Measuring the hull of a sailboat for a mathematical calculation of resistance

Short project presentation

The project of digitizing and mathematically calculating the resistance of a sailboat’s hull represents an innovative approach in applying the Flexijet 3D device. The project’s goal was to measure the sailboat’s hull for the mathematical calculation of resistance needed for competition in ORC Championship races. This task requires precision and technological sophistication, considering the complexity of the sailboat hull’s geometry and the need for a detailed analysis of hydrodynamic properties.

Measuring the Sailboat Hull

Project participants

Studio Element d.o.o.,
Dolac 1, Zagreb, Hrvatska
[email protected]

Measurement: Edo Aganović

Measuring the sailboat hull



The process commenced with a thorough measurement of the sailboat hull using the Flexijet 3D device. Measurements were taken at specific positions on both the right and left sides of the hull to ensure maximum data precision.



After completing the measurements, the obtained data was converted into digital format and exported to an Excel spreadsheet. These data were then imported into a specialized application for calculating the resistance of the sailboat hull, utilizing mathematical models and algorithms.



Results from this project provided a detailed insight into the geometry of the sailboat hull and its associated components, enabling accurate calculations of hydrodynamic forces related to lift and resistance. This information is crucial for generating ORC Rating certificates and for computing the sailboat’s polar speeds.


The state-of-the-art technology in ship hull measurement and digitization

Hull and appendage shapes and geometries is one of the most important factors for predicting a boat’s performance. Not just point measurements as waterline while sailing, but complete information ableto return displacement, wetted surface, and the volume distribution along the hull. This and appendage shapes and positions are the basis from which hydrodynamic forces of lift and drag can be calculated can be calculated through the Lines Processing Program (LPP) that gives all the relevant hydrostatics data used by the Velocity Prediction Program (VPP) to generate ORC Rating certificates and their polar speeds. At the beginning of the IMS during the the 1980’s and 1990’s, special hull measurement instruments were developed to take hundreds of points on the hull organized in the “offset” file, a way to describe the hull geometry that remains today in use for ORC International and ORC Club certificates as well as recently introduced in ORC Superyacht and ORC Multihull certificates. Nowadays, the latest laser technology has introduced new instruments that can be used with sufficient accuracy and affordability to make the hull scanning measurement in the field much quicker. This guide is intended to give basic instructions on how to capture the geometry of the hull with its appendages with a 3D scanner and provide a cloud of points that can be processed by the ORC Technical Staff to generate a hull offset file.

An offset file of the hull

An offset file (.OFF) describes the body plan of the hull together with appendages. It contains points distributed on consecutive vertical transverse sections along the length of the boat, within the coordinates system defined as follows: a) X axis – longitudinal with 0 at stem and positive towards the stern b) Y axis – transverse with 0 at the centerline and positive outwards c) Z axis – vertical with 0 at the waterline and positive upwards Each station is defined by its X, the number of points, a side code and a special code, and is followed by a sequence of Z, Y coordinates for each point on that station, ordered from the bottom at centreline up to the sheer at side.

Do you have space that needs to be measured?

Whether you have a more or less complicated space that needs quality measurement, or you want to be able to measure your clients’ spaces independently – we can offer you a whole range of services:

a) you can contract a 3D measurement service with us,
b) we can also offer you the service of designing furniture, technical preparation for
production, creating programs for CNC machines,
c) you can also buy a Flexijet device from us – with all its software and hardware accessories.

We invite you to contact us for more details about our service and products – we will be
happy to provide you with all the necessary answers.