JT here is a rough copy of such a fan someone posted on this site I think (sorry cannot recall who). These are the proportions by which to reduce square stock to get an octagon (the 10 is the meat that remains). Simply place the square stock on the fan so that the edges of the stock meet the outer edges of the '7' fan lines, then mark the wood with the other lines. The lines should be ruled with a straight edge back towards the centre to reflect the angle of taper rquired. For some yards, not direct to the centre but to the point of transition from straight octagonal to taperered round. These then give you the guide lines to which you reduce the square stock with plane, chisel, file or....
Note: the square stock should be reduced to the appropriate thickness before starting, such that the width of the meat  ends up wide enough, that after rounding, is the correct diameter of the round - this takes a little calculation. Always better to err on 'bigger' so that you can reduce; harder to add Once you have the round, even in taper, it is relatively easy to maintain it with further sanding.
Edited by BANYAN, 10 December 2016 - 04:21 AM.