Recreational Boat Building & Luxury Yacht Manufacturing HVAC Ductwork — Australian Boat Builder Engineering Guide

Why recreational boat building is its own HVAC discipline

Australian recreational boat manufacturing sits at a difficult intersection of process risks that very few industrial HVAC engineers see in a single plant. A modern luxury motor yacht builder turns out a 60-foot fiberglass hull beside a 70-foot aluminium superstructure beside a carbon composite hardtop, and the same factory floor that just sprayed gelcoat at 0900 is laying up vinyl ester resin at 1100, machining carbon at 1300 and welding aluminium engine beds at 1500. Each of those processes generates a different airborne hazard, and each one of those hazards has a different code — AS 1668.2 for general industrial ventilation, NFPA 33 for spray application, NFPA 484 for combustible composite dust, AS/NZS 60079 for hazardous area classification of resin solvents, AS/NZS 5149 for refrigerant handling on engine fit-out, and ISO 12217 plus AS 5111 governing the small craft itself.

The result is that a recreational boat factory needs HVAC ductwork specified to a standard halfway between aerospace composites and a wet paint booth, with the additional complication that the entire facility usually sits within five kilometres of the coast. Australia's largest production yacht plants — Riviera Group at Coomera in southeast Queensland, Maritimo at Hope Island, Telwater's Quintrex, Stacer and Yellowfin lines all out of Coomera, Whittley Marine at Carrum Downs in Victoria, Cruise Craft at Brisbane, Stejcraft at Wangi Wangi on Lake Macquarie, Stessl at Mackay, Bar Crusher at Bairnsdale, and the Haines, Hammerhead, JC and Sailfish operations clustered along the Gold Coast — are without exception built in marine-atmosphere postcodes. Salt-laden air sweeps directly off the Pacific or Bass Strait, mixes with styrene off-gassing inside the layup halls, and attacks galvanized ductwork in months rather than years.

This guide consolidates the engineering rules that SBKJ uses when scoping ductwork for a boat building plant build, refit or extraction system upgrade. It is opinionated. It assumes you will reject galvanized steel in any zone that touches resin, gelcoat, solvent or coastal air, and that you will specify 316L stainless for those zones with full continuity testing in the carbon trim bays. It is also pragmatic — there are six zones in a boat factory where coated mild steel duct is the right answer and you do not need to pay stainless prices to satisfy the standard.

The Australian boat building industry — who builds what, where, and at what volume

Australian boat manufacturing produces roughly six thousand recreational craft per year across fiberglass, aluminium and composite hulls. The industry has consolidated around a small number of large production yards and a long tail of specialist custom builders, with the largest concentration of plants in southeast Queensland's Gold Coast corridor and a secondary cluster in Victoria's eastern suburbs and Gippsland coast.

Luxury motor yacht — fiberglass production, 50 to 100 feet

Riviera Group at Coomera is by a wide margin Australia's largest builder of luxury motor yachts. The Coomera facility is purpose-built for fiberglass production of vessels from 39 to 78 feet, with a flagship facility footprint that includes dedicated tooling halls, hull and deck lamination bays, gelcoat spray booths, polyurethane finish booths, full electronics integration and a launching basin onto the Coomera River. Their ductwork specification on the lamination bays is the benchmark for production fiberglass in the southern hemisphere — full 316L stainless extract from every operator station, hazardous-area-rated exhaust fans on the resin mixing rooms, and dedicated downdraft booths for gelcoat that are commissioned to NFPA 33 even though the Australian regulator only mandates AS 1668.2.

Maritimo at Hope Island, a few kilometres north of the Riviera plant, builds luxury motor yachts in the same 50 to 75 foot bracket and exports heavily to North America. Their facility shares the same fundamental process flow as Riviera — fiberglass hull and deck lamination, gelcoat application, polyurethane finishing — but with a layout optimised for a higher proportion of one-off and semi-custom hulls rather than pure production volume. The ventilation engineering challenge is identical: keep styrene under 25 ppm in operator breathing zones and prevent any spark source within five metres of an open resin pot.

Riviera Sport Yacht — a sister marque to the main Riviera line — operates from the same Coomera campus and shares overlapping facility infrastructure for layup, paint and electronics, with dedicated tooling for sport-yacht hulls in the 39 to 50 foot bracket.

Mid-size fiberglass production — 18 to 40 feet

Whittley Marine at Carrum Downs in southeast Melbourne is Victoria's largest fiberglass production yard and one of the most respected mid-size brands nationally. The Carrum Downs plant produces fiberglass cruisers from 18 to 30 feet on a continuous-flow layup system, with dedicated bays for hull, deck, hardtop and small-parts lamination. The Victorian coastal location means the same chloride exposure problem you see on the Gold Coast applies here, with the added challenge of cooler ambient temperatures slowing resin cure and increasing styrene off-gas time.

Cruise Craft at Brisbane builds high-quality fiberglass trailer boats in the 17 to 27 foot bracket, with a reputation for fit and finish that is closer to luxury yacht standards than to volume production. Their plant runs a tight downdraft gelcoat operation and a separate finishing booth for two-pack polyurethane on hardtops and graphics.

Stejcraft at Wangi Wangi on Lake Macquarie has been building fiberglass cruisers since the 1960s and is one of the last family-owned production yards on the NSW coast. The Wangi facility is smaller in volume than the Queensland plants but produces craft to a build standard that has aged exceptionally well in the second-hand market.

Sailfish Catamarans on the Gold Coast builds fiberglass power catamarans in the 20 to 32 foot bracket, with a specialist twin-hull layup and bonding process that requires careful management of styrene off-gas inside the tunnel deck during lamination.

Hammerhead Marine at the Gold Coast and JC Boats at Toogoolawah in the Brisbane Valley represent the boutique end of fiberglass production — smaller volumes, higher per-unit content, and a process flow that often blends hand layup with vacuum infusion on the same hull.

Haines Group at Coomera operates as a multi-marque builder including Haines Hunter, Signature and Traveller, with a Coomera facility that handles the full fiberglass production sequence from tooling through to launch on the Coomera River.

Aluminium hull production

Australian aluminium boat building is dominated by Telwater Group, also located at Coomera, which owns and operates the Quintrex, Stacer and Yellowfin marques. Quintrex is the largest aluminium boat brand in the southern hemisphere by unit volume, producing thousands of pressed-aluminium and welded-aluminium hulls per year. The Telwater Coomera facility is essentially a metalworking plant rather than a composite shop — large CNC cutting tables, TIG and MIG welding cells, hydraulic press lines for hull pressing, paint and powder coat lines, and final assembly. The ventilation engineering is closer to a precision sheetmetal shop than a composite plant: source-capture welding hoods at every TIG and MIG station, dedicated extraction at plasma and waterjet cutting tables, and powder coat booth extraction that does not need to meet the same hazardous-area standard as a wet paint booth but does need to handle conductive metal dust.

Stessl Boats at Mackay in north Queensland builds aluminium plate boats for the tropical north — heavy gauge, welded construction, designed for offshore and reef work. The Mackay location means tropical humidity is the dominant HVAC challenge alongside welding fume.

Bar Crusher at Bairnsdale in East Gippsland produces premium aluminium fishing boats for the southern Australian market, with a plant that is sized for medium-volume welded-aluminium production and a typical hull length of 18 to 28 feet.

Sailing yacht and custom

Sayer Designs at the Gold Coast is one of the few Australian builders working at the top of custom carbon racing yacht construction — pre-preg carbon hulls, autoclave cure and full vacuum-bag composite manufacture. The ventilation specification at a facility like Sayer is closer to aerospace than to volume boat building, with cleanroom-grade air handling in the pre-preg layup bays and NFPA 484 deflagration protection on every carbon machining cell.

Adams Yachts in Sydney represents the Australian custom sailing-yacht tradition — design and build of individual cruising and racing yachts from 30 to 80 feet, typically on a per-commission basis and using a mix of fiberglass, wood-epoxy and carbon composite construction depending on the brief.

French production brands Beneteau and Jeanneau dominate the imported sailing yacht segment through Australian dealer networks rather than local manufacture, with rigging, commissioning and refit work performed at Australian-based service yards in Sydney, Melbourne and on the Gold Coast.

Commercial recreational and workboat builders

Birdon Group at Port Macquarie on the NSW mid-north coast builds workboats and naval auxiliary craft for both commercial recreational charter and government fleet operators, with a yard footprint and process flow that overlaps with the smaller naval shipbuilding facilities covered separately in our AUKUS submarine and naval dockyard HVAC guide. Marine Construction Solutions covers the bespoke commercial vessel niche — pilot boats, harbour craft, search-and-rescue platforms — for which the HVAC process is essentially a hybrid of luxury yacht fit-out and small naval auxiliary.

Across the entire industry, the constant is the marine atmosphere. There is no Australian boat plant more than a short transit from saltwater. That single fact drives the corrosion specification for every duct, fan, fastener and damper that goes into a boat building plant HVAC system.

Applicable codes and standards — what the facility engineer must satisfy

An Australian boat building plant sits under a stack of codes that operate concurrently rather than in alternative. The facility engineer must satisfy every one of them simultaneously. The list below is the working set used by SBKJ engineers when scoping a project, with the controlling clauses called out where they matter most.

AS 1668.2 — The use of ventilation and air conditioning in buildings, mechanical ventilation in buildings

AS 1668.2 is the foundational Australian standard for industrial ventilation rates. For a general boat building workshop the baseline is 10 air changes per hour with elevated rates for specific zones. AS 1668.2 also sets the framework for local exhaust ventilation, capture velocities and the principles of source control versus dilution. Every Australian boat plant HVAC commissioning report cites AS 1668.2 air-change calculations as the bottom-line compliance number, and our AS 1668.2 reference guide covers the calculation method in detail.

AS/NZS 60079 — Explosive atmospheres

AS/NZS 60079 is the Australian and New Zealand adoption of the IEC 60079 series and covers everything from hazardous area classification (AS/NZS 60079.10.1) through to equipment selection and installation. For a boat building plant the relevant zones are typically:

• Zone 1 — resin mixing room (continuous expectation of flammable vapour during operations);
• Zone 2 — inside the spray envelope of a gelcoat or paint booth during operation only;
• Zone 2 — within 3 metres of any open polyester resin work station during layup;
• Non-classified with engineered controls — bulk fiberglass layup hall with engineered ventilation maintaining concentrations below 25 percent of the lower explosive limit.

Every fan motor, lighting fixture, sensor and damper actuator inside a classified zone must be certified to AS/NZS 60079 or to an internationally-recognised equivalent (ATEX, IECEx). SBKJ supplies ATEX/IECEx certified fan assemblies for the resin mixing exhaust and the inside of the spray booth envelope, with full certification documents in the commissioning pack.

NFPA 33 — Standard for spray application using flammable or combustible materials

NFPA 33 is the US National Fire Protection Association standard for spray booth design. Australian regulators do not mandate NFPA 33 explicitly, but it is the de facto benchmark for any gelcoat or wet paint booth specified to a build standard that satisfies insurance underwriters and that will hold up under the scrutiny of an international fleet survey. NFPA 33 covers:

• booth construction (non-combustible, no exposed insulation, smooth interior);
• ductwork (continuously welded, non-sparking, no unnecessary obstructions);
• fan construction (spark-resistant wheel, motor outside airstream where vapour concentration may be flammable);
• ventilation rate (typical 0.5 metres per second face velocity at the booth opening);
• fire protection (automatic suppression, interlocked spray gun shutdown).

SBKJ ductwork for gelcoat and paint booths is specified to NFPA 33 as standard, with continuous TIG welding on all longitudinal and transverse seams, no rivets, no sealants on the duct interior, and spark-resistant exhaust fans where the duct sees flammable atmosphere.

NFPA 484 — Standard for combustible metals and metal-like dusts

NFPA 484 applies to combustible metal dusts including aluminium, magnesium and titanium, but also covers carbon fibre composite dust because cured carbon fibre behaves as a metal-like combustible. The relevant zones in a boat plant are:

• aluminium grinding and finishing on the Telwater, Bar Crusher and Stessl floors;
• carbon fibre machining, trimming and sanding at Sayer Designs and any Riviera or Maritimo bay that handles carbon hardtops, masts or appendages;
• any post-cure trimming of carbon-reinforced laminates.

The fundamental NFPA 484 requirements are: bonded conductive ductwork with continuity tested to under 10 ohms across the full run; explosion isolation valves between pick-up and collector; deflagration protection on the collector (explosion vent, chemical suppression or oxygen-deficient operation); wet collection or HEPA dry collection for carbon dust; no plastic ducting; and rigorous housekeeping protocols to prevent secondary dust accumulation.

ISO 12217 — Small craft, stability and buoyancy assessment

ISO 12217 governs the design assessment of small craft stability. It is not directly an HVAC standard, but it interacts with the ventilation engineering on two specific points: first, the placement and mass of fixed HVAC equipment on a vessel affects the centre of gravity calculation; second, ventilation openings and grilles on the hull and superstructure affect the downflooding angle that feeds into the stability calculation. Plant HVAC engineers usually only encounter ISO 12217 indirectly through the design office, but it is worth being aware that the ventilation grille you specify for the engine room may need to be reviewed by the naval architect against the stability envelope.

AS 5111 — Small craft general requirements

AS 5111 is the Australian standard for general requirements of small craft, covering construction, electrical systems, ventilation and habitability. It interacts with the plant HVAC specification at the boundary between the build process and the finished vessel — the same ventilation rate that AS 5111 requires for a finished engine room or fuel locker is the same calculation the plant engineer needs to satisfy when commissioning the on-board AC on the assembly bay.

Volatile organic compound capture — styrene, acetone, MEKP

The single largest air-quality challenge in a recreational boat building plant is volatile organic compound capture. Unsaturated polyester and vinyl ester resin both release styrene monomer as the laminate cures, and styrene release continues for hours after laminate is rolled out and rolled. Tool cleaning uses acetone in industrial quantities. The catalyst for polyester resin is methyl ethyl ketone peroxide (MEKP), which is itself a hazardous material releasing organic peroxide aerosol.

Styrene — the controlling exposure

Styrene is the controlling exposure in a fiberglass shop. Safe Work Australia publishes a workplace exposure standard of 50 parts per million as an eight-hour time-weighted average, with a 100 ppm short-term exposure limit over 15 minutes. The published health basis for the standard includes both neurotoxicity (acute and chronic) and ototoxicity (interaction with industrial noise to increase hearing-loss risk). Practical plant design aims to keep operator breathing-zone concentrations under 25 ppm, providing a 50 percent margin against the regulatory limit.

Achieving 25 ppm operator-zone concentration requires engineered ventilation around every active layup station. The two primary approaches are:

• Cross-draft layup hall — bulk make-up air supplied at one end of the hall, drawn across the working area, and exhausted at the opposite end. Practical face velocity at the operator station is 0.5 to 0.75 metres per second. This approach works for high-bay halls with consistent layout but loses efficiency when work stations are clustered or when the hall layout is complex.
• Downdraft layup table — local downdraft extraction built into the work station itself, drawing styrene vapour downward through a grated floor and into a stainless 316L plenum. This is the preferred approach for any operator-intensive layup work, particularly for hand-layup of complex parts. Practical face velocity at the operator level is 0.5 metres per second downward.

Both approaches require extracted air to be treated before discharge. The three viable treatment technologies in Australia are thermal oxidation (incineration), regenerative thermal oxidation (RTO) for larger plants, and biofiltration where the discharge volume permits. Discharge consent is administered by the relevant state environmental authority — EPA Victoria, NSW EPA, Queensland Department of Environment and Science — and limits are typically set to keep ground-level concentration below 0.2 ppm at the nearest receptor.

Acetone — the housekeeping risk

Acetone is used in industrial quantities for tool cleaning and rolling between coats. It is highly flammable with a flash point of minus 20 degrees Celsius and a lower explosive limit of 2.5 percent by volume in air. The dominant risk is not chronic exposure (acetone has a relatively high exposure standard of 500 ppm TWA) but acute fire and explosion risk from accumulated vapour in poorly ventilated tool wash areas. The engineering control is a dedicated solvent recovery cabinet or a ventilated tool wash sink with at least 0.5 metres per second face velocity at the cabinet opening, exhausted to atmosphere through stainless 316L ductwork.

MEKP — the catalyst aerosol

MEKP catalyst is dispensed through metered pumps directly into the resin pot or chopper-gun catalyst injector. The aerosol generated during catalyst injection is corrosive and toxic, and any operator working near an open catalyst pot must have direct extraction overhead. The engineering control is a small captor hood at the catalyst station, exhausted to a separate ductwork run that does not combine with the main resin exhaust until both have been independently treated. SBKJ supplies the catalyst hood in stainless 316L with a dedicated low-flow fan rated for the corrosive atmosphere.

Process zones in detail — equipment, materials, ductwork

Fiberglass layup hall — hand layup, chopper gun, vacuum infusion

The fiberglass layup hall is the largest single ventilation load in a recreational boat plant. A medium-sized production yard like Whittley or Cruise Craft will run a 2,000 to 3,500 square metre layup hall with continuous operator presence across multiple hulls in progress. The big Riviera and Maritimo hulls require dedicated bays of 1,500 square metres each just for the one hull and one deck.

Three processes operate inside the layup hall:

• Hand layup — operators roll resin and chopped strand or woven roving by hand into an open mould. The slowest process and the highest per-operator styrene exposure. Requires the most aggressive ventilation, typically a downdraft table or floor-level extraction with overhead make-up.
• Chopper gun — handheld spray gun chops continuous-strand glass fibre and atomises catalysed resin onto the mould surface in a single pass. Faster than hand layup but generates substantially more atomised styrene and glass particulate. Operator must be in supplied-air respiratory protection in addition to engineered ventilation.
• Vacuum infusion — dry glass is laid into the mould, sealed under a vacuum bag, and resin drawn through under vacuum. Styrene release is significantly lower than hand layup or chopper gun because the laminate is sealed during cure. Ventilation requirement is reduced to general dilution at the workstation plus dedicated exhaust at the resin pot.

SBKJ ductwork specification for the fiberglass layup hall is full 316L stainless on all extract runs from the operator workstations through to the treatment system. The make-up air ductwork can be coated mild steel because it carries clean tempered air with no styrene contact. Make-up air is tempered to within 2 degrees Celsius of hall ambient to prevent thermal shock on uncured laminate, and humidity is controlled to 50 percent relative humidity to maintain consistent resin viscosity. Hall ambient is held at 20 to 24 degrees Celsius dry bulb depending on the resin system in use.

Resin mixing room — Zone 1 hazardous area

The resin mixing room is the most highly classified hazardous area in the plant. Open polyester or vinyl ester resin sits in mixing pots; styrene monomer make-up is stored in drums; catalyst is dispensed from metered pumps; and the entire room sits within the 50 percent LEL contour during normal operation. AS/NZS 60079.10.1 classifies the room as Zone 1.

Engineering implications:

• All electrical equipment certified Ex d IIB T3 or better;
• Lighting fixtures certified for Zone 1 use;
• Exhaust fan certified ATEX or IECEx, with spark-resistant impeller and motor either outside the airstream or certified Ex d;
• All ductwork bonded and earthed with continuity verified across every joint;
• Stainless 316L construction with continuously welded seams;
• No fan inlet damper inside the room — only a fully-open path from the room to the fan;
• Make-up air supplied through a dedicated supply diffuser at low level to maintain positive sweep through the operator zone, with extract at high level above the resin pots;
• Minimum 12 air changes per hour during operation, increasing to 30 air changes per hour during MEKP catalyst transfer.

The resin mixing room exhaust must be ducted separately from the main layup hall exhaust until both streams are independently treated. Combining the two streams creates a long stretch of duct in which the explosive concentration sits above 50 percent LEL, and any ignition source in that duct propagates back into both the mixing room and the layup hall simultaneously.

Gelcoat spray booth — NFPA 33 downdraft

Gelcoat is the pigmented polyester resin spray that goes onto the mould surface before the structural laminate is applied. It is sprayed at 100 to 150 microns wet thickness and cures to the visible hull surface. The spray booth must satisfy NFPA 33 because the atomised spray contains flammable solvent.

SBKJ specification for a gelcoat downdraft booth:

• Booth shell internal lining stainless 316L or smooth painted steel with no exposed insulation, no rivets, no fasteners protruding into the spray envelope;
• Filter floor at 0.5 metres per second face velocity downward, with cartridge filtration in the floor plenum;
• Side extract from the floor plenum into stainless 316L ductwork rising to the exhaust stack;
• Exhaust fan spark-resistant non-ferrous wheel construction, externally-mounted motor with non-sparking belt drive;
• Stack discharge minimum 3 metres above the highest point of the building roof and 7.5 metres from any air intake or property boundary;
• Tempered make-up air supplied at high level around the perimeter of the booth at 20 to 24 degrees Celsius and within 2 degrees Celsius of booth ambient;
• Automatic spray-gun interlocked shutdown on fan failure or filter blockage;
• Automatic fire suppression to NFPA 33 standard (typically dry chemical or wet chemical).

Why the 2 degrees Celsius temperature match matters: gelcoat is sprayed at room temperature onto a tooled mould that is also at room temperature. If the booth ambient drifts more than 2 degrees Celsius from the mould temperature, the spray fan rapidly cools or heats the gelcoat in flight and creates micro-cratering, orange-peel and tackiness defects that show through the finished hull surface. Temperature stability is a finish-quality requirement, not just a comfort requirement.

Aluminium hull fabrication — TIG and MIG welding

Aluminium hull plants like Telwater Coomera, Stessl Mackay and Bar Crusher Bairnsdale are essentially precision welded fabrication facilities. The dominant ventilation load is welding fume — predominantly aluminium oxide particulate with a fraction of ozone from the welding arc — at every TIG and MIG station.

SBKJ specification for an aluminium fabrication shop:

• Articulated source-capture hood at every welding station, with capture velocity of 0.5 metres per second at the weld point;
• Stainless 304 or coated mild steel ductwork from the hood through to the central collector (full 316L is not required because the atmosphere is dry and chloride exposure is from the building ambient, not from the welding fume itself);
• Central cartridge or bag filter collector with HEPA polishing if discharge is back into the workshop;
• Dedicated downdraft cutting tables for plasma and waterjet, with sub-table extraction directly into the collector;
• Powder coat booth extraction if a powder line is integrated with the aluminium fabrication — this is a dust extraction rather than a flammable-atmosphere booth, so NFPA 484 conductive duct requirements apply to the aluminium powder collector but NFPA 33 does not apply to the powder spray itself;
• Make-up air at 20 air changes per hour minimum during welding operations, tempered to 18 to 22 degrees Celsius for operator comfort and consistent weld behaviour.

Aluminium hull plants do not need the full marine-grade stainless duct specification that fiberglass shops require, because the process itself does not generate corrosive vapour. The coastal atmosphere is still the dominant corrosion driver, so coated mild steel or stainless 304 is the right answer rather than galvanized.

Carbon fibre layup and machining — NFPA 484 conductive dust

Carbon fibre composite manufacture happens at Sayer Designs (custom racing yachts), at any Riviera or Maritimo bay handling carbon hardtops or appendages, and at the small number of Australian builders producing carbon composite small craft. The defining hazard is cured carbon dust, which is electrically conductive and classified under NFPA 484 as a combustible metal-like dust.

The two operational risks are:

• Dust explosion — a sufficient airborne concentration of carbon dust in the presence of an ignition source can deflagrate. Primary ignition sources in a carbon shop are electrical (a short circuit caused by conductive dust bridging across exposed terminals) and frictional (a foreign object in the dust collector inlet);
• Electrical short-circuiting — conductive carbon dust settles on every horizontal surface, including the interior of electrical cabinets, motor terminals and PLC panels. Even at concentrations well below the lower explosive concentration, settled carbon dust shorts out electrical equipment and creates the ignition source for the explosion in the same incident.

SBKJ specification for a carbon machining and trim bay:

• Stainless 316L ductwork with all flanges electrically continuous and continuity tested to under 10 ohms across the full duct run;
• Bonded conductive flooring under the work area, bonded to the duct system and to building earth;
• Explosion isolation valve between pick-up and collector inlet;
• Wet-bath HEPA collector or dry HEPA collector with explosion vent or chemical suppression;
• Sealed electrical cabinets in any room with airborne carbon dust, with cabinet ventilation through filtered intake to keep settled dust off interior terminals;
• Housekeeping protocol: daily wet wipe-down of all horizontal surfaces inside the shop, no compressed air blow-down (which suspends settled dust into the explosive concentration range);
• All compressed-air tools fitted with localised vacuum extraction.

Cure oven and post-cure room — 60 to 80 degrees Celsius

Many composite processes — particularly vinyl ester and epoxy laminates — benefit from a controlled post-cure cycle at 60 to 80 degrees Celsius for 4 to 24 hours. The cure oven or post-cure room is a separate enclosure from the layup hall, with insulated walls, controlled heat input, and dedicated ventilation.

SBKJ specification:

• Stainless 304 ductwork (316L not required because the atmosphere is dry and styrene release is largely complete by the time the laminate enters post-cure);
• Insulated duct construction with high-temperature gaskets at every joint;
• Recirculation loop for energy recovery — typically 80 percent recirculation with 20 percent fresh make-up;
• Direct-fired or indirect-fired heat input depending on building gas service, with combustion vent in stainless 304;
• Pressure relief on the oven envelope to prevent over-pressurisation at thermal expansion;
• Temperature uniformity within plus or minus 2 degrees Celsius across the working envelope, verified by NATA-accredited thermal survey at commissioning.

Polyurethane paint shop — NFPA 33 with isocyanate

Two-pack polyurethane topcoat is sprayed over the cured laminate to deliver the visible finish on premium hulls — particularly on Riviera, Maritimo and Sailfish craft where the gelcoat hull surface is overlaid with a polyurethane scheme for graphics and colour stability. The polyurethane spray contains isocyanate, which is an occupational asthma sensitiser, and the booth specification must combine NFPA 33 flammable-spray protection with operator breathing-air supply.

SBKJ specification:

• Construction identical to the gelcoat booth: stainless 316L lining, continuously welded ductwork, spark-resistant fan, externally-mounted motor, tempered make-up air;
• Operator inside the booth on supplied breathing air — the booth atmosphere is dangerous to operators even with engineered ventilation because the isocyanate threshold is far below the achievable booth concentration;
• HEPA polishing on the exhaust stack to capture isocyanate-containing aerosol before atmospheric discharge;
• Booth interlocked with breathing-air compressor — spray cannot be initiated unless breathing air is flowing to the operator suit.

Trim shop and upholstery

The trim shop handles interior upholstery, headlining, carpet and soft trim. The HVAC challenges are fabric and foam dust at cutting tables, and adhesive VOC at every adhesive spray station. The atmosphere is benign compared to the layup hall, so the ductwork specification is correspondingly less aggressive — coated mild steel is acceptable throughout, with stainless 304 only at the adhesive spray station where solvent contact is direct.

SBKJ specification:

• Local downdraft at every fabric cutting table, with fabric collection in a small cyclone separator before the bag filter;
• Captor hood at every adhesive spray station with stainless 304 ductwork to a dedicated small collector;
• General dilution ventilation at 6 to 8 air changes per hour during normal operation;
• Make-up air tempered to 20 to 22 degrees Celsius for operator comfort and consistent adhesive open-time behaviour.

Engine room fit-out and refrigerant handling

The engine room fit-out bay handles diesel engine commissioning, fuel system pressure testing, and charging of any on-board air-conditioning or refrigeration installed on the vessel. AS/NZS 5149 applies wherever R32, R454B, R134a or any other regulated refrigerant is being charged.

SBKJ specification:

• Diesel exhaust extraction at every engine commissioning station, stainless 304 ductwork from the exhaust manifold capture out to a roof stack;
• Refrigerant leak detection in any area where AS/NZS 5149 applies, with audible and visual alarm and automatic ventilation increase on detection;
• General dilution ventilation at 10 air changes per hour;
• Coated mild steel general ductwork is acceptable; stainless is only required at the engine exhaust capture itself.

Electronics fit-out bay — ESD-safe 22 to 24 degrees Celsius

The electronics fit-out bay installs the navigation, communication, autopilot, entertainment and monitoring systems on the finished hull. The atmosphere is benign — no solvents, no airborne dust other than ambient — so the HVAC specification is closer to a clean assembly area than to a heavy-industrial space.

SBKJ specification:

• 22 to 24 degrees Celsius dry bulb, 45 to 55 percent relative humidity;
• MERV 14 filtration on the supply air to keep dust off exposed electronics during assembly and test;
• ESD-safe construction — bonded conductive flooring, ductwork bonded to building earth, no isolated metal sections that could accumulate static charge;
• PVC-coated mild steel ductwork is acceptable throughout;
• Acoustic NC-45 because the bay shares walls with the design office and customer walk-through areas.

Sea trials preparation area

The sea trials prep area is the final staging area before the vessel is craned into the water. It handles final fit-out touch-up, document handover and customer pre-delivery walk-through. The HVAC challenge is minimal — ambient ventilation at 4 to 6 air changes per hour is sufficient — with localised solvent extraction only at any touch-up station where a small amount of paint, polish or sealant is still being applied.

SBKJ specification: coated mild steel ductwork throughout, general dilution ventilation, no special hazardous-area provisions.

Why galvanized fails — and what to specify instead

Galvanized steel ductwork is the default in commercial HVAC because zinc coating provides reliable corrosion protection in normal building atmospheres for 25 to 40 years. In a recreational boat building plant, the same galvanized duct fails in 18 to 36 months. The failure mechanism is straightforward:

1. Styrene attacks zinc — styrene monomer in low concentrations in air does not directly attack zinc, but the acidic condensation products of partial styrene oxidation form a thin film on the duct interior that increases zinc dissolution rate by an order of magnitude.
2. Acetone removes the zinc passivation layer — acetone aerosol carried in the extract air strips the protective zinc carbonate film that normally limits further attack. Without the passivation layer, the underlying zinc is exposed to continuous oxidation.
3. MEKP aerosol is directly corrosive — organic peroxide aerosol attacks zinc directly and accelerates the loss of coating.
4. Chloride from coastal air attacks the underlying steel — once the zinc is consumed, chloride ion in the marine atmosphere attacks the underlying mild steel through the longitudinal seam, the transverse joints and any rivet penetration. Pitting corrosion develops within months, and a perforated duct cannot be safely operated under the negative pressure of an extract system.

The replacement specification is stainless 316L throughout the layup, resin mixing, gelcoat spray, polyurethane paint and carbon machining zones. 316L is selected over 304 because the molybdenum content of 316L specifically improves chloride pitting resistance, which is the failure mode that matters most on the Australian coast.

For the lower-exposure zones — trim shop, electronics, sea trials prep, general workshop — coated mild steel duct (PVC-coated or epoxy-painted) is acceptable and significantly cheaper than stainless. The discipline is to match the duct specification to the zone exposure rather than over-specifying the whole plant.

Conductive duct, ATEX certification, acoustic NC-50

Three further specification points deserve specific attention.

Conductive duct per NFPA 484 for carbon fibre

Conductive duct in a carbon machining bay means every section of duct is electrically continuous from pick-up through to the collector, with continuity tested to under 10 ohms across the full run. This requires:

• Stainless 316L duct construction (mild steel and aluminium are both adequately conductive, but stainless 316L gives the corrosion resistance for the marine environment alongside the conductivity);
• Bonded flanges using a conductive gasket and bonding strap across every joint;
• Earth bonding straps from every duct support to building earth, with separate bonding from the collector to building earth;
• Continuity testing at commissioning and at 12-month intervals thereafter, with results documented in the maintenance log.

ATEX/IECEx certification for resin zones

Every fan, motor, sensor and damper actuator inside a Zone 1 or Zone 2 hazardous area must be certified to AS/NZS 60079 or to ATEX/IECEx (which AS/NZS 60079 accepts). SBKJ supplies the certification documentation in the commissioning pack, with each piece of equipment tagged with the ATEX or IECEx certificate number and the certifying body. The fan motor manufacturer's data plate must show the Ex protection mode (typically Ex d IIB T3 for resin zones), the gas group and the temperature class.

Acoustic NC-50 for industrial bays

Australian recreational boat plants typically target Noise Criterion NC-50 inside the production bays — an industrial standard that protects operator hearing without imposing the much higher cost of an NC-30 office target. Acoustic control is delivered through:

• Inertia bases on every fan, blower and air handler over 7.5 kW;
• Flexible canvas or rubber connections at every fan inlet and outlet;
• Acoustic lagging on supply ductwork in the first 6 metres downstream of the fan;
• Lined plenums where supply duct transits design office, customer walk-through or administrative areas;
• Sound power data on every fan submittal to verify NC-50 is achieved at the operator location.

The SBKJ machine configuration for boat building plant ductwork

SBKJ supplies three core machines for the manufacture of the ductwork specified in this guide. The configuration below is the standard package supplied to a recreational boat building plant or to a regional ductwork fabricator servicing the marine market.

SBAL-V Auto Duct Line — 316L stainless configuration

The SBAL-V Auto Duct Line is SBKJ's flagship rectangular duct production line. For boat building plant ductwork the machine is specified in the 316L stainless configuration with the following options:

• Coil capacity up to 1,550 mm wide, 0.5 to 1.5 mm thickness in stainless 316L;
• Pittsburgh seam lock-forming with stainless-compatible tooling;
• TDF flange forming integrated on the same line for stainless-to-stainless joints;
• Siemens PLC and HMI with English-language operator interface;
• Single-shift output of 800 to 1,200 metres equivalent of stainless 316L ductwork per shift;
• CAD layout drawing for the buyer's workshop supplied with every quotation.

The SBAL-V configured for stainless 316L runs at approximately 60 percent of the throughput of the equivalent machine on galvanized coil, reflecting the higher tooling load required by stainless. SBKJ supplies hardened tooling rated for at least 100,000 metres of stainless formed before regrinding.

SBTF-1602 Spiral Tubeformer — for round duct branches

The SBTF-1602 Spiral Tubeformer produces round spiral-seam duct from 100 mm to 1,600 mm diameter. For a boat building plant the round duct application is primarily on the resin mixing room exhaust runs, the cure oven recirculation loop and the carbon dust collection branches where round duct is preferred over rectangular for cleaning access and continuity.

The SBTF-1602 is specified for stainless 316L coil with the standard machine configuration, with output of 5 to 8 metres per minute of finished spiral duct depending on diameter.

TIG seam welder — for continuously-welded duct seams

NFPA 33 and NFPA 484 both require continuously welded duct seams in classified zones and in carbon dust extraction. The SBKJ TIG seam welder converts a Pittsburgh-lock formed duct from the SBAL-V into a continuously TIG-welded seam suitable for hazardous-area service. The welder is supplied with stainless 316L filler wire, argon shielding gas regulator package and a fume extraction hood for the operator station.

Plant build sequence — typical 18 to 24 month timeline

A greenfield recreational boat plant in Australia typically runs an 18 to 24 month build timeline from site selection to first hull launch. The HVAC procurement timeline runs in parallel with the building shell, with key milestones aligned as follows:

1. Months 0 to 3 — site selection, planning approval, hazardous area classification drawing, initial ductwork specification;
2. Months 3 to 6 — building shell construction begins, HVAC RFQ to vendors, vendor shortlist;
3. Months 6 to 9 — HVAC contract award, ductwork machine procurement (SBKJ SBAL-V on a 10 to 12 week build at the Australian assembly facility), fan and air handler procurement;
4. Months 9 to 12 — building shell complete, HVAC plant room rough-in, ductwork fabrication begins;
5. Months 12 to 15 — ductwork installation, control system installation, balancing;
6. Months 15 to 18 — commissioning, NATA-accredited air flow verification, hazardous area certification, ATEX/IECEx documentation pack handover;
7. Months 18 to 24 — production ramp-up, first hull pulled from tooling, sea trials of first launch.

Documentation pack — what the facility manager should receive

At handover the HVAC contractor should provide a documentation pack that satisfies both the building certifier and any future insurance survey. The pack should include:

• As-built drawings showing every duct run, every diffuser, every damper, every continuity test point;
• Hazardous area classification drawing with the Zone 1 and Zone 2 boundaries marked;
• ATEX/IECEx certificates for every fan motor in a classified zone;
• NATA-accredited air flow measurement at every diffuser, verified against the design drawings;
• Smoke-pencil verification report at every welding hood, spray booth and capture point;
• Continuity test report for the carbon dust collection ductwork (under 10 ohms across the full run);
• Operator and maintenance manuals in English;
• PLC programme backup on USB or cloud drive;
• Fan and motor data plates;
• Spare parts list and supplier contact details for at least 10 years of continuity.

How SBKJ supports Australian boat builders

SBKJ Group operates from Box Hill North in Victoria as the Australian sales and engineering office for the SBKJ machine portfolio. We supply ductwork production machinery to Australian boat builders, to regional ductwork fabricators servicing the marine market, and to facility engineering consultants designing ventilation systems for greenfield boat plants. Specifically we provide:

• Stainless 316L machine configurations — SBAL-V Auto Duct Line, SBTF-1602 Spiral Tubeformer and TIG seam welder configured for stainless 316L coil with hardened tooling rated for marine-grade duct production;
• CAD layout drawings — every quotation includes a CAD layout drawing showing the machine in the buyer's workshop, with run-out tables and coil storage;
• Factory Acceptance Test — every machine is tested with the buyer's nominated coil specification before shipment;
• Australian after-sales — English-speaking engineering support from the Box Hill North office, 72-hour response on remote support, 10-year+ spare parts continuity;
• Installation and commissioning — SBKJ engineers on site for 5 to 10 days for mechanical and electrical commissioning;
• Operator and maintenance training — 8 to 16 hours operator training and 4 to 8 hours maintenance training, with a written commissioning report.

For boat builders evaluating SBKJ as a ductwork machinery supplier, our 47-point pre-purchase verification checklist is the same document we use ourselves when our customers ask us how to evaluate a shortlist of suppliers.

Talk to an SBKJ engineer about your boat plant ductwork specification →

FAQ

Why does galvanized ductwork fail in recreational boat manufacturing facilities?

Galvanized ductwork fails in boat building plants because the combined exposure of styrene monomer from open polyester resin, acetone solvent used for tool cleaning, MEKP catalyst aerosol and saline coastal air corrodes the zinc coating within 18 to 36 months. Once the zinc is consumed, pitting attacks the underlying steel along the longitudinal seam and at every transverse joint. SBKJ specifies stainless 316L ductwork in fiberglass layup halls, resin mixing rooms, gelcoat spray booths and polyurethane paint shops.

What hazardous area classification applies to a resin mixing room?

A boat builder resin mixing room handling unsaturated polyester resin, vinyl ester resin, styrene monomer make-up and MEKP catalyst is classified Zone 1 hazardous area under AS/NZS 60079.10.1 because flammable vapour is expected during normal mixing operations. All ventilation, electrical equipment and instrumentation in the room must be certified Ex equipment to AS/NZS 60079 or IECEx, with exhaust fans rated Ex d IIB T3 minimum.

What is the styrene exposure limit operators must be kept under?

Safe Work Australia publishes a workplace exposure standard for styrene of 50 parts per million as an eight-hour time-weighted average, with a 100 ppm short-term exposure limit over 15 minutes. The practical design target is to keep operator breathing-zone styrene under 25 ppm, providing a 50 percent safety margin against the regulatory limit.

Why does carbon fibre dust require conductive ductwork?

Cured carbon fibre composite dust is electrically conductive. When conductive carbon dust accumulates on duct walls or settles into electrical cabinets, it bridges across exposed terminals and causes short-circuit faults that can ignite an explosive dust cloud. NFPA 484 classifies carbon fibre dust as a combustible metal-like material requiring full deflagration protection — bonded conductive ductwork, electrically continuous flanges, explosion isolation valves and either explosion venting or chemical suppression on the collector.

What ductwork is required for a gelcoat downdraft spray booth?

A gelcoat downdraft spray booth must be designed to NFPA 33. The booth pulls 0.5 metres per second face velocity downward through filter floors. All duct seams must be continuously welded with no rivets or sealants that could spark; access doors must use captive gasketed clamps; and the exhaust fan must be spark-resistant non-ferrous wheel construction. Make-up air must be tempered to within 2 degrees Celsius of booth ambient to prevent gelcoat micro-cratering.