sec coils/ 8" or 4"???

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Original poster: "J Dow by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jdowphotography-at-hotmail-dot-com>

Hello all!

I’m about to wind my two sec coils for a bipolar coil. I’m going to power 
the coil with 4 MOT’s like the ones we saw Tim use (go Tim!). I figure on 
having 5KW available to the coils. There will be only one primary with 15 
turns. The cap is a Geek MMC 69.2uf.
Here is the big Question.
I don’t know if I want to wind 8” coils, or if 4” will do just as well (best 
spark length in mind)
I don’t have 8” PVC so I made open coil forms. The forms are made with 16 
wood dowels set in two end caps.  There is a middle section to keep the 
dowels from bending in. there is a piece of wood in the center of the forms 
to prevent the forms from twisting. It is has been heavily coated with 
polyurethane and before winding I plan to wrap them in polethiline plastic 
like the kind we all use in home rolled caps.
So its ether this or use 4” thin wall PVC.
I think the 8” would give better sparks but I’m afraid they wont last.
I know the 4” PVC will last and is cheep but I’m not confident the sparks 
will be long.
I think I’m sway ing toward not using the open forms I made and just going 
with the PVC.
What say you all?
Read you later
Josh