Fuel tank fittings

Posted on by Neal

Tonight I installed most of the fittings into the fuel tanks. The only fitting I didn’t install was the drain on the left tank. Since that wing is sitting on the bench, and the drain port is on the bottom, I’ll wait until I put it back in the stand to install.

I spent time researching exactly how much torque these fittings need, and how to apply the sealant. Couple of useful videos on the EAA website, and more specific info on Vans Airforce. These (like all fuel fittings) are NTP, tapered threads. Torque values are not really applicable, since the jamming of the threads is what provides the seal. It’s not a complete seal, since there is a spiral pathway that fuel could flow out of the fitting, so some sealant is required. Over-torquing will damage the threads, since these are aluminum fittings and relatively soft. Vans recommend installing by tightening until the first sign of resistance is encountered, then turning 1.5-2 turns beyond. The sealant recommended by both the EAA and Vans Airforce members is called EZTurn, which is a sticky, but workable fuel-resistant sealer. Tape is not recommended, due to the risk of contamination of the fuel system with chunks of tape. For the same reason, any sealant should not be applied to the first 2-3 threads on fuel fittings.

Fuel-resistant sealant, next to the drain valve and fuel strainer

I started by cleaning out the fitting ports, using some rubbing alcohol on a lint-free rag. Despite taping over these ports, there was a surprising amount of dirt in the threads. Then I cleaned the fitting threads and applied a coating of sealant, skipping the first 2-3 threads.

Fuel strainer with sealant applied
Fuel plug. This plugs up a hole that can be used for a fuel-return system

I got all of the fittings in, except the left tank drain port, which I can quickly add once the wing is in the stand. I’m going to keep it on the bench until my landing lights arrive on Thursday, so I can fit them. The last step in the tank work is testing for leaks, which I will tackle next weekend once the proseal has fully cured.

All fittings installed on the end of the left wing tank
Right wing fuel drain fitting attached

Fuel sender install

Posted on by Neal

I’ve been waiting on some more tank sealer so I could install the fuel senders. UPS claimed they delivered it on Wednesday, but it didn’t show up. On Thursday it turned up with another package, so I was able to install the senders tonight.

Cleaning up after the fuel sender install. Happy with the left tank, not so much the right tank.

I took time doing prep work; scuffing the surfaces, cleaning the surfaces, checking that my multi-meter was working, checking that the screws installed in the nutplates, checking that I had the right size Allen Key, etc. Finally I was ready to mix the sealant and get started.

I had one wing on the bench and one in the stand. The wing in the stand was in a slightly awkward position, as the stand itself was interfering with the placing of the sender into the hole in the end of the tank. With a bit of adjustment I got it to work ok, and that’s the wing I started with. In hindsight, I should have started with the easier wing, so I could build some experience. Oh well.

On the right wing, I could have used more sealant. I’m sure I got a good seal in the end, but I don’t think I hit the goal of 0.7mm between sender and rib. This space is to allow easier removal of the sender in the case of future tank maintenance. With a slight gap, a blade can get in there to cut the sealant. I have some gap there, but I think it’s less than desired. It’s also tricky to get an even torque on the screws around the flange of the sender, it’s probably not exactly square. I checked that the plate is grounded, and it seems fine.

Tank sealant is messy… the right tank fuel sender is installed

Then it was onto the easier-to-access left wing. This was quick, clean, and came out great. I used more sealer, and ended up with a nice even bulge of seal around the sender flange. Looks to be just right. Hopefully if I have to do maintenance on tanks, it’ll be the left one!

A much cleaner installation on the left fuel tank

Next up I’ll be installing the tank drain fitting, then pressure testing the tanks for leaks.

Fuel senders

Posted on by Neal

Last night and tonight I bent the fuel sender float arms to the right shape and test fit them into the tanks. It’s a bit hard (impossible?) to tell if the floats are exactly where they are supposed to be, since the tanks are already assembled and sealed. Perhaps if I had a tiny borescope I could peek inside the tank drain and see.

These came out ok, and from careful testing, I can tell they are just off the bottom of the tanks (plans call for at least 1/16 from the bottom), and not interfering with the vent lines. I have no way of testing if they are staying clear of the top of the tank.

I can’t do the final install on these until I get another shipment of proseal, hopefully this week.

Fuel sender. The lever changes the resistance of the circuit as the fuel float moves up and down.
Float arm bent to the correct shape
Two finished fuel senders, ready for final install.

VA-146 Flange Bearings

Posted on by Neal

Tonight I installed the two VA-146 flange bearings, one on each wing. The holes were already final size and deburred, so this was just a case of setting the rivets, easy! the only challenge was working around the wing stand for the right wing (the left is on the bench).

These bearings will hold one of the aileron pushrods attachments. It’s a tube that runs fore and aft, and connects the fuselage pushrod the the one in the wing.

Landing light lens

Posted on by Neal

From Sep 26 to Oct 1, I spent several sessions in the garage working on the landing light lens. Since this was my first foray into working with Plexiglass, I did some research to learn how others have done this. The use of a Dremel tool was recommended, and Vans day to never use a saw, as this will splinter the material. Plexi-bits are also required, but hard to find in the right sizes. I made my own by grinding off the edges of some existing bits, following some advice from YouTube. Then I started with the left wing.

The first steps are to trace lines on the wing and the lens, and then start trimming.

Cutting the plexiglass with a Dremel tool

Covering the lens in tape to prevent scratches is a good idea, as is adding some tape to pull the lens into position (I used blue duct tape). I kept the tape on until I was done countersinking and fitting the lens, then I peeled it off to start cleaning up the edges.

Counter sinks in the plexiglass were easy
Final fitting with dimples and countersinks done

I found that my vixen file did a nice job straightening out the sides of the lens, and my smaller round file cleaned up the edges, rounding them until smooth. I used some sand paper to clean up a few spots, then declared the lens “done”.

Fitted and screwed into position

The screw call outs in the plans were for a slightly shorter stainless screw, but they weren’t included in the kit anywhere. I emailed Vans, they suggested using the longer screw, which I did, and recommended using a carbon screw in the future, as these tend to weaken and snap over time.

After doing the left lens over several days, I knocked out the right lens in one evening. So much faster the second time!

My only concern in this whole step is the gap that exists at the forward edge, between the lens and the wing. This will be ok for first flight, but at some point I may redo these both, or find a way to seal the gaps. When flying through rain or cloud, moisture will easy enter the light cavity.

Landing light bracket install

Posted on by Neal

Tonight I put my new pop rivet dimple die to work, and installed the landing light brackets on the wings. This was the first time I worked on the QB wings themselves. I practiced with the pop riveter, getting a feel for just how much pressure can/should be applied. I snapped the shanks off a couple of nails before settling on the right amount of pressure (not much). I was able to get to all of the holes with both wings in the stands, but it was also obvious I’ll need these wings on a bench to finish the job.

Outside view of pop riveter. A stainless construction nail serves as the shank.
Inside view. The head of the nail visible in the center of the female die

With the dimples set and looking good, I went ahead and riveted the two brackets (one per wing). The rivets were easy enough to buck, even in the wing stand.

Landing Lights

Posted on by Neal

Over the weekend, I started on the landing lights. The holes for the lights are already cut into the leading edge of the wing, but annoyingly the holes for the landing light mount are not dimpled. In a slow build, these holes could be dimpled with the DRDT-2, but at this stage of assembly, I need a custom tool to reach the holes. I picked up a dimpler that works with a pop-rivet gun. The dies are cut so that a nail can be passed through the center of each, and inserted in a pop rivet gun. The gun pulls the dimple dies together to form the dimple.

3/32 size dimple dies, for use with a pop rivet gun. Makes accessing hard-to-reach holes easier to dimple

Anyway, I got started by dimpling the brackets and attach strips, along with the 20 nutplates.

Landing light attach brackets

Then I primed the parts, going for a thicker coat on the brackets which will be partially visible inside the light cove.

Primed landing light brackets. Note the VS attach plate in the background, which I also primed.

Per the plans, I also painted the inside of the light cove with my white epoxy primer. I’m just trying to keep the color consistent, and not really worried about final paint at this stage. My paint gun *just* fit inside the lightening hole in the outboard rib, so I was able to paint the sides of the ribs, and the inside of the skin.

Landing light cove. Hard to tell, but the visible areas of this cove are primed with white paint

The next day, with the paint dried I riveted the nutplates to the brackets and attach strips. I used my new “main squeeze” hand squeezer for all the rivets, securing the squeezer in the vice and holding the work. This went quite well, and I definitely love the squeezer. It requires very little force to squeeze the rivet, and is compatible with all of my existing yokes.

Riveting nutplates with the Main Squeeze
Nutplates installed on the landing light brackets

Garage Clean-up

Posted on by Neal

The last week has been busy, and my time in the garage has been spent cleaning up and reorganizing. I picked up a small tool cart that I can wheel around the garage to keep tools where I need them, without getting them scattered around the place. The cleanup was long overdue, and make me feel more organized.

I also spent time reading and researching the wings, and going through the chapters covered by the Quick Builders.

The first parts of the wing kit I will be working on are the landing lights, at least the housing and covers for the lights. These are located at the ends of the wings, and were obscured by my wing stand. To work around the issue, I modified my wing stand by building another carpet strap just inboard of the existing one. It was slightly challenging as the wings were in the way, and I didn’t want to lift them out of the cradle. I worked around that, and they came out ok.

Finishing Aft Fuse

Posted on by Neal

Today I officially finished section 10, the aft fuselage. With the empennage attachment finished, I completed the final step in section 10, riveting the forward bulkhead to the top skin rib.

I positioned the aft fuse on my work benches, and rolled it onto it’s side. By lying down inside the fuse, I was able to rivet 2/3 of the rivets using my new “main squeeze” hand rivet squeezer. The last rivet needed to be bucked as it was too tight against the skin, and the rib. Using a double off-set in my rivet gun I bucked it. Not my best rivet, but good enough.

Then I completed the aft fuse by screwing on the inspection port covers on the aft end. After I located the correct set of 16 screws, I had a frustrating time with a couple of the nutplates, where the screw wouldn’t sit squarely in the hole and wouldn’t engage with the nutplate. Withou the covers in place I was able to get the screws in, and that seemed to fix the issue. Covers are now installed.