Threads

[aged_sage]

Karel:

I use 8.5%.

John:

I have spent several hours pursuing the question of the tensile strength of a multi-strand thread/rope being the sum of the individual parts over the past two weeks, and have "Googled" it to death! I still have not come up with a definitive answer; so I posed it to a PhD physicist friend of mine last evening; and he did not have an immediate answer.

The problem goes all the way back to the mid-1700's when a French man of science first published a paper in which he claimed the the tensile strength of multiple strands was greater than the sum of the total. He subsequently published a paper in which he retracted his earlier claim, and stated that the the tensile strength of the whole was less than the sum of the individual strands. This is what was published in the 1911 version of Encyclopedia Britannica, and seemingly has been taken as 'gospel' since that date.

It only stands to reason that work has been done in this realm since the 1700's, but I have found Google to be a waste of time in trying to find references to more recent studies; even in the area of "the physics of rope". I did find one site where they answer questions from school teachers, and where three different individuals took a stab at an answer. All there were highly qualified; with nothing definitive, other than to lead one to believe that the sum is equal to or greater than the total of the individual components.

I personally, and intuitively, agree with one who said something to the effect that: "... intuitively, the end product is equal to or greater than the sum...". otherwise, why do they make ropes of varying diameters, and numbers of strands, to meet the needs for dealing with heavier and heavier 'loads' (increasing tensile stress)?

Almost everything I found had to do with WHY ropes break!

Of little value to us, at least as I see it.

Thus, at the moment, I would have to say that the jury is still out on the subject, in terms of something definitive on the subject that is more recent than the mid-1700's!

aged sage

[karelgol]

Perhaps an explanation may lay in something like "less surface area for more material". The threads in the middle of the rope are through friction supported by the threads surrounding them and therefore seem stronger? Could be, dunno. Still, as the tip is the weakest point, the strength of the furled leader isn't that interesting to me. Might have something to do with fishing line being bought here(Netherlands) by diameter and over there(England/US) by lbs breaking strength.

Karel

[jstraightj]

My family raised mink for 40 plus years. At the peak we were pelting 5000 per year and I helped skin most of them. If you ever skinned a mink you might think twice about using any product that contained mink oil. Smelly job, about like skinning a skunk. No fleas on a mink, underfur way to dense. In the wild fish is a major staple of a mink's diet, so if a fish knew a mink was around I think they would run (swim).

Sorry, guess I've got a little off topic.
John

[aged_sage]

istraighti:

The 'essence' of mink, like that of a skunk, comes from the two small anal glands, (mink and skunks are 'first cousins') and therefore, would not be expected to be found in the oil. Mink oil is rendered from the fatty layer found on the skin, which you well know, is scrapped off before stretching and 'drying'. I have used Mink Oil for years to 'waterproof' my leather deck shoes, and to keep them soft and pliable. No offensive odor to any that I have ever used.

aged sage

[jstraightj]

aged sage

Your right on all counts. After 25 year absence I still can't get past the memory of " 'essence of mink". I picked up a road kill mink a couple years ago, intended on using for fly tying, summer pelt was no good, just brought back that unforgettable aroma. We tried collecting fat from fleshing process for a couple of years for sale to a mink oil products company. Not enough $ to justify the effort.
John

[aged_sage]

istraighti:

Though I have never had the 'privilege' of even a whiff of the 'essence of mink', I truly understand your comments about never 'getting past' the memory. My similar experience was with a rendering plant on the 'downwind' side of a major U.S. highway that went from my hometown to our county seat. There was 'world class' swimming pool near this highway and you had to past the rendering plant to get there from my hometown. We got exposed to the aroma both going and coming. !UGH!

aged sage

[aged_sage]

A follow-up to my post #21 on 2-11-11.

I posed the question about the final tensile strength of a multistrand 'rope' being equal to the sum of the tensile strength of its individual strands (threads) to a physicist friend. His response was that as long as the strands lay side-by-side, and not twisted together in any way, the total tensile strength would, in fact, be the sum of the tensile strength of the individual strands.

HOWEVER; if the strands are in anyway twisted together, then the tensile strength is LESS than the sum of the tensile strength of the individual strands. It all has to do with uneven distribution of the various stresses when under tension. Thus, the tensile strength of the tippet ends of our furled leaders is less than the sum of the tensile strength of each individual thread in it.

aged sage

[Jack Hise]

Had I know that we would have been overwhelmed such "High Tech Long Winded" responses we have been subjected too I would not have asked for this forum! Furled leaders are fun to make and they work! So can't we just leave it at that?

[JohnScott]

Had I know that we would have been overwhelmed such "High Tech Long Winded" responses we have been subjected too I would not have asked for this forum! Furled leaders are fun to make and they work! So can't we just leave it at that?

.... being careful about what you ask for ??

[JohnScott]

A follow-up to my post #21 on 2-11-11.

I posed the question about the final tensile strength of a multistrand 'rope' being equal to the sum of the tensile strength of its individual strands (threads) to a physicist friend. His response was that as long as the strands lay side-by-side, and not twisted together in any way, the total tensile strength would, in fact, be the sum of the tensile strength of the individual strands.

HOWEVER; if the strands are in anyway twisted together, then the tensile strength is LESS than the sum of the tensile strength of the individual strands. It all has to do with uneven distribution of the various stresses when under tension. Thus, the tensile strength of the tippet ends of our furled leaders is less than the sum of the tensile strength of each individual thread in it.

aged sage

... your friend is probably in a minority. I did find some very interesting literature on this subject a while back but didn't bother to post it at that time. Karel's comments above were right in line with that research on the point that "The threads in the middle of the rope are through friction supported by the threads surrounding them and therefore ( seem ) stronger?" ( see his post 2-1-11 )

The stuff I read was way over my head - but when someone spends twenty plus pages of narrative and formulas to basically say what Karel pointed out and what seemed true to me just on an intuitive basis and by personal experience, I found it pretty persuasive.

John

With apologies to Jack Hise, of course.