Extreme depth sounding with rope

[Vicarious Reality]

How does one measure eight kilometres down by lowering a rope? How do you know the rope has hit the bottom?
The weight of a sturdy hemp rope as used by the Challenger expedition has to be enormous, so how could you possibly know when the weight stops?

This is very confusing...

http://www.classroomatsea.net/general_science/challenger_exp.html

 

[Frezzato]

Interesting. Nobody seems to explain the process very well.

Without knowing anything about this process, one could guess that a team lowers the weighted rope over the side, into the ocean, allowing the 100-lb. weight to carry the rope to the ocean bottom. I suppose the next step would be to tug on the rope to see if they encountered any resistance. If the state of the rope goes from slack to tight, it could be surmised that they've reached the ocean bottom. They would mark that spot on the rope somehow, and then proceed to reel in the rope, and finally measure or record how much rope they recovered, giving a fairly reasonable depth measurement.

This is all just a guess on my part.

*EDIT*
Then again, perhaps they just continuously lowered and recovered the rope at certain lengths, with something like a bucket on the end. If the bucket came up with something, then they would know they hit bottom.

 

[Vicarious Reality]

Wait.... maybe they weigh the rope

If the lead is hove properly, so that the line pays out with a little tension as it passes through the hands, it is easy to tell when it has reached the bottom by the sudden slack felt in the line.

Well, that i thought of, but how would the rope slack if there are THOUSANDS OF METRES of it hanging down? I do not think hemp rope is particularly boyant... is it?

 

[Frezzato]

Wait.... maybe they weigh the rope

I think my initial guess was closer to the truth, although I could only find one explanation for the process, here [http://www.navyandmarine.org/planspatterns/soundingline.htm].

He would then swing the lead round and throw it as far forward as possible, so that the lead would be resting on the bottom and the line tight, when the vessel is directly over the lead.

If the lead is hove properly, so that the line pays out with a little tension as it passes through the hands, it is easy to tell when it has reached the bottom by the sudden slack felt in the line.

 

[Dirty Hipsters]

I came in here expecting...I don't know what I was expecting, probably weird porn.

 

[Irick]

Wait.... maybe they weigh the rope

I think my initial guess was closer to the truth, although I could only find one explanation for the process, here [http://www.navyandmarine.org/planspatterns/soundingline.htm].

He would then swing the lead round and throw it as far forward as possible, so that the lead would be resting on the bottom and the line tight, when the vessel is directly over the lead.

If the lead is hove properly, so that the line pays out with a little tension as it passes through the hands, it is easy to tell when it has reached the bottom by the sudden slack felt in the line.

One would think that the currents would make this difficult. Maybe they had to vary the weight of the lead weight depending on the intended maximum depth of the sounding line? or maybe the rope was naturally a bit buoyant so the difference was rather obvious...

heh... these are interesting problems to contemplate.

 

[Ten Foot Bunny]

I came in here expecting...I don't know what I was expecting, probably weird porn.

You are one sick puppy. I like that quality in a person.

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OT - Penguins like to dive. Find some penguins with rope experience and foster their research ambitions. Pretty soon, the best, the bravest, and the strongest penguins will come forth, ready to take their species to depths previously unthinkable. Humans, pengins: two tetrapods, one goal. For science!

Spoiler: These penguins are ready. Are you?

 

[BeerTent]

OT - Penguins like to dive. Find some penguins with rope experience and foster their research ambitions. Pretty soon, the best, the bravest, and the strongest penguins will come forth, ready to take their species to depths previously unthinkable. Humans, pengins: two tetrapods, one goal. For science!

Spoiler: These penguins are ready. Are you?

I to was ready for something a bit more exciting. I guess I'll have to put my pants on.

Ooh! Penguins!! This video is awesome! Their minds are so blown by that rope. I take it the training process is going to take a while, hunh? I imagine by 2016 thay'll have learned that one tug is "I'm fine." Two tugs are "Help me up." and 4 or more tugs are "DEAR GOD CTHULU IS PISSED! GET ME THE FUCK OUT OF HERE!!"