True Round Hull
Configerations

The Prototype and Proof of Concept Build was designed with two types of surfaces seporated by a Theoretical Chine line. The surface that runs from the Sheerline to the theoretical chine line is a True Round surface, while the surface from the theoretical chine line to the bottom of the hull was defined as a developable surface. Refer to the below drawing. At that time I thought a two surface design would simplify construction and save construction time.

Since that time, I have come to the realization that combining a True Round surface with a Developable bottom surface serves no real purpose, therefore, I was compelled to redesigned the double surface prototype version of the 'Repllica of Herreshoff's 12.5' to a ‘Single’ surface configuration.

I now feel, that a ‘Single’ surface True Round design configuration has many advantages over any other hull configerations possible using 'Approximate Development' as a design and construction process.

Characterstics that did not change

· Shape and position of the Sheer-line.

· Shape and position of the Fairbody line.

· Location and shape of the Bow.

· Position, shape, and angle of the transom.

· Location and configuration of the Keel and Rudder.

With the forgoing changes there was little or no change in Displacement, Center of Buoyancy, Center of Gravity, Stability, and Design Coefficients.

The following two Illustrations represent the ‘Master Curves’ that define both versions of the Bezier 12.5 overlayed onto each other. It can be seen that there is little difference in hull shape between the two hull configurations.

From a Design Point of View:

The Design Process itself was significantly simplified with the absence of a Theoretical chine.
The longitudinal framing system is less problematic.

From a Construction Point of View:

Welding is simplified – No longitudinal shell plate weld seams.
A single plating method.

The single surface hull form is the least complex from both a design and construction standpoint. Below is the section Lines view of the single surfaced ‘Bezier 12.5.

Preference for a ‘Single Surface’ Hull Configuration:

Double True Round surface hull designs:

A Double Surfaced hull designs combine both an Elementary and Warped surfaces into a single hull design. The design shown is the ‘Prototype’ and 'Proof of Concept' build using Approximate Development.

Here the upper surface is a True Round surface that begins at the sheerline, continues around the turn of the bilge and ends seamlessly and tangent at the theoretical chine line. The theoretical chine line is shown in the Section drawing show below.

A developable surface, then picks up seamlessly and tangent from that theoretical chine line to the centerline at the bottom of the hull.

Triple surface True Round hull designs:

This hull configuration combine two Elementary surfaces and a Warped surface to define the hull. Here the upper surface is an ‘Elementary’ surface defining the freeboard of the hull. It begins at the sheerline and ends seamlessly and tangent to a Warped that defines the center surface at the turn of the bilge, which in turn ends tangent to another Elementary surface that defines the bottom surface of the hull.

In the 'Section' drawing, below, I have labeled the free-form curves at Frames Three, Seven, and Eleven with an approximate radius to demonstrate why this surface is indeed True Round. The drawing showing how the hull changes radius along the length of the hull.

Triple surface Radius Chine hull designs:

The middle surface could be designed with a ‘Single Constant radius’ to becoming a ‘Radius Chine Design’, however using the design criteria for a 'Radius Chine' design, a totally different hull form would emerge as seen below. An eight inch( 8”) and sixteen inch (16”) Single Constant Radius Chine show below were arbitrarily chosen. The Designer can use any radius, but the shape and hydrostatic will certainly change.

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