Small sailing catamarans have held a fascination for people who fiddle around with boats ever since they appeared on the scene 15 years ago.

The little boats are everywhere these days - on the Potomac, on the Chesapeake and in all the protected bays behind the sea-shore. What turns boatmen on about Hobies, Prindles, Nacras and other tiny twin-hull vessels is their astounding speed.

With the proper wind and on the proper point of sail, a catamaran can swoosh through the water at 15 knots, leaving a wake like boiling tea.

If a two-person crew is on board, one and maybe even both will be hiked out on a trapeze, high on the windward side, balancing perilously over a roaring sea. When it goes right, cat sailors are heard across the water, whooping and howling with glee.

That's the compelling allure of the cat. Unfortunately, it's about the only allure.

This was to be exaltation of cats. On the surface they looked so right.

Look at the apparent advantages:

The little boats are light. They weigh perhaps 300 pounds fully rigged, which would indicate a capacity to fly along on even the lightest breezes, the kind that plague the Potamac and Chesapeake all summer long.

Not so. They won't go in light air.

They look maneuverable, the kind of boat one could said for an hour, then pop up to a dock for a bit of exploring in town.

Not so. They are skittish and tricky to handle in close quarters.

They look comfortable, with their bouncy trampoline-like deck ssprung between steel frames. When the wind subsided one would envision rolling over and catching some sleep until the breezes blew again.

Not so. The sea slops through the trampoline and the boat pitches like a cork.

These are the negatives. The positive is that catamarans, sailed in an honest 20-knot blow, are every bit as exciting as they look, easy to sail and surprisingly stable.

On a recent afternoon-long sail on the Chesapeake I had a chance to see the best and the worst of cat life.

The boat was a Prindle 16-footer, handsomely appointed with all the latest go-fast, super-lightweight equipment. It belonged to Chesapeake Catamarans, which rents them for $15 an hour at its base on the east end of the Bay Bridge.

"The marina operators around here call our fleet the Kent Island Air Force," said Skip Ronsaville, co-owner of the company.

But you need air to fly. Lots of it.

We spent four hours searching it out until a spectacular half-hour gust blew up from the south and gave us the standard catamaran blastoff.

In those four hours I discovered what a long and frustrating day cat sailing can become when the conditions are only average. The boat , being light, lacks momentum, so a small whisper of wind can get you moving, but each flat spot stops you cold.

And the boats simply don't point into the wind. A good monohull racer will point within about 30 degrees of the wind direction and go. Because of the catamaran's wide configuration on the waterline, it is lucky to get within 50 degrees of the wind.

That means that if the breeze is coming from Point A and you have to get to Point A, it could mean spending all day tacking.

Which is where we ended on our Prindle until the great gust arose and we set the little cat on one hull and screeched across the Bay, leaving the Wednesday night racers out of Annapolis cursing in our wake.

Brian Biland, Ronsaville's partner, conceded the cat's weakness. "I don't even sail them myself unless there's a gale," he said.

George Stevens, who runs the boat rentals at Belle Haven Marina in Alexandria, rents Hobies for $16 for two hours on weekends or $14 for two hours on weekdays.

"You got here a day too late," he said on Sunday. "Yesterday was Hobie day."

Mild Sunday wasn't a Hobie day. There was no wind until a horrendous electrical storm blew up, and that didn't make it a Hobie day either. "You'd electrocute yourself sitting on that steel frame," he said.

So he pushed his real fleet - a dozen Flying Scots, plain old traditional monohulls.

"Once you've learned to sail one of them you can sail anything there is," he said.

That may be the final disadvantage of catamarans, which stand in this boatman's eyes as wonderful gimmicks for conditions that exist only rarely in our area.

They're great for a windy beach in Hawaii, but who has access to that?

And once you've learned to sail one, you haven't really learned to sail. You've just learned how to cat around. CAPTION: Picture, GIVEN ENOUGH WIND, A "CAT" WILL SCAT. By Angus Phillips.