stick & rudder

flight advisor

Fine-Tune Fueling Build and calibrate a fuel dipstick to sharpen your fuel savvy Ken Scott & Steve Mahoney

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ow much fuel is there in that tank—really? It was winter and the rain lashed at my hangar doors. No

flying today, so I decided to empty my wing tanks and repair the leaky quick drains I’d tolerated all summer. I peered through the filler

neck and saw that the fuel was level with the rear outboard corner of the tank. I’d always known (although how I knew, I can’t re-

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The printed scale is saturated with epoxy resin in preparation for bonding to the tube. 98

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Sharing information is the ultimate goal of this department in EAA Sport Aviation. Whether you’re a new or experienced builder/restorer, or a Flight Advisor, on these pages we want to know how the team of an FA and builder met a particular challenge. You can submit a fully written story, or just the “who, what, when, where, and why,” and we’ll have a staffer contact you for the rest of the details. Please don’t forget pictures, because they often tell a story better than words. E-mail your FA success stories to editorial@eaa. org, with FA as the subject.

member) that it took between 7 and 8 gallons to fill the tank to this point. So I got a couple of 5-gallon gas cans and started to drain the left tank. The first can was threequarters full when the tank ran dry. What I thought was 8 gallons was only about 4. Well, the NTSB accident databases are full of cases where pilots simply failed to accurately determine how much fuel they had on board before they departed. Fuel gauges can be inaccurate or unreliable, so taking an accurate fuel measurement during preflight is one of the easiest ways to avoid disaster. A simple dipstick is the obvious answer—but even something this simple has pitfalls. A sheen of fuel on a wood stick, for instance, can be hard to see and will vanish before your eyes. Avgas evaporates quickly once exposed to the air outside the tank. Here’s a way to

The saturated paper scale is fitted to the tube. The wax paper will keep the resin from sticking to the table.

build a dipstick that’s easy to read and puts the fuel back in the tank when you’re done. It’s cheap, simple, and easy to explain.

None of which can be said for running out of gas. Here are the materials and equipment you will need:

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flight advisor Q One-fourth-inch outside diameter, 1/8-inch inside diameter clear acrylic tube at least 6 inches longer than the distance from the filler neck to the bottom of the tank. I got mine from TAP Plastics, a local chain specializing in fiberglass and plastics. Q Epoxy resin. I used West Systems type 105 with 206 hardener. QA computer and laser printer. QHobby razor knife. Q Abrasive paper, wax paper, and urethane foam rubber packing material.

Step 1 Measure the fuel in the tank. Some might prefer to start at the zero usable fuel level, which is fine if you really know where that is. But a truly empty tank is better because there’s no wondering. With the tanks empty and the aircraft parked on level ground, add 1 gallon at a time. (The fuel dispensing equipment found at most general aviation airports is periodically calibrated, so it is usually accurate.) Mark each increment on a temporary wooden dipstick.

A scrap of firm shipping foam, a small board and a clamp force the scale around the back side of the tube. for these steps. Q Click on Table in the top menu and choose Insert Table. Q Create a table of one column

inch, says Ms. Pope, my junior high geometry teacher.) Q Click on Table, choose Select Table, and slide the cell divi-

Step 2 Plot the measurements to smooth and interpolate the data. Transfer the fuel level measurements from the stick and plot them on a computer using a graphing program such as Microsoft Excel. Viewing the data in a graphical format will allow you to view the cross section of your fuel tank, and it will be obvious whether any erroneous data points exist. This plot will also provide a method to interpolate the location of incremental tick marks used to label the stick. At this point you may want to retake the measurements or make some small adjustments to the data to create a smooth plotted curve.

Step 3 Create the scale and draw the scale decal. I used Microsoft Word 100

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The dipstick in action. Note the magnification effect of the liquid fuel trapped in the tube. and the appropriate number of rows—the number of levels you measured when you filled your tank, plus two. Q Use the sliding bar at the top to make the column half of the circumference of the 1/4-inch diameter tube. (Approximately 0.39

sions with the cursor to match the measurements on your plot. The toolbars on the left side show the dimensions. It helps to use a 300 percent or larger scale. Q Label the bars with amounts. You can type right in the cells, then click on Format and choose

any rough edges with a razor knife or abrasive paper. Be careful not to scratch the front optical surface. You may wish to add one more coat of epoxy to finish off the edges.

straight up and down. If you can’t judge that, take several readings and use the lowest one. Lift the tube from the tank and read the top of the fuel column trapped inside. The fuel in the stick will optically magnify the numbers on the scale, making them easy to read. When you know how much fuel you have, lift your thumb and watch the fuel go back in the tank. You can now fly two seconds longer.

Step 6 Dip and read. Just like chemistry class. Dip the tube in the tank until the bottom touches the bottom of the tank. Cover the top with your thumb, pressing hard enough to create an airtight seal. Hold the stick Of course, you can skip all this work and buy one already made, but where’s the fun in that?

Text Direction to make the text vertical. Q Print it on ordinary white paper using a laser jet printer. This should closely match the marks on your original measurement stick. (In fact, if you want to skip the computer refinements, you may use the dimensions directly off the dipstick and achieve acceptable accuracy.) You may want to add other information such as usable fuel, left tank, or identification such as the N number.

1928 Stearman C-3B, restored by Poly-Fiber

Step 4 Bond the decal to the tube. Mask half the diameter of the tube with tape to avoid scratching it. This will become the optical side that serves as a magnifying glass. Lightly sand the exposed side of the acrylic tube with fine abrasive paper to create a suitable bonding surface for the decal. Use scissors to cut the paper decal to size, and then totally saturate it with epoxy. Place and align the decal on the sanded side of the tube. To make the paper conform to the round tube, clamp it in a sheet of foam rubber separated by a wax paper.

Step 5 Sand and finish your work. After the epoxy has cured, remove the dipstick from the wax paper and clean up

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800-362-3490 Call for a free info pack!

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