Dave G3YXM wrote:

. . .  Just a cautionary note about the use of plastic tubes to support LF
aerials.
Water collects inside the tube (if it is horizontal) and RF then tracks
along it and the whole thing catches fire... I know this!

A good point.  I've experienced similar problems with tubes when used as
insulators.

During a telephone conversation with Bill G0AKY, he described a similar 'trick'
to that described by Dave G3YMC.  Bill cuts his round white plastic tube (e.g.
gutter down-pipe, up to 100 mm diameter) into lengths about 30 mm long.  He then
uses heat to soften the sections into an oval shape.  I suppose the overall
result is rather like using a cable tie, but may be more UV resistant than the
common type of cable tie.

Regards to all,
Steve GW4ALG