Hull mold layup schedule questions

Discussion in 'Boat Design' started by MuddyWater, May 2, 2013.

  1. MuddyWater
    Joined: May 2013
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    MuddyWater Junior Member

    also to the stated addition of a tissue layer between the gel coat and lay up. that is already in my schedule. i have always referred to it as veil.
  2. waikikin
    Joined: Jan 2006
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    Location: Australia

    waikikin Senior Member

    Thanks for the advice Tunnels, of course using coremat is not as resin hungry as solid glass, on the other hand it is really heavy when compared to other cores such as balsa & foam.
    The advantage is in it's easy application as it's so easy to tailor to fit & builds laminate thickness & therefore stiffness quickly.
    Problems occur when through lack of knowledge it is installed dry onto the layer of chop.... of this leads to reisin starvation in the layer. I suggest you look over this site & calc the quantities of resin that should exist with the thickness of coremat used, typically around 600 grams of resin per millimeter of coremat thickness, also add the resin required by the chop strand mat used in the coremat installation.
    Regards from Jeff
  3. tunnels

    tunnels Previous Member

    Have you been side tracked ??

    Now lets get this straight are you talking of making a mould to make a product from or making a product from a mould you already have ???
    sounds to me like you talking of the product (boat )!!!

    Getting right back to absolute beginning corematt appeared in the late 1970s and was meant to be used as a glass replacement in industrial applications and panel work to build thickness quickly !! but it didn't take long before the marine industry pounced on it and started to put it into hulls and decks !! as always no one ever did any testing, they just used it and then found out later its inherent problems as time went on !

    Have use heaps of core matt when making moulds and its a really good way to build thickness quickly !! but I've always used 5 mm and even to the point of using 2 layers with glass layers between !!
    If you want thickness on your mould core matt is defiantly a way to go because it save you resin !!

    If you read the spec sheet ( and you should before you start not after ) there is a wet out resin usage at x times kilograms per sqr mtr depending on the thickness you are using and that's what you need to use !!! easiest and best way to use I have found is to make it really wet like shiny all over then lay a 450 csm over the top and wet and gently roll that out !! The csm if its properly wet then the core matt under it is 100% wet out properly as well !
    One really bad habit people have is to press heavy on the steel roller when rolling over core matt !! Firmly yes but not heavy !!and if you put a 450 over the top the square edges will not get air bubbles round the cut edge any where !!:):p
  4. MuddyWater
    Joined: May 2013
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    MuddyWater Junior Member

    my original post was about the hull lay up itself. not the construction of the mold.
  5. tunnels

    tunnels Previous Member

    WOOW back brothers !!

    Then there's a lot of confusing information here !! you said you were making a mould when in fact you are wanting to make a Boat and not the boat mould !!
    A simple case of lost in translation !! I would suggest you start again and don't mention the word MOULD !! :eek::confused:

    So after 10 seconds of reconsider your lay up !!,definitely not ever use corematt in the bottom !! topsides yes bottom no !!! and all those 1708 for the topsides why so many one after the other ?? any csm between ?? lets back peddle a little !! what speed will this boat do?? what kind of seas you going in?? and framing for the inside ?? stringers etc etc !! all these things would determine what the best glasses would be suitable throughout the hulls construction !!
  6. MuddyWater
    Joined: May 2013
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    MuddyWater Junior Member

    Ok a little more about the boat.
    Gunnels-1.5' above deck
    Draft +/- 10"
    10 degree dead rise in the transom more in the bow at the up turn
    think of an old aquasport flat back similar to that.
    box fiberglass stringers foam filled these are moulded
    Speed +/- 45
    Outboard 150-250 four stroke
    Closed transom with a bracket or portabracket
    Tower with second station.

    Seas- 3 at most on crappy days. Down here in the gulf wave periods are around 5 sec.
    And so on...

    1708 has csm bound to the back side so i didnt think u need a layer of chop between. Also in the layup turning 1708 45 degrees to the previous give a very ridgid lamination.
  7. tunnels

    tunnels Previous Member

    That's where you should have started in the first place !!
    So glassed over foam stringers longitudinally ?
    size and shape ??
    How many stringers pre-side ?
    what about bulkheads etc ?
    any strakes ??
    how many and what size ??
    They create weakness in the bottom panels and make the bottom flex more !!
    Can you post pictures of what you got and where you at ?? this info could really help a lot to determine a more suitable hull layup !
    10 degrees dead-rise is pretty flat bottomed !! and yes it will increase as it goes forward but from where does the increase start ??
    The more info we all get the better and more helpful we can be for you !!
  8. MuddyWater
    Joined: May 2013
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    Location: Naples

    MuddyWater Junior Member

    hey all was offshore the past few days but now back on the dry land. i will get some cad drawings together of the boat for some further info. this will take a few days. thanks again for all the info and help.

  9. tunnels

    tunnels Previous Member

    I'm just sorry for the confusion in the beginning but all going well we will get there I am sure !!
    CAD drawing could be a great help that's for sure ! like all things the more info the better the answers you will get !!
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