A two-masted dipping lug rig carries a four-sided lugsail on each of two masts — a tall mainmast forward and a shorter mizzen aft — where the yard must be dipped around to the leeward side of the mast at every tack to keep the sail setting cleanly on the new weather side. A well-handled Cornish lugger could log 9-10 knots reaching in a breeze. The rig delivers high drive per square metre on a short, stayless mast, which is why East Coast Scottish Zulus and Mounts Bay luggers ran it for over a century of commercial fishing.
The Two-masted or Dipping Lug in Action
The dipping lug is a fore-and-aft sail in name only — the yard sits forward of the mast at roughly a third of its length, so the sail behaves more like a leaning square sail that has been swung to draw on the wind. On the starboard tack, the yard hangs to port of the mast and the sail pulls cleanly. Tack the boat and that geometry inverts. If you leave the yard where it is, the sail now presses against the mast on its weather face, the luff buckles, and you lose half your drive. The crew has to dip the yard — lower the throat, walk the heel of the yard around the back of the mast, and re-hoist on the new lee side. On a working two-master that is two yards to dip, with the mizzen normally dipped first because its yard is lighter and its sheet shorter.
Luff tension is what makes a lugsail set hard. The tack is hauled down to a fitting near the stem or to a traveller on the weather rail, and that downward pull combined with the halyard tension flattens the luff into a clean leading edge. If the tack pendant is slack — even by 100 mm on a 9 m luff — the sail sags off to leeward and pointing ability collapses. Crews learned to set the tack on the weather rail rather than centreline because moving the tack to weather opens the slot between mainsail and mizzen and lets the rig point another 5° higher.
The two-mast layout splits the sail area so neither yard is unmanageable, and the mizzen acts as a balancing sail that lets the helm be trimmed by sheeting the mizzen harder or easing it. Get the balance wrong and the boat either gripes up into wind under hard mizzen, or runs off to leeward with a slack one. That is the trim adjustment a lugger skipper makes constantly while drift-netting.
Key Components
- Mainmast: Unstayed or lightly stayed pole stepped about 25-30% of waterline length from the stem. On a 12 m Cornish lugger the mainmast runs around 9-10 m from step to truck, in pitch pine or spruce, with a hounds band carrying the halyard block.
- Mizzenmast: Shorter mast stepped near the transom, often raked aft 5-8°. Carries a smaller dipping or standing lug; on Zulus the mizzen was usually a standing lug to reduce dipping work, while Mounts Bay luggers kept both as dipping lugs.
- Yard: Spruce or Douglas fir spar from which the sail hangs. The slung point sits at about 33% of yard length from the throat — get this wrong by more than 50 mm and the peak either falls off to leeward or the throat lifts and spills wind.
- Lugsail: Four-sided sail with luff, head, leech and foot. Cut with about 8-10% broadseam in the lower third for shape, and a tabling at the head taking the lacing to the yard at roughly 100 mm spacing.
- Tack tackle: Two- or three-part tackle hauling the tack down to a fitting forward, usually on the weather rail when sailing close-hauled. Must hold tension equivalent to roughly half the halyard load.
- Halyard: Single-part or two-part line lifting the yard. On a 12 m lugger the halyard takes a working load around 200-300 kg and is belayed to a knighthead or pin rail with enough fall to lower the yard 1.5 m for dipping.
- Sheet: Led from the clew aft to a horse, bumkin, or quarter cleat. Mizzen sheets typically lead to a bumkin extending past the transom to keep the foot clear of the helmsman.
Industries That Rely on the Two-masted or Dipping Lug
The two-masted dipping lug ruled the British and Irish working-sail fleets for the back end of the 19th century because it gave a small crew enormous drive on a short rig, with no shrouds in the way of net handling. You will still see it on heritage builds, sail-training boats, and a handful of working replicas where the priority is authentic performance over labour-saving rigs.
- Heritage fishing fleet: The 1909 Manx nobby Master Frank and the restored Cornish lugger Barnabas (1881, St Ives) both sail with the two-masted dipping lug under Cornish Maritime Trust ownership.
- Scottish east-coast restoration: Reaper FR958, the Anstruther-based Fifie at the Scottish Fisheries Museum, sails as a two-masted dipping lugger and demonstrates the rig at festivals across the North Sea coast.
- Sail training: The Zulu replica Swan LK243 from Lerwick takes trainees out under twin dipping lugs as part of Shetland sail-training programmes.
- French working-sail revival: Chasse-marée luggers like the Corentin out of Bénodet carry three dipping lug masts but the same dipping discipline applies — the crew dips the foremast yard at every tack.
- Lifeboat heritage: Pre-1900 RNLI pulling-and-sailing lifeboats commonly used a two-masted dipping lug because the rig could be handed quickly and stowed clear of the oars.
- Open-boat racing: The Looe Lugger Regatta in Cornwall runs an annual fleet of two-masted dipping luggers including Our Daddy and Erin including hard upwind legs that show the rig's pointing limit.
The Formula Behind the Two-masted or Dipping Lug
What a skipper actually wants to predict before sailing is the driving force the rig will deliver at a given true wind speed, because that determines whether the boat will hold a course against tide or slip to leeward. The driving force scales with the square of apparent wind speed, so a doubling of wind quadruples drive — that is why luggers reef early. At the low end of the working range, around 8 knots true wind, the rig is loafing and you carry full sail with the tack at centreline. Around 15 knots the rig is in its sweet spot, tack moved to the weather rail, both lugs setting hard. Above 22 knots true the load on yard and halyard climbs past safe working limits and you reef the main first, mizzen second.
Variables
| Symbol | Meaning | Unit (SI) | Unit (Imperial) |
|---|---|---|---|
| Fdrive | Driving force along the boat's heading | N | lbf |
| ρair | Air density (≈1.225 at sea level, 15 °C) | kg/m³ | slug/ft³ |
| Asail | Combined sail area of main and mizzen lugs | m² | ft² |
| Vaw | Apparent wind speed across the sail | m/s | ft/s |
| CL | Lift coefficient of the lug rig (≈1.1 close-hauled, 1.4 reaching) | dimensionless | dimensionless |
| β | Angle between apparent wind and boat heading | degrees | degrees |
Worked Example: Two-masted or Dipping Lug in a 10 m Cornish lugger replica
Your traditional boat school in Looe, Cornwall is sea-trialling a 10 m two-masted dipping lug replica with 42 m² of mainsail and 14 m² of mizzen, and the skipper wants to know the drive force on a close-hauled leg at three wind conditions: a light 8 knots, a working 15 knots, and a hard 22 knots apparent, all at β = 30°.
Given
- Asail = 56 m²
- ρair = 1.225 kg/m³
- CL = 1.1 close-hauled
- β = 30 degrees
- Vaw,low = 4.1 m/s (8 knots)
- Vaw,nom = 7.7 m/s (15 knots)
- Vaw,high = 11.3 m/s (22 knots)
Solution
Step 1 — compute the nominal drive at 15 knots apparent, the working sweet spot for this hull:
That is roughly 250 lbf of forward drive — enough to push a 4-tonne lugger close-hauled at around 5 knots through the water. The boat is tracking, the helm has weight, the windward chainplate is creaking the right amount.
Step 2 — drop to the low end of the working range, 8 knots apparent. Wind speed is roughly half the nominal so dynamic pressure drops by a factor of four:
72 lbf. The boat ghosts along at 2-3 knots, the lug yards sag visibly between gusts, and you can hear the leech flutter. This is when crews move the tack back to centreline and ease sheets to keep what little flow they have attached.
Step 3 — push to the high end at 22 knots apparent:
540 lbf — more than double the nominal. In theory the rig keeps producing, but in practice the halyard load on a 10 m lugger climbs past 350 kg, the unstayed mainmast bends visibly to leeward, and the leeward gunwale starts dipping. Above this point you reef the main down a panel or hand the mizzen entirely. Most skippers tuck a reef around 18-20 knots apparent rather than wait for 22.
Result
Nominal driving force at 15 knots apparent on this 56 m² rig comes out to roughly 1,118 N (about 250 lbf), giving the lugger an honest 5 knots through the water close-hauled. The low-end figure of 318 N at 8 knots is barely enough to overcome hull drag and tide, while the high-end 2,403 N at 22 knots is past the safe working load of an unstayed mainmast and demands a reef — the sweet spot sits squarely at 12-16 knots apparent with full sail and the tack hauled to weather. If your measured boat speed falls 20-30% below what this drive force should deliver, look at three things: yard sling point drift (a peak that has fallen off to leeward by even 100 mm spills 15% of the area), tack pendant slack (a luff that sags 75 mm off the rail kills pointing by 5°), and mizzen oversheet (a hard mizzen forces the helm up and scrubs forward speed into leeway).
When to Use a Two-masted or Dipping Lug and When Not To
The dipping lug is not the only way to drive a working two-master. Skippers and restorers picking a rig for a new build or replica usually choose between the dipping lug, the standing lug, and the gaff ketch. Each one trades pointing ability, crew workload, and mast complexity differently.
| Property | Two-masted dipping lug | Two-masted standing lug | Gaff ketch |
|---|---|---|---|
| Pointing angle close-hauled | 50-55° off true wind | 55-60° off true wind | 45-50° off true wind |
| Crew workload per tack | High — yard must be dipped on each mast | Low — yard stays put | Medium — runners and preventers |
| Sail area per mast height | High (~1.4× standing lug) | Medium | Medium-high |
| Standing rigging needed | None or minimal | None or minimal | Shrouds, stays, runners |
| Typical minimum crew (12 m boat) | 3-4 | 2-3 | 2 |
| Reefing speed | Slow — yard must come down | Slow — yard must come down | Fast — slab reef at the mast |
| Cost to build (relative) | 1.0× baseline | 0.95× | 1.3-1.5× |
| Best application fit | Working sail, drift fishing, heritage | Small craft, single-handers | Cruising, long passages |
Frequently Asked Questions About Two-masted or Dipping Lug
That is the classic asymmetry of a dipping lug — and it usually means the yard is not actually being dipped, or it is being dipped imperfectly. On the tack where the yard sits properly to leeward of the mast, the sail sets in clean air and the luff is straight. On the other tack, if the crew shortcut the dip or the yard sling has snagged, the sail is pressing against the windward face of the mast, the luff is distorted by the mast itself, and you lose 3-5° of pointing.
Check by sighting up the luff from the tack fitting on each tack. If the luff curves around the mast on one side and runs straight on the other, you have a dipping discipline problem, not a sail-trim problem.
Mizzen first, almost always. The mizzen yard is lighter, the sheet is shorter, and dipping it first lets the boat carry way under the main while the foredeck crew work the heavier main yard. If you dip the main first, the boat loses drive immediately and may not have steerage to complete the tack — you end up in irons with a half-dipped main yard pinned against the mast.
Drop the mizzen sheet, walk the heel of the mizzen yard around, re-set, then call for the main dip. On a Reaper-sized Fifie that sequence takes about 90 seconds with four hands.
Working luggers settled on a mizzen at roughly 25-35% of mainsail area. Below 25% the mizzen cannot balance the helm under a hard reaching breeze and the boat gripes up; above 35% the mizzen starves the main of clean air on the wind and you lose drive on the bigger sail.
For a 12 m hull with 50 m² main, aim for 14-16 m² of mizzen. If you are designing a new replica and the historical sail plan is unclear, start at 30% and adjust by sailing the boat — helm balance under reaching conditions is the test.
Because the halyard is not just lifting the yard, it is also providing most of the luff tension that makes the sail set. On a typical 10 m lugger the static yard-and-sail weight might be 45 kg, but working halyard tension under sail runs 200-300 kg. The tack tackle pulls down hard, and the halyard has to react that load through the sling point.
If you size the halyard or the masthead block for static weight only, you will see the block crush, the halyard chafe through, or the sling parting under reaching loads. Size for a working load of around 5× yard-and-sail weight as a rule of thumb.
Yes on the mizzen, rarely on the main. The mizzen as a standing lug — yard stays put, sail just sheets across — is exactly what Scottish Zulus did, and it works because the mizzen is small enough that the loss of clean setting on one tack is tolerable. The main is a different story: it carries 70-75% of the drive, and accepting a poorly-setting main on every other tack costs you a knot of boat speed and 5° of pointing.
If your priority is cruising with two crew, go gaff ketch instead. If your priority is authentic working-sail performance, accept the dipping discipline on the main.
Because the centre of effort of a lug rig sits higher relative to sail area than people expect — the yard projects above the masthead, and the sail's geometric centre is roughly 55% of the way up the luff rather than the 40% you get on a triangular sail. Higher CE means more heeling moment per unit of drive.
Working luggers compensated with hard chines, deep keels, and ballast low in the hull. If you are converting a hull from Bermudian to dipping lug and the boat now heels alarmingly, the answer is usually internal ballast moved lower, not less sail.
References & Further Reading
- Wikipedia contributors. Lugger. Wikipedia
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