Ljungström rig is the name for the sailing

rig Rig may refer to: Objects and structures * Rig (fishing), an arrangement of items used for fishing * Drilling rig, a structure housing equipment used to drill or extract oil from underground * Rig (stage lighting) * rig, a horse-drawn carriage ...

Fredrik Ljungström Fredrik Ljungström (16 June 1875 – 18 February 1964) was a Swedish engineer, technical designer, and industrialist. Considered one of the foremost inventors of Sweden, Fredrik Ljungström accounted for hundreds of technical patents alon ...

with double main

sail A sail is a tensile structure—which is made from fabric or other membrane materials—that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails may ...

s and rotating

mast Mast, MAST or MASt may refer to: Engineering * Mast (sailing), a vertical spar on a sailing ship * Flagmast, a pole for flying a flag * Guyed mast, a structure supported by guy-wires * Mooring mast, a structure for docking an airship * Radio mast ...

, but without

boom Boom may refer to: Objects * Boom (containment), a temporary floating barrier used to contain an oil spill * Boom (navigational barrier), an obstacle used to control or block marine navigation * Boom (sailing), a sailboat part * Boom (windsurfi ...

foresail A foresail is one of a few different types of sail set on the foremost mast (''foremast'') of a sailing vessel: * A fore-and-aft sail set on the foremast of a schooner or similar vessel. * The lowest square sail on the foremast of a full-rig ...

forestay On a sailing vessel, a forestay, sometimes just called a stay, is a piece of standing rigging which keeps a mast from falling backwards. It is attached either at the very top of the mast, or in fractional rigs between about 1/8 and 1/4 from the t ...

and

shroud Shroud usually refers to an item, such as a cloth, that covers or protects some other object. The term is most often used in reference to ''burial sheets'', mound shroud, grave clothes, winding-cloths or winding-sheets, such as the famous Shr ...

. The early models of the

Ljungström sailboat Ljungström sailboats were created by the Swedish engineer Fredrik Ljungström, who was interested in sailing since childhood. A "Ljungström sailboat" typically has a "circular arc" hull and a "Ljungström rig". A Ljungström rig mast has no ...

had a stern stay but this was omitted around 1945, before the model 12 (Vingen 12). The Ljungström rig is competitive towards the competing rigs from that time when

close hauled A point of sail is a sailing craft's direction of travel under sail in relation to the true wind direction over the surface. The principal points of sail roughly correspond to 45° segments of a circle, starting with 0° directly into the wind. ...

and full run but is lacking at

beam reach Beam Reach is a redevelopment area in London, England and part of the London Riverside section of the Thames Gateway. It is an industrial area adjacent to the new neighbourhood of Beam Park. Geography It is located in the southern part of the L ...

and

broad reach A point of sail is a sailing craft's direction of travel under sail in relation to the true wind direction over the surface. The principal points of sail roughly correspond to 45° segments of a circle, starting with 0° directly into the wind. ...

. Its main purpose and advantage is, however, safety and ease of handling.

History

The first Ljungström rig was developed by the Swedish engineer

to enhance safety at sea. The family had been close to severe accidents with the traditionally rigged Ebella, nowadays named Beatrice Aurore, when in hard weather the crew had to walk on deck to take in sail. Ljungström, in order to not risk the safety of his crew, designed a

less rig handled completely from the

cockpit A cockpit or flight deck is the area, usually near the front of an aircraft or spacecraft, from which a Pilot in command, pilot controls the aircraft. The cockpit of an aircraft contains flight instruments on an instrument panel, and the ...

Components

Mast

The mast is made of glued clean wood, conical, without stays or shrouds. Boom, pole, gaff, spreaders and such are completely omitted. The mast is supported by two ball bearings, one at the keel and one at the deck hole, and can thus rotate freely. The rotation is created using a wooden collar, with a V-shaped track, around the mast below deck. Around this collar an infinite rope sling runs through two blocks to a winch, powered by hand or an electric motor. In this way the sail is rolled onto the mast when less area is needed or when the sailing is finished. As a result of the conic mast, the

clew Sail components include the features that define a sail's shape and function, plus its constituent parts from which it is manufactured. A sail may be classified in a variety of ways, including by its orientation to the vessel (e.g. ''fore-and-a ...

will move up the less sail that exposed. As a result of the mast taper the clew will end up higher and higher the closer it is to the mast. The mast is hollow, partly to reduce weight (up to 4.5% of a

keelboat A keelboat is a riverine cargo-capable working boat, or a small- to mid-sized recreational sailing yacht. The boats in the first category have shallow structural keels, and are nearly flat-bottomed and often used leeboards if forced in open wat ...

's displacement), and partly so that the halyard can run inside the mast, and therefore manufactured in two halves. At the top is a metal bracket with pulley for the halyard which then runs inside the mast and comes out below deck, where a pulley is located under the mast root. The mast foot is tapered so the mast stands firmly in the lower tapered ball bearing. Level with the deck is the mast "bottleneck" where the upper ball bearing rests. By means of a bracket bolted to the deck upper surface the upper ball bearing is kept in place, thereby keeping the mast from being lifted from the lower layer.

Sail

A Ljungström rig usually has two sails, stitched together at the luff. On all points of sail, except a full run, these sails are close together. In the unlikely event that one of the sails would rip the other still stands and the boat can safely reach harbor. The Ljungström rig is often compared with a staysail with the big difference that the mast bends inversely to the forestay. This must be compensated for so that the luff is provided a belly which is <30% of the masthead deflection, about 2% of the luff length. Since the sail is hoisted throughout the season, it is appropriate that leach and foot consists of UV-resistant fabric that covers the entire mast in its furled state.

Sheeting

The two sails each have their own independent sheet. On previous models the blocks sat on the deck aft area but later improved forwarding with a pole which raised the sheeting point about one meter. Some models have a winch. The advantage of the Ljungström rig, besides the simplicity and safety, is in the engineer's knowledge of fluid dynamics. The mast is rotated so that the sail rests on the mast at lee. This is to minimize turbulent flow on the leeward side of the mast and the propulsion force, which is so important, becomes almost undisturbed. This was totally new for that time and made a boat with Ljungström rig point higher than its contemporary competitors. Today profiled masts addresses this problem, but hardly more efficiently. The real showpiece, however, is at full run where the two sails separate as butterfly wings, sheeted on each side, similar to a spinnaker, but with no extra booms or guys needed.

Sources

* "Fredrik Ljungström 1875–1964 – Inventor and inspirer", by the son Olle Ljungström, Svenska Mekanisters Riksförening 1999, * "Ljungström boat 75 years" by Olle Ljungström 2008 (self-published) *

External links

Ljungström boats through the years – The unofficial web page for Ljungström Boats
{{DEFAULTSORT:Ljungstrom rig Sailing rigs and rigging Ljungström