Burt Rutan is up to something. He isn’t saying much about it, but whatever it is, you know it’s interesting.

There’s been plenty of speculation within the aviation world about whether Rutan would stop designing airplanes now that he’s retired from Scaled Composites. Imaginative and prolific, Rutan has been at the leading edge of aerospace design since the 1970s, and few thought he would simply play golf all the time. True to form, Rutan is working on a new aircraft design.

Rutan is famously secretive about designs that have yet to fly, though now that he is “retired” he is letting out a few more details than usual. The engineer told the Experimental Aviation Association he is tinkering with a design influenced to some extent by the lakes and rivers of Idaho, where he now lives after spending more than 40 years in the Mojave Desert. He also mentioned being influenced by the unusual Russian air/watercraft, like the MD-160 Lun-class ekranoplan, he saw shortly after the fall of the Soviet Union.

“It is a combination wing ship and seaplane,” he told the EAA.

What Rutan did say is he hopes to design a very efficient winged boat that could be used on a major body of water like Lake Coeur d’Alene and converted into a seaplane to navigate the small lakes and rivers nearby. There are a few other designs out there that use ground effect to “fly” just above the surface of the water, but no one’s seen anything like the design — known simply as 372-3 — Rutan is hinting at.

Rutan, perhaps anticipating the next question, was quick to tell people not to hold their breath awaiting DIY plans for their own plane. Before gaining worldwide fame for SpaceShipOne and Voyager, the first aircraft to fly non-stop around the world on a single tank of gas, Rutan made his living selling plans for aircraft he designed.

The Rutan faithful have long wished for a new design they could build and fly. But Rutan says he has no timeline for completing this project, and if it doesn’t work out as he hopes it could simply disappear.

Photo of Burt Rutan with SpaceShipOne: Mark Greenberg/Virgin Galactic