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:
One more thing. While tackle twisting is caused by reeving errors, it is enabled by swivels at the top and the bottom. There should ONLY be one swivel, either top or bottom, whichever is more helpful in providing a fair lead. However, if a fair lead can be achieved with no swivel and an additional shackle, that is even better. Reduce the number of swivels to no more than one.
We spent a LOT of time on this yesterday, using that diagram as a model. No matter how we rigged it, always at least two lines touch. The main difference that I can see is that the attachment point (becket) on our block is not underneath a jammer as in that pic but rather directly in the middle of the triple blocks.
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Yeah, I looked at the high-res photos and could see nothing wrong. The post wasn't directed at you, it was directed at me! I re-threaded the offending dingy tackle today; much better.
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