Fiberglass replication

[LIL EVO]

I'm looking to replicate some body parts. If you have fiberglass experience can you please PM me regarding materials.

[Cryptic]

fiberglass, fiberglass cloth, resin, bondo, hardner... lots of fun good luck.

I've never made anything from scratch... Just fixed it and prepared for finishing.

[LIL EVO]

More specifically, 1.5oz chopped strand mat and polyester resin. Am I on the right track with that?

[Cryptic]

I think you have to start out my making a mold. Then you lay your fiberglass layers in.
Like a picture, you need a negative. I could be wrong though.

[LIL EVO]

Yes, I have the original pieces that I want to replicate. The fiberglass would be laid inside the part and pulled out. Then that fiberglass copy would be the mold.

[PonyKiller87]

About a year ago a guy on Thirdgen.org did a huge right up on this, he made a cowl hood for his car. It was a really good right up, and the process seemed pretty easy. He even got into adding clay to the stock panels to change the shape of your mold. Ill see if I can find it again.

[wikked]

http://www.thirdgen.org/techboard/fabrication/312045-custom-camaro-hood.html ?

[Karps TA]

Yes, I have the original pieces that I want to replicate. The fiberglass would be laid inside the part and pulled out. Then that fiberglass copy would be the mold.

If you lay it inside the part, your 'glass part is going to be smaller then the original. What you'd want to do is make a mold of the original, and then 'glass from that mold so that you keep the size the same.

[LIL EVO]

So if I lay glass over the original part and remove that to use as a mold, what happens to all the mounting points, clips, etc on the inside part?

[PonyKiller87]

you have to make tabs, and then lay them in when you do the fiberglass. I would use aluminum, keeps it light but will be plenty strong.

Might want to hit a Barnes & Noble, should be able to find a good How To book.
http://www.amazon.com/s/ref=nb_ss_b?url=search-alias%3Dstripbooks&field-keywords=fiberglass

[LIL EVO]

Ok that's where I was confused. So lay the glass on the outside to get a larger mold then lay glass inside the mold to make an "original", using aluminum, etc for any tabs.

[PonyKiller87]

Yeah make sure you use mold release on the panel, then you glass it, let it dry, pop it off. Then clean it up, put mold release on the mold you just made then make the new part. Heres where Ive read different things, one way was to put the gel coat stuff in the mold then glass it, the other way said to glass it, and gel coat it after you removed it from the mold. The tabs get put in after a few layers of glass are in the mold so they end up in the middle of the fiberglass and its a good idea to add a little extra around the tabs to keep them strong.

[BadAzzGTA89]

You will also want to make a frame for said mold out of some wood so it does not distort(sp)And you will need some gel coat to spray the mold with!
I use to do this about 10 years ago it was fun but remember the part will only be as good as the mold so take your time and get rid of all the air pockets with tools like thesehttp://www.nationaltbucketalliance.com/tech_info/Body/fiberglass/fiberglass_tools.jpg

[BadAzzGTA89]

Yeah make sure you use mold release on the panel, then you glass it, let it dry, pop it off. Then clean it up, put mold release on the mold you just made then make the new part. Heres where Ive read different things, one way was to put the gel coat stuff in the mold then glass it, the other way said to glass it, and gel coat it after you removed it from the mold. The tabs get put in after a few layers of glass are in the mold so they end up in the middle of the fiberglass and its a good idea to add a little extra around the tabs to keep them strong.

Gel coat then glass over it!

[BadAzzGTA89]

making a fiberglass mold



the plug
In order to have a form from which to develop your mold, you must either build the article from scratch using wood, plaster, polyester putty, Formica, sheet metal, etc. or you must have on hand a completed article which you wish to duplicate. The latter is of course the fastest method. The plug is generally a male model exactly like the item you wish to fabricate in every detail. If the plug does not have draft (taper) then you will have difficulty getting parts off. If the plug has reverse bends, like many canoes, then you will need to make a split mold which can be spread or taken apart.



If the plug contains soft materials on its surface such as plaster, wood, or putty, then it will have to be sealed with lacquer or resin to fill the pores. If plaster is used, it must be oven dried and then sealed.



To prevent your mold from sticking to the plug, the plug must be coated with plastic film known as “PVA.” This is a plastic dissolved in alcohol and has a green color. It can be brushed or sprayed on, but the best system is to spray on three thin coats, the first being a “mist coat.” The appearance will then be green. Each coat must dry half an hour or so and there must be no pools or drips to blemish your mold surface. For the easiest possible parting, before applying the PVA, apply a soft wax (Partall #2) formulated for use with PVA. After the third coat of PVA has dried, a coating of this wax can be gently applied over it for easy parting.



the mold

The first step is to apply a gelcoat which will be the mold surface. The gelcoat must be “exterior gelcoat” (wax free). If many parts are to be taken off the mold, it is desirable to use a “tooling gelcoat” which is designed to give longer life in mold use. The gelcoat should be in contrasting color to the surface of the part you will make. Since most parts are light colored, black gelcoat is

commonly used. This facilitates spraying up a uniform thickness of light colored gelcoat since the black will show through thin spots.



If the gelcoat is to be brushed on, two coats must be applied, and the first coat must cure several hours before the second coat is applied. The best means of gelcoat application is a simple gelcoat gun designed for the purpose and easy to clean. Air pressure of 80 to 90 pounds is desirable. Gelcoat must be applied at least 15 mils thick, or a quart to every 25 square feet of surface. If the plug was rough so that considerable sanding of the gelcoat will be necessary, then double the application. Before applying the gelcoat, it must of course, be catalyzed with MEK peroxide hardener, using from one to two percent.



When the gelcoat has cured so that it cannot be scratched off with the fingernail at the edge of the mold, which takes from 2 to 4 hours to overnight in cool or humid weather, you are ready for the “skin coat.” This is a layer of ¾ or 1oz. fiberglass mat, thin enough so you can see and remove all air bubbles entrapped by the resin when you “wet-out” the mat.The resin should be applied with a mohair roller or brush until no white fibers remain. Any air bubbles are then eliminated with a grooved plastic or metal laminating roller. The polyester resin used should be “lay-up resin,” which is wax-free. Be careful not to over-catalyze when laying up the glass. Above 75°F one 10-15 cc of hardener to the quart will generally suffice. Below 70°F, 20 cc per quart. Do not work below 65°F.



In laying up a fiberglass mold, warping can be avoided by allowing each layer to “kick” or gel before proceeding with the next layer. For a large mold, it is good to apply just one layer per day. After the “skin coat,” you can use 1½ oz. mat for a faster build-up. Generally, woven roving is not used in molds because the pattern transfers through the mold to the gelcoat. If it is necessary to use woven roving for strength in a large mold, it is applied after a thickness of 3 or 4 layers of mat has cured hard. The thickness required in a mold depends upon size and shape and the number of parts to be taken off. For a dinghy mold to be used only a few times, four layers of mat might be adequate.



removing mold from the plug
Allow mold to cure several days if possible so it will hold its shape. The first step is to trim the excess laminate back to the molded edge. This is easily done with a saber saw and a metal-cutting blade. The the edges are sanded carefully until the line between the mold and plug is exposed. Then a sharpened “tongue stick” is forced between mold and plug to separate the edges. The stick is then pulled clear around the plug until all edges are free and no bridges remain. Avoid using metal tools for this purpose as they will scratch the mold surface. Then the mold should pull free of the plug. If not, the parts can be flexed or pounded gently with a rubber mallet. If necessary, air or water can be forced under pressure between plug and mold. A hole can be drilled through the interface for this purpose. PVA is water soluble, which facilitates parting with water pressure.



polishing the mold
Depending upon the condition of the mold surface, it may have to be sanded with 220 grit working up to 600 grit wet or dry. The surface is then compounded with regular and fine finish compound formulated for fiberglass work. Best results can be achieved by using special compounds such as our “Heavy Duty Cleaner” followed by our “Sealer Glaze” to bring out a mirror finish.

Before using a mold, it should be allowed to cure a week or more if possible. Be sure to use PVA parting film and soft wax for the first 3 or 4 parts, after which a carnauba wax can be used.



gelcoat problems
Alligatoring, or wrinkling, can result from:



1. Gelcoat too thin in some spots

2. Insufficient hardener, or hardener not mixed will enough.

3. Gelcoat not cured long enough before mat lay-up.

4. Acetone cleaner drips out of roller or brush during mat lay-up.

[fly5150]

Find a boat builder to get the fiberglass from. They have it is 55 gallon drums and huge rolls of the mat. Much cheeper than at any store. I know there used to be a place in Port Washington that did large boat repairs.

[fly5150]

Oh yeah I also have the plastic measuring bottle for the hardner. works great, I'll get it this weekend when I get home if you need it.

[DRK]

you don't have to gel coat it, you can just shoot a high build primer on the scuffed raw glass after completion

[LIL EVO]

Can I put clear packing tape over the original parts before I lay fiberglass? People have said I may ruin the original part regardless of what I do.

[PonyKiller87]

Can I put clear packing tape over the original parts before I lay fiberglass? People have said I may ruin the original part regardless of what I do.

Thats what the "PVA" that Brian mentioned is for. Putting tape on would be a disaster. When the fiberglass resin cures it gets hot, it would melt the tape and most likely perminatly attach the mold to the part.

All the stuff Brian posted is right on, I seriouly recommend getting a book on this and then try it on a junkyard fender for practice if your not sure.

[LIL EVO]

FYI this is all on urethane(?) bumper/body parts

[PonyKiller87]

FYI this is all on urethane(?) bumper/body parts

Then you deffinatly need to make something to hold them the way they are on the car when you mold them or the mold will be all twisted up. I would make a wood frame to replicate the mounting points on the car, then screw the part onto that, and make a mold of it. Then use the same frame to make sure your mounting tabs are in the right place when you make the actual parts with the mold.

The heat from the resin will make the Urethane soft but it shouldn't be enough to melt them or anything. If there is paint on them it will probably bubble or peel though.