THINGS PEOPLE DO : ‘Sidewalk Surfing’ on Crest of Another Boom Despite Problems : Skateboarding: Skate parks have come and gone, but with a rise in popularity, there is a new demand for facilities. Insurance costs and liability concerns stand in the way.

Mike Ryan of Loma Portal remembers stealing his little sister’s metal roller-skates when he was a boy, nailing them onto the bottom of a two-by-four, then attaching a soap box to the top of what is now considered a first-generation skateboard.

He used to deliver newspapers with the contraption, but he soon discovered that without the soap box, the thing made a pretty fun toy. And, hey, sidewalks seemed to be designed especially for it.

“It was just the thrill of going down the sidewalk and hearing the clickety-clacks of the wheels hitting the cracks getting closer and closer together,” Ryan remembered. “And then it was a matter of where I was going to bail, where was the nearest lawn I could jump onto.”

Yep, Ryan considered himself something of a daredevil, but now he wouldn’t even contemplate the things skateboarders do, such as hurling themselves 20 feet into the air, coming down safely on a wooden ramp, then soaring off the other side of the ramp.

What the Beachboys once referred to as “sidewalk surfing” has, like rock music itself, evolved.

You don’t hear many do-wahs in rock & roll these days and you don’t see many people riding a plank with metal wheels down the sidewalk. Bands have become as nasty as they wanna be, and skateboarders have become as gnarly as they wanna be.

Not only has the sport changed radically, it also has flourished. According to the latest numbers compiled by the National Skateboard Assn., there are 10 million skateboarders in the United States (no local figures were available).

But there’s a problem: No place to skate.

“The older generation gets into biking,” said Dennis Bullock, 20, manager of Just Skate, Ryan’s store that caters to skateboarders. “So they’ve had bike paths built all over. But kids have been skating for over 30 years, and skateparks have come and gone.

“Now, there’s nowhere to go.”

It hasn’t always been that way. In the late 1970s, skateboard parks abounded, but soon enough, they suffered a rash of liability lawsuits that resulted in skyrocketing insurance premiums. Eventually, most just shut down.

“If it were up to me,” said Calixto Hernandez, 19, of Ocean Beach, “I’d rather skate on ramps, rather than get into the street scene where there’s so many bad vibes and irate business owners. But because there are no parks, I’ve been forced to skate anywhere I can find.”

Two skateboard parks have opened locally in the past two years, providing an alternative to illegally skating on streets and public property--but only to those who have transportation to get to them. One is in Carlsbad, the other in Linda Vista.

The Linda Vista Boys’ Club Skatepark is associated with the Boy Scouts and thus gets around the liability problem by using the scouts’ insurance. Mike McGill’s Skatepark in Carlsbad has its own policy, but McGill, 24, a professional skateboarder, said because of the high cost, he rarely turns a profit.

Ryan, 40, says the insurance companies’ worries are unfounded. Ryan, who hopes to operate a park at Robb Field to alleviate skateboard congestion on Ocean Beach sidewalks, has compiled data from around the country.

Among his findings:

--Today’s skateparks do not provide the hard, concrete ditches that were a mainstay in the 1970s. Instead, they consist of wooden ramps on which skateboarders have learned to fall without seriously injuring themselves.

--The city of Santa Cruz has operated a public skateboard play area since 1978 and has had only two lawsuits, one of which resulted in a small, out-of-court settlement.

--The city of Virginia Beach has operated three skateboard ramps since 1984 and entertained 18,130 users in its first three years. In that time, there were 36 minor injuries and 15 fractures. There were no insurance claims.

--An Ocean City, Md., skateboard ramp has been in use for 10 years and has had no insurance claims.

--In 1985, the National Safety Council found that there were 581,784 injuries related to cycling, 395,000 injuries related to baseball and 37,326 injuries related to skateboarding.

Besides the Robb Field site, Ryan would like to see one skateboard park in each city council district, arguing they would get kids off the streets and may even provide an alternative to drug use.

He’s not alone in advancing that theory. George Loveland, head of the San Diego Parks and Recreation Department, agreed--to a degree.

“Mr. Ryan is touting (skateboard parks) as an answer to the problems kids are having on the streets and with drugs these days,” Loveland said. “And it would be, but there would have to be an awful lot of these things to make a dent.”

Because of city budget cuts, a skateboard park in each district appears to be out of the question, Ryan admitted.

But even if Ryan were able to get a couple parks built, there will always be a few skateboarders who prefer the street scene, kids who find it part of the fun to seek out new parking lots, malls, school yards or drained swimming pools.

“It’s a lot of fun to go out and find a new place,” said San Diego’s Robert Wages, 16. “It’s like an adventure.”

Some older skateboarders go as far as chartering private planes to fly around the county in search of empty swimming pools, according to several skaters.

But the main thrust in the sport is vertical skating, using plywood ramps pushed together end-to-end to form what skaters call a half-pipe .

A standard half-pipe has banks 11 feet high, the top 18 inches of which is completely vertical. It stretches 34 feet long (16 feet of which is flat) and is 20 feet wide.

Good skateboarders make it appear as though gravity does all the work. They simply slide down one end of the half-pipe and use the resulting momentum to scale the other end. On average, they get themselves and their boards five feet above the ramp’s edge (some go more than 10 feet above) before turning around and heading back down . . . and back up the other side.

In truth it takes a lot of physical exertion to shift one’s weight around and maintain balance. It’s so strenuous, most skateboarders can only go back and forth a few times before running short of breath. But in a couple minutes, they’re right back at it.

“You just keep doing it even if you get tired just because it’s so much fun,” said Jimmy Brandenburg, 15, of Santee.

“It’s a rush,” said Matt Carruthers, 20, of Ocean Beach. “You go fast and do your own thing. It lets out a lot of aggression. It’s like being on a roller-coaster, but you’re driving.”

Added Jerry Warila, 15, of University City, “It’s like a sober high. When you’re five feet above the ramp and looking down, it feels great.”