: Paul, don't worry about flame wars. I WAS trying to stir things up a little
: with MY comments. This is a great subject to discuss, that really makes
: people think, and the dialogue so far has been great.

I was happy to let this thread die, but following your post, decided to shed some light on how anthropometric measurements are actually used. Side-stepping the issue of "what is best", I hope you find the following text informative and thought provoking. Despite appearances, I tried to keep this as brief as possible to the point of oversimplification.

In many modern kayak building methods the design is fully embodied by the cross-sectional forms. This is not the case for traditional kayak building and you have to change your mindset to understand it. The building process is as important as the measurements themselves and cannot be taken out of context and viewed independently. Most of the anthro measurements do not define a finished length outright, but only add an offset to a fixed distance (such as your hips or the width of the gunwale at a specific point). A few measurements simply ensure consistent spacing of components and extreme precision is not necessary.

Traditional building revolves around the gunwales and to a large degree native building techniques work simply because it is difficult to bend the gunwales into a terribly bad shape for a kayak. I am surprised that this concept, rather than the "measurements" is not the cause for controversy. The gunwales are angled, which creates sheer (the ends rise), as the boards are bowed. The shape is then tweaked by pushing desired fullness into the ends. After this is completed, most additional measurements and tasks are primarily based on the completed shape of the gunwales, not the body. For this reason, the components can't be measured by various "body measurements" and cut prior to assembly. Once you pinch the ends of the gunwales and spread them to your calculated beam width (hips plus clearance), you can step into the frame and interact directly, right from the start. If the fit is tight, tweak it. Each rib in a traditional kayak is a slightly different length, but these lengths are not determined by a number of different body measurements. The length of each rib is governed primarily by the width of the gunwales, where it will be installed, plus a small anthrometrically determined "constant" added to achieve the desired depth. The anthro measurement to create the estimated depth is usually performed by using finger widths. While it is true that different people would derive a slightly different offset, and thus rib length, in use this is not a problem since you install a few ribs in the kayak, test the depth and foot room, and then tweak the offset as needed. Since the building process depends on intuition and allows testing and tweaking it can handle a wide range of scaling issues for personal variance. Of course, the freedom you have in building can work both ways and there is a great deal of knowledge that only comes from experience.

One measurement that is not intuitive and evokes criticism of being "magic" is using three arms-spans (or three times your height) for an approximate length. This is only a rough guide, but when I apply this measurement it comes within 2" of my favorite commercial kayak. All of the measurements are only guides, but they do indicate to you whether or not you are staying reasonably close to the original design or are venturing off into new territory.

If you do choose to use some of the traditional measurements with modern materials, ensure that you understand how the measurements are taken. For example, if you apply the "hips plus a fist on each side" (defines beam with enough room to move but not get displaced) to a strip boat, your kayak would be narrower than a corresponding skin boat. Why? On a skin boat this measurement is applied to the inside of the gunwales and since the gunwales are ½" to ¾" thick, this could make a non-trivial difference.

All designing and building is a blend of art and science, intuition and numbers, and different building methods allow you a choice. If you are building for the masses and need to ensure that the design can handle x pounds of paddler and gear, then you would not use the traditional method. On the other hand, if you are building a custom tailored kayak for a single individual, who wants a kayak with the attributes and proportions very close to a Greenland kayak (or Aleut, etc), then the traditional methods will allow you to do just that without expensive modeling equipment or mathematics.

Greg Stamer