It took a combination of youthful daring and mature sensibility to create "The Sailing Chef," a book so good that it should become a waterborne "Joy of Cooking" for those who make meals afloat.

Safety, planning and the innovative use of fresh foods are cornerstones to the design 26-year-old Ty Harrington draws in a thin volume studded with useful drawings and appealing photographs. (It's been published by Walker and Company for $9.95.)

Most previous cookbooks for sailors have fallen somewhere between picnic and camping guides. They offer a smattering of sea lore to spice up recipes that are heavy on convenience foods or are to be cooked ashore before the voyage begins. Harrington has taken a different tack. He sails around the floating picnic by assuming the reader not only has to cook on board but wants to do so.

"The Sailing Chef" is divided into two sections. The first, and probably the most valuable, is a handbook that deals with galley design and equipment, provisioning and the role and duties of the cook. There's some repetition as it unfolds. It should be taken as a sign of earnestness.

If there is an overall theme to his advice, it is to warn those who cook on boats to expect the unexpected. Even at anchor, the wake of a passing boat can launch food or cooking equipment into motion. "It does happen," Harrington said during an interview last week. "And it only has to happen once to leave everyone hungry or cause an accident. You have to get in the habit of being careful. If not, you won't be protected when you need it. You can't conceive of some of the things that can happen. You have to have been a cook to think about it."

His model cook wears gloves, an apron and shoes at the range, has safety straps nearby, works from a carefully organized ice box and storage containers and never leaves knives or utensils unsecured. He sees potential danger everywhere and won't light a burner unless there is a pot on it or risk having a paper wrapper clog the bilge drain.

Not that gloomy forboding is the book's sole theme. Harrington would have the cook experiment with a wok, never spend more than an hour at a time in the galley, call on others to help out if they are willing and invent ways to keep sea gulls away from the food on an on-deck hibachi. Cooking afloat, he points out, isn't like cooking on a camping trip. The heavy pot is practical on a boat; the low-lipped, light frying pan is not.

Nor, he argues, should the sailor's diet be taken for granted. "Campers and hikers tend to be concerned (about what they eat)." Harrington said. "But sailors carry their eating habits on board without thinking. It's crazy." He feels adjustments must be made to compensate for dehydration, added expenditure of energy and weather. "The rougher the weather, the more smoothly a galley must function," he warns.

"The essence of successful cooking at sea is simplicity," he writes in the book. "Use the absolute minimum necessary to produce maximum results. Each item must be selected for a good reason. Every utensil, every pot and every pan must serve more than one purpose or it wastes space . . . All food should be filled to the brim with food value. There is absolutely no room for empty calories. This does not mean that meals need be spartan, nor the cook a wizard. It does, however, require extra planning and careful attention to details that could safely pass unheeded ashore."

His own shipboard cooking career commenced a few years ago in anything but an orderly fashion. Struck by the beauty of the majestic sailing schooner the Bill of Rights anchored off Block Island, he swam out from shore and sought an interview with the captain to volunteer his services as cook.

A native of manhattan, he had come to Block Island for a vacation after combining China studies and American history upstate at Union College (Dorm cooking, he believes, gave him valuable experience in storing and cooking food in small spaces and it shopping with economy in mind.) He stayed to become a dishwasher in a restaurant that served 600 meals a night, thereafter an apprentice cook.

"On the Bill of Rights I had to be a seat-of-the-pants cook, a test pilot," Harrington explained. Meals for 40 were improvised in emergency situations, recipes grew from mistakes. "But I had learned how to do prep work in a large professional kitchen and that is something even the weekend sailor can benefit from. It you don't prepare correctly, it won't come out on a boat, no matter how good a cook you are. There will be missing ingredients or the timing will be wrong."

Harrington argues that "a cook has a head start on the water," and needn't aim at the lowest common demoninator of taste. Hard work and salt air stimulate appetites, and meals become a form of entertainment. The recipes he has devised and collected reflect his view that fresh foods are more versatile, nutritious and economical than prepared foods and his own success in winning over "meat and potatoes" sailors to zucchini and chef's salad.

Lately the chef hasn't been cooking very much. After learning something of the writer's craft and the art of photography at the National Geographic, he undertook an 18-month project to write and do the illustrations for a book about the National Cathedral as seen through the eyes of the craftsmen who created it. Prentice-Hall is the publisher.

"It became a course in Gothic architecture," Harrington said last week. "It was a big switch from cooking, but I've kept my hand in by doing a monthly recipe column for the National Pleasure Boat Owners Association." Now, with work on the book nearly done he's planning a return visit to Block Island. This time he'll go sailing on Buzzard's Bay instead of washing dishes.

Here are several recipes from the book. RARERAREBIT (Makes 4 servings) 2 tablespoons butter 2 eggs 1 cup baked beans, mashed 1 cup grated Cheddar cheese 1 1/2 cups milk 1 teaspoon prepared mustard 1/2 cup bacon bits (precooked ashore) 8 slices of whole-wheat toast

Heat butter in a skillet. Break eggs into hot butter. Immediately stir in baked beans. Add cheese, milk mustard and bacon bits, stirring to blend. Cook until creamy. Spoon on top of toast.

Cooking and preparation time: 25 minutes. THICK AS A FOG PEA SOUP (Makes 10 servings) 1 pound split peas (unless instant variety, must be presoaked) 4 quarts beef broth (made from bouillon cubes) 3 potatoes, peeled and diced 1/2 head of cabbage, shredded 3 cups diced ham 1/4 cup dry red wine 1/4 cup dry vermouth 2 tablespoons dry mustard 1 teaspoon black pepper Salt

Combine all ingredients except salt in a pressure cooker over low heat for 45 minutes. Add salt to taste. Serve with chunks of thick bread.

Cooking and preparation time: 55 minutes. SAVORY ZUCCHINI (Makes 4 servings) 3 large zucchini, sliced thin 1/2 cup vinegar 3 tablespoons butter Salt 1/2 cup thin slices of Cheddar cheese or grated Parmesan

Combine zucchini, vinegar and butter in a large skillet. Cover and simmer for 10 minutes. Add salt to taste. Sprinkle with cheese, cover and cook until cheese is melted. Serve as is, over whole-grain bread, or as a side dish.

Cooking and preparation time: 20 minutes. LENTIL BURGERS (Makes 4 servings) 1 large onion, cut up 2 tablespoons butter 2 garlic cloves, minced Salt and pepper 4 cups cooked lentils (from 2 cups dry lentils) 1 cup chopped mushrooms 1 tablespoon safflower oil

Saute onion in butter with garlic and seasoning to taste. Combine lentils, mushrooms and sauteed onion and mash into a paste. Form paste into patties. Heat oil in a skillet and saute burgers, browning both sides. Serve between slices of bread; rye is best.

Cooking and preparation time: 20 minutes. BUZZARDS BAY BLUEBERRIES (Makes 4 servings) 1 pint blueberries, washed and stemmed 1 tablespoon sugar 1/4 cup chopped cashews or walnuts 1 banana, mashed 3/4 cup heavy cream or milk

Mix sugar and nuts with mashed banana. Spoon over blueberries. Top with 2 tablespoons cream per serving, or use milk.

Preparation time: 5 minutes.