It is a boat owner’s nightmare. You’re lovingly caressing the hull of your pride and joy when your fingers come across something that should not be there – a blister. Is it osmosis? How do you find out? What do you do? Relax, and let Nick ‘Dr Diagnosis’ Vass, explain all.

If you’re unlucky enough to find bumps marking your hull, it’s very easy to assume the worst. Osmosis is a vastly misunderstood nautical curse word and thanks to modern building techniques and materials, is no longer a common bane of the boater. However, osmosis can still occur in the right circumstances and through becoming a rare condition has become a fearful and taboo like affliction. First bit of advice: don’t panic. Osmosis is seldom crippling and may only require a change of storage options to keep the ailment from advancing. What’s more, not all blisters are osmotic.

Step one: Diagnosis

So what do you do if you find blistering? Firstly, get a boatbuilder or surveyor to take a look and confirm that you have blistering. It may sound unlikely, but occasionally barnacles attach themselves to the hull and get painted with antifouling, giving them the appearance of blisters - this does happen!

If blistering is confirmed, first and foremost, it is always best to seek a professional examination and hear what your options are. Separately, you may also want to start considering storing the boat ashore if you don’t already. In my opinion, it’s best to store a sports boat or RIB out of the water when not being used anyway.  This will reduce build up of fouling on the hull, reduce anode depletion and reduce galvanic corrosion to your metal bits such as propeller, stern drive, outboard leg and seacocks. It will also ensure that the rate of moisture absorbed into the hull is reduced, stemming the progress of any blister. It is also now vital you do not leave your boat in the water over the winter.

New fangled dry stack boat parks, such as the one at Parkstone Bay Marina in Poole (pictured on the next page) are a godsend in regards to keeping a hull dry.  They also allow you to go without antifouling paint at all, so any barnacle will remain just a barnacle…

For the full feature, pick up a copy of the September issue of Sports Boat and RIB magazine. In shops from 22 August.