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The problem : – One GRP Speedboat moored for 8 months on a UK South coast tidal mooring which dries for around 2 one hour periods in 24.

The unseasonally wet weather has dictated that boat usage was infrequent, perhaps every 3 weeks.  The boat was removed from the water some 2 weeks before the trial and repeated attempts were made to clean the underside of the boat and remove a stubborn covering of barnacle with a “hobby” type pressure washer which suggested an output pressure of 130 bar with little effect.  The underside of the boat has been given a substantial coat of anti foul, but with no effect on the barnacles.

The DOFF was started at 80 Bar and 110 deg C and this had little or no effect.   The pump was turned up to 100 bar and still the effect was disappointing. Temperature was then increased by 10 deg at a time until at 140 deg C things started to happen.   At 100 bar and 150 deg C the barnacles were coming away.

The operator felt that a close 150 deg C pass appeared to “Kill” the barnacle and a further pass literally blew them off.  It was discovered with dwell on the area it became possible to lift the antifoul and return to the gelcoat.  The DOFF was also used to clean the motor leg and it was impressive at reaching into the corners in which barnacles like to hide.

The operator also commented that any barnacles he had missed seemed to have been killed by the heat and were easily removed by use of a disposable plastic picnic knife.  In short the clean was very effective and although it took around 2 hours to clean the underside and motor leg it was far more effective and undamaging than any mechanical removal.

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