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Curves, Heartache, and Catamarans

How Alibre Design carved out a nautical niche for Switchsports

This year's release from Switchsports of New Zealand is a kayak with a lot of surprises. At first, the craft seems like the ideal kayak for the seaward fisherman and diver, with specially carved-out compartments that hold paddles and rods, a GPS unit and electronic fish finder, plus deeper spaces to strap in fish bins, dive tanks, and luggage.

What is most surprising about the craft is that, with add-on components, it ceases to be a kayak at all. Clamp on a smaller hull, the Switch Core becomes an outrigger canoe. Or, hook up two Cores in tandem, add a small motor, and you can cruise in a catamaran. On a windy day, remove the motor and attach a 5-meter sail, and it becomes two-man trimaran. If that does not provide you with enough outdoor-rec flexibility, you can drive your Core Kayak to where the action is. With the sail and rubber wheels attached, it transforms into ground transportation that is faster than blokarts and land yachts.

Creating such a modern and modular piece of nautica, however, presented some peculiar challenges that pushed both the designer and the design software into new waters. "My father once told me that anything with curves would cause me heartache," jokes Switchsports owner Stacy Bower. "I'm not too sure he had this project in mind when he said that, but he was right. There aren't too many straight lines on the kayak; our designer did a fantastic job at pushing Alibre Design and himself to new and uncharted design territory."

Last year, Bower took his idea for a multiple-purpose craft to Bay CAD Services Ltd, a design company in Napier, New Zealand. Instead of an engineering package priced in the thousands of dollars, Bay CAD Services made a somewhat surprising choice for the software to create the 3D production model. The design team used the moderately priced Alibre Design.

"Some CAD users think that Alibre Design can't be very good because it's so cheap to buy. How wrong they are," explains Bay CAD Services manager Gordon McDermott. "For anyone needing to create design models and drawings, there is no other CAD program that offers such value for the money. As users of Alibre Design creating models and drawings of mostly agricultural and horticultural machinery, we have never felt the need to change to a more expensive CAD program.

"While many users create simple parts and add these together to form assemblies, building the kayak model showed us that very large, complicated models can also be created with this software."

Although modeling the kayak attachments was straightforward 3D mechanical CAD work, the hull itself was more of an exercise in large-scale sculpture. The kayak is a hollow part, 10 feet long -- more than a hundred times larger than typical 3D models. The hull's smooth ergonomic curves, which include 30 different concavities add significantly to the amount of model detail -- and the bulk of the file size.

As it turns out, the Alibre Design software had no difficultly processing the data of the long hull of the Switch Core kayak. The limitations were found instead in the computer itself. "The design hardware needed upgrading as a result of the project," says Bower. "Bay CAD Services now has a PC capable handling the computing requirements of a small nation."

"The kayak project tested our computers as the file size began to grow," McDermott says. "With the addition of each new feature, we had to change graphics cards and add more RAM. Because the kayak body is one object with many features, the file size grew to a point where there were unacceptable delays in displaying edit changes. Ultimately, the controlling factor was the graphics card. We advise anyone anticipating creating very large files to buy the biggest graphics card they can afford. There is no point in having a fast processing computer if it cannot efficiently convert the data to a displayed image."

Once the initial grief from hardware was overcome, the software sailed. According to McDermott: "There is nothing complicated about achieving such a complex shape so long as you know where you want to add the features." The parametric features in the modeler allowed the designer to easily resize and re-position the boat's compartments without repeating the work of rounding the edges.

The design development progressed from general to specific. First, a basic kayak shape was measured out and sketched. The lofting tool in Alibre Design generated the hull's 3D surface based off of 22 curved profiles of gull-wing shape. "Subsequent shaping was done by adding extruded cuts; smoothing was achieved by adding fillets," explains McDermott.

Another surprising aspect of the Switch Kayak design: the solid modeling work was done almost exclusively by one of McDermott's interns, student engineer Leon Mason, who had only a few months prior experience with Alibre Design when he started the Switch project. "The biggest advantage of Alibre Design is the simplicity of the program," McDermott explains. "We find the program to be logical and intuitive to use, and the efficiency of our drawing production has improved since choosing Alibre Design."

The design team made a few iterations of prototypes to balance the functionality of attachments with the performance of the craft. "Once the functional design was locked down, we spent some time styling the product to give it some visual appeal without compromising its capabilities," says Bower. The final Alibre Design model was exported for rotational molding out of a high-density polyethylene, a common method of kayak manufacture.

The Core Kayak and its convertible configurations are now available in New Zealand and internationally through Switchsports' website, The package will likely hit US stores by early 2007. A vehicle with the versatility of a Swiss army knife is bound to appeal to the avid outdoorsman and the occasional kayaker alike, Bower believes: "The key benefit is flexibility for the outdoor adventurer. They are not restricted to a single activity and can 'switch' from one activity to another quickly and easily. The full system -- (kayak, outrigger, trimaran and land yacht --) can easily be transported on the rooftop of a typical SUV or station wagon.

"The advantage for average kayakers is that they get a well-designed kayak that will retain its value far longer than any other because of the other things it can do. The base design has more potential value than a 'normal' kayak," says Bower. "And kayakers can always add components of the system later on and enjoy a new sport without making their initial investment redundant."