Mould/plug questions

Discussion in 'Boatbuilding' started by Ocboatdude, Mar 13, 2016.

  1. Ocboatdude
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    Ocboatdude Junior Member

    Hello, I know this is my first post but I did do some researching through past topics but I still have a couple questions. I guess I don't know the difference between a mould and a plug... Here's what I want to do, I want to build a little kayak/canoe sort of thing for duck hunting. But I want to build more than one, and sell some per order. I know the shape I want and have a lot of confidence in the design. So I need something that allows me to glass the same shape over and over again, a mould/plug right? I have a lot of past skills with shaping and fiberglassing surfboards, so the actual glassing job is easy for me. It's the mould I'm confused about.

    Here's a very basic way I see the process of building this 10-12 foot boat mould.

    So the way I understand it is, and please tell me if I'm wrong, I need to build the shape I want, put heavy duty plastic over the shape, fiberglass over the plastic, build up the fiberglass to support the actual boat glassing, then when it hardens take the fiberglass piece off the plastic, flip it over, then put a gelcoat throughout the inside it, which I then put mould release all over that then start building boats?

    So I'm alittle confused as to how I go about making the mould/plug. I have considered having a company make one for me but haven't gotten that far yet. I do have a friend who can draw things on with 3D cad but I would much rather make my own mould.

    Any hidden information out there? I haven't found a website with step by step instructions on how to build a mould/plug

    Thanks guys, I appreciate any and all help. I'm in no rush to build these and want to build them the right way. I just know I need a mould/plug but don't know exactly how to make that thing!
     
  2. Ocboatdude
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    Ocboatdude Junior Member

    I found a really good set of videos on YouTube. Any help is still appreciated as I continue my research before making a mould.
     
  3. gonzo
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    gonzo Senior Member

    The plug looks like the finish product you want. It is identical in shape to the boat. Then, you use the plug to make molds from which to lay fiberglass and get the boats. The plug and the mold have inverse shapes.
     
  4. Ocboatdude
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    Ocboatdude Junior Member

    Gonzo thanks a lot for the reply
    Ok I understand what a plug vs mould is.... But I'm having trouble understanding how to build a plug..... So I need to build a plug, which is the exact shape and size of boat I want.... Then I fiberglass the plug, gelcoat it, add wax, then a bunch of layers of fiberglass to make a mould... Then separate the two, flip the mould, gelcoat the inside, add wax, and start production?

    Obviously I left out a ton of sanding and resin steps, but am I getting the picture or am I totally lost?
    Any website regarding how to build a plug and mould?

    Thanks again, I really appreciate the help.
     
  5. petereng
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    petereng Senior Member

    plug and mould building

    I think you need to find your local composite supplier and they will have the answers and materials you seek. I suggest you build a small <1m long object first to get a hang of the process. Cheers Peter s
     
  6. TANSL
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    TANSL Senior Member

    First, you should know the shapes of your boat. From there, one possible approach would be to build a structure similar to that of the figure, coating it with wood (plywood, melamine or wood strips) and above it, apply a few layers of fabric to form the female mold of the hull . That done, should reinforce the mold on the outside.
    Other experts in this forum can describe, perhaps, some other procedure or improve that I indicated.
     

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  7. Ocboatdude
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    Ocboatdude Junior Member

    Petereng good tips and I will definitely look around for a local shop. Also I like the idea of trying something small before going big. Most likely I'll build the who mould process but in a very small shape, like you said about 1m, then glass it a few times so I get the hang of spraying the tooling gelcoat, applying wax and pva, and if the glass comes out easily I know I'm doing it right.

    Tansl thank you for the reply. I know the shape I want and I have a friend with some kind of computer software we can draw it up and get exact measurements. That will help me build the structure of the boat correctly.
     
  8. SukiSolo
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    SukiSolo Senior Member

    Generally you can build the plug out of anything, as long as it stays stable enough. Melamine faced hardboard and chip are ideal release surfaces with just a coat of wax. One tip is on any solid timber/ureol/plaster/semi porous stuff is coat with epoxy and spray 2K black to show any minute flaws.

    The mould itself will need quite a bit of suitable reinforcing (for anti twist and sitting right way up) and make sure there are sufficient datums marked on it.
    Watch out on a large shape 'gripping' onto the plug when moulding especially if there is not much taper. To combat this it can be useful to use a thin lay up and 'pop' it prior to increasing the layup.
     
  9. Ocboatdude
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    Ocboatdude Junior Member

    Thank you sukisolo! I wasn't sure what I'm suppose to have over top of the plug to help release the Fiberglass mould..... Before posting my question I didn't really know what a plug vs mould was. I'm going to look into the melamine faced hardboard, and chip

    So I'm going to build the skeleton of my boat, then cover it with plywood, then melamine faced hardboard, or chip... This should look like an upside down boat hull right?

    Then I'll add fiberglass, a bunch of layers, pop off the fiberglass, then build a solid support system... So now I'll be looking at a boat hull as if it is right side up... Spray tooling gelcoat, make it all nice nice, then start glassing inside of that ?

    What are datums?

    And I think I'll do exactly what you said, I'll do a thin lay up, pop it off, then build up the reinforcement fiberglass

    Greatly appreciated guys, very happy to now start understanding the plug vs mould

    X2 thank you sukisolo for telling me a product to finish the plug which fiberglass will not stick to easily
     
  10. SamSam
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    SamSam Senior Member

    No. You get the plug surface as finely finished as you want the future boats to be, wax it up and put some PVA release on it. Then you put on the tooling gelcoat, then all the layers of fiberglass, then all the mold reinforcement to help it keep it's shape.

    When you pull the mold off the plug, the mold is complete. You'll probably have to buff the tooling gelcoat a little bit. Then you prepare the mold and laminate a boat, starting with the gelcoat that will be on the outside of the boat and working inwards. Gelcoat first, then fiberglass, then reinforcements. Put all the reinforcement (stringers, bulkheads etc) in it before you take it out of the mold or it might lose it's shape. When you pull the boat out of the mold, it will be all shiny and finished.

    Datums are marks you put in the mold surface, so when you pull a hull out, the marks will be on the boats hull. They show/mark where holes might have to be drilled for things, or lines where the fiberglass will have to be trimmed, etc.
     
  11. Ocboatdude
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    Ocboatdude Junior Member

    Awesome, now I understand the steps!! Thank you a lot!

    the thing I'll be making will be all fiberglass. I have to build a bottom plug then the mould, as well as a top plug (the deck) then the top mould.

    When I build my first hull and my first deck out of the two moulds, I will then need to connect the two. Should I fiberglass the deck to the hull, or is there some kind of piece that I can connect the two with? Keep in mind this is a small boat propelled by a kayak paddle

    I now understand the process! Thank you!
     
  12. SamSam
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    SamSam Senior Member

    You can make the two pieces fit together like a shoe box and it's lid, and then bond them together or caulk/screw them together with some rub rail covering the whole joint. You don't really want to free hand laminate on the outside as then it's a lot of work to get that looking good. Laminating on the inside can be a nuisance also with fumes awkward positions etc. Do an image search and see how others do it for ideas.
     
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  13. Ocboatdude
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    Ocboatdude Junior Member

    Great, thank you very much.

    Now to get the plug surface as finely finished as possible, I can place the melamine faced hardboard over the skeleton, and use bondo in any cracks and edges to smooth things out?

    Once that is done, proceed with the steps to create the mold?

    If that's incorrect, what materials do you recommend using for the surface of the plug?

    I'm almost understanding this 100%! Thank you a lot! I'm excited!
     
  14. TANSL
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    TANSL Senior Member

    If the plug surface is not developable, or if it is, but it has very tight curvatures, it is likely that melamine boards are not the most appropriate procedure.
     

  15. gonzo
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    gonzo Senior Member

    The mold not only fiberglass, but usually has metal pipes or wood as a structural support. Also, they often are part of the legs or other means of keeping the mold at a comfortable working height. Otherwise, you got the gist of it. Specially the part about a lot of sanding and filling and sanding again, etc.
     
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