Doc #58 — Coastal and Inter-Island Shipping

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RECOMMENDED ACTIONS (BY URGENCY)

First month:

1. Designate coastal shipping as a Tier 1 fuel allocation category (Doc #60) — marine diesel for coastal vessels is among the highest-value uses of remaining petroleum, because each litre moves more freight than any land-based alternative⁴
2. Contact all coastal shipping operators and establish current fleet status, fuel stocks, and crew availability
3. Identify all vessels in NZ waters capable of coastal cargo work — commercial coastal fleet, harbour tugs, fishing vessels with cargo capacity, barges
4. Suspend non-essential commercial vessel movements to conserve marine fuel

First 3 months:

5. Establish priority coastal routes and cargo schedules (Section 4)
6. Begin inter-island ferry operations planning — determine fuel allocation for Cook Strait freight service, the single most critical maritime link
7. Inventory port cargo-handling equipment and assess operational status without containerised systems
8. Survey NZ’s sailing vessel fleet for cargo conversion potential

First year:

9. Begin sail-assist retrofit trials on existing coastal vessels (Section 5.2)
10. Establish coastal pilot training programme for new routes and reduced-technology operations
11. Identify sites for regional cargo wharves or landing points to supplement major ports
12. Begin construction of first purpose-built sail cargo vessels (drawing on Doc #13 designs)

Years 2–5:

13. Progressive transition from diesel to sail-assisted, then fully sail-powered, coastal freight
14. Expand the coastal fleet through new construction and conversion
15. Establish a coastal trading schedule with regular runs on priority routes
16. Develop break-bulk cargo handling capability at all operating ports

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ECONOMIC JUSTIFICATION

Coastal shipping is 40–60% more fuel-efficient per tonne-kilometre than road freight.⁵ A coastal vessel carrying 1,000 tonnes between Auckland and Lyttelton displaces 40–50 truck movements consuming roughly 600 litres of diesel each way by road.⁶ The same cargo by sea uses approximately 15,000–25,000 litres total — roughly 15–25 litres per tonne versus 25–40 by road. Under fuel rationing, this efficiency gap is decisive.

Labour: A coastal vessel with a crew of 8–12 moves 500–2,000 tonnes per voyage, completing 30–70 return voyages per year depending on route length and weather delays.⁷ A basic coastal network of 15–25 vessels requires 350–700 total personnel (crew plus shore staff) — far fewer person-years per tonne of freight than the equivalent road transport. Training a coastal mariner takes 1–3 years depending on role; sail handling adds further requirements (Section 6).

Breakeven: There is no traditional breakeven calculation. Without coastal shipping, inter-regional freight progressively collapses as road transport becomes unviable. This is infrastructure that prevents NZ’s regions from being isolated from each other.

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1. NZ’S EXISTING COASTAL SHIPPING

1.1 The commercial coastal fleet

NZ’s commercial coastal shipping industry in the 2020s was small by historical standards, dominated by a handful of operators:

• Pacifica Shipping / Swire Shipping: Operated container and general cargo services between NZ ports.⁸
• Coastal Bulk Shipping: Cement and bulk cargo transport, primarily servicing Golden Bay Cement’s distribution from Portland (Whangarei) to South Island ports.
• Silver Fern Shipping / various small operators: General cargo, project cargo, and niche routes.
• StraitNZ / KiwiRail Interislander / Bluebridge (StraitNZ): Inter-island ferry services across Cook Strait, carrying passengers, vehicles, rail wagons, and freight. Combined capacity of approximately 3,000–4,000 lane metres of freight per day.⁹

The total NZ-flagged or NZ-based coastal cargo fleet (excluding Cook Strait ferries) was likely in the range of 10–20 vessels, carrying an estimated 3–5 million tonnes of domestic cargo per year.¹⁰ This is a small fleet. Most NZ domestic freight moved by road.

1.2 Port infrastructure

NZ has 13 commercial ports distributed along both islands: Auckland and Tauranga (the two largest by volume), Northport (Marsden Point), Napier, New Plymouth, Wellington (CentrePort — also the northern Cook Strait ferry terminal), Nelson, Picton (southern ferry terminal), Lyttelton, Timaru, Port Chalmers (Otago), Bluff (South Port), and Gisborne.¹¹ All have wharves, cargo-handling equipment, and navigational aids. Most are equipped for container and bulk handling with cranes and mechanical equipment dependent on electricity (available under baseline assumptions) and hydraulic fluid and lubricants (finite — Doc #34).

Critical vulnerability: Most NZ ports have been optimised for container handling. Under recovery conditions, container logistics will degrade as containers, handling equipment parts, and truck chassis diminish. Ports will need to revert to break-bulk cargo handling — individual items, pallets, and parcels rather than standardised containers.¹² Performance gap: break-bulk handling is roughly 3–10 times slower per tonne than container handling and requires 5–10 times more labour per tonne moved, but it requires less specialised equipment, and NZ’s ports retain general-purpose cranes capable of break-bulk work.

1.3 Other vessels with coastal cargo potential

Beyond the commercial fleet: NZ’s commercial fishing fleet (~1,200–1,500 registered vessels) includes many suitable for general cargo, particularly on routes serving smaller ports.¹³ Harbour tugs can push or tow barges — the simplest cargo carriers. And NZ has one of the highest per-capita yacht ownership rates in the world, with an estimated 10,000–20,000 sailing yachts.¹⁴ Most are unsuitable for cargo work, but this community represents the largest pool of sailing expertise in the country — critical for the sail transition.

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2. FUEL CONSTRAINTS ON POWERED SHIPPING

2.1 Marine fuel consumption

Coastal cargo vessels typically consume 500–3,000 litres of marine diesel per day at sea, depending on vessel size, speed, and loading.¹⁵ A medium-sized coastal vessel (1,000–2,000 DWT) on a typical NZ coastal run (e.g., Auckland–Lyttelton, approximately 1,100 km by sea, 2–3 days) might consume 3,000–8,000 litres per voyage.

The Cook Strait ferries are the largest single consumers of marine fuel in NZ’s coastal fleet. A modern Cook Strait ferry consumes approximately 10,000–20,000 litres of fuel per return crossing.¹⁶ At 3–4 return crossings per day across the combined ferry fleet, daily Cook Strait fuel consumption is in the range of 30,000–80,000 litres — a substantial draw on NZ’s finite petroleum stocks.

2.2 Fuel allocation priority

Under the fuel allocation model (Doc #60), marine fuel for coastal shipping should be among the highest priorities: it moves more cargo per litre than any land-based alternative, Cook Strait has no non-maritime substitute, and several key routes have no practical road alternative at scale without petroleum.

Total marine fuel demand for a reduced coastal service (10–15 cargo vessels plus Cook Strait ferries at reduced frequency) is estimated at 500,000–1,100,000 litres per week — roughly 1.5–8% of rationed petroleum consumption, moving a disproportionate share of essential freight.¹⁷ This is efficient but not sustainable indefinitely. NZ’s petroleum stocks support powered coastal shipping for months to perhaps 1–2 years, not decades.

2.3 The transition timeline

The powered-to-sail transition is a managed progression, not a sudden switchover. Months 0–6: existing fleet operates on rationed diesel at reduced speeds (slow steaming reduces fuel consumption by 30–40%).¹⁸ Months 6–18: sail-assist retrofits reduce diesel consumption by an estimated 5–30% on suitable vessels, with higher savings possible on routes with reliable beam or following winds.¹⁹ Years 2–5: purpose-built sail cargo vessels enter service (Doc #138); diesel reserved for Cook Strait ferries and routes where sailing is impractical. Years 5+: coastal freight predominantly sail-powered; diesel reserved for emergency use only.

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3. THE COOK STRAIT PROBLEM

3.1 Why Cook Strait is special

Cook Strait separates the North and South Islands by approximately 22 km at its narrowest point. Currents are strong (up to 4–5 knots in spring tides), weather can change rapidly, and the strait funnels westerly winds into powerful gusts.²⁰ It is among the more challenging short-sea crossings in the world.

Cook Strait freight is critical to NZ’s economic unity. The South Island produces a disproportionate share of NZ’s food (particularly dairy, meat, and grain), while the North Island contains roughly 77% of the population.²¹ Under nuclear winter, this imbalance may shift somewhat (South Island agriculture is more affected by cooling), but the fundamental need for inter-island freight remains.

3.2 Current capacity and long-term options

The Interislander and Bluebridge services together provide approximately 6–8 return crossings per day, with combined daily freight capacity of roughly 3,000–4,000 lane metres (equivalent to 150–200 heavy truck loads per direction).²² At reduced service (2–3 returns per day), capacity drops to roughly 1,000–1,500 lane metres, requiring cargo prioritisation.

Long-term options as fuel depletes:

• Continued powered ferry should be maintained as long as petroleum permits — a single crossing moves more freight than a sailing vessel carries in a week
• Barge towing is more fuel-efficient than running a full ferry: a tug consuming 500–1,000 litres can move a barge carrying 500–1,000 tonnes across the strait²³
• Rail barge (flat-decked barge with tracks) could maintain the rail freight link if ferries cease
• Sail freight is feasible but limited by Cook Strait’s strong currents and variable winds — passage times highly variable, tidal timing critical, vessel design must prioritise weatherliness over capacity

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4. PRIORITY ROUTES AND CARGO

4.1 Route prioritisation

Not all coastal routes are equally important. Priority should be based on freight volume, alternative transport availability, and strategic value.

Tier 1 — Critical routes:

• Cook Strait (Wellington–Picton): The inter-island link. No alternative. Highest priority for fuel allocation and eventual sail freight development.
• Auckland–Tauranga: NZ’s two largest ports, connected by a relatively short coastal run (approximately 200 km by sea). Tauranga serves the Bay of Plenty and Waikato agricultural hinterland. Road and rail alternatives exist but depend on fuel and tires.
• Lyttelton–Timaru–Port Chalmers: The South Island east coast route, linking Canterbury, South Canterbury, and Otago. Road and rail alternatives exist but coastal shipping supplements them efficiently.

Tier 2 — Important routes: Auckland–Northport (Northland forestry and fuel terminal); Wellington–Nelson (the top of the South Island is poorly connected by road, particularly since the 2016 Kaikoura earthquake damaged SH1).²⁴ Also New Plymouth–Wellington and Napier–Auckland/Tauranga.

Tier 3 — Regional: Bluff–Lyttelton (Southland, including alumina for Tiwai Point); Gisborne–Napier/Tauranga (Gisborne is among NZ’s most isolated cities by road); and small port services to communities that lose road access.

4.2 Cargo prioritisation

Limited capacity requires prioritisation: Priority 1 — food and agricultural inputs (dairy, meat, grain, seeds, fertiliser); Priority 2 — energy and industrial materials (fuel, steel from Glenbrook, cement from Golden Bay, timber, coal); Priority 3 — medical and essential consumables (pharmaceuticals, printing materials, chemicals); Priority 4 — general freight (important for normalisation as capacity grows).

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5. THE SAIL TRANSITION

5.1 Sail-assist retrofits

The fastest path to reducing fuel consumption in the existing fleet is retrofitting sail-assist systems to powered vessels. Sail-assist does not replace the engine; it supplements it, reducing fuel consumption on suitable routes by an estimated 5–30% depending on wind conditions, route, and sail area, with higher savings possible in favourable conditions.²⁵

Retrofit options: Soft sail rigs (gaff or ketch rig added to an existing hull) are the most feasible for NZ construction. The dependency chain for a soft sail rig includes: radiata pine spars (requiring sawmilling and shaping — available from NZ plantation forestry); harakeke fibre rigging (requiring harvesting, stripping, and rope-laying — Doc #99); canvas sailcloth (requiring either existing stocks or local weaving from cotton, hemp, or flax — Doc #99); steel or bronze fittings (blocks, shackles, chain plates — requiring metalworking capacity and scrap or primary metal); and mast step reinforcement of the existing hull (requiring shipwright skills and structural steel or heavy timber).²⁶ Rigid wing sails or Flettner rotors are more complex and depend on composite materials or steel fabrication beyond basic workshop capability, but any existing units should be deployed. Kite sails (parafoils deployed from the bow) are effective on routes with prevailing following winds and require less hull modification than mast-and-sail systems, but depend on synthetic fabric stocks that are finite and irreplaceable.

Not all vessels are suitable. Bulk carriers with low profiles and strong hulls are the best candidates; top-heavy container vessels are poor candidates. Fishing vessels designed for heavy weather are also good fits.

5.2 Purpose-built sail cargo vessels

Doc #138 addresses vessel design in detail. The key coastal-specific requirements are: shallow draft (to access smaller harbours), flat or moderate deadrise (allowing drying out on tidal flats), large open holds for break-bulk cargo, self-unloading capability (cargo derricks on board), and robust construction for NZ’s exposed coast. Performance gap versus powered vessels: a sail cargo vessel of this class averages 4–7 knots under sail versus 10–12 knots for a powered coastal vessel, making passages 1.5–3 times longer; schedule reliability is lower because passage times depend on weather; and cargo capacity per vessel is roughly 2–10% that of a modern powered coastal freighter.²⁷ The trade-off is that sail vessels require no imported fuel and can be built and maintained from NZ materials indefinitely.

Target vessel class: 15–25 metres LOA, 20–80 tonnes cargo, gaff ketch or schooner rig, crew of 3–6.²⁸ Construction time: 12–24 months per vessel with an experienced team of 4–8 shipwrights.²⁹ Key material dependencies: hull planking and framing from radiata pine or native hardwoods (requiring seasoned timber — 6–12 months drying time unless kiln-dried); copper or bronze fastenings (from scrap recovery or NZ copper stocks — limited); caulking material (oakum or cotton, from existing stocks or harakeke tow); waterproofing (marine paint stocks are finite; alternatives include coal tar or tallow, both inferior in durability); rigging and sails as described in Section 5.1. Building a functional coastal fleet of 20–30 vessels requires a sustained programme over 5–10 years, constrained primarily by the availability of experienced shipwrights and seasoned timber (Docs #140, #143).

5.3 Historical precedent

NZ operated a substantial coastal sailing fleet throughout the 19th century — schooners, ketches, and barques carrying coal, timber, wool, and general cargo between all ports. By the 1880s, NZ had several hundred coastal sailing vessels, typically 15–40 metres, carrying 50–300 tonnes, crewed by 4–12 people.³⁰ NZ’s ports and much of its coastal infrastructure were built to serve this fleet. The operational knowledge was lost as steam and then diesel replaced sail, and will need to be relearned from documentation, historical sources, and practice.

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6. CREW TRAINING

6.1 Existing maritime workforce

NZ’s commercial maritime workforce — masters, mates, engineers, and deckhands holding Maritime NZ certificates of competency — is concentrated in Cook Strait ferries, coastal shipping, harbour operations, and fishing.³¹ The total number is uncertain but probably in the low thousands. This workforce provides core expertise for recovery-era coastal shipping, but most have no experience with sailing vessels, most rely on modern bridge equipment that will eventually fail, and the existing workforce is insufficient for an expanded fleet.

6.2 Training requirements

Immediate (from existing mariners): Celestial navigation refresher (Doc #139, using tables from Docs #10–11); break-bulk cargo handling (loading, stowing, securing non-containerised cargo — standard knowledge a generation ago, now rarely practised); and coastal pilotage for reactivated small harbours not served by current commercial shipping.

Medium-term (new crew training): Basic seamanship and safety for new entrants, using NZ Maritime School and industry training frameworks.³² Sail handling and sail vessel operations — the largest training gap. NZ’s recreational sailing community can provide instructors for basic sailing, but commercial cargo operations under sail require further development.

Long-term (sail cargo specialists): Cargo operations under sail (loading, ballast, stability, and trim affect sailing performance — different from powered vessels). Passage planning using prevailing winds, currents, tidal gates, and seasonal weather patterns. Rig maintenance and replacement using NZ materials (harakeke cordage, radiata pine spars, locally-produced canvas — Docs #103, #140). Note that harakeke cordage has lower tensile strength and poorer UV resistance than synthetic rope; it requires more frequent inspection and replacement, and rigging dimensions must be increased accordingly (Doc #99). Māori navigational traditions — coastal pilotage by landmarks, currents, wave patterns, and bird behaviour, as well as weather forecasting methods developed over centuries of Pacific voyaging — complement European-derived practice and should be integrated into the training programme through partnership with Māori practitioners (Doc #160, §4.5–4.7).³³

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7. PORT ADAPTATION

As the coastal fleet transitions from large powered vessels to smaller sail traders, port operations change. Container handling continues as long as specialised equipment functions (electrical power is available under baseline assumptions; hydraulic fluid and parts are the constraints), but cargo progressively reverts to break-bulk — loaded and unloaded by general-purpose cranes, forklifts, and manual labour.³⁴ This is slower per tonne but requires less specialised equipment, and NZ’s ports all retain general-purpose cranes. Port labour can be drawn from the general workforce reallocation (Doc #145).

The shift to smaller vessels also reactivates NZ’s network of small harbours and historical landing points. Beyond the 13 commercial ports, NZ has dozens of small harbours that historically served the coastal trade — Kaipara, Raglan, Kawhia, Whanganui River, Akaroa, Oamaru, and many others — most retaining basic wharf infrastructure.³⁵ A sail cargo vessel drawing 1–2 metres can access harbours that a modern container ship cannot, extending the maritime network’s reach into regions far from major ports.

Navigation will progressively revert from electronic systems (GPS, radar, AIS) to visual methods supported by physical aids to navigation (lighthouses, beacons, leading marks), the NZ Coastal Pilot (Doc #13), tide tables (Doc #12), and local pilot services.³⁶ Most NZ lighthouses are solar-powered and may continue operating for years. Maintaining physical navigational aids should be a designated responsibility under recovery governance.

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CRITICAL UNCERTAINTIES

Uncertainty	Impact	Mitigation
Actual size and condition of NZ’s coastal vessel fleet	Determines initial capacity	Fleet census as part of Doc #8
Marine fuel stock levels and allocation	Determines how long powered operations continue	Fuel allocation model (Doc #60)
Cook Strait ferry operational life without imported parts	Determines how long high-capacity inter-island service continues	Condition assessment, parts inventory, cannibalization planning
Sail-assist retrofit feasibility for existing vessels	Determines speed of fuel reduction	Trial retrofits on 2–3 vessels
Port crane and equipment operational life	Determines when break-bulk reversion is forced	Parts inventory, maintenance regime
Sail cargo vessel construction rate	Determines when the sail fleet reaches useful size	Depends on boatbuilding workforce (Docs #140, #143, #162)
Nuclear winter effect on wind patterns	May alter prevailing winds that coastal sail routes depend on	Monitor; adapt route planning
Crew training pipeline throughput	Constrains fleet expansion	Start training early; use existing recreational sailing community

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CROSS-REFERENCES

• Doc #8 — National Asset and Skills Census (maritime workforce, vessel inventory)
• Doc #12 — NZ Tide Tables; Doc #13 — NZ Coastal Pilot
• Doc #33 — Tires (road constraint increasing coastal shipping value)
• Doc #34 — Lubricants and Hydraulic Fluids (port equipment constraint)
• Doc #60 — Fuel Allocation (marine diesel allocation)
• Doc #160 — Heritage Skills Preservation and Transmission (traditional maritime knowledge, partnership framework for engaging iwi navigational knowledge)
• Doc #99 — Textile and Fibre Production (sailcloth, harakeke cordage)
• Doc #138 — Sailing Vessel Design
• Doc #139 — Celestial Navigation
• Doc #140 — Shipbuilding and Boatbuilding
• Doc #143 — Trade Training
• Doc #145 — Workforce Reallocation
• Doc #162 — Heritage Skills

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1. McLean, G., “The Southern Octopus: The Rise of a Shipping Empire in the Twentieth Century,” NZ Ships & Marine Society / Wellington Maritime Museum, 1990. The Union Steam Ship Company, founded 1875, operated the largest NZ coastal fleet.↩︎

2. Ministry of Transport, National Freight Demand Study (2017/18). Coastal shipping estimated at approximately 10–15% of domestic freight tonne-kilometres. The dedicated coastal cargo fleet has declined over decades as road transport took market share.↩︎

3. NZ rail network statistics from KiwiRail. The operational network is approximately 3,700–4,000 km, with much of the South Island West Coast and North Island East Coast lines in limited use or mothballed. Track condition varies significantly — main trunk lines are well-maintained; secondary lines less so.↩︎

4. Marine fuel efficiency figures are approximate and vary widely with vessel type, size, speed, and loading. The general principle that sea freight is 3–5 times more fuel-efficient per tonne-kilometre than road freight is well-established in transport economics literature. See McKinnon, A., “Green Logistics,” Kogan Page, 2015, for comparative modal efficiency data.↩︎

5. Marine fuel efficiency figures are approximate and vary widely with vessel type, size, speed, and loading. The general principle that sea freight is 3–5 times more fuel-efficient per tonne-kilometre than road freight is well-established in transport economics literature. See McKinnon, A., “Green Logistics,” Kogan Page, 2015, for comparative modal efficiency data.↩︎

6. A heavy truck on the Auckland–Lyttelton route (approximately 1,050 km by road) at typical consumption of 40–60 litres/100 km consumes roughly 420–630 litres one way, carrying 20–25 tonnes of cargo. Fifty truck-loads to move 1,000 tonnes.↩︎

7. Voyage frequency depends on route length, cargo handling time, and weather delays. A vessel on a 2–3 day Auckland–Lyttelton run with 1–2 days port time could complete approximately 4–6 return voyages per month, or 50–70 per year. Shorter routes allow more voyages; weather delays reduce them.↩︎

8. Pacifica Shipping (a division of the Swire Group) operated coastal container services between NZ ports. The company has undergone various changes; the exact current fleet composition and service status should be verified through the fleet census.↩︎

9. Interislander (KiwiRail) and Bluebridge (StraitNZ) Cook Strait ferry services. Combined fleet of 4–5 vessels (including replacement vessels in various stages of procurement and commissioning as of 2024–2025). Interislander operates the larger vessels; Bluebridge operates two ferries. Combined daily capacity figures are approximate and vary with vessel availability and sailing schedules.↩︎

10. Ministry of Transport, National Freight Demand Study (2017/18). Coastal shipping estimated at approximately 10–15% of domestic freight tonne-kilometres. The dedicated coastal cargo fleet has declined over decades as road transport took market share.↩︎

11. NZ port information from the respective port company websites and the NZ Ports and Harbours chapter in the NZ Official Yearbook (historical editions). Maritime NZ also publishes port safety information. The 13 ports listed are the main commercial ports; NZ has additional smaller ports and harbour facilities.↩︎

12. Break-bulk cargo handling was the standard method at all NZ ports before containerisation arrived in the late 1960s and 1970s. The transition to containers occurred over approximately two decades. Some NZ ports retain general cargo handling capability alongside container operations.↩︎

13. NZ commercial fishing fleet: approximately 1,200–1,500 registered vessels. Fisheries NZ maintains the register. Larger vessels (30–60 metres) have significant cargo capacity.↩︎

14. NZ has approximately 250,000–300,000 recreational boats registered, including an estimated 10,000–20,000 sailing yachts. NZ’s international sailing success (America’s Cup, Volvo Ocean Race) reflects genuine depth of expertise.↩︎

15. Marine fuel consumption varies enormously by vessel size and speed. A 1,000 DWT coastal cargo vessel at 10–12 knots typically consumes 1,000–2,000 litres/day. Smaller vessels (500 DWT) at slower speeds consume 500–1,000 litres/day. Modern efficient designs may be lower; older vessels higher. Figures are indicative.↩︎

16. Cook Strait ferry fuel consumption: modern roll-on/roll-off ferries of 15,000–25,000 GT on the 3–3.5 hour Wellington–Picton crossing consume significant fuel. Exact figures are commercially sensitive but the range of 5,000–10,000 litres per one-way crossing is consistent with published data for similar vessels on similar routes.↩︎

17. NZ’s pre-event daily petroleum consumption was approximately 23–25 million litres (Doc #53). Under rationing (total consumption reduced to 2–5 million litres per day), marine fuel of 70,000–160,000 litres per day represents roughly 1.5–8% of total — a high-value allocation.↩︎

18. Fuel consumption is roughly proportional to the cube of speed. A 20% speed reduction reduces propulsion fuel by ~49% in theory; in practice, fixed loads reduce savings to roughly 30–40%. Slow steaming is the single most effective fuel conservation measure for powered vessels.↩︎

19. Sail-assist fuel savings depend on route, wind conditions, sail area relative to vessel size, and operational profile. Modern trials of rotor sails (Norsepower), rigid wing sails (Oceanbird), and kite sails (Airseas/SkySails) on commercial vessels have demonstrated fuel savings of 5–30% in typical conditions. Higher savings are possible on routes with reliable following or beam winds.↩︎

20. Cook Strait conditions: Carter, L. and Lewis, K., “Variability of the modern sand cover on a tide and storm driven inner shelf, south Wellington, New Zealand,” New Zealand Journal of Geology and Geophysics, 1995. Cook Strait tidal currents can exceed 4 knots at spring tides, with significant tidal rips and overfalls. The strait is exposed to both northwest and southerly weather systems.↩︎

21. NZ population distribution: Stats NZ. Approximately 3.9 million of NZ’s ~5.1 million population (2023) live in the North Island. The South Island has approximately 1.2 million. Canterbury (Christchurch) is the largest South Island urban area.↩︎

22. Interislander (KiwiRail) and Bluebridge (StraitNZ) Cook Strait ferry services. Combined fleet of 4–5 vessels (including replacement vessels in various stages of procurement and commissioning as of 2024–2025). Interislander operates the larger vessels; Bluebridge operates two ferries. Combined daily capacity figures are approximate and vary with vessel availability and sailing schedules.↩︎

23. Tug and barge fuel consumption estimates: a harbour tug of 20–40 metres at moderate power draws 200–500 litres per hour. A Cook Strait crossing of 3–5 hours at towing speed would consume 600–2,500 litres. Barge capacity depends on construction; flat-deck barges of 30–50 metres commonly carry 500–1,500 tonnes. Figures are indicative and depend on sea conditions in Cook Strait, which can require higher power than calm-water towing.↩︎

24. The inland Kaikoura route (State Highway 1 through Kaikoura) was severely damaged by the 2016 Kaikoura earthquake and took years to fully reopen. The alternative Lewis Pass route adds significant distance. A direct Wellington–Nelson sea connection avoids both road routes.↩︎

25. Sail-assist fuel savings depend on route, wind conditions, sail area relative to vessel size, and operational profile. Modern trials of rotor sails (Norsepower), rigid wing sails (Oceanbird), and kite sails (Airseas/SkySails) on commercial vessels have demonstrated fuel savings of 5–30% in typical conditions. Higher savings are possible on routes with reliable following or beam winds.↩︎

26. Sail rig construction dependency chain based on traditional boatbuilding and rigging practice. See Leather, J., “Rig for the Working Sailorman,” Stanford Maritime, 1977, for traditional rig construction methods applicable to retrofit work. Material availability in NZ: radiata pine is abundant; harakeke processing is documented in Doc #99; bronze fittings can be cast from scrap (NZ has small foundry capacity); structural steel for mast steps requires welding or bolting capability available at most NZ ports.↩︎

27. Sail cargo vessel performance and specifications: comparable to 19th-century NZ coastal traders (see [^21]). Speed estimates based on typical gaff-rigged trading vessel performance — Chapelle, H.I., “The American Fishing Schooners,” W.W. Norton, 1973, documents 4–7 knot averages for working sail vessels of similar size. Construction time estimates from the Sail Cargo Alliance and traditional boatbuilding benchmarks; actual times depend heavily on workforce experience and material preparation. Modern powered coastal freighters of 1,000–5,000 DWT carry 10–100 times the cargo of a sail trader in a fraction of the time.↩︎

28. Sail cargo vessel performance and specifications: comparable to 19th-century NZ coastal traders (see [^21]). Speed estimates based on typical gaff-rigged trading vessel performance — Chapelle, H.I., “The American Fishing Schooners,” W.W. Norton, 1973, documents 4–7 knot averages for working sail vessels of similar size. Construction time estimates from the Sail Cargo Alliance and traditional boatbuilding benchmarks; actual times depend heavily on workforce experience and material preparation. Modern powered coastal freighters of 1,000–5,000 DWT carry 10–100 times the cargo of a sail trader in a fraction of the time.↩︎

29. Sail cargo vessel performance and specifications: comparable to 19th-century NZ coastal traders (see [^21]). Speed estimates based on typical gaff-rigged trading vessel performance — Chapelle, H.I., “The American Fishing Schooners,” W.W. Norton, 1973, documents 4–7 knot averages for working sail vessels of similar size. Construction time estimates from the Sail Cargo Alliance and traditional boatbuilding benchmarks; actual times depend heavily on workforce experience and material preparation. Modern powered coastal freighters of 1,000–5,000 DWT carry 10–100 times the cargo of a sail trader in a fraction of the time.↩︎

30. McLintock, A.H. (ed.), “An Encyclopedia of New Zealand,” 1966 (Government Printer). By the 1880s, NZ’s coastal fleet included several hundred sailing and steam vessels.↩︎

31. Maritime NZ (the maritime regulatory authority) administers certificates of competency for commercial seafarers under the Maritime Transport Act 1994 and associated rules. Certificates are issued for various classes of vessel and voyage type.↩︎

32. NZ Maritime School (Te Kura Moana), based in Auckland, is NZ’s primary maritime training institution, now part of NMIT (Nelson Marlborough Institute of Technology). Industry training is also provided through the Primary Industry Training Organisation (now part of Te Pukenga). Maritime training covers navigation, seamanship, engineering, and safety.↩︎

33. Howe, K.R. (ed.), “Vaka Moana: Voyages of the Ancestors,” David Bateman Ltd, 2006. Irwin, G., “The Prehistoric Exploration and Colonisation of the Pacific,” Cambridge University Press, 1992.↩︎

34. Break-bulk cargo handling was the standard method at all NZ ports before containerisation arrived in the late 1960s and 1970s. The transition to containers occurred over approximately two decades. Some NZ ports retain general cargo handling capability alongside container operations.↩︎

35. NZ’s small harbours and historical ports are documented in the NZ Pilot (Admiralty publication) and in regional histories. Many retain basic wharf infrastructure maintained by local councils for recreational use, fishing, or occasional commercial use.↩︎

36. NZ’s navigational aid system is maintained by Maritime NZ. Most lighthouses were automated and solar-powered in the 1980s–1990s. Physical structures are durable if maintained; the transition to visual navigation is primarily a training challenge.↩︎