No aspect of how the FPB Series handle offshore conditions elicits more surprise than their ability to surf. For most powerboats, and all displacement type configurations, surfing brings with it visions of lack of control, broaching, and risk of capsize. Yet the FPBs surf under control, adding speed, reducing fuel burn, and kicking up the needle on the fun meter.

How is this possible?

Lets start with some video. This first short segment is in the South Pacific. Wind and waves are at 150 to 180 degrees to the boat, with 15 to 25 knots of breeze pushing Wind Horse along.

Obviously the FPB 83 Wind Horse is enjoying these conditions. She is moving quickly, under good control, with minimal motion.

There are several factors which contribute to this surfing capability. The first group has to do with steering control, a familiar theme with us as you know. Steering control actually starts with hull shape. The longer and narrower the hull, the more directionally stable it will be. We cannot overemphasize this point enough. If you take a beamy hull to sea, at some point nothing you do with the rudder is going to control the boat. On the other hand, balanced lines and a moderate hull beam require minimal steering input.

Now another video segment, this time off the West Coast of Mexico. In particular, watch the action at the bow in this section. What we want you to notice is the tendency  for the bow to lift  as the boat surfs down the wave. This is  the opposite of what you would expect in a displacement hull form, where the norm is for the bow to bury as it surfs down the wave.

Whether or not the bow buries and how deeply has a huge impact on when you have to stat worrying about loss of control and broaching. A corollary is the at rest shape of the bow. Bows which are deeply immersed tend to lock in and to bow steer (or trip) over their forward sections.

The last part of the surfing paradigm comes from the steering system, and its ability to do the work required to keep the boat on course.  There are two aspects to this. The first is the rudder size, efficiency, and placement. Close proximity to the propeller is a benefit as it keeps the rudder in the accelerated water flow from the prop. The further aft the rudder sits, the more leverage it has. The total area of the rudder and its shape are also key factors. Ideally the rudder will be an airfoil shape for the best  lift profile. It will also have a relatively high aspect ratio (.e. it should be deep and not too wide fore and aft). Aspect ratio has a huge impact on efficiency. 

The photo above is of the FPB 83. There are two of these rudders of course, and the total area relative to the forces required to turn the boat is about twice the industry norm.

Now the FPB 64. This rudder is almost the same size as the combined area of the two on the FPB 83. In scale, this provides the shorter FPB 64 with even more turning force. Notice the close spacing of rudder to prop on both boats. These are NACA four digit foil shapes.

The second part of the steering system is the autopilot. This needs to be quick acting which translates to powerful, and have the smarts to use fast rudder rates of travel without getting confused and S-curving.

Here is a recap. Downwind control and the ability to surf are important because:

• It is faster and fuel burn is reduced.
• Surfing under control reduces wave influence on motion.
• Allows a wider range of conditions in which you can proceed on a downwind course.
• Adds an important capability to  heavy weather tactics that can be a key factor when dealing with tropical storms.
• Surfing under control is fun!

The design characteristics that lend themselves to surfing under control are:

• Moderate beam to length ratio (less beam for a given waterline is better).
• Balanced lines, so the distribution of volume remains similar as the hull heels.
• Shallow forefoot to avoid bow steering.
• Large, efficient foil shaped rudder in close proximity to the propeller(s).

We’ll leave you with a long section of surfing video.

There are lots more videos available by clicking here.