CAM and the art of boat building

The finished 305 is towed to its first in-water test.

Satellite Beach, FL —After 34 years as a surfboard builder, Doug Wright taught himself naval architecture, got a friend to teach him how to use MicroStation, and set out to build a better speedboat.

Starting out with proven designs for 45-foot catamaran speedboats, Wright says, "I made a few changes, rescaled to 30 feet, and had my basic design for a full tunnel catamaran hull." This boat was a stock class twin outboard, formed with the highest-tech materials he could find, including epoxy, S-2 Glass®, and ATC Corcell. The first design cruised at top speed in the 115 mph range. Under a new company name—Cutting Edge Offshore Raceboats—he designed later versions that can run at 150-160 mph.

Racing speedboats with catamaran hulls come in three different classes determined by their length, and range from 40 ft to smaller boats including Wright's Model 305 (describing its 30 ft, 5 inch length). "This boat differs from others in its class," he says, "because its aerodynamics reflect the advice I got from people in the aerospace design field. The boat has no sharp corners. Everything is curved and smoothed out—and that's why it has proved to be faster than other boats in this class."

Directed by a Mastercam 5-axis toolpath, the XR125 gantry cuts a pass along the starboard sponson at right angles to the curve of the design, giving an optimum pre-handwork finish.

To help obtain funding, Wright made a 1/12th-scale model. The design captured the interest of award-winning racer Alan Butler—a three-time winner of national titles from the American Power Boat Association—who took off a full racing season to work on the boat with Wright.

Wright next had to learn how to model and create the tool path for his design. He chose Mastercam from CNC Software (Tolland, CT), and worked with Daytona Beach Mastercam reseller Jim Gamble to import an IGES translation of his wireframe hull design into the CAM program. Wright says, "While I had no problems with the transfer, if I had had Mastercam at the time I did the initial design, I would have saved time by using its design capabilities rather than a separate CAD package."

Looking down the tunner between the twin hulls reveals the complex 5-axis curves of the sponsons, designed to provide greater lift at higher speeds.

He did use Mastercam's surfacing capabilities, and says that the program "has the best surfacing capabilities I've seen, even with the hull where you can get into some very difficult surface areas."

Wright developed almost 80 separate tool paths for the boat design, bought a Power Systems XR125 CNC gantry machine, and physically created a 4,000-lb. mold for the first hull. The new design competes for sales with the more familiar high-speed "cigarette" boats—but at a cost of $125,000 to buy and $50 a day to fuel the twin outboards, compared to the cigarette boats' purchase price of $250,000 and $600 per day marine fuel requirements.

The twin-hull design out-speeds the traditional design, thanks to the aerodynamic lift of the hull. Wright says that the Model 305 has run in six or seven races as of this writing and has won them all. "It's currently the points leader," he says, "and if it wins its next two or three races, it will place at the top of its category."

Wright now has a back-log of orders, and achieved full-scale manufacturing in September 2000.