Don't want to mess up a mold plug

Discussion in 'Fiberglass and Composite Boat Building' started by aaronhl, Oct 1, 2013.

  1. aaronhl
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    aaronhl Senior Member

    So I am almost done with my mold plug and I want to go through a step by step with the experts..

    Spray primer plug
    Wax a lot
    Apply tooling gel and let cure for a couple hours
    Apply many fiberglass layers to strengthen mold and let harden
    Pull plug and mold apart

    Seems simple enough but I want to know some tips or tricks for doing this. The part is long like 1 foot long by 5 inches high with some curves.

    Any links to some good threads?
     
  2. SamSam
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    SamSam Senior Member

    Any links to some good threads?

    At the bottom of the page 5 similar threads are listed, if you go to one of them 5 more will be listed. Try that.

    Most plug and mold info is in this 'fiberglass and composite boats' forum, go back to that page and then try 'search this forum'.
     
  3. aaronhl
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    aaronhl Senior Member

    I've been searching didn't find much. Too bad this site doesnt have a mold making tutorial sticky. So far I have been watching YouTube videos.

    Are my steps correct in post 1?
     
  4. aaronhl
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    aaronhl Senior Member

    Read a lot more looks like I have it covered just need some info on materials to use.

    Can I use regular Rustoleum primer to seal the Bondo surface plug? If I put multiple coats of wax with PVA inbetween.

    What wax should I use? Any carnuba wax without silicone?

    As far as fiberglass, should I use a few layers of 1oz then go up to thick biaxal? The plug is not too big.
     
  5. SamSam
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    SamSam Senior Member

    Rustoleum would probably work, with wax and pva.

    Carnuba wax is good. Johnson's paste wax used to be 100% carnuba, but not anymore. It m ight still work though.

    Do a test, spread out some bondo , sand it down, use some Rustroleum in a spray can, wax it up and see what happens.

    A small mold like you're doing, I would just use like 4 layers of mat.
     
  6. aaronhl
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    aaronhl Senior Member

    Thanks for the info. I should try a sample first that is a great idea. Now I just have to figure out if the fiberglass I have will work. It's just cloth not too thin and not too thick. The mold doesn't need to weigh 50 lbs it's just s small cowl for an RC boat
     
  7. SamSam
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    SamSam Senior Member

    You can experiment with fabrics like for clothes. That way you can have a paisley or plaid cowling. Different fabrics have different properties as far as stiffness or flexibility. I remember reading of some third world country, they were making roofing panels with polyester and burlap. Tee shirts work.
     
  8. aaronhl
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    aaronhl Senior Member

    No way- that is an idea!!! Interesting and hope I can get that far. All I need a good mold setup one step at a time haha
     
  9. aaronhl
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    aaronhl Senior Member

    OK here is the plug I have been making and taking about in the thread. Let me know what you guys think. I'm pretty sure it's going to be a hassle to get off because of the design...here it is with automotive primer that I will be wetsanding

    [​IMG]

    [​IMG]
     
  10. SukiSolo
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    SukiSolo Senior Member

    Where are the Split lines going to be?. I assume on the sharp edges. That shape is not coming out of a one piece mould, unless I am misreading the form.
    You will need to define the split lines first to give you the best chance of getting mould release. Generally I have used Carnauba based waxes and sometimes mist sprayed with PVA to get release especially with epoxies. You might also consider drilling a very small hole in the mould and blowing it with air or water to get release. You may need more than one hole to do it.
     
  11. aaronhl
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    aaronhl Senior Member

    When I pull the actual piece from the mold, it just has to be flat towards the front. The fiberglass that I place inside the mold will not have to have the 90 degree edge. I just build the plug like that so hopefully the mold will be easier to use? The part coming from the mold will be cut and very rounded towards the flat front. I guess I should have consulted here before I made the plug

    Towards the back there is a flat piece underneath the rounded side. That needs to stay as is. Now I'm not sure what to do. I really want it to be a one piece mold.
     
  12. SamSam
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    SamSam Senior Member

    You need some more pictures from the back end and the top. The other side wouldn't hurt also. It sure doesn't look like you can use a one piece mold.

    Do you know what 'mold draft' means?

    A two piece (or more) mold isn't that difficult to make.
     
  13. aaronhl
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    aaronhl Senior Member

    Thanks for the continued help...of course I don't know what mold draft means, but now I will google it. This is my first mold can you tell? hahaha

    I will take more pictures to post in a few hours
     
  14. SamSam
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    SamSam Senior Member

    Draft is a 2 or 3 degree angling out of surfaces so the part doesn't get locked in the mold and won't come out.

    Say you had a square box for a mold, with the top open. The four sides should be angled out 2-3 degrees otherwise the part can be very difficult to get out of the mold.

    From the pictures you posted, it looks like things would wrap around and would never come out of a mold, the piece would be trapped in the mold.
     

  15. aaronhl
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    aaronhl Senior Member

    OK Here are some other pictures. I've spent like 2 weeks covering the plug with bondo, each time I sand I find a spot to fill. Sanded a little bit more today

    What would you suggest to mold this? If I make a two piece mold can I lay the actual piece in it in one piece?

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
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