Unit 24. Surveying Small Craft Systems & Mechanical Installations


Early diesel yachts fitted funnels as a left-over function from the design of the steam yacht where it served as a focal point of the profile. The exhaust from a diesel engine is less voluminous than the coal or oilfired steam boiler, and it has more gas velocity so it would be less of a problem in almost every way. However, just as a boiler would issue sooty smuts that would foul awnings and scrubbed teak decks, so would the diesel engine, particularly on start-up after the pipe-work and silencer had cooled and carbon had deposited on the internal bores.

All exhaust systems will suffer to some extent from the above problems, although there are some serious attempts to minimise the effects, especially in the larger yachts. The author of this unit remembers seeing a drawing of a sail training ship built in the 1930’s in which the dry exhaust was led up the mizzenmast venting at the top. There are many problems associated with this solution such as the heat of the mast through the deck (unless there is a separate pipe inside the mast), corrosion in the mast, paintwork, the need to run all the lines and cables outside the mast.

The author tried a similar solution on an 80’ composite hull, where he used a wet exhaust with a special dewatering silencer and ran the “dried” exhaust up the mast venting out near the lower spreaders. It was not wholly successful as the builders did not line the dewatering silencer as requested, and the exiting exhaust included a very fine spray if it had been completed correctly it would have been a very good solution.

This unit on exhausts will try to help the surveyor identify any serious potential problems, which will need to be mentioned in the report.

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