So what's a fuel dot and why would you need one?
RC airplanes without cowlings are easy to refuel. Simply remove the fuel line from the carburetor, attach your fuel pump and fill your tank. Piece of cake right?
As you probably know, RC planes with cowlings covering the engine are a completely different story.
Anyone who's ever had an RC airplane with a cowling knows that it's a royal pain in the neck to remove the entire cowling each time you refuel.
A method of filling the tank without removing the cowling is absolutely a necessity. Well...unless you just enjoy removing and installing your cowling several times a day!
The outer piece slips through a pre-drilled hole in the airplane engine cowling and is held in place by a nut. The inner plug has a solid nipple that plugs the fuel tubing.
This inner plug has an O-ring around it that holds it snug with the outer portion.
Both plastic and aluminum ones are available. There are also various brands and colors, but they all accomplish the same thing.
I can remember my first RC airplane with a cowling very clearly. It didn't take very long to realize that I needed a way to fuel the tank externally. I did what seemed like the logical thing to do and bought a fueling valve.
A fueling valve is installed in the fuel line between the carburetor and the fuel tank. It has an internal check valve that forces the fuel from your fuel pump into the fuel tank instead of flooding the engine.
The check valve is also supposed to prevent the fuel from leaking out, or air from entering the fueling port while the engine is running.
It was my experience that these check valves don't work worth a darn! I had dead stick landings after dead stick landings because this valve was not sealing the fueling port correctly.
On top of that, I wasted a ton of fuel as it just seeped out the fueling port.
One of the guys at my club suggested replacing the fueling valve with a fuel dot. So that's exactly what I did and it worked great. From then on, I've installed fuel dots in all my cowled RC airplanes.
A fuel dot is an extremely cheap and easy solution. I'm not saying that all fueling valves are bad, it's just been my experience that fuel dots are so much easier to deal it.
There are a couple different ways of installing them. Unless you have a gasoline engine you are going to have to install a third fuel line.
If you have a gasoline engine (or a rare glow engine with a fuel pump), you can simply use a "T" coupler to install the fueling line in between the carburetor and fuel tank.
The internal mechanics of a glow engine pulls fuel into the carburetor and does not require a fuel pump. This means the path from the fuel line into the carburetor is wide open. If you simply install a "T" coupler , you will flood the carburetor while filling the tank. You can't use a "T" coupler with a glow engine....
If you have a glow engine, you'll have to install a third line to the tank. This is easy because most tank plugs have a third hole, it just isn't all the way through.
So the first step is to go ahead and punch this hole all the way through. You can simply push a piece of metal tubing through the stopper to open it up.
You now have to decide if you want two clunk lines, or one clunk line. This is purely a personal choice.
I personally prefer having two clunk lines. This makes it easy to remove the fuel from the tank. It also comes in very handy when trouble shooting your engine. If you suspect that the fuel suction line is the cause of your engine problems, you can simply switch the fueling line with the carburetor line to see if your engine problems go away.
Some people fear that having two clunk lines may lead to problems with the two clunks interfering with each other, getting tangled up, etc.
While I've never had this problem, it is a legitimate concern.
Most local hobby stores carry at least one type of fuel dot.
You will more than likely find a wider selection on eBay. Below is what it listed on eBay right now. If you don't have an account, no problem. Just click the banner below and take a couple seconds to register before placing an order.