2 Part Epoxy and Wing Coverings

[markc]

Folks

We are planning on Priming all our Aluminum Wing Parts with a 2 Part Green Epoxy Primer.

Question:

Has anyone had any experience on the different covering systems and the chemicals used and how well the work with a 2 part epoxy.

I am wondering if we sould not be masking off where the fabric will attach to the aluminum??

Many thanks

[KOZ]

Sounds like allot of unnecessary work but if thats the way you want to go use the epoxy that STITS produces. It's really good stuff! Many of the other epoxies are not compatable with MEK. Also, the acid etch and alodine treatment of all parts before primer are the most important part of the job. Jim and Dondie Miller in Ohio can set you up. 1877-877-3334
Koz

[nanook]

markc: KOZ brings up a good point. The acid etch (alodyne) prep. before you paint is the biggest part of that job. You don't mention what type wing ribs you have, but the original piper type ribs are not easy to etch properly. they tend to trap liquid on the inside and are hard to rinse out, (read corrosion) The new style ribs don't have this problem. The two part epoxy paint is the way to go, but just because it's two part doesn't mean that MEK won't pull it. You need to buy a known MEK impervious paint or test it before using it, if you aren't sure.... So you open up another can of worms when you decide to paint your wing structure. if the paint pulls the fabric pulls. You may be better off fogging the inside of the wing after covering (and cured) with a corrosion preventer that is safe to use with whatever cover system you are using.(ask the process owners what they recommend)

[Steve Pierce]

I use the Stits white two part epoxy for this. It is easier to inspect with a light color and it won't come off with any of the glues used by the top three fabric system producers. I use the Stits primer because it is locally available (Ft. Worth) and I don't have to pay the ridiculous Haz Mat charges. Used white Epi-Bond before this with good results till it wasn't available locally. Helped a friend cover his Cub with Air-Tec. He insisted that the expensive automotive two part epoxy he bought was MEK proof. As we were glueing the second section of fabric to the structure I could see the first lifting off. Needless to say there were a few choice words and it had to be blasted again. I recommend testing a small part first. I had 3 frames blasted, primed and painted at Air Tractor recently. I had the painter paint a couple of strips with the primer and paint they use and then glued fabric to it, let it set up overnite and pulled it off. Also soaked it in MEK.

I etch and alodine all my aluminum and then epoxy prime. Fixing to do my wing spars, ribs etc. It had been in the Nortwest and had some surface corrosion. The Super Cub wings I did last winter were painted with the Stits white two part epoxy and it is really easy to inspect now. Much brighter than that old dark green stuff.

[Big AK]

Yeah, I love the way white epoxy brightens up any area requiring inspection. Even an engine mount painted white helps with inspections, plus, you know it's really clean if it's white and clean.

[Gloc]

I second all the above posts regarding etching and alodine all aluminum parts prior to painting. I'm also an advocate of white or light grey for steel and aluminum parts. A crack, and the oxidation it produces will show up better with the lighter colors on the steel parts.

I like the Polyfiber, white 2 part epoxy and the PPG, DP-402 white 2 part epoxy the same, I can get the DP-402 locally and have to drive/fly to get the Polyfiber or pay to have shipped.

[StewartB]

How come nobody mentions chromate epoxy? It works for Boeing.
http://www.detcomarine.com/slacguide.htm#AIRCRAFT%20PRIMERS

SB

[Phil Kite]

All 2K epoxy primers will lift with strong solvents if they are not fully cured. Most epoxies take many days under standard conditions before they are cured. If the temeperature is cool, they will take much, much longer. The recommended procedure for primming aluminum is acid etch, alodine then prime shortley after. As mentioned earlier, etching and alodineing wings is not very practicle. Another method "almost" as good is to use an etching primer (vinly wash) and then use your epoxy. These wash primers use an acid in the mix which helps bite into the clean aluminum.

[Glidertow]

Last weekend I primed my Rudder, stabs, and elevators using the Poly-Fiber 2 part epoxy. Mixed with no reducer it still seemed very thin for spraying. I did not feel as though I got a good coverage on the first coat. Are others using this product finding they have to spray a second coat. Other primers I have used are not as thin, but are not epoxy.

[Big AK]

Yes, multiple coats.

Be careful that subsequent coats are not heavy, as they'll wash away the first one quite easily. I have experience in this error!

On ANY epoxy primer I will do at least two coats. Usually allowing a flash-off time for the solvents of about 20 minutes, depending on size of the project and whether it's laying flat or is round tubing, or sitting vertical and upright.....i.e., how prone to running the surface will be.

Good Luck.

[R. JOHNSON]

Does anyone know of a good, black epoxy, that glue will not lift. In Cub Club Tom Hegys PA-12 fuselages look black but I don't know if its epoxy or just a black topcoat over epoxy.

[bob turner]

I shot my wings with a light coat of lacquer based zinc chromate in 1968. They looked pretty good to start with, but the IA said to "mist" them, and I did. Thirty-six years later, they still look pretty good. Dope lifts laquer-based products, but since I use the seam overlap procedure, pull-off is a non-issue. Different story on fuselage; I use epoxy.