Perfecting my final design...

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Original poster: "Adam R." <arabraxas@xxxxxxxxxxx>

Hello, this is my first time to this "forum"...well, I'm working on a 
"second version" of my coil (ie, I want to make it as professional as 
possible) and would like to make sure I am doing everything correctly.

Here are some specs: The secondary is 4"x18" (24.2mH), a .02uF cap bank, 
15-60 NST, and a Terry Filter for protection.

I have a question on the primary--I'm trying to make it high 
quality/durable and compact. What I'm trying is something that I've seen 
before and have been wanting to give it a go: a simple dual layer primary. 
It will be 1/4" OD Cu tubing ten turns, each wound in opposite directions 
(so 20 turns total, top and bottom layers). So each layer will be ABOUT 
0.0306 mH. Does this all sound right? I'm worried I might build it and find 
I need more inductance! Or am I making it overkill with two layers of TEN 
turns? Because the total width of the base is 17"x17", I need to get the 
size right (I have acrylic pieces and they are expensive... cannot mess 
up!) My coupling to the secondary is about 1".

Second question is with the rotary spark gap. I'm making a simple propeller 
gap using a cheap (ie low power) Oriental Brand motor. I'm pretty much 
sticking to what is commonly done, but what length should the rod be? 6" or 
7"? It's my intuition to go with the latter...

Any other recommedations? I'd like to get this coil working very well and 
not miss anything or screw something up.

Thanks for the help!