The water tank arrived at the house safely the other day. There's a picture of it above, next to the house. Earlier today, I pulled it out to clean it up and rinse out the inside.
The image below shows the octagon frame that the tank will sit inside. My idea is that the tank needs to be raised just a bit so that I can water the garden via a gravity feed. So the guy at the pump shop where I bought the tank had an idea to build a frame that will contain pea gravel, then the tank can sit on top of that. It will be sturdy, flat and relatively level. I don't have to worry about the frame needing to support any weight since the pressure of the full tank will be directed straight down, not down and out. The frame will only need to contain the pea gravel.
In order to make that frame, I had to find out what the formula is for determining the length of the sides of a regular octagon if I have the diameter from the middle of opposite sides. Googling around, I found a formula I could work with and determined a length. Rita had the good idea to double check my work with a mechanical engineer friend, who came up with a) a simpler way to do the calculation, and b) an answer that was almost half of what I came up with. Good thing I checked!
I rounded up to lessen the waste of the cuts of wood, but didn't use my brain when making the cuts. I took 360 degrees and divided by eight (angles), which gave me 45 degrees. Well, if you have a couple of 45's, you get a 90 degree joint. I remedied that blunder by pulling out the table saw, setting the angle of the blade to 22.5 degrees (roughly) and removing some material that slightly shortened the outside length. Then things started fitting much more as I had expected.
A couple of screws at each joint brought it all together. Now to go calculate how much pea gravel I need (area of an octagon, anyone?).