preform 12 is not yet in place which allows access to the void space 32 inside the preforms to add the chopped fibers after the hub assembly as described above is placed in the mold base 112 chopped carbon fibers are added the amount of chopped fibers depends on the desired percentage of fiber to the overall weight of the finished rotor in the preferred embodiment fiber from both the fabric preforms and the chopped fibers makes up about 60 of the weight of the rotor the chopped fibers are added to the birds nest mold taking care to distribute them around and under the cell hole mandrels 122 after most of the chopped fibers have been added the upper half of the mold midsection 114 and top 116 is lowered to the base 112 thereby compressing the chopped fibers the midsection 114 is then bolted to the base 112 and the top 116 is raised to provide access to the middle of the mold cavity the remainder of the chopped fibers are then added and the mold is again closed the mold is then heated to about 240 u00b0 f for about one hour to cure the birds nest assembly the resin already present in the preforms helps to bind the preforms and chopped fibers together into a porous structure the birds nest optionally additional powdered epoxy resin may be added along with the chopped fiber to provide more binder material for the birds nest preferably the resin is less than 45 of the weight of the chopped fibers the process of making the birds nest described above does not include the step of placing the bottom fabric preform 12 in the birds.