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Old 11-02-2015, 03:23 PM
Bob Kuykendall's Avatar
Bob Kuykendall Bob Kuykendall is offline
Join Date: Sep 2006
Location: Vallecito, CA
Posts: 593

We call that "aesthetic carbon." We don't do much of it; we're mostly a structural carbon shop.

It is rather difficult to get a pinhole-free surface with epoxy unless you are using advanced techniques and materials. Epoxy beads up on a waxed surface, and it is hard to get all the beads to hold hands even with the best of technique.

Two tricks we have used to get reasonable aesthetic carbon parts:

* Paint the mold with polyester resin, let cure, and then do an epoxy layup on top of that. The polyester wets the waxed mold OK, and the epoxy wets the polyester OK.

* Make an epoxy/carbon part, cure, and demold. Clean and acetone the molded surface, varnish with polyester resin, and then spritz with acetone to smooth out the varnish.

In my experience, the black carbon fiber surface will probably have a limited aesthetic life when used where it will get direct sunlight. Unless you're using a high-temp process like pre-preg, the high temps and temperature cycling will cause the surface coat to go either yellow or chalky pretty quickly.

Thanks, Bob K.
Bob Kuykendall
Low-drag wingtips for RV-4 through RV-8
EAA Technical Counselor
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Old 11-03-2015, 08:17 AM
flion's Avatar
flion flion is offline
Join Date: Dec 2007
Location: Flagstaff, AZ
Posts: 2,708

So, if it's just looks you're after, try finishing the piece as normal and then sending it out to be hydro-dipped. The finished part will be shiny and you can choose from many different weave patterns. I finished my white NACA vents that way and people have thought they were carbon fiber even while handling them, until told the truth.
Patrick Kelley - Flagstaff, AZ
RV-6A N156PK - Flying too much to paint
RV-10 14MX(reserved) - Fuselage on gear
EAA Technical Counselor #5357
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Old 11-03-2015, 08:20 AM
starkw1 starkw1 is offline
Join Date: Feb 2005
Location: Plymouth, MN
Posts: 44

You might consider coating your carbon fiber parts with th

Shiny finish with UV protection.

Plymouth, MN
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Old 11-03-2015, 11:49 AM
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newtech newtech is offline
Join Date: Mar 2006
Location: Evansville, Indiana
Posts: 663

I have had good results with spraying two to three coats of clearcoat into a well waxed mold; letting it cure and then abrading with a maroon Scotch-brite. Dont use air pressure to blow out the mold as you will lift the clearcoat from the waxed mold. Rinse and let dry before doing the layup using your favorite method.

Personal opinion only: don't use PVA; just obsessively wax the mold with Johnson's pure carnuba paste floor wax. The same wax you used on the floor in Basic Training. You can also spray the mold with epoxy primer to pre-prime your parts. This really works best if you are vacuum bagging your parts and select your bleeder layer to leave the part slightly resin rich.
Steve Eberhart, W9JUQ
3EV - Evansville, IN
Where is Steve and the Sky Terrier?
RV-7A Slider, O-360 A1A, Catto 3 blade, 2 screen Garmin G3X Classic, GTN 650, Bionics APRS. FLYING since June 24, 2009
EAA Chapter 21
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Old 11-03-2015, 04:00 PM
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FresnoR FresnoR is offline
Join Date: Oct 2008
Location: Fresno, CA
Posts: 482

Although these are good shortcuts, the tried and true method will always be sanding, more sanding, and wet sanding; then re-coat and repeat the sanding process.

There are a ton of techniques using sanding blocks and other tools to get a flat surface, but its really tough to avoid the manual labor. Make sure you use a resin that is UV protective, and you can use an automotive clear spray on that final coat.
Rick from Seattle

The art to flying lies in learning how to throw yourself at the ground and miss.
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