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Application Guide - Above Waterline Application Systems

Surface Preparation and Priming - Fiberglass/Gelcoat

Gelcoat/fiberglass surfaces are found in four basic forms:

  1. New gelcoat and aged gelcoat which is sound; basically free of any crazing, damage or delamination.
  2. Aged gelcoat with minor crazing and oxidation but no major cracking, crazing, damage or delamination.
  3. Heavily crazed, cracked, broken and delaminated surfaces.
  4. Raw fiberglass, laminating resin with no gelcoat.

Most projects involving molded fiberglass/gelcoat usually fall into categories 1 or 2 and require very little filling or fairing. Refinishing these surfaces can be accomplished with relatively simple systems of:

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  • Cleaning and de–waxing the surface

  • Sanding the surface

  • Applying 545 Epoxy Primer

  • Topcoat application


Surface conditions described in categories 3 or 4 require more extensive attention to abrading the surface and the use of fairing and surfacing products.

Heavily crazed and damaged surfaces require thorough inspection and removal of all damaged or deteriorated materials. Cracking and crazing caused by excessive flexing of the surface may require structural reinforcement to reduce the flexing. Deep crazing and cracking must be ground out before filling to change the dynamics of the working surfaces. Just filling and painting over cracking and crazing usually results in the defect quickly “printing through” in the new finish.

Raw laminating resin is very hard and slick compared to pigmented gelcoats and fairing compounds.

Both polyester and epoxy resins must be washed with household cleanser and water before sanding or grinding. Washing removes mold release materials, un-reacted styrene on polyester surfaces and amine residue on epoxy resins.

Raw fiberglass resin must be ground with 36–60 grit paper until 100% of the surface is dull, with a 36–60 grit surface profile. Allowing even small spots of un-sanded resin in the weave of the fiber strands can lead to adhesion failures.

Fiberglass repairs often have an extra layer of laminating resin applied to give the repair a smoother finish. This allows easy sanding without exposing the fiberglass itself.

Even though these areas may appear fair and true it is important to give them the full 36–60 grit grind to ensure good adhesion of the coating system.

New and Sound Aged Gelcoat Preparation

Removal of all surface contamination (waxes, mold release products, dirt, grease, oil and mildew) is imperative to ensure adhesion of the new Awlgrip Systems.

Note: Always clean the surface before sanding. Sanding the surface with sandpaper does not remove wax or other contamination. Sanding spreads the contamination from one area to another. Sanding often melts greases and oils into the surface making it impossible to obtain a clean surface.

  1. Thoroughly clean and degrease the surface. Use commercial detergents, steam cleaners or pressure washers. Be sure all detergent residue is rinsed from the surface. Use Awlgrip Wipe-Down Solvent (NA/AP: Awlprep Plus T0115; EU: Surface Cleaner T0340) as a final wipe down of the surface.
  2. To remove surface contaminants such as grease, mold releases and flushing oils use a commercial detergent. Scrub with a sponge, soft brush, or Scotch-Brite® pad as necessary or alternatively use pressure washers/steam cleaners. Rinse surface thoroughly to remove all soap residue. Repeat process until rinse water "sheets out" over the entire surface with no breaks or holes in the water film. Allow to dry. Use Awlgrip Wipe-Down Solvent (NA/AP: Awlprep Plus T0115; EU: Surface Cleaner T0340) as a final wipe down of the surface.
  3. Inspect the surface for pinholes and small scratches. Mark the imperfections with a pencil. Do not use a felt tip marker.
  4. Sand out and feather any scratches or dents with 80 grit paper. Sand any raw resin until completely dull.

    Caution

    Do not sand excessively. This will create porosity in the surface that will have to be filled.

  5. Blow off the surface with clean, dry, compressed air while dry wiping to remove sanding dust and residue. Then wipe with Awlgrip Wipe­Down Solvent (NA/AP: Awlprep T0008 or Awlprep 400 T0170; EU: Surface Cleaner T0340) using the Two Cloth Method.
  6. Brush or roll sanded areas with Hullgard Extra.
  7. If necessary, fill scratches, gouges and dents with Awlfair LW. Allow to cure 12+ hours.

    Caution

    If polyester putties are used they should be kept to an absolute minimum. Only use polyester putties for pinholes and very slight scratches or dents. Polyester putties shrink and distort rapidly. Epoxy fillers are much more stable.

  8. Sand the whole surface smooth with 80–120 grit paper. Remove all gloss from the gelcoat, oxidized gelcoat and lightly crazed areas. Feather any dents or scratches. Do not sand excessively. This will create porosity in the surface that will have to be filled.
  9. Blow off the surface with clean, dry compressed air while dry wiping with clean rags to remove sanding dust and residue. Wipe surface with Awlgrip Wipe­-Down Solvent (NA/AP: Awlprep T0008 or Awlprep 400 T0170; EU: Surface Cleaner T0340) using the Two Cloth Method.

After sanding the surface is now ready for priming.

Surfaces with heavily crazed, cracked, broken, delaminated gelcoat and raw laminating resin

  1. Remove surface contaminants using a commercial detergent or a powdered household cleanser. Scrub with a sponge, soft brush or Scotch-Brite® pad as necessary. Alternatively use pressure washers/steam cleaners. Rinse surface thoroughly to remove all soap residue. Repeat process until rinse water "sheets out" over the entire surface with no breaks or holes in the water film. Allow to dry.

  2. Inspect heavily crazed areas or damaged areas for excessive flexing or structural damage. Make structural reinforcements and fiberglass repairs as needed.

  3. Remove heavily crazed, broken and delaminated gelcoat or fiberglass laminate.

  4. Thoroughly grind out damaged areas with a 36–60 grit paper. Heavy crazing must be completely removed. Grind raw resin areas with 36–60 grit paper.

  5. Areas that have been thoroughly ground out need to be primed with Hullgard Extra. Two or three coats may be needed. Allow to dry 12+ hours.


Depending upon the conditions it may be possible to proceed to filling and surfacing without the need for sanding (See Fairing and Surfacing section for detailed information).

Please consult product datasheet for further details.