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Thread: First time Fiberglass questions

  1. #1
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    First time Fiberglass questions

    Well this is my first time using fiberglass and building a sub box. I decided to build the box out of MDF instead of using a fiberglass mold. Didn't want to mess up my car by accident. Now that it is build out of MDF, I want to cover it in fiberglass to make it smooth and rounded so I can paint it.

    My question is:
    1. Is there anything I need to spray or do to the MDF to make the resin stick better to it?
    2. How much hardener per ounce of resin should I use? I don't want to go do high because it is about 90-100 degress F here and I am new to fiberglass.
    3. How many layers should I use to cover the box?


    Thanks
    Ill post some pics up when I am done.

  2. #2
    Maximum Bitrate tundra2000's Avatar
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    im new to the whole fiberglass scene myself, but heres what ive gathered through my studies:

    1) i know the resin likes to stick to fleece, so maybe that? thats what people use if they are just building a box from fiberglass at least.

    2) cant really help you there.. sounds like googling territory to me.

    3) ive read that when making a fiberglass enclosure, you put enough layers on it to where you can stand on it without it flexing. dont know how to measure that if youve already build a box from wood tho. -shouldnt need too many layers since the MDF is pretty strong stuff.


    >>on a side note, why dont you just get some sandpaper/electric sander and round off the edges and paint it? that would be MUCH MUCH easier and would probably look better in the end. if you wanna fill in any gaps (i.e. inbetween boards and what not) , i recommend epoxy putty by Loctite (found at lowes). use that to fill in gaps and then you can sand it down. sorry im not an expert, just figured my answer is beetter than no answer

  3. #3
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    Thanks for your answers.

    As for your side note, I want to start getting into fiberglass. So I can make some more **** for my car and other side projects. This is basically a learning experience. Thanks though.

  4. #4
    Maximum Bitrate TimmyM's Avatar
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    It should stick fine to the MDF. The stuff I used said 14 drops per ounce. It was around 70 here and I used around 8-10 drops to give it a bit more working time.

  5. #5
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    Quote Originally Posted by TimmyM View Post
    It should stick fine to the MDF. The stuff I used said 14 drops per ounce. It was around 70 here and I used around 8-10 drops to give it a bit more working time.
    Allright. Thanks

    Anyone know about how many layers I should do?

  6. #6
    Constant Bitrate roflcopter's Avatar
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    if its purely cosmetic, and you want it all smooth and shiny, you should look into mixing body filler with the fiberglass resin 5:1 ratio. check out this... http://www.the12volt.com/installbay/...TID~74519~PN~1 it would give you a nice smooth surface to paint onto the box.

    now, if you are going to do more shaping to the box first, youll need to throw down a few layers first. test by pressing it with your thumb. its your judgement on how thick it needs to be if its just a cosmetic piece

  7. #7
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    Quote Originally Posted by roflcopter View Post
    if its purely cosmetic, and you want it all smooth and shiny, you should look into mixing body filler with the fiberglass resin 5:1 ratio. check out this... http://www.the12volt.com/installbay/...TID~74519~PN~1 it would give you a nice smooth surface to paint onto the box.

    now, if you are going to do more shaping to the box first, youll need to throw down a few layers first. test by pressing it with your thumb. its your judgement on how thick it needs to be if its just a cosmetic piece


    Thanks a lot. I might try the body filler. Not sure though.

  8. #8
    Wants to make it harder monkeyracer's Avatar
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    one question that may help:

    is the box in it's current state sealed completely?

    So, if you are just putting the fiberglass over the box to get a really smooth surface, but it's only cosmetic, you would be fine with one coat. If there are gaps (larger than 1/2") then the fiberglass needs to be between 4 and 7 layers depending on the weight of the mat. Post a pic of the box, so we can see what you've got so far. That will help us help you a lot better.
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  9. #9
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    Quote Originally Posted by monkeyracer View Post
    one question that may help:

    is the box in it's current state sealed completely?

    So, if you are just putting the fiberglass over the box to get a really smooth surface, but it's only cosmetic, you would be fine with one coat. If there are gaps (larger than 1/2") then the fiberglass needs to be between 4 and 7 layers depending on the weight of the mat. Post a pic of the box, so we can see what you've got so far. That will help us help you a lot better.
    I can't say it is sealed 100% because I cannot fit the silicon caulk under to get the top part of the box. Thats one of the reasons I am putting the fiberglass over as well as for cosmetic. The biggest gap is less than 1 mm. Which I think would be easily covered by the fiberglass in one of 2 coats (thats what I think).

    Here are some pics:






    Also, when I add more layers, do I need to keep putting more fiberglass cloth/mat over for each new layer?

    Thanks

  10. #10
    Constant Bitrate roflcopter's Avatar
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    you could seal the joints in the box with some fiberglass resin. just use a paintbrush and brush it into the joints through the sub hole.

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