Well, it's a bit later than I'd expected, RL tends to bit us all on the ... from time to time, but here's the pics of my dual-parallel-in-parallel coil (28 ga. Kanthal A-1, dual 1Ω parallel coils, wired in parallel for 0.5Ω net resistance) in my Rose V2, after little over 71mL of e-liquid, varying between thick and sweet (I'm guessing 90/10) to 50/50 (Castle Long Reserve). Vaped at between 21.7W and 23.5W.
As is obvious, the coils are a bit dark, and slightly gunked up. While they were darkish before, they weren't nearly this dark, and had next to no buildup on the coil proper. Unfortunately, as I was finishing my last tank, I wasn't paying the attention I should have and bit myself with a dry burn at 22.3W that was almost a full 8 second draw.
I was sufferin' a bit of insomnia, so when the harsh hit finally percolated through my skull, I ended up nearly hacking up a lung and started filling my Rose V2. I realized what I was doing after about a half mL, and not wanting to pour any e-liquid back into the container, I decided to see how the rayon had held up even after that harsh dry hit.
Even with the long dry burn, the flavor came back to almost completely normal after about ten draws, and the draws leading up to that were only a little "off" tasting (about like a cotton wicked coil just starting to gunk up). Visually, it's fairly obvious that the wicks held up well, as there's next to no black near the coil, except for the upper left tail. That, I believe, came from brushing against the Rose V2's chimney/juice flow control chimney when I removed it, as the inside had some blackening after the dry burn, but not much. There's very little "flaking" on the wicks, which was something that was always present with my older wicking in the Rose V2, even with rayon. When I pulled the wicks loose, they came out cleanly, leaving only a couple strands behind which were easily picked out, and the area around the coils was dark, but not blackened (further reinforcing my opinion that the upper left wick tail in the pic was darkened by rubbing against the chimney, and nothing else. I also dry burned the coil just to see how much gunk had built up, and the coils came completely clean after about 6 seconds, with little to no extraneous heat up from gunk (which I have to attribute to the dry burn).
As to the wick construction itself, I trimmed using a 'fan' style trim similar to a Kayfun build, but left about 1/4"-3/8" (a li'l under 6mm to a li'l under 9mm) of a tail, the thickness of which was about 1/16" (right at 1.5mm). I started my cut just a little past the outside top of the coil, angled with a somewhat sharply so the end of the cut is right about even with the outer area of the wick channel, which is the starting point of the tails. Despite the angled cut before the tails, e-liquid rarely seeps down into the atomization chamber, mostly, I'm sure, due to surface tension. A couple times I've dropped my mod from a few inches and it's broken the surface tension enough to allow a bit of e-liquid into the chamber, but not enough to require a "blow out" of the airflow channel. Tipping it enough to get the e-liquid within the chamber to contact the coils helps solve that, as well.
To continue my breakdown of this wick, the tails I left on the ends of the wick were then wrapped them around the base of the chimney, trying to keep them below the level of the first thread as much as possible. This seems to help flow even more than leaving the full thickness even with the wick channles, and has solved well over 90% of the "darkened juice backflow" that some people -- myself included -- have experienced in their RBA's tanks.
Hope this helps out for some, though I will warn ya it's somewhat of a pain to get the tail thickness and angle just right. It makes re-wicking take longer, too; with cotton, I could re-wick a setup like this in under 5 minutes, including teardown, removal of old wick, rewicking, filling and screwing the mod back together. Getting everything right takes me between 10 and 15 minutes now, but it's worth that little bit of extra time, IMO anyway.
At any rate, everyone, keep on vaping!
-Laters...!
kgs-wy
