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operational scenarios to cope with in terms of propeller design,? he said. Consideration had to be given to the increased drag created by the vessel?s long range fuel tanks and the heavy loads that may be carried for some types of operations. Propeller placement also had to take into account retrieval of the AUV. ?It?s quite tricky to get it back on board especially in rough seas because it gets very close to the stern of the boat,? said de Waal. Consequently the propellers also had to be placed well away from the transom. THE BENEFITS & SYSTEM SPECS ?We designed the vessel to have a very speci c two-week mission plan,? said Croft. ?It has the engine con guration to leave the dock and transit to the work site at top speed.? This, he explained, is accomplished with all four engines online. ?Then we shut off the two larger engines and run on the smaller engines for fuel economy during the two weeks on the survey site.? Finally, all four engines are brought back online to transit back home at full speed. Fast transit gives the company more time on the survey site and allows them to go farther and be more competitive in the bidding process. ?A work site that used to take a day and a half to get to will now take half to three-quarters of a day,? said Croft. ?It lets us reap the bene ts of time and money.? Nic de Waal, Managing Director at Teknicraft Design in Auckland New Zealand was the main architect on the job. ?The particular application of this propulsion is for a vessel that needs to operate at large variations in speed,? he said. ?In this case, the vessel needs to transit to the survey area, which may be 100 nautical miles out to sea, at high speed, but once it arrives and start survey operations, it could be operating at displacement speed or lower for up to 300 hours non-stop. The quad propeller design allows the vessel to operate at maximum ef ciency in both modes of operation.? The propulsion package includes two Caterpillar C32 ACERT 1600 bhp engines mated to two ZF 3055A transmissions and two C18 ACERT 553 bhp engines mated to two ZF 550V transmissions. ZF Marine also provided the A drawing of the quad propeller propulsion system installed in the R/V Sea Scout?s catamaran hull. . Provided by Teknicraft Design 44 MNJuly 2012