Page 43: of Marine News Magazine (July 2012)

however, he added, ?part of the reason we went with propellers is slow speed control.? Jet propulsion, he said, would be dif cult to control at surveying speed.Ultimately, All American Marine, partnered with naval architect Teknicraft and won the bid to build and engineer the boat with the unique quad propeller propulsion design. The builder-designer team proceeded to grapple with how to  t the system into a catamaran hull. OVERCOMING THE DESIGN CHALLENGES?Getting four propellers in a cat hull was a challenge, but it worked out very well,? said de Waal. It also adds to redundancy in the vessel?s systems he pointed out. ?We placed the engines in a staggered con guration - one in front of, and to the side of, the other. One engine faces aft and the other faces forward. This arrangement allowed generous space around each individual engine for servicing and cleared space for the generator to  t in between the main engines.? The vessel design includes two Caterpillar C6.6 170 ekW generators.?Space constraint was a particular problem,? he said, ?but the most challenging was to engineer the propellers and more speci cally the location of the propellers and the rudder to work in unison, considering that the two propellers on each side had to be very closely spaced from each other below the catamaran demi- hull. This created a situation which required signi cant design work, including computational  uid dynamic analysis to ensure that the wake from one propeller is superimposed on the other propeller in a positive order. To maximize ef ciency, we did not locate the propellers side by side, but staggered them at different longitudinal spacings and height. The system had to be designed for various operational scenarios, whereby all four propellers work together at high transit speed, or where one pair of propellers work while the other pair of engines are shut down in other modes of operation. There were many permutations which needed to be considered and solved.? Another unique aspect of the propulsion system is the use of composite instead of steel shafting between the engine and the gearbox. The gearbox is remotely mounted and not attached to the engine.?The composite shaft is far better in terms of noise reduction and its ability to prevent any whipping (shaft vibration),? said de Waal, which is important in research vessel operations. ?There were many different Marine Sanitation SystemsWastewater Treatment Systems Wastewater Treatment Systems for Commercial and Marine Applica
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