Shane,
A long time ago DC Cox gave me some advice on a 12/30 design.
on a 4" PVC pipe, 1680 turns of #30 (around 20") was his design, so there is precedent for using a 4" pipe with a 12/30
He also used 14 942c20P15K-F caps in series for 0.017 @ 28KV as the tank cap.
Now, in my experience , a 3" PVC will do you just fine for a 12/30, At the lower power levels i find that a smaller OD and slightly taller secondary makes the sparks looks a little more impressive, but that's just me.
If you had 2 or 3 more transformers laying around, then that would be a good reason to make a bigger secondary, as you could reuse it with later coils. Granted I think I was pulling 45" arcs off of my 3" secondary at one point.
As for your coating, if you want to make it absolutely bullet proof, and are willing to make a decent jig to spin it at a constant and adjustable speed over night and spend the time to get it right. Envirotek lite epoxy, is what I started using a few years back. I will never go back to varnish. But otherwise, the basic spar varnish (clear gloss) was what I was using before I discovered the epoxy.
cheers,
John "Jay" Howson IV
"Why thank you, I will be happy to take those electrons off your hands."
----- Original Message -----
From: "shane bounds" <57ovalbug@xxxxxxxxx>
To: Tesla@xxxxxxxxxx
Sent: Tuesday, December 31, 2013 5:30:54 PM
Subject: [TCML] Secondary choices
Hello all, I've been working on a Tesla coil using a 12/30 transformer. I
built a secondary using a 3.25"pipe, #24 wire and a 5.5:1 ratio but don't
care for the shellac I used to coat it so was considering winding a new
one, after reading many post on here I'm wondering if i would be better of
using a 4" pipe, #26 wire with a 5:1 ratio.
Thanks
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