Category Archives: Fuel Tanks

Time: 5 Hours

Today I set out to get at least one fuel tank attach points done. There are seven z shaped brackets that hold the fuel tank to the main spar. It seems like a general consensus that there is a better way to attach all the parts than what Van’s describes in the plans. The method was known as the “Checkoway” method after a builder that documented it. He has recently come out and asked that the credit be given to the builder that he learned it from and developed it, Steve Hurlbut. I started out by marking seven left and right brackets.

I then marked the center on one flange of each bracket. Van’s wants you to mark the hole dead center of the flange both length and width. Six of the brackets will have nut plates attached to them for the bolts to come up through the main spar web and attach to them. One bracket, the inboard one, will have the bolts go through them down through the main spar web to nut plates that are attached to the main spar. I followed other builders that shifted the center line on the inboard bracket away from the bracket web by 1/16″. This allows the head of the bolt to move away from the bracket web and allow a socket to go over the bolt. The other six brackets have the centerline moved towards the bracket web. These ones don’t have the need for a socket since the bolt comes up through the main spar and into a nut plate. This shift of the center line allows for a little more room on the opposite flange where these brackets will be blind riveted to the fuel tank baffle. Builders usually have to grind down the head of a blind rivet puller tool, this shift reduces the amount of grinding needed. After making all the marks on the flanges I set up the drill press and hit the inboard brackets for the left and right.

I then adjusted the drill for the different holes, here you can see the two different centers.

Hitting all the center holes didn’t take too long once I had the drill press setup.

The next step is to bolt the brackets to the main spar and square them up. You need to make sure you have the orientation correct for all seven brackets per the plans.

With all the brackets bolted and square to the main spar you can drill the other holes by match drilling up through the spar web and attach bolts to those holes.

Now all the brackets are bolted and square you can place the tank back on the spar. Once you have the tank in place you need to make all the seams tight between the leading edge and the tank and the tank skin and the top skin. I used two ratchet straps with a couple rags to get the fit nice and tight, I used a couple pieces of wood to give the straps to bind against at the rear spar so it wouldn’t bend the aft end of the top skin.

All the joint were nice and tight and looked great. The next step is to match drill the the skin splice between the outboard leading edge skin and the tank skin. These need a #19 drill bit for the AN509-8R8 screws that will go here.

Next up is to drill the five inboard holes through the baffle and the inboard z bracket.

With those holes clekoed you move to the other end. To get access to that end you need to remove the outboard leading edge.

Now that you have both ends of the baffle/end ribs attached to the z brackets you can remove the skin and center ribs as a unit leaving the baffle and the outboard/inboard ribs.

What this does is give you access to the baffle holes that you can now use to match drill the z brackets that are below it. So I drilled and attached the baffle to the brackets with the help of my beautiful girlfriend Tricia. I love that she wants to be so involved with the build and can’t wait to fly with me and take some really cool trips! Thanks T!

With those done I removed all the cleckos and replaced the skin/rib assembly. I could then remove the tank leaving the drilled z brackets behind with the spar.

This method ensures that all the attach point are good but also are all inline for a tight fit of the tank to the wing and other leading edge. It was a long day and I decided to clean up the shop and put the tools away for the night. I will repeat the whole process for the right wing next.

Time: 3 Hours

The right tank ribs went into the skin a little easier than the left ones did. I noticed that the right tank skin was not compressed as much which probably accounted for the easier rib installation.

I was able to use the cradle on this side which makes the whole process easier as it holds all the parts in the right place. Hopefully the left tank skin will hold the shape after being together which will help down the road, we will see. I grabbed the tank baffle (I did this on the left tank as well) and put it in place.

I placed the tank on the spar and it matched up as nice as the left side. Next up the Z brackets that are part of the tank to spar attachment.

Time: 5 Hours

I was able to finish up the rest of the deburring on the nose tabs. Next up was to hit the rest of the edges on the scotch-brite wheel and remove all the imperfections from Van’s stamping process. I also grabbed the 1″ scotch-brite wheel and hit the lightening holes. With those tasks done I screwed down my flange tool to straighten the flanges to a 90° angle to the webbing.

With all the flanges now at 90° I was able to use my fluting pliers to take any curve out of the ribs. Before I called it a day I wanted to get at least one of the tanks assembled so I grabbed the leading edge cradle and grabbed the left tank skin. I have read several different builders sites and it seems that it’s 50/50 on how easy the ribs go in. Well for mine I was with the 50% that had trouble! I couldn’t get them slide in far enough to get the holes lined up while in the cradle. So I removed the skin from the cradle and really had to apply pressure to get the holes close. I’m worried about this as when it comes time to assemble these with the nasty Pro-Seal tank sealant on them. Here is a view with the left tank on the spar, has a pretty tight fit between the tank and outboard leading edge for the initial fit.

We will see how the right ribs go in their skin and see how worried I need to be!

Time: 3 Hours

Yes I actually got back in the hangar yesterday! This holiday season was very busy and I happened to throw in two weeks of the flu as well! But now I’m back and will get back into full swing as long as the weather cooperates, it’s been really cold here in the Chicago area! My heater has trouble keeping up with -15° temps and wind chills as low as -40°. Yesterday I spent the morning cleaning the hangar out from all the dust and road grime my truck managed to bring in. Tools got reorganized and parts were laid out for the future work. My goal was to get the right wing fuel tank ribs started. Like the other leading edge ribs that I have finished these too have all the tabs on the forward portion that need deburring. These are no fun and are time consuming to get all the edges between the tabs. So I turned on the heat, found a good movie on and sat down with the files, emory cloth and strips of scotch-brite pads and went to work. Not a whole lot to show but here the finished stack for the right tank.

I laid out the ribs for the left tank to start them.

Then I had a visitor show up for the weekend, my beautiful girlfriend! She’s in town for work and a post holiday party for our EAA chapter 95.

So that was a good place to stop working so I could take her out for a glass of wine and visit. It sure felt good to get back into the Hangar!