Sling 4 for Matt Build Log

I finally ran out of excuses to not work on the V. Stab. and got to work. TIME: 2 hrs The first task was to test fit the assembly. Two things of note: 1) Some of the rib flanges didn't align well with the rear and front spars, so some work with a hand seamer will be necessary; 2) The bottom ribs (1 & 5) require riveting through 4 layers, which usually means alignment challenges. I asked for a VOR doubler plate from the factory. The doubler plate is cut to fit inside rib 4 and follows the contours of an airfoil. However, rather than nicely rounded edges, it's a series of straight segments that are rather unappealing. The image below really demonstrates the awkward outline segments.  I believed that is was just shotty work and I would clean it up myself. Unfortunately, I don't have a bench sander, so away I go with the file.   The final result above looks nicer, even though this plate will never be visible when the skins are closed out. Consequently, I took a closer look ...

When last I spoke of this, I had drilled and cleco'd the second EL wing tip using the fitting technique Craig wrote about. The technique was easier on the front end and easier on the backed. Here was my starting point: Removed and cleaned the composite: It's still a challenge fitting the wing tip back into the skins. I aligned the composite with rivets and required no reaming. Note that on the tailing edge, one side uses a short rivet (4mm) and the other uses the standard length (8mm): Even though not pictured, I replaced every other rivet with clecos and riveted the wing tip on. The gaps between the skin and the composite were smaller on this side, but the composite had a few spots that need to be filled. Final Thought: I'm glad that I put heavy-duty castors on the work benches. It's convenient to be able to reconfigure the work space quickly and easily. 1 hr Next steps: Fix EL trim gusset (ugh!) Install EL access plate r...

Believe it or not, it can get cold in parts of San Diego in the Winter. Cold enough, in fact, that I could prime elevator parts for a week. But, last weekend the temperatures warmed up and I was able to finish priming the E1-E3 assemblies. I didn't get around to assembling things until today, however. Very little seemed to go right. The trim tab appears to have a bad bend on the inside flange that results in warping the trim skin. It takes on a crescent shape (not pictured), and that won't do. I intend to drill it out and look into fixing or replacing the skin. Next, I discovered I need a small torque wrench to set the five AN3 bolts in the assembly before I can close out parts of the assembly. I need some Loctite too for the bolts and rivnuts, but even the rivnuts could wait. This also lead me to realize I should order some torque seal marker paste as well. Not dwelling on having to remove the E1 rivets, I completed all I could on E2 without Loctite and...

From my previous E2 work post, test fitting the parts revealed an alignment problem with the spar box channel. I sent a picture to TAF and the folks from SA said it was acceptable to drill out the spar box holes to match and that the multi-grip rivets would fill the gaps. Rather than drilling through the spar, spar box, and spar doubler, I opted to mark the spar box hole offsets with a fine point Sharpie. I then used the marking as a guide coat and removed the material using a small round file. I refitted the spar box and was able to insert all but one rivet. After a couple of stokes with the file, the final rivet dropped in without a problem. I mentioned in a previous post as well that I ordered short rivets from AirSpruce rather than filing down all the 8mm long rivets necessary to attach the EL trim tab. The short rivets arrived today and here's a quick look: The two on the right are the short rivets while the one on the left is the 8mm provided in th...

Inspired by a series of articles this month from Kitplanes Magazine, I was reminded of the effectiveness of a good, old-fashioned Work Breakdown Structure (WBS). This is a charting technique for understanding project execution order, scope, parallel work organization, and Critical Path (CP) events. Being a software engineer, I'm very accustomed to managing large, long-running, and often rather ambiguous projects from inception to completion. However, building an already designed and fabricated airplane with defined build steps is quite a relief from the ever changing requirements, priorities, and technologies in the software world. Building an airplane is a long, often multi-year process and whether it's a one or one-hundred person undertaking, basic project management techniques can help keep it on track, improve efficiency, provide and unambiguous definition of done. Below is my combined WBS and CP chart for the empennage kit. The top and bottom levels identify the s...

The elevator trim tab work required the shortening of a large number of 8mm long rivets for attaching the trim hinge. Then as many rivets again would need to be shortened to attach the hinge to the elevator. I opted to follow the approach of another builder and just order short rivets from Aircraft Spruce (Ordered 100 BSP-41 cherry rivets  https://www.aircraftspruce.com/catalog/hapages/cherrynrivet.php ). There are a number of other subsequent rivet shortening steps in the instructions, so this is well worth it. I went on to remove the vinyl from the elevator E2 and E3 assemblies and inspect for damage. Unfortunately, one of the two Rib 4 pieces was tweaked beyond repair, presumably at the factory. I believe it happened at the factory because no other piece in proximity to it had any damage. I entered another part replacement request and moved forward. I suggest clecoing the outside ribs, hinges, and trim server plates first before working on the assembly in the center of ...

The night before last, I pulled my first rivets on this Sling 4 kit. With the fuselage partially completed by the previous kit owner, these weren't the first official rivets, but they were mine. Also, I did it with a hand riveter because I didn't have an air compressor. I have a pneumatic rivet gun, but no air. Yesterday (Friday) I was prepared to purchase an air compressor. Naturally, my first step was to check with my wife, who has reminded me to mention how supportive she is of this project. Thank you, Dawn, for being extremely supportive. Anyway, Dawn let me know that her mother wanted to give me something nice for my birthday (and the coinciding holiday, Christmas). She mentioned to her mother than I needed an air compressor and her mother generously paid for the one that I wanted. Thank you very much, Chris! Time to complete HS1: I set up the rear HS spar with the remaining ribs and brackets and went to work. As with the spar rivets, I used rivets in all t...

The time finally came to pull the first rivet. More on that later. One common issue I've come across reading other builder blogs is the problem of misaligned rivet holes and the need to ream holes to match. I'm sure I'll encounter that at some time, but I started with a rather simple technique to ensure rivets fit. And spars are good since you may have three or four overlapping parts and even a slightly misaligned part at any layer can make it impossible for the rivet to fit through. The picture below and left depicts using rivets only to ensure hole alignment. I made sure every rivet fits through all the parts as designed. I didn't take a picture of the next step, but it looks like the one below and right where every other rivet is replaced with a cleco. I did experiment originally with first clecoing parts together and then trying to fit rivets through. I found that rivets wouldn't fit through most of the holes due to ever so slight misalignment. I coul...

I started on the elevator trim tab but encountered the horror of "clear vinyl" on the skins. I had a few parts from the h-stab that left a little adhesive residue, but nothing like this. VAF to the rescue with this post:  http://www.vansairforce.com/community/showthread.php?t=93363 . Or, rather 47 different opinions on solving this problem. The part number sticker contains a date and I believe it's the manufacture date (and not the revision date). After a couple of years, it appears the adhesive is confused about what it should do.

This weekend I moved ahead to get the horizontal stabilizer primed and ready for partial assembly. I say partial because I'm waiting on a spar doubler plate replacement for TAF. I spent a lot of hours deburring, smoothing, de-scratching, and rounding corners on the H-Stab parts. I think I can streamline the process a bit more based on commonalities in the parts manufacturing process, but the parts do need some TLC before assembly. Add to this the cleaning and priming steps and I'll be looking at a long build process. The picture above shows the horizontal stabilizer parts after cleaning with Simple Green Extreme Aircraft and rinsing in distilled water. I then cleaned each part using acetone and hung them in the "paint booth" below: The paint booth is a 60"x63" portable closet with the bottom sealed using plastic sheathing. I found it too difficult to paint parts this way, however. Next time, I'll paint the individual parts on one side of the ...

Continued work on horizontal stabilizer parts including deburring rivet holes, edges, and rounding corners. The work is slow going, but I'm happy to get the parts to the point I know the mating surfaces will be gap free. The grommets for the trim servo wire are barely big enough to fit the provided 6-core wire and too big to fit in the pre-drilled holes in the ribs. I increased the rib hole sizes to 3/8" since the caliper measurement outer diameter of the grommet measured 25/64". The grommets fit and the wire is able to pass through the new diameter. I need to go back over the nose ribs and round out the corners I skipped. After that, I'll be ready to clean and prime the horizontal stabilizer parts, but I won't be able to assemble the complete frame. One of the plates is being replaced and not due to arrive until April. I want to take a moment to describe my parts inspection/preparation process. I don't know if it's more or less than other...