Rearrange the Whole Rig

A conventional square rig turns its yards around a mast that remains fixed in the hull. A conventional mainsail turns with its boom while the mast supports its luff. We have changed sail outlines, added upper sails and divided the work among masts. Another choice changes which parts move together.

The mast itself can turn. A spar can carry sail both ahead of and behind that turning axis. Several yards can become fixed branches of one rotating structure. Each change alters the joints and controls through which the crew manages the rig. Before examining those arrangements, we need to distinguish moving something with power from making it reach a chosen position.

Ask for movement, measure the result

Imagine a crew choosing an angle for a powered rotating rig. The control sends a command to turn, and an electric motor supplies movement. The motor and its drive are the actuator: the part of this system that converts its energy input into the required mechanical motion. A button supplies the request; it does not supply the substantial energy needed to turn the loaded rig.

The turning shaft still needs bearings, and the motor needs an attachment that resists its reaction. If the motor’s body could turn freely with the shaft, its action would not produce the intended movement relative to the boat. The mounting carries that reaction into the supporting structure, just as a winch’s mounting answers the crew’s pull and handle torque.

Now measure the angle actually reached. A sensor converts a physical quantity into a usable indication: here, shaft position becomes an electrical signal. Returning that indication to the controller provides feedback, information about the system’s actual response. The controller compares the measured angle with the target and commands further movement in the appropriate direction until the discrepancy is within the system’s intended tolerance.

The sequence has three distinct routes. A command specifies the desired movement. Energy powers the actuator. Information reports what happened. A motor could run for a fixed interval without any measurement of the resulting angle; adding the returned measurement lets the controller correct the result instead of assuming that the request was fulfilled.

Mark Neal’s 2006 sailing-robot experiment supplies a small built example. Its wing shaft ran in a bearing tube. An electric motor drove the shaft through reduction gears, while a bracket and the boat’s internal structure carried the reactions. A position sensor coupled to the output shaft reported its angle. This was a potentiometer: rotation changed an electrical resistance, allowing the electronics to measure position. A separate masthead wind vane sensed wind direction.

That boat carried no crew. Our crew-selected target is an imagined use of the same positioning principle. In the reported lake trials, the wing stayed at a fixed angle for each sailing leg while a separate rudder control corrected the boat’s direction relative to the wind. The experiment demonstrated particular control jobs, rather than a system continuously discovering the best wing trim or proving ocean endurance.

An angle sensor can show that the rig has reached the chosen angle. It cannot tell us whether that angle suits the conditions. Choosing appropriate sail area, judging the conditions and deciding what the vessel should do remain separate responsibilities. Later, the same actuator–sensor–feedback distinction will help us understand powered winches and steering systems, including the different ways windvanes and electronic controls obtain information and move a rudder.

Turn the mast without losing its support

A rotating mast turns about its lengthwise axis. Its leading and trailing sides change their orientation to the apparent wind, and the sail attached behind it follows the changed alignment. The mast’s overall lean need not change. This movement is rotation about the spar, rather than the mast raking bodily forwards or aft.

The support and the turning drive have different jobs. Bearings carry the mast’s loads while allowing the specified rotation. A sheet, a control arm or powered machinery can set its angle, depending on the arrangement. Identifying a rotating mast therefore leaves two useful questions: where does its load go, and what turns or restrains it?

Eric Sponberg’s account of the Freedom 38 Wobegone Daze answers the first through a particular construction. A carbon outer mast turned around a fixed carbon stub rising from the hull. Two separated bearings between shell and stub carried their contact forces while permitting rotation. The shell passed sail loads into the stub and thence into the boat. This was a free-standing, or unstayed, rig: it relied on that mast-and-hull structure rather than external shrouds to provide the principal support. His construction drawing shows the components separately.

Removing stays changes the support route; it does not remove the bending moment or the need for strong local contacts. A stayed mast can also be designed to rotate, provided its rigging connections allow the required movement. Conversely, a free-standing mast can remain fixed. Stayed versus unstayed and fixed versus rotating are independent descriptions.

The mast section now has an aerodynamic as well as a structural consequence. A wing mast has an elongated, aerofoil-like section that contributes to the working aerodynamic surface alongside the cloth. Turning it can bring its after portion into better alignment with the sail instead of leaving a broad obstruction ahead of it. Pressure acts on the mast’s own exposed surface too, so the combined force and its point of application belong to mast and sail together.

Sponberg used an elliptical section in the rotating shell. Its carbon mast wall had to carry bending and transmit bearing reactions as well as provide that outside shape. A useful external outline alone says little about wall thickness, reinforcement or resistance to local crushing. His reported difficulty turning the bearings under load also shows why an apparently free movement must be considered in its loaded condition; he suspected deformation of their bearing material, rather than establishing a universal fault in rotating masts.

Keep three descriptions from the mast chapter separate. Mast rake describes the overall inclination of the heel-to-head reference. Mast bend describes curvature under the condition being considered. Prebend is the initial curvature established before the changing sailing load. Turning an already curved mast changes the orientation of that curve relative to the boat; it does not, by itself, specify a new amount of curvature. Section shape, wall construction and support determine how the spar then responds to its changed loads.

The fittings must also fit the movement. At the masthead, a crane projecting beyond the spar still carries an offset load; a masthead crane used to keep a connection clear must retain that clearance through the intended turning range. If fixed to the moving mast, the arm moves with it. Its mounting still receives the turning effect of the offset pull.

Take the boom around both sides

A wishbone boom replaces a single lower spar with two curved arms. From the forward support near the mast, one arm passes along each side of the sail. They join aft, where the clew attaches. Their outward curvature leaves room between them for the sail’s belly; their joined end locates the clew and carries its pull back through both arms.

In the Nonsuch 30, the wishbone sits high above the deck, with the mainsail’s tack low on the unstayed mast and its clew at the wishbone’s after end. The mainsheet controls that end’s sideways position. A separate choker line has a fixed end on the mast, leads to the wishbone’s forward end and then aft for adjustment. Hauling it moves the wishbone aft and tensions the sail towards the clew, flattening the lower shape.

Lines beneath the arms form a cradle that receives the lowered cloth. These are the arrangements described in Ed Lawrence’s 2006 sailing account, rather than a claim that every wishbone has the same reeving.

Wishbone rig names a rig through this characteristic sail-control spar. Nonsuch combines it with one principal sail and one forward, free-standing mast, so its cat-rig description remains useful too. The two labels answer different questions. The forked boom does not prescribe the mast count, require the mast to rotate or establish a pair of sails balanced around it.

The Nonsuch designer Mark Ellis described combining an influence from the 1930s Ljungström free-standing arrangement with a windsurfer-style wishbone for better sail control. That is a documented design connection, not evidence that every forked sail spar descends from this yacht. The practical change is visible in the structure: the two arms make room for the cloth while bringing its after-corner load to a controllable support.

Put sail on both sides of the pivot

Sail force acting behind a turning axis tends to rotate the assembly one way. Put some working area ahead of that axis and its force can contribute a moment the other way. A balanced sail uses this geometry: part of its area lies ahead of the mast or selected pivot. We have already met the forward-projecting area of a balanced lug. Here the same principle helps explain a complete rotating assembly.

A balestron rig has a spar extending both forward and aft of a common pivot. In the main-and-jib arrangement, the after portion carries the mainsail’s lower support, while the forward portion carries the headsail’s forward attachment. The mast, spar and sails turn together. Unlike the usual jib whose tack stays at the bow while its sheets change sides, this jib moves bodily with the rotating structure.

The forward sail’s pull can partly oppose the turning moment of the after sail. The controlling sheet then answers their remaining combined moment. Their forces still reach the mast bearings and hull, even when the net turning demand is modest. Reefing one sail more than the other changes that balance. The complete yacht also has its earlier balance problem between aerodynamic and underwater forces; reducing torque about this mast does not make the boat self-steering.

AeroRig is a named implementation of that rotating main-and-forward-sail arrangement. North Windships describes its free-standing mast, rigid forward and after boom structure and shared working sheet. Richard Woods’s account of sailing the AeroRig-equipped Savannah 26 in October 2000 gives a delivered example of the geometry, while the supplier’s 2026 account describes continuing commercial development. The generic balestron arrangement and the named system should remain distinguishable; neither a carbon mast nor a clear deck identifies the supplier’s particular rig.

This also explains why the wishbone is a different choice. Its arms pass to either side of the cloth and join behind it. The balestron’s important extension is ahead of and behind the pivot. One describes how a spar surrounds and controls a sail; the other describes the shared rotating geometry and its force moments. A designer can combine properties, but the names do not make them interchangeable.

Change where the support stands

Move the main support far aft and substantial sail area can hang ahead of it. This is the defining arrangement of a mast-aft rig. The long forward supports become particularly important: their upper pulls enter the after mast, while their lower attachments pull on forward regions of the hull.

Brian Eiland’s mast-aft proposal, developed in the 1970s, provides a specific example. Its single mast stands well aft and leans forwards. Two stays extend from it towards separate forward attachments and support two sails ahead; a smaller after sail is carried from an aft stay. The stays retain the sails’ leading edges and transmit their loads to mast and hull. The supporting structure must answer those tensions as well as the sails’ changing sideways force. Eiland identified the published concept as unbuilt, and its sketch did not show a complete standing-rigging design.

That aft position is independent of balestron balance. The proposal’s forward sail attachments belong to the hull-supported stay arrangement, rather than a shared forward boom rotating with the mast. Mast-aft also states neither a mast material nor an automatic change in how the yacht balances about its underwater resistance.

Another support uses two inclined legs that meet above the deck. Each leg reaches its own lower attachment, producing an A-frame mast. Sail-support loads entering the upper structure pass down the legs to separated hull contacts. The legs and cross-connections must work together as a frame; the wide lower separation is part of its load-resisting geometry.

Greenpeace’s Rainbow Warrior III, in operation from October 2011, has two such assemblies. Its owner calls the sail plan a staysail schooner with two A-frame masts. Counting the legs as four ordinary masts would conceal how the supports work: each joined frame serves as one mast assembly. The owner’s photograph and specification give a delivered example of this support geometry combined with a familiar distribution of sails.

The frame itself need not rotate. Equally, a rotating structure can use more than one supporting member internally. To understand either, follow the actual joints and feet, rather than infer the whole rig from the letter A.

Give the aerodynamic surface thickness

An aerofoil is a section shaped to produce useful lift in airflow. Our flexible sails already take curved sections and act aerodynamically. A wing-shaped mast changes their leading support; a wingsail extends the shaped construction across the working surface. Its finite span, loading, angle to the apparent wind and losses still matter. Calling it a wing introduces no separate source of propulsive force.

A rigid wingsail holds its section through a built framework and covering. The framework supports the surface between its attachments, and the assembled wing transfers the aerodynamic load into its root and supporting rig. It can retain thickness and a specified profile without relying on a freely hanging sheet of cloth to form the whole section.

SailGP’s F50 has a main wing element and an after flap. Changing the flap’s angle relative to the forward element changes the section’s camber; changing the orientation of the wing as a whole changes its angle to the airflow. These are distinct controls. Its 2026 technical guide also identifies a dedicated human wing trimmer and a jib ahead. The wing has not absorbed every sail or the crew’s trim decisions.

The F50’s modular construction allows wing sections to be joined with bolts, electrical connections and hydraulic connections carrying pressurised fluid before sailing. Selecting and assembling those rigid modules ashore differs physically from lowering a cloth sail and tying in a reef. The assembled structure must be raised into place and supported; its covering cannot simply gather down a mast while the complete rigid framework remains aloft.

A soft wingsail obtains a thick section from flexible or partly flexible surfaces supported by internal members. Ilan Gonen’s Omer system uses two cloth mainsail faces and a separate U-shaped cloth leading edge. Each face slides up a leg of its rotating A-frame support, while the leading edge rises in tracks ahead of it. The supporting frame separates the faces, and battens maintain their curved shapes. The cloth components can be lowered and reefed.

Omer’s whole frame turns at its hull support. It therefore differs from Rainbow Warrior’s two fixed frame assemblies and their separate staysails. Here the multiple members support the two sides of one wing surface; the internal frame’s geometry belongs to that sail, rather than specifying a schooner or a mast-aft arrangement.

Omer controls camber by changing the angle between the boom and the leading edge. The resulting movement bends the battens and reshapes the two faces. Its documented cylinder extends or retracts a rod to supply this movement, while the mainsheet controls the whole wing’s orientation. Reversing the camber makes the appropriate curve for the other tack. The maker’s construction and control account separates the shape adjustment from the sheet adjustment; a powered change of shape still needs a chosen setting.

A twin-skin mainsail likewise has two flexible faces, but that description leaves its support details open. In Luna Rossa’s 2021 AC75, the two mainsail skins were hoisted in parallel behind a rotating D-section mast. The rounded forward part of the D formed the leading edge; the skins extended aft from its two sides, with full battens supporting their shapes. Mast and cloth together formed the thicker aerodynamic section.

The crew could rotate the mast and operate familiar shaping controls, including the outhaul and the Cunningham luff-tension control, through powered mechanisms. Moving the lower after attachment altered the cloth’s tension and depth; changing luff tension altered its shape against the mast. Those adjustments acted on flexible skins and battens, unlike turning the F50’s discrete rigid after flap. Luna Rossa’s dated account of its sail system describes the controls as well as the paired hoist.

The later AC75 rules published in March 2022 required continuous attachment of each skin to the mast over most of its luff and required the mainsail to lower with the mast still stepped. The retained leading edges therefore carried load while permitting deployment; two skins did not mean two masts or two independently complete rigs. Burns Fallow’s firsthand account dates the choice of this AC soft-sail approach to the weeks after the 2017 Cup, when the designers sought a wing-like solution using flexible sails. That particular development does not establish that all double-surface wings share one invention history.

Compare the properties separately. The Bermuda mainsail, historically called Marconi in some accounts, puts a flexible triangular surface behind its mast. A wing mast enlarges the shaped leading member. A wishbone boom supports a clew between its two arms. Omer and the AC75 add separated flexible faces by different constructions, while the F50 preserves much of its profile in a rigid assembly. None of these descriptions alone determines aspect ratio: compare span squared with the area of the actual surface being considered, using consistent boundaries for mast and sail.

Rotate the square-sail stack as a unit

Return to the conventional square rig. Its yard is supported at the mast, its braces change orientation, its sheets extend lower corners, and its gathering lines bring cloth towards the yard. DynaRig redistributes those jobs through a mast that rotates with fixed, curved yards. The yards retain their positions relative to one another instead of being independently braced around a fixed mast.

Sail panels extend between successive curved supports. Their top and bottom edges follow the yards, which establish curvature across the rig. When set, the separate panels make a largely continuous working surface. Turning the mast turns the entire supported stack; the relative yard angles no longer need a separate brace adjustment at each level.

The engineering team for Maltese Falcon described the sail handling in its 2004 project paper. The cloth rolled around a vertical mandrel inside the mast. Powered outhauls drew its outer corners out along the yards, with the head and foot edges sliding in retaining tracks. Reversing deployment returned the cloth to the mast. The mandrel drive and the outhaul drives did different jobs, and friction at the retained edges remained a real load for the machinery to overcome.

Support was equally physical. Separated deck and heel bearings passed the rotating mast’s reactions into reinforced hull structure. The 2004 design used geared hydraulic motors to turn the mast; their reaction restraints connected the drive assembly back to the hull. Rotation, sail deployment and structural support were therefore three mechanisms working together, even when their controls appeared together at one station.

Those details came from a project still undergoing development and testing. Dykstra’s account dates Maltese Falcon’s first sea trial to June 2006, with three free-standing carbon masts carrying five individually handled sails each. The designer’s delivered-vessel record and the rig maker’s architecture description establish the realised arrangement; they do not turn every detail of an earlier test design into a universal DynaRig specification.

The history connects a changed mechanism to its enabling construction. Wilhelm Prölss had explored the rotating square-sail concept in the 1960s. The Maltese Falcon team described the difficulty of making a mast with a long sail-storage opening retain the required structural stiffness. Carbon construction, developed bearings, powered drives and extensive testing helped turn that idea into this yacht’s working rig. It was an engineering development within square sailing, rather than a new name for all square-rigged vessels.

The builder’s Maltese Falcon sail plan shows each mast continuing through its yard levels without separately seated upper stages. A polacre already offered continuous spars with independently worked yards; DynaRig adds fixed curved yards, whole-mast rotation and internal sail storage. Those linked changes distinguish its machinery more usefully than the height or outline alone.

Look also at what the yard must hold. A conventional crossjack can receive the sheets of the topsail above even when it carries no sail of its own. DynaRig’s intermediate yard supports the retained edges of adjacent panels. Those are different attachments and ways of restraining the cloth, despite both yards lying below an upper square sail.

The conventional spanker had its own gaff and boom, with its luff carried on a separate trysail mast beside the larger mizzen. Those supports let its fore-and-aft sail be hoisted and worked beside the square stack. DynaRig instead carries its panels between fixed yards on the same rotating mast, with their edges retained on those supports. The change integrates sail support and whole-stack orientation, rather than keeping a separately supported after sail alongside independently worked square yards.

Its handling changes the crew’s normal access job too. A conventional footrope carries people standing beneath a yard, and its stirrups suspend that rope from the spar. The in-mast gathering system removes the routine need for a crew to stand along each yard and hand-furl its sail. Inspection, repair and maintenance aloft still need access; removing the normal hand-furling task does not make the upper structure maintenance-free.

Area selection now happens mainly inside those fixed boundaries. Instead of rigging temporary studding sails, ringtails or watersails beyond the ordinary working cloth, the crew deploys or gathers selected panels through their drives. Each choice changes which supported edges are loaded and which lengths of cloth occupy the mast’s store.

Whole-rig classification still answers the separate question of allocation. Brig, ship, barque, barquentine and the period brigantine conventions tell us what the principal masts carry. DynaRig tells us how its square units are supported, turned and gathered. Maltese Falcon is a square-rigged yacht whose control system changes the work behind that familiar description.

Finally, distinguish the systems that rotate. AeroRig’s balestron joins forward and after sails around one pivot, using their partly opposing moments to reduce the net turning demand. DynaRig joins square yards to a mast and takes its torque through the designed drive. A rotating wing uses its chosen section and shaping controls. Balanced sail area, mast position, support construction, power and feedback remain separate properties, with separate evidence needed for each.

We can now read a rig as connected choices rather than a single family name. The next question concerns the rig in use: how do its controls change the loaded sail’s shape as the wind and the boat’s motion change?