Aft Fuse

With my benches on wheels, I was able to move them apart and install some lengths of 2×4. These can support the DRDT-2 between the two benches, creating a more convenient area to dimple larger skins. My Dad first suggested this earlier in the year, and I’ve since seen several build logs where this has been done.

With the dimpled in place between the benches, I went to work dimpling parts. Starting with the top skin and components that mount to if (j-channel, doubler and a rivet), then moving onto the top side skins. It took some moving of benches to get at all the holes, but the second one went faster than the first.

My helper! She loves to come and see what I’m doing and help any way she can.

With the skins all dimpled, I clecoed the left top side skin into position for riveting. I plan to back-rivet as much as I can, and will do some research first to see what others have done before I begin.

With the wiring secured, I started riveted the aft deck. I worked on this over several evenings (6/28 -7/1), doing a few rivets at a time. Mostly this was straight forward, but I did have a couple of frustrations with rivets in tight corners near the aft end, and tucked in close to the protruding bulkhead attach points. I was able to squeeze most of the rivets, but had to use my double-offset rivet set on several. It’s really easy for the double-offset rivet set to jump, and it only takes a tiny skip to cause a smiley face rivet.

I emailed Vans about the rivet length callouts where several different lengths are specified in areas where the same material is being riveted together. The response was to go with the rule of thumb for determining length, plans are guidelines. So I measured the thickness of the material and added 1.5 times the rivet diameter to get the rivet length, then rounded up. A little long is better than a little short, provided the rivet doesn’t cleve over.

I haven’t actually finished this step yet, as I don’t have a long enough flush rivet set to clear the forward bulkhead. I’ve ordered one from Aircraft Spruce and it should hopefully be here by the weekend.

Additional wiring for antennae pass through a snap-bushing on the aft deck.

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.

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.

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.

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.

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.

Van’s Engineering Response;regarding an RV-14 W-00006C Spar doubler (waffle) plate’s un-deburred edges.

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!

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.

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.

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.