Science Checks the Art of Boat Building
FARO Laser Tracker
Good sailing is a matter of balance, experience, instinct and skill, especially in one-design racing, when all the boats are identical. In these events, each boat must conform to its class rules for dimensions, weight, shape and displacement.
The 2004 Olympic Regatta in Athens marked the first appearance of the Yngling-class boats in the women's keelboat event. The fiberglass hulls of these boats are 6.355 meters long, employ an iron keel for stability and are rated to carry up to 500 pounds. The compound curves of a keelboat are not easy to measure with conventional mechanical implements, and a quarter-inch less girth could reduce drag enough to give one boat an advantage.
A metrology consultant from the heartland of American competitive sailing--Newport, Rhode Island--has found a way to make sure that all the boats are evaluated the same way. Andrew Williams, founder of 3D Measure, uses the FARO Laser Tracker, a laser-based coordinate measuring machine, to trace complex hull shapes.
Developed by FARO Technologies Inc. of Lake Mary, Florida, the Tracker can measure large or distant objects (within a 230-ft range) to an accuracy of 0.001 in. To use the system, an operator places the Tracker base on a tripod, and measurements are taken as the target reflector is touched or dragged along the surface to be measured. It projects a beam that the reflector bounces back to the base unit. Simultaneously measuring two angles and the distance to the target, software within the Tracker records the position of each point. If the beam between the Tracker and the target is interrupted, its SuperADM feature allows it to reacquire the beam without returning to a reference point. The sending-receiving unit can be mounted in any position and in almost any environment, from factory floors to remote locations. They're used to align such diverse equipment as ore crushers in gold mines and assembly robots in auto-body plants.
"We cover all the critical points on a hull surface," says Williams. These include center points on the hull, keel shape, keel depth and specific girth sections. The process is simple. Williams sets up the FARO Tracker near a hull to be measured and begins to move the reflective target along the upper gunwale, down the bow, along the keel, and back to the rudder, recording points in software on the laptop computer that accompanies the portable CMM.
When finished, Williams compares the file of what he has just measured to a digital guideline that is based on the original design of the boat. In the computer-aided design (CAD) program, the recorded file becomes like a transparency that is overlaid on the drawings of the original design. Changes--or errors--between the as-built hull and the design become immediately apparent when the two are compared. This way, competitors know when their boat's dimensions are legal--and more important, when they're not.
Olympic races aren't the only nautical uses that 3D Measure has found for the Laser Tracker. Boat builders frequently call Williams' company to verify the shape of a mold for a fiberglass hull, or to enable the builder to re-create plans for a boat if the original blueprints no longer exist.
"Mortification of molds is a common problem," Williams explains. With time, sections of a mold may sag or warp slightly, and this can greatly change the performance of a hull that is formed from it. 3D Measure carries the FARO Tracker to the builder's shop, sets it up next to a questionable mold and, within just an hour or two, can spot areas where the mold is distorted.
In another application, 3D Measure will survey an old boat that a builder needs to restore, copy, or--more often--upgrade. The Tracker is used to make finely detailed tracings of the entire boat, including the hull, keel, rudder, cabin dimensions, etc. The collected file is then transferred to a software "lofting" program and new plans of the boat are generated. Sometimes the process of data transfer goes from model to boat.
"A builder may have a model that he has developed and wants to build," Williams says. "He has checked the hydromechanics of the design, tow tested it for drag and wave making, and wants to build it full scale. Instead of trying to scale up the model and create building plans on his own, it's far simpler for us to scan the model with the Laser Tracker, then let him use our data to create building plans."
For now, however, Williams is working on an entirely different kind of plan: measuring the boats of the world's best sailors.
FARO Laser Tracker
- Measures large or distant objects within a 230-ft range
- Accuracy of 0.001 in.
- Lightweight and portable design makes measurement easy