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January 2012 www.sname.org/sname/mt at anchor as the chine line came out of the water. ere were a lot of discussions on spray rails, but we decided to retain it on this vessel. However, we brought it all the way back and faded it out at about midship above the waterline, which would eliminate the slapping. We started this hull at 180 ft. in length, and then stretched it for these customers, who always want to go bigger. We kept the molded depth at 14 ft. 6 in., whereas our old 50 m boats were 13 ft., 9 in. at gave us a little extra headroom for engines, guests, piping, and so froth. We did the calculations and put in 3516?s (Caterpillar diesel engines), giving us a 20-knot boat based on the model test data. We found we had a lot of distance from the vertical center of gravity to the metacenter (the relative buoyancy properties) in the hull. is was a good thing, because we found them putting more and more tenders and toys and heavier things up top. We also were over 500 gross tons, so things such as enclosed ybridges could be included without having to worry about stability or volume. At rst, the four hulls were going to be identical. We put the same engine package in each hull. But, of course, as we started getting into it, all of the hulls grew in size; one hull actually had the depth increased by 30 inches. We put three-foot steps forward in the hull, so it?s fundamentally a much larger boat. However, the beam remained the same. Shared goal One of the shared goals of the four owners was to run with xed-pitch wheels and conventional power rather than anything exotic. e big dierence between them is the generator size. On the rst hull, we had 235 kW generators, while on the other three we installed 280 kW units. e increased power requirements meant that we had to put a load bank on them. We also needed to have the right deadrise on the hull. We needed to have tunnels to keep the draft down, yet still allow for enough tip clearance to get ecient propeller ow. In addition, we had to have a fairly ne bow and a good skeg for directional stability. We tested that to ensure the skeg was up to the task, because in our previous boats, we had had some issues with the skeg length. On later boats, we actually increased the length of the skeg. Tests revealed that, due to the framing system and what we?ve chosen in other areas, this is a very smooth- riding boat. We believe the spray rail and the rolled bilge were innovative for this type of hull. It may not be the rst time it?s been done, but we were able to put it all together in a hull that met the customer?s needs: the draft, the speed, the capability of doing additional ser- vices, additional tenders, and enclosing a y bridge if desired. It oered the customer a lot of exibility. Another challenge we faced is that everybody wants bigger windows. e challenge is how to incorporate all these large windows while still meeting the strength requirements for ABS, and while building a practical boat that works as intended. You have a forward own- er?s suite, which is just above the top foredeck, and then you have the pilothouse above that, and all that area under the pilothouse is windows. en you have all the side decks. ere?s nothing but windows on the main deck. You also have bathtub sliding doors that are all windows. Everybody wants to minimize structure and maximize viewing area, but you still have to work At 191 ft. in overall length, Carpe Diem is powered by two Caterpillar 3516C engines. Carpe Diem has a fuel capacity of more than 23,000 gallons. e client wanted water jets, so the hull transom was designed and tested for submerged jet application. 38_41_VesselReport_SNAME_Jan12_P2.indd 3912/22/11 3:40 PM