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.