Jean-Cristoph von Oertzen (Germany) is a traditional archer (traditional being defined by him as an archer who uses simple wooden bows without stabilizers, target devices, or pulley system) who runs a blog about archery in the German language. Jean-Cristoph von Oertzen wrote a script to calculate the real, static spin values ​​for a wooden arrow and put that calculator on his blog.

That script, along with the rest of his blog, became so popular among traditional archers that he wanted to create an iPhone application from that script. That iPhone application is called SpineCalc.

SpineCalc - iOS (iPhone, iPad)