Amphibious bus to circumnavigate

From Ocean Navigator #139
July/August 2004
Intrepid sailors have put to sea in all manner of unlikely craft over the centuries: catamarans built of beer kegs; reed boats, a la Thor Heyerdahl’s Kon-Tiki; miniature sailboats that resemble trash barrels; or makeshift rafts constructed of beach refuse lashed together. And now we have the amphibious school bus, which, when completed some time next year, will have a range of 2,000 miles and will be designed to handle the roughest conditions on land or sea.

Mark Roehrig is converting his 1985 diesel-powered school bus into an amphibious voyaging boat.
   Image Credit: Courtesy Mark Roehrig

Mark Roehrig, a fast-combat-ship U.S. Navy veteran whose past accomplishments have also included converting a Geo Metro into an amphibious vehicle and outfitting numerous yachts for offshore work, is retrofitting his 1985 Thomas International diesel-powered bus at his shop in Louisville, Ky. He will be ready for his adventure to drive and sail around the world in 2005, he said.

The bus was purchased for $1,800. Wheelsea, as it is now called, will cost an estimated $35,000 to assemble, Roehrig explained. He is doing the work himself, since he discovered that paying for such a job, or buying an existing trawler, would cost in excess of $300,000 – and wouldn’t be half as much fun.

Why a school bus? First, there is the voluminous interior space, Roehrig said: 290 square feet, plus another 144 square feet of open aft deck, which is vastly larger than even a moderately sized trawler or sailboat.

Roehrig said that the key to his design is the addition of significant ballast tanks, which will stabilize the vessel in a seaway, lowering it into the water like a laden oil tanker.

“There are six displacement tanks mounted below the waterline; each tank holds 200 gallons of water when full,” he said. The advantage of variable displacement is twofold: adding water in rough seas eliminates buoyancy and allows for additional ballast weight, should the vessel ever capsize. On the other hand, adding air increases buoyancy and allows the hull to rise out of the water (during fine conditions) for far less drag, increasing fuel performance, range and speed.”

Image Credit: Courtesy Mark Roehrig

Mark Roehrig plans to circumnavigate the world by way of the Atlantic Ocean, overland across Africa and Asia, back to North America.

Wheelsea is powered by the bus’ original International 6.9 diesel, which is installed below the vessel’s waterline and will draw fuel from a 500-gallon tank. The vessel will have no propeller shaft or axle through-hull fittings. Instead, it will be hydraulically powered, the only through-hulls being the connections to the hydraulic hoses.

The vessel will be double-hulled: The interior of the bus, reinforced with an exterior, ship-like steel frame, will sit inside a 1/8-inch-thick steel hull. It will be 53 feet long, have an 8-foot beam, and weigh approximately 28,000 lbs.

Roehrig is looking for a shipmate or two for various legs of the circumnavigation, which he expects will last seven years; visit for more information on Roehrig and his nascent adventure.

By Ocean Navigator