# Learn how to make an informed purchase.



## Alex (8/6/15)

Jumping into RDAs? Learn how to make an informed purchase. [PSA] (self.electronic_cigarette)

submitted 6 hours ago * by LucRSVVulcan Vector RDA, Product X

There are a lot of posts regarding "what kind of RDA should I get?", so, I'd like to try and help ease the process by demonstrating how a vaper should go about selecting, vetting, and eliminating options for their purchases. This applies for other hardware as well, but, RDAs/RTAs seem to be the most requested.

*Identify what your purposes are.*

Ok, you want to buy a new RDA, what role does this atty fulfill? Things to consider are:


Size
Airflow
Single/Dual Coil
Post Set-up
Let's examine what each of these affect.

*Size*

When you make an atty smaller, you reduce the distance vapor has to travel. This greatly impacts the heat and density of the vapor. If you want a hot vape without pumping a high wattage (for instance, if you're using a mech mod), then you want to be looking at smaller attys. On the other end of the spectrum, if you want a cool, airy vape, a larger atty with more room for the vapor to travel will help you achieve this, along with...

*Airflow*

_This topic gets really long, so sit tight._

The more airflow an atty has, the more air is traveling over/across a coil and drawing the vapor to your mouth. Airflow will affect vapor density as well as cloud size, flavor strength, and heat. If you're a mouth-to-lung hitter, you want to be looking for a small-airflow RDA like the Magma. If you're trying to blow clouds, you want a lot of airflow, in order to draw as much vapor as possible.

Another factor regarding airflow is the orientation of the airflow. Different styles achieve different things.


*Side Airflow* this is the most common airflow configuration that you'll find. The air travels in from the side, hits the coil horizontally, and then travels up to the drip tip and into your mouth. This airflow configuration is tried and true, and is easy to work with as aligning the airflow is as easy as making sure your coils are symmetrical (assuming a dual coil build).
*Bottom Airflow* This airflow configuration is heralded by many flavor chasers because the vapor travels directly from the coil to the drip tip without much redirection. Bottom airflow RDAs will generally deliver powerful flavor without the need for crazy builds, however, they are trickier to build on and extremely prone to leaking.
*Top Airflow* Top airflow RDAs are relatively new and much like bottom airflow RDAs are heralded for their flavor production, as well as being generally leak-free as there's no holes for the liquid to escape from. These can be a bit tricky to build on in terms of aligning the airflow holes with the coils and spacing them far enough/close enough to the airflow intakes to properly work.
*Single/Dual Coil*

A lot of vapers prefer single-coil. Why? Well, when you build dual coil, you're delivering 50% of your power to each coil. That is to say, if you are using a regulated device at 100 watts, there are 50 watts going to each coil. With a single coil, you send 100 watts to 1 coil. Why is this important?

Say you have an IPV2, which maxes out at 50 watts. You want a nice warm vape, and when you build a dual coil on your derringer, you get an airy vape that takes a long time to heat up (AKA "ramp up time"). If you were to build a single coil on the derringer, and run the IPV at 50 watts, you're going to cut down the ramp up time and allow for a hotter, more dense vape. A lot of people like single coils for this and other reasons, and it's something to take into consideration when buying an atty. Does the device you have give you enough power to enjoyably run dual coils?

*Post Set-up*

Ok, last topic, we're almost there! Post set up is going to affect how easy an atty is to build. Generally we see three types of post design (although there are more, those are niches). The post arrangements we see usually are:


*Three post* This is the most common post arrangement. You have 1 positive post in the center, and two negative posts on the sides. This makes building dual coils easy enough, although it takes a little work to get them centered (centering is where your coil's "center" aligns with the center post). Three post designs can get cramped when working with thicker wires, and can restrict the kind of coil you plan on building.
*Four Post* The four post arrangement is similar to the three post, however, a four post design splits the positive so that there are two spots for your coil's leads. This makes building with thicker wires and keeping everything neat and short-free much easier. Four post designs are quickly becoming a standard in the RDA scene.
*Two Post* This is the least seen arrangement of the three listed here, but still certainly popular. A two post design has only one positive and one negative. The benefit of this is that you can center your builds VERY easily. You usually see post arrangements like this on bottom airflow RDAs where aligning your coils with the airflow is very important. Building on two post designs is called tricky by some, a snap by others.
Why does this matter?

What are you planning to accomplish? If you're looking for high-surface area, cloud pushing builds, you're going to have a much easier time building on a four-post design. You won't have to fiddle with your leads, and should one of your coils not work as well as another, it's penalty-free to remove just the one coil and replace it.

Great! We've gone over RDAs. What's next?

Peripherals. If you already have them, great, but as this post is for everyone, lets talk about the other things you'll need.

*Wire*

Wire is gonna be your biggest thing in terms of effecting vapor. There are a couple things to know about wire sizes and how they perform.

*Gauge*

Wire gauge (often written as "awg" or "g") is rated in number, where the lower the number the thicker the wire. That is to say, if you have a strand of 28 gauge wire, and a strand of 24 gauge wire, the 24 gauge will be thicker. The thicker a wire is, the lower its resistance/inch is.

*Coil Mass*

You want a hot vape? You won't want to wait two years for your wire to heat up, right? Coil mass is the thing to consider here (along with resistance). If you have two coils at .3 ohms and one is 24awg, the other 28awg, the thinner wire will have less mass. The reason for this is simple: the thinner wire has a higher resistance, and thus takes less wraps to reach the target resistance. The wire will heat up faster, at the expense of surface area, which is important for the volume of vapor you create. The more coil mass you have, the more power you will need to throw at it to heat up the wire. This means building lower resistance on a mechanical mod, or just increasing the wattage on a regulated mod.

*Wire Composition*

Aside from gauges, you also have different materials for wrapping coils. The two standards you will see for regular devices are Kanthal A/1 and Nichrome (N80) wire. There isn't too much difference between the two of these, however, some people note a metallic taste with nichrome wire.

For temperature control devices like the IPV4, DNA40d, and SX mini M class, you have two wire choices for use:

Nickel, and Titanium. Both have very low resting resistance which will increase with heat, allowing the devices to gauge what the temperature of the coil is by comparing the hot resistance to the resting resistance. Titanium is a good alternative for people who are allergic to nickel, but, be aware of the fire hazard titanium wire poses.

*Cotton*

Cotton is your wick. It doesn't actually have to be cotton. You could use Rayon, or Hemp wick, or silica. There are a lot of different wicking materials out there. The top recommendations from ecr right now are:


*Japanese Cotton* This is easy to work with because it comes in neat little pads. You simply cut a strip and pull it through your coil. Japanese cotton seems to wick faster than your standard cotton ball, and many say it has less if any cotton taste after you first wick your build.


*Rayon* Rayon is a synthetic cotton which is great if you have cotton allergies. It has no cotton taste, and is cheap as hell.

*Ohm Meter*

If you don't have a regulated mod with a built-in ohm reader, this is important. You don't want to throw a .02 ohm build on a mech if you had intended to build at .4 ohms. You want an ohm reader to be sure you don't have any shorting, and you're within your safe limits. They're cheap, and well worth it. If you have a multimeter at home you can also use that.

*A quick note on safe building and use of RDAs*

So, you're a total noob. You know what kind of RDA you want, you've got yourself a spool of 24awg wire, an ohm reader, some 25r batteries, and your trusty screwdriver(s). But, how do you know you're building safely?

Well, there's a couple things to know here.


What is your build's resistance? Check with your ohm meter/multimeter to make sure you are within the safe discharge limit for your batteries. On ECR, we tend to recommend VTC4s, 25Rs, HE2s, and HE4s because they have higher pulse discharge ratings.


What is your battery's discharge rating? You can either look up your specific spec sheet, or use www.steam-engine.org to have the robot check for you.

Once everything is in the clear, you are ready to vape. Throw that atty on a mod and let 'er rip!



*Author's Note* I'm sure there's stuff I missed. If you see glaring errors or things which should be added, please feel free to tell me. Have a nice day everyone! 

*Useful Links*

*Coil resistance calculator, battery safety* - www.steam-engine.org

*Detailed guide regarding coil resistance & safety* - youtube video

source: http://www.reddit.com/r/electronic_...ping_into_rdas_learn_how_to_make_an_informed/

Reactions: Like 1 | Winner 5 | Informative 9


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## Smoke187 (8/6/15)

Very informative post, this will definitely help the noobs when choosing an RDA, myself included

Reactions: Agree 1


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## Brendz (8/6/15)

Top notch information here! Great post

Reactions: Agree 1


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