Discussion in 'Materials' started by werwer6969, Sep 6, 2006.

  1. werwer6969
    Joined: Jul 2006
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Brampton, Ontario Canada

    werwer6969 New Member

    I'm interested in building a boat out of rigid styrofoam and covering it in fiberglass. I was wondering if anyone can tell me if this would work or will the fiberglass eat away at the styrofoam, any help anyone can give me would be greatly appreciated.

  2. SamSam
    Joined: Feb 2005
    Posts: 3,900
    Likes: 198, Points: 63, Legacy Rep: 971
    Location: Coastal Georgia

    SamSam Senior Member

    Fiberglass won't bother it but polyester resin will melt it. Epoxy resin will work. Sam
  3. frosh
    Joined: Jan 2005
    Posts: 621
    Likes: 14, Points: 0, Legacy Rep: 44
    Location: AUSTRALIA

    frosh Senior Member

    Greg, there have been a number of threads in the past about the compatibility of resins and styrofoam. Ditto about the structural qualities of styrofoam and other core materials Ditto again about the water penetration issues of the various foam materials.
    Suggest you research them yourself, and you will answer your own question.
  4. Ike
    Joined: Apr 2006
    Posts: 2,542
    Likes: 377, Points: 83, Legacy Rep: 1669
    Location: Washington

    Ike Senior Member

    plus all that, and penetration by gasoline, other petroleum product, and alot of cleaners, will dissolve styrofoam. You would be better off using polyurethane foams, They are resistant to gas, oils and solvent, as well as resins.
  5. JR-Shine
    Joined: May 2004
    Posts: 341
    Likes: 4, Points: 18, Legacy Rep: 54
    Location: Vero Beach, FL

    JR-Shine SHINE

    Polyurethane foam makes for a very poor hull core also, mainly due to its peel and shear strength (or lack thereof). Low density PU can be used for insulation and flotation or as a “form” over which you laminate fiberglass. This is not the same a core it does too participate in the structure - it just takes up space. Higher density PU foam is OK for areas of high compression like a transom.

    PVC foam (Divinycell and the like) are what you need for a hull core, or Corecell. I know the DIAB site (maker of divinycell) has a page on how to build a boat by strip planking a jib with foam, then glassing

    Their site is

    Good Luck,

  6. werwer6969
    Joined: Jul 2006
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Brampton, Ontario Canada

    werwer6969 New Member

    Thanks to everyone for there input. I was interested in building a kayak or canoe out of styrofoam, then covering it with fiberglass. maybe I should just consider doing one out of door skin and covering it with fiberglass.

  7. rgranger
    Joined: Feb 2004
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Virginia

    rgranger Junior Member

    Styrofoam core


    All the things these guys said is basically true but I feel you were asking a different question than the one they answered for you.

    Look at this site.

    This is a commercial boat builder using styrofoam core.

    You can use closed cell styrofoam covered in epoxy based fiberglass with no problems. It is rigid and resists water penetration. If the foam is completely covered then there is not an issue with solvent degradation. The blue foam pictured in the above link is nice but DuPont makes a 3" pink version of the same stuff. Home Depot caries it in 3'x8' sheets. A kayak would make a nice project and two layers of epoxy glass and you would have a light an strong boat.

    One more thing. PU foam will handle polyester resins but it does not like epoxy. PU foam core is what surf boards are made out of. If you want to go PU look up some sites for surf board foam.

    Some people like polyester and others like epoxy.

    C-ya on the water.

  8. apex1

    apex1 Guest

    Sure you did notice that this thread died already three years ago!?

    And for a good reason: Styrofoam has nothing, absolutely nothing to do with boatbuilding! There is not a single application one could use that stuff.
    And what you call a "commercial builder" is just a backyard tinkerer.

  9. gonzo
    Joined: Aug 2002
    Posts: 15,522
    Likes: 1,054, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Styrofoam works well as insulation. We have also used it extensively on hard tops and decks as a core between thin plywood. We used epoxy as an adhesive. The close cell polyurethane is rated for ground contact.
  10. apex1

    apex1 Guest

    Poor choice Gonzo! I regret to say that, there is better stuff around at almost the same price.
  11. gonzo
    Joined: Aug 2002
    Posts: 15,522
    Likes: 1,054, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Name one better material at the same price. Also, please explain why it is a poor choice. Have you done any testing? Commercial boats have been working for years with decks and hardtops built like that. It seems like your opinion is not based in facts but preferences.
  12. apex1

    apex1 Guest

    Almost the same price I said! We are talking insulation and we are talking sqare meters not acres right? Then the close cell Cyclopentan expanded PU is the far superior choice. You are too professional that I must declare why!
    And of course it´s my opinion, based on technical properties not preferences. Professionals do´nt have preferences, they strictly use the best material available for the job, or they are not long amongst the professionals.
    But as a structural member (and that was the original question) even that PU foam is not the best choice, let alone the white crap.

  13. gonzo
    Joined: Aug 2002
    Posts: 15,522
    Likes: 1,054, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    It pink or blue not white. I am talking about the closed cell foam. In spite of your rather emotional posts, you are not naming any material at about the same cost as the close cell polyurethane that is better.
  14. Steve W
    Joined: Jul 2004
    Posts: 1,824
    Likes: 63, Points: 48, Legacy Rep: 608
    Location: Duluth, Minnesota

    Steve W Senior Member

    There are applications where styrofoam will do the job ok,an example where i have used it was on a 24ft ULDB which i designed and built in 1987,the hull used klegecell and vinylester,the decks were ply/klegcell/glass but as i was installing full foam floatation under the berth tops i made them of 1 inch pink foam with a layer of glass cloth /epoxy on each side,peppered them with 2inch holes and glued them down and poured 2 part bouyancy foam thru the holed and let it foam out the holes like cupcakes and then cut them off and put light glass over,a lot lighter top than plywood or any other foam for that matter and laughably cheaper,has worked great for 20 yrs.I have also used it as a core in a doghouse top glued with resorcinal which i think works better than epoxy for this application(for many other too)but i also included WRC 1x around the perimeter and as beams across so it was 4mm ply as the bottom skin,wrc perimeter and as beams on maybe 16in centers,styrofoam glued between and 4mm ply top skin dynel sheathed,worked well.
    Russ Bowler built the 18footer "Benson and Hedges" in my shop 30 something years ago out of polystyrene/epoxy with an aluminum space frame to take the huge rig and daggerboard loads. CSK built a small bridgedeck cat back in the 1960s appropriatly named Foamy which was raced in west coast races down to mexico. Malcolm Tennant regularly speced ply/foam/ply with polystyrene for bridgedecks.I personally wouldnt use it for hulls as it has very low peel and sheer strength, but as with everything it does have its uses.

  15. boat fan
    Joined: Sep 2008
    Posts: 717
    Likes: 17, Points: 18, Legacy Rep: 435
    Location: Australia

    boat fan Senior Member

    It would not really make much sense using it for a canoe. or kayak.

    Much easier to use single skin plywood and you can always add floatation with water tight compartments or foam.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.