To A New Paradigm With FPB

FPB 64 “Avatar” Final Trial – Part Three Of Three

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We’ve now received a few selected images from Ivor Wilkins in high resolution (the source files are 60mb each!), so we are able to crop in really tight and dissect what is going on. We’ll start with this shot and look at the bow and stern a little closer (if you are just joining us there are two preceding blogs which should be read first. At the end of each is a link to a slide show that will allow you to study these photos full screen).

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The bow is cutting nicely through the wave. There is a lot of spray, but no solid water on deck. The bow has not yet lifted.

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In really tight here. This wave is large but not as steep as those which bury the anchor..

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The stern is just slightly depressed.

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Now one of the more amazing photos we have seen. There is clearly a lot of boat out of the water.

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The key item here is the fact that the boat is horizontal. While the wave has left the hull suspended, it wasn’t big enough to pitch the bow up.

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The stern appears to be barely immersed. Essentially the boat is airborne, with a soft landing yet to come.

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Now another cool series. This image, which you have seen before, is our favorite.

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In tighter now and we can see that while the crest is at the level of the middle lifeline, the penetration of the wave has been clean. The upper hull volume is sufficient to keep the bow level, yet not so great as to create a huge amount of drag.

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A really close look. While this appears dramatic, there is very little water about to come aboard, just that small wedge forward of the pulpit.

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From this angle it is hard to quantify the stern, but we’d guess it is depressed,  perhaps a foot/300mm.

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Now a more normally-shaped sea, this one about six feet/1.85m.

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A really good shot of the bow penetrating the wave cleanly, with minimal fuss.

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The stern appears to be on its normal lines.

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Another wave uphill.

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This is a little larger than the previous wave.

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As the wide photo shows the hull essentially flat the wave climbing the stern must be a preceding crest, so two very closely spaced seas. If the stern were fatter, that extra buoyancy would force the bow down and into the oncoming wave.

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An overhead view this time.

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Same situation. A bit  of spray, but nothing substantial coming on deck. Note the anchor is fully immersed.

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The stern once again  has a wave climbing the topsides, but since trim appears flat the wave is not able to get a grip on the hull.

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Surf’s up and it is time to have some fun with these waves.

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Note how much bow is out of the water. Essentially she is flying all the way back to the watertight bulkhead.

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Meanwhile the back end is essentially on a normal floatation plane.

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Still surfing, this time looking directly at the bow.

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The hard part of the design cycle is getting the balance right between upwind penetration and downwind buoyancy.

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One of our favorite shots from the series. The FPB 64 is starting to really smoke here.

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The bow has yet to emerge from the wave, but you can see how she has on a head of steam (guessing fourteen or maybe fifteen knots).

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Notice how the stern has dropped here. That is because at these speeds she wants more volume and a flatter run aft. If we were optimizing for just these conditions we could squeeze another couple of knots out of the surfs. But we’d  pay a penalty in everyday efficiency and upwind comfort.

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We’ll leave you with this, the owner’s favorite.

A slide show with full sized images is here.


Posted by Steve Dashew  (July 17, 2010)




3 Responses to “FPB 64 “Avatar” Final Trial – Part Three Of Three”

  1. Conrad Says:
    Hi there Steve. Every time I look at these photos – and I find I keep going back to admire them – I feel less and less inclined to dare venture out in my own boat!!! Question: the large hatch over your forepeak area looks vulnerable, as in anything solid flying around there – an errant anchor for example – during heavy seas could shatter it. Would not a solid hatch such as those incorporated in the new stern extension be more suitable?

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    Steve Dashew Reply:

    That fordeck hatch is a heavy cast aluminum framework, with short unsupported spans and a Lexan lens, which is extra thick per our specification. We have used these on the foredecks of our yachts for 30+ years and are not aware of any problems. We should add that these cost multiples of the standard acrylic lens hatches, but in return do not leak!

    [Reply]


  2. Conrad Says:
    Thanks Steve – the hatch design is clearly one of your many un-obvious (pardon my neologism)features that have had deep investigation! Of all of the photos you have published re the 64, the next to last/penultimate photo here is my favourite. One can just feel the boat settling softly after a good surf.

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