Chaparral2f Posted December 19, 2010 Share Posted December 19, 2010 . In a few weeks I think I should be ready to start building the front clip for the Z31. Right now,it seems my only option is to get a whole lot of plaster and build a bolt together mold that I can separate. I've heard people talk about making a "splash mold". If someone can explain to me how it's done I think it might save me a lot of work. ThankJoe Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted December 20, 2010 Share Posted December 20, 2010 Splash moulds are used to make a copy of something, pretty simple, wax and prep the original so it's smooth and as near frictionless as possible and grease with a release agent (shoe polish, wax, KY Jelly (yes really, it's water based, doesn't dissolve or bond with Epoxy, and is slippery!), grease). Spray on some epoxy and let go tacky, this will keep the fibers of the matting scratching through the release agent and causing the mould to stick to the orginal be very careful not to disturb the release agent. Then lay on fibreglass matting and wet with epoxy, repeat until you have as thick a layer as you wish. The thicker the mould the longer it will last and the more copies you can get out of it before is breaks or degrades. Once the splash mould has cured and set, prise it off the original part, depending on what the release agent was you may find it comes easier if you heat it first to soften and liquefy the release agent between the original part and the new mould. Once off, clean the inside of the mould well, support it properly so it doesn't flex and bow, distorting the part to be made, remove any imperfections on the inside, apply release agent and start building up your fibreglass part in it. Quote Link to comment Share on other sites More sharing options...
Chaparral2f Posted December 20, 2010 Author Share Posted December 20, 2010 Thanks, I hope I'll only have to make one part. I dout anybody else would want a one piece front end for a Z31. Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted December 8, 2011 Share Posted December 8, 2011 Did you ever make your part? I wrote a big ol essay and suddenly realized that this was freaking last year, what was I thinking? Anyway for what it's worth... A splash is any kind of negative of something. I believe it is so named because it's like splashing on some plaster real quick and dirty like. Plaster is almost exclusively used for splash molding because it's a terrible idea for forming from scratch. Plaster mold are often boxed in around a piece though because it's easier to mix it very thin and just pour it. Plaster would probably be the easiest and cheapest for a one-off, but it would be really really heavy and you still have to seal it properly if you don't want your part to stick. Simply waxing it won't do. To make a plaster splash it would be ideal for the plaster to be the same thickness (like one inch) all around to keep it from cracking as it shrinks while it dries. Mix it really thick and put it on like a putty that won't run, then support it with a wood frame or something roughly the profile of the part so it won't be too fragile (egg crate construction). Try to give any mold structure before it cures so that it doesn't warp. If you take it off and it changes shape you can't go back. That said, a fiberglass mold is still ideal. To make it durable and keep it from warping, the mold is generally made pretty thick, which racks up the cost. If it only has to last one time though, I've seen whole car shells (nascar bodies) replicated with one layer of fiberglass backed up by a bunch of cheap foam, not the spray stuff that expands ten times, the kind you mix and it gets the consistency almost of clay that you can press into shape like a hamburger patty. If that's too complicated then you'll just have to use a lot of glass, but you can at least use polyester resin instead of epoxy because it's so much cheaper. Just don't use a heat gun on polyester, it will lose it's shape. Quote Link to comment Share on other sites More sharing options...
blaze73 Posted December 8, 2011 Share Posted December 8, 2011 (edited) On the topic of foam...if you are planning on using foam to create a shape or for a core of some kind where it will be in direct contact with the resin be sure to check the compatibility of the foam and resin. Polyester resin will dissolve styrofoam and leave you with a gooey mess and a ruined part. Urethane foams are fine however. As for release agents, PVA is a liquid plastic that can be sprayed onto your part even with a common spray bottle and will form a film similar to plastic wrap between your mold and part. The nice part about it is that its not greasy and dissolves in water so you can release your part by spraying a hose along the edge of the mold until the PVA has dissolved. Edited December 8, 2011 by blaze73 Quote Link to comment Share on other sites More sharing options...
GOTHALOSISM Posted December 8, 2011 Share Posted December 8, 2011 Where would some one get this so called PVA spray agent? Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted December 9, 2011 Share Posted December 9, 2011 Yes PVA is good stuff. A little messy but releases extremely easily. You can get it from any composites type place, maybe even a boat store like west marine, aircraft spruce, or of course ebay. There are also easy aerosol and water based sprays out there if you don't want to use a cup gun. Most releases are still supposed to be used over wax. By the way, car wax isn't ideal even if it claims to be high carnuba, you need actual mold release wax. Definitely wouldn't recommend styrofoam for anything. It sucks to sand as a shape and isn't dimensionally stable. You'd have to put quite a bit of bondo etc. over it to form a smooth hard shell. I also wouldn't recommend trying to mix your own styrenes, it's cancer in a can. PU can be hot wired etc. no problem. Quote Link to comment Share on other sites More sharing options...
Chaparral2f Posted December 9, 2011 Author Share Posted December 9, 2011 Thanks to everybody for your answers. I still haven't started the glass front clip, but I'm getting closer. The front end has been fabbed and installed, but I still haven't started the body work. I found this, it illustrates the process pretty well http://www.grandsportcorvette.com/gs/gs002.htm This is how the front end is at the moment. Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted December 10, 2011 Share Posted December 10, 2011 That's one way to do it. It seems like a lot of work making all that internal steel braking though. If they're that good at glass, I wonder why they didn't just make a glass mold. You just have to wax the crap out of it and it won't damage the original at all. They recreated mark rolston's whole front end that way. Just be aware that the plaster they used was a special two part system. Regular gypsum surely will not be as good of a finish and most likely be pretty porous. In fact pretty much the only way to get all the bubbles out is to vibrate it, but the part is a little big for that. That's why you see a pink coat, they spray a thin incredibly fine plaster on first to get a nicer finish and back it up with the cheap stuff. Also the name of the system escapes me, I'm sure there are knockoffs but it was first trade named after the guy who came up with it. Quote Link to comment Share on other sites More sharing options...
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