More stuff on knot strength.

"A figure eight follow through, for instance, is often cited as having 80% of the strength of the rope. In our tests this ranged from 100% – it did not fail at the knot in climbing ropes in about a quarter of cases, including in a UIAA fall test that we observed – to near 50% in 5.5 Spectra/Titan cord. "

"Nor does it matter if the eight knot is “sloppy” or “neat”. In fact we tested quite a few figure eight knots, in a variety of ropes, that were improperly tied so that the last pass of the “follow-through” was not made. Did it matter? Drum roll please: sometimes it tested stronger than the “correct” eight and in a third of our tests it did not break at the knot."

http://efclimbers.net/wp-content/uploads/2013/02/Knot-and-cord-strength.pdf