THREE WEEKS before the mast.

A group of Boston sailing buffs has chartered a famous Norwegian "tall ship" and is scheduling four three-week trips this summer in which the paying passengers will double as the working crew.

"It isn't a cruise ship," points out spokeswoman Harron Ellenson of Square-Rig International of Boston, a nonprofit organization. "You peel potatoes, you swab decks, you stand watch, you climb the riggings." And for sleeping quarters, you get a bunk and a locker in a below-decks dorm.

The idea is to recreate life aboard one of the very few remaining ocean-going, square-rigged vessels. An experienced, fulltime crew of 17 will be in charge and will offer instruction in sailing. On each trip, there will be space for 70 paying crew members. Passage is open to men and women 16 and over "in very good physical condition." Ellenson sees it as a family or father-son and mother-daughter adventure. A curtain divides the dorm into male-female quarters.

The ship is the 216-foot Sorlandet, built in 1927 in Norway, according to the Norwegian consulate, and used continuously as a training vessel for the Norwegian Merchant Navy until 1939. Sunk in port in a bombing attack during World War II, it was restored after the war as a private school, where over the years 6,000 Norwegian youngsters received their basic sea training. Fully reconditioned in the late 1970s, it is now owned by a Norwegian foundation.

It is the only operational, full-rigged ship available for crew participation by the general public, says Square-Rig International.

The first passage, beginning June 11, will be from Bermuda to Quebec, with a stop in Boston. The second trip will sail from Quebec up the Saint Lawrence Seaway and through the Great Lakes with stops at Chicago, Duluth and Thunder Bay in Canada. Third is a return passage to Quebec, and the fourth has not yet been set but probably will be down the New England coast.

The fee is $70 a day per person, which includes all meals, but transportation to and from ports-of-call is extra. Passage must be booked for the full three weeks.

One thing to remember: If the captain sets you to unfurling the sails overhead, the tallest mast is 115 feet above the water.

For information and an application: Square-Rig International, 19 Milk St., Boston, Mass. 02109.

FIVE STARS: Out of 20,000 dining and lodging establishments in 4,000 communities in the United States and Canada, Mobil Travel Guides has named 12 resorts for its top award of five stars, including two nearby perennial winners, the Homestead in Hot Springs, Va., and the Greenbrier in White Sulphur Springs, W. Va.

To earn the stars, says Mobil, the resorts must score excellent on everything from food and hospitality to recreational facilities and landscaping, which must be "meticulous." At the restaurants, no frozen foods are permitted. And twice-daily maid service is considered "standard."

The other winners: Arizona Biltmore, Phoenix; Boca Raton Hotel and Club, Boca Raton, Fla.; The Breakers, Palm Beach, Fla.; The Broadmoor, Colorado Springs, Colo.; C Lazy U Ranch, Granby, Colo.; Cloister, Sea Island, Ga.; Marriott's Camelback Inn, Scottsdale, Ariz.; The Pointe, Phoenix; Tall Timber, Durango, Colo.; and The Wigwam, Litchfield Park, Ariz.

The Williamsburg Inn in Williamsburg was one of eight hotels rating five stars. The others: Carlyle, New York; Fairmont, Dallas; Four Seasons Clift, San Francisco; Hurrah's, Stateline, Nev.; L'Ermitage, Beverly Hills; Quail Lodge, Carmel, Calif.; and Stanford Court, San Francisco.

MARYLAND BY MOTORCOACH: A weekend bus tour through Southern Maryland is the inaugural travel offering of the newly revised Maryland Magazine, a state publication that anticipates an annual series of excursions to scenic and historic sites within Maryland's borders.

The spring outing is April 9-10, with Saturday featuring a visit to Mary Surratt Tavern in Clinton (she was hanged as a conspirator in the escape of John Wilkes Booth, who shot Lincoln); a stop at St. Clements Island, where Maryland's first colonists on the Ark and Dove dropped anchor in 1634; and a candlelight dinner of Southern Maryland cooking at at the 18th-century Sotterly Plantation on the Patuxent River.

Sunday's itinerary begins with a visit to St. Mary's City, the state's colonial capital, and continues on to Solomons Island, home of the Chesapeake Bay watermen, for lunch at a waterfront restaurant. The day concludes with High Tea at Penwick House, a country inn in Dunkirk.

Buses depart the Hilton Hotel and Baltimore (8 a.m.) and the Sheraton Inn in Lanham (9 a.m.) on April 9, returning late afternoon the next day. Overnight accommodations are at the Belevedere Motor Inn in Lexington Park. The fee is $165 per person (double occupancy) and includes bus, hotel and four meals. The trip is co-sponsored by the AAA-Automobile Club of Maryland.

Establishing a tour series, says new associate publisher D. Patrick Hornberger, seemed a natural use of Maryland Magazine's resources. Coming up in the fall is Western Maryland and plans for four trips in 1984.

For more information or reservations: Maryland Magazine Southern Maryland Tour, 2525 Riva Rd., Annapolis, Md. 21401 (301) 269-3507.

SILVER CREEK: More slopes for ski fans. Construction is scheduled to begin this spring on another downhill skiing and year-around recreational resort in the Middle Atlantic. The new place is called Silver Creek and is located about a mile and a half from West Virginia's Snowshoe Mountain, itself a major ski area about a 230-mile drive from Washington.

Initial plans call for a triple high-speed chairlift servicing six to eight slopes on a mountain that rises to 4,800 feet. The 10-year development plan calls for at least 24 slopes. A 320-unit condominium and conference complex, with indoor/outdoor pool, is expected to be completed for an opening in December.

BALLOONING BICENTENNIAL: France is celebrating the 200th anniversary of balloon ascension this year, and these days travelers can find balloon adventures on practically every continent--from a "zebra safari" above a wild game reserve in Kenya to wind-borne floats across the Australian Outback.

The Bombard Society, a balloon-tour company in McLean, is offering a unique, if expensive, way to participate in the French fe te this summer: a week-long combination balloon and canal barge tour of the Burgundy wine country.

Cruise the Burgandy countryside between Montbard and Pouilly en Auxois on the 24-passenger barge L'Escargot, which serves as your hotel and restaurant, and then soar overhead on daily balloon flights to accent the sightseeing.

Bombard, which has a fleet of 19 brightly colored balloons, has been leading balloon tours to France for seven years. In most cases, the firm points out, balloons float at tree-top level at a pace only slightly faster than a walk. The cost for a seven-day, six-night package, not including airfare, is $3,550 per person, with departures on Wednesdays in July and August.

For more information: The Bombard Society, 6727 Curran St., McLean, Va. 2210l or 448-9407.