#tennineace

Keep in mind, this is just my theory, I’m not 100% this is how it works. If you’ve got other thoughts, send me an ask, I love talking about this stuff.

Pre-1.11 AFK fish farms had you cast your line when the door was open. But if you just cast against an open door, you risked your bobber going right through the door, without ever triggering the tripwire. If you were lagging it was almost guaranteed. But if the door closed on its own the moment after you cast, your bobber would hit the door and you wouldn't reel it back in right away, giving it a moment to float up into the tripwire. 

In 1.11, you can cast your line against a closed door, so your bobber never gets a chance to fly past the tripwire. As long as you’re aimed at a very precise window, your bobber hits near enough to the tripwire to trigger it immediately without any need for the door to change state.

(...at least I think that's how that works. Pretty sure.)

Anyway, regardless of whether I’m right about why, it’s undeniable that the design without a redstone clock works. I also did some tests to make sure that it holds up against lag, here’s one:

It goes on for way longer than necessary, but my fishing rod was so on the beat I couldn't bring myself to stop it. As you can see, lag causes some interesting visual effects (like looking like the bobber’s stuck in the block behind the water and still catching fish) but doesn’t interfere with the machine’s functioning. Other tests included things like clocked dispensers throwing tnt out of the sky, but those videos didn’t come out as well.