Repairing Of Cracks Diagrams - Piper Navajo Chieftain PA-31-350 Service Manual

27
DOUBLER
PLATE
BONDED TO UNDERSIDE
OF DAMAGED AREA
Figure 4-27. Repairing of Cracks
b.
Surface Scratches. Abrasion or Ground-in-Dirt: (Refer to Figure 4-23.)
I .
Shallow scratches and abraded surfaces are usually repaired by following directions on containers of
conventional automotive buffing and rubbing compounds.
.
If large dirt particles are embedded in thermoplastic parts, they can be removed with a hot air gun
capable of supplying heat in the temperature range of 300
°
to 400°F. Use care not to overheat the material. Hold the
nozzle of the gun about
1/4
of an inch away from the surface and apply heat with a circular motion until the area is
sufficiently soft to remove the dirt particles.
3.
The thermoplastic will return to its original shape upon cooling.
c.
Deep Scratches. Shallow Nicks and Small Holes: (Less than I inch in diameter.) (Refer to Figure 4-24.)
I.
Solvent cements will fit virtually any of these applications. If the area to be repaired is very small. it
may be quicker to make a satisfactory cement by dissolving thermoplastic material of the same type being repaired in
solvent until the desired paste-like consistency is achieved.
2.
This mixture is then applied to the damaged area. Upon solvent evaporation, the hard durable solids
remaining can easily be shaped to the desired contour by filing or sanding.
3.
Solvent adhesives are not recommended for highly stressed areas, or thin walled parts or for
patching holes greater than
1/4 inch in diameter.
4.
For larger damages an epoxy patching compound is recommended. This type material is a two part.
fast curing. easy sanding commercially available compound.
5.
Adhesion can be increased by roughing the bonding surface with sandpaper and by utilizing as much
surface area for the bond as possible.
6.
The patching compound is mixed in equal portions on a hard flat surface using a figure eight motion.
The damaged area is cleaned with perchlorethylene or VM&P Naptha prior to applying the compound. (Refer to
Figure 4-25.)
7.
A mechanical sander can be used after the compound is cured, providing the sander is kept in
constant motion to prevent heat buildup.
Reissued: 9/23/80
STRUCTURE
NAVAJO CHIEFTAIN SERVICE MANUAL
1H5