Polyurethane Foam

Discussion in 'Boat Design' started by Bart01, Sep 23, 2008.

  1. Bart01
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    Bart01 Junior Member

    Thanks a lot for the info Christopher, are you using polyethylen foam as mentionned by fanie or PU?

    Bart
     
  2. Bart01
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    Bart01 Junior Member


    lolol no unfortunately not lolol otherwize I would be in the middle of the ocean speaking to you via NASA wireless stuffs lolol

    I know also about polyethylene foam but I'm quite interested by the isulation & fire extinguishing properties of the PU. As you mentionned there are also disavantage like expansion with water and so on ... I think the thing is to inject it well. Actually friend of mine is working in a PU company. We both are boats lovers and we plan to build one. My friend started speaking with people at his work about using PU as flotation material ... so perhaps we could have some help from his company to inject the foam. The thing is I would like to be sure it works lol ...

    Bart
     
  3. Design_1
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    Design_1 Water Logged Hack

    Bart-
    One company I worked for used polyethylene foam in 1/4" thickness on the back of compartment lids for noise reduction. I have not used it as a flotation material, but the standars on it are within a reasonable range. Water Absorption (Lbs/Sq.Ft.) Max of 0.2. Bouyancy factor of 58 lbs./cu, ft. What are you planning on using it for? Keep in mind the boats that I design are 28' and under.

    Fanie-
    Thanks for the info on the SPX33.

    Regards,
    Christopher
     
  4. TeresaPay
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    TeresaPay Junior Member

    If you are going to have any fiberglass layup come in contact with it you will need a polyisocyanurate as styrene attacks others...
     
  5. Ike
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    Ike Senior Member

    It seems I am going to have to give you all a lesson in flotation. US Coast Guard requires monohul boats under 20 feet in length to float when swamped. Exceptions are canoes kayaks, inflatables, sailboats and multihulls. So if it's a monohull motorboat or row boat it has to have flotation. The Coast Guard does not require foam. You can use anything that achieves the performance standard, which is, for outboard boat over 2 hp, level flotation, for rowboats and 2 hp or less, modified level flotation, and for inboards basic flotation. You can look up all the details (because there are details) at my web site http://newboatbuilders.com/pages/flot.html

    Most boat manufacturers use foam to accomplish this. For the most part they use either polystyrene (styrofoam) or polyurethane. Polystyrene is used in boats where the foam will not come in contact with gas, oil solvents, bilge cleaners etc. Anything that will dissolve it. This is found mostly in small aluminum jon boats, or other boats where the foam is enclosed in a box or encased. For the most part it is pre made block or stick foam.

    Polyurethane foam is almost always two part, commonly called pour foam. It is usually applied with a spray foam gun that mixes the two chemicals in a preset ratio and blown into the compartment. It is usually 2 lb density non-structural foam but some builders use heavier structural foams (such as Boston Whaler) in 4 or 6lb weights.

    The US Coast Guard does require that foam used where it comes in contact with gasoline, oils, bilge cleaners, etc, be able to resist those without losing their integrity. That is what people selling foam mean when they say it meets USCG requirements. I has nothing to do with it's density, structural capability, etc. It simply means that the stuff in your bilges won't dissolve it.

    PU foam is not supposed to absorb water. Surprise surprise. It does. Back in the mid 80's I was the project officer on a research project to test foam for water absorption. This was done by the USCG R & D center. Over two years our foam samples absorbed less than 2 /10% of their weight in water. However, we were using carefully prepared block foam from the foam manufacturers, not 2 part blown foam.

    In 1995 when the EPA changed the rules on blowing agents we began seeing boats that we were testing for compliance with flotation, absorbing lots of water into the foam. All kinds of reasons have ben put forth to explain this, but it just didn't happen before the change. The USCG has given ABYC a Federal Grant to research why this is happening. That is still ongoing. No results yet. But one thing is certain, it varies from sample to sample and some don't do it at all. But the same foam in another sample will. For some reason the cells walls are very fragile and breaking which allows water to migrate into the foam.

    You can get PU foam in block form usually from people who supply contractors. It is used for insulation in buildings, and so is polystyrene foam. PU is more exspenvie than PS. But you can also buy it direct from foam manufacturers. But they usually sell in large quantities. I have always recommended to boat manufacturers that they use pre-made block foam because it does not absorb water like blown foam. But the foam manufacturers all claim that none of their foams absorb water if you follow their instructions to the letter. The jury is still out on that.

    As for insulation properties, I don't know the R rating for blown foam but I'm sure the makers do. It is used a lot for insulation on metal boats. The R rating for block foam is usually printed right on the foam or on the literature for the foam. Fire resistant? Not likely. There are fire resistant foams used on cruise ships and other passenger carrying vessels. But I am not very familiar with it. The CG guys who regulate commercial vessels would know.

    The rules are basically the same in Canada and Europe except they also have flotation for all those boats that the USCG doesn't require it. ABYC has standards for flotation on Canoes/kayaks, poontoon boats, multihulls, inflatables and so on.
     
  6. Fanie
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    Fanie Fanie

    Fuel spillage is almost a given in any boat using a motor. You have to mention that fuel super disolves Polystyrene.

    It is the impacts the foam are exposed to while in contact or wetted with water. If a boat hits a wave you can expect quite a bit of pressure in the hull, which makes the foam compress and it inhales a bit of water. When the pressure is released again water is trapped inside the cells of which some may now have broken or developed small cracks.

    I have seen a boat stripped that had glassed in wood and blocks of polistirene. The wood was used as structure, it was falling apart (rotten) and was soaked with water. The polistirene blocks probably weighed more than the boat. If you squished them water oozed out. The PU pour foam have the same illness.

    Off topic - we have the same law that under 2 or 5hp (not sure which) does not pass as a 'powerboat'.

    Personally I think it a bit stupid. A boat with such a small motor is more likely to get into trouble if it is not able to make way into the wind. I think it would have been much more sensible if ie. a power to weight ratio was considered.
     
  7. Ike
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    Ike Senior Member

    Sorry Fanie but it ain't necessarily so. We have put this stuff through repeated shock, slamming, vibration, freeze thaw cycles and so on. At this point I am only speculating but the problem seems to be in the actual chemical process. Sometime it works and sometimes it doesn't When it doesn't you get very thin fragile cell walls that break easily like thin glass.

    Having said that, we have tested old boats and some had perfectly good foam. Some soaked up water like a sponge. So over many many years the aging process can break down the foam, but it seems to be freeze thaw cycles that do the most damage rather than shock and vibration. But this thing is ongoing and we'll see what the lab comes up with. At this point your guess is as good as anyones.
     
  8. Design_1
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    Design_1 Water Logged Hack

    Ike-

    Thanks for the lesson, always willing to learn something new. But I had already stated the flotation subject earlier. I go to a wonderfully boring seminar every year with the NMMA to learn all the new and interesting requirements placed on us. The Coast Guard regs. fall short of the NMMA standards on this subject, so we follow NMMA certification requirements. Anyone who wants to know the NMMA regs can go to www.nmma.org and do the research.


    As for Canada, I agree. As for Europe (CE certification) it is much more of a pain in the anal regions. Due to the fact that it has boating catagories that designate boats needing floatation as a lesser vessel. Which also leads to a more strict swamping restrictions.
    Ex. An 18' boat that we swamped a few years ago, company name withheld, that passed NMMA standards fell short in floatation by 3 cu. ft. of floatation according to CE certification requirements. We spent the next month adding 2 Part foam to all boats that had been manufactured and placed in transit hold. A hard lesson learned.

    All of that being said, I believe there are a lot of regs. that allow for designer/engineer interpretation. And anytime you add in the human factor, you have misinterpretations, therefore you have mistakes. But then again that is why we all gather here. All I have to go off of is what I experience for myself.

    And that is my take on it. And as usual, that and 35 cents will get ya a cheap cup of coffee.

    Regards,
    Christopher
     
  9. Fanie
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    Fanie Fanie

    You get fire retarding PE foams as well, check @ the link I posted
     
  10. Bart01
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    Bart01 Junior Member

    We are planning to build a 18 feets motor boat. We are still drawing the plans but it's changing a lot over time lolol.
     
  11. Bart01
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    Bart01 Junior Member

    Thanks a lot Ike for the lesson (by the way thx all of you for helping me :p )

    So from what I understood you advise to use pre made blocks. I am just wondering if the boat manufacturers who use PU foams are using pre made ones ... they would need lot of molds (especially when they have a large range of boats available ..), is that the case?
    I guess in both case it is the boat builder who either spray or mold the foam ... ?

    As you seems being an expert in that field :D perhaps would you know what kind of foam formulation is appropriated for the use in boat ?

    For the R rating, I neither don't have the number ... it depends of the thinkness you use but at least I'm 100% sure it is higher than PS ones. For Fire rate, it will depend on the foam formulation, it exists today some foams (PIR instead of PU) that are containing fire retardants which allows the foam to have good resistance to fire.

    Thanks again for your income :)
     
  12. Design_1
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    Design_1 Water Logged Hack

    Bart01-

    If you are planing on becoming a boat manufacturer, your best bet is to obtain a set of regulations from the coast guard or NMMA. They will help with interpretation if you need it. If you are just building a boat for yourself, the information you receive here may or may not be sufficient.

    As for "premade blocks", the only premade blocks that we use are the stringer systems. We aquire them through a company called Compsys.They are preformed and pre-rapped in virgin glass based on our drawings. We pre-soak the subsrtucture of them(travera), install the and then wet and roll the remaining rapped glass.

    There are a multitude of methods for installing and fixturing foam. Anyone of these methods may work for someone else and not for you. The way that we install foam works for us, but that does not mean that is the only correct way to do it. Or anyone else as far as that goes. We just know that we have had success with it. The best method is the one that fits within your capabilities and the regulatory bodies that govern your region and craft size.

    Good luck with your 18' boat. Would love to see it sometime.

    Regards,
    Christopher
     
  13. Bart01
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    Bart01 Junior Member

    We are planning to make only one for ourselve lol enough to worry about with one lol.

    The thing is that I have the opportunity to make a "partnership" with a PU formulator company: They provide the PU & installation, we provide the test boat. The thing is they are not familiar with such application so will be kind of R&D project for them. That's why I would like to have as much info as I can ... With such project I prefer to look myself for info rathen than letting people do and then being in trouble after words ...

    I know from my friend that his company stopped selling PU formulation to company which spray it into building wall because as someone mentionned earlier they got claims ... For this reason I am wondering if Pre-made wouldn't be better.

    Sure I will post pics of the advancement ;) for the moment we are more in the study part of the work lololol
     
  14. Design_1
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    Design_1 Water Logged Hack

    Bart01-

    Here is a link that may answer many of your questions for you. It may also give you some more ideas that you may not have considered. Either way it is a good point of reference for Coast Guard regs. Most of the floatation and capacities are covered starting at page 46, but it is useful to read through it entirely.
    http://www.uscgboating.org/safety/boatbuilder/downloads/PART1.pdf

    Good luck with your build.

    Regards,
    Christopher
     

  15. Bart01
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    Bart01 Junior Member

    Thanks a lot Christopher I'm gonna have a deep look at it :)

    BArt
     
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