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boat propulsion for PeaceKris
Posted by BuoyancyBray
boat propulsion for PeaceKris
BuoyancyBray - 1/29/2007 12:00 AM
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Category: Educational
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Today`s Aluminum Jet boats are a far cry from the early riveted aluminum fishing boats sold through Sears catalogs or the early jet boats from the 1960s and 70s. Here`s a quick overview of where the industry has come from and what represents the state-of-the-art today.

First Generation. The water jet pump for boat propulsion was invented by New Zealander, Sir William Hamilton. In 1953 he constructed his first centrifugal pump driven by a bevel gear. He installed it in a 11.5 ft plywood boat with a Ford engine. A year later he began producing jet boats. In the 60s Berkeley Marine was the first large volume producers of jet pumps in the USA and popularized jet-powered boats for the American family runabout & skiing markets.

During the 70s jet-powered boats were all the rage. Many boat builders jumped into the jet-power market segment including well-known companies like Glastron, Formula and Sea Ray. These boats typically were hi-performance runabouts made mostly of fiberglass with monster engines from Detroit. The engines were gas hogs and the jets were about 60% as efficient as conventional props. Then the 80s fuel shortage hit and these boats fell from favor, even though they offered superior safety and reliability as well as lower maintenance compared to propeller driven boats.

Second Generation. Through the 1980s and early 90s development and improvements continued in jet pumps as well as aluminum hull design & fabrication. For jet pumps other manufacturers entered the market, such as; Dominator, American Turbine, Kodiak Marine, and Legend Jet Drive. Each made innovative contributions to efficiency, versatility and reliability

For aluminum boats, development continued mostly from small boat manufacturers in the North West where river running in jet boats continued to have a strong following. They moved away from the poor maneuverability and hard ride of the early flat bottom jon-boat styles to V shaped delta as well as perfecting the reliable all-welded aluminum process.

Third Generation. By the mid 90s improvements in jet intakes, impeller designs and jet nozzles saw the leading jet pump manufacturers producing jets with efficiency approaching 90% that of props. And the in-board gas guzzlers were history, replaced by much more efficient engines mainly from Chevy and Ford and marinized by engine specialists like Marine Power and Kodiak Marine. Mercury also entered the market with an integrated in-board/jet out-drive For aluminum boats, by the mid-90s manufacturers had largely converted to producing a "modified-delta". This is basically a combination of "flat bottom" and "delta V". The modified-delta typically has a 6` to 14` flat bottom from mid-ship to stern. It combines the shallow draft advantages of flat-bottom hulls with the turning and straight-line handling of the "delta V". The premier Winter 2004 issue of River Jet magazine listed 44 Aluminum Jet Boat Manufacturer throughout the US, but mostly concentrated in Oregon, Washington and Idaho. Most of these aluminum boat manufacturers still produce the modified-delta style or 3rd generation hull. By the way you may be surprised to learn that today`s Aluminum boats weight 25% less than a fiberglass (or FRP) boat of similar size and design.

Fourth Generation. Today`s four leading jet pump manufacturers are Mercury, American Turbine, Kodiak Marine and Hamilton Jet. Mercury produces the entry-level SportJet which is basically their popular out-drive with the prop/lower drive unit replaced by a compact intake-impeller-nozzle jet assembly. (The Rogue Jet Sportwater uses the Mercury SportJet.) American Turbine has developed a lower cost in-board design using a single stage aluminum impeller that is popular in the mid-range priced boats. Kodiak also produces a popular mid-range jet. Meanwhile, Hamilton Jet has continued its 40 years of innovative jet pump design leadership. In the late 90`s Hamilton introduced the 212 High Thrust Marine Jet, which set new standards in reliability and efficiency. Hamilton`s optional stainless-steel turbo impeller further increases efficiency and performance. Today the unquestioned top-of-the-line jet is the Hamilton Jet 212 with the stainless steel Turbo impeller. According to Hamilton this design has 50% greater grip in aerated white water over their non-turbo impellers. Its efficiency is 94% to 95% that of a prop. And because of its lower weight-to-thrust ratio at low rpm, you will also get onto plane 50% to 55% faster than a prop. (This is the standard combination on all Rogue Jet FastWater and WhiteWater models.)

For hull design, experts agree that the current state-of-the-art 4th generation hull is the modified rounded or radiused bottom. Modified-delta hull designers have long recognized that replacing the narrow flat bottom section with a radiused section would produce superior on-water handling and a smoother ride for passenger comfort. But this type of hull requires fabrication technology that most manufacturers simply do not have. Furthermore, it is also more expensive to produce. So in the competitive boat manufacturing business, only 4 of the current 44 manufacturers produce this advantageous 4th generation design. Furthermore, Rogue Jet is the only builder that produces the exclusive tampered-radiused hull with the ½" surfboard keel-plate© and laminar flow jet intake© for additional safety and efficiency. There is nothing else like it on the market at any price.