Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx> Hi Rich,I think we need more details. What do you mean by C/D caps at 30 (qty or nf)?? 9inch dia tube sounds OK, silver plated wire probably isnt necessary (OK if you already have it, but I wouldn't pay a premium for it).
Being a static gap, shoot for a Cp of 49 nf. Your transformer is mains resonant at 30 nf and this value should be avoided unless you have experience at resonant charging. The secondary should have a winding height of around 40 inches given a 9 inch dia. The wire guage should be chosen to give you around 1400 turns with this winding height.
Gerry R
Original poster: "Rich" <rdjmgmt@xxxxxxxxxx>I want to build my 2nd coil this year and I have a question on the secondary diameter.Power will be 13Kv 150ma transformer , RQ spark gap, MMC of C/D caps at 30.My secondary can be a 9" dia mailing tube and 20ga silver plated stranded wire with thin insulation or6" PVC with 24ga mag wire. Any pros or cons on the secondary Rich