7. Primer/Filler Application a. Spray Gun Choice – Any good quality commercial grade spray equipment will work including HVLP such as the Croix. b. With the Croix HVLP equipment most of the overspray problem is eliminated. Also the turbine air can be used for breathing if positioned in a “clean air” area. c. Select a medium size tip/ air cap for Air-Tech materials. It sprays like most polyurethanes or enamels. d. The materials may be applied at temperatures of 50-100 F regardless of humidity as long as the spread between ambient temperature and the dew point is 5°F or greater. The materials are not prone to “blush”. e. Clean fabric per Air-Tech procedures with FAA/PMA approved RF 4020 Rev.
3 Fabric Wash. f. Apply the coats of primer “wet” - No tack coats! Wet coats allow the polyurethane to flow and level properly. g. The first coat of primer can be brushed if one wishes. We spray all coats but some prefer brushing that first coat. h. The primer has a relatively short pot life so mix small quantities. i. Up to about 85°F use the RT 4070 Rev. 4 thinner; above 85°F use RT 4085 Rev. 4. Never store materials in a shed or area where temperatures will exceed 100 F. j. Materials to be used should be at ambient temperature not hot or cold from storage. k.
If using a turbine system which heats the air note the flash time; if too short additional hose can be used or possibly a slower thinner or a blend of both. l. Apply the primer coats (cross coats) on after the other allowing enough time for “flash off” in between. m. After the final primer coat allow the part to cure overnight. It can then be sanded as required to remove bugs or trash. No overall sanding is required. 8. Color Coats a. After the final primer coat the color should be applied within 5 days for maximum adhesion. After 5 days the entire surface must be wet sanded for adhesion. b. Use of other color coats. The Air-Tech process is an FAA approved system.
Best results will be obtained using Air-Tech color – maximum adhesion, maximum flexibility and the best finish. c. Spray the color coats on “wet” – Do not use tack coat. d. Allow the first coat to dry to the touch before applying the second coat. e. Apply only enough material to get color holdout. Excess materials serve no purpose. f. Normally the process requires no sanding or buffing; however if one is preparing a competition showplane fantastic results can be obtained as follows: 1. After the final primer coat is allowed to cure overnight sand as necessary to gain a smooth surface for topcoating. 2. Apply one color coat and allow to cure 2-3 days. 3.
Wet sand the surface using fine sandpaper 380 or finer. 4. Apply second color coat. 5. Normally buffing would not be required but if one wishes to buff Air-Tech buffing procedures should be followed. Begin after 8-12 hrs of cure. Finally, please remember we are here for any question you have. Call us before any step if you are uncertain about how to proceed. We welcome these calls anytime on our Watts Line 1-800-325-1650.