fiberglass over plywood vs fiberglass foam sandwich

Discussion in 'Boat Design' started by nims11, Apr 7, 2015.

  1. nims11
    Joined: Apr 2015
    Posts: 8
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Fiji

    nims11 Junior Member

    I've started looking at boat designs from different links kindly provided by other forum members. I'm interested in a fiberglass build but am noticing that all the plans I've looked at are a plywood structural core with a fiberglass skin as apposed to a foam core with figerglass sandwich layers which is the type of boat I would actually like to build.

    I am also just discovering that here in Fiji the significant majority of boats, at least in the 16 to 40 foot fishing type range are called wood, but they are actually they same type of design I've been looking at which is marine grade plyboard with an outside layer of fiberglass.

    What would be the optimal design type/role of boat that would make use of a foam fiberglass composite? I understand this material will be more expensive, but lighter, less tensile strength but great compression strength. Stiff but easy to puncture. Again, what type of boat would this material be best suited for?
  2. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,386
    Likes: 1,045, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    I am getting worried about this aeroplane you intend to make from composites, because you clearly are not overly primed on the subject matter. In any event, there is no great call to be using glass over ply, usually the structure has enough strength without needing glass to increase it, but other types of sheathing materials that enhance abrasion resistance, and in conjunction with epoxy resin, seal the joins as well, are commonly employed.
  3. rwatson
    Joined: Aug 2007
    Posts: 6,170
    Likes: 498, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    The plywood boat is much easier to design, as much more of structural strength is obtained by the plywood before outside glassing.

    Foam has to rely on the outside laminates for a large component of the total forces, really it only provides compressive resistance to the equation.

    You assuming that foam is "easy to puncture" is a misconception. If the design has been done properly, they should be no easier to puncture than plywood.

    The biggest reason you should not be considering foam core is that real engineering expertise has to be applied to designing a foam composite hull, and is not something that an amateur should attempt on a boat this size.

  4. Pericles
    Joined: Sep 2006
    Posts: 2,015
    Likes: 141, Points: 63, Legacy Rep: 1307
    Location: Heights of High Wycombe, not far from River Thames

    Pericles Senior Member

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.