Junk rig

The junk rig, also known as the Chinese lugsail, Chinese balanced lug sail, or sampan rig, is a type of sail rig in which rigid members, called battens, span the full width of the sail and extend the sail forward of the mast. While relatively uncommon in use among modern production sailboats, the rig's advantages of easier use and lower maintenance for blue-water cruisers have been explored by individuals such as trans-Atlantic racer Herbert "Blondie" Hasler and author Annie Hill.

Etymology

The English word "junk" comes from Portuguese junco from Malay jong. The word originally referred to the Javanese djong, very large trading ships that the Portuguese first encountered in Southeast Asia. It later also included the smaller flat-bottomed Chinese chuán, even though the two were markedly different vessels. After the disappearance of the jong in the 17th century, the meaning of "junk" came to refer exclusively to the Chinese ship.

History

The origin of the junk sailing rig is not directly recorded. The Chinese adopted the sail design from other cultures, although the Chinese made their own improvements over time. Paul Johnstone attribute the invention of this type of sail to Austronesian peoples from Indonesia. They were originally made from woven mats reinforced with bamboo, dating back to at least several hundred years BCE. They may have been adopted by the Chinese after contact with Southeast Asian traders by the time of the Han dynasty. However, Chinese vessels during this era were mostly fluvial while others were made to cross shorter distances over the seas ; China did not build true ocean-going fleets until the 10th century Song dynasty. The Chinese were using square sails during the Han dynasty; only in the 12th century did the Chinese adopt the Austronesian junk sail.
Sinologist Joseph Needham also argues that Chinese balanced lug sails developed from Indonesian tilted sails. Iconographic remains show that Chinese ships before the 12th century used square sails. A ship carving from a stone Buddhist stele shows a ship with square sail from the Liu Sung dynasty or the Liang dynasty. Dunhuang cave temple no. 45 features large sailboats and sampans with inflated square sails. A wide ship with a single sail is depicted in the Xi'an mirror.
Needham thinks a ship in the Borobudur relief may have been the first to depict a junk sail. The ship is distinct from the reliefs of other ships and could be the oldest depiction of a Chinese seafaring ship. This is disputed by D.A. Inglis, who concluded that the ship described was more like Indian Ocean ships operating from Arabia and South Asia after conducting an on-the-spot investigation of the relief. The ship has protruding deck beams, a single mast, and a square sail that has a yard and boom.
The oldest depiction of a battened junk sail comes from the Bayon temple at Angkor Thom, Cambodia. This depiction may feature a Chinese ship, but this is disputed by Nick Burningham, who points out that the ship had a keel and that Chinese ships generally did not have a sternpost. The rudder has a thin blade, different from the Chinese rudder which usually has a long blade. These characteristics may suggest a quarter rudder mounted on the beams of the rear gallery. From its characteristics and location, it is likely that this ship is a Southeast Asian ship.

Junk sail rigged boats

As the origins of the junk sail remain unknown, no particular rig can claim to be the original or correct way to rig a junk sail. Some sailors have demonstrated the junk sails ability to work even in the presence of some standing rigging, such as the Colvin rig, although more care must be taken to prevent damage while sailing.
Some ships that have been known to use junk sails include:

Casco, a flat-bottomed barge originally used by the Tagalog people along the Pasig River and Manila Bay.
Tongkang or "Tong'kang". A light boat used commonly in the early 19th century to carry goods along rivers.
Twakow, a type of vessel with one mast and junk rig. They were a common sight in the Singapore river in the mid-19th century.
Djong, a ship with pointed hull, some are equipped with bowsprit and bowsprit sail.
Bedar, a type of ship from Malaya.
Pinas, a Malay ship, originally rigged with schooner rig.
Lorcha, a light Chinese sailing vessel. This ship combined a western-style hull of Portuguese influence, with Chinese-style mast and sail. The lorcha were found in the Gulf of Siam and in Philippine waters as well. The Vũng Tàu shipwreck consists of the remains of a late 17th-century lorcha from the South China Sea off the islands of Con Dao, about 160 km from Vũng Tàu, Vietnam.

There is no one specific junk sail plan and various designs exist. Square headed junk sails have parallel yards and booms and resemble rectangles. Fan-headed junk sails have yards angled forward at varying degrees. Split panel junk sails separate the sail plan in two sections, a main section behind the mast, and a smaller section forward the mast. This is done in an effort to mimic the effect of the "slot" created by separating the headsail and mainsail in Bermuda rigs, although the benefits of the "slot effect" are disputed. Hybrids between a Bermuda sail and junk sail exist as well, attempting to join the junk sail rigs ease of use with tried and true Bermuda triangular sail plans, some examples being the Aerorig and Aerojunk.

General sail construction

Sail terminology

The junk sail has essentially the same sides and corner names as the traditional gaff rigged four-corner sail.
Knowing the names of the sides and corners help understand the running rigging and sail trim of the junk sail.
The four corners of the junk sail are:

the peak or the top corner;
the throat down the yard from the peak, close to the mast.
the tack at the base of the mast and boom, which is "tacked" on to the boat and does not move.
the clew at the end of the boom, connected to the sheet.

The four sides of the junk sail are:

the head or top edge of the sail.
the luff or front of the sail, the first part of the sail to "luff" or shake when sailing too close to the wind.
the foot at the bottom, connected to the boom.
the leach or trailing edge of the sail, where wind telltales might be found.
Sail components

A junk sail requires the following parts:

The sailcloth material can be as simple as woven plant material, light canvas, tarpaulin, ripstop nylon, Dacron, or anything wind cannot permeate. Camber, or shape, can be added in to junk sail panels in order to increase the possible performance on all points of sail, though doing so reduces the rigs simplicity and increases stress loads. It is unknown if ancient junk sails were constructed using cambered panels, flat panels, or if the panel material itself developed its own shape.
The yard supports the head of the sail from the throat and peak. The yard is usually stronger relative to the battens because it supports the full weight of the sail. It also elevates the peak of the sail on fan headed junk sails.
The battens support the sail from luff to leech. Batten materials that easily allow some bending while maintaining strength work best, such as bamboo and fiberglass,
The boom is the spar at the foot of the junk sail. It supports the sail directly at the tack and the clew, and holds the sail assembly down at the tack using the tack line.
The batten parrels are lengths of line or strap that hold the sail to the mast. They can be quite long in rigs which allowing the fore and aft movement of the sail across the mast. Such controls allow the sail to be centered on the mast for more stable downwind sailing.
the tack parrel holds the boom to the mast.
The tack line holds the boom down towards the deck and if adjustable is considered running rigging.
Sail controls

The running rigging controls the junk sail.

The halyard raises the sail up the mast. It is usually connected to the middle of the yard.
The yard hauling parrel holds the yard close to the mast. It runs from the yard around the mast, and down to the deck. The yard hauling parrel helps control the fore and aft movement of the sail in conjunction with the tack parrel, tack line and luff hauling parrel, but is not used on all junk sail rigs.
The luff hauling parrel, is rigged from the luff of the sail at the battens to the mast in shoestring fashion such that when it is hauled, it will pull the middle battens aft but this is not a necessary part of the rig.
The topping lift, also called "lazy jacks", holds the boom and sail up off the deck when the sail is not raised. The topping lift also serves to tame the junk sail, acting as a cradle while hoisting and lowering and is also not an essential part of the junk sail rig.
The sheets control of the trim of the sail. In some junk sails the sheets are connected to both the boom and multiple battens. Doing so enables a flat cut junk sail to improve windward capabilities by tensioning some battens more than others which encourages bending that creates shape in a flat cut sail. In such a setup the multiple sheets connected to battens often join together in some way, called a euphroe which is a long piece of wood with holes in it, that enables a single line to trim the sail like modern Bermuda rigs. Ship designers Tom Colvin, Michael Kasten and Herbert "Blondie" Hasler employed such a technique, but others such as Derek Van Loan and Phil Bolger simplified the design without euphroes. Cambered junk rigs are generally sheeted directly to the boom, as extra shape is not necessary.

An interesting side note is that a small Bermuda rig sail can be constructed from a single cut, out of a single cloth, and still sail effectively. A junk sail, by definition, requires multiple individually cut panels sewn together.