[R] French Curve

[Marc Schwartz]

On Fri, 2005-04-01 at 20:07 +0100, Ted.Harding at nessie.mcc.ac.uk wrote:

<snip>

> I still have some, from the 1950s ... The curves in the edges
> are supposed to be segments of logarithmic spirals (which
> ensures a kind of self-similarity on different scales).
> A nice picture is at
> 
> http://missourifamilies.org/learningopps/
> learnmaterial/tools/frenchcurves.htm
> 
> Splines, in the drawing-office sense, were long narrow
> (about 1/4 inch wide) strips of thin springy metal with,
> along their length, little flanges at right-angles to the
> plane of the strip. Each little flange had a hole in it.
> 
> The principle was that you would pinthe flanges to the
> drawing-board at chosen points by pushing drawing-pins
> through the holes. The metal strip then stood up at a
> right-angle to the paper.
> 
> The flanges were attached in such a way that you could
> slide them along the metal strip. (Or you could use a
> strip without flanges, and special pins which raised
> little pillars up from the paper, against which the
> spline would press.)
> 
> The end result was that the metal strip then defined
> a curve on the paper, and you could run a pencil along
> it and draw a curve on the paper (taking care not to
> press too hard against the metal, to avoid deforming
> the curve).
> 
> By virtue of the laws of elasticity, the curve delineated
> by the metal strip had a continuous second derivative, i.e.
> what modern kids call a second-derivative-continuous
> piecewise cubic spline.
> 
> We have not moved on.
> 
> Happy whatever it is to all,
> Ted.

Ted,

That sounds like the flexible curves that I found earlier, while
Googling for an example of a French Curve and found the Mathworld link:

http://www.artsupply.com/alvin/curves.htm

and

http://www.reuels.com/reuels/product21021.html

Marc