Bill Rockford, a Baltimore city official, couldn't stop shaking his head. "I look at it and I keep wondering, 'Where's the other half?'"

Rockford was studying Yankee Girl, the boat in which Gerry Spiess sailed 3,800 miles from Norfolk to Falmouth, England; the same boat in which Spiess intends to sail from California to Australia this summer.

It is 10 feet long.

Ten feet. Right. Three giant steps. Smaller, end-to-end, than grandma's Toyota. The smallest boat ever to cross the Atlantic, east to west. For deck space to walk on there is exactly zero. It is a plywood womb, a time machine Spiess can zip around himself and bob in like a cork to new continents.

And feel safe? Not really.

"You can prepare yourself for loneliness," said Spiess. "You can prepare for hardship. But the one thing you really can't prepare for is fear. I was under tension, I guess you could say afraid, for the entire trip."

That was 54 days at sea, the first two weeks being the most treacherous. It blew hard for a week after Spiess left Norfolk on June 1, 1979. Then it got worse. He was hove-to with only a storm jib flying for the first three days of the second week. Then it grew worse still, and he rocked and pitched for four days in 40-knot winds, hundreds of miles offshore in a 10-foot boat with no canvas flying at all.

The seas were 15 feet, towering over the little boat and cresting almost higher than the masthead, which is 17 feet from the waterline.

Yankee Girl stood up. "That's what she was built for," said Spiess.

He should know. He built her, from his own design. And that's really why he's going back out again. It wasn't fun the first time; now he's planning an infinitely more difficult trip across the Pacific, one he expects to take five months to complete. Why?

"That's a good question," said the 41-year-old Spiess, who graduated Phi Beta Kappa in psychology from the University of Minnesota and holds a graduate degree in education.

"The boat really doesn't have any life unless it's doing what it's designed for. I'm doing it more for the boat than for myself. I'm still in love with the boat. It needs a chance to perform. If you designed a car and it drove beautifully, would you leave it in the garage?"

Spiess is no quick study. Most serious sailors are complicated people. His story is enlivened by the strange circumstance of his origins -- he comes from the inland flats of White Bear Lake, Minn. He learned to sail by reading books. He has been married, happily, for 20 years.

He was plugging along merrily toward a career in administration with Gillette when he was bitten by the long-distance sailing bug in the late 1960s. One day he quit his job, hurried home, scrubbed the garage floor and began laying out pieces for his first home-made boat, a 17-footer. He planned to sail it around the world.

He launched that boat in November 1969, in the Mississippi River and broke ice for the first leg south. Four thousand miles and 18 months later he had crossed the Gulf of Mexico and Panama Canal and was lonely in Ecuador. He called Sally, his wife. She joined him briefly, but then they sold the boat and abandoned the voyage.

Spiess came back and worked for two years driving a concrete truck. Before long he was building boat No. 2, a 15-foot trimaran, with the idea of sailing that around the world.

That trip fared less well. He started from Miami and by the time he had the Bahamas in sight he found himself hallucinating, not eating or sleeping, completely unprepared psychologically. He turned the boat around, sailed back to Miami and sold it. He was home less than a week after he started.

"I told myself, 'That's it. No more sailing. I'm not cut out for it,'" said Spiess. It didn't last.

He grew intrigued with new questions. How small a boat could actually make an ocean voyage? He formulated a theory of "impinging parameters -- the smaller the boat, the slower it goes, the longer the trip, the more supplies you need." He wondered where the impinging parameters converged on the smallest boat that could carry enough to make a successful ocean crossing.

He picked the Atlantic crossing because it is the longest distance a boat would have to go between stops to get around the world. And, from his mental meanderings, Yankee Girl was born.

Her arrival in England was a triumph he never will forget.

"It had been raining for weeks but the clouds broke and it was a beautiful, sunny day. It was the height of tourist season in a resort town. My wife and parents came out to meet me in the pilot boat. The BBC and CBS and NBC were there. There were airplanes and helicopters, hundreds of boats, 10- or 20,000 people watching from the roads and the hills in town, boat whistles, horns. It was overwhelming; just like you'd staged the thing."

A great successful adventure.

"Adventure? I don't think of myself as an adventurer," said Spiess, who looks like an accountant who exercises rather than an oceangoing singlehanded sailor. "I like to think of these things more as projects, as personal challenges. Adventures to me are more often misadventures. The achievement, I think, is the guy who can come in and say, 'No problems. I had enough water, enough food.'

"After all, humans' strong point isn't going without food or clothes. It's being smart. . ."

Spiess and his 10-foot oceangoing yacht are among 400 boats on display in the Chesapeake Bay Boat Show at Baltimore Convention Center this week. Boat show hours are noon-9 p.m. weekdays, noon-10 Saturday and noon-8 Sunday, closing day. Admission is $4 for adults, $2 for children.