1. Flying bobo,

I think I am responsible for some your confusion.
I think I jacked up the spreadsheet when I was tring to figure out why the spreadsheet was adding an extra 2 inches to the innerface lenth and width in addition to the seam allowance. That 14b cell is suppose to be yellow( a function cell) like the length cell 15b below it, but now seems hardcoded for 42.

I PM'd the OP but haven't heard back. The Spread sheet isn't locked and I guess I proved the problem with that.
Someone mentioned the ability to roll back the sheet, but I can't for the life of me figured out how to do that.
I beg forgiveness from the forum for my sins.
I did find out that you can exort the spreadsheet to your computer an an excel file, so if it does get fixed, I promise to keep my paws off it.
Very sorry to all,
Jason

2. I am pretty sure that B14 is supposed to be "=B10" so I set it that way... OR =B14+2, so you have enough to make an end-channel...

3. Originally Posted by JohnSawyer
I am pretty sure that B14 is supposed to be "=B10" so I set it that way...
Bingo

For future reference, here are the original formulas (formulae?) in case it gets out of whack again:
[Col, Row] Calculation

[B14] =B10
[D14] =B14+(B12*2)
[B15] =B11
[D15] =B11+(B13*2)
[B16] =(B14*360/170/PI()+2*B9)*PI()*170/360+2*B9
[D16] =B16+(B12*2)
[B17] =B11+(B9*2)
[D17] =B11+(B9*2)+(B13*2)
[B18] =B14/B8
[B19] =(B16-(2*B9))/B8
[B20] =B18+B9
[B21] =B19+B9

[B27] =(B9*(B18+B19)/2*B11)
[B28] =B27*B8
[B29] =B27/B25+B27/B25*B26
[B30] =B28/B25+B28/B25*B26