Hi Luc,

It’s a good question.  The short answer is very few parameters are required and they’re easy to change.

The longer answer is as follows:

In the case of the lee hull, the bilge and deck curvature are compound.  The compound shape is developed with a quadratic Bezier curve relying upon 3 offset points: waterline; keel and curvature control (positioned relative to the other 2 and typically located at keel depth and waterline width).  This control point does not need to be changed as the bow radius, or for that matter the rocker of the hull, is adjusted. Consequently, the bow shape is obtained with one simple radius parameter.

I’d like to point out a fundamental issue with KSS.  Topsides must only curve in one plane – non-compounded curvature.  If topside flair is required, either the bow must be raked accordingly or a compounded bow section must be developed.  The designs I’m currently exploring feature vertical topsides though this is not essential.  The solution is either a large area of compounding or a blunt upper bow.

The windward hull stem top is far more complex to develop, but again requires few parameters.  The windward deck join of the w hull maintains a constant radius along its length.  This constant radius necessarily describes the bow stem shape.  The stem shape is obtained from the angle at which the radius intersects the bow.  Given that the leeward deck join of the w hull approaches the bow at a much blunter angle, it becomes necessary to flare this radius along its length. Thus the leeward rail is flared in the lateral direction. Necessarily this leeward join changes from a KSS radius to a compound curve along its length. Parameters required: KSS radius and radius flare factors.

If all this isn’t sufficiently clear, feel free to seek clarification.

David