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Kayak and Canoe Design Bulletin Board
Re: Design Water Line
Posted By: Nick Schade In Response To: Design Water Line (Arne Haaland)
Date: Wednesday, 18 April 2001, at 9:38 a.m.
The design water line is a somewhat arbitrary point determined by the designer to meet the design requirements. If the design is intended to be used while carrying 100 pounds of gear, the DWL will generally reflect that. At a minimum the DWL should reflect the estimated weight of the boat plus the paddler. But again this may be somewhat arbitrary. Designing for myself, I usually use my weight to determine the DWL. Since other people weigh more or less than me, the DWL may not exactly match their weight.
Just because the displacement might not match what the boat will see when you paddle it, doesn't really matter. The DWL is used for calculating all the other particulars such as waterline length, draft, prismatic coefficient etc. And while changing the DWL will effect these number it won't make a huge difference and can still be used for relative comparison purposes.
Most designs can be used with much different displacements. The DWL is just a point of reference.
The DWL is often initially determined by where the designer thinks it would look good. He then calculates the displacement at the give DWL to see if it meets his needs. He will then adjust the design give a better displacement or he will move the DWL to make it more in line with what the actual displacement will be.
The actual calculation is easiest these days with help from CAD software, but the general task is to find the area below the waterline of several cross-sections along the boat. These cross-section areas are multiplied by the distance between the areas to determine a volume. The volume is proportional to the displacement.
: Can somebody explain how to calculate DWL (Design Water Line)?
: Is the DWL calculated with the kayak's weight, cargo, paddler ?
: Perhaps the DWL is best calculated by a CAD program?
: This lines position must be important when calculating for example
: displacement, length of waterline, beam of waterline.
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