The Hull Truth
FasTrac, SureTrac, Z-Trak, Z-Plane—the world of hull design is a hive of buzz phrases. But what they really mean could be a telltale sign of which boat to buy, or not to buy.

9 TERMS
FOR LAYMEN

PLANING HULL A hull designed to ride across the top of the wter, rather than plow through it (as does a dispalcement hull like a pontoon)
STEPPED HULL A hull with a trough that runs from the outer chine all the way to the keel, creating seperate forward and aft surfaces. The junction of the two appears as a stair step.
TRI-HULL A V-hull with two additional outside hulls; also call gull-wing hull. This might be found in a deck boat or catamaran.
V-HULL A boat with an pointed bow and V-shaped bottom, at least in its forward section, for cutting through the water and softening the ride.
CHINE Where the side of the boat transitions to the bottom of the boat, creating a corner. The shaper the corner, the "harder" the chine and the stronger the bite in turns.
REVERSE CHINE A two-corner chine; before the bottom meets the side, it forms and upside-down V-shape to deflect spray away from the boat.
KEEL The centerline, or spine of a boat. The sharper the keel's angle (deadrise), the softer the ride—though sometimes at a cost in speed.
PAD A flat or nearly flat area on the running surface toward the back of the boat.
STRAKES Horizontal or nearly horizontal lengthwise surfaces that help lift the boat onto plane.

Oooh, the clean sweeps and crisp lines of those boats. Such style! You'll see a lot of that on these pages. But hull design is not just a matter of style. At least it shouldn't be.

A boat hull has all sorts of shapes, bends, fins and grooves—things you can see most clearly when the boat's on the trailer. Surely, you've wondered: Why the hull do the makers do that?

Well, they do it because a deep-V hull is seaworthy but slow, and a flat-bottom is fast but flakey. Finding a blend of seaworthiness and speed has become a tantalizing challenge for some builders. Here's how a few standouts have gone about it with their own trademark design.

Case study:
Stingray's Z-Plane Hull
Stingray president Al Fink once said his goal was "to make a boat as fast as it can be, but safe and easy enough for your grandmother to drive."

Stingray, which introduced its CAD-designed and patented hull in 1989, knows plenty about the pluses and minuses of the V-bottom boats with lifting strakes. Typically, lifting strakes are roughly parallel to the water's surface and the keel—until the boat turns, when they dig in and force the driver to slow down. They also create air bubbles in the water, reducing the propeller's bite. Lowering the motor helps, but that creates drag. Speed is lost.

The Z-Plane Hull minimizes these problems by avoiding right-angled strakes. The hull's running surface is actually three shapes nested, becoming steeper as they approach the chine. These running surfaces have strakes that vary from right angles by about five degrees.

The result? Less unwanted grab and ventilation in turns. The motor can be mounted higher, which reduces grag. Drive, Grandma.

The Stingray Z-Plane hull was feature in this story, along with 6 other hull designs.

by Steve Griffin
Boating Life Magazine
January 2008





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