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Old Sep 18, 2007, 10:51 AM
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Carbon fiber finish

I'm new to composites. I've made a few carbon fiber plates by laying up fabric and epoxy resin between two pieces of MDF wood and wax paper, basically making a sandwich and then clamping the heck out of it to substitute for a vacuum.

The plates come out pretty good but don't have the "glossy" cosmetic appearance that I've seen on other CF parts. I care more about utility than cosmetics, but it couldn't hurt to have it look good. What are my options? I've heard you can use clear coat in a can as a final finish, but that it may peel off over time. I've also heard you can layup with polyester resin instead of epoxy, but it won't be as strong.

Cosmetics aside, does my epoxy finish need UV protection? The parts will see MAXIMUM one hour of sunlight per week, probably.

Thanks!
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Old Sep 18, 2007, 11:31 AM
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flxzcat's Avatar
lake forest, CA
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Use Mylar or a similar glossy surfaced material instead of wax paper. Also, wax and buff the surface of the material facing the epoxy.

Paul
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Old Sep 18, 2007, 11:33 AM
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David Forbes's Avatar
United States, FL, Gainesville
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Remember that the finish on the part mirrors the mold, which in your case is wax paper. Try using waxed mylar or acetate about .013 thick, and watch your finish improve. Car wax is fine.
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Old Sep 18, 2007, 03:08 PM
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Thanks for the replies guys. Sounds like waxed maylar is the way to go. Where can I obtain this? The wax paper I was using was available at grocery stores... I've never bought a mylar sheet before so I'm not sure where to look.

Thanks again.
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Old Sep 18, 2007, 03:35 PM
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United States, CA, Davis
Joined Sep 2004
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Quote:
Originally Posted by The111
Thanks for the replies guys. Sounds like waxed maylar is the way to go. Where can I obtain this? The wax paper I was using was available at grocery stores... I've never bought a mylar sheet before so I'm not sure where to look.

Thanks again.
Online sources are Aerospace Composite Products and Composite Structures Technology (CST). My local hobby shop in Sacramento carries rolls of the .014" thick stuff from ACP which saved on shipping.
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Old Sep 18, 2007, 03:45 PM
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John O'Sullivan's Avatar
Nova Scotia Canada
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Acetate has a higher gloss than mylar and will not adhere to the part. It separates easily and gives a mirror finish.
john
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Old Sep 18, 2007, 05:00 PM
DLD
David Layne
Tracy, Ca
Joined Jun 2004
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If you are just making flat plates, use glass, waxed and polished. That should give you the finish you are looking for.

DLD
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Old Sep 18, 2007, 05:57 PM
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Los Gatos, CA
Joined May 2005
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Also: roll the heck out of your fabric - each layer - to make sure bubbles are popped or soaked up. I drop a paper towel over the wet CF and use a 3" paint roller lookin' thingy from ACP (link above)... really helps to beat the bubbles.
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Old Sep 18, 2007, 06:47 PM
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Portland Intl, Oregon, United States
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Another idea that works well is anti static bags used in the electronics industry.

I have used them as vacuum bags on small flat parts and also pressed them as you have done. They leave a really glossy finnish as well.

TIM
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Old Sep 19, 2007, 12:25 AM
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Christchurch, New Zealand
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Glass is best, You can wax it really hard though you don't need to and if any resin does stick you can scrape it off.
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Old Sep 19, 2007, 01:12 AM
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United States, AL, Madison
Joined May 2002
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Quote:
Originally Posted by The111
Sounds like waxed maylar is the way to go. Where can I obtain this?
You can buy .005" or maybe .010" thick acetate at your local crafts store. i.e. Micheal's or Hobby Lobby (craft store, not RC store).

http://www.michaels.com
http://www.hobbylobby.com

For example at hobby lobby.
http://www.craftsetc.com/store/item....cat=4&Search=Y

I've seen acetate at hobby lobby store. I can't find much on their website. A better source is if you have a local (non national chain) art/drafting supply store. They likely will have acetate by the foot.
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Old Sep 19, 2007, 06:49 AM
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I but mylar from the local drafting supply house. It works great and I can buy as much as I want and the cost is $1/sq. ft. You should be able to find one close by. You might ask a surveyor or architact if they have any old drawings on mylar they want to part with. Be sure to use the non-inked side or you'll have some graphics on your lay-up.
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Old Sep 19, 2007, 08:00 AM
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San Diego
Joined Mar 2005
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You definitely want to use a glass plate if your panels need to be flat and you are making cosmetic panels.

Like DLD said, wax and polish the glass first. Then pour epoxy onto the glass and spread it around to the size of panel your making, say, 6" by 6". Then use a blow torch or butane torch and lightly move it over the epoxy to pop all the bubbles. Lay your first layer of carbon down into this epoxy making sure that the weave is nice and straight. Come in with subsequent layers of carbon for your strength. Let cure, use a wood wedge or razor blade to pry the panel from the glass.

Sean
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Old Sep 19, 2007, 03:44 PM
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United States, CA, Lake Forest
Joined Feb 1999
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I've done many aesthetic carbon panels and have found the best way to get nice looking parts.

-As others have suggested, a piece of glass or a mirror is a must. Wax it well and tape off the area you want with masking tape.

-Spray a couple coats of clear paint on the glass surface First before any lay up is done. If this will see sunlight, the epoxy will turn yellow in a short amount of time from UV (without clear paint). The best is a two part urethane paint like PPG car paint but you can even use a Krylon clear if you want... Anything with a decent UV protection in it.

-When the paint is dry, lay up the panel in normal fashion and vacuum bag it down. When the part is cured, you will pop it off and see a very high depth gloss and shine like nothing else. Any minor porosity that didn't evacuate with the vacuum will have a sealed layer of clear paint covering it. Any small bubbles will be masked much better than if it is just a layer of epoxy on the surface causing pin holes.
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Old Oct 01, 2007, 10:36 PM
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Carlsbad, CA
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How wet should the layup be before the mylar goes on? Should the epoxy be damp or just enough to wet the weave or?

Thanks

Ray
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