Push tug simulator — flanking rudders, backing down a narrow cut, in the browser

A push tug is driven backwards as much as forwards, and that is where ordinary steering lets go: with the screws astern the rudders behind them have almost nothing to bite on. Flanking rudders solve it, but nobody learns them from a drawing — you learn by backing a square-bowed, 110-tonne boat down a cut twice her beam wide, in a crosswind, and finding out which way her stern goes. Our push tug is built for exactly that, with real towlines and a scored flanking exercise. You can take her helm now, in the browser, on your phone too.

The boat

The PUSH TUG is a river and harbour push tug of our own design, 18.0 m long, 7.6 m in the beam, drawing 1.9 m, about 110 t. She has twin screws in nozzles, about 400 kW each, on two levers; two steering rudders behind the screws (the wheel, ±45°) and two flanking rudders ahead of them (also ±45°). Her square bow carries push knees, she has tow bitts fore and aft, and her wheelhouse is raised — the height a pusher needs to see over a barge. Measured in the simulator: 8.9 kn ahead, 6.6 kn astern, 13 t bollard pull.

Her character is all in the rudders. Going ahead the flanking rudders sit in the screws' inflow and do little — about a fifth of the steering rudders' effect, and the other way. Going astern it reverses: the screws' discharge runs forward over the flanking rudders and they steer her, while the steering rudders go dead. Backing at full astern, steering rudders hard over give 1.0° a second; flanking rudders hard over give 5.8°. The rule on the panel: astern, the lever is the way her stern goes.

The 3-D view puts you in her wheelhouse with the bridge window live — drag to look round, tap a vessel for 7× binoculars. ⚓ DOCK (ENTER) shows the water from straight above, north up, with only her own controls: the two levers, the rudders, her lines and fenders. FORCES draws the wash behind each screw — ahead a short wake aft, astern the wash running forward along her side — so a split is plain to see, with the wind arrow and her drift in metres a minute.

What you learn on her

Every skill below is tied to a control or a mode you will find in the simulator:

• Twin-screw handling. Two levers, one screw each; Q / E twist her on them. One ahead and one astern turns her on the spot.
• Flanking rudders, astern. Z / C move them, X puts them midships. Back her down, feel the flanking rudders take over, and learn to lead her stern with the lever before she wanders.
• Backing a cut: ⛓ TOWING exercise 6, FLANKING. A buoyed cut 36 m wide with 14 kn of wind across it: stern first through five gates, then turn and stop outside. Scored out of 100 — gates 30, buoys 20, heading 20, stern first 10, time 20 — with a briefing and live steps on the TOW panel. Run it on the flanking rudders and the gates come easily; try the same run on the steering rudders alone and she wanders out of the cut. That gap is the lesson.
• Watch it done first: ▶ DEMO. A demo tug master sails the exercise on your own boat, every order through the real control, each lit with an orange ring, the DEMO bar saying what and why. At the end ▶ YOUR TURN gives you the same start with the guide line on.
• Lines that behave like rope: the TOW panel. + YACHT, + COASTER or + SHIP 5 kn calls a tow ahead of you. Within 30 m of her bow and under 2 kn apart, T passes the line — a heaving line, then the towline made fast while you hold station 10 s. Y makes fast alongside for a hip tow: you con the pair as one.
• The winch and the brake. I heaves in, J holds, K pays out; BRAKE − / + sets the load at which it renders; G lets a slack line go; R is the QUICK RELEASE. Lines hang in a catenary, stretch (nylon a lot, HMPE little, wire hardly) and part at their breaking load or at the tow's weakest fitting — a yacht's bow cleat goes long before your line. A parting line snaps back.
• Girting — and the way out. A line leading abeam, high on her staple, heels a tug over. The HEEL gauge marks her deck edge; the docking plan draws the safe sector (within about 45° of right astern) and the red girting sectors. Take the power off, turn under the line, RELEASE (R) before she goes.
• Rule 24 lights and Rule 35 sound. Towing astern: two masthead lights in a line, sidelights, sternlight and a yellow towing light; three masthead lights and a black diamond over 200 m. Pushing ahead or alongside: two masthead lights, no towing light. In fog one prolonged and two short blasts — FOG AUTO (Shift+Y) sounds it for you.

The six towing exercises run in open water of the Gulf of Riga, each with its own wind and sea, no traffic, TIME ×1, a debrief scored out of 100 and the best score kept in your browser. The other five — a disabled yacht, a dead coaster on a long wire, a hip tow, escorting a tanker, push-pull with a second tug — are sailed on the ASD TUG: the two tugs make one towage course.

The sea is real

Outside the exercises the push tug sails in Free Mode, which starts in a real sea area: the Gulf of Riga off the Daugava mouth. For a tug the AREA to pick is "Daugava, port of Riga" — the river itself, the tanker at a terminal quay a mile up, the cruise ship at the passenger terminal by the old town. Past the Gulf the whole Baltic is there, Gotland to the Danish straits, at coarse detail for everyone and in detail from Luleå to Kiel with the; 107 real harbours are in the picker.

The wind is today's real wind — MET Norway's forecast where you are — and so is the weather: cloud, rain, snow, fog and the visibility they leave; the sun, moon and stars stand where they really stand, and lights and buoys light up at sunset. The water moves too: the CURRENT tile shows the Daugava running by its monthly discharge for today's date, 0.2–0.4 kn most of the year and 1–1.5 kn in the April flood. Her hull feels it — STW differs from SOG, she crabs across it, a current that differs along her length turns her. The sea surges both ends of a towline.

The chart is OpenSeaMap, with EMODnet depths on request; the radar has short ranges (0.25 to 1.5 NM) for rivers and harbours; tap any target for RNG, BRG, CPA, TCPA. The traffic keeps COLREG and sounds its signals — you hear them before you see them.

Shared sea — other real people on the water

Logged in, SHARED SEA is on by default — one live sea for everyone at ×1 — and you can switch it off. The boat you meet in the fairway may be another real person, and COLREG then means what it means at sea: a real give-way, a real sound signal, a real CPA. A practice wind is yours only — the others keep the real wind and see PRACTICE WIND by your boat's name.

Classroom and the scenario builder — for schools, clubs and instructors

✎ SCENARIO BUILDER opens over the simulator: a chart and tabs. The instructor writes the brief, sets the place (any harbour of the Gulf or the Baltic, or a point on the chart), puts the push tug UNDER WAY or MADE FAST at a berth, chooses day, night or a clock time on any date, sets wind, gusts, visibility down to thick fog and sea state. ⊕ VESSEL adds traffic with AIS names, Rule 18 types and routes; ▱ AREA and triggers make the fog close in, the wind change, a vessel start or a VTS message appear. ⇗ MAKE A LINK packs the whole scenario into the link itself — nothing is stored on our server — ready to ▶ RUN.

🎓 CLASSROOM → TEACH opens a private class: free sailing, a scenario, a docking lesson or a drill — towage among them. OPEN THE CLASS gives a code and a link; up to 30 students join from any browser — a laptop, a Chromebook, an iPad — on the class's own private sea at ×1. The instructor view shows every boat with her track, CPA ring, speed, heading, contacts and score, and the controls: ❚❚ PAUSE ALL, a message, 🌫 FOG, 🌬 WIND, ⚙ ENGINE FAILURE, ↺ RESET TO START, ▤ SUMMARY to CSV or print. TEACH is for the subscriber or instructor; students run shared scenarios for free.

Where she fits

The push tug lives in ⛓ TOWING (beside ⚓ DOCK) with the ASD TUG, and in the TOW panel for free practice. Her drills have ▦ PLAN · ◩ 3-D, ▶ DEMO beside START and the ┄ GUIDE line. ⛶ GLASS fills the screen with the view, HELM, RADAR and CHART over it. Any gamepad or throttle quadrant steers her — TWIN LEVERS, a stick each.

Who it is for

Professional and leisure alike. The cadet before the first watch, the deck officer, the pilot, the tug, offshore or survey crew, the training centre that wants a situation every student can repeat — and, on the same sea, the leisure skipper who is curious how the working boats are handled and what the ship on the horizon can and cannot do. The vessel, the sea and the rules are the same for everyone; only the exercises are the professional's.

How to start

Free Mode is open to everyone — no account needed — with the 15 m motor yacht and the 50 ft cruiser LATEKO at up to TIME ×10; every other vessel — the push tug, the ASD tug and the towing exercises among them — the docking, sailing and ECDIS units, the scenario builder and Classroom TEACH come with the simulator subscription; students join shared scenarios free. SHARED SEA and the regatta need a free SkipperCheck login. Our main product is the VHF course (€199) at /vhf-course: the certificate comes from the course, the practice from the simulator.

FAQ

Does it run on a Mac or a phone?

Yes. It runs in the browser, nothing to install; on an upright phone the panel sits under the view.

Is the wind real?

Yes — MET Norway's forecast where you are, with the real sky and weather. The towing exercises set their own wind for a fair score.

Can I sail with friends?

Yes. The shared sea puts everyone on one sea at ×1; a class or a scenario link gives you a private one.

Can a school use it?

Yes. An instructor opens a class in 🎓 CLASSROOM → TEACH and hands out a code; up to 30 students join from any browser, and shared scenarios are free for them.

Do I get a certificate?

The VHF course gives the certificate; the simulator gives the practice, scored out of 100.

Take the push tug's levers in the simulator: /colreg-simulator?scenario=familiarization&area=gulf-of-riga&vessel=pushtug — or begin with the course that comes first, /vhf-course.

Related reading

• Tug simulator — towing, escort and push-pull with real towlines, in the browser
• ASD tug simulator — harbour towage, azimuth drives and the towline, in the browser
• Tanker simulator — ship handling on a 183 m product tanker, in the browser
• All articles · Open the simulator

Boat types are described generically; SkipperCheck is not affiliated with any boat builder or class association.