RC10Talk - The Net's Largest Vintage R/C Community

Is the dental plaster much harder than hobby plaster? Can you pick it up locally or do you have to be in the field?

Before I hollowed it out, I would try drilling a couple tiny tiny holes through the center and around the edge. I don't know how strong the dental plaster is but I would worry about collapsing plaster of Paris.

We have 4 types of plaster for dental use, the softer is harder than hobby plaster, the harder (type IV synthetic plaster) is 15 times harder than usual plaster.

Perhaps "Henry Schein" has a retail website for US. Or ask a local denstist or prothesist.

I gotta get me some of that. Sounds like good stuff. Plaster of Paris is ok but it is soft. It scratches way too easy.

Can you tell us how you heated the plastic before molding? Even a picture would help a ton.

the mold is now hollow, I drill some holes in all corners. It works better, the plastic goes in the deep corners.



i have a very bad method to heat the plastic, I have to make some tests with a oven: that's why I use garbage plastic cans for now.

When I have the whole good method, I'll try with bigger parts...

Nice work. Looks like you have the heat right. I had a problem getting the lexan too hot and it would be sucked into the holes of the mold. OK for points like the rear wing holes and body mount holes. Bad for the windshield or drivers helmet.

What about the vacuum side of it.Is it just a case of the more suction the better.

Moggie XL wrote:What about the vacuum side of it.Is it just a case of the more suction the better.

You want something that will pull plenty of inches. That is the distance the vacuum will pull a column of water in a sealed pressure environment. 50 plus inches is a good starting point. Most big time formers will go with a holding tank and take a high pressure vacuum and build up the intake. High pressure vacuums are nice but usually don't have the volume to pull the heated material fast enough. They trade off speed for power. A combination of both or a high pressure vac connected to a holding tank will work. I use a 6hp shop vac with good results. It pulls about 55 inches.

Or you can piggy back 2 vacuums.

sorry if its a repost on here but i didn't see it. What kind of vacuum former is that?

ra took a simple black box and drilled holes in it. Works like a dream for parts probably wing size and under. I built mine big enough to do 1/8 scale bodies but have not had the time or place to set it back up. I got my ideas from a video where the guy was making full size storm trooper uniforms. Depending on the size, you can use it to form just about anything.

So is this holding tank the exact opposite to a compressor tank.A tank with all the air sucked out.Also please explain piggy backing vaccums.

Yes, it's the axact opposite of a compressor tank and I guess piggy backing vacuums just means connecting two vacuum cleaners to one hose/air duct

Tadracket wrote:ra took a simple black box and drilled holes in it. Works like a dream for parts probably wing size and under. I built mine big enough to do 1/8 scale bodies but have not had the time or place to set it back up. I got my ideas from a video where the guy was making full size storm trooper uniforms. Depending on the size, you can use it to form just about anything.

The simple black box is no good: I have to build a rigid box, the black one lost his shape when the vaccuum is on, it creates massive air leaks and alows the melted plastic to go under the mold....and get the mold captured in plastic.

ra272 wrote:

Tadracket wrote:ra took a simple black box and drilled holes in it. Works like a dream for parts probably wing size and under. I built mine big enough to do 1/8 scale bodies but have not had the time or place to set it back up. I got my ideas from a video where the guy was making full size storm trooper uniforms. Depending on the size, you can use it to form just about anything.

The simple black box is no good: I have to build a rigid box, the black one lost his shape when the vaccuum is on, it creates massive air leaks and alows the melted plastic to go under the mold....and get the mold captured in plastic.

I use 3/4 inch MDF board. It is stout and cheap, but don't get it too wet

Moggie XL wrote:....please explain piggy backing vaccums.

Most of the big shop vacs have a 2 1/2 hose that you can vacuum with or you can move it to the exhaust and use it as a blower. You connect the first vacuum intake up to the former box and the second vac intake connects to the exhaust of the first vac. You will not double your power but you will increase it quite a bit.

Thanks for explaining all that.I'll give it a go.