Wednesday, March 18, 2020

Find out What a Bulbous Bow Is

Find out What a Bulbous Bow Is The strongest resistance any vessel faces in standard operations comes from displacement as the hull moves through the water. Waves that climb the bow are water being pushed aside faster than it can move away. It takes a lot of power to overcome the viscosity and mass of water and that means burning fuel, which adds to costs. A bulbous bow is an extension of the hull just below the waterline. It has many subtle shape variations but it’s basically a rounded front portion that flares out slightly as it blends into the traditional displacement hull construction. These forward protrusions are about twice as long as the width of the base and they would usually not extend forward past the top of the bow. The basic principle is to create a low-pressure zone to eliminate the bow wave and reduce drag. First appearing on the USS Delaware in 1910, the bulbous bow was a controversial design of U.S. Navy Ship Architect David W. Taylor. Much of the controversy disappeared ten years later when passenger ships began exploiting the design to increase speeds. Hulls built with bulbous bow sections are common today. Under certain conditions, this type of design is very efficient at redirecting forces of hydrodynamic resistance and drag. There is a movement against bulbous bows that allows greater flexibility of ships at a time when slow steaming is a way to save fuel. Good Conditions for Bulbous Bows The design of a ship with a bulbous bow is discussed in many textbooks and technical articles. It is often referred to as a theory or an art, which is a short way of saying nobody is 100 percent sure of what they are writing. There are details to be worked out but modern builders have proprietary ways of analyzing and integrating all hydrodynamic aspects of their hulls and these methods are strict secrets. A bulbous bow works best under certain conditions and good design gives efficiency gains throughout the range of these factors. Speed – At low speeds, a bulbous bow will trap water above the bulb without forming a low-pressure zone to cancel the bow wave. This leads to increased drag and loss of efficiency. Each design has what is known as most efficient hull speed, or often just hull speed. This term refers to the speed where the shape of the hull is acting on the water is such a way to produce the minimum possible drag. This ideal hull speed might not be the top speed of a ship because at some point the lower pressure zone created by the bow features becomes larger than necessary. A zone of lower pressure water that is larger than the hull is inefficient and leads to reduced rudder response. Ideally, the cone of lower pressure water will collapse just before the props. This gives the prop blades something to push against and limits cavitation at the props and rudder. Cavitation will lead to reduced efficiency of props, sluggish steering, and excessive wear of hull and drive components. Size – Vessels under 49 feet (15 m) do not have enough wetted area to take advantage of a bulbous bow. The amount of drag on a hull is related to its wetted area. The structure of the bulb also increases drag and at a certain point, the benefits shrink to zero. Conversely, larger ships with a high proportion of waterline to frontal area use the bulbous bow most effectively. Bad Conditions for Bulbous Bows Rough Seas – While a traditional hull rises with the wave, a hull with a bulbous bow can dig in even if it is designed to lift the bow under normal conditions. The issue of trim is one of the most deeply dividing aspects of bow design among naval architects. There is also a huge psychological aspect among crews who perceive this bow design as dangerous in storms. There is some truth that these bows dig into wave faces but there is little proof that it is more dangerous than traditional designs. Ice – Some ice breaking ships do have a special shape of a bulbous bow that is heavily reinforced. Most bulbous bows are prone to damage since they are the first point of contact with an obstacle. In addition to ice, large debris and fixed objects like dock faces can damage these extended underwater bows.

Sunday, March 1, 2020

How Sequestration and Mandatory Federal Spending Cuts Work

How Sequestration and Mandatory Federal Spending Cuts Work Sequestration is the federal governments way of applying mandatory spending cuts across most programs and agencies during the budgeting process. Members of Congress use sequestration to reduce spending across the board when the governments annual deficit reaches a point that is unacceptable to them. Congress imposed spending caps on discretionary portions of federal spending through 2021, a move that was designed to save taxpayers about $1.2 trillion over nearly a decade. Sequestration  Definition The Congressional Research Service defines sequestration  this way: In general, sequestration entails the permanent cancellation of budgetary resources by a uniform percentage. Moreover, this uniform percentage reduction is applied to all programs, projects, and activities within a budget account. However, the current sequestration procedures, as in previous iterations of such procedures, provide for exemptions and special rules. That is, certain programs and activities are exempt from sequestration, and certain other programs are governed by special rules regarding the application of a sequester. Whats Affected By Sequestration When Congress uses sequestration, spending cuts happen to to both military and non-military spending, including important social programs such as Medicare. Most of the mandatory spending cuts come from non-military agencies and programs in the departments of Agriculture, Commerce, Education, Energy, Environmental Protection, Health and Human Services, Homeland Security, NASA and Transportation. Whats Not Affected by Sequestration Several programs - most notable those for senior citizens, veterans and the poor - are exempt from sequestration cuts. They include Social Security, Veterans Affairs, Medicaid, food stamps and Supplemental Security Income. Medicare, however, is subject to automatic cuts under sequestration. Its spending cannot be reduced by more than 2 percent, however. Also exempt from sequestration are congressional salaries. So even though federal works are furloughed or laid off to save money, elected officials still get paid. Sequestration  History The idea of imposing automatic spending cuts in the federal budget was first put in place by the Balanced Budget and Emergency Deficit Control Act of 1985. Sequestration is rarely used, however, because of the negative consequences severe spending cuts have on programs and services for citizens. Even when Congress uses sequestration, it does so as a political tool to force voluntarily spending reductions and often doesnt allow the full cuts to take effect. Modern Examples of Sequestration The most recent sequester was used in the Budget Control Act of 2011 to encourage Congress to reduce the annual deficit by $1.2 trillion by the end of 2012. When lawmakers failed to do so, the law triggered automatic budget cuts to the 2013 national security budget. A super Congress made up of a select group of 12 members of both the U.S. House of Representatives and U.S. Senate was chosen in 2011 to identify ways to reduce the national debt by $1.2 trillion over 10 years. The super Congress failed to reach an agreement, however. The sequestration cuts imposed in the 2011 legislation took effect in 2013 and continue through 2021. Opposition to Sequestration Critics of sequestration say spending cuts threaten national security through Defense Department reductions and harm the economy because federal works are often furloughed or laid off. These cuts will make it harder to grow our economy and create jobs by affecting our ability to invest in important priorities like education, research and innovation, public safety, and military readiness, said President Barack Obama, who was in office when the sequestration cuts of 2013 took effect.