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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 ? onsfor Commercial and Marine Applica ? onsSea Horse Systems, LLC Sea Horse Systems, LLC PO Box 53241 PO Box 53241 Lafayette, LA 70505-3241 Lafayette, LA 70505-3241 phone: 337-984-6130 phone: 337-984-6130 fax: 337-456-3099 fax: 337-456-3099 www.seahorsesys.com www.seahorsesys.com info@seahorsesys.com info@seahorsesys.com Sea Horse Sea Horse has introduced the has introduced the only roll molded plastic tank only roll molded plastic tank designed speci À cally for the designed speci À cally for the tug and push boat user. The tug and push boat user. The unit is lightweight, À ts through unit is lightweight, À ts through most doorways, and comes as most doorways, and comes as a complete package that can be a complete package that can be handled by two people for easy handled by two people for easy replacement of older units. This replacement of older units. This new unit has all of the industrial new unit has all of the industrial components found on the steel components found on the steel models but with the advantage models but with the advantage of non-rust proof plastic tanks. of non-rust proof plastic tanks. CMP SeriesSeahorse MN Apr12.indd 13/28/2012 1:42:12 PMwww.marinelink.com MN 43
