Bigger yacht, worse weather, a number or a decision wanted. Rope stretches or it does not, an anchor holds only along the seabed, and every load needs somewhere strong to go.
1 · Rope
Stretch, strength, and what a knot costs
How much strength does a bowline take out of a rope?
A bowline leaves about 60 % of the rope's strength, a splice about 90 %, a tight turn over a thin pin less. Divide what is left by a safety factor for the safe working load.
Rope
Behaviour and use
Nylon
Stretches: snubbers, tow and dock lines. Stiff and faded is weak
Dyneema
1% stretch, slippery, melts near 150 °C: no snubber
Aramid
Flexing and UV weaken it unseen: replace on age
A splice keeps about 90%, a bowline 60%, a tight turn over a thin pin less; divide what is left by a safety factor for the safe working load.
Working load of a tow line
16 mm nylon: breaks at 6.0 t when new
Wet: × 0.85 = 5.1 t
A bowline in it: × 0.6 = 3.06 t
Safety factor 5: about 0.6 t
Nylon: five tucks in an eye splice; a long splice keeps the diameter. Dyneema: knots slip, bury a long tapered tail.
Heavy warps: a seized carrick bend still unties; a bowline shakes loose in a surge. Sew whippings; coil right-hand lay clockwise; end-for-end a worn halyard.
Doubled lines in a surge
Line A 6 m, line B 12 m, both just taut
Stiffness ∝ 1 ÷ length: A is twice as stiff
A takes two-thirds of every snatch
Make doubled lines the same length
2 · Ground tackle
The anchor for the seabed
Which type of anchor holds in sand, soft mud or kelp?
Match it to the seabed: a roll-bar anchor in sand, as it resets when she swings; wide Danforth-type flukes in soft mud; a fisherman through kelp over rock. Nothing holds in sea-grass: find pale sand.
Seabed
What holds
Sand
Roll-bar anchor: resets as she swings
Soft mud
Wide flukes, Danforth type
Kelp over rock
Fisherman: narrow fluke gets through
Shingle
Heavy, sharp, loaded gently
Sea-grass
Nothing: find pale sand
Boulders
Buoy the chain's middle
The gypsy fits one chain standard; another jumps off under load. Lengthen the rode with 8-plait nylon spliced into the last link. Size chain for the whole load, worn: a snubber spares the windlass, not the chain.
Lower under power in deep water: free-falling chain outruns the brake. The windlass lifts only what hangs off the bottom. Lash the bitter end where you can cut it.
3 · At anchor
Enough rode, enough room, and a watch
How much anchor chain should I let out for a gale?
Measure scope from the bow roller: depth plus the roller's height, times 7 for a gale on chain and rope. In 18 m with the roller 2 m up, that is 140 m.
Scope is measured from the bow roller: depth plus its height, times the ratio, 7:1 for a gale on chain and rope. Heavier chain needs less.
Room to swing
Radius = chain along the bottom + boat
60 m of chain, roller 12 m above the seabed
√(60² − 12²) ≈ 59 m; + 24 m of yacht = 83 m
Boats lying differently: add both radii
Log a radar range and bearing every 15 minutes and set the alarm. An arc on the plotter is swinging, a straight line downwind dragging. Leave an open roadstead before an onshore gale; a strange bay at night: radar, sounder, a charted contour.
Against sheering: a riding sail aft on a ketch, a second anchor under foot on a high-bowed motor yacht. The kedge goes out in the tender, warp paid out as you go; aground on a lee bank, lay it to windward now.
4 · Two anchors
A V for a gale, a line for a stream
How do I lay a Bahamian moor in a reversing tidal stream?
Let go up-stream, drop back twice the scope, let go the second anchor, then heave back to the middle: a Bahamian moor lies in line with the stream, the yacht between its two anchors.
For a gale that will veer, lay both anchors ahead in a V across the shift, so each takes its share.
In a reversing stream lay a Bahamian moor: two anchors in line with it, the yacht between. Let go up-stream, drop back twice the scope, let go again, heave back to the middle. A cross wind pushes her sideways until both legs are taut.
5 · Berthing
Springs, screws and the stream
How do I walk a twin-engine yacht sideways?
With twin screws, one ahead and one astern, the stern swings towards the engine going ahead; put the bow thruster the same way and she walks sideways.
Twin screws: one ahead, one astern, the stern swings towards the engine going ahead; thruster the same way and she walks sideways. One engine astern alone throws the stern away from it: outward-turning, offset and prop walk add up. A right-handed propeller kicks the stern to port astern: get sternway on early.
Berth
What works
Stream along quay
Both engines ahead, bow angled in: it ferries her over
Stream astern
Pass the berth, back up against it
Piles
Up-tide pile first; fender board in a swell
Tidal wall
Slack in long springs: 15 m needs 0.8 m for 5 m
Raft
Largest inside; outer boats cast off to let you out
Stern-to in a gusty crosswind
Gusts 26 kn: load ≈ V² ÷ 60 kgf per m²
Bow windage 24 m²: 26² ÷ 60 × 24 ≈ 270 kgf
Thruster 160 kgf cannot hold it
Anchor upwind, snub the chain: it holds the bow
Engines place the stern
Plan for the gust; the thruster is for short bursts. Crossed stern lines check a sideways swing; where lazy lines lie, your anchor fouls the ground chains.
6 · Towing
A long, elastic line and a slow tow
How long should the towline be when towing another yacht in a seaway?
About one wave length, 1.56 × the period squared: with an 8-second sea, 100 m. The spring is nylon's stretch, not a weight on the line; tow at about two-thirds of hull speed.
Decide
Rule of thumb
Towline
One wave length, 1.56 × T²: 8 s, 100 m
Speed
⅔ of hull speed 1.34 × √LWL ft: LWL 10 m, 5.1 kn
Bridle leg
Pull ÷ 2 cos half-angle: 1.6 t at 90°, 1.1 t
Agree channel, speed and signals first. Make fast with turns round a strong point you can ease or cut; a ship's tow: spread the pull over mast foot and both bow cleats. Chafe parts tows; the spring is nylon's stretch, not a weight on the line.
Night orders for the tow
Watch aft on the line, knife to hand
Chafe and VHF check every hour
Tow steers in our wake; drogue if she sheers
Line parts: engines neutral, recover it
Before the bar: shorten up, then alongside
Offshore: tender on deck
Length of tow: your stern to the tow's stern. Over 200 m: three masthead lights, not two, and diamonds by day. No towing lights? Light the towline (Rule 24(i)).
Up to 200 m
Over 200 m
From astern
7 · Heavy weather
An end to the seas
In a gale, should I heave to, run off or use a sea anchor?
Never lie a-hull, beam-on to breaking crests. Heave to with the main eased and helm to leeward to drift slowly, run off fast with a drogue on a bridle, or lie to a parachute sea anchor for the least drift.
Never lie a-hull: beam-on, a breaking crest can roll her. Drift times hours of gale must fit your sea room.
Tactic
How
Heave to
Main eased, helm to leeward, 50° off the wind; slow
Run off
Drogue on a bridle to both quarters, 1.5 wave lengths; fast
Sea anchor
Parachute from the bow on long nylon; least drift; trip line
The trysail has its own track and two sheets to the quarters, led before hoisting; a forward lead tightens the leech. The storm jib hanks to an inner forestay on a tack pennant; try both in harbour.
Can she run with the seas?
LWL 21.5 m = 70.5 ft: 1.34 × √70.5 ≈ 11 kn
Period 6 s: 1.56 × 6 = 9.4 m/s ≈ 18 kn
She cannot keep up: slow down, let them pass under her
A motor yacht cannot heave to: she jogs at displacement speed, seas fine on the bow, and running lets faster waves pass, tabs up. A lowered trim tab lifts its own side; a burst ahead on the engine she yaws towards checks her.
Practice questions
Questions from this topic, as the app asks them. Open one to see the answer.
The mate's offer for the snubber
14 mm Dyneema, spare halyard stock “Twice as strong as our nylon”
Stretch at working load: about 1%
You are rigging a snubber for a night at anchor in your 24 m yacht, with a swell running in. Your mate offers the line in the figure. What do you say?
No: it hardly stretches, so each snatch hits the fittings
Yes, if you double it so that it can never part
Yes, once each end has a good whipping on it
Yes: twice the strength means half the risk of parting
Show the answer
A. No: it hardly stretches, so each snatch hits the fittings
A snubber works by stretching; Dyneema stretches about 1%, so the shock loads go straight into the chain, cleats and windlass.
All 100 questions of this topic are in the app: practice by topic with the reason after every answer, your mistakes brought back, and a timed mock exam. Free, no sign-up, in the browser or in Telegram.
