Basic Sails & Sailing
Everything else in the course assumes this vocabulary. This module covers the full IYT Module 15 syllabus at Working depth: how a sail actually generates drive, standing vs running rigging, the points of sail (with an interactive trim wheel), winches and deck hardware, the sail wardrobe from storm jib to spinnaker, reefing both ways, and what sails are made of.
How Sails Work
A sail works like an aircraft wing turned on its side (an aerofoil). As wind blows across the sail's curved shape, it produces a pulling force — the same force that lifts a plane — called lift. That force doesn't point straight ahead, though: part of it drives the boat forward, but a lot of it tries to push her sideways, and that sideways slip is called leeway. What stops the boat simply sliding sideways is the keel — the deep fin under the hull — which grips the water, resisting sideways movement while letting the boat slip forward easily. With the sideways push held in check, the forward part of the force wins and the boat moves ahead. Trimming the sails well is really just angling them so that as much of that force as possible points where you want to go.
- Head — the top corner
- Tack — bottom corner of the leading edge
- Clew — the aft (rear) corner
- Luff — the leading edge
- Leech — the trailing edge
- Foot — the bottom edge
Rigging & the Bermudan Sloop
Two families of rope and wire, two different jobs:
The fixed wires holding the mast up: forestay (to the bow), backstay (to the stern), and sidestays/shrouds. You tune it, you inspect it — you don't handle it while sailing.
The moving lines that hoist and trim: halyards raise the sails, sheets adjust their angle to the wind. This is the stuff in the crew's hands all day.
The Bermudan (sloop) rig — one mast, two triangular sails — is the modern default: a headsail (jib) hanked or furled on the forestay, and a mainsail hoisted up a mast track with its foot on the boom. A headsail grows into a genoa the moment its clew reaches past the mast — a 120% genoa carries 20% of its area past the mast, a 150% carries half.
Points of Sail
The wind's angle to the boat dictates how the sails are set — each named angle is a point of sail. One angle is off-limits: head closer than about 40° to the wind and the sail can't fly as an aerofoil; the boat stalls, stops, and sits "in irons." To reach an upwind destination you tack (turn the bow through the wind) and zig-zag — beating. Downwind, taking the stern through the wind is a gybe. Steer the boat around the wind and watch the trim:
Deck Hardware
U-shaped connectors — halyard to sail, block to padeye. Three forms: screw-pin (the everyday one), captive-pin (push and turn), and snap shackle (pull the pin for instant release).
Pulleys, with up to four sheaves. Led in series they give mechanical advantage, taming loaded lines — the mainsheet tackle is the everyday example.
All solve the same problem: hold a loaded line yet release it fast. Clutches (levers) let you take a line to a winch, lock it, and free the winch for another job.
Mainsheet — trims the main's tension/angle to the wind. Traveller — slides the sheet's anchor point to angle the boom port or starboard. Topping lift — holds the boom up off the deck once the sail is furled.
Winches
Even a light breeze puts enormous loads into sheets and halyards — winches are the gearing that lets human arms manage them. Most have two or three internal gear speeds (more power for the same handle effort), a star-shaped socket in the top for the locking handle, and on modern boats a self-tailing jaw that grips the tail so one person can crank and tail at once.
- Wrap the line clockwise around the drum — three turns under load
- Feed the tail into the self-tailing jaw
- Insert and lock the handle
- Grind; change gear by reversing rotation
- To ease: handle out, palm flat on the turns, ease smoothly
- Rings, necklaces and jewellery off before handling loaded lines — crushed fingers are the classic winch injury
- Fingers stay clear of the drum; feed with a flat palm
- Never wrap a loaded line around a hand
- Stow handles when not in use — a flying handle is a missile
The Sail Wardrobe
The workhorse aft of the mast, foot tensioned by the outhaul at the boom end, leech stiffened by battens. Its heavy-weather replacement is the trysail — small, very strong, thick cloth, set instead of the main when it's really blowing.
A range of sizes to suit conditions — numbered jibs down to a storm jib: tiny, triple-stitched, toughest sail aboard, set on the forestay. Remember the boundary: clew past the mast = genoa.
The biggest, lightest sail aboard, for running and broad reaching. Symmetric excels dead downwind; asymmetric (MPS) flies more like a huge jib, generating lift from the side — better for reaching, easier to handle, and the near-universal cruising choice.
Named for the panel layout: radial head (light air), horizontal (also light air), star (strong-wind reaching), and tri-radial — the blend of the other three and the most universal all-rounder.
Reefing & Sail Materials
As wind builds, a boat becomes progressively overpowered — harder on the helm, heeling further, slower. You reduce sail progressively, and the golden rule is sooner rather than later: leave it late and you're doing foredeck work in exactly the conditions you were trying to avoid. Typical sloop sequence: big No. 1 genoa → smaller No. 2 → first reef in the main → deeper reefs and smaller jibs → and beyond a triple-reefed main and No. 4 jib, the two storm sails (storm jib + trysail) keep you moving.
Furling gear rolls the headsail around the forestay to any size — and in-mast or in-boom systems do the same for the main. Fast, safe, done from the cockpit; the trade-off is a flatter, less efficient partial sail.
- Head up toward the wind and ease the mainsheet to unload the sail
- Ease the halyard while hauling the reefing line — the sail comes down to the boom
- At the reef point, secure halyard and reef line
- Bear away back on course and re-trim
- Tidy the loose bunt with sail ties through the grommets, around the boom
Materials: canvas and cotton gave way to polyester — Dacron, the durable cruising standard — now itself eclipsed for performance by Mylar, Kevlar and Spectra: stronger, lighter, better at holding a designed shape. Construction is panels of cloth, double-stitched, aligned to the load paths, with the head, tack and clew heavily reinforced so the cringles can take the big loads.
Basic Sails & Sailing — Knowledge Check
12 questions at IYT exam standard (75% to pass), drawn from the IYT Module 15 knowledge review.