Lets reflect on them in reverse. How will we get 3 cubic yards of concrete into the 2 foot diameter fiber form tubes? Where is that darn Easy Button when you need it!
How will one person, working alone support, locate and level the correct length of form tube in each of the pier holes? This was tricky but a close study of the picture shows my helpers, vertical Z axis board, pivoting X and Y 2x2 attached to form and batter board strings above. With the addition of two staked parallel side boards and some screws into the tube the deed was done!
How deep below grade would the piers need to be (4 foot) and how would they be dug? That was easy!
Puzzler - What is the formula for calculating the volume of these tubes? How many cubic feet in one cubic yard?
Tech Vocab - Fiber Form, Batter Boards, Plumb Bob, Transit, X, Y, Z axis