One of the key design elements in the FPB series is the approach to fuel and water tanks.
With a metal hull, the tanks are integral – the hull itself forming the outer skin of the tanks. In the photo above you are looking into the fuel tanks in the center of the hull, under the great room.
This has two advantages. First, it is possible to have enormous volumes of liquid carried low in the hull, where it assists with stability. Second, the integral tanks create an additional safety factor in collisions. The fuel tank tops, for example, are above the waterline in most load conditions.
Fuel tanks are located below the raised salon, and contain approximately 3200 US gallons (12,000 L) of fuel. They are divided into four tanks. Forward there is a large central tank and two outboard “wing” tanks. The aft section is one large tank.
This arrangement allows for easy trimming of the boat. Wing tanks can be adjusted to trim out any heel, and the fore and aft tanks give good control of longitudinal trim.
Engine Room Day Tank
In addition there is a large “day tank” in the engine room for feeding the engine, genset, and diesel heater.
The day tank is arranged so that it is normally kept half full, and automatically refilled when it reaches the quarter level. Capacity is 410 liters/108 US gallons. When the heavy dinghy is launched the boat will often pick up a slight list to starboard. This can be eliminated by filling the day tank. The photo above shows the forward end of the day tank and its sight gauge.
This huge amount of fuel capacity gives enormous range, obviously more than is probably ever going to be used. So, why this huge capacity?
There are a number of reasons. First, the boat can handle the weight very efficiently. Second, carrying so much fuel offers a wide variety of options for when and where to fill up. If you are in Seattle at the end of the summer and heading south, you can probably save 30% on your fuel bill by waiting to buy until you clear into Mexico in Ensenada. The third reason is emotional. We don’t know about you, but we like knowing that the boat has the ability to go for years without needing fuel, should a disruption in supplies occur.
Fresh Water Tanks
Fresh water tanks are located under the soles of the sleeping cabins. The tops of these are 250mm (10″) below the datum waterline (75,000 pound/34,000kg displacement). The aft fresh water tank holds 750 US gallons (2840 L),
while the forward tank has the capacity to hold 1000 US gallons (3750 L).
That’s way more water than you would normally need for drinking and cleaning given the ability these boats have to make their own water and catch it off their decks. The capacity is there so that you can easily adjust trim and displacement.
Payload and Trim
Bow down trim is more comfortable heading into the waves, while stern down is preferred when surfing. You don’t have to change trim, but if a long passage is in the offing, it is a nice capability offering a smoother ride and the chance to save some fuel through increased efficiency. The variety of fuel and fresh water tanks give you wide trimming latitude.
The FPB series are optimized to cruise heavy. This means you will have maximum comfort with the boat at full load, while still being efficient under power at cruising speed. As fuel is burned the boat gets lighter. This is fine – and more efficient – in protected waters. If you are just powering for short hops, heading downhill in moderate ocean waves, or passaging in protected waters, having the boat light is great. But when you are heading into the waves for days on end, or crossing the ocean with a stiff breeze, those big water tanks, filled so that the boat remains at full load, will be much appreciated.
On the FPB 83, Wind Horse, we’ve found that even in conditions where we don’t need the weight, we tend to fill the water tanks on the last day of a passage (by running the watermaker). This allows us to take long showers and deep baths when we’re at anchor, without worrying about using the watermaker.
To find out more about the FPB 64 contact ToddR@SetSail.com.