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Bowstring Truss Bridges In The United States
A bowstring joins the two ends of the Bow and arrow, bow stave and launches the arrow. Desirable properties include light weight, strength, resistance to Abrasion (mechanical), abrasion, and resistance to water. Mass has most effect at the center of the string; of extra mass in the middle of the string slows the arrow about as much as at the ends. String forms Most bowstrings may be described as either simple, reverse-twisted, or looped. Simple strings may be made of any fiber, twisted into a single cord. Such strings have been used in many parts of the world and are still effective and fairly quick to make. However, they tend to be weaker for their weight, and they may also come apart if not kept constantly under tension. They are normally secured to the bow by a knot/round turn and two half-hitches at each end. Reverse-twisted strings are traditional in Europe and North America for most natural materials. Linen and hemp fiber have been widely used. The form is also used for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tsurumaki String Holder 1
Tsurumaki may refer to: *Tsurumaki, a traditional woven Japanese bowstring A bowstring joins the two ends of the bow stave and launches the arrow. Desirable properties include light weight, strength, resistance to abrasion, and resistance to water. Mass has most effect at the center of the string; of extra mass in th ... holder * Tsurumaki (surname), a Japanese surname * Tsurumaki Domain, a feudal domain of Japan {{disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Recurve Bow
In archery, a recurve bow is one of the main shapes a bow can take, with limbs that curve away from the archer when unstrung. A recurve bow stores more energy and delivers energy more efficiently than the equivalent straight-limbed bow, giving a greater amount of energy and speed to the arrow. A recurve will permit a shorter bow than the simple straight limb bow for given arrow energy, and this form was often preferred by archers in environments where long weapons could be cumbersome, such as in brush and forest terrain, or while on horseback. Recurved limbs also put greater stress on the materials used to make the bow, and they may make more noise with the shot. Extreme recurves make the bow unstable when being strung. An unstrung recurve bow can have a confusing shape and many Native American weapons, when separated from their original owners and cultures, were incorrectly strung backwards and destroyed when attempts were made to shoot them. A test performed by Hepworth and S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bow (weapon)
The bow and arrow is a ranged weapon system consisting of an elasticity (physics), elastic launching device (bow) and long-shafted projectiles (arrows). Humans used bows and arrows for hunting and aggression long before recorded history, and the practice was common to many prehistoric cultures. They were important weapon of war, weapons of war from ancient history until the early modern period, where they were rendered increasingly obsolete by the development of the more powerful and accurate firearms. Today, bows and arrows are mostly used for bowhunting, hunting and Modern competitive archery, sports. Archery is the art, practice, or skill of using bows to shooting, shoot arrows.Paterson ''Encyclopaedia of Archery'' p. 17 A person who shoots arrows with a bow is called a bowman or an archer. Someone who makes bows is known as a bowyer,Paterson ''Encyclopaedia of Archery'' p. 31 someone who makes arrows is a fletching, fletcher,Paterson ''Encyclopaedia of Archery'' p. 56 and som ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archery
Archery is the sport, practice, or skill of using a bow to shoot arrows.Paterson ''Encyclopaedia of Archery'' p. 17 The word comes from the Latin ''arcus'', meaning bow. Historically, archery has been used for hunting and combat. In modern times, it is mainly a competitive sport and recreational activity. A person who practices archery is typically called an archer, bowman, or toxophilite. History Origins and ancient archery The oldest known evidence of the bow and arrow comes from South African sites such as Sibudu Cave, where the remains of bone and stone arrowheads have been found dating approximately 72,000 to 60,000 years ago.Backwell L, d'Errico F, Wadley L.(2008). Middle Stone Age bone tools from the Howiesons Poort layers, Sibudu Cave, South Africa. Journal of Archaeological Science, 35:1566–1580. Backwell L, Bradfield J, Carlson KJ, Jashashvili T, Wadley L, d'Errico F.(2018). The antiquity of bow-and-arrow technology: evidence from Middle Stone Age layers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Worm, Parcel And Serve
To worm, parcel and serve a line is to apply a multi-layered protection against chafe and deterioration to standing rigging. It is a technique not usually used on modern small boats, but is found extensively on traditionally-rigged sailing ships. Worming, parcelling and serving —referred to collectively as "service"— is traditionally applied only to traditional twisted rope, either natural fiber or steel wire-rope, not the braided line almost exclusively used on modern vessels, but some traditional vessels now use modern high modulus braided lines (like Amsteel or AS-90) in place of wire rope (to save weight aloft) and serve the line to maintain the traditional appearance. It can be applied to the entire length of a line, such as a shroud, or selectively, to specific parts of a line, such as over the spliced ends of a stay, where the chafe on the middle section of the stay precludes complete protection. Technique Worming "Worming" the line is designed to fill in the ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultra-high-molecular-weight Polyethylene
Ultra-high-molecular-weight polyethylene (UHMWPE, UHMW) is a subset of the thermoplastic polyethylene. Also known as high-modulus polyethylene, (HMPE), it has extremely long chains, with a molecular mass usually between 3.5 and 7.5 million amu. The longer chain serves to transfer load more effectively to the polymer backbone by strengthening intermolecular interactions. This results in a very tough material, with the highest impact strength of any thermoplastic presently made. UHMWPE is odorless, tasteless, and nontoxic. It embodies all the characteristics of high-density polyethylene (HDPE) with the added traits of being resistant to concentrated acids and alkalis, as well as numerous organic solvents. It is highly resistant to corrosive chemicals except oxidizing acids; has extremely low moisture absorption and a very low coefficient of friction; is self-lubricating (see boundary lubrication); and is highly resistant to abrasion, in some forms being 15 times more resistant to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymer
A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass, relative to small molecule compounds, produces unique physical properties including toughness, high elasticity, viscoelasticity, and a tendency to form amorphous and semicrystalline structures rather than crystals. The term "polymer" derives from the Greek word πολύς (''polus'', meaning "many, much") and μέρος (''meros'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vectran
Vectran is a manufactured fiber, spun from a liquid-crystal polymer (LCP) created by Celanese Corporation and now manufactured by Kuraray. Chemically it is an aromatic polyester produced by the polycondensation of 4-hydroxybenzoic acid and 6-hydroxynaphthalene-2-carboxylic acid. Properties Advantages Vectran's golden fibers are noted for their thermal stability at high temperatures, high strength and modulus, low creep, and good chemical stability. They are moisture-resistant and generally stable in hostile environments. Polyester coating is often used around a Vectran core; polyurethane coating can improve abrasion resistance and act as a water barrier. Vectran has a melting point of 330 °C, with progressive strength loss from 220 °C. Disadvantages Although the tensile strength is similar to Kevlar, Vectran still tends to experience tensile fractures when exposed to significant stress. The wispy, hair-like fibers tend to fray, to easily acquire dirt, and to rea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kevlar
Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s as a replacement for steel in racing tires. It is typically spun into ropes or fabric sheets that can be used as such, or as an ingredient in composite material components. Kevlar has many applications, ranging from bicycle tires and racing sails to bulletproof vests, all due to its high tensile strength-to-weight ratio; by this measure it is five times stronger than steel. It is also used to make modern marching drumheads that withstand high impact; and for mooring lines and other underwater applications. A similar fiber called Twaron with the same chemical structure was developed by Akzo in the 1970s; commercial production started in 1986, and Twaron is now manufactured by Teijin. History Poly-paraphenylene terephthalamide (K2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Liquid Crystal Polymer
Liquid crystal polymers (LCPs) are polymers with the property of liquid crystal, usually containing aromatic rings as mesogens. Despite uncrosslinked LCPs, polymeric materials like liquid crystal Elastomer, elastomers (LCEs) and liquid crystal networks (LCNs) can exhibit liquid crystallinity as well. They are both crosslinked LCPs but have different cross link density. They are widely used in the digital display market. In addition, LCPs have unique properties like thermal actuation, anisotropic swelling, and soft elasticity. Therefore, they can be good actuators and sensors. One of the most famous and classical applications for LCPs is Kevlar, a strong but light fiber with wide applications including bulletproof vests. Background Liquid crystallinity in polymers may occur either by dissolving a polymer in a solvent (lyotropic liquid-crystal polymers) or by heating a polymer above its glass or melting transition point (thermotropic liquid-crystal polymers). Liquid-crystal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyethylene Terephthalate
Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, and thermoforming for manufacturing, and in combination with glass fibre for engineering resins. In 2016, annual production of PET was 56 million tons. The biggest application is in fibres (in excess of 60%), with bottle production accounting for about 30% of global demand. In the context of textile applications, PET is referred to by its common name, polyester, whereas the acronym ''PET'' is generally used in relation to packaging. Polyester makes up about 18% of world polymer production and is the fourth-most-produced polymer after polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC). PET consists of repeating (C10H8O4) units. PET is commonly recycled, and has the digit 1 (♳) as its resin identification code (RIC). T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gunnar Hámundarson
Gunnar Hámundarson () was a 10th-century Icelandic chieftain. He lived in Hlíðarendi in Fljótshlíð and is probably better known as Gunnar of Hlíðarendi ( non, Gunnarr á Hlíðarenda). He features prominently in the first half of Njáls saga, which tells of the chain of events ultimately leading to his death in battle. He was married to Hallgerðr Höskuldsdóttir of Höskuldsstaðir in Laxárdal in Dalasýsla, who was known as Hallgerðr langbrók ("Hallgerður longpants"). He was her third husband. It was said that she had killed both her former husbands, but she had in fact only killed the first. Their marriage was considered imprudent by Gunnar's friend Njáll Þorgeirsson, because it was caused by lust and not practicality. Gunnar the hero Gunnar was a god-like warrior — he is described as nearly invincible in combat. According to Njáls saga, he was a powerful, athletic man "capable of jumping his own height in full body armour, both back and front". He ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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