Kennecott Copper Corp. and Curtiss-Wright Corp. have reached a compromise, ending - at least for the time being - one of the most bitter and hard-fought corporate takeover fights in history.

The settlement calls for an end to the prolonged legal volleying between the two firms, and will result in a reconstituted Kennecott Board of Directors that will now include several Curtiss-Wright executives.

Curtiss-Wright will be allowed to increase its holdings of Kennecott stock until it control 21 percent of the company's shares. Curtiss-Wright presently owns 9.9 percent of Kennecott, making it the largest single stockholder.

Under the agreement, the 18-member Kennecott board will now include seven new directors, including Curtiss-Wright chairman T. Roland Berner and two other candidates originally listed on a slate proposed by Curtiss-Wright at a dramatic annual meeting last May.

Kennecott also said it plans, subject to the approval of its stockholders, to reimburse Curtiss-Wright for as much as $1.8 million in out-of-pocket expenses spent in a proxy fight at that annual meeting.

At the meeting, Kennecott won a proxy fight only to have that verdict overturned in federal court on procedural grounds, and a new vote ordered for next month.

The new board will stand for re-election at the next regular Kennecott stockholders meeting in May. Meanwhile, Kennecott agreed to look into a Curtiss-Wright proposal that the nation's largest copper producer divest itself on its Carborundum subsidiary.

Both firms also acknowledged that the agreement reached yesterday expires immediately prior to the 1981 Kennecott annual stockholders meeting. "I have no idea why," said a Kennecott spokesman about the expiration date. Presumably, at the time Curtiss-Wright could resume its takeover attempt.

As of now, however, yesterday's agreement ends a year-long attempt by Curtiss-Wright, a New Jersey based aerospace conglomerate, to take control of Kennecott.

For the post several days, Curtiss-Wright chairman T. Roland Berner and Kennecott chairman Thomas D. Barrow have been negotiating the deal finally struck yesterday.

A Curtiss-Wright spokesman said he couldn't describe the deal "in any way as a victory, defeat or whatever." Curtiss-Wright had been critical of Kennecott management, and had long proposed the sale of the Carborundum subsidiary.