Crewboats are a hybrid vessel that is suitable to carry either passengers are cargo. They were designed for oilfield use and are predominate there. However, many have been adapted to other tasks such as passenger ferries, tour vessels, dive boats, charter fishing vessels and of course offshore launch vessels. These boats are usually built of aluminum and range from about 40feet to 175 feet in length. They are generally faster than other vessels of the same size. Many have three to five main engines for extra speed. They also tend to consume more fuel.
They were originally intended to carry oilfield workers to the rigs offshore and to move needed equipment around the oil field at high speeds. Many operate from 15 to 30 knots (nautical miles per hour or about 18 to 36 miles per hour). However, as oilf fields have become larger and further from shore, it is more efficient to move people by helicopter. But, crewboats still move equipment around the oilfield. They are also used to service ships with crew changes and supplies.
Utility boats range in size from 65 to 150 feet in length. As the name implies they are general duty and multi purpose. Hence the name utility boat General Utility. They are primarily used in the oilfield to transport equipment and personnel. They are usually steel construction and have the ability to carry and transfer fuel, water, mud and other chemicals. Typically, they have extra bunk space and are used to support dive operations, construction projects, and house repair crews. They are slow but stable vessels with speeds from 9 to 12 knots.
Chaseboats are used in the seismic industry. Not necessarily fast, chaseboats are typically fishing trawlers equipped with extra navigation equipment. They protect seismic cables towed behind the seismic vessels. These cables carry sensors that record the bottom geography and geology. Cables can be anywhere from 3 to 6 miles in length and are both expensive and fragile. Chaseboat/Trawlers are very stable platforms with a long endurance. Most operate in rough weather conditions and can do so for 3 to 6 weeks without fuel or supplies.
Launch boats can fall into two distinct groups; inland launchs which are small vessels or tug and barge combinations used to deliver food and supplies to ships in harbor and offshore launches which are larger open water vessels that perform the same task but on open water in either the anchorage or lightering areas of the gulf. Offshore launches are typically crewboats or utiity boats.
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