The reason for doing a layup on a sheet of glass. If placed between 2 sheets, you can hook a vacuum pump to it & get a nearly impenetrable surface due to the mold being so smooth.

Ed

 

aka as vacuum bagging.

 

vacuum bagging is a good idea but there is a problem it is used to make molds. i would be hard to make a waterjacket this way.

i see what you are saying yankneck but the time and money put into building it would be amazing and hard. carbinfiber is expensive and a beeech to work with.