Mast tapering jigs:

Tapered Mast ("A" taper, like a candle.)

Older sailing vessels

(Taper: to become progressively smaller toward one end,
 to diminish gradually, usually with even increments along the length of the taper.)

You don't have to glue the paper in. You can just 'form' it into the shape of the mold.

A hardwood is best suited for the mold.

This method works well for Spars also! Just work from the center out to the ends.

Before you know, you'll have an entire collection of jigs.

I use a grid type of sand paper- lasts longer. If you have to replace the paper,

Just refile the rounded out area again (carefully!)

"Conical" shaped mast, which at the same time, tapers along it's length.

Modern sailing vessels

Conical:

1 : a plane curve, line, pair of intersecting lines,

 or point that is the intersection of or bounds the

intersection of a plane and a cone with two napes
2 : a curve generated by a point which always moves

 so that the ratio of its distance from a fixed point to

its distance from a fixed line is constant)

The same type of jig will work for conical masts too.

The only difference is you can't use a drill. Just make two molds, one for each side,

 and draw along the length like a plane. Then finish off by hand.