Fibre Re-Inforced Thermoplastics & Vinyl Wrap

Discussion in 'Materials' started by PI Design, Oct 4, 2012.

  1. PI Design
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    PI Design Senior Member

    Hi,

    I am interested in designing a 14ft dinghy to be made from a reinforced thermoplastic, such as Twintex or Polystrand.

    Does anyone here have experience of such materials? I have heard that they degrade badly with UV, so that the apparent material advantages are undone somewhat by the need to cover in gel coat. I was wondering whether it would be possible to avoid gel coating by using a vinyl wrap. In fact as vinyl wraps are a bit temporary, it would probably something a little tougher such as PU.

    Does this sound doable/sensible?

    Thanks.
     
  2. jonr
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    jonr Senior Member

    Which thermoplastic are you considering? Some (like PP) can be painted.
     
  3. upchurchmr
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    upchurchmr Senior Member

    You are going to spend a lot of money coming up with a new acceptable material.
    Go to yostwerks.com to look at his SOF (skin on frame) boats, or Dave Gentrys website, or kudzu.com, or www.gaboats.com. You might also look at kayakforum.com. There are lots of articles on skin boats, but search thru the threads before you start asking questions. Lots of stuff there.

    Sunlight kills most every plastic, why do you think vinyl wrap is different?
     
  4. PI Design
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    PI Design Senior Member

    It's not skin on frame I'm trying to achieve, more llike a normal grp boat but with polypropylene and with a wrap rather than gel.

    Jonr, probably pp, but was thinking paint would be more expensive. I like the idea of a vinyl wrap as possibly a clean and quick solution, but figured PU is more scratch resistant.
     
  5. upchurchmr
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    upchurchmr Senior Member

    Polypropylene is very poor in strength and stiffness, and it doesn't bond well.

    Almost any unreinforced plastic will be flexible and heavy without glass or graphite reinforcement and it needs to be a high % of the skin (50-60% or higher).

    You don't need gelcoat for the outside of a fiberglass boat, it is well understood that you can save weight if you just paint a boat instead of gelcoating.
    If you have a plastic boat it does not need gelcoat.
     
  6. jonr
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    jonr Senior Member

    You could also get PP that is treated for UV resistance. That plus a topical coating like "Aerospace 303" might be enough.

    People are building useful boats out of PP, ABS, HDPE and Polycarbonate, even without fibers. Long fiber thermoplastic composites are replacing steel and aluminum in some applications.
     
    Last edited: Oct 6, 2012
  7. PAR
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    PAR Yacht Designer/Builder

    Just hold the polypropylene sheeting up to the sun light. See anything? So will the epoxy . . . even with oil concoctions such as 303 on it.
     
  8. upchurchmr
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    upchurchmr Senior Member

    jonr,

    What useful boats?
    Next we will have a discussion about the meaning of "useful".
     
  9. PAR
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    PAR Yacht Designer/Builder

    Most boats aren't useful, as this economic environment has proven quite handily.
     
  10. PI Design
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    PI Design Senior Member

    I'm not reinventing the wheel. Twintex is a commercial material, used in some French boats and in kayaks. It is pp with continuous strands of glass, so similar in weight and stiffness to grip, but no VOCs, recyclable and better impact resistant. And it doesn't absorb water like polyester resins do. So lots of plus points. Bad points are that it needs 200C or so, so relatively expensive tooling. And I understand that it degrades in UV over a number of years. So if I didn't want to paint (not viable for large production runs) can I wrap in plastic sheeting? Vinyl wraps are common for short term graphics for PR, but is there a longer term alternative?

    So please can this be kept on topic, without lectures trying to show how smart you are (and failing!) whilst missing the point of the question. Sorry to be rude, but it is exasperating!
     
  11. jonr
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    jonr Senior Member

    3M sells stick on films that block 99% of UV and last at least 10 years. Non-clear films should do much better.

    For the sake of discussion, consider rotomolded glass fiber reinforced thermoplastics (using long fiber pultruded pellets).
     
  12. PI Design
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    PI Design Senior Member

    Sounds great. Thanks for that. Do you know of any downsides?
     
  13. jonr
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    jonr Senior Member

    My guess would be application difficulty and abrasion resistance when compared to paint or UV inhibited plastic.
     
  14. groper
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    groper Senior Member

    http://www.polycraft.com.au/

    These guys have been building polyethlene boats in australia for 11years now. Not sure if they are using fibre reinforcement tho? They are rotomolded... and have a skin thickness of around 10mm. They last fine in the UV light. The main drawback on these boats is they are quite heavy and thus heavy on fuel.
     

  15. jonr
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    jonr Senior Member

    My guess is the rotomolded PE (without fiber) is about 20% heavier than fiberglass + thermoset. But very rugged and lower cost.
     
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