|
|
Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
|
OP
Carpal Tunnel
Joined: Jan 2001
Posts: 13,858 |
From an article in New Scientist for Dec 29, 2001, p. 58 During WWII a number of US warplanes en route from Labrador to Iceland were forced by storm to land on Greenland. All the airmen survived, but the planes sank into the ice, until by now they are 80 meters, about 250 feet below the surface. A team of adventurers has recovered one of the P-38s. After managing to find the location, they sank a shaft down to the plane, and then descended to it by " abseiling" down to it. I knew this was a rock climbing term, and found a site of rock climbing terminology. Perhaps the terms might be worth discussing. http://www.theclimbershub.co.uk/dictionary/dictionary.asp?Term=abseil
|
|
|
|
|
Joined: Nov 2000
Posts: 866
old hand
|
|
old hand
Joined: Nov 2000
Posts: 866 |
A synonym for abseil is rappel - and you'll find this word is the one used most by the people that do it.
To climb up a rope with the aid of a friction device is to prussick. Couldn't find this at the above URL.
I did a fair bit of both in my younger days - but mainly into old mines. As I recall there were a lot of european terms - not surprising considering the origins of climbing as a sport. Words such as carabiner (snap clip for tethered or free running ropes) and piton would be known to most. Considering lives are involved, the huge amount of technology behind the development and manufacture of climbing gear (and hence its cost) are also not surprising.
stales
|
|
|
|
|
Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
|
|
OP
Carpal Tunnel
Joined: Jan 2001
Posts: 13,858 |
Dear Stales: Rappeling and abseiling are both means of descending in a controlled manner. The abseil mentions use of a figure of eight. I gather that the rope goes about the person in a way that rate descent can be controlled, but can't imagine how the user prevents fouling or excessive tightness.Or worse still, sudden loss of control.
The chimney down through the ice apparently gave very little freedom of movement.
I haven't finished the article yet, so don't yet have any idea how they were able to dig a chimney big enough to lift the plane straight up two hundred and fifty feet! Incidentally, that means the planes sank five feet a year, meaning the ice isn't as solid as you might think.That's almost two tenths of an inch per day.
|
|
|
|
|
Joined: Nov 2000
Posts: 866
old hand
|
|
old hand
Joined: Nov 2000
Posts: 866 |
A 'Figure of Eight' friction device is two loops of a special aluminium alloy about 3/4" thick joined together. 'Chunkiness' is important because the heat from the rope passing around the device needs to be disseminated through it - or the heated device will melt its way through the rope if the rapeller stops during a rapid descent. One end of the device clips via a carabiner ("crab") to one's harness, the other hangs free. A rope is passed once or twice around the outer loop then across the throat of the device, between the two loops. The rapeller holds onto the upper part of the rope (if descending backwards - the least terrifying way!) and grips the free end of the rope behind their buttock. If they're using the correct configuration of rope, descender and turns around the device, little more than a strong handshake grip is sufficient to control their descent.
For the record, and despite their popularity, I believe Figure of Eight descenders to be potential killers and won't use one. A guy died on a cliff near my place because his Fo8 snapped across the middle whilst he was descending. When this happens you are left with a useless loop on the rope - and not connected to you, so down you go. I always used a 'whaletail' device instead. These are a block of alloy, rectangular in section and about a foot long. Along one edge are a series of protruding 'whaletails' - lipped wedges - around which the rope passes. Much safer, far greater heat sink capacities and, even if a wedge or two snap off (never heard of it happening), there's still a few left to get you to the bottom. The construction of a whaletail also lets one tie themselves off during a descent if they need a rest or if they need to use both hands. Difficult/suicidal with a Fo8.
As you say, the rope must hang free. A big step to ensuring this is to use a braided rope rather than a 'wound' rope (ie twisted). The rope consists of a core of tiny kevlar or nylon fibres, only thousandths of a millimetre thick, each as long as the rope itself. They are held together by a woven braid casing. (I recall a previous discussion on ropes - in relation to casement windows). The rope itself will be rated not only by its breaking strength, but also by its 'bounce' factor. Climbers require ropes with a high stretchability so they won't be pulled up hard if/when they fall. A rapeller on the other hand doesn't want a bouncy rope, it makes descending unpleasant and difficult to control (hence less safe).
Ropes are carefully coiled in a special way, rather like plaiting, and packed into bags. Done properly, the rope will undo itself without kinks or snags if it (and its bag) are tossed from the anchor point at the top of the descent. Looping them like a cowboy's lariat is guaranteed to induce loops and tangles and therefore not regarded as a long term practice in the field. They should also never touch the ground or be trod upon - the tiny particles of dirt will chop their way through the braided wrapping.
Rapelling with only a rope is achieved by wrapping the rope around your limbs and trunk and using clothing as padding. This is highly ineffective with a braided rope (they are made to operate with a low coefficient of friction and hence extremely difficult to grip), and more easily achieved with a wound rope. Only for emergencies in my opinion.
BTW - The bottom end of the descent rope should have a large knot tied in the end so the person doesn't rappel off into space. A sky diver friend of mine has however rappelled off a rope at 10,000' from an aircraft!
stales
|
|
|
|
|
Joined: Mar 2000
Posts: 11,613
Carpal Tunnel
|
|
Carpal Tunnel
Joined: Mar 2000
Posts: 11,613 |
The chimney down through the ice apparently gave very little freedom of movement.
Okay--in a mine, I think what you're describing is called a shaft. Why is it a chimney, here, please?
|
|
|
|
|
Joined: Jan 2001
Posts: 13,858
Carpal Tunnel
|
|
OP
Carpal Tunnel
Joined: Jan 2001
Posts: 13,858 |
Dear Jackie: there is a very extensive list of climbing jargon. Chimney is just one word I have seen for a narrow vertical passageway. Just search for "abseil" and see how many sites there are! "Seil" is German for rope, and "abseil" just means to go down a rope. As Stales' very informative post indicates, there are a number of different kinds of rope, and different kinds of devices to control rate of descent. Not for me.
|
|
|
|
|
Joined: Nov 2000
Posts: 866
old hand
|
|
old hand
Joined: Nov 2000
Posts: 866 |
> Why is it a chimney, here, please?
Thanks for the reply on this wwh - spot on.
Y'all may like to know that climbing has also spawned 'chimney' - the verb - ("We'll have to chimney that section of the climb"). This style of ascent or descent is where the climber braces their back against one wall of the chimney and locks their legs against the opposite wall - movement being afforded by little shuffling steps up or down. Hence 'chimneyed' and 'chimneying' as well ("Joe took the lead while we were chimneying that section").
stales
|
|
|
|
|
Joined: Jan 2001
Posts: 1,773
Pooh-Bah
|
|
Pooh-Bah
Joined: Jan 2001
Posts: 1,773 |
[Bob Rivers]
There's something stuck up in the chimney
And I don't know what it is,
But it's been there all night long.
Well, I waited up for Santa all Christmas night
But he never came and it don't seem right.
And there's something in the chimney
And it doesn't make a sound,
But I wish you Merry Christmas.
There's something stuck up in the chimney
And I don't know what it is,
But it's been there all week long.
Well, the dog keeps barking up the chimney flue
And we don't know what we're going to do.
Cause there's something in the chimney
And it doesn't move around,
And it's been a week since Christmas.
There's something stuck up in the chimney
And I don't know what it is,
But it's been there all month long.
Well, it's jammed up tight above the fireplace
Now the house smells funny, such a big disgrace.
That there's something in the chimney
And it doesn't talk at all,
And it's been there since last Christmas.
There's something stuck up in the chimney
And I don't know what it is,
But it's been there all year long.
I'll been waiting up for Santa like I did last year
But my brother says, "He's already here."
And he's stuck up in the chimney
And he doesn't say a word
And he'll be there every Christmas.
And we'll have him every Christmas.
[/Bob Rivers]
|
|
|
|
|
Joined: Nov 2000
Posts: 3,146
Carpal Tunnel
|
|
Carpal Tunnel
Joined: Nov 2000
Posts: 3,146 |
It's been dunnamany years since I did any abseiling. But others have tried ... Below is a synopsis of a Darwin Award-winning prison escape attempt in the US a couple of years ago. The Darwin Awards, for those of you who don't know, are awards handed out to deceased people who have managed to remove themselves from the human gene pool in bizarrely stupid ways. The Awards are managed by one Wendy Northcutt who has a website at http://www.darwinawards.com. She has also published, I believe, two books' worth of award winning deaths, honourable mentions and urban myths on the subject. Well worth a read as well. This tale comes from the first book. A prison in a new, high-tech prison decided that he could escape from it through a window if he managed to tie enough sheets together. He did quite well in that area, because he got enough sheets to make a "rope" that was about 100 feet long. Timing it just right, he smashed his way through a toughened glass window, tied off one end of his "rope" and flung the rest of the bundle out the window. Clambering carefully over the broken glass on the lower rim of the window, he trusted his weight to the sheets and began the perilous climb down. Unfortunately, that sharp glass was having an effect on his "rope", and his weight dangling below the window enabled it to cut through the sheet draped over the window frame. Our intrepid escapee fell to his death on the concrete below. Sad? Well, maybe. But one can't help but wonder what would have happened in any case even if he had actually managed to get to the bottom of the makeshift "rope". It was, as mentioned above, about 100 feet long. The drop to freedom was, unfortunately, 180 feet ...
The idiot also known as Capfka ...
|
|
|
|
|
Joined: Nov 2000
Posts: 3,146
Carpal Tunnel
|
|
Carpal Tunnel
Joined: Nov 2000
Posts: 3,146 |
I remember following the progress of the expedition to recover the P38 from the icecap. I don't remember it being 250 feet, but I can't argue, since I no longer have the Flight magazines that were chronicling the recovery. But Stales is right in making the assumption that the majority of the overburden was deposition rather than the aircraft "sinking" into the ice. They did some studies at the same time as I remember it.
In Zild there are two glaciers, Fox and Franz Josef, which are apparently unique in that they descend to nearly sea-level in a temperate country. At various times I've been to the neves of both of them. They rise, very steeply, to about 8,000 feet. Both of them have huge neves, heavily crevassed last time I was there. They drop so steeply that the icefalls are spectacular and damned dangerous to climb, to boot.
Glaciers are fed by snowfall in the neve as Stales says. If there isn't much snow for a few years, the rate of flow falls away. In the case of Fox and Franz, this has been the case now for about twenty years, and they have actually both retreated up their valleys about seven miles. The retreat is caused by melt-off (which everyone blames on global warming) but for a number of years before (I think) 1975 they were actually advancing at quite a rate. It's a balance between attrition and deposition, and at the moment attrition is winning hands down.
The local geologists have a field day (literally) at Franz and Fox, because almost all of the glacial landforms are there, raw and fresh, just begging to be studied. Whatever turns you on, I say!
The idiot also known as Capfka ...
|
|
|
|
Forums16
Topics13,913
Posts229,344
Members9,182
| |
Most Online3,341
Dec 9th, 2011
|
|
|
0 members (),
782
guests, and
2
robots. |
|
Key:
Admin,
Global Mod,
Mod
|
|
|
|
