Damage analysis before repairing the fiberglass hull

One of the most common repairs to fiberglass (GRP) is on boats. The hull can be damaged by physical force and have dents and holes as well as chipping and exfoliation. The repair of osmosis damage is necessary in almost all older boat hulls sooner or later.

minor repairs

If there is a single damage such as cracks, fissures or small holes in the fuselage made of fiberglass, they can usually be repaired with sanding and then backfilling with spatulas.

For large-scale damage, it must be checked how deep they interfere with the structure of GRP. Depending on the potential impact on stability and durability of the entire hull, in some cases, it may be necessary to partially think of lamination reinforcement.

Damage due to osmosis

An elaborate repair of the fuselage is required when osmosis has occurred at the GRP. The formation of bubbles by air bubbles, which has increased by the physical process of osmosis, is usually not directly on the surface of the fuselage.

The air bubbles must all be completely exposed, dried and closed. Since the air inclusions are normally in the contact layer between GFK and gelcoat, a relatively extensive removal is necessary.

Everything for fixing a fiberglass hull

  • abrasive
  • putty
  • Possibly gelcoat repair kit
  • Glass fiber mats or glass fabric
  • epoxy resin
  • Harder
  • Pull knife, cutter, wire brush
  • grinding machine
  • spatula
  • Vacuum cleaner or extraction system
  • Respiratory and eye protection
  • Full body protective coverall
  • rubber gloves
  • Absorbent towel

1. Damage analysis

Make a comprehensive damage analysis. If necessary, you must expose osmosis bubbles. If you are not sure osmosis is present, close all hatchways in the boat interior and do a smell test after three days. If a sour smell has developed, you must go out of osmosis.

2. Grinding works

Sand down all marked damage points and make sure that you get fiber-free and smooth surfaces.

3. putty work

For repair use as putty for underwater hull parts only Epoxidharzspachtel with hardener in the two-component system.

4. Reconstruction

For larger damaged areas, you must assess the stability and overall condition of the hull. If necessary, you must re-laminate parts of the hull area with glass cloth, fiberglass mats or interspersed glass cuttings.

5. Painting / varnishing

After the fine sanding, seal the hull with the paint, gelcoat or topcoat that matches the original one. A final polishing completes the repair.

Tips & Tricks

If you suspect no visible osmotic damage, leave the test to a specialist. Any other repair can be pointless otherwise.

Video Board: Fibreglass Hull Repair