Testing laminate schedules

Discussion in 'Fiberglass and Composite Boat Building' started by Tungsten, Jul 2, 2013.

  1. Tungsten
    Joined: Nov 2011
    Posts: 468
    Likes: 10, Points: 18, Legacy Rep: 75
    Location: Canada

    Tungsten Senior Member

    After building a couple of small boats (wood&foam cores)I've collected most kinds of glass.I'm gearing up to build again this fall/winter and want to do some testing so I can get a better understanding of whats good and whats not.
    I think everyones done the "hammer test" I'd like to do some "flexing tests"
    The boat I plan on building (drift boat) would benefit if it were more flexable in the middle of the hull.
    I'm looking for ideas on how to test flexing back and forth.

  2. tunnels

    tunnels Previous Member

    Flex !!
    what about twist ??
    sometimes those two go together !!.
    What kind of testing are you hoping to do !!!
    how thicker glass lay up and what glass you intend using ??
    what are you really trying to achieve !!.
    are you anticipating a core of any sort ??
    if so how thick and what would it be made of ??
    what size of boat ? big ?small? long ?narrow? deep ?shallow ?
    going to use a internally frame work of any sort with stringers and barers ?will it have a deck of any sort ?? this is related to twist that's also related to flex !!!:confused::eek:
  3. tunnels

    tunnels Previous Member

    no reply !! no one home ?? or to many questions !!!

    the more information you give the more information you will get in return and if there is no answer then we all miss out !!:(
  4. Tungsten
    Joined: Nov 2011
    Posts: 468
    Likes: 10, Points: 18, Legacy Rep: 75
    Location: Canada

    Tungsten Senior Member

    When floating rocky rivers you run the risk of high centering your boat on a rock.Say 4" around so all the weight of the boat sits on that little area.Solution as far as I know would be to have a hull(floor) that would flex in to reduce the point load of the rock.

    So i';d like to test different thickness of core with varying amounts of glass.

    Say corecell foam 9mm with 3 layers of glass compaired to say 12 or 16 mm foam with one layer of glass. Which will give me the most amount of flex before the core fractures?
  5. TeddyDiver
    Joined: Dec 2007
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    Location: Finland/Norway

    TeddyDiver Gollywobbler

    Then you should study about Lindsay Lord's method..
  6. tunnels

    tunnels Previous Member

    If you into rock sitting then core of any sort is the last thing you should be considering 3 layers of glass with 6 mm of core is a better option than 9 mm core ! thick glass or thin , the thicker the core the stiffer the panel so less flex .
    So on any panel what glass do you anticipate to be the best at flexing ??
    woven roving ?
    double bias ?
    chopped strand matt?
    triaxle ?
    biaxle 0/90/ ?
    what about unidirectional glass ?
    of the selection of glasses and if you insist on a core where do you anticipate putting the good glass , inside or outside of the cored panel ??
    or the same lay up both sides ?
    what about good glass outside and the not so good inside ?
    have you considered Kevlar for such a project ?
    what are the advantages between using Kevlar or Glass ? or just Kevlar ?

    Bending ability and flexibility is one thing but puncture resistance is something quite different but the two sort of need to work in combination and work side by side so the placement of the different types of glass materials within a laminate stack is vital and how it could destruct or stay together in an extreme situation . !!
    Interesting the results you will discover and will be I very interesting excise , would really like to know what you discover along the way and I hope you will share some of your finding with everyone on Boat design !!

    Some small high speed boats only use a csm +woven roving outside with a 3/8 thick balsa core and csm on the inside but virtually no stiffening inside to hulls but if there is stiffening its quite small and doesn't load any part of the hull very much so the panels bend and flex !! . Took me a long time to accept and understand what was actually happening !
    This concept is similar to what you are trying to achieve !!

    If you do make panels of unequal lay ups each side of a core of any thickness test one side then turn the panel over and test from the other side ,you will get some really interesting results I promise;)
    This is to do with the orientation of glass and you will get quite different results !!!
    Good luck and good hunting for the answers !!
  7. tunnels

    tunnels Previous Member

    That sounds like one very interesting book . I had trouble finding it on the net !!:)

  8. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    In one of the professional boatbuilders, but I do not know which number exactly (WHO KNOWS THIS?) is an article about a relatively simple test rig that you can build easily to test laminate specimens.

    One of my customers built one of those rigs on a shoestring, and learnt a great deal on the products he is using.
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