We offer complete repair of osmotic blister problems.
Osmosis, the main cause of blistering in fiberglass hulls, is a process of degeneration within a fiberglass laminate. It is caused by a chemical reaction between water and unreacted substances remaining in the manufactured hull.
The water enters the hull through the gelcoat and, once inside, reacts with the chemical components creating acidic substances. These substances create pressure behind the gelcoat, which causes blisters and eventually cracking. Once the gelcoat is breached in this manner, the underlying laminate is capable of absorbing water like a sponge. The accumulation of a large number of blisters will, in turn, create a serious hull delamination. The degree of structural damage will increase as the blisters fracture and penetrate deeper into the layers of the hull.
Osmosis is not only caused by water on the outside of the hull - bilge water from the inside can also cause a problem. It is therefore worth making efforts to keep your bilges dry.
Any unprotected hull is likely to show signs of osmosis eventually, like rust on a car.
The exact length of time before osmosis occurs depends on many factors, including: the type of water in which the hull is moored; the temperature of the water and most importantly, the quality of the original hull construction.
In some cases, reactive impurities in the gelcoat and laminate will cause osmosis in the early life of the boat. This is a structural problem and should be referred back to the boat manufacturer. However, even well-built, fiberglass hulls will eventually experience osmosis and blistering. This is why we recommend applying an epoxy protection layer, even to new boats.
Blisters are the most common warning sign of osmosis problems. Blisters can vary from small pinhead blisters, to areas as large as the palm of a hand. The presence of any fluid behind a blister indicates a potential problem. If the fluid has a pungent, vinegary odor or feels greasy or sticky when rubbed between the thumb and forefinger, there is a high probability of osmosis. Before any treatment is carried out, you need to establish what has caused the problem.
Other warning signs to look for:
Star Crazing - This effect can occur where the gelcoat is brittle. Fine cracks usually form due to severe flexing or impact damage, allowing water to seep into the laminate.
Pinholes - Tiny bubbles present in the gelcoat reduce its effectiveness and promote rapid water absorption.
Prominent fibers - Seen protruding beneath or through the gelcoat and can cause "wicking" where water is drawn into the hull by capillary action.
In many older vessels you may only see crazing or cracking of the gelcoat. You may never see a blister. In this scenario, the gases created by water reacting with WSMs simply escape through the lesions in the gelcoat.
Once a blister problem is identified, we determine the depth and severity of the damage. Repair of minor blister problems may require simply grinding out the affected area, and filling and fairing with epoxy laminate and fillers. We use an electronic moisture meter to determine whether the problem is localized, or affects the entire wetted surface.
If it is determined that a large portion of the hull is affected, removal of all gel coat and perhaps even a thin layer of the underlying fiberglass is indicated. We accomplish this with a specially designed peeler, and subsequently sand the affected surfaces.
Drying of the hull can then be done conventionally, by keeping the boat dry and out of the water for several month to a year, to allow the moisture to evaporate from the hull. Alternatively, Anchors Away can use its HotVac technology to apply a heated vacuum to the hull surface, and dry the boat in a matter of days.
It is important that the hull be very dry before moving to the next steps, to avoid trapping moisture in the hull with epoxy coatings. Trapping moisture in the hull will not only diminish the new coatings’ adhesion to the hull, but may allow for continued blistering
If more than 80 mils of material had to be removed, the vessel will usually require a new laminate. Anchors Away recommends Interlux epoxy resins and laminates, followed by appropriate mil thicknesses of a barrier-coating epoxy product such as Interprotect, PetitProtect, or Sea Hawk’s Tuff Stuff. Only after these products have been applied to at least a 6 mil dry film thickness do we apply two coats of antifouling paint.