TB 1-1615-351-23
(9) When the tape is in proper position, press the exposed portion of the blade as close to the
leading edge as possible. Press down on the tape, working toward the trailing edge to prevent trapping
air bubbles. See figure 3-1, sheet 4. Peel backing strip back while keeping tape aligned and pressing
down toward trailing edge. Remove the backing strips one at a time, working toward the trailing edge.
See figure 3-1, sheet 5. Thoroughly press down tape. Any bubbles encountered during the application
process may be removed by continuous squeegee stroking towards the edge of tape or by puncturing
the bubbles with a needle and applying pressure to the wet adhesive.
CAUTION
Do not puncture bubbles after the adhesive has dried.
(10) Masking Tape Removal. Remove masking tape.
NOTE
Repeat Steps (6) through (10) for each blade.
NOTE
The structure to which the polyurethane protective tape, 3M 8663, is to be applied
should be in recent overhaul or new condition. This means that repairs have been
made and the part has been primed and painted in accordance with the appropriate
technical directive for that part.
NOTE
The rotor blade must be smooth. Any dirt inclusions or paint roughness must be
sanded off the surface using 400 grit sandpaper. Simply, the surface should be at
least as smooth as you can get it by sanding with 400 grit sandpaper.
(11) Clean the surface by rinsing with isopropyl alcohol and wiping dry with clean untreated paper towels
or rags.
(12) Using a small clean rag, apply a thin coat of #86A adhesion promoter to the entire area of the rotor
blade that is to be covered with 3M 8663 PPT film. Let the 86A dry 15 minutes, prior to application of 3M
8663 PPT film.
(13) Cut a sheet of 8663 polyurethane protective tape (PPT) to the size of the area to be covered leaving a
margin of 1/8 inch around the perimeter. This margin will later be used for application of the edge sealant
around the perimeter of the PPT sheet.
(14) Prepare a "wetting" solution as follows: To a pint sized spray bottle, add 2 drops of liquid dishwashing
detergent and 1/2 cup of isopropyl alcohol and fill the bottle with clean water. (The actual mixture is: 75%
water, 25% isopropyl alcohol and 2 drops of liquid dishwashing detergent per one liter of solution.)
(15) Remove the liner from the sheet of PPT. Liberally spray the adhesive side with "wetting solution"
that was prepared in step #4 above. Also spray the surface of the part to which the PPT is to be
applied.
(16) Carefully position the PPT on the part. Use a plastic squeegee, starting at the middle of the
sheet, and remove the wetting solution from beneath the PPT sheet, by using long overlapping strokes.
If you should trap an air bubble, lift an edge to allow the bubble to be removed. When the edge is lifted,
respray with more "wetting solution" to insure that no air is trapped under the PPT. Use a clean rag to
mop up the excess water solution at the edges to prevent the water solution from "wicking" back under
the tape.
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