ORCi and Stability for a boat relies on an approved offset file. To obtain the data for this file, a boat’s hull may need to be scanned.

Before an ORCi Certificate and a Stability data sheet can be issued the offset file which describes the shape of the hull and appendages must be approved by the Offshore Racing Congress’s head measurer. If your boat does not have an existing approved offset file, hull scanning will be required. This means the use of laser scanner (LiDAR) to create a 3-dimensional cloud of points.

Scanning is expensive and the data supplied by the scanning experts must meet the specifications of the ORC. If there is a problem, the data can be rejected or the processing delayed while the information is corrected. So, when you plan to get your hull scanned you must have a measurer present to guide the location of freeboard points and the scan targets. These free board positions are critical to obtaining a good outcome from the process. Only points from the bottom of the keel/bulb to just above the sheer line are needed to create the offset file.

To obtain a good scan of the hull the boat and surrounds need some preparation.

• The hull needs to be clean and free of any detritus.
• Position the hull on props/jack stands so that the keel and bulb are as visible as possible. The boat must be held so it remains stable for the duration of the scanning operation.
• Make sure there is enough space around the boat to allow the LiDAR device clear view of the boat on the stands. There should be a minimum of 6 meters clearance all around.
• Typically, the scanning is done from between 6 and 15 different locations around the boat. This is to capture all the hull features accurately.
• Measure and record the chosen forward and aft freeboard points accurately relative to the centreline of the boat from the stem.
• Supply the absolute (x,y,z) coordinates of each of the scan target locations.

Target placement 

It is important that all targets are securely fixed in place and clearly marked so they remain undisturbed throughout the scanning process. Any movement or misplacement of these targets can result in errors in the final hull measurements, leading to costly delays and potential re-scanning. Double-check the alignment and labelling of each target before the scan commences to ensure accuracy and efficiency.

Figure 1 show the placement of a forward target relative to the freeboard. In this situation where the target is directly below the freeboard point the number required are the absolute position (x,y,z) of the target and the height of the freeboard point above the target.

Figure 1: Shows the placement of the forward freeboard point and scanning target.

The aft target (Figure 2), if possible, should be placed directly below the actual freeboard measurement point on the sheer line. However, as this point is normally best placed right on the stern quarter it can be difficult to be directly under. So, in this case the position location needs to be both the vertical distance below the freeboard station and the scanning target location plus the (x,y,z) absolute coordinated of the target.

Figure 2: Aft Freeboard location offset

To learn about ORC and IRC ratings, click here.

By Chris Zonca