Look Mom... nothing touches!
The problem is friction. For the same reason that you can hold a 2,000-pound load on a winch with 2 fingers by virtue of 3 wraps, a tackle where the line going up rubs against the line going down will waste energy from the start and virtually lock-up when it gets within 6 block diameters of finished.
I keep this cheat sheet handy for when the davit tackle gets tangled; typically a well meaning guest detaches it and drops it to one side, unknowingly passing the block through the tackle. Oops.
4:1 blocks have a trick too: