A Fuel Dot Makes Refueling Easy!

"A fuel dot provides a very easy way
to refuel an RC airplane that has a cowling. "

RC airplanes without cowlings are easy to refuel. You simply remove the fuel line from the carburetor. You attach your fuel pump to this piece of tubing and fill your tank. If your RC airplane has a cowling, the carburetor is not easily accessible.

Anyone who's ever had an RC airplane with a cowling knows that it would be a royal pain in the neck to have to remove the entire cowling each time for refueling. 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!

What Exactly is a Fuel Dot?

A fuel dot is really nothing more than a plug for a fuel line on your model airplane. They look just like a gas caps from the outside, making them great for scale RC airplanes.

The outter 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 outter portion of the fuel dot.

Both plastic and aluminum fuel dots are available. There are also various brands and colors, but they all accomplish the same thing.

Why Use a Fuel Dot?

I can remember my first RC airplane with a cowling very clearly. I realized that I needed a way to fuel the tank externally. So 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 (mechanical mechanism) that forces the fuel from your fuel pump into the fuel tank instead of flooding the engine. The mechanisms in this valve also prevent the fuel from leaking out, or air from entering the fueling port while the engine is running.

It didn't take long to realize that these internal mechanisms didn'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 this fueling port.

It was one of those days at the field where your overwhelming excitement to try out your new airplane is replaced with frustration and despair. One of the guys at my club suggested replacing the fueler valve with a fuel dot. So that's exactly what I did and it worked great. From then on, I installed fuel dots in all my cowled RC airplanes.

The 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. There is also a consensus amongst other flyers at my club that using fuel dots instead of fueling valves prevents a lot of frustration and headaches.

Installation

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.

"T" Coupler for Engines with Fuel Pumps

If you have a gasonline 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. Not good...

Installation with Two Clunk Lines

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 peice 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.

This is much easier than removing the tank to physically check the condition of the clunk line in order to eliminate it as the possible cause of your problems.

Installation with Single Clunk Line

Some people fear that having two clunk lines may lead to problems with the two clunks iterfearing with each other, getting tangled up, etc. While I've never had this problem, it is a legitamate concern.

If you only want to have one clunk, all you have to do is bend your copper tubing from the fueling line to the bottom of the tank. Since your RC airplane is sitting upright when you remove the fuel, you should have no problem getting all the RC airplane fuel from the tank at the end of the day.

Important Tip

When brand new, there is a very tight fit between the plug and the outer portion of the fuel dot. Some times it is necessary to lubricate the O-ring with oil or vaseline in order to slide it in. But whatever you do, do NOT enlarge the hole in the outer portion. Doing so will cause the plug to continuousy fall out of place. Then you have to buy a new one...

Where to Buy Them?

Most local hobby stores carry at least one type of fuel dot. You will more than likely find a wider selection on eBay also. 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.