An article (10) such as a grid fin that controls the direction of flight of a vehicle, has precisely formed passages (14) with porous locating walls (52A, 52B) and a layer of fibrous material (86) such as graphite cloth lying against one or both opposite sides of the locating wall, and with the locating wall and fibrous material impregnated with resin (84). Locating blocks (30) of foam are molded and the fibrous material (42) is wrapped around each block. The wrapped blocks (44) are each inserted into a passage (54) of a locating grid (50), so the fibrous material is compressed. The locating grid lies in a grid-holding mold (60). With the fiber-wrapped blocks inserted, the grid-holding mold is closed and resin is injected into the mold and allowed to harden. The foam blocks are removed by eroding them, as by sand blasting them, to leave a final article.