Matt, Here's what I've learned that works for me. I am NOT the expert, but I've been having some really good luck with my coils, so here goes.
I use about two or two and a half inches of wire per coil. I also use about two inches of wicking material for each coil, but I'm using cotton instead of silica. After I wrap the coil, then I end up cutting some of the wicking material off. Since I'm using cotton threads and/or yarns that I buy at Walmart or Michael's, it's super, super cheap and I never worry about waste or trying to conserve it.
If you decide to get a rebuildable and try your hand at wrapping coils (easy peasy), PM me and I'll send you a package of samples of all the cotton/bamboo wicking materials I've accumulated in my search for the "perfect" wick.
The wire I use is 32 AWG Kanthal. Rob has 28 gauge, 30 gauge, and 32 gauge on his site. There's a chart that is very informative about the resistance of the wire and the actual size if it at Resistance Wire (ohms/in). Here's the gist of it. The smaller the number, the "thicker" the wire, and the lower the resistence. So, for instance, an inch of the 28 gauge wire would give you a resistence of about .5 ohms, whereas an inch of the 32 gauge wire will give you about 1.4 ohms. We usually don't talk in inches, we talk in "wraps" around the wicking material, but it really has to do with how much wire you have between the two posts in your atty. I use about 4 - 5 wraps of 32 gauge Kanthal wire around my wicking material and between the pos. and neg. posts, which translates to roughly an inch of wire or so. I usually get a coil that meters in at about 1.5 ohms....perfect for my tastes. If I wanted higher ohms, I'd either go to a smaller wire (like 34 or 36 gauge kanthal....which I've never seen around these parts) and still use the 4 - 5 wraps, OR I'd go to a fatter wire like 28 gauge Kanthal and do more wraps. That's how that works.
I have my "sweet spot" which is a 1.5 ohm coil on either my REO Grand at 3.7 - 4.1 volts, or on my VV Grand. On the VV Grand, I still keep my volts set at around 4.1-4.3 volts. The vape is the same. The big difference is that the VV Grand will hold at that voltage longer than the REO Grand because it's regulated. The REO Grand battery will gradually go down with use until it's time to recharge.
There are some pretty good videos around showing how to wrap coils.
Hope this is not too much information..
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