{"id":11241,"date":"2010-05-07T00:00:37","date_gmt":"2010-05-07T05:00:37","guid":{"rendered":"https:\/\/setsail.com\/fpb-64-series-the-motion-equation-2-2\/"},"modified":"2011-10-03T20:37:15","modified_gmt":"2011-10-04T01:37:15","slug":"fpb-64-series-the-motion-equation-2-2","status":"publish","type":"post","link":"https:\/\/setsail.com\/fpb-64-series-the-motion-equation-2-2\/","title":{"rendered":"FPB 64 Series – The Motion Equation – Being Comfortable and Secure"},"content":{"rendered":"

We’ve been watching video brought to us by the Owners of Avatar<\/em>, the first FPB 64. It has long and steady shots of Avatar<\/em> heading upwind with waves on the bow quarter. In discussing what the video shows with current Owners, it was suggested that a recap of the design of the FPB Series and how this impacts comfort, and safety might be in order. Now that we have the ability to embed video within these blogs it will be a lot easier to illustrate the design concepts.<\/p>\n

This is a long article, with lots of video, so make yourself comfortable and prepare to do some passaging with us aboard Wind Horse<\/em> and Avatar<\/em>.<\/p>\n

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Going Places<\/strong><\/p>\n

From many hundreds of thousands of offshore miles on our own and the experience of our Owners over the years, we know that the key to successful cruising is physical comfort and emotional security. With both of these bases covered, making the passages required to get to new cruising grounds becomes a pleasure (most of the time) rather than something to be endured (or feared). Result: you go more places. We have described the structural approach used with the FPB Series and its factors of safety elsewhere. What we want to concentrate on now is the motion equation.<\/p>\n

Tradeoffs<\/strong><\/p>\n

There are no simple rules or design parameters which dictate how to make a safe, comfortable, ocean crossing yacht. With a multitude of wave shapes and sizes, not to mention crossing wave patterns, the overall situation from a design perspective is chaotic. What we want as owners is a vessel which is an all around design that can cope with a variety of situations<\/em>.<\/p>\n

Designs need to start somewhere and for us this is ultimate<\/em> stability in extreme weather. In particular we are talking about the ability to handle a breaking sea and with the inherent capacity to recover a full knockdown or capsize. The FPB’s ability to return to upright from a capsize forms the baseline from which all other design aspects flow.<\/p>\n

The second design criteria is the ability to maintain cruising speed throughout a wide range of adverse conditions. This affects both comfort and safety. Boat speed reduces weather risks and fast passages are almost always more comfortable than going slowly.<\/p>\n

Reduced passage time goes hand in hand with weather tactics. The characteristics which allow you to proceed quickly, even in adverse sea states, also make available a wide variety of weather tactics. All of this, comfort, boat speed, and heavy weather tactics come down to a single factor – steering control. This is the most difficult of all design parameters to get right. You need good control downwind, with seas on the quarter or dead behind you, at the same time you want a fine bow for slicing upwind. The hull shape that does well downwind is not going to be optimized for going uphill, and visa versa. We’ll cover this in more depth a little later on.<\/p>\n

Comfort is a complex question, and comfort at sea and in port are not always arrived at in the same manner. If there has to be a tradeoff between these two scenarios and the goal is long distance cruising, the design should be optimized for the ocean rather than the marina.<\/p>\n

When you mix these baseline issues with the thousands of decisions that are made in a yacht design there are going to be tradeoffs. The key, for us as designers, and you as owners, is to be clear about the goals for the yacht, and maintain a consistent approach towards this end.<\/p>\n

In the text which follows you will find embedded sections of video. These run a minute or two in length. Clicking on the box in the lower right hand corner will play them full screen. Keep in mind when viewing these that the camera shrinks your perception of wave size, typically by a third or more. If you want to see the full length videos from which these are extracted there is a link at the bottom of this article.<\/p>\n

There are a couple of things to watch for in these videos:<\/p>\n