| Author |
 Topic  |
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swoodard23
204 Posts |
 Posted - December 23 2002 : 2:24:14 PM
Well, I've just ruined my 1/4 scale plug of a car I would like to build. With a cardboard eggcrate template using styrofoam as filler, I had the form looking pretty good. Then I put plaster of paris on it and really messed up. The stuff is lumpy, dries slowly, hard to sand when dry, harder to sand when wet, and overall sucks. Does anyone know of a website that suggests a better method. It would be great if there was something I could spray on. Or if someone know how to make styrofoam acceptable to take a female mold off of directly using fiberglass. If someone has experience and would like to help I will definitely listen. Thanks meat for the corvette sites.
Thanks,
Scott |
andrew
53 Posts |
Posted - December 24 2002 : 12:29:53 PM
I'm not sure why one would use plaster in this application, unless you are just going by what is available at the local art supply shop?When I do plugs, it's polyurethane foam. You can't hotwire it, but it sands easy enough, it doesn't really matter. Just makes a big mess. Once you have your plug done, glass over a single laminate. For larger projects, like many car parts, I'd use 4 oz. But on something as small and intricate as a model, 2 oz fabric should do just fine. Once cured, then you body-fill, sand, and repeat until the shape is perfect. Finish up with a good sealant or primer. Normally I use Duratec (just about everyone does). But again, for something really small, breaking out the spraygun may be overkill. An aerosol type auto primer should do. You may have to do more finishing, is all..which will be the final step either anyways. Get it up to a glassy finish and you'll be ready to splash your mold. My question, if your still developing a prototype, why are you going molded? You may want to consider moldless construction. It's used all the time in prototyping and even moreso in amateur boat and aircraft construction. Not only is it more efficient and practical, the cash outlay will be significantly less. Andrew 
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meat
USA
992 Posts |
Posted - December 24 2002 : 1:40:13 PM
Andrew sounds right. I've made male molds from styrofoam covered in body filler and it's worked out okay. Fiberglass will distort, eat, and pretty much destroy styrofoam. It's not a pretty picture. And it sticks to your garage floor forever....not that I've ever done that... When I was much younger, I built a TriMagnum from an article in Popular Mechanics. I could have sent off for the plans, but I was young, impressionable, and only had enough money for the foam and fiberglass.  www.rqriley.com/imagespln/tmc3.jpg" border=0>
Here's how to do a one-off using GRP/urethane foam composite (it's the same article I used to build the car): http://www.rqriley.com/frp-foam.html Doing a one-off is pretty easy. And, when you're finished, THEN you can make up the mold! Your pal,
Meat.
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andrew
53 Posts |
Posted - December 24 2002 : 4:20:15 PM
The fiberglass, or more correctly the resin, must match the foam. If you are using a polyester resin, then it hould be safe on polyurethane foam. The wrong resin will act as a solvent, however...Andrew
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automotiveconcepts2002
USA
288 Posts |
Posted - December 27 2002 : 5:57:33 PM
When we did are 1/6 scale of the Mclaren f1 model we
used clay it works alot better then body filler
and glass.hope that helps but with the clay you work
alot harder on detail with rakes and hooks to carve
out you design.
robert
of Automotiveconcepts2002
www.lamborghinireplicas.com
robert
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hlcole
67 Posts |
Posted - December 30 2002 : 1:47:02 PM
Can you give some info on moldless construction? I am interested in this but don't know where to start.Thanks,
HLC
quote:
I'm not sure why one would use plaster in this application, unless you are just going by what is available at the local art supply shop?When I do plugs, it's polyurethane foam. You can't hotwire it, but it sands easy enough, it doesn't really matter. Just makes a big mess. Once you have your plug done, glass over a single laminate. For larger projects, like many car parts, I'd use 4 oz. But on something as small and intricate as a model, 2 oz fabric should do just fine. Once cured, then you body-fill, sand, and repeat until the shape is perfect. Finish up with a good sealant or primer. Normally I use Duratec (just about everyone does). But again, for something really small, breaking out the spraygun may be overkill. An aerosol type auto primer should do. You may have to do more finishing, is all..which will be the final step either anyways. Get it up to a glassy finish and you'll be ready to splash your mold. My question, if your still developing a prototype, why are you going molded? You may want to consider moldless construction. It's used all the time in prototyping and even moreso in amateur boat and aircraft construction. Not only is it more efficient and practical, the cash outlay will be significantly less. Andrew
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meat
USA
992 Posts |
Posted - December 30 2002 : 4:25:48 PM
quote:
Can you give some info on moldless construction? I am interested in this but don't know where to start.
Start here: http://www.rqriley.com/frp-foam.html Your pal,
Meat.
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andrew
53 Posts |
Posted - December 30 2002 : 4:49:22 PM
Here's a real good summary. Do a search on Moldless Composite Construction, or just Moldless Composite and you'll get plenty of hits. This is used especially in home aircraft building, and that is pretty good testament to its strength.One thing that is not really mentioned, you can use a solvent to dissolve the foam form underneath once the body is finished. www.fibreglast.com/bro25201056.php?session=69ff91897fad28d1cb945c4ac98119b1" target="_blank">http://www.fibreglast.com/bro25201056.php?session=69ff91897fad28d1cb945c4ac98119b1
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swoodard23
204 Posts |
Posted - December 31 2002 : 2:49:10 PM
I have been looking all over to find some pricing on polyurethane foam and have had no luck. Does anyone have any websites where they have prices listed online. Even went to the homedepot website and searched under insulation.
Thanks for the tip on the moldless construction. It should be a ton cheaper and weigh less than half what I was planning. Meat, how did you trimagnum turn out. Did you follow the two layers of 6oz cloth inside and out recommendation and how was the strength of that combo?
Thanks,
Scott
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andrew
53 Posts |
Posted - December 31 2002 : 6:47:25 PM
The company I posted the link to sells it. It'sa two part mix. Click the "sandwich core materials" link or follow this link www.fibreglast.com/products.php?session=69ff91897fad28d1cb945c4ac98119b1&area=14" target="_blank">http://www.fibreglast.com/products.php?session=69ff91897fad28d1cb945c4ac98119b1&area=14
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hlcole
67 Posts |
Posted - December 31 2002 : 7:28:53 PM
Thanks everyone for the info on moldless construction. I am, however, still a bit confused. Please bear with me, I am totally new to composite construction and just trying to learn as much as I can.I read that article you posted meat. I am curious though, once that project is built, isn't that the plug for a mold? If you are prototyping and you use this method, you still need a mold for making more of the same product, right? If I am understanding this correctly, what would be the advantage of the moldless construction? Thanks for all the info and help,
HLC
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meat
USA
992 Posts |
Posted - December 31 2002 : 8:23:48 PM
quote:
I have been looking all over to find some pricing on polyurethane foam and have had no luck. Does anyone have any websites where they have prices listed online. Even went to the homedepot website and searched under insulation.
Thanks for the tip on the moldless construction. It should be a ton cheaper and weigh less than half what I was planning. Meat, how did you trimagnum turn out. Did you follow the two layers of 6oz cloth inside and out recommendation and how was the strength of that combo?
Do a search on "polyurethane foam sheet" and you'll find a TON of links with pricing. The Trimagnum, as a built-from-scratch car in which I knew nothing about what I was doing turned out much better than I expected. I learned alot. Things like resin doesn't come off of concrete. It was an early experiment, and when it was done I sold it. As far as I know, it's still floating around up in Northern California somewhere. I've seen pictures of it, and it's still in one piece! In retrospect, and with about 20 years more experience, I'd have to say that I could have done better. In fact, I've been thinking about the Trimagnum quite a bit. I may end up doing one. But first I have to finish my FFR, built a GT40, and there's a Cobra replica that fits on a Miata that I want to do. Oh, and then the F355 on an MR2...I don't know if I'll be able to get to it this year. Your pal,
Meat.
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(21 views)
plaster sucks!
