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Thread: quick easy fiberglass question

  1. #1

    quick easy fiberglass question

    i want to take a mold off of my corvette wheel well. my corvette has a really nice newer paint job... i want to keep my paint job lol what is a good way to do this with out messing up the paint when i pry the mold back off the wheel well?

    figured it would be a simple question for a body guy I'm just not that experienced yet, working with fiberglass yes but not in making molds.

    i do have carnuba wax, pva, gel coat, resin all the stuff I'm just worried about pulling the stuff back off the car and messing up the paint.

    i was thinking ceran wrap or something like that but seems like i will make more work for myself.

    thanks

  2. #2
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    Go to an auto wreckers and get a good used wheel well and work with that. Will probably be cheaper than re-painting.


  3. #3
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    Quote Originally Posted by CARBUILDER View Post
    Go to an auto wreckers and get a good used wheel well and work with that. Will probably be cheaper than re-painting.
    Good suggestion and advise.

    What are you wanting to do with what you will end up with?

    There are ways to do what you ask, but all of them involve the risk of screwing up your paint.

    A garbage bag taped in place, or saran wrap like you mentioned, covering the entire area with masking tape, or you might be able to vinyl wrap the area, then glass on top of that. All of these methods are risky as far as not damaging your paint. Just depends on too many factors for there to be any "guarantees".

    Your best bet would be to do like CB suggested and get another guinea pig to play with.

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    Help me understand. You want to make a mold of a part that is not only cheap but readily available?

    ebay my friend.

  5. #5
    Senior Member murcie-me's Avatar
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    I have molded several parts off cars and have never ruined the finish. You want to coat it with wax first, then buff as you would regularly. Next is to use a good sprayable water based mold release, either PVA or others that are available in shaker cans. The trick here is to make sure it goes on wet, and do several coats allowing each one to dry before the next. Dont worry about runs, they will shrink to nothing when the release dries. Apply 2 coats of gelcoat with a brush, do not add extra catalyst to speed the cure. Now you're home free. Apply as many layers of matting as you need to make a nice rigid mold. Do not try to pry the mold off until its fully cured. When glassing its best to construct a tab of fiberglass along one edge that can be used to grip with a pliers to lift the edge of the fiberglass for removal. As you lift, run a steady stream of water between the fiberglass and body panel. The water will dilute the mold release and the mold will fall off with no stress to the paint.
    Without talent experience is worthless

  6. #6
    Quote Originally Posted by murcie-me View Post
    I have molded several parts off cars and have never ruined the finish. You want to coat it with wax first, then buff as you would regularly. Next is to use a good sprayable water based mold release, either PVA or others that are available in shaker cans. The trick here is to make sure it goes on wet, and do several coats allowing each one to dry before the next. Dont worry about runs, they will shrink to nothing when the release dries. Apply 2 coats of gelcoat with a brush, do not add extra catalyst to speed the cure. Now you're home free. Apply as many layers of matting as you need to make a nice rigid mold. Do not try to pry the mold off until its fully cured. When glassing its best to construct a tab of fiberglass along one edge that can be used to grip with a pliers to lift the edge of the fiberglass for removal. As you lift, run a steady stream of water between the fiberglass and body panel. The water will dilute the mold release and the mold will fall off with no stress to the paint.
    thank you for that ive seen it done on you tube but never explained.
    Corvette panels... Not so cheap. Making my own molds... Free

    what i am trying to do is make the front wheel flares the back. Front looks great but the back is kinda lame. C4 vette.

    Thanks

  7. #7
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    Quote Originally Posted by murcie-me View Post
    I have molded several parts off cars and have never ruined the finish. You want to coat it with wax first, then buff as you would regularly. Next is to use a good sprayable water based mold release, either PVA or others that are available in shaker cans. The trick here is to make sure it goes on wet, and do several coats allowing each one to dry before the next. Dont worry about runs, they will shrink to nothing when the release dries. Apply 2 coats of gelcoat with a brush, do not add extra catalyst to speed the cure. Now you're home free. Apply as many layers of matting as you need to make a nice rigid mold. Do not try to pry the mold off until its fully cured. When glassing its best to construct a tab of fiberglass along one edge that can be used to grip with a pliers to lift the edge of the fiberglass for removal. As you lift, run a steady stream of water between the fiberglass and body panel. The water will dilute the mold release and the mold will fall off with no stress to the paint.
    Cautionary Note: Apply as many layers of matting as you need to make a nice rigid mold??? Fiberglass while curing can generates huge amounts of heat causing panels to warp, paint to bubble, etc. So I would recommend applying only three layers of matting and use some form of supporting structure IMHO


  8. #8
    Quote Originally Posted by CARBUILDER View Post
    Cautionary Note: Apply as many layers of matting as you need to make a nice rigid mold??? Fiberglass while curing can generates huge amounts of heat causing panels to warp, paint to bubble, etc. So I would recommend applying only three layers of matting and use some form of supporting structure IMHO
    Yup, known and understood.

    Thank you

  9. #9
    Senior Member murcie-me's Avatar
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    Quote Originally Posted by CARBUILDER View Post
    Cautionary Note: Apply as many layers of matting as you need to make a nice rigid mold??? Fiberglass while curing can generates huge amounts of heat causing panels to warp, paint to bubble, etc. So I would recommend applying only three layers of matting and use some form of supporting structure IMHO
    The amount of heat generated by 3-5 layers of average matting saturated with resin and the correct amount of catalyst would not exceed 95F degrees. Cars sitting out in direct sunlight here in CA during the summer reach surface temperatures of over 160 degrees for duration's well over 6-8 hours with no damage to the paint. Most people ive seen who do fiberglass always put in way to much catalyst, resulting in a quick cure and alot of heat. The problem is the life and strength of the fiberglass is greatly reduced, resulting in a brittle part (or mold) that easily cracks and has minimal structural value.
    3 layers of matt is more than enough to create a rigid mold, but I guess that depends on what weight matting is being used, right? I said to apply as many layers that are needed to create a rigid mold because I have no idea what weight matting they are using. A rigid mold for a small part with alot of returns and angled surfaces might be rigid enough with one layer (the angles create added rigidity), while a large curved surface may need 8 layers and a frame to hold the shape.
    Either case, the key is to following the instructions on the resin can and not rushing the job. I pulled a front bumper mold off a showroom quality LP670 a year ago and didn't have any problems.
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    Last edited by murcie-me; 06-17-2014 at 05:54 PM.
    Without talent experience is worthless

  10. #10
    Quote Originally Posted by murcie-me View Post
    The amount of heat generated by 3-5 layers of average matting saturated with resin and the correct amount of catalyst would not exceed 95F degrees. Cars sitting out in direct sunlight here in CA during the summer reach surface temperatures of over 160 degrees for duration's well over 6-8 hours with no damage to the paint. Most people ive seen who do fiberglass always put in way to much catalyst, resulting in a quick cure and alot of heat. The problem is the life and strength of the fiberglass is greatly reduced, resulting in a brittle part (or mold) that easily cracks and has minimal structural value.
    3 layers of matt is more than enough to create a rigid mold, but I guess that depends on what weight matting is being used, right? I said to apply as many layers that are needed to create a rigid mold because I have no idea what weight matting they are using. A rigid mold for a small part with alot of returns and angled surfaces might be rigid enough with one layer (the angles create added rigidity), while a large curved surface may need 8 layers and a frame to hold the shape.
    Either case, the key is to following the instructions on the resin can and not rushing the job. I pulled a front bumper mold off a showroom quality LP670 a year ago and didn't have any problems.
    great info, thank you very much.

    Ill take all i can get. I actually just started on it. I cleaned the surface, waxed it and aplied quite a few layers of pva. Ill aply the gel coat tomorrow after work.

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