Cheap cast nets that violate 2*pi*radius circumference formula

The circumference of a circle is 2*pi*radius, but I've noticed that many cast net manufacturers cheat on this formula to save on cost. Here's how:

Expensive part of cast net is the weights. For a cast net to open fully, you need to have a circumference of 2*pi*radius of net. But hardly anyone will notice if you make the circumference smaller than that so you use fewer weights. I realized this when I measured a net and found that the circumference was much smaller than it should be. The easiest way to check a cast net circumference is to stretch out the ring of weights in a straight line and measure. This will be 1/2 the circumference. Then measure the radius from the center to the weights. A little math gives the correct relationship between these two as 1/2 circumference = pi*radius. So the stretched out weights should be over three times as long as the radius. Here's the math:

Circumference = 2*pi*radius
so 1/2*Circumference = pi*radius
Example: radius 5', 1/2 circumference just over 15'

A net I was having trouble throwing because it had too small a circumference (so not enough weights) had a 1/2 circumference that was only 1.2 times the radius. No wonder it was so cheap, they skimped on over half the weights it should have had.

what?

the circumference is ALWAYS 2Pir. ALWAYS.

are you saying that they advertise a certain radius, and that the actual radius is smaller than the advertised radius?
i could see that happening, with the excess material forming a cone.

doesn't change the circumference of a section, but I thought cast nets were cones, not circles.

Yes, they measure the radius from center to weights. When fully open it forms a cone that is less than the advertised radius.