8.
Gel coat
As
soon
as
the laminated patch repair
is
hard
it
can
be
profiled
by
sanding with 80-
grade paper. Fill the larger surface faults with white polyester putty. Finish the
preparation with
150 grade paper to yield a surface which
is
levelled and evenly
abraded to improve gel adhesion.
Before
applying the gel coat the repair must
be
cleaned of
all
traces of abrasive dust,
releasing agents and other foreign bodies.
The
gel coat should
be
applied with a soft brush and built
up
in
several layers until the
laminate does not shine through. The individual layers should harden, and each layer
be
rubbed down with 360 grade wet and dry so that one can see where an additional
gel
coat
is
required.
The final surface finishing
is
done with 600 or 800 grade wet and dry paper. Finish off
with polish.
9.
Repair
of
fittings
a) Steel Fittings
Repair of steel fittings should,
in
principle, only take place after consultation with the
manufacturer.
Welded fittings are of
steel specification 1.7734.4 and/or 1.0308.1
(St.
35.4). Welds
should
be
made only using the tungsten inert gas fusing welding process with the
welding
material 1.7734.2 (for 1.7734.4 alloy) and 1.7324.0 (for 1.0308.0 and/or
junctions of 1.7734.4 and
1.0308.1 alloys).
b)
Aluminium casting fittings
Aluminium casting fittings (alloy 3.2374.6: GA1Si7Mgwa) cannot
be
repaired. Cracked
or bent aluminium cast parts must
be
replaced
by
new components.
Note: Bent aluminium castings cannot
be
straightened. They will
be
brittle at the
deformation site, which
is
not permitted.
c)
Wing - fuselage spigots.
The spigot lock
(4
off
in
the fuselage) between the wings and fuselage
is
made by six
steel balls of 6mm diameter, which are pushed
by
the locking
ring
on the fuselage
fitting into the groove
in
the spigot pins
on
the wings. If one or more balls are missing,
the fuselage spigot
lock must
be
replaced with a new fitting.
10.
Larger repairs
Larger repairs are to
be
carried out
by
the manufacturer or other recognised repair
shops (according to data supplied
by
the manufacturer).
Larger repairs
include for example:
- broken off wings, snapped fuselage, tail units, rudder, wing main spar damage
-
pulled out main wing fittings
in
the fuselage or wing, damage to the tailplane/fin
fittings, damage to the
mid
fuselage section linking undercarriage to wing fittings.
- damaged GRP
laminates (showing white areas, or delamination)
in
direct proximity to
the main fittings.
31
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