Perry Design Review: Contour 34SC

Cole Beadon is unique among designers. He not only draws the boat, he constructs the tooling. His latest project is the sharp 34-foot trimaran for Contour Yachts of Ontario, Canada. The Contour 34SC was conceived as a capable offshore cruiser and employs folding, swing-style amas to aid with trailering and storing.

I called Cole and asked him to send me something more detailed than the typical builder's advertising. "Show me the beef." Cole responded with some very interesting technical information. So hang on to your slide rule. We are going to get into some specific jargon. The D/L of this tri is 174 using a 23-foot-2-inch DWL. The amas are 175 percent of total displacement. This means that you could theoretically fly both the windward ama and the main hull without burying the leeward ama. The amas are shaped in such a way that the longitudinal center of buoyancy moves forward as the ama is immersed. This means that the ama's shape will help prevent burying the ama bow as the boat is overpowered. It's not nice to bury the bow of the leeward ama. At the point of full ama immersion, the center of buoyancy has moved to a point that is 45 percent of the DWL aft of the cutwater. Most boats have a longitudinal center of buoyancy located about 52.5 percent aft of the cutwater. This will reduce the possibility of pitchpoling. I hate it when that happens.

The beam-to-length ratio of the main hull is 7:1. As the boat accelerates, the leeward ama is depressed. Cole makes the amas efficient at higher speeds by giving them a high prismatic coefficient of .66 at the half-immersion point. The beam-to-length ratio of the ama is 14:1. The main hull has a prismatic of .61. This is very high compared to the typical .54 you see in most monohulls and indicates very full ends. That's the problem with the simple prismatic coefficient. There is no way of telling where the additional volume is that pushes up the prismatic, i.e. more volume in the bow or the stern.

There are two generally accepted ways of folding a trimaran. You can hinge the amas in a vertical plane, or you can hinge the amas horizontally, as you see here. One of the advantages of folding horizontally is that the orientation of the folded ama to the waterplane remains unchanged. If you leave a vertically folded tri in the water over a period of time, it can grow a real garden on the portion of the ama not protected by bottom paint. The amas are attached to the main hull with akas. These akas use a water stay, or flying wire system, to reduce the bending loads. This means that in the extended position there is a wire stay that runs from the aka-to-ama attachment to a point on the main hull about 12 inches above the water plane. This puts the aka in compression and helps keep things from getting too floppy and squeaky in a seaway. The akas penetrate the main hull 36 inches in the folded-out configuration.

The rig features a double-spreader rotating mast. Rotating masts are nice and help keep a good shape to the mainsail. The jib is self-tacking and North Sails pushes the roach on the mainsail to the limit. The SA/D of this design with moderate roach is 35.1 and that's plenty to give the 34 excellent light-air speed.

Boat Specifications