From Handmade Prototype to Production: 3D Scanning Lee Stone’s Freestyle Jet Ski Hull

The development process began with a handmade physical prototype. Building a design by hand gives a designer tremendous freedom to shape, adjust, and evaluate a product in the real world. It is especially useful for highly sculpted products such as jet ski hulls, automotive body panels, marine components, and composite tooling.

However, a handmade prototype does not automatically provide the digital information required for manufacturing.

To produce the final jet ski hull and deck, a manufacturer must first create accurate production tooling. That process normally begins with a master pattern, commonly called a plug. The plug can be CNC machined from a suitable tooling material and then used to create the production molds. Those molds are subsequently used to manufacture the finished hull and deck components.

Before any of that can happen, the manufacturer needs an accurate and properly constructed 3D CAD model.

Traditional measurements alone would not be sufficient for this project. The prototype contained complex curves, continuously changing surfaces, blended transitions, and other organic geometry that would be extremely difficult to capture with calipers, rulers, templates, or conventional coordinate measurements.

The most practical solution was to 3D scan the complete prototype.

EMS used a Creaform MetraSCAN BLACK Elite to capture the handmade jet ski prototype. This professional optical 3D scanner allowed our engineers to rapidly collect highly accurate dimensional information across the part’s complex exterior surfaces.

Rather than measuring a limited number of individual points, 3D scanning captures millions of measurements across the complete object. The resulting data creates a detailed digital representation—often called a digital twin—of the physical prototype.

This scanning process records subtle curves, edges, transitions, surface changes, and other features that would be nearly impossible to reproduce accurately using manual measurement methods.

For a complex jet ski hull, that comprehensive coverage is essential. Even relatively small variations in a surface can affect the appearance, fit, hydrodynamic behavior, balance, and manufacturability of the final product.

The 3D scan gave us an extremely detailed digital reference, but the scan itself was only the beginning of the reverse-engineering process.

One of the most common misconceptions about 3D scanning is that the scanner automatically produces a finished, production-ready CAD model.

It does not.

Raw scan data normally consists of millions of measured points. These points can be converted into a polygon mesh made from many small, connected triangles. Although the mesh may closely resemble the original object on the computer screen, it does not contain the clean mathematical surfaces and structured geometry expected in a professional CAD model.

A polygon mesh can be useful for visualization, inspection, reference measurements, and certain additive manufacturing applications. However, it is generally not the ideal format for designing production tooling or making controlled engineering changes.

For manufacturing, Lee Stone needed a true CAD model built with accurate curves, controlled surfaces, smooth transitions, symmetry, and intentional geometry.

Converting the scan into that kind of model required advanced surface modeling.

EMS imported the jet ski scan data into Geomagic Design X, a specialized reverse-engineering software platform designed to help engineers convert 3D scan data into usable CAD geometry.

Creating the completed surface model required approximately two full days of detailed modeling work. Although the process can be condensed and accelerated for a video, the actual work involves a careful series of decisions, evaluations, adjustments, and rebuilds.

We began by separating the scan into logical regions based on the shape and design features of the hull. These region groups helped define where individual surfaces should begin, end, and transition into neighboring geometry.

We then created guide curves using lines, arcs, and splines. These curves followed important feature lines and directional changes found throughout the original prototype. They provided the underlying framework needed to construct the new mathematical surfaces.

Depending on the geometry in a particular area, we used several surface-creation techniques, including:

• Mesh-fit surfaces
• Boundary surfaces
• Lofted surfaces
• Swept surfaces
• Trimmed and extended surfaces
• Standard and variable-radius fillets

No single modeling command could accurately reproduce the entire design. Each section required the most appropriate combination of curves, surfaces, trimming operations, and transition controls.

Building individual surfaces is only part of advanced surface modeling. Those surfaces must also connect properly.

On a complex jet ski hull, a poorly constructed transition could create a visible crease, an uneven reflection, an unwanted flat spot, or an abrupt change in curvature. These issues may affect both the appearance and performance of the finished hull.

Our engineers repeatedly extended, adjusted, smoothed, and trimmed the surfaces to create clean transitions. Fillets and variable-radius fillets were introduced where controlled blends were needed between neighboring features.

We also evaluated tangency and curvature across the model. Tangency helps ensure that two surfaces meet without an obvious directional break. Curvature continuity provides an even smoother and more visually refined transition.

This is especially important for marine designs, where the surfaces must flow naturally across a large, highly contoured form.

Because Stone’s original prototype was built by hand, it naturally contained small surface imperfections and inconsistencies. This is normal for handcrafted models. Even an exceptionally well-made prototype will usually contain minor waves, uneven transitions, localized high or low areas, and differences from one side to the other.

The goal of the reverse-engineering process was not to reproduce every imperfection.

Instead, we needed to preserve Stone’s original design intent while improving the model for appearance, performance, tooling, and repeatable manufacturing.

Our engineers carefully faired and smoothed the CAD surfaces, removing unintended irregularities without changing the defining character of the hull. This required judgment. If the geometry were smoothed too aggressively, important design features could be lost. If every minor imperfection were preserved, those imperfections would be carried directly into the tooling and every production part made from it.

A high-quality reverse-engineered model must strike the proper balance between dimensional accuracy and intelligent design refinement.

Another challenge was that the handmade prototype was not perfectly symmetrical.

Even when a designer intends to build a symmetrical part, small differences will occur during hand fabrication. One side may have a slightly different curve, angle, or surface transition than the other. These variations can be difficult to see without placing the part under a 3D scanner and comparing the two sides digitally.

For the production model, EMS selected and refined the appropriate geometry on one side of the hull. We then mirrored that geometry to create a perfectly symmetrical finished design.

This approach allowed us to retain the strongest elements of the handmade prototype while producing the precise symmetry expected in professional manufacturing.

When the final CAD model was compared with the original scan, the differences between the two sides of the handmade part became clearly visible. Those differences were not scanning errors. They represented the natural asymmetry found in the original physical prototype.

The completed model transformed that handcrafted form into clean, controlled, and repeatable digital geometry.

Accuracy verification was performed throughout the modeling process using the accuracy-analysis tools in Geomagic Design X.

These tools compare the newly created CAD surfaces with the original 3D scan and display the deviations as a color map. The map allows engineers to quickly identify areas where the CAD model is above, below, or within the specified tolerance of the physical prototype.

This feedback is extremely valuable during surface development. It lets us adjust the geometry while the model is being created instead of waiting until the entire design is complete.

However, a completely uniform comparison is not always the objective.

Areas that were intentionally smoothed or corrected may show a greater deviation from the original scan. Mirroring one side of an asymmetrical prototype will also reveal differences when the finished CAD model is compared to the scanned part.

Those differences represent controlled design improvements—not inaccuracies in the reverse-engineering process.

In the final comparison, most of the CAD model remained within the project’s established tolerances. The remaining deviations appeared primarily in areas where the surfaces had been intentionally smoothed, faired, or made symmetrical.

Some software can place a collection of automatically generated surfaces over a polygon mesh. This process is often referred to as auto-surfacing.

Auto-surfacing can be useful in certain applications, but it was not the right approach for this jet ski project. Automatically generated models are typically made from a patchwork of randomly arranged four-sided surfaces. They often reproduce every minor bump and imperfection in the scan while providing little control over the placement of important surface boundaries.

They can also be difficult to edit later.

The Lee Stone jet ski model was created using true advanced surface-modeling methods. Its guide curves, boundaries, blends, and transitions were intentionally constructed around the functional and aesthetic features of the design.

That difference matters when a CAD model will be used to manufacture tooling, modify a product, develop future versions, or serve as the master digital definition of a design.

Advanced surface modeling requires more than knowing how to operate CAD software. It demands an understanding of design intent, manufacturing methods, curvature, tooling requirements, and how complex surfaces behave when changes are made.

Unlike conventional sketch-driven solid modeling, surface modeling frequently requires trial and error. Adjusting one surface can affect several surrounding surfaces, requiring transitions and boundaries to be rebuilt. The work calls for experience in industries where complex surfacing is common, including marine manufacturing, automotive body design, composite tooling, and aerospace.

EMS has been creating complex reverse-engineered CAD models for more than 20 years. That experience allowed us to accurately capture Stone’s prototype while also making the improvements necessary for a refined production model.