Operational Guide · Registers & Logbooks

# Dry Dock Scheduling for Sister Ships (Sister Ship Scheduling)

When a series of sister ships enters dry dock months apart from one another, each subsequent entry can benefit from lessons learned from the previous one, if the information is systematically collected and reused.

sister ship sister ships fleet planning repair specification

## Operational Explanation

When a Company manages a series of sister ships, dry dock planning can be organized at fleet level rather than ship by ship: entries are staggered over time, and each subsequent dock cycle reuses the repair specification, survey results and lessons learned from the previous cycle on the same ship series.

A concrete industry example of this practice is staggering across dedicated ship series, where cruise companies plan the dry dock entries of sister ships of the same class months or years apart, allowing the technical department to apply to each subsequent ship what was learned from the previous cycle on the same class.

## Regulatory Reference

There is no dedicated IMO regulatory framework for fleet planning; each ship in the series remains individually subject to its own five-year survey cycle (HSSC) and its own Class requirements, regardless of the staggering planned at fleet level.

## Scope of Application

Every Company managing two or more sister ships (same class, same building shipyard, substantially identical technical specifications), with the technical department/Superintendent responsible for coordinating planning at series level.

## Procedure / How to Complete It

1. Maintain a structured record of work carried out on each ship in the series during each dock cycle, including recurring problems and solutions adopted.
2. Reuse the previous ship's repair specification from the same series as a starting point, adapting it to the specific conditions of the next ship.
3. Stagger the dry dock entries of the ships in the series to avoid overlaps that would concentrate the demand for technical and shipyard resources into a single time window.
4. Negotiate fleet-level contractual conditions with the shipyard when possible, leveraging the repeated volume of work on the same ship series.
5. Standardize the logistics of critical spares common to the series, reducing procurement times for subsequent entries.

## Practical Example

Example: a Company with three sister ships plans dry dock entries 12 months apart from one another; the technical department applies to the second ship the lessons learned from the first ship's dock (a recurring corrosion problem in a specific double-bottom zone), scheduling a targeted preventive intervention that had not initially been included in the original repair specification.

## Real Cases

An industry example of this practice involves a series of sister ships of a cruise company, whose dry dock entries were staggered over several years: the first ship in the series entered dry dock, followed months later by the second and subsequently the third, allowing the technical department to progressively refine the repair specification and logistical planning at each successive cycle on the same ship class.

## Common Mistakes Mistake Library

Mistake | Consequence | How to avoid it
--- | --- | ---
Each ship in the series treated as an isolated case, without systematic reuse of lessons learned from the previous dock cycle on the same class | Known recurring problems on the series rediscovered from scratch at each dock cycle | Maintain a structured record of work and recurring problems for each sister ship series
Dry dock entries of ships in the same series not staggered, with overlapping time windows | Concentration of demand for technical and shipyard resources, with lower negotiating power | Always stagger the dry dock entries of ships in the same series over time
Repair specification developed from scratch for each ship in the series, without reusing the previous ship's as a base | Time and resources wasted reworking information already available from the sister ship | Always reuse the previous ship's repair specification from the series as a starting point

## PSC Observations

Fleet-level planning is not subject to direct PSC verification; each ship in the series remains subject to individual verification of its own certificates and surveys according to its own specific cycle.

## Operational Tips

- Always maintain a structured record of work and recurring problems for each sister ship series: it is the most valuable information asset for subsequent cycles.
- Stagger the dry dock entries of the same series over time: avoid concentrating demand for technical and shipyard resources into a single window.
- Always reuse the previous ship's repair specification from the series as a starting point, adapting it instead of starting from scratch.

## Checklist

- Structured record of work and recurring problems maintained for each sister ship series
- Previous ship's repair specification from the series reused as a starting point
- Dry dock entries of the same series staggered over time
- Fleet-level contractual conditions negotiated with the shipyard when possible
- Logistics of critical spares common to the series standardized

## FAQ

Does each sister ship still have its own individual survey cycle?
Yes: despite coordinated fleet-level planning, each ship in the series remains individually subject to its own five-year survey cycle (HSSC) and its own Class requirements.
Why stagger dry dock entries of sister ships over time?
To avoid concentrating demand for technical and shipyard resources into a single time window, maintaining greater negotiating power and allowing lessons learned from the previous cycle to be applied to each subsequent ship.
What is concretely reused from one dock cycle to another on the same ship series?
The repair specification as a starting point, previous survey results, the record of recurring problems found, and the logistics of critical spares common to the series.
🎬 Additional photos, videos and interactive diagrams for this topic will be available in a future version of the platform.

## Related Topics

Dry Dock Entry Planning Managing Shipyard Repair Contracts

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