Aluminium boat warning

Press, 19 August 1982, Page 4

Aluminium boat warning

PA Wellington The Ministry of Transport has issued a set of instructions to marine surveyors in an effort to prevent cracking which has shown up in a number of 5m to 6m aluminium boats.

The Ministry’s director of marine, Mr Hugh Jones, said the cracking had occurred in six boats.

It was caused by two factors — the use of aluminium sheet with a relatively high magnesium content combined with the use of intermittent (rather than continuous) welds when stiffeners were attached to the plating. Mr Jones said welding could stress the plating and when a highly stressed piece of metal was right next to an unstressed piece cracks

could start.

Surveyors had been told to check plating before use. If it had a high magnesium content that plate should not be used or else they should insist that continuous welds were used on stiffeners. The boats where the cracks had been detected were either catamarans used for fishing or other decked craft They had all been fitted with relatively powerful engines which set up vibration stress, and one or two had been roughly handled with daily launching from a trailer. Mr Jones said there was no. problem with dinghies and other small aluminium pleasure craft. He was certain this form of cracking was not responsi-

ble for the recent Kapiti boating tragedy in which five persons drowned.

“That boat had been looked at several months before and cracks had been fixed. The cause of that sinking was the loss of a loose inspection hatch.”

Mr Jones said the new instructions to surveyors apElied only to boats being uilt for commercial use.

Pleasure boats had never been subject to survey requirements. For prospective pleasure boat owners it was a case of let the buyer beware..

“If they don't know what to look for they should get advice from a surveyor,” said Mr Jones,