The Cambridge firms of Fuller and Sadao, Inc., Geometrics, Inc. and the Cambridge Seven Associates, Inc. will design the United States Pavilion at the 1967 Montreal World's Fair.

W. Terry Renkine, assistant professor of Architecture and head of Cambridge Seven's part in the exhibit, yesterday said the architects hope to make the exhibit "light and engaging rather than the usual heavy-handed effort."

Cambridge Seven is a virtual manpower center for the School of Design. Five of its members have Harvard appointments and teach there or at the Carpenter Center. The firm has renovated the basement of the Brattle Theatre.

To make the exhibit "light and engaging," the pavilion will> de-emphasize industry. Working with the theme, "Creative America," Renkine said that the exhibits will include temporary art--painting, sculpture, and photography--well as demonstrations of new technology and a multi-been film. Another highlight will be a lunar exhibit, a visualization of the 1970 Apollo flight, to be reached by an 85-foot escalator.

The pavilion was designed by R. Buckminster Fuller '17, who developed the geodesic dome. The main structure of pavilion will be one of these domes, 200 feet high and 250 feet in diameter.

A geodesic dome is a sphere formed by tetrahedrons--pyramids made of equilateral triangles, the simplest possible shape in three dimensions. This gives the largest possible space to the interior dome with a minimum of surface area surrounding it. It makes a lightweight, easily-assembled, low-cost frame.

The bubble will be filled with natural light by day and will glow from internal light by night. The architects regard the structure as a prototype for whole communities living in a "Garden of Eden" environment protected from unfavorable climates.

Construction will begin on the pavilion by the end of this month, and will be completed by April 1967, when the fair opens. A total of $9.3 million has been appropriated by Congress for U.S. participation