Q. The ‘Underbody Type’ declaration is new with CRF MkII. Why has this been added to the rating application?
A. Stability and wetted area are critically important performance parameters, but it is not reasonable or practical to ask owners to declare appropriate values for them. The 6 underbody types displayed on the CRF rating application work as surrogates for stability (via related keel volume, VCB and VCG), and for wetted area more directly. In addition, the various underbody type options help account for the advantages of a high aspect ratio fin with separated spade rudder over a lower aspect ratio configurations, including a full keel with an attached rudder.