Learn the boat

Trim, in short

Everything you do to a sail is changing one of three things: how deep it is, how twisted it is, and how far off centreline it sits. That's the whole game.

Depth

Deep is power, flat is speed and control. Light air and chop want depth. Breeze wants flat. On the main, depth comes off with outhaul, backstay and cunningham; on the headsail, with halyard tension and forestay sag.

Twist

Twist is how much the top of the sail opens compared to the bottom. More twist spills power at the top and keeps the boat on its feet; less twist points higher when you have the crew weight to hold it. Main twist lives in the mainsheet and the traveller. Headsail twist lives in the lead car — forward closes the leech, aft opens it.

Angle

How far inboard the sail is sheeted. Closer to centreline points higher and goes slower. Further out foots faster and gives up height.

Three gears upwind

• High — sheet on, lead forward, traveller up. For holding a lane off the start, pinching to a mark, or making life hard for the boat to leeward.
• Normal — the fast, balanced setting. Where you live most of the race.
• Fast — ease and twist, bow down. To get to a shift, roll a boat to windward, or punch through chop after a tack.

The helm calls the gear. Trimmers answer with what they did. That loop — call, trim, report speed and height, repeat — is most of the difference between a quick boat and a slow one.

Telltales

Both streaming aft is right. Windward one lifting means you're too high or the sail is too tight — bear away or ease. Leeward one stalling means you're too low or sheeted too hard — come up or ease the sheet and let flow reattach.

Before you leave the dock

• Know where your PFD is and how it works
• Know which winch is yours and which way the handle goes in
• Find the one line you'll be responsible for, and flake it
• Ask what the first manoeuvre is after the start

On deck

Short calls, loud enough, once. Say what you see, not what you think it means — "puff in ten seconds, left side" beats "I think we should tack." Nobody stands on a sheet, nobody sits on a winch, and when something breaks the first words are what broke, not whose fault it was.