3. In bolted installations, use spacers, collars, shoulders, or stop-nuts to prevent tightening the bolt excessively. Whenever such devices are used by the aircraft manufacturer, retain them in the replacement installation. It is important that the original number of bolts, complete with washers, spacers, etc., be used. When rivets are used, provide adequate spacers or other satisfactory means to prevent excessive tightening of the frame to the plastic. 

4. Mount plastic panels between rubber, cork, or other gasket material to make the installation waterproof, to reduce vibration, and to help to distribute compressive stresses on the plastic. 

5. Plastics expand and contract considerably more than the metal channels in which they are mounted. Mount windshield panels to a sufficient depth in the channel to prevent it from falling out when the panel contracts at low temperatures or deforms under load. When the manufacturer’s original design permits, mount panels to a minimum depth of 1 1 ⁄ 8 -inches, and with a clearance of 1 ⁄ 8 -inch between the plastic and bottom of the channel. 

6. In installations involving bolts or rivets, make the holes through the plastic oversize by 1 ⁄ 8 -inch and center so that the plastic does not bind or crack at the edge of the holes. The use of slotted holes is also recommended. 

