I've spent 2 months or so of tweaking an older Cushcraft ATV-5 5-band
vertical with a friend's MFJ analyser and have had this thing exactly where
I want it several times now. After tightening things down and putting vinyl
electrical tape on all traps and section joints (where it seemed to make
sense) it would look fine for a few days to a week.

Then the resonant points of some bands would shift up to no-man's band
seemingly overnight and stay there. I suspected poor screw conections at
the traps, and so have been adding a stainless steel pipe-clamp connection
just above and below the trap for improved connection. Made things better I
thought - now 1-2 bands are just out of whack again.

There's always moisture inside the trap when I disassemble the thing, so I'm
wondering if maybe I shouldn't be trying to tape up the traps at all - maybe
they are retaining water or something that is affecting the capacitance.
Each trap has a drain hole at the bottom, and the aliminium pole itself has
drain holes every now and then that I'm trying not to interfere with.

Is there a trick, or some practical experience here that you can share?

I've had a lot of fun experimenting with this in any case, but winter's
coming...

Thanks,

Kevin VE9-XYZ