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On the Water A


s I write this I am pleased to be overlooking the river in the quirky nautically themed apartment owned by local illustrator Paul Barclay – a stay here is a must for visitors to the Dart!


Plug over with… In this issue we cover the subject of Osmosis; from its detec- tion to remedial treatments and its prevention. Osmosis has been a hot subject in the boating press since the


1970’s. GRP (Glass Reinforced Plastic) is almost maintenance free and it is a near perfect boat-building material but it does have this potential flaw that, if not caught in the early stages, can be costly for the boat owner to correct. It can make an otherwise sound vessel un-saleable and even uninsurable. Osmosis is a subject beset by old wives tales and many misconceptions, with every skipper and their crew having an opinion. A vessel’s outer gelcoat surface acts as a barrier against water coming into contact with the GRP but the gelcoat is not fully waterproof. At a molecular level, the gelcoat is semi-permeable, allowing water to pass through the surface and come into contact with the GRP. A new GRP hull will instantly absorb moisture through the gelcoat and this will take place every day whilst the vessel is afloat. This is normal and initially this moisture will pass through the GRP, into the bilge and evaporate. This is a regular cycle and is nothing to worry about. At this stage, it would be an excellent time to protect the hull in the form of ‘Osmosis Protection’. The hull would greatly benefit from an epoxy-coating scheme with previous antifoul coatings removed by way of grit blasting. This process will also open micro pores or air inclusions behind the gelcoat surface. Using marine based epoxy fillers and several coatings/films of underwater epoxy, should prevent osmosis from ever occurring. Correctly applied and fully cured epoxy will provide a better barrier to moisture than almost any gelcoat and can protect the vessel for 10 years or more.


A5 Back Hi-Res.pdf 1 21/11/2011 17:28


Without these coatings, the onset of osmosis is almost inevitable in an older vessel as eventually moisture-absorbing solutes within the GRP resin are drawn together under the influence of incom- ing moisture. This is the start of osmosis. The physical signs of osmosis i.e. the blistering so often seen, may take longer to present itself. Beneath the gelcoat surface small amounts of moisture will be busily breaking down the laminate into its original constituents. Eventually blisters can appear; the breakdown of the laminate and the resulting chemicals will exert great pressure on the gelcoat, therefore forcing the gelcoat to ‘bulge’. In older boats, the most obvious breakdown products will be


Torquay Marina, Torquay, Devon TQ2 5EQ


2011© Google Maps ONE Tel: 01803 292229 info@one-brokerage.com


www.one-brokerage.com TEL: 01803 292239


One Brokerage is a unique Power Boat and Sailing Yacht brokerage service, guiding owners and buyers securely through the complex world of


By Jamie Coombes – One Brokerage


Sunseeker Torquay


acetic and hydrochloric acids. It is these acids that give the osmotic blister fluids their characteristic vinegar smell. Litmus papers can confirm their presence. Remedial osmosis treat- ment and the preferred methods to correct this condition vary in many ways. The GRP will certainly need to be dried. Firstly, the gelcoat must be removed to expose the ‘wet’ GRP – osmosis centres have staff trained to use the ‘Gelplane’. This ‘peels’ the gelcoat leaving an exposed GRP surface. This does not, however, show underlying areas of affected GRP. The GRP will need to be thoroughly cleaned over a period of many days using a commercial high pressure washer. Most vessel hulls will dry naturally. Should this not be the case, use of a HOTVAC ma- chine can force drying as this method heats the hull to around 100 degrees centigrade and, by creating very powerful vacuums, the moisture can be drawn from the GRP. The GRP hull will also post cure.


image by www.osmofix.com C M Y CM MY CY CMY K


www.one-b info@one-brokerage


Once a hull has been successfully dried, applications of


epoxy resins, underwater epoxy fillers and coatings as used in osmosis prevention can soon see the vessel successfully treated and afloat. Should you have a vessel ashore and are in any doubt over its underwater condition, why not call One Brokerage. Whilst we are primarily yacht brokers, our previous experience in this field is extensive, allowing us to advise on the condition of your boat and what remedies need to be taken - if at all – this can be very important when identifying your boat’s resale value and sale appeal, or simply to monitor your boat’s condition. About us… One Brokerage offers power boat and sailing yacht owners & buyers a unique experience and in-depth knowledge of the complex world of buying and selling boats. With over 20 years of experience Tom Wills and Jamie Coombes have unparalleled in depth knowledge of buying and selling power boats and sail- ing yachts and how best to maintain and repair them. Tel 01803 292239 email: info@one-brokerage.com


l o h w Sunseeker Torquay L ONE Where to Find Us


Great Collection of Power & Sailing Yachts


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Tel: 01803 Torquay Marina


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