Trawl Winch Product

Overview

A trawl winch is a powerful deck-mounted spooling machine that deploys and retrieves heavy bottom or midwater trawl fishing nets. The winch consists of two independent cast-iron drums, each capable of holding 800–1200 m of warp wire (the cable that connects the trawl to the vessel). The design uses a split-drum configuration—two drum sections on a single shaft—to allow independent or synchronized control of left and right doors, which are the rigid frames that hold the trawl mouth open during fishing. The winch is driven by a 30–60 hp electric or hydraulic motor through a 10:1 to 20:1 helical-gear reducer, powered by a proportional-joystick pendant control system that displays real-time load.

The Warp Wire Assembly (16–24 mm galvanized or stainless steel wire rope) connects each trawl door to a Split Drum. As the drums rotate, the Level-Wind Carriage carriage reciprocates horizontally, packing warp wire evenly across the drum face and preventing rope jam or uneven load concentration. A spring-set Brake Unit, backed by a 5 L accumulator, holds the load stationary when the Drive Motor is stopped, preventing runaway or sudden line release in rough seas.

The entire assembly is mounted on a welded Frame Base with vibration dampers, anchored to the vessel's deck via 30 mm studs. Control is via a sealed handheld Control Pendant with proportional joystick, variable-speed dial (0–100%), load display (0–200 tonnes), and emergency-stop button. Modern trawl winches integrate wireless control (2.4 GHz) to allow the net master to position themselves for optimized sight lines during trawl deployment and recovery.

How It Works

Pre-tow phase: The trawl net is secured on deck or in a net bin. The warp lines are attached to the top bridle eyes of each trawl door. The winch operator or net master engages the motor at slow speed (10–20% of maximum) and begins paying out warp from both drums symmetrically, keeping tension balanced. The Level-Wind Carriage carriage traverses across the drums to unwind wire evenly; if it were to spool off asymmetrically, rope jam and bearing overload would result.

Deployment: Once the desired warp length (typically 200–400 m, depending on water depth and trawling strategy) is deployed, the trawl door hitches are released, and the trawl net begins its descent. The winch is held in idle (brake applied, motor off) to prevent accidental payout. The vessel then moves forward at trawling speed (2.5–4 knots), and the warp hangs freely below, with the trawl doors splayed apart by hydrodynamic force, opening the trawl mouth.

Hauling phase: After 30–60 minutes of trawling, the operator engages the motor in reverse and proportionally increases speed via the joystick. The Drive Motor turns the Gearbox, which multiplies torque and spools warp wire back onto the Split Drum. As warp is retrieved, the Level-Wind Carriage carriage reciprocates to wind wire uniformly across the drum face width. Real-time load is displayed on the Load Display—indicated by tension in the warp lines, which is converted to hydraulic or electrical load-cell signal (0–200 tonnes range).

Trawl ascent and retrieval: The trawl net, now filled with catch, is hauled upward. The Brake Unit engages automatically if load suddenly increases (snag or fouling), preventing motor stall and protecting the gearbox. Crew stand by with grapnels (catching hooks) to secure the trawl bridle as it breaks the surface. Once the trawl doors are secured, the net bag is hoisted inboard using a separate Power Block or dedicated fish-lift winch (not part of the trawl winch itself). The empty trawl is emptied, inspected for damage, and re-stowed on deck.

Load management and safety: The Brake Pressure Accumulator (5 L, 100 bar pre-charge) is pressurized by a small auxiliary pump during idle periods. When hauling, if load rises suddenly (trawl hits bottom or snags), the brake is engaged proportionally via the Brake Solenoid to prevent catastrophic load shock. If the operator releases the joystick, the brake automatically applies. A hard over-pressure relief (not shown separately, but part of the gearbox or motor circuit) is set to 150 bar to protect hoses and seals.

Typical Trawler Configuration

• Vessel class: Stern trawler, 20–80 m length
• Trawl depth range: 100–2000 m depending on vessel and net design
• Warp length deployed: 200–600 m (3:1 to 6:1 ratio of water depth)
• Haul cycle time: 45–90 minutes (30–60 min tow, 10–20 min haul)
• Daily catch: 5–50 tonnes depending on stock and vessel efficiency
• Crew: 15–25 personnel (captain, net master, engineers, deck crew, processing crew)

Dual-Drum Advantages

The split-drum design allows two independent control strategies:

1. Synchronized hauling: Both drums haul at equal speed, keeping warp tension balanced, typical for bottom trawling in stable conditions.
2. Door control: Left and right drums can be operated at different speeds to angle the trawl doors, correcting for current drift or steering the trawl laterally during tow.
3. Emergency recovery: If one door is snagged, the operator can haul faster on the opposite drum to break the snag or alert crew to manual recovery.

Maintenance Schedule

• Weekly: Inspect warp wire for visible damage, fraying, or corrosion; verify brake pressure (accumulator gauge).
• Monthly: Lubricate Gearbox sump (check level and top-up with ISO VG 220 oil); inspect Level-Wind Roller bearings for play.
• Quarterly: Full system pressure test; brake clamping force verification via load cell; electrical connection inspection (pendant contacts and wireless transceiver).
• Annually: Warp wire replacement (or section replacement if damage detected); gearbox oil full change and filter replacement; motor bearing inspection; brake disc friction-face measurement.

Alternative Configurations

Single-drum variant: Some small trawlers use a single large drum (1.2–1.6 m) instead of split drums. This simplifies controls but offers less flexibility for door steering.

Carrousel hauler: Large industrial trawlers sometimes use a carrousel system (continuous rotating drum) instead of spooled winches, allowing simultaneous hauling and redeployment in rapid-succession fishing grounds.

Net drum integration: Some vessels integrate the trawl winch directly with a net-stowage drum (see Net Drum), creating a combined reel system that stores net and warp in a single rotating assembly.

Regulatory and Safety Considerations

Modern trawl winches are subject to DNV (Det Norske Veritas), ABS (American Bureau of Shipping), and national maritime authority certification. Load-limiting devices prevent exceeding rated warp tension; wireless controllers must include dead-man switches (loss of signal → automatic stop). Crew training on emergency stop and brake operation is mandated in commercial fisheries.