Part (a): How osmosis may be detected in service
Osmosis is a process where water diffuses through a semipermeable membrane from a less concentrated solution to a more concentrated one. In the case of GRP hulls, the semipermeable membrane is the gelcoat, and the more concentrated solution is the seawater outside the hull. This can cause the gelcoat to blister and delaminate.
Here are some ways to detect osmosis in service:
- Visual inspection: Look for blisters, cracks, or changes in the color or texture of the gelcoat.
- Tapping: Gently tap on the hull with a mallet or other blunt object. A hollow sound may indicate delamination beneath the surface.
- Moisture meter: Use a moisture meter to measure the moisture content of the hull. This can be a more quantitative way to detect osmosis.
Part (b): Why simply drying out the hull is not a cure for the effects of osmosis
Simply drying out the hull will not cure the effects of osmosis because it does not address the underlying cause of the problem, which is the presence of water trapped within the laminate. Once water has entered the laminate, it can react with the resin and cause it to break down. Even if the hull is dried out, the damage has already been done and the blisters and delamination will likely reappear.
Part (c): The FULL process for the treatment of a hull suffering from the effects of osmosis
The full process for treating a hull suffering from osmosis is a complex one and can vary depending on the severity of the damage. However, here are the general steps involved:
- Cleaning and drying the hull: The hull must be thoroughly cleaned to remove any dirt, grime, or salt deposits. It should then be dried out completely, ideally using a combination of heat and ventilation.
- Grinding: The blisters and any delaminated areas must be ground out to remove the damaged material.
- Neutralizing the acids: The exposed laminate must be neutralized to remove any acidic salts that can cause further damage.
- Filling and fairing: The ground-out areas must be filled with a suitable epoxy filler and faired smooth.
- Re-laminating: A new layer of gelcoat or epoxy resin must be applied to the repaired areas.
- Painting: The hull may need to be repainted to restore its appearance and protect it from further damage.
Part (d): The chemical reaction that occurs during osmosis
The chemical reaction that occurs during osmosis is complex, but it essentially involves the diffusion of water molecules through the gelcoat and into the laminate. The water molecules react with the resin in the laminate, causing it to break down and lose its strength. This can lead to the formation of blisters and delamination.