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Discussion Starter · #1 ·
Sounds like you have done some fiberglassing in the past. I have done a bunch of it but have never taken a mold off an existing finshed body part. I want to make a mold of my fiberglass hood on my Willys so I can make replacement if/when I wreck the existing one. Can I gel coat and laminate over the existing well cured (8 years) catalyzed urethane paint job and not ruin it when I pop the mold off?
 

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Absolutly, its rather simple. Before you layer the 'glass matt or weave (cloth)(prefferably weave) and resin all you would need to do is apply a seperating agent to the serface. A nice thick coat of carnuba wax would be fine. Just coat the hood with a few layers of wax untill the serface looks cloudy or waxy, then lay on your gel coat and layers of weave, after 3-4 layers use an old paint roller with a section of PVC pipe coverd in wax to roll over the layers firmly to squeaze out any air pockets, reapeat if nessasary depeding on if you use weave or matt (thickness). A female mold should be about 13/16"-1/8" thick after the compression for best results so it doesn't flex to much. Let it cure and it should pop right off with little effort.

A seperating agent could be anything from carnuba wax to candle wax to the correct 'glass seperating agent from a 'glass suplier. Its all works well, the wax with come off with a little wax remover paint prep or heat gun. The seperating agents very depending on type, but not very difficult. Pure clear candle wax is the cheapest way($2), you can melt it down let it cool a bit and pour it over, the warmer it is the thinner and smoother it will be. Candle wax can be found at most grocery stores or craft stores in 1lb bricks.

When making your hood from the mold make sure to compress it as well with either the paint roller (best) or a plastic spreader. When using a plastic spread make sure to only use one side of the spreader through the whole thing. If you switch sides mid river you will snag the fabric and have and awfull mess.

If you have anymore questions feel free to ask.

HK
 

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Discussion Starter · #3 ·
Thanx for the info. I have a full set of mat rollers and have carnauba mold release wax and PVA so am set up there. Main question is whether my current paint will survive unscathed after mold is popped off. I took the original hood mold off the sheet metal that I had welded together and finished. The fiberglass destroyed the surface of that plug but it had a very fresh coat of gloss black lacquer and I expected the damage. Didn't really care 'cause I didn't intend to use the steel hood when done. I do plan to keep using my current hood and would rather not mess up the paint if at all possible.
 

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I don't know about you guys but I have had much better luck with this <a href="http://www.sculpt.com/catalog_98/moldingaccessories/pd/polyesterparfilm.htm" target="_blank">type of product.</a> The catalysation of the polyester will eat right through your carnuba wax and probably adhere to the paint. At the other end of the spectrum is the teflon release agents that work just as well, <a href="http://www.freemansupply.com/RenRP792Fluorocarb.htm" target="_blank">here's one.</a> They are more expensive though.

I would do a test trial before subjecting that beautiful hood of yours to resin Willy, that would be an expensive lesson if it didn't work. Also I would "glass" in some plywood supports cut roughly to the shape of your hood to help retain it's shape once you attempt to pop it off. If you make the supports in two pieces and leave a gap in the middle (so you could use strapping to join them) you will be able to flex the form to ease removal. The other method I can think of is to use mylar film, you can guarantee no sticking that way and have a permanent mylar face on the mold. The mylar must fit perfectly though or you will end up with folds and seams in the buck. Use a heat gun (carefully!) to shrink and expand the film for fitting.

Good luck.
 

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Usually if the wax is topcoated with a gel coat before the resin is applied you'll have no problem. I've made carbon fiber hoods by molding a stock hood in this method 4 times and each time the worst that ever happened was that I got a bit of resin on the inner hood frame and it was a pill to get off.

4Jaw has a few good ideas also, mylar will work well, but it has to be perfect. I personally like candle wax because it cheap, easy and you can reuse it for your files after you scrape it off the hood. As long as the wax is a good coat (cloudy milky appearance) (3layers carnuba, 2 layers of melted candle wax) (let dry between each layer) nothing will harm your paint. The gel coat will act as another layer of protection over the wax because it is non porus and none of the resin will bleed through.

Also 4Jaw is right about the wooden frame to limit flexing, help during unmolding and it also acts as its own table when being filled to create your male peice. If you intend on mking both side of the hood use a gulf ball or marbel on each end between layers (top and bottom)to make sure the mold will line up correctly.

HK
 

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Discussion Starter · #6 ·
Yes I have all those tricks down. Main problem is whether the gel coat would mess up the paint. I think I'll give it a try since my paint is about as cured as you can possibly get! I'll put on about 6 coats of mold release wax plus a slick coat of PVA and should come out ok. Here are some shots of my first mold and the hood I made from it. I had to do so many fixes to the resulting hood that it will be easier to take a new mold from it than keep making flawed hoods from my old mold.

This is the original steel hood that I ran on the car for awhile but it kept cracking and flexing too much.


This it is the same hood w/ body work done and ready for gel coat.


This two shots of the final mold.


Another shot of the mold. I since sold the sheet metal.


This is the hood I made from the mold. I did a BUNCH of fixing body work flaws to get it in the shape it is now. Note the NASCAR type hood scoop I got rid of!
 

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Very nice work. I understand why your doing this again. A flawed mold has to go. No reason to make a flawed hood when you can take another mold and get what'cha want :D It shouldn't harm your paint one bit other than the hassle of removing the wax afterward. Have fun!

HK
 

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Nice work Willy, I continue to learn something new everyday. :D

Good luck and let us know how it works out. :)
 

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Willy if you do not mind me asking how long/much did it cost/take you to make the mold and new front end?

Where did you go for your supplies? (local or online?)

I am looking into makeing a mold for some body pieces on my car so any help/suggestions would be great.
 
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