Surface preparation and cleaning are the most important steps to
insure proper adhesion.
(4) Surface Preparation. Scuff the masked off area with 120 grit sandpaper. Only sand in a
(5) Cleaning. Wipe the masked area several times with cheesecloth or machinery towel
dampened with isopropyl alcohol or denatured alcohol, then wipe once again with a clean, dry cloth.
Perform procedural Steps (6) through (10) for one blade at a time.
(6) Application of Adhesive Promoter. Apply a thin coat of No. 86 adhesive promoter to the
masked area. Allow to dry at least five minutes, but not more than one hour before applying tape.
Promoter can extend beyond ends of tape.
(7) Polyurethane Tape Preparation. Peel back one of the center (1 inch wide) backing strips from
the 4" wide tape approximately 3 inches as shown in figure 3-1, sheet 3.
(8) Tape Alignment. Align the tape in the position shown in figure 3-53 before pressing to blade.
(9) Tape Application. When the tape is in proper position, press the exposed portion on 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 the 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 application process may be removed by continuous squeegee stroking toward the
edge of tape or by puncturing the bubbles with a needle and applying pressure to the wet adhesive.
Do not puncture bubbles after the adhesive has dried.
(10) Masking Tape Removal. Remove masking tape.
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.
The rotor blade must be smooth. Any dirt inclusions or paint rough-
ness 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