The Next FPB – A Breath Of Fresh Air


When you start to consider powerboat (stinkpot) systems, virtually every decision revolves around air conditioning. Air conditioning holds you hostage. High heat loads from large windows and poor-to-nonexistent shading, coupled with a lack of ventilation, force you to fit large compressors, which means a big genset. Since you cannot do without the genset, you need a second, both of which are too big to just run air conditioning at night, so a small night generator is needed.  All other systems decisions flow from this conundrum.

But what if you had good ventilation, even when there was no breeze, and then coupled this with minimized heat loads?

The  photo above gives a hint of the integrated ventilation system that will come with the new FPB. It works in rain, and when it is calm, with minimal power drain.

Those water shedding vents between the pickle forks receive an accelerated volume of air thanks to the shape of the bow, the coamings, house and overhangs.

The plate that overhangs contributes to this acceleration. It also acts as a seat bottom, and when hinged down provides a storm cover.


This feeds through a giant dorade box, spanning the full three meters (10 feet) between the coamings. The combination of water shedding grills and dorade trap means there is minimal risk of water ingress into the interior. And there is a hinged closure lid to seal the grill at sea.  This system will deliver more air flow to the great room than three of the giant Bomar 160 hatches we normally use, and it will do it in a downpour to boot.

And what of the staterooms? This gets even more interesting.


You are looking here at a section through the coamings on which the great room structure resides. There are a series of dorade boxes integrated into the structure. Each has our standard downpipe detail of a closure plate to adjust air flow and seal the pipe in extreme conditions. Notice the box alongside.


This box has a water shedding grill and a highly efficient, nearly silent MSR muffin fan. The fan is rated at 100 CFM (no flow restriction), with a power consumption of .18 amps at 24 VDC. Sound rating is 38dB.

Think of this in the context of a typical stateroom with attached head compartment.

wicked fpb eyeball vent 2.jpg

One of these units draws out of the head and a second blows into the stateroom, aimed at your head and shoulders, providing a gentle, silent caress. As for net friction, we are guessing 150 combined CFM sounds in the ballpark, sufficient for eight to ten air changes per hour. You can run the two of these units half a day for a 103 watts. Even if you had half a dozen of them going 24 hours a day the power consumed, as a percentage of the total, would be insignificant.

There are two other factors that will significantly reduce heat load below. The structural system provides an air gap of 150mm/6″ between the insulated hull and interior hull and head liners. The air pocket so formed makes a wonderful thermal barrier.


The great room windows are slanted outward, and between their angle and the additional overhang, we have what are in effect built-in awnings. Not enough for your climate late in the day? A simple short, vertical awning from the overhang to the rail takes care of that.

This new FPB will benefit in a number of ways from what we’ve been discussing. First, the need for air conditioning will be substantially reduced. Next, when you do want air, much smaller compressors will do the job with lower power requirements. In many situations we expect the solar panels will provide sufficient power to run stateroom air conditioners during the evening with minimal impact on battery capacity.

There are many other components to this approach which we shall detail shortly.

For more information on the FPB Series, e-mail Sue Grant: Sue.Grant@Berthon.Co.UK.

Posted by Steve Dashew  (January 28, 2012)

16 Responses to “The Next FPB – A Breath Of Fresh Air”

  1. Alain M Says:

    Hi Steve,

    Great!!! I just not understand why some other boat on this size range never had this kind of air system!!!
    We do it for house since many years!!! I know it is about taking of the shelves, but sometimes we have to do it from scratch, it’s more efficient, more costly sometimes, sure, but not so that many though…
    And one way to take back part of the energy from the hot or cold air flow who goes out the boat???
    Waiting the next!!!

  2. Jay Vincens Says:

    Steve this is GORGEOUS !!!

    Jay Vincens

  3. Raj A Says:

    Wow. I like where this is going.
    Does this design also raise the height of the basement?


  4. Steve B Says:

    Does the hinged closure lid make a watertight seal in case of capsize? These ideas are looking sooo good for sunny climes.

  5. Steve Dashew Says:

    Yes, Steve:
    There are two layers for sealing. The hinged panel is one (bolted into place). And their will be seal plates in the interior as well.

  6. Steve B Says:

    Hi Steve,

    Have you considered installing an evaporative cooler (with a similar configuration as the giant dorade)on the roof of the great room, ahead of the fly-bridge? For the cost of running a small re-circulating water pump (which could probably be wind driven) you could dump chilled air straight into the great room below. It could be great for hot, dry climates, but I guess you would need to be careful not to get too much moisture (read mold)in the tropics.

    Looking forward to more of the reveal!

  7. Steve Dashew Says:

    Hi Steve:
    They are common here in Arizona. But not sure the benefits would be worth the hassle on a boat unless you were somewhere like Baja or the Red Sea, and then you would need to make the fresh water.

  8. Alain M Says:

    The evaporative cooler works very well in HOT and DRY environment, but they just don’t work in wet environment. As seas are a wet environment, forget it….

  9. Anthony VDM Says:

    Hi Steve,
    With the solar array on the rooftop, there is no longer provision for a (couple) of ventilation hatches to the great room.
    Whilst I appreciate that your new fresh air delivery system will of course be better in rain or inclement weather, are you confident that your new ventilation design will be sufficient in temperate climates in that zone between needing the A/C and not needing it.


  10. Steve Dashew Says:

    The great room should have as good a ventilation as we are used to, without the heat load of the hatches, in a wider range of conditions. In some situations, where more than usual wind s hear is present in light winds, we may be a little less. Overall, it should be an improvement.

  11. RayG Says:

    There is still the hatch under the flybridge thas is over over the galley or at least the possiblity of it.

  12. Steve Dashew Says:

    The galley has an extraction system to work in conjunction with the vent forward. Because of the headroom, and structural depth, a deck hatch is not practical.

  13. Vasko Minev Says:

    Hi Steve,
    May be is too early to ask, but I’m so exited with the new design!
    Is it possible for the future the FPB 64’s to adopte the same exterior vision and the new and improuved systems designed for Wicked FPB. For some of us 30m boat is too much.
    S/Y Nirvana /Bulgaria

  14. Steve Dashew Says:

    Hi Vasko:
    It takes a much larger hull to make the look of the FPB 97 work. So, I doubt we’ll be able to change.

  15. Hoovenson Haw Says:


    I have noticed that the three water shedding grills between the pickle forks are absent in the “Iceberg”. Is it no longer needed for ventilation or owner’s request that they be deleted?

    I enjoy reading the blog posts past & present.


  16. Steve Dashew Says:

    The inlet grills that were originally to be placed in the coaming on the FPB 97 were moved to the underside of the roof overhang (same detail as the FPB 78). This is a more difficult instalation in terms of structural integration, but reduces the water loading that would have occured occasionally.