Osmosis In Yachts


My yacht has osmosis and I don’t know what to do!

Osmosis is understandably an area of concern for second hand boat buyers. But is it the kiss of death? It is important to understand what you are dealing with and how to go about addressing any issues. Today we speak to Tony Hearder, director of one of Australia’s most respected marine surveying companies Marinassess, to find out more:

Can you give us a clear definition of what osmosis actually is?

The definition of the word osmosis is ” the equalization of a solution, by the passage of the solution through a semi permeable membrane”.

Osmosis occurs due to this process, once the moisture enters the GRP Hull it mixes with the uncured chemicals in the layup and the solution thickens up and applies pressure to the surrounding GRP. This pressure splits the laminate making room for more solution to enter which thickens up and this process causes the blisters.

Osmosis BlistersOsmosis_2

When you find a yacht has osmosis during a survey what rectification steps are recommended …is it a one job fixes all, what are the options?

The rectification of osmosis does vary because as you can have very large deep seated blisters and or tiny small ones under the gelcoat and those in between. The blisters do need to be removed by grinding out big blisters individually or shaving the outside skin to remove an entire laminate and or a Mix of both. Each case has to be investigated and have tests done to see why it has occurred so the correct repair can be conducted.

Does Osmosis always need to be treated?

Osmosis usually needs to be removed. In most cases it will continue to develop unless the hull is sealed so that no more moisture can get in to feed the blisters.

What are the risks involved in not treating osmosis?

In the worst case if left untreated it could sink your boat, but this would be an extreme situation.

Is osmosis still a problem in modern yachts?

On modern yachts with the introductions of modern resins and materials the industry is very confident that it will not be a problem on new boats getting Osmosis in the future.

What are the tell tale signs of osmosis and are there any other symptoms often thought incorrectly to be osmosis?

Tell tale signs are blisters appearing in the underwater surface and or High levels of moisture measure on a dry Hull and not measuring the underwater area.

Finally what advice would you give to someone on finding out their potential new yacht has some degree of osmosis?

If your ideal yacht arrives on the market that you are keen to buy and it has osmosis it all depends on the severity and whether it can be repaired. Modern techniques appear to have a good reputation and have a good track record.