How to Make a Boat Mold

Written by bryan hansel
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How to Make a Boat Mold
A boat mould allows quick construction of identical hulls. (Jupiterimages/Brand X Pictures/Getty Images)

Making a boat mould allows you to quickly reproduce exact copies of the same hull through composite construction. To build a mould you need a plug, which is an exact copy of the final hull. Any imperfections on the plug transfer to the mould and to the parts that come out of it. In short, you cover the plug with a mould release, and then fibreglass over the plug. When the fibreglass dries, you pry it off, and the inside of the fibreglass becomes the mould.

Skill level:

Things you need

  • Heavy-duty cleaner for machine polishing
  • Buffer
  • Sealer glaze
  • Cotton rag
  • Paste wax
  • Paint sprayer
  • PVA mould release
  • Gel coat
  • MEKP
  • 85.1gr. fibreglass cloth
  • Vinylester resin
  • 85.1gr fibreglass mat
  • Paintbrush
  • Plastic wedge
  • Hammer
  • Soap
  • Water

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  1. 1

    Polish the plug using a buffer and heavy-duty cleaner for machine polishing moulds. Allow the cleaner to dry.

  2. 2

    Create a surface for paste wax by buffing with a sealer glaze. Buff until the surface shines.

  3. 3

    Coat the plug with five coats of paste wax, and buff the surface with a cotton rag until it starts to shine. Wait for the wax to dry.

  4. 4

    Find a room with a constant 70-degree or above temperature Fahrenheit and spray two coats of PVA mould release on the plug.

  5. 5

    Mix enough gel coat to cover the plug to half a millimetre in thickness with MEKP. Follow the manufacturer's instructions. Wait for it to dry, and then add a second coat.

  6. 6

    Place a layer of 85.1gr. fibreglass over the entire plug. Mix up enough vinylester resin according to the manufacturer's instructions to cover the plug. Paint the fibreglass with resin until the resin saturates it completely. As it saturates the cloth, the cloth turns from white to clear. Wait overnight for the resin to cure.

  7. 7

    Add two layers of 85.1gr. fibreglass mat over the plug and saturate it with resin using the same process as you used for the fibreglass cloth.

  8. 8

    Set aside in a warm place for two weeks until the resin completely cures.

  9. 9

    Remove the fibreglass from the plug. You may need a plastic wedge and hammer to release it if it's stuck on.

  10. 10

    Wash the paste wax and PVA mould release out of the fibreglass mould using mild soap and water. Once washed, you can start using the mould.

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