painting a boat mould?

Discussion in 'Boat Design' started by whacker82, May 18, 2012.

  1. whacker82
    Joined: Sep 2011
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    whacker82 Senior Member

    hi again people i have a 10" clinker style boat mould, and im looking to repaint the inside as the colour of it at the moment is not working out for me. i was gonna paint it black, my question is how do i paint it and with what kind of paint? is it hard to achieve the glossy finish that you see in moulds? and how many coats would it need? thanks again
     
  2. CDK
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    CDK retired engineer

    Spray paint it with 2-pack polyurethane or any other paint that will not dissolve in the resin you're going to use. Two or 3 layers, flawless, then polish it, apply several coats of hard wax until it shines like well maintained Bentley.
     
  3. whacker82
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    whacker82 Senior Member

    thanks cdk, could i roller paint it on instead of spray, ive no sprayer
     
  4. messabout
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    messabout Senior Member

    The paint that CDK mentions does not work well with roller and only marginally well with a brush. Rent or borrow some spray equipment. Better yet have an experienced spray painter do the job for you. Someone who is a spray painter at an automotive body shop would be an ideal candidate. Such a shop will almost surely have odds and ends of paint that could be combined and sold cheaply for your job.
     
  5. whacker82
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    whacker82 Senior Member

    thanks for that, ill look into getting a spray painter to do it, plently of them around. thanks again
     
  6. SamSam
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    SamSam Senior Member

    It might work, but I would think it would be hard to clean up a mold enough to where paint would stick, especially when it comes time to start pulling boats from it.

    After a mold gets used a few times, it gets what they call 'cured'. The first few pulls are at risk for sticking, so multiple coats of wax are used. After the heat of a few boats curing, wax is driven into the pores of the mold a bit and much less wax is needed for subsequent pulls, sometimes multiple pulls can be made with no wax at all. If one of the newer silicone based release systems has ever been put on the mold, it might be a chemical impossibility to get paint to stick.

    Especially being a 'clinker' boat mold, getting all the ledges, nooks and crannies clean will be a chore.

    It might be possible with the correct stripper to get it good enough for painting, but you'll have to be real thorough in the preparation for painting.

    I'm guessing you want to make white boats and someone made the mold using white gelcoat, and it's hard to tell how your coverage is going. ?
     
  7. whacker82
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    whacker82 Senior Member

    well if im being honest sam sam, i only got the mould and for the first time pulled my first boat from it. whats after happening is when the boat was ready to be pulled from the mould i turned it upside down and hit it with a rubber hammer. the rubber hammer i used was fairly heavy. when i looking into the mould closely i could see tiny cracks in the inside of the mould. the light has to hit the mould to see these cracks mind and cant be felt to the touch. also when i look at the mould one side is more glossy then the other. im wondering would another layer of hard wax like cdk mentioned fix it up before putting on the mould release wax?
     
  8. Jeremy Harris
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    Jeremy Harris Senior Member

    Whacking a mould to get the part out is, as you've found, not a good idea.

    The problem you now have is that the gel cracks in the mould will propagate through the paint, pretty much no matter what you do. I had this self-same problem years ago on a GRP car body. After two paint jobs, both of which failed within a year with cracks coming through the paint, I had to grind back all the gel in the affected areas down into the glass, lay up a new layer of glass tissue, re-gel coat the areas and then painstakingly sand the surface back fair and re-paint. This worked OK, but was a heck of a lot of work.

    In your case I'd be inclined to just wax the mould and use it as it is until you can't get any more decent pulls from it, then invest in a new mould, using either your original buck or the last decent hull you pulled as a new buck.

    If you make a new mould, then I'd advise using black tooling gel, as I find black is far and away the best mould colour for being able to see whether a laminate is thoroughly wetted out.
     
  9. whacker82
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    whacker82 Senior Member

    if i keep pulling boats from the mould will the gel coat crack on the boat itself like it did with yourself after a years? im very worried now as ive 2 orders in paid for
     
  10. whacker82
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    whacker82 Senior Member

    how can i get the boat to pull away from the mould its seems impossible without hitting it a few times.
    the mould colour is a messy green colour like someone just spattered the mould with brush a few times and waxed it over. i would definetly be getting my next mould in black, it seems so much easier seeing where the wax needs to be polished off and gel coating.
     
  11. SamSam
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    SamSam Senior Member

    No, the crack in the mold won't transfer and make the boat crack in the same place.

    You should be able to able to loosen the sides up and pull the boat directly form the mold. You can CAREFULLY use soft wood or plastic wedges to get it started. We used to (on a big unmovable mold) loosen up the side, stick the water hose in, turn it on and float the hull loose from the mold. Another common thing to do is drill a small hole in the bottom of the mold and jam an air nozzle in and bust the boat loose with compressed air. Be sure to cover the hole inside the mold with a piece of masking tape before laminating.

    Just wax it a few times extra over the cracks and it should be fine.

    The dullness of the one side is probably too much wax. On molds used a lot, it's not uncommon to get a mold wax stripper and strip all the old wax out and then rewax like a new mold - 5 or 6 wax coats and a layer of PVA for 4 or 5 boats until the mold gets 'broken in'. Once the mold is stripped, if the mold itself is dull, you can get some buffing compound and an electric drill buffing pad and buff it to restore it to window glass shiny. You can also do that to the boats after you pull them if they have dull spots.
     
  12. whacker82
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    whacker82 Senior Member

    phew thanks sam sam, though i was in trouble there, i heard of the air pressure to realise the boat from the mould but ive no compressor at the moment, the water hose is brilliant i love that one very easy to do and effective id say.
    when i popped it out of the mould it had a dull look to it. ive seen some boats been pulled from the mould before and the shine and glossy look that they achieve is amazing. i was wondering how come i never got that with my mould
     
  13. Jeremy Harris
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    Jeremy Harris Senior Member

    The golden rule with moulds is to wax and polish them far, far more than you think you need to. Use a good quality wax (my preference is Maguires) and buff the hell out of it after each coat.

    Despite the gel cracks, as already mentioned, the mould is probably still OK. The water and air tricks work well, and I've found that adding a tiny bit of soap to the water helps get it to work it's way between the mould and the part.
     
  14. whacker82
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    whacker82 Senior Member

    thanks jeremy harris, i was leaving it half an hour between waxes and only rubbing it off with a wipe, gave it 6 coats of wax. i was using TR 104 High Temp Wax for my boat ill see if i can get the maguires wax, for the next boat as ive the material ordered due in monday.
    it will be only a matter of time before i make a new mould from a new boat hull as the mould has some wear and tear but its still in good enough condition for producing moulds.
    but what would i have to do to make a new mould from a boat hull, is it as simple as put on the releasing wax over the gel coat of the new boat hull, and paint on 2 to 3 layers of black tooling gel, and cover with fiberglass. or is there a more extensive method of getting it done. sorry now for all the questions, these things have been niggeling me for a bit. thanks again in advance this advice has been very much appreciated
     

  15. SamSam
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    SamSam Senior Member

    You can also temporarily laminate something in the hull that you can get a hold of to help get it loose and lift it out, and then cut it off and grind smooth once your done with it. Like a paper toilet paper tube you can pass a rope through or a loop of rope or a handle or something.

    Mainly though, get it loose on the side somewhere, then work it loose around the mold, applying some upward pressure and it should come loose pretty easily.

    Edit;;
    If you look at the bottom of this page, there are related threads.You can go to the top and in the search box put 'molds' or whatever, especially in the 'fiberglass and composites' section and it will show threads, keep looking at the bottom of the page for more threads, etc. If you have questions, just ask.
     
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