Osmosis is probably one of the main reasons of concern to the buyer of a fiberglass boat.
Fortunately, the osmotic phenomenon, although of considerable impact, is unlikely to lead the boat in the short span of a few seasons to be unsafe, even when it happens structurally.
The boat will certainly depreciate its value and just as surely place the owner in the uncertainty of having a diseased hull.
Let me describe the osmotic phenomenon using the words of one of my masters i.e. one of the pioneers of the appraisal profession as well as a Naval builder, namely Sergio Boghi ” In recent years we realized that fiberglass is not a perfect material as it was thought to be. Osmosis happens when some water enters the laminate forming pockets. At the beginning, it’s limited between the gelcoat and the first layer of fiberglass and are easily visible from the outside, and later they can also manifest themselves between the innermost layers causing their delamination resulting in a strong reduction in the mechanical strength of the hull.
These pockets or bubbles occur when three conditions occur simultaneously:
1) It is necessary that there is water inside the laminate, which can come from: hull built in a wet environment, materials used such as wet mats or mattes, excess porosity due to poor processing of the outer layers and gelcoat.
2) It is necessary that there are water-soluble substances in the fiberglass from poor curing of the polyester resin or from the poor quality resin itself.
3) Finally, it is necessary that inside the fiberglass there are air spaces left empty where water can penetrate; poor impregnation, poor adhesion of the gelcoat to the outer layer.
Having said that, then, we find that a number of construction defects must interlock and that, for example, in recent decades, shipyards have been running for cover either by intervening in the workmanship or by improving the materials.
What if your hull has osmosis anyway, how do you go about it?
First, it is essential to contact only professionals both to identify the problem and to analyze the spread of the problem. Secondly, choose the shipyard that will be able to perform the anti-osmotic cycle ensuring that the materials are applied at the right time and of the highest quality thus avoiding a relapse to future osmosis.
It is more common than you think to find boats that again exhibit osmosis even worse than the first time precisely because of sloppy workmanship.