A skiff yawl rig is a two-masted sail plan on a small open or half-decked boat, with a tall mainmast forward and a short mizzenmast stepped aft of the rudderpost. Sail areas typically split around 80% main and 20% mizzen, giving a total plan of roughly 9 to 25 m² on hulls 4 to 6 m long. The mizzen lets you balance the helm under reefed main, heave-to in a blow, and steer under sail alone — which is why builders like Iain Oughtred and Francois Vivier draw it for cruising dinghies such as the Caledonia Yawl and Ilur.
Skiff Yawl Rig Interactive Calculator
Vary main and mizzen sail areas, CE positions, and CLR to see combined CE and yawl helm lead.
Equation Used
The combined centre of effort is the area-weighted average of the main and mizzen CE positions. Lead is the distance from CLR to the combined CE; positive lead means the sail CE is aft of CLR. This compact calculator uses the worked example LWL of 4.6 m to express lead as percent of waterline length.
- Bow is the position datum and positive distance is aft.
- LWL is fixed at the worked-example value of 4.6 m for lead percent.
- Sail centres are geometric centres of effort.
- Target lead band shown is 5% to 10% of LWL aft of CLR.
How the Skiff Yawl Rig Works
The rig works by splitting the sail plan into two pieces with the mast division falling roughly 80/20 between main and mizzen. The mainmast carries the working sail — gaff, lug, sprit, or bermudan — and sits in the forward third of the hull. The mizzenmast is short, often 2.5 to 3.5 m on a 5 m skiff, and it steps abaft the rudder head. That aft position is the whole point. With the mizzen sheeted hard, the centre of effort of the combined sail plan shifts aft of the centre of lateral resistance, which generates a small steady weather helm. Sheet the mizzen out and the boat luffs up. Sheet it in and she bears away. You can sail and tack the boat without touching the tiller.
Why build it this way on a small boat? Because a skiff is open, often rowed and camped from, and you want hands free for anchoring, fishing, reefing, or heaving-to in a chop. With the main dropped and the mizzen sheeted flat, a yawl-rigged skiff sits 50 to 60° off the wind making about 0.3 knots of leeway — the classic heave-to position for reefing or eating lunch. A sloop the same size has no equivalent. You either keep sailing or you drop everything and drift.
Get the balance wrong and the rig fights you. If the mizzen is too large or stepped too far aft, the boat develops 8 to 12° of weather helm and rounds up in every gust. Too small or stepped too far forward and the mizzen does nothing useful — you carry the windage of a second mast for no balanced-helm benefit. Builders aim for the centre of effort no more than 0.10 × waterline length aft of the centre of lateral resistance at full sail, tightening to within 0.05 × LWL once you reef.
Key Components
- Mainmast and main sail: Carries 75 to 85% of total sail area. On a 5 m skiff that's typically 9 to 14 m² in a balanced lug or gunter cut. The mast steps in a thwart partner and a keelson step, with rake set between 0 and 3° aft to position the centre of effort correctly.
- Mizzenmast: Short unstayed spar, 2.5 to 3.5 m tall on most skiff yawls, stepped abaft the rudderpost. Mast diameter at the partners is usually 50 to 65 mm in solid spruce or hollow Douglas-fir. The location aft of the rudder is what distinguishes a yawl from a ketch.
- Mizzen sail: Carries 15 to 25% of total area, typically 1.5 to 4 m² on a small skiff. Cut as a leg-of-mutton or sprit-boomed sail with a free-standing luff. Used for helm balance, heaving-to, and steering when the main is stowed.
- Mizzen sheet and bumkin: The mizzen sheet leads to a bumkin — a short spar projecting 300 to 600 mm aft of the transom — to keep the sheet clear of the rudder. The bumkin must take the full mizzen sheet load, often 200 to 400 N in a fresh breeze, so it's typically 40 mm oak or laminated ash.
- Rudder and tiller: Sized normally for the hull, but the rudder head must clear the mizzenmast. Most builders offset the mizzen step 50 to 80 mm to port or starboard, or use a kick-up rudder with the stock forward of the mast.
- Centreboard or daggerboard: Provides the lateral resistance the rig balances against. Position is critical — the centreboard pivot pin or daggerboard slot location sets the centre of lateral resistance, and getting it within ±50 mm of design is the difference between a balanced boat and one that won't tack.
Who Uses the Skiff Yawl Rig
The skiff yawl rig shows up wherever sailors want a small, open, manageable boat that behaves itself when the crew has work to do. It's a working rig, not a racing rig — you'll find it on tenders, beach cruisers, fishing skiffs, and traditional small craft revivals from the UK, France, and the US east coast.
- Dinghy cruising: Iain Oughtred's Caledonia Yawl, a 5.8 m glued-lapstrake open boat with a 9.3 m² balanced lug main and 1.9 m² mizzen — one of the most-built amateur cruising dinghies in the English-speaking world.
- Small craft restoration: Francois Vivier's Ilur, a 4.5 m French-tradition skiff with a standing-lug yawl rig, sailed across the Channel and around the Brittany coast by amateur builders.
- Camp cruising and expedition rowing: John Welsford's Navigator design, a 4.5 m yawl-rigged centreboarder used for the Texas 200 and similar shallow-water raids.
- Traditional fishing tenders: Drascombe Lugger and Drascombe Dabber yawls, built by Churchouse Boats in the UK since the 1960s, used as estuary day-boats and yacht tenders.
- Heritage small craft: American Catspaw dinghy yawls and revived New England working skiffs displayed and sailed at Mystic Seaport Museum and the WoodenBoat School in Brooklin, Maine.
- Solo coastal cruising: Phil Bolger's Chebacco yawl variant, used by single-handed cruisers who need to heave-to and reef without leaving the helm.
The Formula Behind the Skiff Yawl Rig
The core sizing question on any yawl rig is where the combined centre of effort (CE) sits relative to the centre of lateral resistance (CLR). You want CE slightly aft of CLR to produce a small weather helm — too little and the boat is sluggish to tack, too much and she rounds up in puffs. At the low end of the typical lead range, around 0.03 × LWL aft, the helm feels neutral and the boat hunts in light air. At the nominal 0.06 to 0.08 × LWL the helm has a comforting 2 to 4° of weather pressure on the tiller. Push the lead beyond 0.12 × LWL and the boat fights you upwind in any breeze over 12 knots.
Variables
| Symbol | Meaning | Unit (SI) | Unit (Imperial) |
|---|---|---|---|
| CEcombined | Distance from a chosen datum (usually the bow) to the combined centre of effort of the sail plan | m | ft |
| Amain | Area of the mainsail | m² | ft² |
| Amizzen | Area of the mizzen sail | m² | ft² |
| xmain | Distance from datum to geometric centre of the mainsail | m | ft |
| xmizzen | Distance from datum to geometric centre of the mizzen | m | ft |
| Lead | CE position aft of CLR, expressed as a fraction of waterline length | m | ft |
Worked Example: Skiff Yawl Rig in a 5 m glued-lapstrake camp cruiser
Your amateur boatbuilding shop on Vancouver Island is finishing a 5.0 m glued-lapstrake camp cruiser to a Caledonia-Yawl-style sail plan. The hull has LWL = 4.6 m and CLR measured 2.30 m aft of the bow. The proposed rig is a 9.5 m² balanced lug main with its geometric centre 1.95 m aft of the bow, and a 2.0 m² leg-of-mutton mizzen with its centre 4.85 m aft of the bow. You need to verify the lead falls in the right band before you cut the mast partner.
Given
- Amain = 9.5 m²
- xmain = 1.95 m
- Amizzen = 2.0 m²
- xmizzen = 4.85 m
- xCLR = 2.30 m
- LWL = 4.6 m
Solution
Step 1 — compute the combined centre of effort at the nominal full-sail configuration:
Step 2 — compute the lead, which is CE aft of CLR expressed as a fraction of LWL:
That sits at the low end of the usable band. The boat will tack cleanly in 8 knots of wind but the helm will feel light, almost neutral, and you'll need to actively steer rather than letting her self-track.
Step 3 — check the reefed configuration, which is what really matters in a blow. With one reef tied in, Amain drops to about 7.0 m² and the main's centre lifts and moves slightly aft, say xmain,reefed = 1.85 m. Recompute:
That's healthier — under reef the helm picks up to roughly 3° weather pressure, which is what you want when the breeze is up. Now check the high end: if you also drop the mizzen and sail under main alone, CEmain-only = 1.95 m, which puts the lead at (1.95 − 2.30) / 4.6 = −0.076, a 7.6% LEE helm. The boat will refuse to come about and try to bear away in every gust. Lesson — a yawl needs the mizzen up to balance, even reefed.
Result
The nominal full-sail lead is 3. 35% of LWL, with the combined CE 2.454 m aft of the bow. That puts the boat at the light end of balanced — sailable and forgiving but with a softer helm than a Caledonia Yawl normally carries. At the reefed operating point the lead climbs to 4.7%, which is the sweet spot, while sailing under main alone collapses to a 7.6% lee helm that makes the boat unmanageable upwind. If your finished hull tracks differently than this prediction suggests, the usual culprits are: (1) centreboard pivot pin located 30 to 60 mm forward or aft of the drawing, which shifts CLR more than the rig math accounts for, (2) mainmast rake set wrong — every 1° of aft rake moves CE about 30 to 50 mm aft on a 4 m luff, and (3) the bumkin flexing under mizzen load and letting the mizzen twist off, which kills its balancing effect entirely.
When to Use a Skiff Yawl Rig and When Not To
The yawl rig is one of three sensible two-masted plans for a small boat, and it competes with the simpler sloop on the small-boat end and the bigger ketch on the cruising-yacht end. Here's how it stacks up on the dimensions a builder actually has to weigh.
| Property | Skiff Yawl Rig | Sloop (single mast) | Ketch Rig |
|---|---|---|---|
| Total sail area on a 5 m hull | 10–14 m² split 80/20 | 10–14 m² single sail plan | Not practical below 8 m hull |
| Helm balance under reef | Excellent — adjust mizzen sheet | Poor — fixed by sail shape only | Excellent — adjust mizzen sheet |
| Heave-to capability | Heave-to under mizzen alone, 50–60° off wind | Backed jib only, drifts faster | Heave-to under mizzen, slower drift |
| Rigging complexity | 2 masts, 2 sheets, bumkin, no shrouds typical | 1 mast, 1–2 sheets, shrouds and forestay | 2 masts plus full standing rigging |
| Build cost (amateur, 5 m hull) | £900–1,400 in spars and sails | £700–1,000 in spars and sails | Not applicable at this size |
| Windward performance | Moderate — mizzen backwinds main | Best — clean single sail plan | Moderate to poor — mizzen interference |
| Single-handing under sail | Excellent — steers on mizzen sheet | Tiller-tending required | Excellent on larger hulls |
| Mast intrusion in cockpit | Mainmast forward, mizzen aft of tiller — clear cockpit | Single mast in or near cockpit | Mizzenmast often through cockpit |
Frequently Asked Questions About Skiff Yawl Rig
Calculated lead assumes the centre of effort sits at the geometric centre of each sail at zero heel. The moment the boat heels past 15°, the main's CE swings to leeward of the hull centreline while the mizzen's CE swings less because it's smaller and lower. That asymmetric heel-induced moment generates a yawing couple that adds to weather helm — sometimes 6 to 10° on top of the static figure.
Quick fix — ease the mizzen sheet 100 to 200 mm in the puff before the boat heels. That depowers the mizzen first and unloads the helm. If the problem is constant rather than puff-driven, your mainsail is probably too full in the upper third; flatten it with halyard tension or reef earlier.
For a hull intended primarily to row and motor with sail as a secondary mode — go 15 to 18%. The smaller mizzen reduces windage when stowed and the boat behaves like a sloop with a balancer. For a hull intended to sail seriously with frequent reefing and heaving-to — go 22 to 25%. The larger mizzen does real work driving the boat, and you can sail home under mizzen alone if the main rips.
Drascombe Luggers run about 18%, Caledonia Yawls about 17%, Ilurs about 20%. Below 12% the mizzen is decorative. Above 28% you're really building a small ketch and the rig stops behaving like a yawl.
Free-standing mizzenmasts flex more than builders expect. A 60 mm spruce mast on a 3 m mizzen will deflect 80 to 120 mm at the head under a moderate sheet load, which slackens the luff because the mast tip is bending toward the clew. The sail then can't hold its shape and the luff flutters.
Two fixes — stiffen the mast (go to 70 mm solid or a properly tapered hollow spar) or move to a sprit-boomed mizzen where the sprit holds the peak out and pre-tensions the luff geometrically. Most traditional skiff yawls use the sprit-boomed mizzen for exactly this reason.
You can convert it, but you have to move the main forward, not just bolt a mizzen onto the transom. The combined CE of the new yawl rig must still land in the same place relative to CLR — typically 5 to 8% lead. Adding a 2 m² mizzen 4.8 m aft of the bow on a hull whose original sloop CE sat at 2.4 m will pull the combined CE aft by roughly 250 to 350 mm and the boat will refuse to tack.
Practical conversion — shorten the main by the same area you add as mizzen and step the mainmast 200 to 300 mm forward of its original position. Then re-measure CLR with the centreboard down and check the lead before you cut anything permanent.
Drop the main, sheet the mizzen flat amidships, and lash the tiller down to leeward (away from the wind). The boat will settle 50 to 60° off the true wind, fore-reaching at 0.2 to 0.4 knots and sliding sideways at about 0.3 knots. You should see the bow oscillate slowly through a 10 to 20° arc as the mizzen alternately stalls and re-attaches.
If the bow falls off past 70° or the boat gybes herself across the wind, your mizzen is too small or sheeted too loose. If the bow keeps shooting up into irons, the mizzen is too large or the tiller isn't lashed far enough down. The lashing position is the main control — adjust it 50 mm at a time until the boat settles.
Two reasons. First, the mizzen sits in the dirty air coming off the main's leech, so it's stalled or back-winded on most points of sail closer than 60° apparent. It contributes drag without lift upwind. Second, the split rig has more total spar windage and more induced drag from two smaller sails versus one larger one — the aspect ratio of each sail is lower.
Expect to give up about 3 to 5° of pointing angle compared to a sloop of equal total area. That's the trade you accept for the balance and heave-to benefits. If you need to point higher in a specific situation, ease or drop the mizzen entirely and sail as a cat-rigged single-master for that leg.
By definition, abaft the rudderpost — that's what makes it a yawl rather than a ketch. In practice on a 5 m skiff, the mizzen step sits 150 to 400 mm aft of the rudder stock. Closer than 150 mm and the rudder head fouls the mast or sheet. Further than 400 mm and you need a long heavy bumkin to carry the sheet, and the structural loads on the transom climb sharply.
Offset the mizzen step 50 to 80 mm to one side of centreline so the rudder tiller can sweep past the mast. Most builders offset to port because the helmsman traditionally sits to starboard. Check the geometry full-scale with the rudder hard over both ways before you commit the step location.
References & Further Reading
- Wikipedia contributors. Yawl. Wikipedia
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