Chris Mitchell, 64, said he's been designing a trimaran for years, but was "closing in on it now".

"The America's Cup this year was an extraordinary event, and confirms that a tri is the way to go," he told The Journal from Qingdao, China, last week.

It's not the first time the boat builder has been successful in thinking outside the square.

With a philosophy that sailing should be accessible to everyone, Mr Mitchell built a fast-moving SKUD 18 keel boat, which was selected to race in the 2008 Beijing Paralympic Games. Then in January, Australia's first MkII SKUD 18 won the ISAF Sailing World Cup Sail Melbourne International Regatta.

A team of four employees run the boat business in Dandenong.

Project manager David Staley said the keel was the unsinkable boat's secret.

"They are heavy keels and the boats are designed to be fully accessible for a couple of wheelchair users to go for a squirt up the coast for a weekend."

Mr Staley said the SKUD 18 had two seats and sailors could be seated on the centreline for paralympic events.

"Rachael Cox, who has the use of an arm and leg, and quadriplegic Daniel Fitzgibbon, raced the SKUD 18 and won silver in Beijing.

"Ame Barnbrook, born without arms, with only half a leg and three toes, sails the scud using her toes to steer the joystick. Her crew, vision-impaired Lindsay Mason, controls the sails. They weren't selected in 2008, but are working at representing Australia in 2012."

Mr Mitchell said he didn't specifically set out to focus on designing boats for people with a disability, but his first design was a multipurpose dinghy.

"It progressed to a specialist dinghy built for the Chinese.

"Disability came into the picture after I built a single-seat version of the 2.3-metre-wide seat so someone would be very secure sitting stationary in the centre and water wouldn't come over the side when the boat leaned over.

"When that worked I could see we needed a servo-assisted steering and winch to pull in the sails. I realised then a quadriplegic person could use that boat."