With the leading edge prep work done, I clecoed them together. Here’s the left leading edge.
Left LE clecoed together
The next day, Captain John and I riveted them.
LEs riveted
John and I have a pretty good riveting rhythm going…I shoot and he bucks. Using my Sioux 2x gun with a straight mushroom set (yep, we’re going bareback here – no swivel set or rubber guard) and the tungsten bucking bar I bought from Bucking Bars by Webster, we got really good results.
After cutting landing light holes in both leading edges and fitting the AoA probes in the left leading edge, it’s time to debur, dimple prep and prime the leading edge skins, landing light parts, joint plates, and a lot of other miscellaneous parts like the inboard leading edge ribs. So…after deburring and dimpling – not very visually exciting, so no picture – that means the obligatory wash/degrease/scuff/etch process.
Here are the landing light brackets and the inboard LE ribs drying after being alumiprepped.
LE parts prep
And here’s everything after priming, and after back-riveting nutplates to one of the W-423 joint plates that fasten the leading edges to the tanks.
AoA port holes
My goal is to get both leading edges ready for riveting in the next week.
I’ve been tying to finish as much of the leading edge work as possible before they go on the wings for good. That includes the Angle of Attack (AoA) system I bought from Advanced Flight Systems. The “A” kit for this system includes the pressure probes that provide static pressure above and below the wing to a processor that computes AoA. If you’ve got a hankerin’ to know how this system works, click here (MS PowerPoint required).
These pressure probes go in the outer portion of one leading edge; the locations are specific to each airplane design. Captain John had already installed an identical system in his RV, and he lent me a drill template he fabricated for the port. Here it is taped in location on the left upper leading edge.
AoA port template
Here are the holes…two for the #4 screws that hold the probe in place, and a #60 hole that actually provides static pressure to the probe.
AoA port holes
Here’s the upper probe temporarily screwed into position. The Duckworks instructions hint that the screw holes can be dimpled with a #30 die, but I couldn’t get the screws to set flush in a test piece of scrap – so I called Cleaveland and ordered a set of #4 dimple dies – worked great.
AoA port
Here’s the upper probe itself, the lower probe looks very similar. The quick drain on the bottom of this probe allows moisture to be drained from the probe. The kit comes with a ‘poker’ that’s inserted through a hole in the underside of the leading edge to push in the quick drain.
AoA probe
Small-diameter tubing connects that barb on the probe to the processor in the cockpit. I won’t install them until the leading edges have been riveted on to the wings.
Welcome back to the wings! I’m wrapping up the tanks, but in between tank sealing and riveting sessions I started to do some work on the rest of the wings. Over the last five days I worked on the leading edges, getting the W-423 joint plates deburred and dimpled, and starting work on the landing light installation. No pictures of the joint plates – pretty boring stuff.
The landing lights are more interesting, I’m putting 100w Duckworkslights in both leading edges. The Duckworks kits come with decent installation instructions, and following them I had no problems with the installation. The first step in this process is using the provided template to mark holes on the outboard ribs for the screws that will hold the landing light brackets…
Template for screw holes
…and for the hole that will be cut to let the light out.
Template for light opening
Hole marked for light opening
The next step is cutting the leading edge hole. As you might guess, there’s a slight bit of a pucker factor here because of the potential to screw up the leading egde skin. To make the hole, I pilot-drilled holes at each corner of the hole and opened them up with a Unibit. Then I used a side-cutting bit and a cutoff wheel in the Dremel to rough-cut the whole opening. The side-cutting bits don’t cut agressively so they’re a little easier to control.
Rough-cut landing light hole
I followed that up with a sanding drum on the die grinder, followed by a small scotchbrite wheel on the same tool. The end result was a nice hole. After that, I match-drilled the lens mounting brackets to the skin – sorry, no pictures.
Rough-cut landing light hole
Over the last three days I finished a lot of prep work on the left tank in preparation for attaching the baffle. Got the outboard rib sealed and riveted, attached and wired the sender plates, and permanently installed the flop tube into the inboard leading edge.
I also had to find a way to secure the hinge pin that holds the trap door in place on the second inboard rib. The second rib and trapdoor form a sort of header tank that retains fuel when doing aerobatics. I can foresee a need to remove the hinge and door at some point, so I wanted to make a clip that I could reach just by removing the access plate. The little clip has a small hole for safety-wiring the hinge pin, there’s a little proseal on there as well.
Here’s the screen in place on the pickup. It will be safety-wired and prosealed in place on the pickup tube.
A couple of weeks ago I received the brass screen I ordered from McMaster-Carr. I needed to finish up the right tank’s fuel pickup, so I broke out the wire cutters, soldering iron and solder to fabricate a pickup screen.
This turned out to be a lot easier than I anticipated; the only trick was keeping the screen from unraveling while cutting and forming it. Running a bead of solder along one edge of the screen ‘locks’ the individual brass wires in place, making it easy to roll into a cylinder using a piece of 3/8″ aluminum tube as a mandrel. Solder the long side of the cylinder together with more solder, trim the excess screen away then close the end – and voila, a pickup screen.
Before somebody emails me, yes, I do know now that Van’s sells a pre-made fuel pickup with screen. But I already had the screen on order when I found out, so I decided to experiment – and it was easy to make an acceptable screen. I’ll probably continue to experiment with this over then next couple of days.
With the end ribs in place, I worked on some of the cleanup items that needed doing before the tanks are sealed. One of those items is a Van’s service bulletin that calls for safety-wiring fuel pickup attachments. Fortunately, the pre-made flop tube I bought from Van’s already had a safety wire hole drilled in the flare nut, so all I had to do was attach the flop tube to the bulkhead fitting – using the proper torque, of course – then safety-wire the assembly.
Looks like this…
I was definitely out of practice with the safety wire pilers – took me a couple of tries to get a nice, tight twist on the wire.
Had a visit today from Jon Ross, my EAA tech counselor, and Mike Muratore, friend and former flight test colleague. We talked about tank sealing technique and fuel pickups. Looks like I’m still on the right track, and we’ll plan another visit before I close out the wings.
I’m getting burned out on proseal and the mess and cleanup that accompany it. So I’ve been pushing pretty hard to get the inboard ribs riveted into both tanks. The only ‘gotcha’ on these ribs is fitting the T-410 reinforcement plates and the T-405 attach angles to the rib. The plans don’t specify an exact location for the angle, it just fits as far as possible into the leading edge of the rib.
Some builders get into trouble by riveting both the angle and the plate in place before the rib is riveted; they then find out that there’s no room to squeeze those rib-to-skin rivets that lie between the angle and the rib. Take a look at the picture below and you’ll see how everything fits together.
For me, the best way to put this assembly together was to rivet the inboard rib in place with a minimum amount of sealant around the front of the rib. I held the T-405 angle in place and match-drilled through the top and bottom pilot holes into the rib, clecoing as I went. Then I removed the angle, taped the reinforcement plate in place inside the rib and match-drilled it through the holes just drilled in the rib. Finally, I clecoed both the plate and angle to the rib and match-drilled the remaining holes. For the left tank, the center hole also became the pilot for a 3/8″ hole which will accomodate the flop tube bulkhead fitting.