The short version
- What it is
- A second mark a short way from the windward mark. You round the windward mark, sail a short leg across the wind to the offset, round that, and only then start the run.
- Why it's there
- To keep boats bearing away and hoisting spinnakers out of the path of boats still beating up to the windward mark.
- Which way
- Usually the same way as the windward mark — on a port-rounding course, both to port. The sailing instructions say for certain.
- How to use it
- Treat the short leg as your preparation time: get the boat set for the run, then round the offset and set the spinnaker.
Why committees set one
On a windward-leeward course without an offset, the windward mark is the busiest piece of water on the course. The leaders round and bear away while the rest of the fleet is still arriving on the starboard layline. A boat that has just rounded is bearing away, hoisting and trying to get its spinnaker to fill — and it's doing that directly in front of boats close-hauled at full speed. That's a recipe for collisions, protests and spinnakers wrapped round other people's forestays.
The offset mark moves the bear-away somewhere else. Boats round the windward mark, sail a short leg away from the layline, and turn downwind only once they're clear of the traffic coming up. It also gives the boats that have rounded a few seconds to get organised before the run, so the hoists are cleaner and the fleet is less bunched.
Where it goes and which way you round it
On the usual port-rounding course, the offset sits to the left of the windward mark, looking upwind — the side you're turning toward as you round. The leg between them is roughly across the wind, so it's a short reach. You round the offset the same way as the windward mark: to port.
How far apart the two marks are varies with the venue, the fleet and the size of the boats. As a rough idea it's often somewhere in the region of 50 to 100 m (160 to 330 ft) — far enough to separate the traffic, short enough that the leg isn't a race of its own. Don't assume: the sailing instructions describe the course, and some courses round the offset differently or leave it out on some laps.
The sequence: windward mark to run
With an offset, the windward rounding splits into two smaller turns, and the jobs split between them.
1. Round the windward mark
Come in on the starboard layline at full speed, without overstanding. Bear away only as far as the reach to the offset needs — usually to a beam reach or a little lower — easing the sails as you turn and keeping the boat flat.
2. Prepare on the short leg
- Ease the upwind controls: cunningham, outhaul and vang to their downwind settings.
- Raise the centerboard as far as the reach allows, and move weight back.
- Get the spinnaker ready to go: pole ready, sheets and halyard clear, the person hoisting in position.
- Look down the run. Decide which side you want and which gybe you'll be on before you get to the offset.
3. Round the offset and set
Bear away around the offset onto the run, and hoist once the boat is pointed downwind and level — the same bear-away set as at a windward mark without an offset. In some boats, particularly those with asymmetric spinnakers, crews hoist on the reach itself if the angle allows; that's a boat-by-boat call. See Spinnaker launch and douse.
Tactics on the short leg
The offset leg is short, but it's still a leg, and boats close together do still interact on it.
- Clear air before the run. A boat just behind you on the reach is to windward of you once you've both borne away. Getting your hoist done quickly and cleanly is the best defence.
- The offset is a mark too. It has its own zone, so the mark-room rules apply there as they do at the windward mark. A boat that's overlapped inside you at the offset is entitled to room. See Mark-room.
- Think about the gybe. Rounding the offset on a port-rounding course leaves you on starboard gybe heading down the left side of the run. If you want the right side, a gybe soon after the offset gets you there — but a gybe straight after a hoist in a crowd is where things go wrong. Pick a clean moment.
- Don't stop the boat. It's tempting to do everything at once on the offset leg. Steer first; the jobs that can wait until after the hoist should.
Common mistakes
- Hoisting before the offset when the leg is too tight a reach for it, and then not being able to bear away round the mark with the spinnaker pulling hard.
- Skipping the offset. It's part of the course. Forget it and you haven't sailed the course, and you'll have to go back.
- Rounding it the wrong way. If the sailing instructions say to starboard, or the offset sits on the other side, the habit of a port rounding will catch you out.
- Bearing away too far at the windward mark, so you sail below the offset and have to head up to reach it.
Doing it with Sail Tactician
Questions
What is an offset mark in sailing?
A mark set a short distance from the windward mark. Boats round the windward mark, sail a short leg across the wind to the offset, round it and then start the run.
Which way do you round an offset mark?
Usually the same way as the windward mark — on a port-rounding course, to port. The sailing instructions are the authority.
How far is the offset mark from the windward mark?
It varies by venue and fleet, but it's often roughly 50 to 100 metres (160 to 330 feet). The sailing instructions or the race committee set it.
Does mark-room apply at the offset mark?
Yes. The offset is a mark like any other, with its own zone, so rule 18 applies when boats are overlapped there.
Sources
Mark-room at the offset from the Racing Rules of Sailing 2025–2028, rule 18, described in our own words. Course layout, typical distances and the rounding sequence from standard club and regatta practice; distances and rounding directions at any event are set by its sailing instructions. Sail Tactician behaviour from the in-app User Guide, version 3.2.
What changed
- First published.
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