There's a spreadsheet [Excel xls] in the Articles section of the TVW website http://www.tnvalleywoodclub.org/articles/PDFs/basic_seg_vessel_calc.xls

That's the one created many years ago for our shop-tour programs on the subject and I still use it. You can put your own data in place of the INPUT section that's there in blue -- it's just a place holder -- but don't put anything in the rest of the spreadsheet since that's where the formulas are. You can delete any rows you don't need; so for an eight ring vessel, you just need 8 rows and can delete the rest [or just ignore them].

By the way the segment length in the spreadsheet output is given in metric since it's a lot easier to set without dealing with decimal to fraction conversion. Or, you can covert the spreadsheet display to express the segment length in fractions by messing with the cell definition and converting it from 'Number' to 'Fractions' and set it to the precision you need; probably 16ths.

I believe that Doyle uses another program and maybe he'll share details on that with us.