This is a technical diagram of how Samantha's tail was constructed.

(EDIT: I rewrote this description almost completely since posting this)

First, the tail is a waist hugger - held on by a tight strap around the waist (over my corset). The whole thing weighs about 5 lbs.

INNER ARMATURE:
The inner armature is on the right side of the diagram. It is drawn with the base "unbent." It is easiest to assemble everything without the U-turn bend, then bend it upon completion. The inner armature is all #9 wire and steel -- except for the belts for the waist.

The base of the armature is a rigid band of steel - a 1/8 inch thick hot rolled steel band about 2 inches wide. I used this because the base of the tail has to withstand the most torque. When finished, this band goes down from the small of my back down to the tail exit point(coccyx), then does a near U-turn and extends up about 6 inches into the tail. From that point on, two groups (spines) of number 9 wires continue further into the tail for internal support. (Because the tail has two spines instead of one, this keeps the tail from rotating unnaturally).

OUTER ARMATURE:
The outer armature is in the middle of the diagram. I cut a piece of muslin in the shape of the horizontal cross section desired for my tail. Then I designed pockets into it so that the steel band and the spines of #9 wires would slide into the pockets and provide support. The sections hashed with diagonal lines are those pockets. The four "dog-bones" are just lengths of coat hanger wire bent to that shape and attached on top of the muslin with snaps. The "dog-bones" were sized to provide width-wise support and they rest on top of the muslin and spines.

This finishes the structural parts. So next I need to attach the fur to it to make a 3 layer sandwich. I cut the tail top fur (white in my case) and bottom fur (black in my case) to match the shape of the outer armature. I need to sew these together around the edge when the whole thing is INSIDE-OUT. Think carefully. Unsnap and remove the dog-bones. I stack the 3 layers together like a sandwich with the outer armature on top, bottom fur underneath plush down, then top fur underneath that, plush up. So fur touches fur at this point. I then sew around the edge (except for the narrow tail base - leave yourself enough opening to work). Now revert the structure to right side out, slide the dog-bones inside, and snap them into place. You'll later need to hand-sew the narrow strip that makes the base of the tail, but not yet.

ASSEMBLE:
On the inner armature, the tips of the longest wires need to have a shield to slide into their pockets. I used the tips from some toy plastic swords. Anything will do as long as it is slippery and blunt and light. A bit of tape should be wrapped where the triple wires become double and where the double wires become a single wire. (This tail was made before Delrin rod was easily available)

Slide the inner armature into the outer armature pockets.

STUFFING:
Now I put some foam packing peanuts in the top half - be sure you use WHITE, SOLID styrofoam packing peanuts - Do not use modern biodegradable peanuts (which dissolve in water) or super cheap crumbly peanuts. Squeeze test a peanut - if it crumbles, it is no good.
Next I took a needle and thread and basted in a central "part" in the top half fur down the middle of the tail (I was going for a "Pepe Le Pew" look.) Then I added more peanuts until it seemed full enough.
Finally I added some peanuts to the bottom half, but not too much - gravity gives most of your shape on the bottom.

After stuffing, I hand stitched the tail base together.

The finished side view is on the left side of the diagram. Time to bend the steel band. The steel inner armature needs to be bent almost 180 degrees (at the star in the diagram) so that the tail will point up instead of straight down into the earth. The star is marked on all 3 views and parts. Also, the #9 wires in the top of the tail needed to be bent gently back for a proper curve.

BJ Staehlin and I made this tail back in 1995 and it has served me well ever since.

If you decide to build a tail like this, you will probably want to replace the shorter of the #9 wires with Delrin rod. But remember that Delrin rod will not bend to shape, unlike wire. (Delrin rod has to be heated in an oven if you want to bend it permanently.)