9.  
After repair is complete, sand to obtain a good surface finish.

CRACKS: (Refer to Figure 51-6)
1.  
Before repairing a crack in thermoplastic parts, first determine what caused crack and alleviate condition to prevent it from recurring.

2.  
Drill small stop holes at each end of crack.

3.  
If possible, bond a double plate to reverse side of crack to provide extra strength.

4.  
The crack should be V grooved and filled with repair material such as solvent cement, hot melt adhesive, epoxy patching compound, or hot air weld.

5.  
After repair has cured, sand to match surrounding finish.

51-10-00 Page 51-13 Issued: April 1, 1997

51-10-00 Page 51-14 Issued: April 1, 1997
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Figure 51-7. Various Repairs 
51-10-00 
Page 51-15 
Issued: April 1, 1997 
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REPAIRING MAJOR DAMAGE: (Larger than 1 inch in diameter.) (Refer to Figure 51-7.)
1.  
Make a patch of same material and cut slightly larger than section being repaired.

2.  
When appearances are important, large holes, cracks, tears, etc., are repaired by cutting out damaged area and replacing with a piece of similar material.

3.  
When cutting away damaged area, under cut perimeter and maintain a smooth edge.  The patch or plug should also have a smooth edge to ensure a good fit.

4.  
Coat patch with solvent adhesive and firmly attach it over damaged area.

5.  
Let the patch dry for approximately 1 hour before any additional work is performed.

6.  
Fill hole, etc.  with repair material. A slight over filling of repair material is suggested to allow for sanding and finishing after repair has cured.  If patching compound is used, repair should be made in layers, not exceeding a 1/2 inch in thickness at a time.  Allow compound to cure and ensuring a good buildup of successive layers.

STRESS LINES: (Refer to Figure 51-8)
1.  
Stress lines produce a whitened appearance in a localized area. They are generally caused by severe bending or impacting of material. (Refer to Figure 51-9.)

2.  
To restore material to original condition and color, use a hot air gun or similar heating device to apply heat to affected area.  Do not overheat material.

PAINTING THE REPAIR:
—CAUTION— NOT ALL LACQUERS OR ENAMELS CAN BE USED ON THERMOPLASTIC. SOME PAINT SOLVENTS WILL AFFECT AND DEGRADE THE PLASTIC PROPERTIES.
—CAUTION— DO NOT USE HARD, BRITTLE COATINGS IN FLEXING, IMPACT, OR HIGH STRESS AREAS.  SUCH COATING MAY CRACK, CREATING A WEAK AREA.
1.  
An important factor in obtaining a quality paint finish is the proper preparation of the repair and surrounding area before applying any paint.

2.  
Clean parts before painting with a commercial cleaner or a solution made from 1/4 cup of detergent mixed with one gallon of water.

3.  
Use lacquer or enamel paint for thermoplastic repair.

4.  
Do not use hard, brittle coatings in flexing, impact, or high stress areas.  Such coating may crack, creating a weak area.

SAFETY WALK REPAIR SURFACE PREPARATION
1.  
Clean all surfaces with a suitable cleaning solvent to remove dirt, grease, and oils.  Apply solvents by dipping, spraying, or mopping.

2.  
Check no moisture remains. Wipe surface with a clean dry cloth.

3.  
Outline the area to which liquid safety walk compound is to be applied, and mask adjacent surfaces.

—Note—
For newly painted surfaces, allow 2.5 hours minimum drying time before application of safety walk.
51-10-00 Page 51-16 Issued: April 1, 1997
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PRODUCT LISTING FOR LIQUID SAFETY WALK COMPOUND
1.  
Suggested Solvents: Safety Solvent per MIL-S-18718 Sherwin Williams Lacquer Thinner R7KC120 Glidden Thinner No. 207

2.  
Safety Walk Material:
Walkway Compound and Matting Nonslip (included in Piper Part No. 179-872)

51-10-00 Page 51-17 Issued: April 1, 1997
APPLICATION OF LIQUID SAFETY WALK COMPOUND
— Note —
Apply in an area which is free of moisture for a period of 24 hours minimum after application.
— Note —
Do not apply when surface to be coated is below 50°F (10° C).
— Note —
Do not walk on coated surface for a minimum of six hours after final coating.
1.  
Mix and thin liquid safety walk compound per manufacturer’s instructions on container.

2.  
Coat surfaces with a smooth, unbroken film of liquid safety walk compound.  A nap type roller or a stiff bristle brush is recommended, using fore and aft strokes.
　
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