Author Archives: Michael

Time: 6 hours

Today I decided to do more research on the topic if covering up the middle hole in the second inboard rib of the fuel tanks. The lower hole has the trap door but I couldn’t find any description in the plans for covering the upper hole. I tried several searches on vansairforce.net and finally came up with one builders blog that had an email reply from Van’s Aircraft support:

After I decided that I would cover those holes I match drilled the covers to the rib and countersink them for riveting. I used flush rivets so that there wouldn’t be any chance the flop tubes could get hung up on them.

I then started the work on the anti-hang up mods for the inboard rib. The flop tube has the opportunity to get snagged or caught on the nutplates of the access plate. You can see in this photo this risk.

Van’s has you make a guide that sits proud on the nutplates like a bridge that gets riveted to the top and bottom of the access plate stiffening ring. The downside to that design is that it restricts you access through the hole as there would now be a 1/2″ wide strip of aluminum in the center of the hole. That would make using that hole in the future, should I need it, a lot tougher. Other builders have built a two piece guide that has one piece riveted to the access plate and one piece riveted to the stiffening ring. What this does is allow most of the guide to come out with the access plate and allow full access through the hole. I took my time and made several measurements to come up with a design that I was happy with.

I installed one of the flop tubes to see how it looked and fit.

With one side done I just copied the pieces for the other side, again building both wings at the same time is a great idea.

To remove the access plate you just need to slide the plate up and pull the lower portion out before pulling the top out.

It was a long day in the Hangar, I find that when I have to design and build a part from scratch it takes me a while to make sure I get it just right. I’m getting closer to the dreaded task of sealing the tanks. I ordered most of the supplies for that as well as a few more parts to make some modifications to the tanks baffles, more on that later.

Time: 6 Hours

Today I had a list of tasks I wanted to complete on the tank ribs and z brackets. My order of nutplates from Aircraft Spruce came so I riveted one to the last z bracket since I had ran short when I was working on them. Next was to finish up the capacitor fuel sending plates since I received my electrical tools. The outboard plate are connected to the inboard plate with an 18 Awg wire. They then are both connected to the fuel gauge system via a BNC connector. I soldered a BNC connector to 15″ of wire for the connection to the inboard plate. I then marked and drilled the 7/16″ hole for the connector on the inboard rib.

The outboard plate gets a 48″ wire bolted to it with a terminal end. The other end, as well as the end of the BNC wire, will also get terminals later when the tanks are riveted. This allows you to fish the wire through the bushings that hold the fuel vent, something you couldn’t do if the terminal ends were in. So with my new crimper I attached the the terminals as well as soldered them per the plans.

I then drilled the holes for the fuel vent line elbows in the inboard rib. This allows air to replace the fuel that is being used by the engine.

Next was to finish up the fabrication on the trap doors for the second ribs.

One other modification that some builders have done is to cover the lightening hole the is in the middle of the second rib, above the trap doors. This also helps keep fuel in the first bay for the flop tubes to pick up when doing aerobatics. I still haven’t decided weather I’m actually going to do this until I research it a little more but I made the plates anyways.

I decided that I would call it a night as it was approaching 10:30 pm but before I did I connected one of the flop tubes to see how it looked. I still need to fabricate the anti-hang-up guides that cover the access panel to prevent the flop tube from hanging on the nutplates.

Time: 4 Hours

Today I took care of some office items and played 2 hours of drop-in hockey at the local ice rink. I used to play a lot but had taken a few years off since my divorce. It feels really good to get back out on the ice and realize how old I am while playing with much younger and faster players. It was fun nonetheless and I’m hoping to get in the ice at least twice a week if not more. When I got home I jumped in the Hangar to carry the momentum I had from this weekend. First up is to mark and drill the fuel caps. I decided to go with upgraded lockable caps just cause they look much better and the stock ones have a history of being difficult to open. The ones I relieved are from Newton Equipment and are great looking and operate very smoothly.

I drew a line on the face of the cap flange that marked center so I had a reference point and clamped them to the skin as they were centered.

Once happy with the placement I secured them with vise-grip’s for match drilling.

The next step is to countersink the flange so that it could accept the dimples from the tank skin.

I got three done and my #40 countersink broke the pitot off, so a tool order is in order.

So I just moved on to the fuel drains. They come already drilled and countersunk, you just need to align it up with the hole in the skin and match drill it. I drew a center line on the skin and lined up the top and bottom holes. With everything looking good I clamped it down and drilled the holes. I placed a clecko in each hole as I drilled to help hold everything in position.

One other task I wanted to start today was the fuel tank trap doors. There are holes at the lower aft end of the tank ribs that are approximately 1.5″. These allow fuel to flow between the ribs and as the fuel moves. When doing acrobatics such as a knife edge (the plane flys with one wing pointing towards the sky and the other towards the ground) fuel on the lower wing try’s to move to the outboard of the tank. This isn’t good as the fuel pickup is at the inboard of the tank. So to help with this problem you fabricate a check valve of sorts called a trap door. The idea is to allow fuel to flow freely towards the fuel pickup and not the opposite. The trap door is simply a square piece of aluminum on a hinge that swings open as fuel enters the pickup area and covers the hole as fuel try’s to escape. I got the parts cut and shaped and will rivet them when I’m back in the Hangar on Friday.

Time: 7 Hours

Todays started with the finishing off the shaping of the 2 outboard capacitor plates to make for clearance the tank stiffeners on the bottom if the tank skin. Van’s says you can trim the plate and/or the stiffeners. I decided to just do the plates and measured for such.

Since the plates are exactly the same just on opposite tanks I just put them back to back to shape them at the same time.

Just a few minutes at the scotch-brite wheel and I had a matching pair.

There will be 12 spacers on each plate, 4 per hole. These had dangling chad hanging off them from the manufacturing process. I debured them with a utility knife around the outside edge as well as the inner hole.

The point of the spacers is to isolate the plate from the rib. You also use 1/4″ clear tubing that you slide over the screw to further ensure that there is no potential contact between the plate and the rib that it is screwed to. I made these tubes to the 15/32″ as per the plans.

That’s as far as I can go on the fuel capacitor kit as I’m waiting for my wire stripper and crimper to arrive this week. So I moved on to the next steps in the plans. In the inboard ribs of bit tanks there is an access plate that allows for servicing to fuel pick up lines (my case the flop tubes). This plate is rather large and you need to cut that hole in the rib. I ordered my fly cutter from Cleaveland Aircraft Tool.

I did the measuring to get to the center of of the circle of the rib and moved it to the drill press.

This cutter made quick work if the cut and I was able to knock out both ribs fairly quick.

Each rib gets a stiffener ring and an access hole cover plate. The original cover has various holes it if for the normal fuel pick-up line and the float type fuel sender. With the capacitor kit it is just a blank cover as you don’t need any of those holes.

Next up was to line up the stiffening ring so that the holes line up and allow the cover plates flat spot to sit parallel with the ribs stiffener bead.

The. I was able to match drill all the #40 holes for the nutplates and the #19 holes for the AN509-8R8 screws that hold the cover plate on.

The stiffener ring gets riveted to the rib and nutplate. The ring needs to have the rivet holes countersunk to accept the dimples from the rivet holes in the rib. That way the rivets will be flush with the inboard side if the rib to allow the access cover plate to sit flush and be sealed. I set up a piece of oak and drilled half of the rings holes into it and clecko’d it down. This gives my countersink bits pilot to have a guide in the wood and removed the chance of the bit wandering.

With all the holes in the rib debured I hit the rivet holes with my 3/32″ dimple dies setup in the pneumatic squeezer (my favorite tool) and dimpled all the holes in a matter of 60 seconds.

Left side done and on to the right side. I would probably have my plane done by now if I didn’t have A.O.C.D. (Advanced Obsessive Compulsive Disorder) as I have to clean up my work area after each project. So even though I will be drilling the right side now I needed to clean up before doing so. That means vacuuming all the drill shavings and mess I made.

Bith sides are done but before I can do any riveting I need to debur all the edges. So I hit all the inside circles with a 1″ scotch-brite wheel and all the outside edges on the bench wheel. Then I clecko’d everything up and grabbed the squeezer. I had all of the nutplates riveted in about 30 minutes.

I then grabbed 12 of the AN518-8R8 screws and temporally attached the covers.

It was a pretty good day in the Hangar! Next up will be the fuel drains and and fuel caps.