BY KIM


SKOV-NIELSEN MIIMS


It was during a standard pre- purchase condition survey on a 72’ motor yacht. The vessel was placed ashore on the Friday and I went along to inspect the underwater hull on the Monday – giving her some time to dry out over the weekend.


It is common amongst some boat builders to pass air-conditioning gas through an underwater heat-exchanger array. Usually a couple of pipes in a double-U configuration on the outside of the hull just below waterline on the upright surface.


In this case the heat-exchange function had been deleted some years previously but the piping left in place.


The shipyards all round the Western Med where she was cleaned off and re-anti-fouled on a yearly, or even twice-yearly basis, could not know that the array had been deleted so they still cleaned it diligently every time the boat was lifted.


And in Spain we all know what that means – after initial spray- off, the shipyard workers come along with a box of 12 x 1-litre bottles of Hydrochloric Acid (a.k.a. Agua Fuerte) and start to pour/ spray it all over the props, shafts, rudders and any other underwater metalwork – like the calcified array below. Regardless of cutlass bearings or rudder bearings! And they don’t skimp on the acid – so stand back!


The Report • June 2017 • Issue 80 | 57


<< Concretion on the cooling array


The first sign of trouble was a large bubble which I immediately pierced with my spatula only to see liquid pour out – see picture below.


I sniffed it and tested it but it was not vinegary. It was just sea-water. Great, but not great – seawater in the laminate makes you scratch your head a bit. It really shouldn’t be there. So you go looking further.


So, after receiving the vendor’s permission, I carefully probed the area with my


pocketknife. The laminate, not just the thin gelcoat on the outside but the actual laminate started coming away in great chunks. See below the porous-looking chunks which disintegrated to dust as they dried out over the next 24 hours:


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