Can I use my grp boat as a mould?

Discussion in 'Materials' started by littletent, Nov 1, 2008.

  1. littletent
    Joined: Nov 2008
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    Location: belfast

    littletent New Member

    Hi - i have no boat building experience whatsoever! I am at the very beginig of researching what I might need to do. I have just bought a smooth walled old grp 12' boat and I was wondering if I could sand it down and use it as a mould to make a 'clone'? (of the exterior - please excuse my ignorance if this happens to be a ridiculous idea!) If it is possible, would the process be roughly like this: (so I know what to research!)

    1 clean and sand down my old boat.
    2 apply coats of wax
    3 apply release agent
    4 apply multiple layers of fibre/resin? (how many/what density?)
    5 apply gelcoat or top coat(?) (what is this finishing paper im reading about?)

    Im not looking anything other than a very rough job that will do as a first building project - I can maybe build something a bit more respectable after learning from this one!
    Thank you kindly for you knowledge and help.
    Littletent
    mjspam@live.co.uk
     
  2. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    1 clean and sand down my old boat remember sparkel
    1.5 new topcoat
    .
    2 apply coats of wax
    3 apply release agent
    3.5 gelcoat or topcoat (in the areas where's no internal lamination afterwards)
    4 apply multiple layers of fibre/resin? (atleast as much as the original g/sqm)
    4.5 sparkel & sanding multiple times

    5 apply gelcoat or top coat (what is this finishing paper im reading about?)it's to hide skipping the stage 4.5
    Just a quickie answer.. maybe I missed something
     
  3. lesburn1
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    lesburn1 Junior Member

    Just what is sparkel?

    Just what is sparkel? ;)
     
  4. NordicFolkboat
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    NordicFolkboat Junior Member

    My guess is some kind of bondo-like compound
     
  5. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    little tent,

    Using your existing boat you are using it as a plug, the mould is what you make off the plug, then you make another boat from the mould.
     
  6. lesburn1
    Joined: Oct 2007
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    lesburn1 Junior Member

    Boat as mold.

    I would repair and patch the boat.
    Sand to 800 grit.
    Compound until your arms fall off!
    Then apply Sealer/Glaze compound.
    Then 3 coats of wax, and 3 coats of pva.

    Since the surface you are putting the PVA on is the inside
    of the "new" boat you could roll it on, as it need not be perfect.

    Not knowing the size of the project, it would be un-wise
    to discuss how many layers of what kind of glass to use.
    Although you might think about a couple layers of 8oz. cloth
    then build thickness with mat then your outer layers of glass.

    Good Luck.
     
  7. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    Once you have the form gell coated and glassed, you're going to have to build a frame glassed into the mould to keep it rigit. Unless it is as little as your tent :D then it probably won't matter.

    Better get someone to show the ropes on working with fiberglass and gellcoat. Save you a couple of tries.
     
  8. TeddyDiver
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    TeddyDiver Gollywobbler

    :D Sometimes blander sammen idiomas mit toisiinsa...
     
  9. CDK
    Joined: Aug 2007
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    CDK retired engineer

    'Littletent' sees this as a first exercise in GRP boat building. The idea is not so bad and could provide him with a lot of experience for the next project.
    Where I live, people use the same process to build a GRP boat from an old wooden one. They don't bother with polishing and releasing agents, instead, they use hammer and chisel to remove the wood once they decide the project is finished.
     
  10. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    Covering the original boat with the brown packing tape works also well...
     

  11. carboncopy001
    Joined: Dec 2008
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    carboncopy001 Junior Member

    Yes you can use your grp for a mold, first fill and sand out any scratches or fractures, you can wet sand your part to 1200grit wet/dry. You can get away with a 320 then 600 grit wet/dry. Then polish with a coarse compound like aqua buff 2000 then wash down with methal hydrate, acetone or your preferance of compound removal washes. then polish again with miguires machine glaze or a aqua buff 1000. Then I would recommend finish bath of methal hydrate replacing rags each time you bath the part with cleaner(two rags one wash and one for drying, repeat 2-3 times. then apply a sealer, i prefer to use fre-cote or honey wax sealers. If you use products like fre-cote it is a liquid wax (4-5 coats of wax with a 1/2 hr gas off time between coats. Remember to use two rags always one for applying and one for drying. if you use a product like fre-coat you need to dry 30 seconds after application. the next is paste like honey wax, two rags also. But this time you have a wax rag that you apply the wax to the mold. Let wax haze then break with one rag and polish with the other. this i would repeat 10 times with gas off time as before. then spray with gelcoat, wait till gel time and peal it off, this will make sure that your wax job is done well spay this layer hot. then rewax as per specifications. spray tooling gel and begin your layup first layer just after your gelcoat has become hard enuf to apply pressure. first layer being a single layer of csm this is your skin layer this will help to prevent voids against the surface. After hardened sand and apply two layers, let set up and repeat process til you have a min of 8 layers. post cure and release after bracing.
     
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