steel)

    Basically its strong and light weight.

    The fibreglass will give it more strength and prevent the 4% water absorption from occurring, to make sure I could give it a coat of polyurea?

    If you guys still think its not going to work I could slice the foam into 5cm (2inch) sheets and then add in a layer of thin plywood between each sheet to give it more strength if you think its needed?

    Is the objection to the foam because its too light? or not strong enough?

    Or is this is total dream?
     
  6. rwatson
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    rwatson Senior Member

    Yes, it is.

    Strength for money, its structural contribution is a lot less than most 'standard' materials.

    There is a precedent for the technique.

    http://www.boatdesign.net/forums/boat-design/bourne-method-boat-building-17840.html




    http://bourneboats.blogspot.com.au/2199/01/building-boat-using-bourne-method.html

    The cost of the hull is a fairly small percentage of the cost of a boat. If you cant insure a boat, because the hull is not engineered by qualified people, then you are risking a big investment.
     
  7. williamchill
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    williamchill Junior Member

    Thank you so much, I find the Bourne boat building method very interesting indeed.

    The Idea for the PU foam house boat wasn't one of my own but came from some research on youtube this morning where I found a nice chap building a house boat from foam and I was hoping for some support for the idea and possibly furthering the idea from the members of this forum.

    From you comments I'm going to continue to research and continue follow the progress of Gotoluc on you tube.

    https://www.youtube.com/watch?v=8_3cMqIAG20&feature=c4-overview&list=UUwXI4FD09cVYyofvzF2sUrA
     
  8. williamchill
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    williamchill Junior Member

    Can anyone recommend a good boat building book for the newcomer? Ideally with some basic engineering principles.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    I'm not sure that lightweight PU foam should be at the centre of the structural design of your houseboat. The stuff is a little more substantial than "fairy floss" ( the Americans might call it "cotton candy"), but not overwhelmingly so ! Which is not to say it doesn't have it's uses in boats, but the structural contribution is not primary. Maybe in a boat like those Boston Whalers it did have, but the density was probably a lot higher than what you envisage using.
     
  10. rwatson
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    rwatson Senior Member

    It was, and we have a lot of posts about how badly the Boston Whalers became sodden wrecks.

    Its easy to forget how much pressure develops on hulls from the water, even a foot or so down. Remember your ear drums in the swimming pool.

    Put this cotton candy in water absorbing polyester skins, and its a recipe for disaster.
     
  11. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Foam core sandwich construction, is fairly well understood and uses straight forward principles and formulas, to get predictable results. Predictable results are the primary goal, when engineering composite structures. You can "play" with it, if you like, but unpredictable outcomes, as a result of not understanding the engineering involved or worse, just taking a good guess, generally ends up with lost effort and materials, hopefully not lives too. Simply put, if you want a structural panel, you'll need a structural foam. 5 pound (2.2 kg) foam is the minimum in this regard, with much higher density foams available for tougher applications. Calculate the loads you'll have and use the appropriate core. There's really no short cut to this, if you expect to have predictable results.
     

  12. congellous
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    congellous Junior Member

    Foam sandwiched between say diolen or e-glass epoxy will give excellent stiffness/ weight with how adhesive the core is to the shell
     
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