Installing Fuel Tanks Page 1

Started 07/05/10

There are left and right fuel tanks, so make sure that you are using the correct fuel tank for the wing you are building. The filler neck should be toward the wingtip and the fuel line attachments facing the root end of the wing. The tanks come with two fuel line connections on one end and four on the opposite end. The side with four fuel line connections faces the root end of the wing.

NOTE:  For all of the following pictures,  please keep in mind that the wing is inverted.  The top of the wing is sitting on the workbench and the bottom is facing up.

The first step is to cut a hole in the top of your wing skin for the filler neck to stick out.  It can be a little un-nerving to cut a big hole in your wing but if you will follow the steps outlined below, its no big deal.  

Start by placing your tank into the opening, (you have to sort of tilt the back edge in first to clear the spars).  Center up the tank fore and aft in the opening but with the tank offset toward the wingtip (see drawing #2) as far as you can but still leaving room to get it out.  It needs to be shifted toward the wingtip to give you room for the fuel line attachments at the root end of the tank. Now site down the back edge of the tank and get a mental picture for where that back edge lines up with the false spar at the rear. Remember that position, and remove the fuel tank.

Now, get the wife or girlfriend to bring you some lipstick that they don't want to use any more (or go buy some).  I am truely blessed to have a supportive wife who helps me out on occasion with my airplane building hobby.  Here is wife Michelle applying some lipstick to the filler neck of the fuel tank:

That's my helper, grandson Cole looking on.

With lipstick heavily coating the top of the filler neck, Cole helped me carefully lower the tank back into the hole, keeping the filler neck from touching the skin. Cole's job was to keep the filler neck from touching the skin until I was sure that the tank was properly aligned in the position that we had previously determined:

Again, make sure the tank is outboard as far as possible in the opening.

Once it was perfectly aligned, Cole gently lowered his front corner until the filler neck was touching the top skin of the wing.  I then lifted the rear of the tank to make sure the full circle of the filler neck was touching the skin.

We then picked the tank straight up and out of the opening, leaving a nice red lipstick circle on the wing skin:

Next we used a simple compass to find the middle of the circle and make a mark.  Cole then drilled a 1/8" guide hole in the exact center of the lipstick hole:

The filler neck has a 2" outside diameter, but there is some weld on it to clear so we used a 2 1/4" hole saw to cut the hole in the wing. You can see the white styrofoam through the hole:

The styrofoam was cleaned out by scraping it with a screwdriver and the vacuuming out the hole:

The fuel tank was then placed back into position and centered up:

Cole tilted the wing up so I could look at the top of the wing and check the fit of the filler neck. There was a perfect 1/8" gap all around the filler neck:

That roughness  you see around the hole is not the metal skin, its just the ragged edge of plastic that covers the skin. The metal underneath is nice and smooth.

As you can see in the picture above, the filler neck sticks out about 1/4" at this point. That's because the tank is laying right on the hat shaped skin stiffeners inside the tank bay. Once I get the steel support straps installed, it will only stick out about 1/8".  

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