M. Bruno wrote:

. . . .   I discovered that plywood is not a good insulator,
expecially
after a rainy weekend and with 21 kV on it .... :(((

Now, IK1ODO QRT.

But QRV again soon, we hope!

I  had the same 'learning experience' with my wooden coil former (2  x
400 mm diameter plywood ends;  7  x  1000 mm length broom handles
between).   It was working fine during my first QSO with Finbar, EI0CF
---  until it started to rain!  The coil flashed-over to the wooden
former with sufficient energy to ignite the coil former.  So, now I wrap
the loading coil with a green plastic tarpaulin (available from hardware
stores), and use a 'gardening bag', made of the same plastic material,
to act a 'hat' for the top of the coil.

Regards to all,
Steve GW4ALG