Technical data

13773-001
51-20
Page 330 Nov 2000
(1) Initial-Cure
An initial-cure must be performed before handling the repaired area. Cure time at temperature
for the initial cure is:
(a) 5 hours at 125°-150°F (52°-66°C)
(b) 3 hours at 150°-195°F (66°-91°C)
(2) Post-Cure
Post-Cure must be completed before the assembly is ready for service. Multi-step post-cure may
be used providing the total time at temperature meets the minimum requirement. Initial-cure
requirements must be met if assembly will be handled between post-cure steps. Cure time at
temperature for the post cure is:
(a) 10 hours at 175°-195°F (79°-91°C)
(3) Heated Air Cure
(a) To perform initial-cure or post-cure with heated air, an enclosure around the repair is
required. The enclosure can be made from any material that will withstand around 250°F
(121.1°C). Plastic sheet taped to the structure is often used. If plastic sheet is used, man-
ufacture a simple structure to ensure that the plastic stays clear from the repair area.
(b) To supply heated air, use a common hair dryer. More sophisticated equipment may be
used if available. Avoid hot air guns, as temperatures achieved are too high for this appli-
cation. Place the hot air source so that it doesn't contact the structure and is not blowing
directly at the repair area.
(c) Temperature of the repair is critical, for the resin must be in the specified range for both
temperature and duration. A thermocouple, or similar surface temperature measuring
device, shall be placed in contact with the panel immediately adjacent to the repair. At
least one temperature measuring device should be used for every 1-2 square feet of
repair area. It is recommended that at least two temperature measuring devices be used.
(d) Repair temperature is controlled by air temperature. Air temperature should be approxi-
mately 15°-25°F (8.3°-13.9°C) higher than the desired repair temperature. The exact air
temperature required is dependent on many factors such as shop temperature, insulation
of the enclosure, thickness of the repair, etc. Part temperature can be controlled by cutting
vent holes in or insulating the enclosure and/or by insulating the backside of the repair
area. Be sure to remove all insulation after completing cure.
(e) Bringing the part temperature up slowly is preferred, this allows the resin to solidify at a
lower temperature. During the first part of the cure cycle the repair plies should be
observed frequently. Any air trapped within the repair will expand when heat is applied. It
will be necessary to deflate any bubbles that form. Lance bubbles with a scribe or pin, and
push the ply down with a brush. This must be done before the resin solidifies.
(4) Other Cure Methods
Heat blankets are also commonly used for repairs. Use equipment per manufacturer’s
instructions.