Tail Shaft
Aftermost length of the propeller shaft, running through the stern tube to the propeller; subject to bearing wear and torsional fatigue.
In practice
Surveyed at intermediate (5-yearly) and renewal (10-yearly) intervals; condition often determines drydock duration. Modern oil-lubricated stern tubes extend intervals; water-lubricated bearings are mandatory in some jurisdictions.
Regulatory detail & full definition
The tail shaft is the aftermost length of the propeller shafting, running through the stern tube and its bearings to carry the propeller; it is subject to bearing wear, corrosion and torsional fatigue. It is a classification-survey item with mandatory periodic withdrawals for inspection - traditionally around every five years, with the shaft renewed at longer intervals on older designs. Modern oil-lubricated stern tubes with effective seals extend the survey intervals, while water-lubricated rubber bearings are required in some jurisdictions for environmental reasons.
Authoritative source: IACS Unified Requirements ↗
Related
Source: IACS UR M68 (tail shafts); class-society surveying rules
High confidence
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