I have for years used to install baffles in my ballast tanks by cutting round discs from pvc sheeting then drilling small holes in each one then glueing them in one by one.
Now I have found a much easier way.
This can be done from schedule 20 pvc sizes 2 inc to 6 in.
The baffles are the inspection plugs not the regular caps,just trimoff the lip and drill a hole to fit your threaded threded shaft in each baffle,preferably in the middle.
Then install one nut on one end then a spacer or stanoff that the shaft will fit threw,then a baffle then a spacer,just repat that last step untill the desired number of baffles is made,these are one inch spaceing and use no holes.
No holes! The clearance between the tube wall and baffle is large enough to let pass watter without a torent.
when at the end of the shaft install the nut and tighten it.
The one showed is for the modified Robbe XXI I am currently building.
No mess and all available parts at the hardware store.
Glue the end caps on drill the vent/drain holes and your done.
Dave Amur Ship Yard