A show on Discovery Channel a couple of weeks ago claimed that a “rope” made of spider silk (the stuff spiders use to make webs) of the same diameter as a pencil could stop a Boeing 747 flying at full speed.
I really have trouble believing this - how could this possibly be?!
I thought I was going crazy until I looked this up and saw a couple of other references to it. Search in Google for “spider thread strength 747” and you’ll find plenty. All the ones I looked at seemed rather second hand, though -very Urban Legend-like.
Wow! That’s quite a claim, SenorBeef!! You’ll pardon me if I don’t subscribe to that level of ambition early on a Sunday morn…
However, I distinctly recall reading in a grade school science text that spider web has roughly three times the tensile strength of steel. Of course, such a comparison would have to take into consideration things like cross-sectional area, etc.
First off, the phraseology used by all the links produced by the Google search are just too similar. It makes me think they are derived from one source, or each other. In fact, the first two links have many of the same diagrams and incorrect terms (see below).
Secondly, most of the sites are religious in nature–either creationist claptrap or sermons. Nothing wrong with sermons, but not my first choice for scientific info.
Even the first site, which appears to be scientific at first glance, is a bit too “gee whiz” for my tastes. Here is the relevant phrase.
But then the site goes on to say:
I’ve never heard of a “dernier,” especially with respect to the strength of a material.
Ahh, this is more of a UL than anything else. Spider silk (webbing) is not “stronger than anything known to man” or even close. But they told me that in third grade too.
There are two basic varieties - dragline silk (strong) and the regular stuff (sticky). Two basic cites:
For comparison, piano wire has about a 475 000 psi ultimate strength, and the steel used in common nails (mild steel) is more like 40 000 psi. So, nothing amazingly strong, although it’s up there with some of our better materials.
But the kicker is that the spider silk elongates quite a bit (30% IIRC), so it can absorb a fairly large amount of energy before failure. I think one of the links above discusses that aspect in more detail.
A fully loaded 747 weighs about 800 000 lbs, and can fly mach 0.85. I’m not sure how they made their calculation, but with the “factoid” presentation I’d have to say it sounds pretty iffy.
I suppose if it were used as a tow line tied to something solid to stop the plane it might work. But I’m too lazy to figure it out this morning.
From the data I posted in this thread* for the tensile strength of a spider thread, the tensile strength for the “capture spiral” is 1338 MPa. A pencil has a diameter of 7.0 mm. Thus, a thread of spider silk with the diameter of a pencil has a max strength of 51,500 N (11,600 lb). Pretty impressive, but nothing compared to the max takeoff weight of a Boeing 747-400 Passenger jet, which is 875,000 lb.
Since this thread can’t even support the weight of the jet at rest, there’s no way it’s going to “stop [it] flying at full speed.”
*BTW, what was the rationale for starting an additional thread with such a similar topic?
A black widow or brown recluse can be deadly to humans, but not necessarily so. I have seen a number of news stories about how strong spider silk is, how some people want to make bullet proof vests out of it and how they are going to do genetic engineering on goats to make goats produce the stuff in their milk. Getting it from spiders just isn’t practical apparently.
Wow! No activity on this thread all day (for more than 6 hours), and when I decide to revisit this thread, multiple simulposts! Great minds must think alike!
Anyway, I hadn’t seen Thrasymachus’ contribution when I posted, but considering these new figures, they seem to be comparable to mine.
With the conversion 1 MPa = 145 psi, the 200,000 psi for dragline silk corresponds to 1380 MPa, which is on par with the figure I used above.
Oh, and apparently manhattan has closed the other related thread.
I don’t see why that would be advantageous. From Thrasymachus’ link above, Kevlar 29 fiber has a tensile strength of 2700 MPa (400,0000 psi), which is twice that of spider silk.
Also, Thrasymachus, the maximum extensibility of the capture spiral thread is an incredible 476%. The weaker radial thread’s average extensibility is 39.4%.
So how are they going to get goat’s milk up a spider’s butt? Oh, wait: goat’s milk… So, goats are gonna be spinning webs with -, um, oh, man, the thought of this is getting pretty wierd right about now. - DougC
Just to nitpick: it’s bullet-resistant body armor. If it were bulletproof no bullets could get through it. I love throwing that out to the reporters and prducers I work with!
I know nothing about spider webs or their relative strengths…
however, I do know something about fibers.
The term “denier” (just one “r”) does, indeed, refer to the thickness of a fiber. It was originally used to describe silks, but is also used for other fibers. This thickness is important for those who work with fibers; the tensile strength would be entirely dependant on the content of the fiber in question. This site-scroll down about a third of the way-gives a bit of an explanation. I couldn’t find anything much clearer. In any case, it is a term which is (I’m guessing) more useful to fiber artists than anyone else.
Yeah, but that’s kinda like the same theory “Enough small pebbles piled in one spot can stop a train dead.” or something like that. If you put enough of something in one spot it will be able to do something you wouldn’t expect. I would be amazed if one spider could do that in a set time period, but the fact you propose does not impress me.
If you get enough republicans in the way of a train…
