Coat New Boat Plug

Discussion in 'Fiberglass and Composite Boat Building' started by Nicholas Clark, Sep 1, 2013.

  1. Nicholas Clark
    Joined: Sep 2011
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    Location: glostershire england

    Nicholas Clark Junior Member

    Hi i have just built a small boat plug about 12 ft long. I have painted it in epoxy and have sanded it down. What would be the next step, do i need to coat it in anything else. Any advise ?
     
  2. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Yes. You are in for a lot of work from this point onward. I will assume that you will use the plug to make a female mould. Further assume that the plug has enough design draft (Tapered so as to be slightly larger at the sheer than at any lower part of the boat) to allow the female mould to be removed. This also applies if you intend to use the plug as a one off build without the female mould.

    Polish the plug to a fare the well. Make it a piano like finish or else prepare to curse a lot when you try to remove the moulded part. Repair any imperfections, even slight ones. Get some mould release wax. Wax the plug, polish, wax some more, polish, wax, polish. This may go on for days. You may want to use some poly vinyl alchohol (PVA) mould release on top of the wax. Be sure that no dust or contaminates are on the plug surface when you start the next layup.

    If you are making the female mould, then attach a generous amount of framing to the female part so that it is certain to hold its' shape. Let the mould, or boat if one off, cure for plenty of time, maybe days. Now the big event. ....Pray,..... try to remove the new part. If you have done all the work well and there is sufficient draft, then you can remove the new part even if it takes some time, muscle, and determination.
     
  3. Nicholas Clark
    Joined: Sep 2011
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    Location: glostershire england

    Nicholas Clark Junior Member

    Thanks

    Hi thanks for your reply. Yes its a female tapered plug that I have coated in epoxy but I cannot seem to get a good finnish on it. I have sanded the epoxy down but wonderd whats the best stuff to coat the plug in before I make the mould. Someone told me that duratec gives a great finnish and another told me just to wax it. What do you normally do. Thanks Nicholas Clark
     
  4. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    Duratec is nice, but as it is a polyester product, I would definately inquire about the adhesion on epoxy. It might be OK for a plug.

    Another option would be 2part PU paint (not acrylic paint, at least when you are planning on making a polyester based mould). In that case the normal procedures are applicable: block sand the plug until fair (grit 80 or 120), fix minor blemishes with epoxy putty, then sand with finer paper, and paint.

    After a week you can polish the plug, apply a wax according to instructions, then make the mould. (as per the instructions of the tooling system).

    I am not a big fan of PVA, as it causes rework in the mould. Instead I like to threat my plugs with a semi-permanent system at least the sealer part, followed by a hard wax. I use Ferrokote FS10 sealer, and Meguiars M87 wax, over a local produced 2C PU paint, and this Always works.

    Make tests, though...
     
  5. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    First let me be sure that we are talking about the same things. The plug is the male component. It is an exact duplicate of the boat you will build. It looks like the boat in every detail of the hull shape.

    The female part is the Mould. It is a cavity whose inside is exactly like the outside of the plug.

    If you are to make one boat there is probably no need for a mould. If you are to make several boats then the mould is the way to go. For a one off boat the plug does not need to be perfect except to the extent that the boat will be removable from the plug.

    The mould will contain every scratch, blemish, or other characteristic of the plug. That means that every hull that you pull out of the mould will have the same scratches,and blemishes. Obviously the plug needs to be near perfect.

    Having applied epoxy to the plug, you have made the careful fairing of the finish somewhat difficult. Epoxy does not sand easily. You might consider using an automotive primer over the plug surfaces. It will sand to a beautifully smooth finish without making a career of the sanding and polishing. Sand in stages of grit. First with something on the order of 400 grit wet or dry type sandpaper. Sand wet. Plain water with just a tiny dash of dish washing detergent makes the job go well though a bit messy. Continue sanding with 800 grit wet or dry, then finish with 1200 or 1500 grit. The surface will be as smooth as a babys bottom. Now the waxing begins.

    If there are indentures or deep scratches in the plug, you can use automotive body filler material which sands reasonably well. Do that prior to the primer stage of course.

    It is always a chore to remove the mould from the plug or to remove the boat hull from the mould. A common ploy is to install a length of small pipe at two or more locations in the mould. The end of the pipe is positioned to impinge on the inner surface of the mould and covered with a small bit of masking tape. When it is time to part the two items, apply air pressure to the pipes. That will usually set up a peeling action that helps break the part from the mould. There will be a small blemish in the finished hull where the pipe ends were. Choose an inconspicuous place such as along the keel line.
     
  6. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    And that is where a high gloss plug, no matter if you are making one or 1000 boats, comes in. Releasing the mould or the product does not need to be a chore, it can be a 5 minute job. With the release system mentioned, and the right surface prep, installing a couple of wedges is all it needs. Furthermore some lifting (sometimes by help of a crane, depending on the weight of your mould or product). Even 50ft boats seldomly took more than 30 minutes....

    With air injectors it even can be a 10 second job.
     
  7. Nicholas Clark
    Joined: Sep 2011
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    Location: glostershire england

    Nicholas Clark Junior Member

    Thanks thats great.
     
  8. Nicholas Clark
    Joined: Sep 2011
    Posts: 14
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    Location: glostershire england

    Nicholas Clark Junior Member

    Hi the plug is for a 12ft mould to produce many boats. I youse to work for a wooden boat builder many years ago and have recently worked for a company makeing resins and parts. And I thouht that I would give this small boat project ago. I yoused 6mm marine ply to build the boat without any problems. But as i told you i have made the mistake of putting a thick coat of epoxy on it. I thinks i have lost its true form and will start agian. Should i have yoused a cheaper alternative to marine plywood like mdf or something and then youse automotive primer on that and sand and wax ? THANK NICHOLAS.
     

  9. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    What is wrong with it now? Do you have pictures?

    Most can be corrected by a bit of elbow grease and some sandpaper.
     
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