VIDEO: Market sees surge in stepped-hull designs


A growing number of boatbuilders are inserting the stepped-hull design into their vessels, hoping to offer boats with greater speed and efficiency — a trend to watch in the industry and one you’ll see at the Fort Lauderdale International Boat Show.

Invincible, Contender, Regal, Beneteau Powerboats, Scout, Intrepid, Cutwater and SeaHunter use steps in one form or another.

With the technology comes some marketing hyperbole, however, said Ocean5 Naval Architects CEO Robert Kaidy. “The idea that the hull is operating a gigantic bubble and is supported by compressed air can only be described as complete baloney,” he said during a presentation in September at the International BoatBuilders’ Exhibition & Conference in Louisville, Ky. “The whole idea of a stepped hull having ‘air bearings’ or ‘air lubrications’ is unsupported.”

Click play for a look at some models.

Some stepped hulls lack the proper engineering and naval architecture, Kaidy said. “The reality is the market is filled with a lot of stepped-hull boats that don't actually work,” he said in a follow-up phone interview. “Stepped hulls when applied properly are effective, however.”

How? “They lock the boat, regardless of speed, into its optimal running trim angle,” said Kaidy, whose company is working on seven stepped hulls. “Every planing hull has an optimal trim angle that is typically between 3.5 and 4.2 degrees. That is where the lift is greatest and the drag is lowest. It’s called the drag bucket.”

Kaidy’s Ocean5 developed an analytical tool to determine this optimal trim angle. Its Virtual Seatrial computer software analyzes hull designs through a “digital sea trial.”

Kaidy predicts that during the next few years a “whole new stable of boats with stepped hulls will come to the market.”

I know that SeaVee is coming at us with several of them. The builder’s Facebook site says: “SeaVee announces the new Sea Vee Z High Performance model line featuring an innovative stepped hull design that will recalibrate the industry standard for performance, efficiency and handling. The new Z line will be unveiled on Oct. 31 at the Fort Lauderdale Boat Show, Booth No. 2023.”

I plan to put together an article about this design technique’s rise in popularity; its pros and cons; the characteristics of an effective — and ineffective — stepped hull; and the types of boats that benefit most from it.

— Chris Landry


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