Speed is a critical component of long distance cruising, as is a structure that carries a high factor of safety. We also want lots of heeled stability and the ability to recover from a capsize. But there is a conflict between these elements, and it revolves around weight and center of gravity.
The FPB 78s will cruise at 11+ knots several times across the Atlantic before needing a fuel stop. They also have the highest factors of safety of any of the yachts we have done to date. The fuel payload is heavy, as is the structure, so we need to save weight elsewhere to compensate. Cue the interior.
With the FPB 78 Series we are switching to a performance sailing yacht style of interior construction. Head and hull liner panels, furniture modules, and the grounds to which these attach have been put on a diet. The result is a savings of weight and lowering of the vertical center of gravity, both critical to accomplishing our performance goals for the FPB 78s.
The Great Room settee carcass above is a case in point. Panels have lightening holes (which also helps with ventilation), and the other furniture/cabin sole/coaming to which this is attached provides strength. More care in building and installation is required, increasing cost, but the weight savings throughout add up.
Here is another example, the centerline furniture module between the guest cabins aft. Until installed this unit is unstable, so a temporary end panel is used to maintain shape. Once secured in place, the bulkheads to which module is attached stiffen the unit.
With the FPB 78 Series we are going back to foam cored doors. These have not been necessary until now, although we used them on many of our sailing yachts in the past. The weight savings from this are not huge, but this is one small piece of a large effort.
The biggest savings with the highest VCG impact are in the headliner panels. The headliner panels and the grounds system to which they attach have been put on a serious diet, resulting in a 50% reduction in weight. The panels are harder to fabricate and one must take care during installation and removal.
The result of all of this fussing around is a two percent reduction in overall displacement at cruising payload, with a lowering of the VCG by a couple of percent as well, Not much, you are probably thinking.
Here is where it gets interesting. By trading this interior savings for a heavier hull bottom we end up at the same displacement, but since that weight we added back is low in the boat the VCG drops . With the lower VCG we can now reduce lead ballast, and this is a big number. This in turn allows for a larger battery bank (low), heavier propulsion package (also low), and thicker (heavier) insulation.
The end result is a quieter boat (engines and insulation), safer structure (heavier bottom plate), better cruising range and faster ocean crossing speeds (more efficient propulsion package).
All of which stems from putting the interior on a diet.