Mar 26, 2022     15-04 - Rear Spar Assembly - (36.1 hours)       Category: 15 Rear Spar

Initial Prep (Debur, Trim, Drill, and Cut)
1/4/22 – 0.6h
2/18/22 – 2.1h
2/19/22 – 1.8h
2/23/22 – 1.6h
2/27/22 – 1.2h
3/1/22 – 0.9h
3/2/22 – 1.0h
3/4/22 – 0.4h
3/18/22 – 1.0h
Rear spar assembly starts with some final part preparation including straightening the rear spar reinforcement fork and the rear spar doubler plate. I went back to my method of bridging the part bow side up across a couple small pieces of wood trim, and then applying pressure with a c-clamp at the middle of the bowed area to straighten the part. This process goes pretty quickly, and is very controllable to get a uniformly straight part. The individual parts, including the doublers from the previous step, are cleco'd to the rear spar to final drill all of the common attach holes. There are also 6 holes through the reinforcement fork to final drill through the spar and rib flanges. After all the parts are drilled and countersunk (see below), it's time to disassemble and debur.
[C-Clamp, #30 Drill, Hole and Edge Deburring Tools}

Final Prep (Dimple, Countersink, and Shape)
2/26/22 – 1.7h
2/27/22 – 0.7h
3/5/22 – 1.5h
The rear spar has a few holes to countersink including the bottom holes in the rear wing attach doubler plate and the top flanges common to the rear spar doublers. I started with the #30 holes in the wing attach doubler plates. The bottom six holes are countersunk to fit the head of a NA426AD4 rivet, and the six holes above them are countersunk for a dimpled 0.020” skin (about .005” deeper). The final countersunk holes are the #40 holes in the flange of the rear spar that correspond to the 3 doublers.

The holes in the top and bottom flanges of the rear spars are dimpled where there are no countersinks. I wanted to use the C-Frame to dimple the holes, but that was impractical do to the length of the rear spars. I used the pneumatic squeezer for the dimples with good results.
[#30 Countersink Cutter and Microstop Countersink Cage, #40 Countersink Cutter and Microstop Countersink Cage, Pneumatic Squeezer, Reduced Diameter 3/32 Dimple Die)

Edge Forming Tool (Vise Grip Style), Hole and Edge Deburring Tools, 22” C-Frame with #40 Reduced Diameter, #30, and #40 Standard Diameter Dimple Dies, Pneumatic Squeezer with #40 Reduced Diameter Dimple Die]

Prime
3/4/22 – 0.9h
3/6/22 – 1.3h
3/18/22 – 0.4h
3/19/22 – 2.0h
The final step of preparing parts for assembly is priming. I did the priming in phases as I finished individual parts. I liked breaking this task up into smaller sessions than one or two really long sessions. It also helped me keep parts for the left and right spars separate and marked properly.
[Grey Scotchbrite Pads, Bon-Ami Cleanser, Dupli-Color Degreaser, Dupli-Color Self-Etching Automotive Primer (Green – Rattle Can)]

Assemble
3/14/22 – 0.8h
3/19/22 – 3.3h
3/20/22 – 4.8h
3/21/22 – 1.1h
3/22/22 – 1.1h
3/23/22 – 1.0h
3/24/22 – 1.0h
3/26/22 – 3.9h
Assembly of the rear spar looks deceptively simple in the plans. First you rivet six parts onto each rear spar, then you rivet the rear spars to the ribs. No problem! In reality, it is a little more complex than that. One question was orientation of the rivets. Van's doesn't specify, which means it is builders choice. Conventional practice is to put the manufactured head of the rivet on the side with the thinnest part, which would be the forward side (inside) of the spar for the thick doublers and reinforcement fork and the aft side (outside) of the spar for the thin outboard doublers. I looked at several pictures on-line to see what other builders did, and I tried to find clear pictures of how the quick-build wings are assembled. It looked like the quick-build wings put all the rivets with the manufactured head on the aft (outside) side of the spar, and several builders did that as well. That was also the approach I took to ensure maximum clearance later for flaps and ailerons, to make it easier to remove rivets (if needed), and for the aesthetic.

The far outboard doubler plate went quickly with the pneumatic squeezer. Pay attention to the holes that do not get riveted and there won't be any problems. The two doubler plates in the center of the spar are a little trickier because you also have to skip the holes where the spar will be riveted to the ribs later. It is really difficult to see which holes to leave empty in the overview diagram of the wing, so I found a better picture of the rib-spar connection in the bottom skins section of the plans. I used that picture to count holes in the bottom flange of the spar to find the one that aligns with the rib for the outboard doubler. It is the row right next to the hole for the aileron pushrod. After counting holes, I noticed in the plans that the row I identified for the rib gets a different length rivet than the other doubler holes (duh!). That confirmed I had the right location to tape off. The rib locations on the reinforcement fork and inboard doubler were more obvious.

The pneumatic squeezer does a good job with most of the rivets, but there are a few areas where clearance is too tight and I had to go to the rivet gun and bucking bar. Specifically, the rivets to attach the flanges of the aileron hinge to the spar are very tight. Similarly, can't get into the area cleanly for the bottom hole on the rib next to the aileron hinge because the hinge is in the way.
[Pneumatic Squeezer, 1/4" Cupped Squeezer Set, Flush Squeezer Set, 3x Rivet Gun, 1/4" Cupped Rivet Set, Tungsten Bucking Bar]

  Mar 15, 2022     15-03 - Rear Spar Doublers - (12.7 hours)       Category: 15 Rear Spar

Initial Prep (Debur, Trim, Drill, and Cut)
1/26/22 – 1.4h
1/28/22 – 1.3h
1/29/22 – 2.7h
2/14/22 – 1.1h
2/15/22 – 2.9h
3/4/22 – 2.1h
3/15/22 – 0.2h
Each rear spar has three flat plate doublers where the aileron hinges and outboard flap hinge attach. Preparing the doublers includes match drilling them to the rear spar and cutting the aileron pushrod hole in the W-1007D outboard doubler. I started cutting the pushrod hole by using an old geometry class template to find a circle with the correct diameter to match the rounded corners of the hole. I planned to use the step drill to remove the material up to that diameter. This approach cleanly removed a lot of the material, but there was still some that had to be removed another way. I used a combination of Dremel grinding wheels, files, and deburing tools to get to the final shape and size of the hole.

The final task for this step is to final drill the rear-spar attach hole in the Rear Spar Doubler Plate. This is a critical hole (it is where the wing aft spar attaches to the fuselage) and should be drilled with a drill press. After the hole is drilled to 11/32”, it is attached to the Rear Spar Reinforcement Fork and the holes in both parts get reamed to 3/8”. I decided to final drill the Rear Spar Doubler clecoed and aligned with the Rear Spar Reinforcement Fork to ensure the holes aligned correctly. The manufactured hole in the fork is just slightly larger than 11/32”, and worked really well to help center the bit for the hole in the doubler plate. I then left the parts clecod together and clamped in the drill press, swapped over to the reamer, and reamed both holes together. The result was excellent, and I feel really good that the holes are aligned, straight, and sized very precisely. There shouldn't be any problems when I eventually attache the wings to the fuselage!
[Cleco Clamps, #30 Drill, #40 Drill, 11/32” Drill, 3/8” Reamer, Flat and Round Files, Hobby Files, Dremel with Metal Cutting Disk and Grinding Stones, Step Drill, Hole and Edge Deburring Tools]

Prime
2/10/22 – 0.5 hours
2/16/22 – 0.5 hours
[Grey Scotchbrite Pads, Bon-Ami Cleanser, Dupli-Color Degreaser, Dupli-Color Self-Etching Automotive Primer (Green – Rattle Can)]

  Mar 14, 2022     15-02 - Aileron Hinge Bracket Assemblies - (19.9 hours)       Category: 15 Rear Spar

The plans for this step have some changes to accommodate Service Bulletin SB-16-03-28. The SB deals with cracking of the aft wing spar web at the inboard aileron hinge bracket attach rivets and bracket flanges in all of the RV models except the RV-12. The SB replaces the original inboard hinge brackets with newly designed hinge brackets, and the new brackets are installed with additional doublers on the spar web. The SB was intended to repair flying airplanes with the cracking problems and to prevent the issue with new builds. The SB replaces step 3 on this page, which is the build-up of the inboard aileron hinge bracket assemblies (W-1013-L & R). The original design is still used for the outboard hinge bracket assemblies (W-1014-L & R). Step 4 on this page stays the same to build-up the outboard hinge bracket assemblies, and steps 5 – 6 apply to both inboard and out-board. The other thing to note on this page is that the aileron stop tab on hinge bracket spacers for the outboard assemblies is trimmed off, and it remains in place for the inboard assemblies. Steps 15-28 in the SB contain the details on preparing, building, and installing the inboard aileron hinge brackets.

Initial Prep (Debur, Trim, Drill, and Cut)
1/23/22 – 2.9h
1/24/22 – 1.8h
3/13/22 – 1.3h
The aileron hinges are built up from relatively thick parts with a lot of tool marks on the edges to debur. The parts have mainly long straight edges, which makes the deburring process easier. The plans call for final drilling all of the holes common to the hinge parts, which are all easy to access. The inboard aileron hinges have long and short sections of aluminum “L” channel that form the flanges of the parts. The long piece extends above the inboard hinge parts, which is trimmed along the angle of the hinge bracket and deburred. The outboard hinges have three pieces sandwiched together, and the aileron stop is cut off.
[Hole and Edge Deburring Tools, Dremel with Metal Cutting Disk, #30 Drill]

Final Prep (Dimple, Countersink, and Shape)
1/6/22 – 1.3h
1/7/22 – 3.5h
1/25/22 – 1.6h
The hinge bracket spacers can warp slightly when they are manufactured. I straightened them as well as I could using a combination of hand pressure and pressure from a table clamp. The clamp method works by elevating the piece off the table with small wood blocks at each end, and then using the table clamp in the center of the piece to bow it down. The hinge bracket spacers are short parts, and very sensitive to the amount of pressure used in the center to straighten them. They are also triangular-shaped parts, so I straightened each edge in turn until the whole part would lay flat on the smooth marble surface.

Each aileron hinge – both inboard and outboard – has holes near the hinge point that are countersunk for flush rivets. The holes are countersunk on the sides that will face the aileron to provide clearance when the aileron is installed. The microstop countersink cage with the #30 countersink cutter works well until you get to the flanges of the inboard hinges. The countersink cage is too large for that area, and I ended up “free handing” those holes. They actually came out pretty good by going slow and checking the depth often. I made one countersink about .003 - .005 too deep, but that should still be useable.
[Wood Blocks, Table Clamps, Flat Marble Surface, Flat File, Band Saw, Bench Grinder with 6” Scotch Brite Wheel, Microstop Countersink Cage, #30 Countersink Cutter]

Prime
2/16/2022 – 1.2h
2/20/2022 – 1.7h
3/13/22 – 0.7h
[Grey Scotchbrite Pads, Bon-Ami Cleanser, Dupli-Color Degreaser, Dupli-Color Self-Etching Automotive Primer (Green – Rattle Can)]

Assemble
2/21/22 – 3.2h
3/14/22 – 0.7h
The outboard hinge brackets are essentially a thick center piece sandwiched between two thinner edge pieces. The thick center piece also holds the aileron attach bearing. The bearing is pressed into the center piece with a bench vise and a couple of sockets, then the outer layers of the sandwich are riveted into place. Assembly of the outer hinge brackets went well, and the brackets are on the shelf to be attached to the rear spar in a later section of the plans.

The inboard hinge brackets didn't go quite as planned. The inboard brackets are made from two thick parts that hold the aileron attach bearing between them, and then two “L” brackets which make the flanges to attach the hinge bracket to the rear spar. The two primary pieces went together very well with the squeezer, and the ends holding the aileron bearing are tight against each other. I then attached the long “L” bracket to the top of each hinge bracket. Everything to this point came out fine, but somehow I swapped the left and right short “L” brackets which make the inboard flanges. I noticed the mistake when I tried to test fit the completed hinge brackets to the rear spar, and the holes did not line up! I drilled out the six (three on each assembly) AN426AD4-11 rivets and removed the short “L” brackets. These are very long rivets, and I damaged the ”L” brackets when I removed them. The rest of the assemblies look fine, but I need to order new “L” brackets to finish the assembly (sigh). I received the new “L” brackets from Van's, which I successfully prepped and attached to the hinge brackets correctly.
[Pneumatic Squeezer, 1/8” Cupped Squeezer Set, Flat Squeezer Set, Bench Vise, 7/16 and 9/16 Sockets]

  Feb 20, 2022     15-01 - Rear Spar Preparation (Plans) - (1.5 hours) Category: 15 Rear Spar

1/15/2022 – 1.5 hours
The rear spar section of the plans is deceptively short and simple. There are only four sheets and fewer than 10 parts for each rear spar. There are, however, several things going on. First, there is a Service Bulletin from March 2016 regarding “Cracking of wing aft spar web at the inboard aileron hinge bracket attach rivets.” The SB parts kit is shipped with the wing kit, and it essentially replaces the original inboard aileron brackets. The plans have not been updated with the instructions for the SB, so you have to be aware of which aileron hinge bracket (inboard or outboard) you are working on and use the plans or SB instructions as appropriate. Another item I noted was drilling the rear wing attach bolt hole through the rear spar doubler plate and rear spar reinforcement fork. This is a critical hole that must be drilled and reamed with a drill press and appropriately sized bits – 11/32 drill bit and 3/8 reamer. I had to order the drill bit and reamer since they were not already part of my tool kit. The final thing that caught my attention was outboard doubler plate, which needs to be match-drilled (like the rest of the doubler plates) to the rear spar and then machined to put a hole for the aileron control pushrod through the doubler that matches the hole in the rear spar. The hole is not round, so this is more than simply using a step drill.