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.
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.
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.
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.
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.
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.
Time: 2 Hours
I spent most of the day working on my sons car. It needed new rotors, brakes and calipers for it to be safe for him to drive. I’m not much of an auto mechanic so it was a big job for me. So that took up most of the day but I was still able to get so work done on the RV after I scrubbed the Hangar clean from all the brake work. So you learn early that you put parts together and take them apart and put them back together. I had to take the tanks all apart so that I can do more work on the ribs.
The next step is to work on the fuel quantity sending parts. You have 2 options to chose from, the first is a float system that uses a plastic float that rises and lowers with the level of fuel. The float system is proven but also has moving parts and has the potential for failure. The second is a capacitive fuel sender. There are a couple of benefits to this design, no moving parts and very it’s sensitive to the amount of fuel and can read the quantity very accurately. I chose to go with the capacitive senders for the accuracy that if provides. The design is based off of two individual plates in the tank that have a small electrical current and are separated by a dielectric(insulator) in this case the fuel. The capacitance between these plates and the fuel is measured giving a fuel level. The first steps is to position the 2 plates per tank on their ribs per the plans.
I then matched drilled the 3 holes with a #20 bit on one rib. I then used that rib as a guide for the opposite end rib of the other tank. That rib was then used as a guide for the second rib on the first tank and finally it was used for the final rib of the second rib, clear as mud? The fact that the ribs are the same part number in both tanks allowed for me to place the ribs back to back and match up the tooling holes. These parts are pretty accurate so using the match drilling this way made the holes come out perfectly.
The plates are mounted on opposite sides of their ribs when viewed form
Inboard to outboard. So I laid them out as they would sit on the ribs so that I could mark them for the nutplates that they get.
I then treated all the edges and debured the holes so that I could rivet the nutplates. That was a pretty quick process with the squeezer. I decided to call it a night and clean up but before I did I mocked up one plate to see how it looked. The plates need to be isolated from all other metal, the rib, and have plastic spacers that take care of this.
Time: 5 Hours
Today I created a mirror of the bracket I made yesterday. I used a combination of the bandsaw, table disk sander and the good old scotch-brite wheel to get the shape just right.
The plans are a little vague about the next step which is to match drill the bracket to the rib as well as the reinforcing plate on the opposite side. The plans just call for the bracket to be 2″ from the leading edge and shows a pattern for the rivets but no dimensions. After talking to my friend (Glen a fellow -8 builder) I made a plan of attack. First I lined the bracket up to be parallel with the rib stiffening bend at 2″. Then I just eyeballed the placement of the rivet layout. Since I’m going with flop tubes in both tanks I needed to account for them with this layout. That’s due to the fuel line elbow will now come through these parts rather than the access plate at the aft end of the rib.
Once I was happy with the layout I drilled the holes to their final size, the very center hole will be enlarged to 9/16″ for the fuel line elbow. With that done I could now use the bracket as a guide to drill the rib and backing plate.