r3tic

I was looking through the mold making process as outlined on www.slopeiron.com and it was mentioned there that he uses a mix of epoxy, carbosil and graphite powder for the first layer of the mold. this layer, I'm assuming to to give a more durable surface to the mold to allow more parts to be pulled from it. My question is, what is the ratio used to properly do this? I tried to e-mail him and it was denied from his server.


thanks

slopemeno

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You could try going over to RCGroups and PM'ing him. You'll haqve to register but its easy. Gotta love that Spitfire!

Randy Etken

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I use West System # 423 graphite power and # 420 aluminum power both 10% by volume, mixed with #1099 Epoxy surface coat from Fibre Glast. The graphite makes it stronger and slicker and aluminum makes it stronger. Do not use carbosil and Epoxy if you want to pull many parts. Use the tooling epoxy or surface coat and your mold will be much stronger. I have pulled over 50 parts from same mold using this process.
Just what works for me.

SCALECRAFT

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Randy what do you use for a mold release system?/

Thanks

steve

Randy Etken

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Steve I use 2coats of Dolphin wax and Pva mixed 50-50 with 91% alcohol that I spray on. This is for wing tip molds. The back of mold all most comes down to a knife edge. For fuse and tail molds i only use the Dolphin Wax.
Randy

TT2

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If you need alot of it, Resin Systems makes a very nice surface coat epoxy for about $75 a gallon. I like it better than the FiberGlast 1099 because it's a little bit thinner thus easier to pour, mix, and apply. Releases air a little better too. You can get it in black, gray, white.

I have used my home-brew cabosil / graphite / epoxy but it seems that the results are quite brittle for some reason...maybe too much graphite? Who knows. Very difficult to get all of the clumps out of the cabosil as well...had to mix the heck out of it. Now I use the Resin Systems and no problemo.

-Tom

XJet

I use graphite/resin for the first layer of my molds and find that the graphite helps with the release. So far I've never had a layup stick and I'm just using conuba wax for release.

In fact, the only downside to graphite is that nothing seems to stick to it very well once it's fully cured. That means it would be hard to fix any chips or scratches on the mold surface. It also means that you have to lay up the next layer when making the mold *before* the graphite/resin layer fully cures so as to get a chemical bond, because a mechanical one won't be very good at all.

SCALECRAFT

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Thanks Randy

Steve