Like a friendly dinosaur, the great white skeleton rears into the sky on a marvelous swooping curve. Just below the peak a man tickles the wooden frame with a paint roller on a six-foot handle. He is nine stories high, and he looks pretty small up there.

They are putting together the new roller coaster at Wild World. It doesn't open until May 3, and they have already sold 5,000 tickets.

The place is quiet today. The parking lots are empty. The rides and walkways and the 14 restaurants where 10,000 people might bustle and shout on a good summer's day stand vacant. Dead leaves gather in the corners of the Wild Wave tank, where for 115 days of the year kids jump and shriek in a million gallons of water. On a plastic beach, umbrella skeletons and folded beach chairs wait for the overhead sun. Through the window of a shed stares the large merry painted eye of a carousel horse.

The only action here at Largo is around the roller coaster, nearly complete now. In its former life as the Giant at Paragon Park in Nantasket Beach, Mass., it was rated the sixth-best coaster in the country, rising with excruciating slowness to 98 feet, then dropping like a stone in five seconds, twisting and banking and lifting its riders clean out of their seats for a few hysterical moments along a 3,400-foot route that took it doubling back through its own framework.

The ride took 2 1/2 minutes, which is half of forever in roller-coaster time.

Now, as the Wild One, it will go 4,000 feet, for the new owners have added a huge horizontal loop at the end called the Helix in hopes of making it No. 1. Just when you thought the agony was over, this invention spins you 540 degrees at 55 miles an hour, a full circle and a half, before it lets you go tottering off in search of a cot.

We are standing around in the muddy meadow with Lyle Wolinsky, Wild World's marketing director, who wears a city suit, a city coat and engineer boots. "With a steel coaster you can have a vertical loop," he says. "But this is wood, so we go horizontal."

He is not saying it will be any less scary. Anyone who has been on a wooden roller coaster knows how it creaks and sways and makes you believe for sure you are taking the last ride it will ever give. There used to be one outside San Diego that had a big "Condemned" sign on it for a gag.

Now we are standing around with Charles Dinn, who has spent the last 20 years or so designing wooden roller coasters, including the 7,000-foot Beast at King's Island, Ohio. "The rhythm is important," he says. "You can get bored on a ride, so you vary the action, make it interesting. You put in turns and drops and bumps, take 'em sideways . . ."

Doing our best to picture the kind of person who would get bored on a roller coaster, we watch workmen paint slats on the ground before they are hoisted up into the framework. When Wild World bought the Giant for $28,000 last year, it was dismantled and brought here on 12 trucks. The Helix, based on an addition built after a fire in 1962, had to be designed from scratch, since the original blueprints were lost. Dinn worked it out from an old post card.

One great feature of the Wild One, remarks General Manager Mark Mason, is that the speed bumps give you a weightless feeling. "It lifts you up," he says. "Makes you fly." To make sure you don't really fly, the thing has seat belts. Mason also has a good word for the old wood in the frame, Douglas fir heartwood as sound as the day it was cut, he says. The addition is of specially treated yellow pine.

It will be finished in about 45 days, the men estimate, leaving plenty of time for tuneups. One reason why Wild World preferred to spend $1 million renovating an 80-year-old coaster rather than build a new one is that it takes three to five years to work out the bugs. Fifteen million people, including generations of Kennedys, Ted Williams and Cardinal Cushing of Boston, have put their imprimatur on this one.

"It looks bigger out here with all this open space," Mason observes. "It didn't look half as big in Massachusetts."

He is right. It dominates the winter landscape, rearing far above the smoky gray woods, stretching clear beyond the other rides on this 500-acre site. Something about those crisp white lines, the gliding curves, that fantastic pathway to the blue, makes you smile and smile.