Q. I have determined that the displacement of my yacht is heavier than that shown in the designer/builder specifications. How does this affect the other CHR MkII data declarations that I need to make?
A. If you are declaring a displacement that is heavier than the designer/builder specification, it follows that your declaration for the LWL that corresponds to that heavier displacement should be longer, and that your declaration for Draft should be deeper, than the designer/builder specified values. One way to quantify the differences in LWL and Draft (DM) would be to estimate the sinkage resulting from the difference between the designer/builder spec and the declared displacement (DSPS). The ‘Pounds per Inch Immersion’ (sink) for most boats can be approximated by: Lbs/in Immer = 1.1*LWL^2. It follows that actual sinkage (in inches) = delta DSPS/Lbs per In Immer. This estimated sinkage would equal to the amount added to the designer/builder specified Draft (DM) in inches , and for most boats multiplying this sinkage by 6 approximates the amount added to the designer/builder specified LWL, also in inches.