Glossary
Yachting Glossary
Browse yacht and superyacht terms covering refit, technical systems, class codes, safety, and onboard operations.
| Description | |
|---|---|
| A-60 Rating | An A-60 rating identifies an A-class fire division that has been tested to maintain fire integrity and insulation performance for 60 minutes under the standard fire test. SOLAS-based fire definitions describe A-class divisions as steel or equivalent bulkheads and decks that prevent the passage of smoke and flame to the end of the one-hour standard fire test, with temperature rise on the unexposed side limited within set values; the A-60 class corresponds to 60 minutes. The FTP Code is the fire-test framework used to verify those properties. |
| Abrasive Blasting | Mechanical surface cleaning using grit to remove old paint/rust and create profile. |
| Access Control System | Electronic system managing doors/permissions, often integrated with CCTV and alarms. |
| Adhesion Test | Test that verifies coating bond strength to the substrate and between layers. |
| Advance Provisioning Allowance (APA) | Advance fund paid by charterer to cover variable operating costs during charter. |
| AFFF Foam System | An AFFF foam system is a firefighting system that uses aqueous film-forming foam concentrate mixed with water to produce foam for flammable-liquid fire protection. IMO foam guidance defines aqueous film-forming foam concentrate as a mixture based on hydrocarbon and fluorinated surface active agents, and the FSS Code framework treats foam concentrates, proportioning, discharge equipment, compatibility, testing, and sampling as integral parts of the system rather than separate accessories. |
| Aft Deck | Exterior area at the stern used for dining and boarding; refits often enhance furniture, lighting, and access to water. |
| Air Draft | Air draft is the vertical distance from the waterline to the highest fixed point of a yacht. That highest point may be a masthead, radar arch, antenna mount, dome, funnel, or another permanent structure, depending on the vessel’s design. Some yachts can reduce air draft temporarily by lowering masts or folding certain fittings, but the stated figure usually refers to the normal operating condition. |
| Air Handling Unit (AHU) | Within a yacht HVAC installation, an Air Handling Unit, or AHU, is the larger air-treatment assembly that takes in air, filters it, heats or cools it through coils, manages airflow with fans and dampers, and then sends conditioned air onward through ductwork. Eurovent describes the AHU as a complex device designed to handle and condition air in HVAC systems, and modern units typically include fans, filters, heat-recovery devices, heating or cooling elements, and controls. |
| AIS | AIS (Automatic Identification System) is a VHF radio transponder system that automatically sends your identity, position, course, speed and status while receiving the same from others. The information rides in structured time slots so many ships can share two AIS channels without talking over one another. Shore stations and traffic services also receive these messages, which is why AIS underpins modern monitoring and port management worldwide. The technical blueprint for this timeslot approach lives in ITU-R Recommendation M.1371. |
| Alarm Monitoring System (AMS) | Central monitoring that aggregates machinery/safety alarms for crew awareness and response. |
| Aluminium Yacht | Lightweight metal yacht often used for performance; galvanic isolation and weld quality are critical in refit planning. |
| Anti-heeling System | System that shifts ballast/fluids to correct list and improve stability during operations. |
| Antifouling Convention (TBT Ban) | The AFS Convention is an IMO treaty that controls the types of coating systems ships may apply below the waterline. It was adopted in 2001 and entered into force in 2008. From that date, Parties to the Convention prohibited applying organotin compounds that act as biocides, and they required ships to either remove legacy TBT or over-coat it with a sealer barrier that prevents leaching. |
| Antifouling Paint Source | Antifouling paint is the underwater coating applied to a yacht’s hull and niche areas to control the attachment of marine organisms. In yacht use, the term usually refers to the final submerged coating system selected to limit slime, weed, and hard fouling during service. Its purpose is functional as much as protective: a cleaner underwater surface preserves speed, efficiency, and handling while reducing the rate at which roughness builds up between dockings. |
| Approval Mapping | In yacht refit and technical project work, approval mapping describes the structured identification of what needs to be reviewed, accepted, or witnessed, by whom, and at what stage. It is a project-control term rather than a formal universal rule term. In superyacht use, it usually means a matrix or coordinated register that links each scope item to the relevant authority or reviewer, such as class, flag, owner’s team, designer, OEM, or surveyor. |
| ARPA | ARPA (Automatic Radar Plotting Aid) is a radar processing function that acquires radar targets, tracks their motion, and calculates key collision metrics. Core outputs include closest point of approach (CPA) and time to closest point of approach (TCPA), along with target course and speed, presented as vectors in either true or relative motion. International performance standards define what a compliant ARPA must do on the display, how many targets it can track, and how the data should be presented for collision assessment. |
| As-Built Drawings | Updated drawings reflecting what was actually installed after modifications. |
| ATA Carnet | Customs document enabling temporary import/export of equipment without paying duties in many countries. |
| Autopilot | An autopilot is a closed loop steering system. It reads a heading or track reference, compares that to a desired setpoint, then moves the rudder via an electric linear drive or a hydraulic pump until the error is minimized. The core blocks are the heading sensor, for example a gyrocompass or satellite compass, the control computer, and the steering actuator. When integrated with a plotter or ECDIS, the same hardware can become a track control system that follows legs between waypoints under defined performance standards. |
| Ballast Water Treatment Source | Ballast water treatment is the onboard process used to manage ballast water so it can be discharged in compliance with the applicable ballast water standard. In yacht context, the term is relevant to larger yachts that actually take up and use ballast water, especially expedition, explorer, and other displacement vessels operating internationally. IMO explains that ballast water is used to maintain safe operating conditions by reducing hull stress, providing transverse stability, improving propulsion and manoeuvrability, and compensating for weight changes during a voyage. |
| Battery Bank | A battery bank is two or more batteries connected together to provide a required voltage, a required capacity, or both. In yacht use, the term usually refers to a grouped DC power source assigned to a function such as engine starting, hotel loads, emergency services, thrusters, or energy storage support. ABYC defines a battery bank as batteries connected in series for higher voltage or in parallel for increased capacity. |
| Beach Club | A stern leisure area at water level, often with fold-down platforms; refits add gyms/spas, improved access, and ventilation. |
| Beam | Beam is the width of a yacht, usually measured at its widest point. In technical documents, the exact basis may be given as maximum beam, moulded beam, or another stated measurement standard. Even small differences in how beam is recorded can matter when a yacht is being compared across drawings, specifications, or operational limits. |
| Bearing Clearance | Bearing clearance is the designed or measured running gap between a shaft, journal, stock, or moving surface and the bearing that supports it. In yacht work, the term appears across main engines, gearboxes, rudder stocks, stern gear, pumps, and other rotating or oscillating machinery. The number itself only makes sense in relation to the specific component, its material, its lubricant, and the maker’s or class requirements. |
| Bilge System | The bilge system collects and removes water that accumulates in the lowest parts of the yacht and provides the pumping arrangement used to dewater compartments when leakage or flooding occurs. In yacht and superyacht use, the term usually covers bilge wells, suctions, strainers, branch lines, the bilge main, non-return and changeover valves, pumps, alarms, and overboard discharge arrangements. It is a safety-critical service system, not a housekeeping convenience. |
| Black Water | Black water is sewage from toilets and associated sanitary systems carried on board the yacht for treatment, retention, or controlled discharge under the applicable rules. In superyacht use, the term is operational rather than statutory wording, but it aligns closely with the sewage controls addressed by MARPOL Annex IV. IMO states that Annex IV regulates sewage discharge from ships and covers the equipment and systems used to control it. |
| Blackout Test | A blackout test is a controlled test of the yacht’s electrical generation and recovery logic after a simulated total loss of main electrical power. On a superyacht, the purpose is to verify that the vessel can recover essential functions safely and in the intended sequence after a full blackout condition. The term belongs to commissioning, trials, periodic testing, and post-refit verification. |
| Blasting (Sa 2.5) | Blasting to Sa 2.5 describes a very thorough abrasive blast-cleaning standard for steel surface preparation before coating. The designation comes from ISO 8501-1, which uses “Sa” for blast-cleaning grades. Sa 2.5 means the surface, when viewed without magnification, is free from visible oil, grease, dirt, mill scale, rust, paint coatings, and foreign matter, with any remaining traces showing only as slight stains in the form of spots or stripes. |
| Blistering | Blistering describes the formation of small raised bubbles or pockets under a yacht’s paint, gelcoat, or outer surface layer. It usually develops when moisture, contamination, trapped solvent, heat, or poor surface preparation breaks the bond between layers. On metal yachts it may point to coating failure and corrosion risk, while on composite hulls it can also suggest deeper moisture-related deterioration. |
| BMS (Battery Management System) | For modern battery-supported yachts, the BMS is the control and monitoring layer that keeps the battery system operating inside safe electrical and thermal limits. IMO’s Future Fuels and Technology project describes a Battery Management System as integrated control and monitoring software that continually ensures the safe operation of a battery propulsion and or storage system on board. |
| BNWAS | BNWAS (The Bridge Navigational Watch Alarm System) is a bridge safety system that verifies the Officer of the Watch is alert, detects incapacity, and automatically calls additional officers if the watch is not acknowledged within set time limits. The technical “how good is good” lives in IMO Resolution MSC.128(75), Performance Standards for BNWAS. The “who must carry it and when it must run” appears in SOLAS Chapter V, Regulation 19, which requires BNWAS that conforms to IMO standards and states it shall be in operation whenever the ship is underway at sea. |
| Bollard / Cleat | Deck fittings used to secure mooring lines safely. |
| Bonding System | The bonding system is the network of conductors that electrically interconnects selected non-current-carrying metal parts of a yacht. In boat and yacht standards, bonding conductors connect metal parts to the vessel’s bonding system so that those parts remain at the same electrical potential. Within yacht practice, that usually includes underwater metals such as through-hull fittings, seacocks, rudder gear components, struts, and other protected metallic items. |
| Boot Top | The painted band around the waterline area, designed for aesthetics and protection. |
| Borescope Inspection | Borescope inspection is the visual examination of internal machinery spaces or components through a small access opening using a flexible or rigid optical scope. In yacht engineering, the term is used mainly for engines, turbochargers, cylinders, valves, and other enclosed machinery areas where condition needs to be checked without full strip-down. It is a condition-assessment method, not a repair in itself. |
| Bosun’s Locker | Crew storage for tools, deck gear, and paint; refits optimize organization and safety. |
| Bow Thruster Source | A bow thruster is an auxiliary manoeuvring device fitted at the bow to generate sideways thrust at low speed. On yachts and superyachts, it is used during docking, undocking, and close-quarters handling where the captain needs direct lateral control at the bow without relying only on propeller wash and rudder effect. Tunnel thrusters are the most familiar arrangement on larger yachts, though other configurations exist. |
| Bridge / Wheelhouse | The navigation control room where the yacht is operated; refits typically focus on integrated navigation/comm systems and ergonomics. |
| Bunker Delivery Note (BDN) | Document provided at bunkering detailing fuel quantity/spec and supplier info; key for compliance records. |
| Capstan | Vertical winch used for mooring lines and handling loads. |
| Carbon Fiber Yacht | Advanced composite construction for high strength-to-weight; repairs require specialist processes and quality control. |
| Catamaran | A catamaran is a vessel with two separate hulls connected by a bridging structure. In yacht use, the term can apply to both sailing and motor designs. The twin-hull arrangement changes the yacht’s proportions, deck layout, and behavior on the water in ways that are very different from a monohull. |
| CCTV System | Onboard camera system for security, situational awareness, and incident review. |
| Chain Locker | Compartment where anchor chain is stowed; requires drainage/ventilation management. |
| Change Order / Variation Order | A formal change to scope/cost/time agreed after the contract is signed. |
| Chase Boat | A chase boat is a fast support craft that operates with a yacht during guest movements, watersports, and daily logistics. On many yachts it functions as a working tender that can move quickly between the main yacht, shore, and activity areas. |
| Chilled Water System | A chilled water system is the yacht’s central cooling network that circulates temperature-controlled water between the chiller plant and the air-side units serving cabins, saloons, bridge spaces, and other conditioned areas. In superyacht HVAC design, the term usually includes the chillers, circulation pumps, distribution pipework, control valves, expansion provisions, coils in AHUs and FCUs, and the control logic that keeps water flow and temperature within design limits. |
| Chiller | A chiller cools water or another secondary fluid so that the yacht’s air-conditioning system can remove heat from interior spaces. On a superyacht, the term usually refers to the central refrigeration machine serving the chilled-water loop rather than a self-contained direct-expansion cabin unit. In larger yachts, that central plant is part of the hotel-services backbone and usually sits in machinery spaces with its own pumps, controls, strainers, and heat-rejection arrangement. |
| CII | Carbon Intensity Indicator measuring operational emissions efficiency; drives rating and improvement actions. |
| Class Approval | Class approval is the formal acceptance by a classification society that a yacht’s design, modification, repair, installation, or test result meets the applicable class rules. In superyacht work, the term usually appears during new build, refit, major equipment replacement, structural repair, machinery changes, or system alterations that affect the classed condition of the vessel. Depending on delegation, some related statutory items may move alongside it, but class approval itself belongs to the class framework. |
| Class Renewal Survey | Periodic in-depth survey required to renew class status (if applicable). |
| Classification Society Source | A classification society is an organization that establishes and applies technical standards for the design, construction, and survey of marine vessels. In yacht and superyacht context, it is usually referred to simply as class. A classed yacht maintains a valid certificate for hull and machinery under the society’s rules, and that status is then maintained through plan approval, surveys, and continuing compliance. |
| Close-Out | In yacht work, close-out is the controlled final stage of a job, package, survey item, or yard period in which the agreed scope is checked, documented, and either accepted, deferred with approval, or kept open for further action. The term is used in refit, repair, class and flag items, warranty work, commissioning punch lists, and onboard defect tracking. In safety-management language, it also covers the follow-up and formal closing of non-conformities and deficiency reports. |
| CMMS | CMMS stands for Computerized Maintenance Management System. In yacht and superyacht use, it means the software platform used to plan, schedule, record, and review maintenance activity across the vessel’s technical assets. In practice, many yacht teams use CMMS language interchangeably with planned-maintenance software, although the exact software scope may also include procurement, defects, spare parts, compliance tasks, and reporting. DNV describes planned-maintenance systems as tools that let operators plan, perform, and document vessel maintenance in line with class and manufacturer requirements. |
| Coating System | The complete paint build-up (primer/epoxy/fairing/topcoat) designed for protection and finish. |
| COLREG | COLREG (International Regulations for Preventing Collisions at Sea) is a treaty-level rule set that tells vessels how to avoid each other, what lights and shapes to show, which sound signals to make, and how to behave in narrow channels and traffic schemes. It applies to all vessels on the high seas and connected waters, from tenders to superyachts and commercial craft. Administrations incorporate it into national law, which is why many mariners also see the rules published in domestic codes. If you hear the term IRPCS, that is simply another name for the same regulations used in some jurisdictions. |
| Commissioning | On a yacht project, commissioning covers the planned process of setting systems to work, checking functions, tuning controls, proving alarms and interlocks, and confirming that installed or modified equipment operates as intended before handover or return to service. In superyacht use, the term applies to new systems and to refit work alike. It sits after installation and before final acceptance, with the focus on performance, safety, integration, and recordable results. |
| Compass Swing | Procedure to determine compass deviation by comparing compass headings to known references and producing a deviation card. |
| Composite Yacht (GRP) | Fiberglass/composite yacht offering corrosion resistance and weight benefits; osmosis and laminate repairs are common. |
| Condition Survey | A detailed survey evaluating hull, machinery, and systems condition, commonly used for valuation, insurance, or refit decisions. |
| Controllable Pitch Propeller (CPP) | A CPP, or controllable pitch propeller, is a propeller system that changes blade angle while the shaft continues to rotate. In yacht terms, that gives the propulsion package another control layer beyond engine speed alone. Thrust, response, manoeuvring behaviour and engine loading are then shaped by pitch position, control logic, hydraulic or mechanical actuation and the condition of the whole propeller package.That makes CPP a propulsion-control topic above a simple propeller topic. Once the system enters refit scope, the job reaches into hub condition, blade mechanism, hydraulic oil route, control response, feedback, shaftline interface, manoeuvring behaviour and the operating proof that shows the pitch system is doing what the yacht expects from it. |
| Corrosion Protection Source | Corrosion protection is the combined set of measures used to prevent or slow the deterioration of metal caused by the marine environment. On yachts and superyachts, that usually means protective coatings, correct surface preparation, cathodic protection where applicable, sound drainage, isolation between incompatible materials, and disciplined maintenance of damaged areas before corrosion spreads. IMO’s protective coating framework and class guidance both treat coatings as a core part of structural protection rather than a cosmetic extra. |
| Crew Area | Accommodation and mess for crew; refits improve durability, ergonomics, and compliance standards. |
| Crew Mess | Dining/lounge area for crew; refits often improve storage, ventilation, and finishes. |
| Critical Path | The sequence of tasks that determines the minimum project duration; delays here delay the whole refit. |
| Cutlass Bearing | A water-lubricated bearing supporting the shaft at the stern tube/strut. |
| Cyber Hardening | Practical steps to reduce attack surface (patching, firewall rules, least privilege, backups). |
| Cybersecurity on Yachts Source | Measures to protect onboard IT/OT systems and connected devices from hacking, malware, data loss, and operational disruption. |
| Davit | Crane-like device for launching tenders, rescue boats, or handling loads. |
| Day Boat | Day boat describes a boat or small yacht intended mainly for daytime use, short coastal cruising, entertaining, and watersports. The design usually prioritises open deck space, easy boarding, and direct access to the water over full overnight accommodation. |
| Deadweight (DWT) | Deadweight, usually abbreviated DWT, is the total weight a vessel can safely carry in addition to its own lightweight structure. It includes variable loads such as fuel, fresh water, provisions, crew, guests, luggage, stores, spare parts, and other consumables carried up to the vessel’s permitted loaded condition. |
| Deep-V Hull | Hull with pronounced V shape for softer ride at speed; sensitive to trim and weight distribution changes. |
| Dehumidification | Moisture control process essential to comfort and preventing mold/condensation damage. |
| Dew Point | Dew point is the temperature at which air becomes saturated enough for moisture to condense on a surface. ASHRAE describes dew-point condition as a measure of absolute humidity determined by cooling air until condensation starts or dew forms on a cold surface. In yacht work, the term appears in two main places: humidity control inside the vessel and environmental control before coating work. |
| DFT (Dry Film Thickness) | DFT means Dry Film Thickness, the measured thickness of a paint or coating layer after it has dried or cured on the substrate. In yacht and superyacht coating work, DFT is one of the main quality-control values for primers, build coats, and finishing systems because protective performance depends on having enough coating on the surface, distributed within the specified tolerance range. ISO 19840 describes DFT verification against nominal dry-film thickness on rough surfaces and ties it to measurement method, inspection areas, and acceptance criteria. |
| Dining Salon | Formal dining area; refits optimize seating, service access, and lighting/acoustics. |
| Displacement Hull | Hull form optimized for efficiency at lower speeds; typical of larger yachts and long-range cruisers. |
| Docking Plan | A docking plan is the drawing or technical instruction set used to show how a yacht is to be supported in dry dock or on a slip. In yacht and superyacht use, it typically identifies keel block positions, side support limits, appendage clearances, restricted support areas, sonar or transducer precautions, bottom plug locations, and any special assumptions that the yard and dockmaster need before the lift. |
| Doppler Speed Log | A Doppler speed log is an instrument that measures vessel speed by analysing the Doppler shift of acoustic signals reflected from the water column or the seabed. On yachts, it is used to provide speed data for navigation, manoeuvring, and bridge awareness. Depending on the equipment and operating conditions, it may provide speed through the water, speed over the ground, and sometimes distance run as well. |
| Draft | Draft is the vertical distance from the waterline to the lowest point of the hull, keel, or underwater appendage. It shows how deep the yacht extends below the surface and is one of the first dimensions checked for navigation in restricted waters. Depending on the yacht, the controlling point may be the keel, propeller, rudder, stabilizer, or another fixed underwater feature. |
| Dry Docking Source | Dry docking is the process of taking a yacht out of the water and supporting it in a dry dock or on a slip so the underwater body and related systems can be inspected, maintained, repaired, or modified. In superyacht use, the term covers both the physical docking event and the planned yard period built around it. It is the standard window for work that cannot be completed safely or effectively afloat. |
| DX HVAC | Direct-expansion air-conditioning using refrigerant at fan coils; common on smaller/older yachts vs chilled water. |
| Dynamic Balancing | Dynamic balancing is the correction of unbalance in a rotating component by considering both the amount of unbalance and where it sits along the rotor. ISO 1940-1 describes two-plane dynamic balancing as the balancing method used when a rotor cannot be treated as a simple disc-shaped item suitable for single-plane balancing. In yacht and superyacht work, the term is used for rotors, impellers, fans, motor armatures, turbocharger parts, and other rotating assemblies where vibration control matters. |
| Dynamic Positioning (DP) | Dynamic Positioning, usually shortened to DP, is a computer-controlled system that keeps a vessel on a fixed position and heading by automatically using its thrusters and propellers. Instead of relying on an anchor or mooring line, the vessel continuously corrects for wind, current, and sea movement. |
| ECDIS | ECDIS stands for Electronic Chart Display and Information System. In simple terms, it is a digital navigation solution that has replaced paper charts on most commercial and private vessels. But ECDIS is more than a digital map. It is a powerful system that combines real-time position data, navigational warnings, and safety features into one central platform. For yachting professionals and management companies, this technology has reshaped how voyages are planned and executed. |
| Echo Sounder | An echo sounder is a depth-measuring instrument that sends a sound pulse downward and calculates water depth from the return echo off the seabed. On yachts, it is used to monitor under-keel clearance during pilotage, coastal navigation, anchoring, and movement in shallow or poorly forgiving waters. The reading may be shown as depth below the transducer, below the keel, or below the waterline, depending on how the system is set up. |
| EEBD | EEBD full form is Emergency Escape Breathing Device. It is a compact, portable breathing apparatus designed specifically for emergency situations where the atmosphere has become hazardous. Unlike full firefighting breathing gear, which is intended for entering and operating in dangerous areas, an EEBD is purely for escape. Its purpose is straightforward: to provide a short but reliable supply of breathable air, allowing the user to evacuate safely.Typically, an EEBD consists of a small compressed air cylinder or chemical oxygen source, a regulator, and a hood or mouthpiece with nose clip. Once activated, it supplies air for a limited duration, usually 10 to 15 minutes, which is generally enough to reach an area of safety or muster station. |
| EEXI | Energy Efficiency Existing Ship Index; technical efficiency metric requiring certain ships to meet targets. |
| Electric Propulsion | Electric propulsion uses an electric motor to create propulsive shaft power or thrust instead of relying on a direct mechanical drive from an internal-combustion engine to the propeller. In yacht and superyacht use, the term can cover shaft motors, podded drives, and other arrangements where propulsion is electrically driven. It describes the propulsion method, not the energy source behind it. Electrical propulsion can be supplied by generators, batteries, shore-charged storage, fuel cells, or mixed configurations. |
| Emission Control Area (ECA) | Geographic zones with stricter emission limits (sulphur/NOx) affecting fuel and operations. |
| ENC | Electronic Navigational Chart used in ECDIS; official vector chart data for safe navigation. |
| Energy Storage System (ESS) | An Energy Storage System, or ESS, is the complete onboard package used to store electrical energy and release it in a controlled way when the yacht needs it. In current yacht and superyacht work, ESS usually means a battery-based installation rather than a loose collection of cells. Maritime guidance commonly treats the ESS as a system-level arrangement with dedicated safety, control, and installation requirements rather than as a single component. |
| Engine Overhaul Source | Engine overhaul is intrusive maintenance in which a yacht’s main engine or generator engine is opened up, inspected, measured, and rebuilt to restore condition within acceptable limits. In yacht use, the term usually sits well above routine servicing. It can involve a top-end overhaul, a major overhaul, or a full rebuild, depending on the engine type, hours, condition trends, and the owner’s maintenance strategy. OEM guidance treats overhaul intervals as running-hour based and condition-sensitive rather than universal. |
| Engine Room | Machinery space for engines and major auxiliaries; refits include overhauls, upgrades, and fire safety systems. |
| EPIRB | An EPIRB, or Emergency Position Indicating Radio Beacon, is a specialized maritime safety device designed to send a distress signal when activated. Its job is simple but critical: alert rescue authorities that a vessel is in trouble, while providing the vessel’s exact location. Unlike standard communication equipment, which relies on manual operation and good conditions, an EPIRB transmits via satellite networks monitored globally. That means even in the middle of the ocean, far outside cellular or VHF range, the beacon can still call for help. |
| Explorer Yacht | An explorer yacht is a yacht designed for extended cruising, strong autonomy, and practical operation over longer distances and in more demanding environments. The type is commonly associated with robust construction, high storage capacity, serious tender-carrying ability, and layouts that support time away from major marina infrastructure. |
| Fairing Source | Fairing is the process of shaping and smoothing a yacht’s surface so the hull, superstructure, or repaired area follows the intended lines without visible hollows, highs, or abrupt transitions. In superyacht work, the term usually refers to substrate correction carried out before primer and topcoat, using fillers and repeated surface checking to achieve a visually even and technically controlled finish. On underwater areas, fairing also contributes to a smoother hydrodynamic surface. |
| Fairlead | Deck fitting guiding mooring lines to reduce chafe and control lead angles. |
| Fan Coil Unit (FCU) | An Air Handling Unit is not the same thing as a Fan Coil Unit, and on yachts the distinction is practical. A Fan Coil Unit, or FCU, is the smaller local terminal unit that uses a fan to move room air across a heating or cooling coil and condition the specific space it serves. Manufacturer guidance describes the unit as a fan passing air over a heating and cooling coil, with the coil supplied by a chilled-water system for individual-room air-conditioning duty. |
| FAT (Factory Acceptance Test) | Pre-delivery testing at the manufacturer to confirm equipment meets requirements. |
| FDHF (Fast Displacement Hull Form) | Fast Displacement Hull Form, commonly shortened to FDHF, is a hull concept intended to combine the efficiency and comfort of a displacement-oriented yacht with the ability to run at higher speeds than a conventional displacement hull. In yacht use, it is meant to widen the efficient operating envelope instead of optimizing the vessel for only one narrow speed band. |
| Feather Edge | Tapered edge sanding to blend repaired areas into surrounding paint smoothly. |
| Fender | Protective buffer used during berthing to prevent hull and structure damage. |
| Fire Damper | A fire damper is a device installed in a ventilation duct that normally remains open for airflow and closes during a fire to restrict the passage of fire through the duct. The current Red Ensign Group Yacht Code defines it in those terms and distinguishes automatic, manual, and remotely operated fire dampers by the way they close and are controlled. |
| Fire Main | The fire main is the fixed water-distribution line that carries firefighting water from the yacht’s fire pumps to hydrants and hose stations around the vessel. In yacht use, the term normally includes the main pipe run, branches, isolating valves, hydrants, hose connections, and the arrangement that allows the required jets of water to be produced where a fire might occur. |
| Fire Pump | The fire pump supplies the water pressure and flow needed for the yacht’s fire main and hydrants. On a superyacht, the term usually refers to the main power-driven fire pump and, where required, the additional independent or emergency fire pump arrangement that allows firefighting water to remain available if one space or one power source is lost. |
| Fixed CO₂ System | Total flooding suppression system for machinery spaces requiring strict safety procedures. |
| Fixed Pitch Propeller | Propeller with constant blade pitch; simpler and efficient at design point but less flexible than CPP. |
| Flag State | The flag state is the national administration under whose flag a yacht is registered. In yacht and superyacht use, it is the statutory authority tied to the vessel’s legal nationality, registry status, and core compliance framework. Its role may be exercised directly by the administration or through delegated organizations, depending on the yacht, the registry, and the certificate involved. |
| Flybridge | An upper deck with helm and seating, popular for views and outdoor living; refits often upgrade electronics, shading, and furniture. |
| Flybridge Yacht | A motor yacht with an upper helm and lounge area on the flybridge, offering better visibility and outdoor living space. |
| FM200 | A clean-agent fire suppression system using HFC-227ea (FM-200) for rapid extinguishing in enclosed spaces and machinery rooms. |
| Fold-Down Balcony | Side platform that opens to create extra terrace space; refits require structural checks and watertight integrity. |
| Foredeck / Bow Area | The forward deck used for anchoring and crew operations; refits focus on windlass, deck gear, and safety. |
| Foul-Release Coating | A non-toxic silicone-based system that reduces adhesion of marine growth for easier cleaning. |
| Freeboard | Freeboard is the vertical distance between the waterline and the deck edge or assigned freeboard deck line at the ship’s side. In practical yacht terms, it is the visible height of the hull above the water. The amount of freeboard changes the way a yacht sits in the sea and how much reserve buoyancy remains as load increases. |
| FSS Code | The FSS Code (International Fire Safety Systems Code) was adopted by the IMO's (International Maritime Organization) Maritime Safety Committee (MSC) via Resolution MSC.98(73). It sets detailed engineering specifications for fire detection, alarms, fixed gas systems, water mist and sprinklers, foam, emergency fire pumps, hydrants and hoses, means of escape arrangements, and more. If a component or system is “FSS compliant,” it has met uniform international performance and testing requirements, not just a manufacturer's brochure promise. |
| Fuel Polishing System Source | A filtration and water-separation system that cleans fuel to remove particulates, sludge, and water, reducing engine and injector issues. |
| Full-Displacement Hull | Displacement hull designed for continuous low-speed efficiency; ideal for range and comfort-focused refits. |
| Galley | Professional kitchen for guest service; refits address workflow, refrigeration, extraction, and safety. |
| Galvanic Isolator | A device that reduces galvanic corrosion caused by shore power ground connections. |
| Gearbox (Reduction Gear) | A transmission that reduces engine RPM to suitable propeller RPM and transfers torque. |
| Generator Room | Space housing generators and switchgear; refits address noise control, load management, and exhaust systems. |
| GMDSS | GMDSS stands for the Global Maritime Distress and Safety System is a coordinated framework that connects ships, satellites, coast stations, and Rescue Coordination Centers so that a distress alert from your yacht actually triggers help, not just hope. In simple terms, GMDSS ties together equipment, procedures, and shore infrastructure so a mayday reaches the right people fast, your position is known, and nearby vessels are alerted to assist. The International Maritime Organization (IMO) built GMDSS into the SOLAS convention, which is why commercial ships must carry it. Pleasure yachts are often exempt from SOLAS, yet the principles and many devices are directly relevant to safe yachting. |
| GNSS | GNSS stands for Global Navigation Satellite System. It is the umbrella term for satellite constellations that provide positioning, navigation and timing data. GPS is one GNSS, but it is not the only one. Galileo, GLONASS, BeiDou and some regional systems also fall under the same broader category. In other words, GPS is a member of the GNSS family, not a synonym for the whole thing.That distinction matters on yachts because modern maritime receivers are often designed as multi-system receivers. IMO performance standards describe shipborne equipment that can use signals from two or more GNSS, with or without augmentation, to provide position, velocity and time data for navigation and other shipboard functions. The practical benefit is straightforward: more available signals, more redundancy, and better resistance to the loss or degradation of a single system. |
| GPS | GPS stands for Global Positioning System, the U.S. satellite navigation system. A GPS receiver calculates position by processing timing signals from satellites and turns that into latitude, longitude, speed over ground, course over ground, and precise time. On yachts, the term "GPS" is often used loosely. Strictly speaking, many modern marine receivers are actually GNSS receivers, meaning they can use more than one satellite constellation such as GPS, Galileo, GLONASS, or BeiDou. The distinction matters because a modern multi-constellation receiver usually gives better availability and resilience than a receiver relying on GPS alone. It also helps to separate GPS from the screen it feeds. The GPS receiver is not the chart display itself. A chartplotter or ECDIS uses position data from the receiver, combines it with charts and other sensor inputs, and presents the result to the bridge team. |
| Grease Trap | Separator preventing fats/oils from entering wastewater systems, reducing blockages and odour issues. |
| Grey Water | Wastewater from showers/sinks; managed separately from black water in many systems. |
| Gross Tonnage (GT) | Gross Tonnage (GT) is a measure of the internal volume of a vessel, not its weight. It is calculated using a formula that considers the total enclosed spaces of the yacht, from the hull to the superstructure, and includes areas like cabins, salons, engine rooms, and technical spaces.Unlike displacement, which refers to how much water a yacht displaces (and thus is related to weight), GT is purely a volumetric measurement. It gives a sense of how much usable or functional space is inside the vessel. |
| Guest Cabins | Accommodation for guests; refits improve layout, bathrooms, HVAC, and noise reduction. |
| Gyrocompass | A gyrocompass is a heading reference that points to true, not magnetic, north. It exploits a continuously driven gyroscope and the rotation of the Earth to align itself with the geographic meridian, remaining immune to magnetic deviation from steel, wiring, or nearby equipment. That north-seeking behavior is achieved by controlled gyroscopic precession using gravity or a pendulous arrangement. |
| Handover Package | The complete set of documents/certificates/tests delivered at the end of the refit. |
| Hard Chine Hull | Hull with sharp chines to improve stability and planing performance; refits may address spray, drag, and handling tweaks. |
| Harmonic Distortion (THD) | Electrical waveform distortion that can cause overheating and equipment issues if unmanaged. |
| Harmonics | Electrical distortion that can overheat equipment and cause nuisance faults. |
| HAT (Harbor Acceptance Test) | In yacht newbuild, refit, and major-system integration work, HAT means Harbor Acceptance Test. It is the structured dockside test stage used to confirm that an installed system is correctly fitted, functional, and ready to move forward before sea trials. OEM HAT procedures describe the purpose in similar terms: verify that the delivered system is correctly installed and fully functional while the vessel is still alongside. |
| Heat Exchanger | A heat exchanger transfers heat between two fluids without requiring those fluids to mix. In yacht engineering, the term covers a wide family of equipment rather than one fixed shape. Coolers, central freshwater coolers, plate exchangers, shell-and-tube units, HVAC exchangers, lube-oil coolers, and domestic hot-water exchangers all fall within the same core idea: controlled heat transfer across a separating surface. |
| Helipad | Certified landing area for helicopters (on some yachts); refits require strict structural, fire, and operational compliance. |
| Hold Point | A hold point is a mandatory checkpoint in a project or inspection sequence where work must stop until the required inspection, verification, or approval has taken place. In yacht refit, repair, coating, fabrication, and equipment-installation work, the term is used inside inspection and test plans, quality-control plans, and approval maps. It belongs to project control more than to marine law, but it has direct technical consequences. |
| Hot Work Permit | A hot work permit is the formal written authorization for work that produces flame, heat, sparks, or other ignition sources in a defined place and for a defined period. In marine safety guidance, hot work is treated as work involving sources of ignition with enough energy to ignite a flammable atmosphere. The permit records that the area, the job, and the controls have been checked before work starts. |
| Hull Thickness Measurement Source | Hull thickness measurement is the gauging of metal structure to determine the remaining thickness of plating or structural members and to identify wastage, corrosion loss, or local damage. In yachting, the term is used mainly on steel and aluminium structure, especially where survey, repair planning, or condition trending is involved. The measurements are usually taken by ultrasonic methods and recorded against original scantlings, allowable diminution, or repair criteria. |
| HVAC Source | HVAC stands for heating, ventilation, and air conditioning. On yachts and superyachts, it refers to the onboard system that controls temperature, air movement, humidity, and fresh-air supply across accommodation, guest spaces, crew areas, bridge spaces, and selected technical compartments. On larger yachts it is both a comfort system and a major hotel-service load. IMO energy-efficiency guidance identifies HVAC as a significant electrical consumer on passenger-oriented ships, which is close to the way it behaves on large yachts with heavy accommodation demand. |
| Hybrid Construction | Combination of materials (e.g., steel hull + aluminium superstructure); interface corrosion and insulation details matter. |
| Hybrid Propulsion | Hybrid propulsion combines mechanical and electrical sources of propulsive power within one yacht propulsion concept. ABB describes hybrid propulsion, in propulsion terms, as a merge of electrical and mechanical sources of rotating energy. In superyacht work, the term usually covers systems that let the yacht run under engine power, electric-motor power, or a coordinated combination depending on the mode selected. |
| Hydraulic Power Pack (HPU) | A hydraulic unit supplying pressurized oil for steering, stabilizers, or deck machinery. |
| Hydrostatic Test | Pressure test using water, commonly applied to certain piping and pressure vessels. |
| ICCP | Impressed Current Cathodic Protection system that uses controlled electrical current to protect metal hulls and appendages from corrosion. |
| ICLL 1966 | International Convention on Load Lines setting minimum freeboard and watertight integrity requirements. |
| IMO | The IMO (International Maritime Organization) is the UN agency that writes the global safety and environmental rules for shipping, including frameworks yachts inherit through flag state and class. If you’ve heard SOLAS or MARPOL, you’ve already seen IMO standards in action. This guide explains what the IMO does, what it regulates, and what yacht owners and refit teams should check first. |
| In-water Survey | Survey performed afloat (where allowed) to reduce downtime; scope is limited and approval-dependent. |
| Inclining Experiment | Stability test measuring lightweight ship characteristics and center of gravity after major changes. |
| Inertial Measurement Unit (IMU) | Sensor package (gyros/accelerometers) providing motion/attitude data for stabilization and navigation systems. |
| Inmarsat | A satellite communications provider offering global voice and data services widely used for maritime connectivity and safety communications. |
| Inverter/Charger | Converts DC to AC and charges batteries, enabling silent modes and backup power. |
| Iridium Certus | Iridium Certus is a mobile satellite service that delivers L-band connectivity with service tiers from compact “midband” devices to broadband terminals. Current maritime plans top out at 704 kbps for download and roughly half that for upload, which is ample for operational apps, voice, messaging, and well-managed guest access. The platform is designed to evolve, so terminals and airtime options continue to expand without changing the global footprint. |
| ISM Code | The ISM (International Safety Management) Code is an international standard that sets out what a company and its ships must do to manage safety and prevent pollution. It was adopted by the IMO, then made mandatory via SOLAS Chapter IX, which means flag states and recognized organizations audit companies and ships against it. For yachts, applicability depends on flag and operation, commercial yachts subject to SOLAS are within scope, while many others adopt an ISM-style Safety Management System because it reduces risk and improves oversight. |
| ISO 8217 | Fuel standard defining marine fuel properties and test requirements to avoid engine damage and disputes. |
| ISPS Code | ISPS (International Ship and Port Facility Security Code) is a security framework issued by the IMO. It standardizes how ships and ports assess risk, raise or lower protective measures, and coordinate during port calls. The Code is risk based, so the depth of measures scales with the threat level set by the government or port. In short, it creates a common language for “who does what, when, and how” across the ship–port interface. |
| ITC 1969 | International Tonnage Convention defining how gross/net tonnage is measured for regulation and fees. |
| ITP (Inspection and Test Plan) | A quality plan listing hold points, inspections, tests, and acceptance criteria. |
| Jacuzzi | Deck-mounted spa; refits often address plumbing, weight, heating, and waterproofing. |
| Jet Ski Dock | Storage/launch solution for personal watercraft, often integrated into beach club. |
| Laser Alignment | Precision alignment method for shafts/couplings using laser measurement tools. |
| Laundry / Laundry Room | Crew operational area for linen/uniforms; refits target machines, ventilation, and noise control. |
| Lazarette | Aft storage/technical compartment near the stern; often houses steering gear, pumps, and spares. |
| Lead Time | The time required to manufacture and deliver equipment; crucial for refit scheduling. |
| Liferaft | Inflatable survival craft used during abandon-ship situations; must be serviced and equipped per requirements. |
| Liquidated Damages | Pre-agreed compensation if completion is delayed beyond contract terms. |
| Lithium Battery (Li-Ion / LiFePO4) | High energy-density battery technology requiring proper safety design and monitoring. |
| LOA (Length Overall) | LOA stands for Length Overall. It is the maximum length of a yacht measured from its foremost fixed point to its aftmost fixed point. In practical terms, it is the full end-to-end length that the vessel occupies. The exact measurement basis can vary slightly depending on the builder, registry, marina, or document standard, especially where removable fittings or appendages are involved. |
| Load Bank Test | Electrical test applying controlled load to verify generator performance and stability. |
| Load Line | A load line, often referred to as the Plimsoll line, is a physical mark painted on the side of a vessel that shows the maximum depth to which it can be safely submerged under different conditions. The position of the line depends on a variety of factors, including:The vessel’s design and stability characteristicsThe type of waters it will operate in (tropical, freshwater, saltwater)The season or expected weather conditionsClassification society and flag state regulations |
| Load Sharing | Generator control feature that balances electrical load among multiple generators. |
| Load Shedding | Automatic disconnection of non-essential loads to protect generators and keep critical systems powered. |
| Load Study | Analysis of electrical loads to size generators, converters, batteries, and cabling. |
| Load Test (Crane/Davit) | Proof test verifying safe working load (SWL) for lifting equipment. |
| Lockout/Tagout (LOTO) | Lockout/Tagout (LOTO) is the isolation method used to prevent machinery, circuits, valves, or other energy sources from being re-energized or reopened while people are working on them. On yachts, LOTO applies to electrical, mechanical, hydraulic, pneumatic, fuel, seawater, and stored-energy hazards. The lock secures the isolation point. The tag identifies who applied it, why the isolation is in place, and what must happen before the system can return to service. |
| Long-Lead Item | Equipment with long lead times that must be ordered early to avoid schedule impact. |
| Long-Range Cruiser | A long-range cruiser is a yacht intended for extended passages with strong emphasis on endurance, fuel economy, seakeeping, and onboard autonomy. The term is used for yachts built to cover substantial distances between ports or fuel stops while remaining comfortable and manageable for life underway. |
| Lower Deck | Deck below the main deck housing cabins, crew, and technical spaces; refits often involve cabins, plumbing, and HVAC distribution. |
| Lower Helm | The primary helm station inside the wheelhouse, designed for all-weather operation. |
| LRIT | LRIT (Long-Range Identification and Tracking) is an IMO defined system under SOLAS regulation V/19-1 that collects a ship’s identity, position and timestamp at long range, then makes that information available to entitled users, such as flag States, port States, coastal States, and search and rescue services. It is built for maritime security, safety, and environmental protection, not for collision avoidance on the bridge. The default reporting interval is four times per day, and administrations can request more frequent transmissions when required. |
| LSA Code | International Life-Saving Appliance Code defining performance and testing standards for lifeboats, life rafts, lifejackets, and related equipment. Adopted by the IMO’s (International Maritime Organization) Maritime Safety Committee through Resolution MSC.48(66), the LSA Code (International Life-Saving Appliance Code) became mandatory via SOLAS (International Convention for the Safety of Life at Sea) Chapter III for ships that must carry life-saving appliances. It sets international standards for everything from lifebuoy lights to lifeboat engines and defines how those items are evaluated and approved. For yacht teams, that means a common language with flag, class and service stations about what “good” looks like for survival craft and personal gear. |
| LWL (Length at Waterline) | LWL stands for Length at Waterline. It is the length of the yacht where the hull meets the water, usually measured at a stated loading condition or at the design waterline. Unlike LOA, it does not describe the yacht’s total physical length. It describes the effective water-contact length of the hull. |
| LY3 | Large Yacht Code (older MCA framework) setting safety and construction standards for certain commercial large yachts. LY3 is the third edition of the Large Commercial Yacht Code developed by the UK Maritime and Coastguard Agency (MCA). It is a code of practice for commercial-use yachts that are 24 meters and over in load line length, carry no cargo, and carry no more than 12 passengers. Its purpose is to prescribe safety and pollution prevention standards suitable for yachts, using a blend of direct requirements and equivalences to big-ship conventions. |
| Magnetic Compass Deviation | Error in magnetic compass readings caused by onboard magnetic influences; requires correction tables. |
| Main Deck | The principal deck with primary guest areas (salon/dining) and key access routes; refits commonly reconfigure interiors and flow. |
| Main Engine Alignment Source | Precise alignment of engine, gearbox, and shaft line to minimize vibration, bearing wear, and coupling loads. |
| Main Engine Repowering | Replacing main engines with new units to improve reliability, efficiency, emissions compliance, and overall yacht performance. |
| Main Salon | Primary guest lounge usually on the main deck; refits often change layout, lighting, AV, and finishes. |
| Main Switchboard | The main switchboard is the yacht’s central electrical distribution and control board supplied directly by the main source of electrical power. Class rule language describes it as the switchboard intended to distribute and control electrical energy for the ship’s services. In superyacht terms, it is the main hub through which generated power is combined, protected, monitored, and sent onward to propulsion support loads, hotel services, auxiliaries, and downstream distribution boards. |
| Man Overboard Device | A MOB (Man Overboard Device) device is a wearable alerting and locating unit that lives on a lifejacket or foul-weather gear. When activated, it sends an electronic distress alert and a continuous position update so the nearest capable receiver can see and home to the casualty. Today’s devices fall into three families, each with different reach and responsibilities. |
| Marine Sanitation Device (MSD) | A Marine Sanitation Device, or MSD, is equipment designed to prevent the discharge of untreated sewage from a vessel. The term is especially tied to United States regulatory usage. The U.S. Coast Guard states that MSD regulations in 33 CFR Part 159 govern the design, construction, and certification of equipment that prevents discharge of untreated sewage from vessels into U.S. waters. |
| Marine Survey Source | A marine survey is a professional inspection and assessment of a yacht’s condition, compliance, systems, or value, depending on the purpose of the assignment. In superyacht use, the term can cover pre-purchase surveys, condition surveys, damage surveys, class and statutory survey support, insurance-related inspections, and technical baseline surveys before refit or major repair. IMO describes surveys and verifications as the mechanism by which ships are checked so relevant certificates can be issued and compliance maintained. |
| MARPOL | MARPOL is the International Convention for the Prevention of Pollution from Ships, adopted by the IMO and recognized worldwide. It is built as one convention with six technical Annexes that target different pollution sources: oil, noxious liquids in bulk, harmful substances in packaged form, sewage, garbage, and air emissions. Think of it as the global baseline that follows your yacht from Monaco to the Maldives, regardless of flag or itinerary. For the authoritative overview, see the IMO’s MARPOL convention page, which lists all six Annexes and their scope. |
| Mast / Radar Arch | Structure carrying antennas, radars, lights, and sometimes satcom domes; refits address weight, cabling, and corrosion. |
| Megayacht | A megayacht is a very large (often 60m+) luxury yacht at the upper end of the private-yacht market. The term is widely used in media, brokerage, and industry conversation, but it does not have one single universal threshold that applies in every context. In practical use, it usually points to yachts that sit above the ordinary superyacht range in scale, complexity, and onboard capability. |
| Megger Test Source | An insulation resistance test using a megohmmeter to assess electrical cable/equipment integrity and detect moisture or degradation. |
| Method Statement | A step-by-step plan describing how a task will be executed safely and to specification. |
| Milestone | A key project checkpoint (e.g., docking, blasting complete, launch, sea trial) used to measure progress. |
| MLC | MLC stands for Maritime Labour Convention, a global agreement developed by the International Labour Organization (ILO). It’s often described as the "seafarers' bill of rights." Its purpose is to ensure fair and safe working conditions for people working at sea including those on commercial yachts. |
| Mooring Winch | Winch designed to tension and control mooring lines during docking operations. |
| Motor Sailor (MS) | A yacht designed to cruise efficiently under power and sail, typically with a substantial superstructure and long-range systems. |
| Motor Yacht | A motor yacht is a yacht powered primarily by engines for propulsion. The term covers a wide range of private and commercial-style leisure vessels, from compact cruising yachts to very large luxury yachts with guest and crew accommodation. What makes it a motor yacht is the reliance on mechanical propulsion as the main means of movement. |
| Muster List | Posted list assigning emergency duties, alarms, and assembly stations for crew and passengers. |
| Muster Station | Designated assembly area during an emergency for headcount and procedures. |
| Naval Architecture Source | Engineering discipline focused on vessel design, stability, structure, hydrodynamics, and overall performance. |
| NAVTEX | NAVTEX, short for NAVigational TEleX, is an automated broadcast service that delivers navigational warnings, meteorological warnings and forecasts, search and rescue information, and other urgent updates to ships in coastal areas. It is a core element of the Worldwide Navigational Warning Service and a major component of the GMDSS system used on seagoing vessels. In the regulatory world, the IMO (International Maritime Organization) treats NAVTEX as a primary coastal delivery method for Maritime Safety Information, and carriage capability is addressed in SOLAS for certain classes of vessels. |
| NCR (Non-Conformance Report) | A formal record of work that does not meet spec, requiring corrective action. |
| Net Tonnage (NT) | Net Tonnage, or NT, is an official tonnage figure calculated under the International Convention on Tonnage Measurement of Ships, 1969. It is a formula-based measurement tied to the vessel’s usable earning or cargo-related internal volume, so it is different from weight-based figures such as displacement or deadweight. On private yachts, NT is often much lower than gross tonnage because the vessel usually has limited cargo space. |
| Network Segmentation | Separating networks to reduce cyber risk and prevent failures from propagating across systems. |
| NMEA 0183 | A serial communication standard for marine electronics that transmits navigation data sentences between instruments and displays. |
| NMEA 2000 | NMEA 2000 is a marine networking standard maintained by the National Marine Electronics Association. It rides on CAN bus, the same proven technology used in automotive and industrial control, and defines how marine devices announce themselves, share data, and recover gracefully when something is unplugged or added. The international equivalent is IEC 61162-3, which adopts NMEA 2000 for carriage on regulated vessels. These attributes are why N2K shows up on everything from tenders to commercial tonnage. |
| Noise Survey | Measurement of onboard noise levels to verify comfort targets and compliance requirements. |
| Non-Destructive Testing (NDT) Source | Inspection methods such as ultrasonic, dye penetrant, magnetic particle, or radiography to detect defects without damaging parts. |
| Novec 1230 | A clean-agent fire suppression system using Novec 1230 to extinguish fires with minimal residue and reduced equipment damage. |
| NOx Tier III | IMO nitrogen oxide emission standard requiring advanced controls in designated areas for new engines. |
| NTP Time Sync | Network Time Protocol used to keep onboard systems and logs aligned to a consistent time source. |
| NVH (Noise, Vibration, Harshness) | Comfort/performance discipline focused on minimizing noise and vibration. |
| O&M Manuals | Operation and maintenance manuals provided at handover for systems and equipment. |
| Oil Analysis | Laboratory analysis of lubricants to detect wear metals, contamination, and early failure indicators. |
| Oily Water Separator (OWS) | Treats oily bilge water to meet discharge limits where permitted by regulations. |
| Open Yacht | A motor yacht with a low-profile superstructure and large open outdoor areas; often sportier and faster than enclosed designs. |
| Orange Peel | Uneven textured finish caused by spray technique, viscosity, or curing conditions. |
| Osmosis Treatment Source | Repair process for fiberglass osmosis involving drying, grinding, re-lamination, and barrier coating to prevent blistering. |
| Owner’s Representative Source | Person/team acting for the owner to manage scope, quality, schedule, and costs during refit. |
| Owner’s Suite | The owner’s private accommodation; refits often upgrade bathrooms, sound insulation, and climate control. |
| PA/GA | Public Address / General Alarm system used for announcements and emergency alerts throughout the yacht. |
| Pantry | Service area supporting dining and cabins; refits focus on storage, appliances, and service routes. |
| Paris MoU | The Paris Memorandum of Understanding, a regional agreement coordinating Port State Control inspections and enforcement among members. |
| Passarelle | Boarding gangway system for shore access; refits improve reliability, controls, and stowage. |
| Passenger Yacht Code | The Passenger Yacht Code is a set of international standards, recognized by the Red Ensign Group, for pleasure yachts that carry more than 12 and not more than 36 passengers and do not carry cargo. Since 2019 PYC has been folded into the REG Yacht Code Part B, with a consolidated July 2024 edition now current. This framework is an IMO-accepted equivalence to passenger ship rules, allowing a yacht to meet the same safety outcomes without being treated like a cruise ship. |
| Permit to Work | Permit to Work is the formal authorization process used to control hazardous, non-routine, or interacting work on board a yacht or during a yard period. In superyacht operations it sits inside the vessel’s safety management system, the yard’s control-of-work regime, or both. The permit does not replace competence or supervision. It records that the work has been defined, the risks reviewed, the controls agreed, and the job released by the responsible person before it starts. |
| Pinholes | Tiny holes in coatings that can lead to corrosion; detected by inspection/holiday tests. |
| PLB (Personal Locator Beacon) | A Personal Locator Beacon (PLB) is a compact, handheld emergency device designed to transmit a distress signal when activated. Its main purpose is to send your exact location to rescue authorities via satellite, even in the most remote areas where no phone signal exists. Think of it as your last line of communication when everything else fails. Unlike regular radios or phones, a PLB connects directly with international search and rescue systems. When triggered, it transmits a signal to the Cospas-Sarsat satellite network, which relays your location to the nearest rescue coordination center. Authorities can then mobilize a response team to your position. |
| PLC | Programmable Logic Controller used for automation and monitoring of onboard systems. |
| Pocket Explorer | A pocket explorer is a compact explorer-style yacht designed to deliver long-range cruising capability, autonomy, and practical expedition features in a smaller size bracket. The term is a market and design label rather than a formal class rule, and it usually points to a yacht that aims for explorer functionality without the scale of a larger expedition vessel. |
| Pod Drive | A steerable propulsion unit integrating propeller and electric/mechanical drive for efficiency and maneuverability. |
| Power Factor | Measure of electrical efficiency; poor power factor increases current draw and losses. |
| Power Management System (PMS) | Automatically controls generators and load sharing to maintain stable power supply. |
| Pre-Purchase Survey | A condition assessment performed before buying a yacht to identify defects, risks, and costs. |
| Pressure Test | A test to verify piping/tanks can withstand specified pressure without leaks or deformation. |
| Primer | The first coating layer that provides adhesion and corrosion protection. |
| Propeller Cavitation | Formation of vapor bubbles on prop blades causing noise, vibration, and surface erosion. |
| Propeller Polishing | Propeller polishing is the cleaning and surface finishing of an uncoated propeller to remove slime, light marine growth, oxidation, and surface roughness that reduce efficiency. In yacht maintenance, it is usually carried out underwater by divers or with specialist in-water cleaning equipment, though it may also be done during docking. The aim is to restore a smooth working surface without altering the propeller’s designed geometry. |
| Propulsion System Source | The complete set of machinery that drives the yacht, including engines, gearboxes, shafts, propellers/pods, and controls. |
| PSC (Port State Control) Source | Inspection regime by coastal states to verify visiting ships comply with international conventions on safety, security, and pollution prevention. |
| PTI (Power Take-In) | A drivetrain arrangement where an electric motor can drive the shaft line (often via gearbox) to provide hybrid or electric propulsion. |
| PTO (Power Take-Off) Source | A mechanical interface transferring engine or gearbox power to auxiliary equipment such as generators, pumps, or hydraulics. |
| Pump Room | Compartment for fluid systems (bilge, ballast, fuel transfer); refits improve redundancy, valves, and monitoring. |
| Punch List / Snag List | A list of defects or incomplete items to be closed before final handover. |
| Purchase Order (PO) | A contractual order issued to a supplier specifying items, pricing, and delivery terms. |
| Pyrotechnics | Distress flares/rockets used for visual signaling; storage, expiry, and handling are tightly controlled. |
| Radar | Radar, short for radio detection and ranging, transmits radio pulses, then measures the time it takes for the echoes to return. From that, the set calculates range, uses antenna angle for bearing, and paints targets on a plan-position display. Because it generates its own energy, radar works in darkness and poor visibility, and unlike AIS it detects non-cooperative targets like unlit craft or flotsam. COLREG Rule 7 explicitly calls for the proper use of radar, if fitted and operational, as part of determining risk of collision. |
| Redressor Source | A tool or repair process used to straighten and re-align bent shafts, propeller components, or structural members during maintenance. |
| Refit Brief Source | A scope and specification document defining objectives, budget, timeline, and technical requirements for a refit project. |
| REG Yacht Code | The Red Ensign Group Yacht Code, a compliance framework used by several flag states for commercial and large yacht safety standards. |
| Retrofit | In yachting, retrofit describes the upgrade, replacement, or addition of equipment, systems, or structural elements to an existing yacht rather than to a vessel still in build. The term usually covers work beyond routine maintenance. It can involve navigation and hotel systems, machinery, propulsion support equipment, stabilizers, emissions-related upgrades, interior changes, or wider technical modernization. |
| RFI (Request for Information) | A formal question to clarify drawings/specifications before proceeding. |
| RFQ (Request for Quotation) | A formal request sent to suppliers/contractors to price a defined scope or item. |
| RIB (Rigid Inflatable Boat) | Tender with rigid hull and inflatable tubes; valued for stability and safety, often upgraded for electronics and seating. |
| Round Bilge Hull | Smooth curved hull common on displacement yachts; refits focus on efficiency, comfort, and noise/vibration control. |
| ROV Inspection | Underwater inspection performed with a remotely operated vehicle to assess hull, appendages, and submerged structures without divers. |
| Rudder Bearing | A rudder bearing supports the rudder stock and helps the rudder turn smoothly while carrying steering loads from the blade into the hull structure. Depending on the yacht’s arrangement, there may be upper and lower bearings, carrier elements, bushings, or pintle-related bearing surfaces. On superyachts, the term is used in a straightforward mechanical sense: it is one of the key load-bearing parts of the steering arrangement. |
| Rudder Drop | Removal/lowering of rudder for inspection of bearings, stock, and seals. |
| Rudder Stock | The main rudder shaft; critical for steering integrity and structural safety. |
| Runs / Sags | Paint drips due to over-application or incorrect viscosity and spray settings. |
| S-100 | Next-generation IHO framework enabling richer digital maritime data (new ENC products, overlays, dynamic layers). |
| S-57 | IHO standard data format historically used for ENC distribution and structure. |
| S-63 | IHO data protection scheme for encrypted/secure ENC distribution and licensing. |
| S-band Radar | S-band radar is a marine radar that operates in the S frequency band, typically around 3 GHz. On yachts, it is used to detect land, large vessels, rain cells, and other targets at medium and longer ranges. Its longer wavelength helps it keep a more stable picture in rain, spray, and sea clutter, which is why it is especially useful on larger yachts making offshore passages. |
| Sacrificial Anode | A replaceable anode that corrodes preferentially to protect underwater metals from galvanic corrosion. |
| Safety Drills | Planned crew exercises (fire, abandon ship, MOB) to verify readiness and meet safety management requirements. |
| Sailing Yacht | A sailing yacht is a yacht designed to be propelled mainly by sails, with an auxiliary engine used for maneuvering, harbor work, and periods without suitable wind. The term applies across a wide spectrum, from smaller private cruisers to large performance yachts and sailing superyachts. The sail plan, rig type, and hull balance are central to the way the yacht performs. |
| SART | Search and Rescue Transponder that responds to radar signals to help rescuers locate a vessel or survival craft during an emergency. |
| SAT (Site Acceptance Test) | Onboard testing after installation to verify correct operation in real conditions. |
| Satellite Compass | A heading sensor that derives true heading from GNSS antennas, often used as a gyro backup or on smaller vessels. |
| SCBA | Self-Contained Breathing Apparatus providing compressed air for emergency response in smoke or oxygen-deficient environments. |
| Scope of Work (SOW) | The defined scope describing exactly what will be done during the refit, including boundaries and deliverables. |
| Sea Chest | A sea chest is a recessed intake space built into the hull below the waterline that collects seawater before it is led into onboard systems. On yachts and superyachts, sea chests feed services such as engine cooling, generator cooling, air-conditioning seawater circuits, fire main suction, and other seawater-dependent equipment. The arrangement usually includes shell openings, gratings, internal piping connections, isolation valves, and sometimes marine growth prevention equipment. |
| Sea Margin | Power allowance for real-world conditions (fouling, waves, wind) beyond calm-water predictions. |
| Sea Trial Source | Operational testing at sea to verify performance, handling, systems functionality, and noise/vibration after build or refit. |
| Seacock | A valve on a through-hull fitting that can shut off seawater flow for safety and maintenance. |
| SEEMP | Ship Energy Efficiency Management Plan outlining operational measures to improve energy efficiency. |
| Selective Catalytic Reduction (SCR) | Exhaust aftertreatment using urea/DEF to reduce NOx emissions (Tier III compliance). |
| Semi-Displacement Hull | Displacement-based hull allowing higher speeds; performance gains often come from prop optimization and weight control. |
| Sewage Treatment Plant (STP) | System treating sewage to permitted discharge standards where allowed. |
| Shadow Vessel | A shadow vessel is a separate support vessel that travels with or near a yacht to carry equipment, crew, supplies, and operational capacity that the main yacht does not want to keep onboard. In superyacht use, it functions as an extension of the primary vessel rather than as the main guest platform. |
| Shaft Alignment Source | Alignment of shafting and bearings to reduce vibration, prevent seal/bearing damage, and optimize drivetrain efficiency. |
| Shaft Seal | A sealing system preventing seawater ingress where the shaft exits the hull. |
| Shaftline | Within a shaft-driven yacht’s propulsion train, the shaftline is the assembly that transmits power from the main engine and gearbox to the propeller. In superyacht use, the term usually covers the shaft or shafts themselves, couplings, bearings, stern tube arrangement, seals, and supporting elements such as brackets or struts, depending on the vessel’s configuration. It is a propulsion and mechanical alignment term, not a generic label for the whole engine room. |
| Shell Door | Large side opening for tender garage/beach club access; refits must address sealing, interlocks, and classification requirements. |
| Shore Power Converter (Frequency Converter) | Converts shore supply (50/60 Hz) to match yacht electrical requirements. |
| Shore Transformer Source | An isolation/shore power transformer that adapts voltage and provides galvanic isolation when connecting a yacht to shore power. |
| Side Boarding Door | Boarding access door on the yacht’s side; refits ensure sealing, lighting, and safe steps/handrails. |
| Sky Lounge | Upper deck lounge with panoramic views; refits often integrate AV/IT and improved glazing/shading. |
| Snagging | Identifying minor defects/incomplete items near project completion. |
| SOLAS | SOLAS stands for the International Convention for the Safety of Life at Sea, developed by the IMO (International Maritime Organization). It is a living set of rules that governments adopt, then enforce through their flag administrations and recognized organizations such as classification societies. SOLAS is organized into chapters covering construction, fire protection, lifesaving appliances, radio communications, navigation, cargo handling, and more. |
| Spares & Consumables List | A recommended inventory of spare parts and consumables for reliable operations post-refit. |
| Sportfisher | A high-performance yacht built for offshore fishing, usually with an open cockpit, outriggers, and fast transit speeds. |
| Spot Repair | Localized repair to a damaged coating area without repainting the full panel. |
| Stabilizer Source | A roll-reduction system (fin, gyro, or other) that improves comfort and safety by minimizing yacht motion in waves. |
| Starlink Maritime | Starlink Maritime is a mobility service that provides high-speed, low-latency internet on the ocean through purpose-built hardware and Global Priority data plans. Current Starlink materials describe the Performance Kit as capable of up to 400+ Mbps under favorable conditions, with plan evolution promised through software and network upgrades. Typical user documentation also notes that latency on oceans can be higher than on land due to the network path, which matters when planning real-time applications. |
| Statutory Survey | Mandatory survey for regulatory certificates (safety, pollution prevention, etc.). |
| STCW | STCW stands for the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers. Adopted by the IMO in 1978 and amended several times, it establishes minimum training and certification requirements for seafarers serving on seagoing ships, including commercial yachts. The Convention sets the legal framework, while the STCW Code contains the technical detail, such as competency tables, sea-service requirements, and revalidation intervals. |
| Steel Renewal | Steel renewal is the replacement of wasted, damaged, cracked, or otherwise unacceptable steel structure in a steel yacht or superyacht. The work may involve shell plating, deck plating, tank boundaries, bulkheads, stiffeners, floors, girders, inserts around openings, or local foundations. In yacht use, the term usually points to structural repair rather than cosmetic metalwork. |
| Steel Yacht | Yacht built primarily in steel, durable and common for large yachts; corrosion protection and coating systems are key refit items. |
| Steering Gear | The hydraulic/electric machinery that moves the rudder(s) according to helm commands. |
| Stern Thruster | A transverse propulsion unit at the stern that provides lateral thrust to assist maneuvering, especially during docking. |
| Stern Tube Seal | At the aft end of a shaft-driven yacht, the stern tube seal is the sealing arrangement around the propeller shaft where it passes through the hull. Its job is to control the boundary between seawater and the stern tube system, keeping water out of the hull and, on oil-lubricated arrangements, keeping lubricant contained. On larger yachts it sits within the wider shaftline and stern tube assembly rather than as a stand-alone component. |
| Strainer (Sea Strainer) | A filter at seawater intakes that prevents debris from entering pumps and heat exchangers. |
| Stray Current Corrosion | Rapid corrosion caused by unintended electrical currents leaking into seawater. |
| Stripe Coat | Extra coating applied to edges/welds/high-risk areas to reduce early breakdown and corrosion. |
| Sun Deck | The highest open deck used for lounging, often with jacuzzi/bar; refits target layouts, shading, and lightweight structures. |
| Superyacht Source | A large luxury yacht (commonly 24m+), typically professionally crewed and equipped with advanced systems and custom accommodation. |
| Surface Preparation | Cleaning and profiling of surfaces to ensure coating adhesion and durability. |
| Surface Profile | The roughness pattern after blasting that helps coatings adhere correctly. |
| SVDR | Simplified Voyage Data Recorder with reduced data set/capacity compared to full VDR, used on certain vessel categories. |
| Swim Platform | The aft platform for water access and tender boarding; refits upgrade lifts, teak, and safety rails. |
| Synchronization | Matching voltage/frequency/phase before connecting a generator to the electrical bus. |
| Tank Deck | A low deck area dedicated to tanks and technical equipment; critical for stability and service access. |
| Technical Space | Dedicated areas for pumps, electrical panels, and system modules; refits focus on access, labeling, and reliability. |
| Technical Specification | A detailed document stating technical requirements, standards, and acceptance criteria for each work item. |
| Tender | Small boat carried by a yacht for shore transfers and water sports; refits include outboard/inboard service and davit integration. |
| Tender Garage | Storage bay for tenders and water toys; refits optimize handling gear, drainage, ventilation, and fire safety. |
| Tender Lift | Mechanism for launching/recovering tenders; maintenance and certification are key. |
| Thermography (IR Survey) | Infrared inspection used to detect overheating in electrical/mechanical systems. |
| Through-Hull Fitting | A hull penetration for seawater intake/discharge; must be correctly installed and bonded where required. |
| Thrust Bearing | Bearing designed to absorb axial propeller thrust loads and protect gearbox/engine. |
| Tie-Coat | An intermediate coating layer used to bond incompatible paint systems (e.g., epoxy to antifouling). |
| Topcoat | The final visible paint layer providing UV resistance, gloss, and color stability. |
| Toy Garage | Dedicated storage for water toys with ventilation, drainage, and securing points. |
| Transom Door | Aft door providing access to swim platform or beach club; refits focus on watertight integrity and mechanisms. |
| Trawler Yacht | A trawler yacht is a private motor yacht inspired by the proportions and practicality of commercial trawlers, but designed for leisure use rather than fishing work. The type is widely associated with fuel-efficient cruising, comfortable accommodation, and steady passagemaking, especially for owners who value range and livability over very high speed. |
| Trimaran | Three-hull vessel for speed and stability; structural connections and weight control are critical in refit work. |
| Underwriting Survey | A survey requested by insurers to assess risk and set coverage conditions. |
| Upper Deck | A deck above the main deck (varies by yacht), often containing lounges, owner spaces, or exterior terraces. |
| Upper Helm | A secondary steering position (often on flybridge) for docking and coastal cruising. |
| UPS (Uninterruptible Power Supply) | Battery-backed power that keeps critical systems running during short outages. |
| UTG Mapping | Systematic ultrasonic thickness gauging mapped over areas to identify wastage patterns and plan steel renewals. |
| UWILD | Underwater Inspection In Lieu of Drydocking, allowing approved underwater surveys to replace some drydock inspections when permitted. |
| VDR | VDR stands for Voyage Data Recorder. It is an onboard recording system that stores selected bridge, navigation, and alarm data so the sequence of events before an incident can be reviewed later. On larger yachts and commercially operated vessels, it supports incident investigation, safety review, and operational accountability. |
| VFD (Variable Frequency Drive) | Controls motor speed efficiently (pumps, fans) and reduces inrush currents. |
| VHF | Very High Frequency marine radio used for short-range ship-to-ship and ship-to-shore communications, including DSC distress and calling. VHF (Very High Frequency) refers to radio frequencies from 30 to 300 MHz, and the maritime service occupies a dedicated slice between 156 and 174 MHz. Within this band, equipment is channelized, standardized internationally, and optimized for short, prompt transmissions that are easy to copy over engine noise and weather. The result is a communication system that is simple to learn, robust in coastal conditions, and interoperable across flags and ports.For yachts, marine VHF equipment enables ship to ship and ship to shore calling, routine traffic, safety coordination, and regulated distress procedures. Two channels define the core: Channel 16 at 156.8 MHz for distress, safety, and calling, and Channel 70 at 156.525 MHz reserved exclusively for DSC (Digital Selective Calling) digital alerts and selective calling. The division keeps critical signaling separate from voice so important traffic can be handled without clutter. |
| Vibration Analysis | A diagnostic technique measuring vibration signatures to identify imbalance, misalignment, bearing wear, and other machinery faults. |
| VIP Cabin | High-end guest cabin typically closest to owner standard; refits focus on comfort and storage. |
| VLAN | Virtual LAN used to segment onboard networks (crew/guest/critical systems) for reliability and security. |
| VSAT | VSAT stands for Very Small Aperture Terminal. In simple terms, it is a satellite communication system that uses a small dish antenna, typically mounted on a yacht’s mast or superstructure, to connect with satellites orbiting the Earth. Unlike traditional land-based internet services, VSAT provides coverage far beyond coastal limits, delivering reliable data and voice connections even in remote waters.The “very small” part refers to the dish size. On yachts, these antennas are usually between 60 cm and 1.2 m in diameter. While compact compared to massive ground-based satellite dishes, they are powerful enough to maintain a steady connection with satellites thousands of kilometers above. |
| Wastage | Material loss due to corrosion, measured to decide steel renewals. |
| Water Mist System | Fine water droplet suppression system effective for machinery spaces with reduced water damage. |
| Waterjet Propulsion | A propulsion method using a high-velocity water jet for thrust; offers maneuverability and shallow draft options. |
| Watermaker | A desalination system (reverse osmosis) that produces fresh water from seawater for onboard domestic and technical use. |
| Watertight Bulkhead | Structural wall designed to prevent flooding spread; refits must preserve penetrations and certification. |
| Watertight Door | Door designed to maintain compartment integrity; refits ensure correct operation, seals, and alarms/interlocks. |
| Windlass | Machinery used to raise/lower anchors and chain. |
| Work Breakdown Structure (WBS) | A structured breakdown of the refit into manageable tasks for planning, costing, and tracking. |
| X-band Radar | X-band radar is a marine radar operating in the X frequency band, usually around 9.4 GHz. It is common on yachts because it provides sharper target definition and better short-range detail than S-band radar. That makes it particularly useful for coastal navigation, harbour approaches, buoy identification, and tracking smaller targets near the vessel. |
| Yacht | A yacht is a private recreational vessel designed for offshore and coastal voyages, typically featuring dedicated accommodation, domestic utilities, and specialized marine systems. Yachts can be sail driven or motor driven. In practice, the term spans everything from 10–15 m family cruisers to the superyacht segment above 24 m, where professional crew, complex systems, and international regulations become central. |
| Yacht Management Company Source | A provider that manages operations, crew, maintenance, budgets, compliance, and logistics on behalf of yacht owners. |
| Yacht Refit Source | A planned upgrade or renewal of a yacht’s systems, interiors, and structure to improve performance, compliance, and aesthetics. |
| Zero Trust | Security model that assumes no device/network is trusted by default; enforces continuous verification and least privilege. |
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