# RE: Question on Spirals in Columns

• To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
• Subject: RE: Question on Spirals in Columns
• From: Eric Green <egreen(--nospam--at)exponent.com>
• Date: Tue, 12 Mar 2002 10:52:42 -0800
```I never could force myself to read the entire question before giving the

Eric Green
-----Original Message-----
From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com]
Sent: Tuesday, March 12, 2002 12:43 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Question on Spirals in Columns

Eric Green gets the gold star!

The question was, could an ordinary *playing card* (not a deck of playing
cards) be slipped under the string?

The answer is a resounding, "Yes."

pi(d2-d1) = 1"

Therefore the diameter will increase ~1/3"

And in spirals, the core diameter will increase 1/3 the elongation of the

spiral.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Eric Green wrote:

. > It depends. Is your deck of cards thicker than 1/3.14159 inches?

. > Eric Green

. > -----Original Message-----
. > From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com]
. > Sent: Tuesday, March 12, 2002 10:55 AM
. > To: seaint(--nospam--at)seaint.org
. > Subject: RE: Question on Spirals in Columns

. > Glen Pappas made an excellent observation on the function of spiral
. > reinforcement.

. > As an illustration of the effect of strain on effective confinement, the

. > following puzzle is offered:

. > Assume the earth is a perfect sphere and a string is placed around the
. > sphere
. > at its equator.  If you increase the length of the string one inch (1"),

. > would you be able to slip ordinary playing cards under the string around

. > the

. > entire circumference?

. > A. Roger Turk, P.E.(Structural)
. > Tucson, Arizona

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