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Rudder

Gist

A rudder is a flat, vertical blade at the stern (rear) of a ship that controls its direction by deflecting water flow. When the rudder is turned, the force of the water against it pushes the stern away, causing the ship to turn in the opposite direction. It is operated by a steering wheel or tiller connected to a mechanical or hydraulic system, making it a crucial component for navigation and safety. 

A rudder is a control surface used to steer a vessel or aircraft by changing the direction of the fluid (water or air) flowing past it, which in turn creates a turning or yawing motion. In ships, it directly steers the vessel, while in aircraft, it is primarily used to coordinate turns, correct for aerodynamic forces (like "adverse yaw"), and maintain stability, especially during crosswinds. 

Summary

A rudder is a part of the steering apparatus of a boat or ship that is fastened outside the hull, usually at the stern. The most common form consists of a nearly flat, smooth surface of wood or metal hinged at its forward edge to the sternpost. It operates on the principle of unequal water pressures. When the rudder is turned so that one side is more exposed to the force of the water flowing past it than the other side, the stern will be thrust away from the side that the rudder is on and the boat will swerve from its original course. In small craft the rudder is operated manually by a handle termed a tiller or helm. In larger vessels, the rudder is turned by hydraulic, steam, or electrical machinery.

The earliest type of rudder was a paddle or oar used to pry or row the stern of the craft around. The next development was to fasten a steering oar, in a semivertical position, to the vessel’s side near the stern. This arrangement was improved by increasing the width of the blade and attaching a tiller to the upper part of the handle. Ancient Greek and Roman vessels frequently used two sets of these steering paddles. Rudders fastened to the vessel’s sternpost did not come into general use until after the time of William the Conqueror. In ships having two or more screw propellers, rudders are fitted sometimes directly behind each screw.

Special types of rudders use various shapes to obtain greater effectiveness in manoeuvring. The balanced rudder and the semibalanced rudder (see illustration) are shaped so that the force of the water flowing by the rudder will be balanced or partially balanced on either side of its turning axis, thus easing the pressure on the steering mechanism or the helmsman. The lifting rudder is designed with a curvature along its lower edge that will lift the rudder out of danger should it strike an object or the bottom.

Details

A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium (usually air or water). On an airplane, the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane. A rudder operates by redirecting the fluid past the hull or fuselage, thus imparting a turning or yawing motion to the craft. In basic form, a rudder is a flat plane or sheet of material attached with hinges to the craft's stern, tail, or afterend. Often rudders are shaped to minimize hydrodynamic or aerodynamic drag. On simple watercraft, a tiller—essentially, a stick or pole acting as a lever arm—may be attached to the top of the rudder to allow it to be turned by a helmsman. In larger vessels, cables, pushrods, or hydraulics may link rudders to steering wheels. In typical aircraft, the rudder is operated by pedals via mechanical linkages or hydraulics.

Boat rudders details

Boat rudders may be either outboard or inboard. Outboard rudders are hung on the stern or transom. Inboard rudders are hung from a keel or skeg and are thus fully submerged beneath the hull, connected to the steering mechanism by a rudder post that comes up through the hull to deck level, often into a math. Inboard keel hung rudders (which are a continuation of the aft trailing edge of the full keel) are traditionally deemed the most damage resistant rudders for off shore sailing. Better performance with faster handling characteristics can be provided by skeg hung rudders on boats with smaller fin keels.

Rudder post and mast placement defines the difference between a ketch and a yawl, as these two-masted vessels are similar. Yawls are defined as having the mizzen mast abaft (i.e. "aft of") the rudder post; ketches are defined as having the mizzen mast forward of the rudder post.

Small boat rudders that can be steered more or less perpendicular to the hull's longitudinal axis make effective brakes when pushed "hard over." However, terms such as "hard over," "hard to starboard," etc. signify a maximum-rate turn for larger vessels. Transom hung rudders or far aft mounted fin rudders generate greater moment and faster turning than more forward mounted keel hung rudders. Rudders on smaller craft can be operated by means of a tiller that fits into the rudder stock that also forms the fixings to the rudder foil. Craft where the length of the tiller could impede movement of the helm can be split with a rubber universal joint and the part adjoined the tiller termed a tiller extension. Tillers can further be extended by means of adjustable telescopic twist locking extension.

There is also the barrel type rudder, where the ship's screw is enclosed and can be swiveled to steer the vessel. Designers claim that this type of rudder on a smaller vessel will answer the helm faster.

Rudder control

Large ships (over 10,000 ton gross tonnage) have requirements on rudder turnover time. To comply with this, high torque rudder controls are employed. One commonly used system is the ram type steering gear. It employs four hydraulic rams to rotate the rudder stock (rotation axis), in turn rotating the rudder.

Aircraft rudders

On an aircraft, a rudder is one of three directional control surfaces, along with the rudder-like elevator (usually attached to the horizontal tail structure, if not a slab elevator) and ailerons (attached to the wings), which control pitch and roll, respectively. The rudder is usually attached to the fin (or vertical stabilizer), which allows the pilot to control yaw about the vertical axis, i.e., change the horizontal direction in which the nose is pointing.

Unlike a ship, both aileron and rudder controls are used together to turn an aircraft, with the ailerons imparting roll and the rudder imparting yaw and also compensating for a phenomenon called adverse yaw. A rudder alone will turn a conventional fixed-wing aircraft, but much more slowly than if ailerons are also used in conjunction. Sometimes pilots may intentionally operate the rudder and ailerons in opposite directions in a maneuver called a slip or sideslip. This may be done to overcome crosswinds and keep the fuselage in line with the runway, or to lose altitude by increasing drag, or both.

Another technique for yaw control, used on some tailless aircraft and flying wings, is to add one or more drag-creating surfaces, such as split ailerons, on the outer wing section. Operating one of these surfaces creates drag on the wing, causing the plane to yaw in that direction. These surfaces are often referred to as drag rudders.

Rudders are typically controlled with pedals.

Additional Information:

Description

The rudder is a primary flight control surface which controls rotation about the vertical axis of an aircraft. This movement is referred to as "yaw". The rudder is a movable surface that is mounted on the trailing edge of the vertical stabilizer or fin. Unlike a boat, the rudder is not used to steer the aircraft; rather, it is used to overcome adverse yaw induced by turning or, in the case of a multi-engine aircraft, by engine failure and also allows the aircraft to be intentionally slipped when required.

Function

In most aircraft, the rudder is controlled through the flight deck rudder pedals which are linked mechanically to the rudder. Deflection of a rudder pedal causes a corresponding rudder deflection in the same direction; that is, pushing the left rudder pedal will result in a rudder deflection to the left. This, in turn, causes the rotation about the vertical axis moving the aircraft nose to the left. In large or high speed aircraft, hydraulic actuators are often used to help overcome mechanical and aerodynamic loads on the rudder surface.

Rudder effectiveness increases with aircraft speed. Thus, at slow speed, large rudder input may be required to achieve the desired results. Smaller rudder movement is required at higher speeds and, in many more sophisticated aircraft, rudder travel is automatically limited when the aircraft is flown above Manoeuvring Speed to prevent deflection angles that could potentially result in structural damage to the aircraft.

Tobacco

Gist

Within 10 seconds of your first puff, the toxic chemicals in tobacco smoke reach your brain, heart and other organs. Smoking harms almost every part of your body and increases your risk of many diseases. Smoking also affects how you look and feel, your finances and the people close to you.

Tobacco in cigarettes is made from dried, cured tobacco leaves that are processed and often mixed with additives for flavor. These leaves are wrapped in paper and contain a highly addictive drug called nicotine. When a cigarette is burned, it releases a mixture of thousands of chemicals, at least 69 of which are known to cause cancer.

Summary

Tobacco is the common name of several plants in the genus Nicotiana of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. Seventy-nine species of tobacco are known, but the chief commercial crop is N. tabacum. The more potent variant N. rustica is also used in some countries.

Dried tobacco leaves are mainly used for smoking in cigarettes and cigars, as well as pipes and shishas. They can also be consumed as snuff, chewing tobacco, dipping tobacco, and snus.

Tobacco contains the highly addictive stimulant alkaloid nicotine as well as harmala alkaloids. Due to the widespread availability and legality of tobacco, nicotine is one of the most widely used recreational drugs. Tobacco use is a cause or risk factor for many deadly diseases, especially those affecting the heart, liver, and lungs, as well as many cancers. In 2008, the World Health Organization named tobacco use as the world's single greatest preventable cause of death.

Details:

Key facts

* Tobacco kills up to half of its users who don’t quit.
* Tobacco kills more than 7 million people each year, including an estimated 1.6 million non-smokers who are exposed to second-hand smoke.
* Around 80% of the world's 1.3 billion tobacco users live in low- and middle-income countries.
* To address the tobacco epidemic, WHO Member States adopted the WHO Framework Convention on Tobacco Control (WHO FCTC) in 2003. Currently 183 countries are Parties to this treaty.
* The WHO MPOWER measures are in line with the WHO FCTC and have been shown to save lives and reduce costs from averted healthcare expenditure.

Overview

The tobacco epidemic is one of the biggest public health threats the world has ever faced, responsible for over 7million deaths annually as well as disability and long-term suffering from tobacco-related diseases.

All forms of tobacco use are harmful, and there is no safe level of exposure to tobacco. Cigarette smoking is the most common form of tobacco use worldwide. Other tobacco products include waterpipe tobacco, cigars, cigarillos, heated tobacco, roll-your-own tobacco, pipe tobacco, bidis and kreteks, and smokeless tobacco products.

Around 80% of the 1.3 billion tobacco users worldwide live in low- and middle-income countries, where the burden of tobacco-related illness and death is heaviest. Tobacco use contributes to poverty by diverting household spending from basic needs such as food and shelter to tobacco. This spending behaviour is difficult to curb because tobacco is so addictive.

The economic costs of tobacco use are substantial and include significant health care costs for treating the diseases caused by tobacco use as well as the lost human capital that results from tobacco-attributable morbidity and mortality.

Key measures to reduce the demand for tobacco:

Surveillance is key

Good monitoring tracks the extent and character of the tobacco epidemic and indicates how best to tailor policies. Almost half of the world's population are regularly asked about their tobacco use in nationally representative surveys among adults and adolescents.

Second-hand smoke kills

Second-hand smoke is the smoke that fills restaurants, offices, homes, or other enclosed spaces when people smoke tobacco products. There is no safe level of exposure to second-hand tobacco smoke. Second-hand smoke causes serious cardiovascular and respiratory diseases, including coronary heart disease and lung cancer, and kills around 1.6 million people prematurely every year.

Over third of the world's population living in 79 countries are protected by comprehensive national smoke-free laws.

Tobacco users need help to quit

Among smokers who are aware of the dangers of tobacco, most want to quit. Counselling and medication can more than double a tobacco user’s chance of successful quitting.

National comprehensive cessation services with full or partial cost-coverage are available to assist tobacco users to quit in only 31 countries, representing a third of the world's population.

Hard-hitting anti-tobacco mass media campaigns and pictorial health warnings prevent children and other vulnerable groups from taking up tobacco use, and increase the number of tobacco users who quit.

Today 62% of the world’s population live in the 110 countries that meet best practice for graphic health warnings, which includes among other criteria, large (50% or more of the main areas of the package) pictorial health warnings displayed in the national language and rotating regularly.

2.9 billion people live in the 36 countries that have aired at least one strong anti-tobacco mass media campaign within the last 2 years.

Bans on tobacco advertising lower consumption

Tobacco advertising promotion and sponsorship (TAPS) increases and sustains tobacco use by effectively recruiting new tobacco users and discouraging tobacco users from quitting.

More than one third of countries (68), representing over a quarter of the world’s population, have completely banned all forms of TAPS.

Taxes are effective in reducing tobacco use

Tobacco taxes are the most cost-effective way to reduce tobacco use, especially among youth and low-income groups. A tax increase that increases tobacco prices by 10% decreases tobacco consumption by about 4% in high-income countries and about 5% in low- and middle-income countries.

Even so, high tobacco taxes are rarely implemented. Only 41 countries, with 12% of the world's population, have introduced taxes on tobacco products so that at least 75% of the retail price is tax.

Illicit trade of tobacco products must be stopped

The illicit trade in tobacco products poses major health, economic and security concerns around the world. It is estimated that 1 in every 10 cigarettes and tobacco products consumed globally is illicit.

Experience from many countries demonstrates that illicit trade can be successfully addressed even when tobacco taxes and prices are raised, resulting in increased tax revenues and reduced tobacco use.

The WHO FCTC Protocol to Eliminate the Illicit Trade of Tobacco Products (ITP) is the key supply side policy to reduce tobacco use and its health and economic consequences.

Newer nicotine and tobacco products

Heated tobacco products (HTPs) are tobacco products that produce aerosols containing nicotine and toxic chemicals upon heating of the tobacco, or activation of a device containing the tobacco. They contain the highly addictive substance nicotine, non-tobacco additives and are often flavoured.

Despite claims of “risk reduction”, there is no evidence to demonstrate that HTPs are less harmful than conventional tobacco products. Many toxicants found in tobacco smoke are at significantly lower levels in HTP aerosol but HTP aerosol contains other toxicants found sometimes at higher levels than in tobacco smoke, such as glycidol, pyridine, dimethyl trisulfide, acetoin and methylglyoxal.

Further, some toxicants found in HTP aerosols are not found in conventional cigarette smoke and may have associated health effects. Additionally, these products are highly variable and some of the toxicants found in the emissions of these products are carcinogens. 

Electronic cigarettes (or e-cigarettes) are the most common form of electronic nicotine delivery systems (ENDS) and electronic non-nicotine delivery systems (ENNDS) but there are others, such as e-cigars and e-pipes. ENDS contain varying amounts of nicotine and harmful emissions. Use of ENDS/ENNDS products is colloquially referred to as ‘vaping’. However this does not mean that they are harmless or emit water vapour.

E-cigarette emissions typically contain nicotine and other toxic substances that are harmful to users and non-users who are exposed to the aerosols second-hand. Some products claiming to be nicotine-free have been found to contain nicotine.

Evidence reveals that these products are harmful to health and are not safe. However, it is too early to provide a clear answer on the long-term impacts of using them or being exposed to them. Some recent studies suggest that ENDS use can increase the risk of heart disease and lung disorders. Nicotine exposure in pregnant women can have negative health consequences on the fetus, and nicotine, which is a highly addictive substance is damaging for brain development.

Nicotine pouches are pre-portioned pouches that contain nicotine and are similar to traditional smokeless tobacco products such as snus in some respects including appearance, inclusion of nicotine and manner of use (placing them between the gum and lip). They are often promoted, as “tobacco-free”, which can be used anywhere and in some jurisdictions, such as the USA, they are referred to as “white pouches”.

Additional Information

Tobacco is common name of the plant Nicotiana tabacum and, to a limited extent, Aztec tobacco (N. rustica) and the cured leaf that is used, usually after aging and processing in various ways, for smoking, chewing, snuffing, and extraction of nicotine. Various other species in the genus Nicotiana are grown as ornamentals, known collectively as flowering tobaccos. This article deals with the farming of commercial tobacco from cultivation to curing and grading.

Cultivation

Though tobacco is tropical in origin, it is grown throughout the world. Cultivated tobacco (N. tabacum) requires a frost-free period of 100 to 130 days from date of transplanting to maturity in the field. Aztec tobacco (N. rustica), which is grown to some extent in India, Vietnam, and certain Transcaucasian countries, matures more quickly and is more potent than cultivated tobacco.

The prime requisite for successful tobacco culture is a supply of well-developed healthy seedlings that is available at the proper time for transplanting. Soil for a plant bed should be fertile and of good tilth and drainage; it must be protected from chilling winds and exposed to the sun. The soil is usually partially sterilized by burning or using chemicals such as methyl bromide (now illegal in many countries) to control plant diseases, weeds, insect pests, and nematodes. The soil must be finely pulverized and level so that the seed can be lightly covered with soil by rolling or trampling. Uniform distribution of seeds is important. In warm regions of the world, the germinating seedlings are produced outdoors in cold frames covered with thin cotton cloth or a thin mulch, such as chopped grass (used in particular in Zimbabwe), straw, or pine needles. Glass or plastic is used in colder regions, and close attention is given to watering and ventilation. After 8 to 10 weeks the seedlings are 10 to 18 cm (4 to 7 inches) in length and are ready for transplanting in the field. Transplanting machines are used extensively in some areas, but much of the world’s tobacco is planted by hand.

Spacing of plants in the field varies widely according to the type of tobacco. Orinoco strains, used for flue curing, are grown in rows 1.2 metres (4 feet) apart, with plants 50 to 60 cm (20 to 24 inches) apart in the row. Varieties in the Pryor group are grown to produce the dark air-cured and fire-cured types and are often planted in hills 1 metre (3.5 feet) apart. Burley and Maryland strains, used for the production of light air-cured tobaccos, may be planted 81 to 91 cm (32 to 36 inches) apart or closer. Broadleaf and seed-leaf strains, including the Havana seed, Cuban, and Sumatra varieties, are used for the production of cigars; they are grown in rows spaced 1 metre (3 feet) apart, with individual plants placed at a distance of 38 to 68 cm (15 to 27 inches) from each other. The variety grown for production of Perique is spaced the widest, with rows 1.5 metres (5 feet) apart and 91 to 107 cm (36 to 42 inches) between plants. Aromatic tobaccos, also used for cigars, are spaced in rows 38 to 60 cm (15 to 24 inches) apart with 8 to 20 cm (3 to 8 inches) between plants in the row.

Soil requirements vary widely with the type of tobacco grown, though well-drained soil with good aeration is generally desirable. Flue-cured, Maryland, cigar-binder, and wrapper types of tobacco are produced on sandy and sandy loam soil. Burley, dark air-cured, fire-cured, and cigar-filler types are grown on silt loam and clay loam soils, with clay subsoils. The need for fertilizer is determined by the type of tobacco, soil, and climate; nitrogen, phosphorus, and potassium are commonly applied as necessary to prevent symptoms of nutritional deficiency.

Large-leaf tobaccos are often topped—that is, the terminal growth is removed—when the plant has reached the desired size, usually at or shortly after flowering. The number of leaves remaining varies widely. Dark air-cured and fire-cured tobaccos may have 10 to 16 leaves, while Burley, flue-cured, Maryland, and cigar types may have 16 to 20 leaves. After topping, the suckers, or lateral shoots, are removed to increase leaf development, providing increased yields. The work may be done by hand, in which case it must be repeated regularly, or by application of sucker-suppressing chemicals. Aromatic tobacco culture differs from that of most of the large-leafed tobaccos in that the plants are rarely topped and preferably are grown on soils of low productivity.

Diseases and pests

Common diseases and pests are black root rot, Fusarium wilt, tobacco mosaic virus (TMV), bacterial leaf spot, downy mildew, black shank, broomrape, and witchweed. These may be controlled by sanitation, crop rotation, the use of fungicide and herbicide sprays and fumigants, and breeding of disease-resistant strains. Some resistant varieties of tobacco have been produced by blending desired characteristics from longflower tobacco (N. longiflora) and N. glutinosa, among others, with strains of commercial tobacco.

Common insect pests are green June beetle larvae, cutworms, and flea beetles in the plant bed and hornworms, grasshoppers, flea beetles, cutworms, budworms, and aphids in the field. The cigarette, or tobacco, beetle damages the stored leaf and sometimes the manufactured product. Insect pests are controlled on the growing crop by using pesticide sprays and dusts, on the stored product by fumigating and trapping. Biological control often is effective. Fumigation controls nematodes in the field.

Harvest

Tobacco is harvested 70 to 130 days after transplanting by one of two methods: (1) the entire plant is cut and the stalk split or speared and hung on a tobacco stick or lath, or (2) the leaves are removed at intervals as they mature. The leaves of cigar-wrapper and aromatic tobaccos are strung using a needle, and leaves to be flue-cured are looped, using a string tied to a lath or stick that is hung in a curing barn. To prevent breakage and bruising during the handling necessary in curing, it is desirable for the leaf to wilt without sunburning. Tobacco may be left in the field from a few hours to two days to wilt.

Curing

The three most common methods of curing are by air, fire, and flue. A fourth method, sun curing, is practiced with aromatic types and to a limited extent with air-cured types. Curing entails four essential steps: wilting, yellowing, colouring, and drying. These involve physical and chemical changes in the leaf and are regulated to develop the desired properties. Air curing is accomplished mainly by mechanical ventilation inside buildings. Coke, charcoal, or petroleum gas may be burned to provide heat when conditions warrant. Air curing, which requires from one to two months’ time, is used for many tobaccos, including dark air-cured types, cigar, Maryland, and Burley.

The fire-curing process resembles air curing except that open wood fires are kindled on the floor of the curing barn after the tobacco has been hanging for two to six days. The smoke imparts to the tobacco a characteristic aroma of creosote. The firing process may be continuous or intermittent, extending from three weeks to as long as 10 weeks until curing is complete and the leaf has been cured to the desired finish.

The barns for flue curing are usually small and tightly constructed with ventilators and metal pipes, or flues, extending from furnaces around or under the floor of the barn. Fuels used are wood, coal, oil, and liquid petroleum gas. If oil or gas heaters are used, flues are not needed. Heat is applied carefully, and the leaves are observed closely for changes in their chemical and physical composition. Flue curing requires from four to eight days’ time and is used for Virginia, or bright, tobacco. In the process called bulk curing, the leaves are loaded evenly in racks arranged in a curing chamber.

Grading

After curing, the leaf may be piled in bulk to condition for a time before it is prepared for sale. The preparation consists usually of grading the leaf and putting it in a bale or package of convenient size and weight for inspection and removal by the buyer. Except during humid periods, the leaf must be conditioned in moistening cellars or humidified rooms before it can be handled without breakage. Type of leaf and local custom determine the fineness of grading. At its most elaborate, grading may be by position of the leaf on the plant, colour, size, maturity, soundness, and other recognizable qualities; flue-cured tobacco in the United States is graded that way, and each grade is bulked or baled separately. Much simpler grading is usual in developing countries, where the buyer is as much concerned with the proportions of each grade as with the quality of the entire lot; aromatic tobaccos are an example of this. Most tobaccos entering world trade, except the aromatic, are assembled before sale into bundles, or hands, of 15 to 30 leaves and tied with one leaf wrapped securely around the butts.

Most tobaccos, except aromatic and cigar, are regraded if necessary and usually redried after purchase; then the exact amount of moisture needed for aging is added and the tobacco is securely packed in cases or hogsheads. Exported tobacco is shipped in this form. The trend is for the packing factories to stem the leaf—that is, remove most of the stem leaving the lamina (leaf blade)—usually by threshing machines but sometimes by hand, before redrying it. The aging process, particularly with cigar tobaccos, is sometimes hastened by forced fermentation procedures. After purchase, aromatic tobaccos are manipulated; that is, they are factory-graded, baled, and subjected to an elaborate in-the-bale fermentation process before going to the ultimate manufacturer.

Codes Quotes

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2. Moral codes adjust themselves to environmental conditions. - Will Durant

3. I cannot help thinking that the menace of Hell makes as many devils as the severe penal codes of inhuman humanity make villains. - Lord Byron

4. Many British people of different faiths follow religious codes and practices and benefit a great deal from the guidance they offer. - Theresa May

5. I knew that the most important thing a man has is in his head, and from a young age, I often studied the head structure of each person, hoping to crack his codes. I considered a high forehead a gift from God. - Shimon Peres.