Osmosis is a chemical/physical phenomenon that allows a liquid to pass through a wall or semi-permeable membrane.
The passage, usually of water, takes place from the least concentrated to the most concentrated solution. The water passes through the semi-permeable membrane to bring the two solutions to the same osmotic pressure. That’s why when we bathe in the sea our fingers become wrinkled: our cells have thrown out water to try to get the most out of it. dilute the sea. Physiology does not always make intelligent choices immediately. However, without dwelling too much on physical laws and surroundings.
When we talk about osmosis in boats we mean something simple, but not very pleasant: the absorption of seawater by fiberglass. This happens when air bubbles have been left in the fiberglass at the time of lamination. These bubbles are filled with water and the process goes on indefinitely. As a result, these spaces swell and propagate, causing the hull to weaken. The consequence of osmosis is therefore an increase in moisture in the boat.
While you have the boat on the reservoir, check the hull to prevent osmosis. To understand if your boat also suffers from it, check with a specialist technician the state of the hull once winged. It often has small swellings of a few millimetres in diameter with a rough surface that, with the passage of time, increase in size until it breaks the outer layer of the gelcoat. The most used instrument to obtain an initial analysis of the hull is the hygrometer, which allows you to measure the moisture level of the hull. Leaving the boat dry will reduce the value but you will not have found the solution to the problem. If the osmosis stains are concentrated and the analyses define them as surface stains, you can act with power tools that remove the surface gelcoat evenly, without altering the lines of the hull.