This do-it-yourself material can be made for a fraction of what you would pay if you bought it, made up, from your local supplier.   You will use sizeable quantities of filler (commonly referred to as “BOG”) during construction of any fibreglass boat.   There are several materials that can form the dry ingredients of the resin putty mixture.   These include industrial talcum powder, Q-Cells and micro balloons.  When mixed with waxed polyester resin and a small amount of additional accelerator they make and excellent and economic filler. This material, if stored in a covered container, will keep for up to two or three weeks. When you want to use the filler, you simply dig out a quantity and place it on a mixing board.   You then add a dash of catalyst.  This does not have to be measured, as you will soon gauge the mount required to make the bog set in the desired time. Check with your local fibreglass supplier as to the recommended materials.