So I've never seen this done, so I thought I would post my idea for a compromise between a sparge arm and batch sparging for those who want to try their hand at fly sparging. It's basically just some 3/8" copper tubing bent into a spiral with 70 3/32" holes drilled along the length (see picture below). I chose this design because a) I already had all the materials to do it this way, so no cost, and 2) it offers an adequate coverage of the grain bed with no moving parts. I still need to do a bit of tweaking, mostly just to get each ring of the spiral to sit even with each other, but it works well enough that I feel confident I can have it dialed in by brew day on Saturday. If anyone builds this, let me know how it works for you.
Here's the bottom:
And here it is all set up:
Here's the bottom:
And here it is all set up: