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Some Knot Testing Data

Discussion in 'Archives - Yahoo Canyons Group' started by Tom Jones, Nov 15, 2005.

  1. Tom Jones

    Tom Jones Guest

    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: ratagonia@zdnetmail.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.
  2. Benny R

    Benny R Guest

    2 quick questions about this post:

    1) What do you mean by a Rappel Knot? 2) Any links to visuals for this figure of 9?

    --- In Yahoo Canyons Group, "Tom Jones" <ratagoni@x...> wrote:
    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: ratagonia@z... > 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. >
  3. Tom Jones

    Tom Jones Guest

    A "Rappel Knot" would be one for tying two ropes together, to rappel as climbers do, toss and tangle.

    Visuals? Nein! (sorry, couldn't resist).

    Tie a figure 8, but go one half-turn further before putting the rope in the loop. It looks kinda messy, and does not dress very well, which I think is part of the reason it will not fully invert. It is also easier to untie than a figure 8.

    Tom

    --- In Yahoo Canyons Group, "Benny R" <benjaminroberts@h...> wrote:
    2 quick questions about this post:
    1) What do you mean by a Rappel Knot? > 2) Any links to visuals for this figure of 9?
    --- In Yahoo Canyons Group, "Tom Jones" <ratagoni@x> wrote:

    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: ratagonia@z...
    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.
    >
  4. Surely you aren't suggesting conclusions can be drawn from a single datum? At best you'll only confuse the issue with a statistically insignificant result. Was there more data that went with this report?

    Steve Tucson, AZ

    --- In Yahoo Canyons Group, "Tom Jones" <ratagoni@x...> wrote:

    snip....

    > 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.
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