If there is no pattern as a basis for determining the correct spoke length, the only way to calculate it is to use the formula. For the hobbyists among us who have not received the blessings of higher mathematics, this is not so easy to see through. During my research on the Internet I found an address with a page for calculating the spoke length, where only a few easy-to-determine data have to be entered and the correct spoke length is given. Maybe this page will help you too. To find under www.kreuzotter.de
Spoke length calculation page. Many thanks to Ralf Raub for the information!!