Leaving Boat 2 Alongside on a Falling Tide
At the Sea Cadet Corps unit's harbour you have two 27-foot whaler boats and ten cadets. It is 15:40. Boat 2 must be left secured alongside the jetty for about two and a half hours while the cadets attend their seamanship class, and the tide will fall about 1.6 m in that time. The jetty bollards sit 0.9 m above the present waterline and the slipway dries out. Cadet Rane has secured the bow painter to a ring on the jetty using a reef knot pulled tight, and Cadet Fernandes has made off the stern line to a bollard with a single clove hitch, with two round turns of slack left lying on the deck. The wind is south-westerly, force 4, pushing the boat off the jetty, and the spring line you asked for has not been rigged. The other instructor has taken Boat 1 out and is not expected back before 17:00.
1. Judge the two make-fasts. Which are wrong, why, and what would you tie instead?
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Bow painter - reef knot to a ring: wrong twice over. A reef knot is for reefing sails and for bandages; under a steady pull it capsizes and either jams solid or spills, and it is not a bend for a ring at all. Replace it with a bowline to the ring - it holds under load and breaks easily even when wet - or a round turn and two half hitches, or a fisherman's bend for a semi-permanent mooring.
Stern line - single clove hitch on a bollard: wrong for this berth. A clove hitch will take a steady load but slips under a load that veers or alternates, and with the wind pushing her off the jetty she will surge against it all afternoon. The two turns of slack lying on deck are not scope; they are a trip hazard and a sign the line was never properly set. Replace with three or four round turns around the bollard, then two half hitches - the turns take the strain, the hitch locks it - or a figure-of-eight over the bollard.
Then check it yourself: take the line and put your weight on it. A knot accepted on a cadet's word is not a knot that has been checked.
2. The tide falls 1.6 m in those two and a half hours. What does that change, and what is the specific danger you must prevent?
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It changes the geometry of every line. A line set bar-taut at 15:40 is a steel wire by 17:00, and any line led up to a bollard 0.9 m above the water gets steeper as the water drops.
The specific danger is hanging off. With a short line to a ring or bollard above her, the boat can be left hanging from the jetty as the tide falls, or her gunwale can be pulled down until she fills and capsizes as she takes the ground. That is the classic alongside accident and it kills people who are not even on board.
What to do: give each line enough scope for the fall while keeping her off the neighbouring berth; lead lines so they tend to lead down rather than up as the water drops, or shift to a lower ring; rig the spring so she cannot walk fore and aft; if the berth cannot be made safe for a 1.6 m fall, move her to deeper water or beach her deliberately near the slipway and secure her for the falling tide. Then check at 16:30 and again at 17:15 - the boat that comes adrift is the one nobody looked at.
3. What do you check before you walk away, and what is your plan if she does come adrift?
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Before leaving her:
- Every knot and every make-fast checked by hand, under load.
- Fenders on the jetty side; no line crossing where it will chafe through on the jetty edge.
- Plug in, oars and gear stowed and lashed, nothing loose that will float away.
- A chalk or rope mark on the jetty at the present waterline, so anyone can see the fall at a glance.
- Boat's name and unit painted on, and the harbour master told she is lying there and when you will return.
Watch-keeping: two instructors and ten cadets cannot run a seamanship class and watch a boat. Tell off one cadet to check every 30 minutes by name and time, and tell the harbour master - that is the plan, not an intention.
If she comes adrift: no cadet enters the water after her, ever. Raise the alarm to the harbour master, use Boat 1 if she is back and manned, throw a heaving line from the jetty, note the time. If she grounds, it becomes a written incident report to the unit commander - not something to be tidied up quietly before he hears of it.