How to make a mold?

[Austenp405]

To anyone that is seriously interested in fiberglass, I would highly recommend this book: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=2228&item=4506833049&rd=1 . A lot of it is related to commercial procedures, but it really helps to understand the entire process of what is going on, all the way down to the chemical level. It also has a lot of information on building molds, as the author talks about his short run of fiberglass bodied cars. I spent many nights reading in bed with a highlighter in hand.

[hanomon]

Yes I have picts, I can email them to you if you wish as my Zcar build link is under construction.

 

Yes, it is that yellow insulating foam you refered to and, I forgot to mension if after applied, it can't breathe, It won't dry completly. In other words, if the air dosen't hit it, and more is better (mobeta') it stays gooey.

 

PCM is the main component of the LT-1 computer system. it stands for (Powertrain-engine Control Module)

[Owen]

I'm still a little confused. THey made it seems like the mold is just one sided. I would've thought that you make one side of the mold lay in a bunch of glass then put the back mold of top of that. With hoods you need a way to attach to hood to the car. the easy wasy is pins but what if you want to use the original opening mechanisms? I also thought the molds themsleves were made of clay' date=' these are fiberglass. And the whole gel thing is confusing. Thanks for posting the site but are than any other that are informative yet understandable to a novice. (hands on I've never even worked with fiber glass, just done some reading to understand how to lay up fiberglass. The waxing is also confusing. Is he talking about car wax for shinyness and protection or some other kind of wax?

 

In the case of making custom body components would taking an autobody class be an excellent idea, or is that really only good for learning how to repair stuff?[/quote']

 

I like this book a lot.

http://www.amazon.com/exec/obidos/tg/detail/-/1859606245/002-4326797-8201651?v=glance

 

There's a lot of info here on HZ, but to answer your questions very briefly...

The one sided mold is used since you usually don't care what the inside of a body panel looks like, unless you're doing a hood or something. (My hood mold was still one-sided).

The two side mold you're thinking about is more for pour-in liquids or castings/injection molding etc. but they are a very widely used type of mold.

 

Hood hinges can be built in to the hood using angled pieces of aluminum.

 

I didn't look at the site but clay or fiberglass are used to make the plug-the male part of the mold. The fiberglass is pulled off the plug and is the female side, it is in this part that you lay fiberglass, carbon fiber, etc., and when it has cured, remove it. You should have a copy of the plug. If you did it right, it should be exactly the same size too.

 

The wax is a release agent, when the resin-impregnated mat/cloth is put into the mold, it will stick. Without the release agent, you'd have a hell of a time separating the two pieces. The release agent is used on the plug as well of course.

 

There's many ways to do this kinda stuff, it's not all just foam and wax. Speaker box makers use wool or t-shirt cloth stretched over an MDF ring to create the sloping sides (like a mountain or hill).

 

The gel coat is a protective layer of resin which will be on the topmost side of your part, check out your air dam, etc. you shouldn't see the strands of fiber etc.

 

I wouldn't recommend an autobody class unless it was strictly fiberglassing. Just get the books, know the basics and experiment with small pieces.

 

I thought this was gonna be brief...sheesh!

 

Hope this helps,

Owen

[Drftn280zxt]

thanks for the replies guys.

[Guest SS-Z31]

Alright, yes I know this post is kind of old but instead of making a new one maybe I can just add to this...

 

All of this info is great for replicating existing parts but what about one-off peices...?

 

I'm looking to make a mold for a one-of-a-kind front lip, flares, side skirts, rear lip and hood... Yeah, I know it'll cost an assload of money but not too many companies make anything for a Z31 and depending on how everything turns out I might be able to sell these to the Z31 crowd... Anyway, I've made a mold for some small interior stuff but I'd like to know how you guys went about making a form to create the mold for original parts? I've seen people using chicken wire and wood to make something to mold fender flares to but that does not really apply for a bumper lip and hood.

 

If anyone with some experience with this can chime in that would be great!

[ZROSSA]

I used foam that I glued to the car then filed and sanded roughly to shape. I then put coats of gib stopping compound ( the stuff you use to smooth sheet rock walls) And sanded it to the final finish. You then have to seal it and paint it. I had to use water based paint becuase the solvent based stuff would eat the foam I used. Just make sure you wax the hell out of it before you start laminating.

 

Douglas

[Here comes trouble]

You can use pre bent 90 degree (1 1/2 x 1) sheet metal flashing from Home Depot for a temporary flange for two part molds. The actual flanges will be of fiberglass construction. Pumber's putty in the string coils can be used for your clay needs to fill in the gaps on the preliminary sheet metal parting flange. Decide where your parting line is to be placed on the part to be copied. Cut an apropriate length of the flashing and lay it on the item you want copied. Use tin snips to cut slices in the sheet metal to conform to the surface of the piece to be copied. No need to remove sections of the sheet metal. # 8 by 1 1/4 self tapping screws with large phillips screw heads can be found at Home Depot to fasten the sheet metal to the work piece. With proper snipping the sheet metal flashing will comform to the work piece and the large head self tapping screws will pull the flashing very tight to the work surface. Any gaps can be filled with the plumbers putty to keep resin from seeping thru to the other side of the flange. Your parting line flange is in place and sealed with the plumber's clay putty. The screwed down part of the flange will always face away from where you start laying fiberglass. You lay the fiberglass up to and on the sheet metal. This will be your first parting line flange. When this entire side of the layed fiberglass is cured, trim the excess fiberglass that extended beyond the sheet metal flange to make a good clean edge with a cutting wheel grinder disc. Then remove the screws and sheet metal flange and discard the sheet metal, the screws can be used for another project. Fill in the screw holes on the work piece. Secure with clamps the cured layed up fiberglass first part to the work piece so no accidental movement takes place while laying up the second part to the work piece. Re-touch the other side with release "green wax" which you should have obtained from a fiberglass supplier. Rub the wax into the new fiberglass parting flange and lay the fiberglass to the unfinshed side to mate it to the work poece surface and the first parting line flange. Let cure and then grind off any excess fiberglass at the second parting line flange so both parting line pieces are even and straight to each other. These parting line flanges should be at least 1 1/2 to either secure together with clamps or bolts. With the two pieces secured to gether... you have a two piece mold. Any gaps in the mating surface of the two fiberglass flanges can be filled with plumber's putty which rubbed vigorously with finger to become very smooth. Thoroughly wax the new mold, spread on the gelcoat and then fiberglass . Shred the fiberglas mat to lay in tight spots and the shoulders of the first fiberglass flange that was created by the aid of the now discardedsheet metal flashing. Cure and crack! Do some research in this section and for Terry Oxendale (Blue Oval Z for previous threads.

[Guest SS-Z31]

Beautiful... I was also thinking about using foam but then I ran into the problem of it melting. Now I know that something needs to be coated over top of it... duh.

 

Here Comes Trouble - Thanks so much for that little write up. It was very helpful. I'm starting on the designs for the different parts now and your info will be invaluable when I start to lay up the part.

 

Keep the ideas flowing though... Never too much info to be learned

[Chewievette]

I used foam that I glued to the car then filed and sanded roughly to shape. I then put coats of gib stopping compound ( the stuff you use to smooth sheet rock walls) And sanded it to the final finish. You then have to seal it and paint it. I had to use water based paint becuase the solvent based stuff would eat the foam I used. Just make sure you wax the hell out of it before you start laminating.

 

Douglas

Depending on what your making, You can cover the foam part with a layer of packaging tape. I've only ever used this on small parts, but it works great. Gasoline also works well for dissolving the foam. Just be sure to protect yourself from the now toxic foam!

[Here comes trouble]

As for making original parts..... there were some some good hints on foam and plaster material that I found enlightening. I have used eheet metal roll sheathing to extend surfaces in making parts. Fiberglass does not adhere to the sheathing that is electrically galvanized. Also if you can find finished fiberglass parts that have been discarded by a manufacturer for a flaws. I bought a flat section of a fiberglass motor home roof panel that I cut up and utilized.