The shell is made of PVDC plumbing pipes (Rain Pipes) available at Do-It-Your -Self Stores assembled with some aquarium glass silicone. 

The central tube is connected to the two motor tubes with a double mounting ring adapted. 
Holes are drilled for cables, antenna and blow tank. The hemisphere is a simple Christmas ball of the same diameter  drilled on the top and the bottom to let water enter.

I used several Air Compressor connections adapted with gasket to close the opening needed for cables to pass through. 

The sub is sanded and painted with automotive paint. I use high temperature painting because is easy and fast to dry. 

  << Click here  to See the plan

 

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