Junk Rig
From Wikipedia, the free encyclopedia
The Junk rig, also known as the Chinese lugsail and Sampan rig, is a type of sail rig in which the sail is fully battened (rigid members span from the luff to the leech) and partially balanced (some of the sail extends forward of the mast and some extends aft of the mast.)[1][2]
The junk sail can be trimmed in either the fore and aft manner for sailing into the wind, or in the square rigged manner for sailing with the wind in the trade winds.
The junk rig takes its name from the ancient and traditional Chinese junk ship, where it was used extensively throughout Chinese history.
The junk rig is rare in modern sailing due to the popularity of the Bermuda rig in modern production sailboats. The modern junk rig is somewhat more common among blue water cruisers due to the rig's low cost and easy sail handling.
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[edit] Traditional Chinese junks
Junks are efficient and sturdy ships of great proportions that traveled across oceans as early as the 2nd century AD. The design is a tradition of China and has endured throughout its history:
- 2nd century (Writings of the Han Dynasty documented ships capable of carrying 700 people together with 260 tons of cargo)
- 10th-13th century (Documents from the Song Dynasty show great trading ships of commerce and of military capability such as those used in the Mongol invasions of Japan)
- 14th century (Western documents confirm the specs of massive junk ships of the Yuan Dynasty)
- 15th-17th century (Huge fleets of specialized junk ships from the Ming Dynasty are documented in the excursions of Admiral Zheng He)
- 19th century (Ships of the Qing Dynasty such as the Junk Keying shown above were appreciated by Western ship builders for their speed and storm keeping properties)
[edit] Modern junk sail rigs
[edit] Types of modern rigs
Each of the traditional sailing rigs can be achieved using the modern junk sail.
- the catboat, characterized by its single mast and sail, is easiest to handle and is most likely seen on sailing dinghies and small boats, including the sampan.
- the ketch, characterized by a two mast configuration with the largest main mast forward and the smaller mizzen mast aft. Both sails in the ketch are driving sails. For larger boats, this breaks down the sailing canvas into two smaller panels that are easier to handle compared to one huge sail.
- the yawl, characterized by a two mast configuration with the largest mast forward, is distinguished from the ketch by the smaller size of the mizzen mast, typically aft of the rudderpost in traditional sailing craft, but is not a driving sail. The mizzen mast is used to assist steering the boat and balancing the helm.
- the schooner, characterized by a two or three mast configuration, with the smallest mast forward and the main mast aft. The schooner rig is suitable for larger boats because it breaks down the sail into smaller canvas which is easier to handle.
- the ship rig, consisting of at least 3 masts, is suitable for the largest sailing craft. Modern junk rigged ships have multiple masts of equal size, where traditional Chinese sailing junks have 3 masts with a dominating main mast in the center.
[edit] Junk sail components
The junk sail is a low tech approach to sailing and requires only inexpensive components. Spars are typically of wood. Lines for running rigging are typically 3-strand cordage rather than dual core braid. The sailcloth materials are typically light canvas or tarpaulin, used Dacron from discarded sails, or even PVC sheeting.
The junk sail is composed of the following components:
- the yard in context with the modern junk sail is the supporting spar along the head of the sail from the throat and peak. The yard is a stout spar relative to the battens because it supports the full weight of the sail when the halyard is hauled and the sail is raised. It also elevates the peak of the sail when trimmed.
- several battens support the sail from luff to leech. A fully battened sail is quiet and steady during raising and reefing, making the junk sail a convenient cruising sail. The battens also make the junk sail rather flat, which detracts from the efficiency of sail drive in light and moderate winds, but is ideal in the trade winds.
- 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 junk sail assembly down due to the tack line or downhaul. In modern rigs, the boom is connected to the sheets and is responsible for controlling the mailsail trim. However in the junk rig, the boom is partially in control of the trim of the sail because the sheets are connected to the junk boom and several of the the junk battens.
- the sailcloth panels in the junk rig do not need to be expensive low stretch materials as is required in modern sails. The junk sail makes a substantial driving force from a huge sail area, as opposed to the high efficiency curves built into small modern sails that depend upon Dacron, Mylar, or Kevlar to hold their shape.
- the batten parrels are short lengths of line or strap that are responsible for holding the junk sail to the mast. They are quite long, allowing the fore and aft movement of the battens across the mast under the control of the running rigging.
- the tack parrel and tack line secure the tack of the junk sail. The tack parrel will hold the tack into its horizontal position (parallel to the deck) and the tack line will hold the tack in its vertical position (down to the deck). The tack parrel and tack line can be rigged with either standing or running rigging. The later, if chosen, will rarely be adjusted.
[edit] Junk sail assembled
The junk sail has essentially the same sides and corner names as the traditional gaff rigged 4-corner sail. Knowing the names of the sides and corners help understand the running rigging and sail trim of the modern junk sail.
The 4 corners of the junk sail are:
- the peak or the top corner;
- the throat down the gaff 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; and
- the clew at the end of the boom, connected to the sheet.
The 4 sides of the junk sail are:
- the head or top edge of the sail;
- the luff or front of the sail, would be the first part of the sail to "luff" or shake when sailing to close to the wind;
- the foot at the bottom, connected to the boom; and
- the leach or trailing edge of the sail, where wind telltales might be found.
[edit] Running rigging
The running rigging for the modern junk rig can be divided into two groups -- the "pull ups" and the "pull downs." This is important because the action of hauling one line in a group will be resisted by the opposite group. For example when raising the sail via the halyard, the pull-downs must be uncleated and free to run.
The running rigging which pulls up the junk sail are:
- the halyard, whose purpose is to raise the junk sail up the mast. It is connected to the middle of the gaff, runs up to a block on the mast, and down to the deck. Because it hoists the full weight of the junk sail assembly, the halyard is often rove in a multipart purchase (3:1 or 4:1) via block and tackle;
- the topping lift, whose purpose is to hold the boom and junk sail up off of the deck when the sail is not raised. The topping lift also serves to tame the junk sail during reefing and dropping because the spars and sailcloth will all drop into the cradle of the topping lift.
The running rigging which pulls down on the junk sail are:
- the yard hauling parrel, whose function is to hold the junk sail yard close to the mast. It runs from the yard around the mast, and then down to the deck. The yard hauling parrel will control the lateral movement of the higher battens along the mast;
- the luff hauling parrel, whose function is to tame the wrinkles in the junk sail cloth as a result of the middle battens creeping forward when the sail is trimmed. It is rigged from the luff of the sail at the batten to the mast in shoestring fashion such that when it is hauled, it will pull the middle battens aft;
- the yard downhaul, whose optional function is to assist lowering the junk sail when it will not fall of its own weight;
- the batten downhaul, whose function is to assist lowering the junk sail in addition to the yard downhaul;
- and, the tack line, whose purpose is to secure the tack of the junk sail assembly in the vertical direction. It typically runs from the boom down to the deck or a block on the deck.
The running rigging that sets or trims the junk sail (controls the angle of attack relative to the direction of the wind) is the sheet. On a traditional Chinese junk rig, the sail is controlled by sheetlets -- small sheet lines running from the battens to blocks that in turn are on lines running through a euphroe, a long piece of wood with holes in it. This helps maintain uniform tension in each panel of the sail. Western ship designers Tom Colvin, Michael Kasten and H.G. Hasler use the same technique, but others (such as Derek Van Loan and Phil Bolger) use a simplified design without euphroes[1], [2].
[edit] Sail handling for the modern junk rig
Sail handling on the junk rig is ideal for cruising sailors, particularly when sailing short-handed.
There is no need to point "head to wind" when raising sail. When the sheets are sufficiently eased, the junk sail will rotate around the mast to any point of the wind. While sailing dead down wind is inconvenient for making sail, it is still possible to raise the junk sail with the sail luffing.
To raise the junk sail, start by easing the sheets until the furled sail is blown down wind. This will take the pressure off the sail and ease the raising. Then it is important to watch the lines that will run in while the sail is raised, including the gaff hauling parrel, luff hauling parrel, the downhauls if equipped, and the sheets. Hauling the sail with a 3:1 or 4:1 purchase will ease the burden, but the length of halyard will consequently be very long. The fully battened sail will remain calm in the lee of the mast during the hauling. Due to the weight of a huge canvas sail and its many spars, some junk sailors find a winch is needed for the last few feet. There is probably already a standing tack line in place, so the halyard is hauled until the tack line is taught, although there is no need to tighten up the leech severely to avoid scallops as in trimming the triangular sails. After hauling and securing the halyard, the fore and aft position of the leech is set by hauling the yard hauling parrel until the halyard is close to the mast. A short pull on the luff hauling parrel may be needed to extend the middle battens toward the leech to control wrinkles in the sail. The last act is to haul the sheets and set the sail to the wind.
Reefing a junk rigged sail is very easy. When sailing close to the wind, all that is needed is to ease the halyard. As the sail lowers by its own weight, the other running lines will also relax. The sail is lowered until the desired batten is along the boom. Then the gaff hauling parrel and luff hauling parrel are trimmed, and the sheet is hauled to reset the sail to the wind. When reefing on other points of sail, it is helpful to ease the sheet first to take the pressure off of the sail, and then ease the halyard and trim the other running lines. When sailing dead down wind, it may be helpful to use a downhaul to reef larger sails.
Emergency furling is fast and simple. When the sheets and halyard are let go, the sail will blow down wind, drop into the cradle of the toping lifts, while being steadied by the full battens. While this is fast and easy, it will also make a mess of the halyards, boom hauling parrel, yard hauling parrel, and downhauls. They will have to be put in order before raising the sail again. For non-emergency furling, it is preferable to drop the sail with two crew so that the slackening lines can be hauled in and maintained in order. Alternatively, a single-handed sailor can lower the sail in stages and attend to the slack lines.
[edit] Points of sail
The junk rig brings unique characteristics to each point of sail.
When close hauled, the junk sail rig comes under harsh criticism. In a racer/cruiser world that favors speed and sport, the criticism is quite valid. The junk sail is very inefficient when sailing up wind. The rig cannot "point" as close to the wind, and the craft looses ground by sailing a longer path. In addition, the sails do not generate as much power per square foot of sail area because of the flatness of the sail induced by full battens. In a practical junk rig, this is overcome by having larger sails. However in a handicap racing situation, this criticism hits an extreme because the handicap is based on sail area: the handicap rating will punish the junk rigged boat severely. On a race course, the buoys are set to assure that the boats will battle directly upwind for half of the race. Thus the junk rigged boat must sail a longer race course to the up wind buoy, at a slower speed, and then is punished by its handicap rating.
In a cruising environment however, sailing up wind is judged differently. Cruising upwind at the highest speed possible for long periods of time is uncomfortable. The experience of being heeled over for 4 hours is great sport, but for 4 weeks is just miserable. Slowing down when beating to windward is sensible cruising. The junk rig is also self tacking. None of the running lines need to be touched to tack the boat through the eye of the wind: you simply put the helm down, and the sails will swing over close hauled on the new tack. Life aboard a yacht for weeks that makes slow steady comfortable progress to windward is a much more pleasant experience because it is easy to tack, reef, cook, eat, and sleep.
On the reach, the criticism of the inefficiency of the flat sail shape of the junk sail seems to apply again, but only in very light winds. This can be overcome with cruising spinnaker and gennaker on the junk rig. However in moderate winds, both the larger inefficient junk sails and the small efficient modern sails will generate sufficient power to drive the hull near its hull speed. In high winds, the flatness of the junk sails is a benefit, where the modern rigged boat will require reefs. In a heavy blow, the ease of reefing will give the junk rig a clear advantage.
When running, the junk sail rig shows its advantage. When cruising, many sailors seek the trade winds and maximize their downwind routes. The huge sail area cross section of the junk rigged sail spreads a powerful wall of canvas far greater than a modern rigged boat, which will require a spinnaker to catch up. The junk rigged boat sails more easily downwind because it is self-jibing (just as self-tacking): just put the helm over to windward, and around she goes without touching anything. The center of effort on the junk sail can be adjusted by sliding the sail forward, exchanging sail area from behind the mast to the front of the mast: this improves the downwind balance of the sail and tames the jibe. Directly down wind, the junk rigged boat can sail "goose winged" (also known as "wing and wing," or even "wing and wong" by cruising sailors such as Annie Hill) with great ease and success. In this cruising environment, the junk rigged yacht is fast, easy to use, and inexpensive to setup and maintain.[3]
Heaving to in the junk rigged yacht is simple. Simply luffing the boat into the wind with the sails close hauled and then putting the helm down when the forward speed is spent will set the yacht into an easy "hove to" mode. The battens will tame the luffing sails. Heaving to in severe weather is done by dropping the forward junk sails into their cradle and reefing the aft junk rigged sails -- both tasks that are simplified by the junk rig. Heaving to in light winds can be difficult due to the lack of sail drive up wind.
[edit] Notable sailors of the modern junk rig
Annie Hill sails the junk rigged dory and writes of its virtues in her book 'Voyaging on a Small Income.' Her ship Badger was designed by Jay Benford.[4]
Bill King sailed the junk schooner (i.e. junk rigged boat with two masts) Galway Blazer II in the Sunday Times Golden Globe Race.
Joshua Slocum and his family built and sailed a junk rigged boat from Brazil to Washington, DC after the wreck of his barque Aquidneck. Slocum had high praise for the practicality of the junk rig: "Her rig was the Chinese sampan style, which is, I consider, the most convenient boat rig in the whole world."[5]
[edit] Comparison with Bermuda Rig
The junk rig is a simple and effective rig. The rig contrasts starkley with the bermuda rig which is prevalent on modern production boats. In its most traditional form the junk rig is carried on an unstayed mast (i.e. a mast without shrouds or stays, supported only on the step at the keelson and the partners) however standing rigging of some kind is not uncommon.
The cost to rig a boat with a junk rig would typically cost a fraction of the cost of a bermuda rig, due mostly to the lower number of parts and adaptability of the rig to cheaper materials (especially the sailcloth.)
The junk rig typically produces less drive than a similarly sized bermuda rig at high angles of attack (e.g. when sailing upwind, close-hauled) and this is especially pronounced in light wind. Performance close-hauled is perhaps the strongpoint of the bermuda rig - key to winning a race with an upwind leg or outmaneuvering an opponent in battle.
The junk rig typically produces more drive than a similarly sized bermuda rig when running downwind. A junk rigged boat can let its sails out athwartships (and beyond.) On a bermuda rigged boat the shrouds interfere with sails if the sail was let out until it was athwartship. The full battens of a junk sail prevent the sail from collapsing when running in light wind (dispensing with the need for a whisker pole.) On double-masted junk rigged boats, the sails can be flown wing-and-wing (i.e. on opposite sides of the boat) even when on a broad reach. The junk rig is well suited to downwind travel.
The junk rig appeals to shorthanded sailing crews for many reasons, especially because the rig reefs very easily. To lessen sail ("reef") all that is required is to let out the halyard. In contrast, reefing sail on a bermuda rigged boat would typically require crew to move about the deck - which increases the chance of falling overboard, especially during a high sea state which is typical of conditions which would encourage reefing.
It is typical to run the halyards (lines used to raise and lower the sail) and sheets (lines used to trim the sail) to the companionway on a junk rigged boat. This means that typical sailhandling can be performed from the relative safety of the cockpit, or even while the crew is below deck.
Junk sails are typically carried on a mast which rakes (slants) forward a few degrees from vertical, which can look odd to the unitiated. The forward rake of the sail encourages the sail to swing out, which makes the use of a preventer unnecessary. Another way to say this is that the sail is stable when swung out and doesn't return to the middle of the ship when the wind drops.
Other benefits of the junk rig over the bermuda rig
Less flogging of sails (quieter)
Less danger of an accidental jybe due to balance of the sail
Less danger from an accidental jybe with a lighter-weight boom (lowest batten)
More options when reefing - more "reef points"
The sail can be constructed by an amateur - the cut is entirely flat
Other shortcomings of the junk rig compared to the bermuda rig
The shape of the sail depends on the flex of the battens, and the battens do the opposite of what would be most desirable: they bend only a little when the wind is light, and they bend a lot when the wind is strong. Consequently the airfoil developed in light wind doesn't have enough chord length to develop much lift at low wind speeds. Perhaps the chief shortcoming of the junk rig is that it typically produces poor drive to windward in light winds.
The sail may remain almost entirely flat in light winds and develop unacceptable drive to windward
The fully battened sail is heavier than a sail made entirely of sailcloth.
[edit] Current Research
Several lines of research are being pursued by members of the Yahoo! Junkrig Group (see external links) which appears to be the most popular forum for discussion of the junk rig.
Some research of note:
The use of permanently cambered, flipping battens as pioneered by Nils Myklebust. This approach addresses one of the junk rig's greatest shortcomings: poor drive to windward in light winds. A similar approach involves the use of hinged battens to achieve a more precise camber than provided by bending of the battens alone.
The use of "quilted" panels to provide a more consistent camber as designed by Arne Kverneland.
The use of the Gurney flap is also being pursued.
[edit] References
- ^ Hasler & MacLeod, Practical Junk Rig, Tiller Publishing. [VM531.H37]
- ^ Derek Van Loan & Dan Haggerty, The Chinese Sailing Rig
- ^ *Voyaging On a Small Income ISBN 1-85310-425-6
- ^ http://www.benford.us/index.html?dories
- ^ Slocum, Joshua, The Voyage of the Liberdade, Press of Robinson & Stephenson, 1890. Reprinted by Roberts Brothers, Boston, 1894 and thereafter. Also available online http://www.ibiblio.org/eldritch/js/liberdade.htm
[edit] External links
- Junk and Advanced Cruising Rig Association
- Oliver Platt's The Chinese Sail
- A collection of information concerning chinese lugsails
- The Voyage of the Dragon King has detailed descriptions of sailing a junk rig, including a diagram and photos of the sheetlets and euphroe.
