What is Gelcoat made up of?

    Gelcoat is a polyester product that is cured by using a catalyst called MEKP. (Methyl Ethyl Ketone Peroxide)

    MEKP is a dangerous substance and should be treated as such when using, being very careful not to get any on your skin or in your eyes.

    How can I get the catalyst - MERK?

    We cannot ship MEKP so you will always need to buy it separately from your local marine store or fibreglass manufacturer.

    How much MERK do I need?

    The amount of Catalyst varies depending on the conditions you are using it in, but around 2%-3% will always work.

    It is best to use a small syringe or dropper to get the required catalyst rate.

    If you have mixed 100gm of gelcoat, then you are aiming for 2ml of catalyst.

    Generally, polyester doesn’t stick well to Epoxy, so if you are repairing an epoxy boat, then you should source a special epoxy compatible gelcoat.

    What are the Gelcoat colours?

    Gelcoats colours are not always a 100% perfect match.

    Colour will vary depending on the depth of the repair and the batch.

    470, 420, 29er & Starling are built from polyester resin.

    49er, VX One & Zephyr are built from Epoxy resin.

    For the epoxy boats we use a product made by Scot Bader.

    Grey is Crystic 253 RAL= 7035

    White is Crystic 253 PA   - White 337

    For Polyester boats

    470  White-  LS30    White PA 337

    470  Grey- Grey RAL 7035

    Blue = is supplier by Nuplex who have their own code which is not an international code

    Does Mackay Boats supply gelcoat?

    We supply a small tin (of each relevant colour) with each new boat.

    Order additional gelcoat from our store

    How do I do gelcoat repairs?

    Doing gelcoat repairs is an art that improves with experience.

    Making sure the surface is prepared well and keyed up is critical.

    Overfill and then sanding back is a slow and time-consuming process.

    What sandpaper should I use?

    The biggest mistake is to use sandpaper that is too coarse.

    You shouldn’t sand the original surface around the repair with any paper coarser than 600grit.

    Once you have it fair with 600g, you can work your way through the sandpaper grades until you finish with 1500grit before cutting and polishing.

    We would typically use 600g, then 800g or 1000g, then 1200g, then finally 1500g.

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    Mackay Boats Ltd

    • 24 Manga Rd, Silverdale
    • Auckland, New Zealand
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