A family of Platypus (Platypusses? Platypi?) are currently in residence in Blue Lake at Jenolan. A pair of platypus were seen by SUSS on the most recent Jenolan trip. It's not the first time that Platypus have been seen in Blue Lake, but according to the Guides, this pair seem to be the adventurous type. They've apparently penetrated the resurgence at least as far as Pool of Cerberus in the southern showcaves and have been seen on the western side of the Grand Arch near Caves House. We wait with bated breath for the first account of a diver coming face to face with a platypus in the show caves (it would make a change from eels). Phil Maynard
There's been a large amount of feedback on the item in the last Bull about double rope abseiling. In brief, an abseil using two ropes will sideways load a figure eight knot if that is the knot used to tie the ropes together. This has resulted in at least one fatality. Here's some more information about this. The mechanism by which a figure eight knot can fail if loaded sideways is not simple slippage. The knot is actually pulled inside out, and due to the symmetry of the knot the result is a figure eight knot which looks exactly the same as the original knot -- except that the tails of the knot are now ten centimetres shorter. The process can repeat until the tails pull through the knot and the ropes part company. The force required to invert a figure eight is high enough to be outside the realm of normal loading during an abseil - a shock loading is required. However, if the knot is incorrectly laid (the strands cross over each other inside the knot) then the load required to invert the knot can be Very Low.
Many people advocate (and are taught) the use of an overhand knot instead of a figure eight knot to tie the ropes together. Because an overhand knot is asymmetrical, it should not be able to repeatedly invert when sideways loaded. Is an overhand knot safe? This has caused many arguments in the climbing community, but the following is the only data produced on the issue that I know of. This was posted to the rec.climbing newsgroup (sorry about the American units. 2.2lb = 1kg).
From: Tom Moyer tmoyer@alum.mit.edu Newsgroups: rec.climbing
Ok - here's the next round of tests. Should add a little more fuel to the fire...
Some comments: When the overhand inverts, it doesn't really do the same thing as the 8 does. The 8 flips completely around and it's really obvious. It also eats a huge chunk of the tails when it does. The overhand kind of twists a little, some more rope goes through the knot, and the force goes down. Any time I pulled on the come-a-long and the force went *down* a few hundred pounds or more, I noted the peak force before it happened. I'm going to change my terms and call it "rolled" to differentiate it from way the figure-eight behaves.
Tests 18, 19, and 20 are on double fisherman's knots, pretty much the gold standard for comparison. As before, the load is on a single strand, with a figure eight on a bight at each end. For #19 and #20, the double fisherman's is loose and mis-tied in every way I can think of that you could still sort of call it a double fisherman's knot. Definitely the worst excuse for a DFK I've ever seen.
Rope B: Unknown manufacturer red 11mm dynamic - used
Test #13: RopeB/RopeB - overhand - well dressed, pretensioned loosely.
Rolled at 1070lb, Rolled at 1120lb, Rolled at 1470lb, Rolled at 1870lb, Rolled at 2000lb, Rope broke at 2100lb
Test #14: RopeB/RopeB - overhand - sloppy, crossing strands & loose.
Rolled at 200lb, Rolled at 370lb, Rolled at 1400lb, Rope broke at 2100lb
Test #16: RopeB/RopeB - overhand - sloppy, crossing strands, loose (again).
Rolled at 300lb, Rolled at 420lb, Rolled at 1440lb, Rolled at 1520lb, Rope broke at 1830lb
Test #18: RopeB/RopeB - double fisherman's - well dressed & pretensioned.
Rope broke at double fisherman's at 2880 lb
Test #19: RopeB/RopeB - double fisherman's - sloppy, mis-tied & loose.
Rope broke at the figure-8 on a bight at 2580lb
Test #20: RopeB/RopeB - double fisherman's - sloppy, mis-tied, loose & WET.
Rope broke at double fisherman's at 2620lb
Editor's Comment: 200lb?????? If an overhand knot is not correctly laid, it could easily kill an abseiller. Be warned.
The last three months have flown by. In late July we held a training weekend at Bungonia. Nearly 30 people attended and we covered topics from knots to rigging and navigation to first response. We also managed to sign off on two trip supervisors - congratulations to Megan Pryke and Martin Pfeil.
The project work at Jenolan has been proceeding apace with a new entrance to Wiburd's connected last month. With regular trips every month this is an area worth visiting if you haven't done so already. We have also been caving around the state from Wee Jasper to Wyanbene and Borenore. There are plenty more caving trips coming up and with summer around the corner the canyoning trips are creeping into the program.
There are two big trips on the cards for January - Mole Creek in Tasmania-- one for the formation freaks - and Waitomo in New Zealand. Full details are on the trip list. I have also heard rumours of a week long canyoning trip between Christmas and New Year so keep an eye out for that one.
On a more administrative note, the committee is looking at the finances for next year. Since the union stopped allowing us to also be registered with the sports union our finances have been tight. Last year our ASF bill also increased dramatically due to a fee hike and the removal of the first time student category. In planning our budget for next year we are looking at a fee increase of over 20% if we remain a member of ASF. The committee is currently investigating the option of withdrawing from the ASF and the impact this would have on the areas in which we cave. If we were to withdraw there would be a fee decrease. If you have any comments on this, please let the committee know. Annalisa Contos
The OZTeK Australian Diving Technologies Conference was held in Sydney on the 14th - 15th of September 2002, and SUSS was there. Greg Ryan and Keir Vaughan-Taylor presented an overview of cave diving at Jenolan through the years, from the early assaults on the Imperial streamway in the 1950s up to the most recent underwater mapping in the southern showcaves (can Platypus carry compasses and depth gauges?). The presentation was well received and promises to make for a good monthly meeting sometime soon. Phil Maynard