|
Regardless
of the care taken in producing fiberglass reinforced parts,
some of them will require repair. Defects are caused by operator
error, defects in the mold, contamination, rough de-molding
and impact and abrasion during assembly, handling, and storage.
When
a defect is discovered, determine and eliminate the cause
so that it is not repeated in the production of subsequent
parts. Next,
determine which of the three major repair types fit the defect:
marred or slightly scratched area; deep defects which require
routing; or damage to the laminate behind the gel coat.
MARRED
OR SCRATCHED AREAS
STEPS
1. Wet-sand the damaged area using a good quality
320 grit sandpaper followed by successively finer grits
ending with 600. Use a sanding block when applicable and
always sand in the same direction.
CAUTION:
Use 320 grit only when the defective area is deep. Minor
scratches can be rubbed out with 400 grit followed by 600
grit or rubbing compound.
2.
Wash sanded area with clean acetone. Be sure it is completely
free of sanding dust and grit both during and when the sanding
operation is completed.
3.
Use a good quality rubbing compound and buffer to polish
sanded area. It is advisable to use a white or translucent
compound especially with white or pastel colored finishes.
Use liberal amounts of compound, minimal pressure and keep
buffer moving to prevent heat buildup.
4.
When the surface appears to have a dull gloss, use a
polishing compound to bring the gloss close to the original
gloss.
5.
Wash compounded and polished area with clean acetone.
6.
Apply an even coat of paste wax and hand buff.
DEEPER
DEFECTS - ROUTING
STEPS
1. Grind out the defective area with a sharp routing
tool. Do not leave any undercut edges. Feather in the defective
area.
2.
Sand entire defective area with 280 grit dry sandpaper,
feathering in the edges. Use an air hose to blow out the
dust.
3.
Wash area with clean acetone.
4.
Catalyst and mix the gel coat to repair defective area.
(Epoxy putty may be preferred especially if damaged are
is in hull or area below water line.) A reinforced putty
can be used to fill in areas where there is a deep defect
(more than 30 mils) which does not affect the laminate strength.
Follow with a patch. For reinforced putty, mix 10% filler-milled
glass fibers, 1% thixotrope to resin or gel coat. Mix well
until obtaining smooth, paste-like consistency. Then catalyze,
fill, allow to cure and sand for spray patch.
CAUTION:
Use the same production batch of gel coat applied to the
part being repaired. Use 2 cc MEKP per 100 grams of gel
coat. Hand stir for one minute prior to applying to repair
area. Fill area and smooth with flat edge of putty knife.
Leave slight rounded over-fill to allow for shrinkage of
the patch on curved areas Cover with wax paper or cellophane
to exclude air from contact with the surface. Do not work
at surface temperatures below 60º F.
5.
When patch is firm and free of exotherm heat, remove wax
paper or cellophane. Permit patched area to cure for a minimum
of one hour. Wet-sand with 320 grit sandpaper until rough
surface of patch is removed. Proceed with 600 grit and wet-sand
until smooth.
CAUTION:
Always use a sanding block and sand in the same direction.
Continue to wet-sand until all shiny edges on patched area
have been removed.
6.
Wash area with clean acetone.
7.
Inspect area for defects. If area is non-porous and
free of blemishes, proceed with rubbing compound, liquid
polish and wax as outlined in "Marred or Scratched
Areas" Steps 3 through 6.
8.
Depending upon the degree of surface irregularities,
it may be necessary to repeat Steps 4 and 5 or reduce the
viscosity of the gel coat consistency and apply with a touch-up
gun. This is accomplished by reducing the gel coat with
Max. 20% (wt.) styrene monomer. Catalyze mixture with 2%
(wt.) MEKP. Apply the reduced mixture on the area to be
repaired using a uniform, even spray stroke. Permit 5-10
minutes to set and then topcoat with a water soluble polyvinyl
alcohol parting film. When the patch is cured, the PVA film
can be removed with tap water. Proceed with Steps 3 through
6 as outlined in "Marred or Scratched Areas."
|
