Theoretical straw length

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Theoretical straw length

Postby Joe Duxbury » Oct 25, 2010 7:19 am

it is well-known that there are many extremely long straw stalactites found all over the world (what is claimed to be the longest?), but has anyone calculated the maximum possible length of such a straw, for a given diameter?
The calculation would have to assume that the limiting factor would be the strength of the straw itself, ie that it was bonded sufficiently strongly to the ceiling. If the calculation hasn't already been done, do any of you have numbers for the density and tensile strength of calcite?
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Re: Theoretical straw length

Postby gdstorrick » Mar 19, 2011 10:29 pm

Post deleted.
Last edited by gdstorrick on Jul 8, 2012 6:24 am, edited 1 time in total.
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Re: Theoretical straw length

Postby ian mckenzie » Mar 29, 2011 3:21 pm

Water drops round the world are of nearly-uniform size, as are the interior diameter of straws although the thickness of their outer walls varies. The answer would have to eliminate all sorts of variables, such as to assume that the bond between straw and ceiling is greater than that of the straw itself (i.e. the straw will snap, not detach); the wall of the straw is uniform in thickness; there are no external forces such as wind, cavers etc.

So calculate the area of a thin circle (cross section) of a typical straw, calculate the adhesive strength /molecular bond of this area to itself, calculate the weight of a cm2 of pure calcite, calculate the length of a straw comprising one cm2 of calcite, then figure out what length of straw gives you the weight necessary to shear the straw in a downward direction. Can anyone do it? Not me...

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Re: Theoretical straw length

Postby Rodney Tennyson » Jun 2, 2011 7:28 pm

While here in Arkansas there are numerous caves with long straws, the longest I have ever seen were not calcite but rather aragonite, the needle-like crystal bundles of aragonite create a much thicker side wall and are generally twice the diameter of the more common calcite straw.
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Re: Theoretical straw length

Postby Jon » Aug 11, 2011 6:25 pm

Ok here's what I heard/know/assume to be true.
Kartchner Caverns in AZ has a 21'3" soda straw. For years they argued with some cave in Australia each thinking the other had a slightly longer one. Then a 28 or 29 foot plus one was found in an unnamed cave in Mexico. I've seen a photo of the Mexican Monster and actually I'd be tempted to say that the top 4, 5 or maybe more are in that one room in Mexico. But then the photo I saw might not be the right place.
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Re: Theoretical straw length

Postby Aaron Addison » Aug 12, 2011 7:42 pm

I've personally seen the straws in the Mexican cave. They are the real deal and at least one is 9m or more. There are many over 8m in the same room.

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Re: Theoretical straw length

Postby harrym » Nov 12, 2012 10:16 am

Here is a calcareous soda straw in a lava tube in South Korea. The soda straw is about 7 meters in length.

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