I'll help you....RDA's are going to get hot. there is a lot of heat in a little chamber and without enough airflow they get super hot super fast. and even with good airflow they can still get super warm if you chain vape it and it gets worse if you let your wick get too dry and scorch it.
if this is really your first build you need to do three things...find out what battery you have, get an ohms checker, and get a higher gauge wire like 28 to start with. No offense...but 20 gauge wire is a dangerous thing in the hands of the wrong person.....the answer to your question....8 wraps of 28 gauge kanthal around a 2.5 mm drill bit will be aprox. 0.65ish. I understand you want to blow big clouds and even vape shops are pushing out pre build coils on RDA's with twisted 24 gauge and such but try a few safe builds and know your amp limits. Especially when you get down below .3....below .3 a difference of .01 can make your amps jump high fast and most of the popular IMR batteries still easily available have a continuous drain rate of 20 amps which max's you out at .2 and that's pushing it's limit when it's fully charged. i have a friend who almost blew his hand off because a vape shop built him a .4 ohm build on his first atty he bought and then sold him a battery with a 5 amp limit and told him he was fine...it wasn't till he asked me why his mod was getting hot that I found out. Luckily I was able to give him the right batteries and a spare charger before something bad happened but I can't stress the importance of safety enough. Hope this helps
