Steel hull isolation: alternatives to foam?

Discussion in 'Metal Boat Building' started by MarijoV, Apr 9, 2009.

  1. MarijoV
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    MarijoV Junior Member

    Hi everybody, does anybody have some opinion or better yet own experience of steel hull isolation using any alternatives to PU foam spraying or PU sheets? Has anyone ever used some of the common house-building materials (styrofoam sheets, glass wool, etc.) and got away with it?

    many thanks, Marijo
     
  2. Landlubber
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    Landlubber Senior Member

    Marijov, I have used both the foams only, spray and stick on, never again will I use the foam, it causes more troubles than it is worth, and also fitting out nightmares where extra lines or wires are needed, it is almost impossible to get then through, and always something comes up that has been "forgotten", making removal of sections very difficult. The stick on works very well, covers nearly all places and allows removal for either inspection or alterations.
     
  3. MarijoV
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    MarijoV Junior Member

    Hi Landlubber, thanks a lot for your reply... I am also afraid of the damn thing sticking as hell, which is great now, but in 20 years or at the very first change in interior (wires, pipes,...)??

    I can't help thinking some of the usual house-building isolation materials could do. Imagine the yellow glass wool in rolls? If it would be covered with nylon sheeting under the ceiling, maybe it would be damp-free and all of teh condensation would drip to bilges?

    I don't know... I built only a house, never a boat, so maybe I'm just plain stupid :)
     
  4. MarijoV
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    MarijoV Junior Member

    C'mon guys... so many views, and no comments except Landlubber's? I hope the question is not so dumb no one wishes to comment :)
     
  5. Northman
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    Northman Junior Member

  6. MarijoV
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    MarijoV Junior Member

    Thanks Northman.... I actually found that thread and I'm sure going to check it out in details... BR, Marijo
     
  7. MarijoV
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    MarijoV Junior Member

    Hi Northman, I saw the discussion... lot's of good advices... What about styrofoam (expanded polystiren)? It's unbelievelve cheap, easy to work with, and it does not absorb moisture like rockwoll or glasswool! It's easy to imagine it could simply be glued to the hull, cut with carpet knife when needed and easily replaced... have some experience there?
     
  8. daiquiri
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    daiquiri Engineering and Design

    Whatever you decide to do, it is important that you avoid the formation of condensation between the insulation and the hull. So the idea of glueing it tightly against the hull is a good one, whatever insulator you decide to use.
    Now about the Styrofoam (PS). It has a close-cell structure and is therefore a good moisture insulator and also a very good thermal insulator.

    But it is also inflamable, burns very quickly and releases toxic fumes during combustion. It shouldn't be used at temperatures above 70 °C.
    At about 95 °C it will start glassifying and it's good insulating characteristics will start deteriorating.
    It also has very low chemical resistance to diesel and gas vapours. PU foams perform much better in that sense.

    So bear all those thing in mind when choosing which parts of hull are suitable for insulation with PS.
    Don't use it in zones with electrical wiring, those in contact with fuel vapours and in zones which could overheat for whatever reason and reach temperatures above 70 °C.

    You can find a safety data sheet for Styrofoam here:
    http://engineering.union.edu/~rapoffa/MER214/laboratories/lab7documents/Styrofoam MSDS.pdf
     
  9. MarijoV
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    MarijoV Junior Member

    Daiquiri, thanks! Good advice on avoiding overheating zones... That stuff actually doesn't burn, but melts as long as there is fire close by... so, definitely some caution is needed, but I think it shouldn't be regarded as fuel for fire, or...?

    It's compatible with bitumen, so it could perhaps be bedded into a bitumen/tar based glue or similar...
     
  10. daiquiri
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    daiquiri Engineering and Design

    It will burn! It will start decomposing at about 250 °C, which is what you see when you put it close to the fire.
    But if it reaches a temperature of 450 °C it will start burning and feeding the fire, so it will actually become a fuel.

    An open-atmosphere combustion of PS will hardly reach a temperature of 450 °C. That's why you only see it "melting".

    But if a fire starts inside a closed structure, particularly if it's a metallic one (like your boat's hull), the temperature might (and I say "will") easily rise above 450 °C. Closed metallic structure acts like a reflector for heat radiation and therefore promotes a rapid temperature build-up to values way above 450 °C.

    That's why a small and apparently harmless fire on a vehicle in a road tunnel quickly becomes a catastrophe - the temperatures can easily reach values above 1000+ °C during the arson (up to 1200-1300 °C). A special branch of fire engineering exists (and a lots of related research has been done lately) for this type of structures, for a good reason.
     
  11. MarijoV
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    MarijoV Junior Member

    hmm... made me think! There is a local manufacturer here claiming "theirs will not burn", but I guess that's out in the open...huh!
     
  12. mydauphin
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    mydauphin Senior Member

    Poly foam Fire hazard

    In my humble opinion, after many years.

    Run all wiring on ceiling in duct, tubes, raceways etc... where removable roof panels give easy access.
    Run plumbing in bilge, water, air, hydraulic, with removable floor sections, covers etc...
    Insulation sides of hull with lots of spray in foam, can be done cheaply if you do first, There are many foams that will not catch on fire. Bond interior side panels to foam. No creaking....

    Oh, I don't take manufactures fire ratings with a grain of salt. I get my propane torch and see if it burns and what gases it puts out. Your life could depend on it. I was welding on steel boat one time, a someone had put some poly foam where no one knew. The fire that happen was hard to put out, could not get close because of poisionous fumes.... Never have any white poly foam on a boat, it burns like gasoline but even more noxious....
     
  13. daiquiri
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    daiquiri Engineering and Design

    Good point. Yes, it's better to precise that the story about the fire is valid for Styrofoam as much as it is for any other insulating material. At such high temperatures, like those developed in closed-ambient fires, nearly any insulating material is inadequate. Well, maybe the mineral wool - but it has other unwanted characteristics, like moisture-absorption.
    The fire needs to be prevented by adopting all the available measures, like the ones suggested by mydauphin. I would add a good switch pannel, a well done wiring and a correct engine-room ventilation.
     
  14. MarijoV
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    MarijoV Junior Member

    great! thanks a lot for the advice... both you and daquiri have the same thoughts, although you are a bit more hostile towards poly :).

    Good idea about running everything in roof... but how do you insulate the roof then? If you stick everything there in the foam, than I might as well do it in the middle of the hull...
     

  15. mydauphin
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    mydauphin Senior Member

    You put conduits, or raceways in roof. Only small part of roof is used.
    I then insulate around it with piece of non-flammable foam glue to ceiling. Remember ceiling should have structure and wiring and foam is within it.
    This is time consuming but only way to go. I tried spray foam on ceiling it was a disaster.

    Other point, living in South florida, we don't insulate for moisture control, cold waters, etc... We insulate for noise and radiant heat from sun. But it is very similar.

    On conduits and raceways, yes it cost more money. But it will save countless hours later when you find out you need to run just one more wire. Oh, and we run a lot more wires than we need for future use.
     
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