technical manual applicable to the aircraft.
The paragraphs that
follow give general information on cleaning techniques, safety
practices, application, and curing.
Cleaning Techniques.
Loose foreign material can be removed by
using a vacuum cleaner on the area to be resealed. The old sealant
can be scraped from the repair area with a sharp plastic, phenolic,
or hardwood block. Care must be taken not to make any scratches. A
stripper and cleaner are used next to remove all the old sealant.
Cleaners in general use are aliphatic naphtha, ethyl acetate, or
lacquer thinner. The naphtha can be used satisfactorily by dipping a
clean cloth or brush into the naphtha and then scrubbing the surface.
After using aliphatic naphtha, a clean cloth must be used to wipe
metal surfaces dry.
The cleaner must not be allowed to dry on a
metal surface.
The surface can be checked for cleanness by pouring
clean water over it, after it has been wiped dry of the cleaner. If
the surface is not free of an oily film, the water will separate into
small droplets.
Safety Practices. In addition to protecting undamaged sealants and
acrylic plastic from the stripper compound, users must practice
personal safety. For example, if artificial lighting is used when a
repair is being made, the light must be explosion proof.
Clothing
that prevents these chemicals from touching the skin and goggles to
protect the eyes must be worn.
Ventilation to dissipate fumes must
be ensured, and no smoking regulations must be enforced.
Sealant Application.
Rubber seals must be applied, or installed,
immediately after the seal frame is cleaned. A clean paint brush can
be used to apply an even coat of rubber cement upon the metal parts
and the seal surfaces to be joined.
If the cement needs thinning,
apliphatic naphtha can be used.
The cement must be allowed to dry
until it becomes quite sticky before joining the seal to the metal.
The seal is joined to the metal by pressing it firmly along all
contact points. Next, the seal retainers are installed, and the seal
is allowed to set for 24 hours before using. Toluene, or an approved
solvent, can be used to clean the brushes used to apply the cement.
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AL0992
Sealing compounds are applied only when the contacting surfaces are
clean.
The compound must be spread from the tube by using a
continuous forward movement to the pressure side of the joint.
The
compound is spread 3 inches beyond each end of the repair area. If
the compound is in bulk form it is applied with a pressure gun.
Curing. Two layers or coats of compound are
frequently required.
If two coats are needed, the first coat must
be allowed to cure
before the second is applied.
The compound
must cure until it
becomes tough and rubbery before the surfaces
are joined.
Curing
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