Found some of my own testing Data over on the Fish Products site (thanks Russ). People might find it interesting: Someone out there proposed the Figure 9 knot as a superior Rappel Knot. The loading situation is the same as using your rope tie-in loop as a belay loop. A figure 9 knot is like a figure 8, but you go a half-turn further before finishing it. BD Test Doc # TD 15025 4-28-99 Tom Jones Load Speed 8"/minute. 10mm steel pins top and bottom. Test was performed using a slightly used 10.5mm Yellow rope. A figure 9 knot was tied forming a short loop. Two pins were inserted into the loop and pulled apart. Performance was compared to a Figure 8 knot tested under the same conditions. Fig 9 Results: The rope stretched and the knot tightened as usual. Unlike a fig 8 knot, the fig 9 does not creep down the free ends - the knot essentially has a built in backup knot. Under loading, the knot "looks like" two knots - a front knot and a back knot. At about 2900 lbs, the front knot inverts over the back knot, and the load drops to about 2700 lbs. Loading continues and the load increases fairly smoothly up to 4000 lbs, where the sheath breaks on one side. Max load achieved was 4398 lbs. Neglible creep at the free ends was experienced. Fig 8 (with backup knot ) Results: loads up and stretches. At 1500 lbs, the knot inverts, and the load drops to about 1000 lbs. Reloads slowly, but it creeps along the free ends at a load of about 1000 lbs until it hits the backup knot. Then it loads fairly evenly to 4509 lbs where one side of the sheath breaks. Max load was 4509 lbs. My Conclusions: A. Figure 8 knot should be used with a backup knot. B. Figure 9 knot is essentially a backed up figure 8. C. Maybe I'll use a fig 9 next time. Tom Jones Black Diamond Equipment, Ltd. Disclaimer: These are my personal opinions and recommendations, and may or may not be shared by Black Diamond. Subject: Test Report - Fig 8 Tie In Knot From: email@example.com Newsgroups: rec.climbing Date: Fri, 22 Jan 1999 23:02:50 GMT I tested a figure 8 as a tie in knot using the test machine at Black Diamond. This was to see how strong the 'belay loop' formed by your tie in knot is. Rope: slightly used 9.7mm single rope Knot: follow through figure 8 like when tieing in Date: Dec 16, 1998 Setup: pulled at 4"/minute. Pulled as a loop with the knot in the center of one of the strands. Used 1" pins both ends. Results: Knot loads steadily and tightens up to 2200 lbf. At this point, the knot starts to roll, and the force drops to 1500 lbf. Then the stiff end of the rope where it is taped started to get sucked into the knot, and the rolling action stops. Load increased steadily to 4050 lbf, where the sheath on the non-knot side broke. Force drops to 3400 lbf. Load increased steadily to 4050 lbf, where the sheath on the knot side, upper strand broke. Force drops to 3750 lbf. Load increased steadily to 4884 lbf, where the core broke at the knot, breaking the loop. Conclusions: Figure 8 knot can roll in this loading configuration ( belay loop on harness or when used as quick rappel knot ) at a load on the order of 1500 - 2000 lbs. It will continue to roll until some mechanism stops it. A backup knot on a figure 8 in a pulled-apart loading configuration actual does something. I will use these from now on when rappelling. Ultimate strength of loop is > 16kN belay loop strength. Additional Comments: One data sample only gives you a general idea of what is going on. Loads for rolling and for breaking can be expected to vary quite a bit with rope size, surface conditions and loading sequence. Having one side jammed up against a chain or rappel ring may also effect this. Take this with a grain of salt, please. Opinions expressed are my own, and may or may not be shared by my employer.