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A patent-pending hull shape

Shannon Yachts has a new hull design that it says marks a departure from conventional planing and displacement powerboats. The Shannon 38 SRD uses reverse deadrise — as opposed to the traditional positive deadrise or convex hull shape of most boats — in the aft hull sections.

Walter Schulz, Shannon’s founder and chief designer, says the inverted aft sections of the 38 SRD, or Schulz Reverse Deadrise, provide tremendous lift. The forward sections have a vee-shaped entry that Schulz twists amidships and creates a laminar flow that prevents suction at the aft concave sections.

Schulz is known for shallow-draft designs such as the Shannon Shoalsailer 32, a monohull sailboat that draws only 30 inches with the daggerboards up or down. He says the 38 SRD’s main attributes are its shallow draft, fuel efficiency and offshore performance.

It took three years for Schulz to develop the patent-pending design, which he says incorporates the best elements of planing, semidisplacement and displacement hulls, while eliminating their worst qualities.

“I designed it to go offshore,” says Schulz. “I think everyone is surprised by the motion in a chop.”

Schulz says he has noticed the boat’s fuel efficiency tends to spark initial interest in his boat. “Everybody’s touting fuel economy at the moment,” he says, adding that some of the claims in the industry make it difficult for customers to know what to believe. Because of this, Shannon equipped his demo boat with fuel burn gauges.

However, Schulz says the 38 SRD’s fuel efficiency becomes apparent when comparing the small size of the engines with the boat’s speed and performance. A pair of 150-hp diesels push the 38 SRD to more than 25 mph, which he says is about half the horsepower necessary for other boats in its class. It cruised at around 20 mph and burned 11 gallons per hour with that setup. (Standard power now is 160-hp diesels.)

The fuel efficiency brings customers in the door, but Schulz says people are buying the boat for its motion on the water.

“The SRD does not [roll] because of the concave sections,” says Schulz. In fact, he says he experienced no rolling in 2-foot beam seas. Comfort at rest has also been impressive, he says.

Schulz says he has a simple test for grading a boat’s performance in sloppy conditions. “If you can get below and use the head and make coffee then it’s a success,” he says. Indeed, Schulz says he was able to make coffee aboard the 38 SRD in a 3-foot chop and winds gusting to 30 knots.

The boat handles like a conventional vee bottom, Schulz says, and it’s the owner’s choice between a single engine or twin engines.

Schulz says he wanted to design a fuel-efficient, shallow-draft boat to escape the crowds at popular cruising spots. In destinations such as the Bahamas, he says, the longer range helps him reach more remote shallow-water locales.

“I’ve driven the boat up on the beach half a dozen times,” says Schulz, explaining that the reverse deadrise tucks the propellers and rudders up under the stern. The 38 SRD draws 2 feet, and the hull laminate schedule was specifically engineered for beaching, he says.

A 38 SRD currently under construction at Shannon’s Bristol, R.I., facility uses surface-piercing propeller drives, which Schulz says can reduce fuel consumption by up to 30 percent. Jetdrives aren’t available, he says.

Three different interior layouts are available, and include single or dual cabins with berths for up to seven. There is a galley to starboard and a head with shower (optional separate shower) to port.

Above decks there is a helm seat, a companion seat and an L-shaped bench with a cockpit table. There is a provision in the cockpit for an icemaker, refrigerator and built-in stainless steel barbecue.

The look of the 38 SRD incorporates some traditional elements, including a long cabin top, a series of portholes, interior wood finishing and a barrel-back stern. The integral swim platform in the transom, however, betrays a more modern powerboat. A selection of hardtop, soft top and flybridge models are available.

“We hand-build these boats,” Schulz says “It’s not an assembly-line type of operation — and it never will be.”