I picked up some spiral wrap from Aircraft Spruce and put it to use today. It’s good for protecting wiring runs from chafing, and for stiffening and organizing wires. I used some at the point where the elevator and tail light wiring transitions from the forward bulkhead to the j-channel. I also added a small length at the point where the wires pass through the bulkhead, and secured it all with zip ties.
Spiral wrap in 3 different diametersForward bulkhead with wiring run secured, and spiral wrap attached. This gives some stiffness to the bundle, and provides some protection from chafing on the edges of the j-channel and bulkheadThis extra length of spiral wrap is giving some protection from the bulkhead edge. It’s secured on the other side with a zip tie
Aft of the bulkhead, zip ties are keeping plenty of clearance between wires and sharp edges. At the aft end of the j-channel where the wiring run transitions through a bushing in one of the aft bulkheads, I added some more spiral wrap to the elevator trim wires. The elevator trim wires pass through this bulkhead then route up and through the the aft deck via a molex connector. There is a lot of slack, so I created a service loop and secured it with zip ties on the bulkhead. The concern here is to make sure these wires could never interfere with the elevator pushrod that passes through this area.
Looking aft, spiral wrap on the elevator trim cables protect against chafing and keep the wires together. The elevator pushrod will pass through the hole in the bulkhead in the top left of the pictureLooking forward, service loop is secure below the opening for the elevator pushrod. The molex connector will plug into a port on the aft deck.Close up of the service loop. This is secured against the bulkhead with a zip tie. If that were to break, this loop is stuff enough to remain in position.
Tonight I primed the top and top side skins. I started in the afternoon cleaning and etching, then came back into the garage in the evening to paint. I used a new paint nozzle on my gun, and it made a big difference in quality. I’ve been using the original nozzle since I started about a year ago, and it was past due for a replacement. The combination of high air flow and new nozzle made a huge improvement over my initial attempts at priming. I finally feel like I am getting the hang of painting with the spray gun.
About to start paintingTop right side skin primed. Aft deck in the foreground
I heard back from Vans this week about the cracked dimples. I was anticipating installing a doubler plate, but their advice was to upsize the holes and install oops-rivets (rivets with a -4 shank and a -3 machine head). I didn’t think upsizing the hole would remove the cracks, but I did it anyway. On one hole the crack was removed, and on the other it was better but still not completely eliminated. I carefully inspected and filed down the dimple slightly to remove the remains of the crack, and plan to install oops rivets tomorrow. I took pictures and emailed to Vans and Jason for a second and third opinion.
One of the cracked dimples.
I also heard back from Vans on the spar deburring question. Here is their response
Just a quick follow up, Engineering has just given me a written response to your initial question about deburring (or lack thereof) on your wing spar.
There are considerably higher stress concentrations elsewhere in the spar than along the edges of the spar doubler (waffle plate), e.g. the spar to center section attach holes and the notch in the spar web where the flange terminates. Early version waffle plates were not deburred and were deemed acceptable. Spars were static-tested to 150% of Limit Load (aka Ultimate). Experience has shown that static tests exceeding ultimate loads tend to produce shape failures at locations removed from the main spar. As part of the annual condition inspection, it is required to examine the connection between the wing spar and center section. This would reveal any evidence of fatigue cracking at these higher stress concentrations. Therefore, the un-deburred waffle plate edges are not critical.
Last night, and again tonight I spent time deburring the top side skins. I finished deburring these skins, and these are now ready to be primed. My goal is to prime them this weekend, so they are ready to go when I need them in the near future.
At this point I have a number of tasks to complete. I need to fix my cracked dimples, finish up my wiring runs (install a couple of zip ties), install the aft deck, then install the top skins, finishing the aft fuse. Then I need to start working through the QB sections, checking that all steps were completed.
Jason came over for a visit today and reviewed my work on the aft fuse. We talked about some of the wiring runs and some of the more challenging rivets. His comment in the write up of “very high quality” was really encouraging. We also looked over the QB wings and fuse and he gave me some great advice while also pointing out some issues. There is a lack of deburring on the wing spar “waffles”, which I emailed Vans about. Also a couple of scratches and notches that I’ll need to debur.
Later in the day, I went to work riveting a few rivets that I had found to be difficult on the aft fuse, and had left until after I had talked to Jason. These rivets were instructed by the j-channel, and when I set them using the foot of my I long bar, the rivets had a tendency to cleave over. Jason offered a couple of simple suggestions, including taping my other bucking bar to increase mass and center the rivet along the center of mass. This worked great!
Taping two bars together helped put more mass inline with the rivet being bucked
Unfortunately I ended up cracking dimples on two rivets, when I stupidly set the rivet while it was not completely square with the holes. For some reason, a alignment issue caused the rivets to not sit squarely in the hole, and instead of investigating and perhaps reeming the hole, I set the rivet. This caused the rivet to transfer stress to the bulkhead flange and crack the edge of the dimple. Really stupidly, I did it twice, on different bulkheads. I didn’t detect the first one until after setting the second rivet. I emailed Vans asking for advice, and went to bed feeling frustrated.
One of the two cracked dimples. The other one is on the other side on a different bulkhead. I had left these rivets to the end because they are behind the j-channel, and setting them had Ben difficult
There are a few holes on the aft deck components that need to be match drilled, as they are fabricated by the builder. Today I clecoed and clamped together these parts and drilled the 5 holes.
Aft deck parts clecoed in position. I used clamps to support these parts while drill the holes. Here you can see the cleco clamps on the aft brace where three holes are match drilled.
Aft deck and some top skin components cleaned, etched and ready to be primed
Today I primed the aft deck components and some of the top skin reinforcing parts. I used 50 grams of part A, and it was just enough to get a coating I was happy with.
Tonight I spent an hour deburring some of the remaining parts for the aft fuselage. Not much to go now, just some aft deck components, and top skin parts with associated stiffeners.
Some of the remaining components for the aft fuselage after deburring
Tonight I riveted on the two aft angle stiffeners, one on each side, below the inspection cover. This was easy, except for the bottom most rivet on each side. No matter what I tried, I struggled to get a bucking bar on the rivet. It worked out ok on one side, and was a mess on the other. Unfortunately, access to the bottom most rivet is almost impossible, so I have not attempted to replace it, for fear of making the situation worse. I’ll review it with my tech counselor when he comes (hopefully soon).
Outside view of stiffeners going from bottom left to top right. Smudges on the skin are due to rivet tape residue which I’ll wipe up soon
Today I completed a couple of steps on the aft fuse by attaching the rudder stops and about 30 nut plates.
The rudder stops turned out to be easier than I thought. I was able to start by squeezing the aft two rivets easily, and then bucking the forward two without much trouble. I did the right aft side, then the left aft side, then right forward side, then left. Both came out fine.
Aft end showing 4 squeezed rivets holding the rudder stops on, with two holes to go on the forward endsThe vacant holes below will get rivets soon. The bottom one is the aft-most rivet that goes through the side skin, bottom skin, and bulkhead. The other empty hole is for the angle stiffeners which goes up and to the right on a 45 degree angle Fairly easy to rivet, although clearances were very tight
Then I dimpled a set of nutplates and started riveting them on. I dimpled 4 nut plates that I shouldn’t have, as I found an error in the drawings. The diagram called out for 9 dimpled nutplates and 5 un-dimpled on each side. But it should have been 7 dimpled and 7 in-dimpled, as there are 7 that sit flush with the longerons. I have a ton of these things, so it didn’t matter at this stage.
I started with all the un-dimpled nutplates, which was quick and easy. Unfortunately I had to drill out a rivet when I inserted it without checking that it was passing through the nutplate. It wasn’t, so I drilled and redid that one.
When I moved onto the dimpled nutplates, I realized I hadn’t held the nutplates steady enough when dimpling. As a result, many of them were slightly bow shaped. This was problematic, as they wouldn’t sit flush against the holes, and had a tendency to break when the second rivet was set. It took me a few nutplates to realize what was going on, and then I drilled out several, dimpled new nutplates (this time holding them level when dimpling), and then re-riveted them on.
Dimpling a platenut
The end result was ok. Some of my rivets didn’t set as well as I wanted, but these are not structural, and plenty strong enough to support the screws they will be holding. my main concern was making sure they were straight, aligned with the hole, and not likely to snap off.
Looking left to right through the access panels. Here you can see the outside view of the left hand rivets holding the nutplates, and the inside view of the right hand side nutplates. These hold screw that secure the access panels here, under the horizontal stabilizer.
