Look in alt.binaries.pictures. woodworking for "Arc calculator - Arc height calculation.sxc".
It's a spreadsheet I did for the freeware Open Office suite's Calc spreadsheet program. You can download that Sun Corporation freebie ( a direct alternative to Microsoft Office, it also reads their files, with some exceptions due to different formatting and so on) here if you like:
I divided the half chord into ten parts, but can also redo that if more are needed. This does the calculation knowing the chord half-length, and the height from chord to arc at its center. Calculations are for other heights along the chord to get points on the arc. Just the half is needed for a template, or to transfer directly.
Enjoy!
Bill.