An All-Epoxy Finish

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Written by Joe Daly
Control Line Aerobatics
As seen in the July 2021 issue of Model Aviation.

IN THE EVER-CHALLENGING PURSUIT of a lightweight, high-quality finish, I decided to complete an airplane using an all-epoxy finish from bare wood. This is not a new concept. It was used in some form in the 1970s and 1980s with polyester resin and paint such as K&B SUPERPOXY. It is similar to the old concept but is better because you do not have the terrible smell of polyester resin. I’ll take you through the process from bare wood to a high-quality finish using only epoxy products.

For the base, I started by sanding the airplane and components with 320-grit sandpaper and wiping off the dust. The first coat is what I call a sealing coat to seal the wood. This important step will allow for a lightweight finish.

For the first coat, I used both West System 105 Epoxy Resin and Pacer Z-Poxy Finishing Resin from Zap. Both work the same. I prefer to use the Z-Poxy for this coat because it seems to sand better. I mix 1 ounce at a time. More than this is not workable. I brush it on, coating an area on the airplane (for example, the top of the wing).

Here is the important step. Warm the area using a heat gun and use a paper towel to wipe off all of the Z-Poxy until you are left with a dull, slightly tacky surface. Allow it to dry for 24 hours and you will have a sealed surface that will not allow the finish to soak in and add unnecessary weight. You are left with a dull, fuzzy surface when it’s dry.

Next, lightly sand the area with 320-grit sandpaper and knock down the fuzzy surface; however, do not sand off the Z-Poxy coating. I then applied a second coat of Z-Poxy. In this step, I poured it on and squeegeed it off, only trying to fill in the grain. Again, I applied a little heat to help it flow, and allowed it to dry for at least 24 hours.

the wing has a third coat of z poxy applied
The wing has a third coat of Z-Poxy applied and is ready to sand out flat. Remember not to sand through the Z-Poxy!

Lightly sand the area with 320-grit sandpaper to take down any high spots, being careful not to sand through the Z-Poxy. To finish the base, I applied a third coat of Z-Poxy using the same method as the second one. When it is dry, you have a shiny surface, which you will then sand flat with 320-grit sandpaper, again being careful not to sand through the Z-Poxy! This process added 3/4 of an ounce to the entire airplane.

For the paint, I decided to use a Klass Kote epoxy finishing system. Excellent customer service was provided by Klass Kote, and the quality of the company’s material is fantastic! After sanding the Z-Poxy base flat, I applied a few medium coats of Klass Kote epoxy primer until all of the grain had disappeared. I allowed it to dry for a few days then block-sanded the airplane with 320-grit sandpaper until it was flat, sanding off much of the primer.

I applied a second coat of primer, again following the same process, and was left with a flat, grained, filled base. The surface was a translucent gray in most areas. The primer added 2 ounces after I sanded it off.

Now for the color. White was applied first and took three coats to obtain coverage. Next was the red and blue trim and the black checkers. All of the colors added 2.5 ounces.

Moving to the main event, I used Klass Kote clear gloss epoxy. This stuff flowed out of the spray gun like water. In fact, the colors all flowed well out of the spray gun and left a nice, flat finish. I shot three coats of clear and a fourth coat on the trim areas to help with blending in the trim line. The clear coat added approximately 1.5 ounces to the finish.

After the clear coats dried, the finish had a nice shine to it, and it looked like a new car coming off of the lot.

Always looking to improve appearance points, I decided to sand it down with 1,500-grit sandpaper then 2,500-grit sandpaper until it was perfectly flat, and then I used Meguiar’s M205 Mirror Glaze Ultra Finishing Polish to buff it out. The shine really came out and the finish was nearly perfect! This also shaved off approximately 1/2 ounce of weight, making the total weight gain from bare wood to a clear finish 6-1/2 ounces. Not too bad for a 675-square-inch aircraft.

I was happy with the process and the quality of materials that were used. I will also be writing a step-by-step for the Precision Aerobatics Model Pilots Association’s (PAMPA) Stunt News newsletter!

the klass kote gray primer has been applied
The Klass Kote gray primer has been applied. The primer flows out nicely and sands well with 320-grit sandpaper.
the fourth coat of clear has been applied
The fourth coat of clear has been applied. The clear coat flows like water out of the spray gun and has a nice shine.

On the subject of PAMPA, there is renewed focus on bringing back Stunt News, which was a bimonthly, 100-page newsletter and very well done. Many members joined because of that benefit. Bob Hunt brought the idea forward to have an online newsletter on the PAMPA website and that has sparked an interest that is coming to fruition.

So far, quite a few district representatives have submitted district reports, and even a few how-tos are posted on the website! This is definitely going to give PAMPA new life and provide an excellent benefit to its members. If you are not a PAMPA member or haven’t renewed your membership, join this AMA Special Interest Group!

after sanding it with 1500 grit and 2500 grit sandpaper and polishing
After sanding it with 1,500-grit and 2,500-grit sandpaper and polishing it with Meguiar’s M205 Mirror Glaze Ultra Finishing Polish, the reflection on the rudder can be clearly seen in the stabilizer.
the finished product is awaiting to be flown
The finished product is awaiting to be flown! The finish gained 6-1/2 ounces from the bare wood to polish.

SOURCES:

PAMPA

www.pampacl.org

West System

(866) 937-8797

www.westsystem.com

Zap Glue

www.zapglue.com

Klass Kote

(612) 243-1234

www.klasskote.com

Meguiar’s

(800) 347-5700

www.meguiars.com

K&B Manufacturing

www.kbmfg.com

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6 comments

Looks great, Joe. Would this process work on a foam aircraft?

The finish looks great, however in my experience, putting a finish directly over balsa without the use of a covering material, results in a fairly weak structure that can be damaged very easily.

I'm also a car guy. Wonder how epoxy primer, Then 2 part urethane paint finish would work? Maybe too heavy?

Great article and beautiful job!

How much weight would have been added if one of the kotes was? Also it seems to me that the airframe would be extremely ridgid, which could be a good or bad thing, depending on flying style/experience level. Also curious about complications if a repair is needed.

Do you know Klass Coat offers a white primer? I use the white Primer fewer color coats are required for the color over it. I also agree with other posts I would have started with 3/4 glass cloth and peel ply directly on the wood. After side by side testing Evercoat and Zap epoxy I source my epoxy that is used from the surfing industry. Resin Research 2000F epoxy and 2100F fast hardner. Been using this product for over 15 years. Significantly easier to sand

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