Tracking, or cordelling, pulls a boat upstream from the bank with a 20-30 m rope attached about one third of the way back from the bow, hauled by people or a horse walking the bank while the helmsman steers; it is slow, 2-3 km/h, and exhausting, but it works where the current is too strong for poling. With a 25 m line and the boat 10 m from the bank, the rope pulls at 23.6° and 40% of the tow force acts sideways, which a bow attachment turns into three times the steering torque of the carrier’s one-third position.
Part of River Navigation & Ferry Systems
Tracking is towing a boat upstream with a long rope from people or animals on the bank, used where the current is too strong to pole.
The Rope Also Pulls The Boat Toward The Bank
The carrier’s method has four parts: a long rope of 20-30 m attached to the bow at a point about one third back from the bow; people or a horse on the bank pulling the rope at an angle; the helmsman steering to keep the boat in the channel; and a second line from the stern for control. The method moved cargo up the Missouri and Mississippi rivers for decades before steamboats, at 2-3 km/h.
The geometry produces a sideways pull. The rope runs from the bank to the boat, so only part of the tension is along the river. The rest drags the boat toward the bank, and unless it is countered the boat sheers in and grounds. The stern line, the rudder and the choice of attachment point are the three controls.
What You Need
- A towline 20-30 m long, tested for strength (see Rope Strength Testing), plus a stern line
- A clear bank path with firm footing, free of fallen trees
- A bridle or a strong attachment point about one third of the way back from the bow
- A rudder or steering oar and a helmsman who watches the tow
- A tow crew of people or an animal, with a signal to stop
Method: Set Up And Tow
Step 1: Walk the bank first and clear or mark obstacles.
Step 2: Fix the attachment at the one-third point; lash a bridle to a thwart or frame, not to the planking alone.
Step 3: Take up the slack slowly; start the boat moving with a steady pull, not a jerk.
Step 4: Steer to keep the boat out from the bank at the rope’s natural angle, and use the stern line to control sheer.
Step 5: Stop the tow before any hazard, and have a rule for dropping the rope.
Worked Example: Sideways Pull And Steering Torque
A 25 m rope pulling a boat 10 m from the bank makes an angle α with the bank: sin α = 10 ÷ 25 = 0.40, so α = 23.6°. Sideways component = tension × sin α = 0.40 × tension, that is 40% of it. Suppose the tow tension is 1,000 N (an assumed value). The sideways pull is 400 N toward the bank. Take a boat 6 m long with its centre of lateral resistance at midships (an assumption). Attached at the bow, 3.0 m from midships, the sideways pull gives a turning moment of 400 × 3.0 = 1,200 N·m. Attached at one third back from the bow, 2.0 m from the bow and 1.0 m forward of midships, it gives 400 × 1.0 = 400 N·m, one third as much. That is the reason for the carrier’s attachment point.
Speed: at 2-3 km/h, 10 km takes 10 ÷ 2 = 5 hours to 10 ÷ 3 = 3.3 hours. Rope: for a 1,000 N tow at a 5:1 safety factor the breaking strength needed is 5,000 N. The corpus gives 445-890 N for a 6 mm cord (100-200 lbf); if strength scales with cross-section (an assumption), the diameter is 6 × √(5,000 ÷ 890) = 14 mm to 6 × √(5,000 ÷ 445) = 20 mm.
Common Mistakes
- Attaching the line at the bow — the boat sheers in with three times the torque.
- Tying the rope to a person’s body — see below.
- Pulling in jerks — a jerk puts a peak tension above the steady pull on rope and crew.
- A towpath along a cut bank — the bank collapses.
Safety
A rope under tension kills and drags
A parted rope whips back; a rope round a person’s waist or wrist drags them into the river if the boat is swept away or grounds; and a bank path may be slippery or undercut. Never tie the tow rope to a body, make the end release instantly, keep onlookers out of the line of the rope, and never tow in flood. See Rope Strength Testing for the safety factors.
What’s Next
- Learn next: River Cargo Operations — what the towed boat is carrying
- Combine with: Poling Upstream — the alternative in weaker current