Looking back some 4 years, the word was the Baker Island expedition would not be repeated for some 15 years.  I'd better get some going again in way of a HF antenna for my long unused station.  Ingredients were mostly what was on hooks in the garage.  Wire was "found" multi conductor ex telephone pvc jacket line.  Center and segment insulators are 3/4 Schedule 40 PVC with length set by TLAR analysis.  That Looks About Right.  Make that 4 to 5 inches.  Pieces were pilot drilled 1/8 inch.  End holes opened to 1/4 inch plus a center hole for the center insulator of 5/16 inch to pass RG8X. 

How this is set up:  For a given band, the insulator segments inboard of that point are bridged with the antenna wire.  Closing and opening the bridges is by Faston push together terminals.  This took 2 boxes of terminals from Lowes Home Improvement Center.  Cost of that was about $10.  Only cost to build antenna system for 40, 30, 20, 17, 15, 12 and 10 Meters.  

Since this example was insulated wire both in terms of overall jacket and individual wire insulation, resonant length was less than formula value.  Working with your antenna analyzer, first prune length of innermost segment to give 10M resonance.  I worked on basis of nulling reactance.  Could be off resonance a bit because of feedline properties.  But this is close enough.  Based on what you find, there is a scaling factor to applied for segments working outward and to lower frequency bands.  Still start a bit on the long side.  Then prune for desired resonance.  Result is a true center fed dipole for each band used.  By means of a lanyard, I drop one end, change Faston brides to change bands, and go back to operating.  Not a setup for cold inclement weather.  But great to just get going, portable operation, Field Day or what have you.

What the center insulator installation looks like:  Yes not balanced feed.  But things happen.

Detail of a pair of segment insulators.  One on left shows open.  End of one side of antenna for 15M operation.  Element to right would be end of 12M segment, but here is continuation of antenna.

What the series of segments for one side of antenna looks like.  As lowered to ground for picture.