Apr 21, 2024     25-06 - Bulkhead Reaming - (0.5 hour)       Category: 25 Mid-Fuse

Final Prep (Dimple, Countersink, and Shape)
04/21/24 – 0.5h
The final step in this section is to ream a handful of holes from the forward and aft center bulkhead assemblies through bulkhead webs and side angles. The instructions laid out a specific process to complete this task, which worked well. My only addition to the procedure was to use a Drill Guide to help ensure no side loads on the holes during the reaming process.
[.311 Reamer, .375 Reamer, Drill Guide]

  Apr 20, 2024     25-05 - Forward Center Section Bulkhead - (9.8 hours)       Category: 25 Mid-Fuse

Initial Prep (Debur, Trim, Drill, and Cut)
3/9/24 – 1.3h
3/12/24 – 1.2h
3/13/24 – 0.9h
This step starts with two pieces that are split apart to make a total of four parts. I separated the parts for this step when I separated parts in the first step of this section. The band saw made quick work of separating all of the parts for this section. Fine-tuning the parts with files and grinder wheels, followed by deburring, yielded nicely finished parts.
[Hole and Edge Deburring Tools, Band Saw, Flat File, Bench Grinder with 6” Scotch Brite Cut and Polish Wheel, Dremel with Metal Cutting Disk]

Final Prep (Dimple, Countersink, and Shape)
3/14/24 – 0.3h
3/23/24 – 0.3h
Most of the final prep was countersinking holes in the top and bottom flanges of the Forward Center Section Bulkhead. The #40 holes in the top flange are countersunk for rivets to attach nut plates. The #30 and #40 holes in the bottom flange are countersunk to accept dimples in the bottom fuselage skin. There are also three holes in each bearing bracket brace to countersink prior to attaching the bearing bracket angles.
[#30 Countersink Cutter, #40 Countersink Cutter; Microstop Countersink Cage]

Prime
3/14/24 – 0.4h
3/23/24 – 0.1h
[Grey Scotchbrite Pads, Bon-Ami Cleanser, Dupli-Color Degreaser, Rust-Oleum Automotive Self Etching Primer (Green – Rattle Can)]

Assemble
3/23/24 – 0.2h
3/25/24 – 1.1h
4/15/24 – 0.6h
4/19/24 – 0.6h
4/20/24 – 2.8h
The two bearing brace assemblies are each made by riveting a bearing bracket angle to the end of a bearing bracket brace. The bearing brace assemblies are installed between the two inboard cover ribs on each side of the airplane, and provide a rigid structure for the bearing brackets attached to the cover ribs.

I installed the nutplates to the top flange of the Forward Center Section Bulkhead at the same time as I did the Aft Center Section Bulkhead. I was in nutplate mode, and this was an efficient way to quickly complete both. I hung the spar from the edge of the workbench, clamped it securely in place, and used the pneumatic squeezer with flat sets to set the rivets for the nutplates.

Attaching the side angles to the forward bulkhead was similar to the process used on the aft bulkhead. The side angles have one bolt installed at this time near the top of the bulkhead, and rivets in the top and bottom most holes help keep things aligned. Clecos do the rest to hold everything together during riveting. Like before, I used the C-Frame for the universal head rivets with excellent results.

The final assembly step was attaching the cover ribs and bearing brace assemblies to the Forward Center Section Bulkhead. I started by inserting bolts in the top and bottom holes of the cover ribs, and then ensured the ribs were aligned using rivets in the remaining top and bottom holes prior to tightening the nuts to the final torque. The easiest setup for me to install the bolts and rivets was to lay the bulkhead across two saw horses with the cover ribs hanging down. I set all of the rivets on the cover ribs with the pneumatic squeezer, but had to use varying yoke sizes to get clean looks at each rivet through the bulkhead lightening holes.

After the cover ribs are completely installed, this step is finished with the attachment of the bearing brace assemblies to the cover ribs and bulkhead. I started by attaching the bearing brace assemblies to the cover rib with the bearing bracket by installing two structural screws with washers and nuts in each. I used the torque wrench set to 25 in-lbs to torque the nuts on the screw. There are 2 rivets opposite the screws that get set next. The pneumatic squeezer did a nice job with these, but clearance on the rivet closest to the bulkhead is very tight. I set the final three rivets in each assembly to the bulkhead with a rivet gun and bucking bar. One note on the final three rivets - they are longer than the rivets used to attach to cover ribs to the bulkhead. The rivet size is specified in the drawing, but it is easy to overlook. I figured it out after using the shorter rivet and noticing that the shop head was not formed correctly. I drilled out the short rivet, and continued with the longer rivets - all good!
[Pneumatic Squeezer, 1” Yoke, 2 1/2" Longeron Yoke, 3” Yoke, Flat Squeezer Set, Torque Wrench, C-Frame, Cupped Set, 3x Rivet Gun, Long Cupped Rivet Set, Tungsten Bucking Bar]

  Apr 19, 2024     25-04 - Cover Ribs - (7.2 hours)       Category: 25 Mid-Fuse

Initial Prep (Debur, Trim, Drill, and Cut)
4/7/24 – 3.0h
This step is all about preparing the cover ribs that attach to the forward side of the forward center section bulkhead. I waited to start this step until the replacements for my laser-cut cover ribs arrived from Vans. Vans recommended replacement of the cover ribs since the center two ribs on both the left and right sides of the airplane support the control sticks, which means lots of cycles and additional loads.
[Hole and Edge Deburring Tools]

Final Prep (Dimple, Countersink, and Shape)
4/7/24 – 0.5h
One cover rib each on the left and right side is prepared a little differently than the other six. The different cover ribs have three nutplates on the top flange, and are used to mount the bearing brackets built in the previous step. Most of the #40 holes in the top, forward, and bottom flanges of all eight cover ribs are dimpled, and the holes that are not are clearly marked in the plans drawing.

The top flange of the left and right cover ribs that are different from the rest have two #19 holes that are drilled #17 and dimpled for.a #8 screw. Due to the large dimples in the top flanges of these two ribs, a relatively small forward flange near the bottom of the cover rib, and the close proximity of several #40 holes, I went with a reduced diameter #40 dimple die. The reduced diameter cleared the large dimples, small flanges, and adjacent close holes, and is definitely the way to go to avoid damaging the part.
Pneumatic Drill, #17 Drill Bit, Pneumatic Squeezer, #8 Screw Dimple Die, #40 Reduced Diameter Dimple Die]

Prime
4/7/24 – 0.6h
4/8/24 – 0.5h
4/10/24 – 0.5h
[Grey Scotchbrite Pads, Bon-Ami Cleanser, Dupli-Color Degreaser, Rust-Oleum Automotive Self Etching Primer (Green – Rattle Can)]

Assemble
4/10/24 – 1.7h
4/19/24 – 0.4h
This step doesn't have much in the way of assembly - attach a few nut-plates and a couple bearing brackets to the cover ribs. There are, however, some assembly considerations during this step.

First, the top flange of each cover rib gets nutplates attached. Most cover ribs get two nutplates - one near the forward end of the flange and one near the aft end of the flange. Two cover ribs get three nutplates, which are different than the ones used on the other cover ribs and are relatively close together. For these cover ribs, I started with the nutplate in the center, then moved to the forward and aft nutplates. Pay attention to the rivet specs, the length changes depending on the nutplate that is getting attached. I found the pneumatic squeezer with a short yoke did a really good job setting the rivets on the all the nutplates on all of the cover ribs.

The second assembly step is to rivet the bearing brackets to the cover ribs with the 3 nutplates on the top flange. I switched to a longer 3” yoke to provide better access to the rivets, and used the pneumatic squeezer to set these rivets, too. The rivets are long (AN426AD4-8) because the bearing brackets are relatively thick. I had to use thin squeezer sets to give the pneumatic squeezer enough clearance to set the rivets. Another option that I used on the second bearing bracket was to back rivet the bearing assembly to the cover rib. That also worked really well, but one rivet still had to be squeezed because it is just too close to the two adjacent rivets for the back rivet set to fit.

The thing that jumped out at me during this process is the large number of AD4 rivets used to attach bearing brackets to one left and one right cover rib. There are a total of eight rivets that are closely spaced on this fairly small part. The bearings will support the control sticks, and need to be strong to avoid a control issue in flight. Given the loads and loading frequency on the bearing brackets, braces, and cover ribs; it makes sense that these parts are made from thick pieces of aluminum, anchored with lots of rivets and screws to multiple cover ribs and the bulkhead, and that Vans replaced the laser cut cover ribs with punched parts to avoid potential part cracking and failure issues.
[Pneumatic Squeezer, 1” Yoke, 3” Yoke, Flat Squeezer Sets, Small Back Rivet Plate, 3x Rivet Gun, Back Rivet Set, #19 Drill]

  Apr 05, 2024     25-03 - Aft Center Section Bulkhead - (8.3 hours)       Category: 25 Mid-Fuse

Initial Prep (Debur, Trim, Drill, and Cut)
3/3/24 – 1.1h
This is the first of two steps to prepare the aft-center and forward-center bulkheads. Eventally, these two bulkheads will sandwich the wing spar to attach the wings to the fuselage. The two bulkheads are prepared (alodined and critical/large rivets set) and delivered just like the wing spar. This step is focused on the aft-center section bulkhead. There aren't many parts for this step, so initial prep goes pretty quickly. [Hole and Edge Deburring Tools]

Final Prep (Dimple, Countersink, and Shape)
3/6/24 – 0.8h
3/8/24 – 0.3h
3/9/24 – 0.2h
3/23/24 – 0.4h
Every part in this step has holes to countersink. I hung the bulkhead from the edge of the work bench and secured it with clamps to countersink the flanges. This technique kept the work at bench level, and was more secure than clamping the bulkhead to the top of the bench. I countersunk the top flange holes for flush rivets to attach nut plates, and flipped the bulkhead over to countersink the bottom holes for the bottom fuselage skin dimples. The guideline to go 0.007” (seven clicks) deeper for the dimpled skin countersinks than the flush rivet countersinks worked well for me.

Each side angle gets two countersunk holes in the web of the angle. Take time to study the drawings to identify the correct two holes. The other parts in this step are the bearing bracket assemblies. There are two bearing bracket assembly drawings on the sheet for this step. At first glance, I didn't notice a difference, but upon closer inspection the drawings are mirror images of each other - one is for the right assembly and one is for the left. I started with the #40 holes, and had some problems countersinking the forward-most holes in the bearing brackets. The holes are very close to some irregular shaped edges, and there wasn't enough surface to hold the countersink cage square to the hole. The result was a couple of bad countersinks and a trip to the Vans webstore to purchase some more. The bearing brackets will eventually carry loads from the control sticks, so it's worth it to make sure these are prepared and assembled correctly to preserve their strength.

After I sorted out the #40 holes in the bearing brackets, I moved on to the #30 holes. This is where the left and right assembly drawings matter. The exterior sides of the #40 holes are countersunk in both the inboard and outboard parts for double-flush riveting. The #30 holes are only countersunk in the outboard part of the assembly. Countersinking the #30 holes went smoothly - no issues like I had with the #40 holes.

The bearing brackets also have two #19 holes that are countersunk for the head of AN509-8R12 screws. Like the #30 holes, the #19 holes are only countersunk on the outboard side of the assembly. I countersunk the #19 holes by hand using a hole deburring handle with the #19 countersink cutter attached, and inserting the deburring tool into a 5/8” drill guide to keep it square with the part. The bench setup for this technique took a little thought, but ultimately worked out well. I deburred each hole slowly, regularly checking the depth with a screw head. A little care and patience resulted in really good countersunk holes.
[#30 Countersink Cutter, #40 Countersink Cutter; Microstop Countersink Cage; Electric Drill, #19 Countersink Cutter; Deburring Tool, Drill Guide]

Prime
3/8/24 – 0.2h
3/9/24 – 0.9h
3/12/24 – 0.3h
3/23/24 – 0.1h
Priming followed my standard process of scuffing, cleaning, degreasing, and priming parts after they are fully prepped and ready for assembly. In addition, I used a Q-Tip to prime the holes that had been countersunk in the aft-center bulkhead flanges.
[Grey Scotchbrite Pads, Bon-Ami Cleanser, Dupli-Color Degreaser, Rust-Oleum Automotive Self Etching Primer (Green – Rattle Can)]

Assemble
3/17/24 – 0.5h
3/24/24 – 2.4h
4/5/24 – 1.1h
The first assembly step was installing the nutplates to the top flange of the aft-center bulkhead. Once again, I hung the spar from the edge of the workbench and clamped it securely in place. I then used the pneumatic squeezer with flat sets to set the rivets for the nutplates.

Attaching the side angles came next. The instructions specify inserting 4 AN-6 temporary bolts through the side angle and spar webs. I decided to get some 5/8” bolts at the hardware store for this, so I wouldn't damage the AN-6 bots and nuts that will be used for final assembly. I started riveting with the 2 flush AN426 rivets. That allowed me to back-rivet with a small back-rivet plate before the universal head rivets were in the way. From there I switched to the C-Frame for the universal head rivets using the same technique as the previous step.

The bearing bracket assemblies, which had counter-sinking issues earlier, also had some riveting problems that led to yet another trip to the Vans webstore for replacement parts. The first issue is the AN426AD3-7 rivets specified for the bearing brackets are too long to double-flush rivet. The shop head complete fills the countersink and leaves a significant tail that has to be filed flush with the bracket. I used 3-6 rivets during my second attempt, which worked much better. The 3-6 rivet still leaves a tail, but it is much shorter and easier to file flush. The other gotcha is the riveting method. I chose back-riveting with the part securely clamped to a small back-rivet plate. This method works well as long as you account for the actual bearing that sits just proud of the bracket. In other words, the assembly has to be clamped to the back-rivet plate in a way that allows complete back-riveting without affecting the bearing. I didn't account for that correctly the first time and the result was a very stiff bearing sandwiched inside the bearing bracket assembly. I ended up removing the rivets to pull the assembly apart and inspect the bearing. The bearing was fine, and moved freely and smoothly outside the bearing assembly. I was more careful with the bearing placement relative the back-rivet plate for the second attempt, and the bearing now moves freely in the assembly.
[Pneumatic Squeezer, 1” Yoke, 3X Rivet Gun, Back Rivet Plate, Back Rivet Set, C-Frame, Cupped Set]

  Apr 04, 2024     25-02 - Bulkhead Bottom Channel - (11.9 hours)       Category: 25 Mid-Fuse

NOTE: This step contains several laser-cut parts that Van's determined should be replaced. Therefore, I will only be able to prep the punched parts in this step for now. I will finish the parts prep and assemblies when Van's sends the replacement parts to me.

The laser-cut replacement parts arrived on 3/28/24! I got quite a bit done in several steps while waiting for them, and the shipment of replacement parts timed out well to keep the build sequence on track. I'm back into full-on build mode :).

Initial Prep (Debur, Trim, Drill, and Cut)
2/26/24 – 0.8h
2/27/24 – 1.0h
3/2/24 – 1.1h
3/3/24 – 0.3h
3/29/24 – 1.9h
A few parts in this section, including the bulkhead bars for this step, are manufactured from a single piece of aluminum and have to be separated. I set up the bandsaw and separated all of the parts for the mid-fuselage bulkhead section. After the standard hole and edge deburring of all the parts for this step, I skipped forward a bit to complete the bulkhead bar assemblies. I bought a handful of 3/8” bolts and nuts at the hardware store, and used those to temporarily bolt the bulkhead bars together, I then inserted a 3/8” bolt with 1/4" worth of nylon and metal washers into the outboard-most hole of the bulkhead bars to prepare for double-flush riveting later in this step.
[Band Saw, Flat File, Hole and Edge Deburring Tools]

Final Prep (Dimple, Countersink, and Shape)
3/3/24 – 0.4h
3/22/24 – 0.1h
3/31/24 – 0.4h
The two pairs of F-01405B Bulkhead Bars are assembled by double-flush riveting them together before they are bolted to the Bulkhead Bottom Channel and eventually bolted to the rear spar of each wing. The plans make it very clear that the bars are to be double-flush riveted, but the plans omitted the step to countersink the holes for the rivets flush on the exterior surface of each of the bulkhead bars. It's been awhile since I've done any countersinking, but the eight countersinks (two on the exterior face of each bar) went well.

After the bulkhead bar assemblies are riveted together, the outboard hole that attaches to the bulkhead bottom channel is reamed to final size with a .311” reamer. The plans recommend using a drill press at low speed for reaming whenever possible. That is certainly an option for this hole, but is more problematic as the bulkhead assembly comes together and is more difficult to position and secure for drilling. I decided to use an electric hand drill and drill guide with a 5/16” guide hole to ream all of the holes in this step. I found that to be a really good technique to keep the drill square with the holes, while maintaining flexibility to reposition for other holes relatively quickly.

The other final prep operation in this step is dimpling the outboard holes on the side channels and the bottom flange holes in the bulkhead bottom channel. The drawings for this step clearly outline the #40 holes in the side channel that are not dimpled as well as the 3 #30 holes in the side channel that are dimpled. The pneumatic squeezer clamed to the work bench with standard diameter dimple dies did a nice job with the dimples.
[#30 Countersink Cutter; Micro-stop Countersink Cage; Electric Drill; 0.311 Straight Flute Reamer; Drill Guide; Pneumatic Squeezer, #30 and #40 Standard Diameter Dimple Dies]

Prime
3/3/24 – 0.3h
3/12/24 – 0.2h
3/31/24 – 0.6h
Priming followed my standard process of scuffing, cleaning, degreasing, and priming parts after they are fully prepped and ready for assembly.
[Grey Scotchbrite Pads, Bon-Ami Cleanser, Dupli-Color Degreaser, Rust-Oleum Automotive Self Etching Primer (Green – Rattle Can)]

Assemble
3/16/24 – 0.9h
4/3/24 – 2.4h
4/4/24 – 1.5h
I started the assembly step with double-flush riveting the bulkhead bars to make bulkhead bar assemblies for the port and starboard sides of the bulkhead. As mentioned above, I prepared the bulkhead bars by countersinking the exterior face of the rivet holes. I used a small back-rivet plate and back-rivet set in the rivet gun to do the double-flush riveting. I found that the shop-head side of the rivet was not quite flush when the rivet was set, so I filed the shop-head side down flush with the face of the bulkhead bar and reprimed that area. The result was flush and tight rivets on both sides of the bulkhead bar assemblies.

The remainder of the riveting for this step used AN470 rivets, so back-riveting on a plate was not an option. Most rivets are also out of reach for a squeezer, so this became an opportunity to try a different riveting technique. I've primarily used my 22” C-Frame for dimpling, but it can also be used to set rivets. For this step, I inserted a 1/8” cupped set in the base of the C-Frame and a flat set in the C-Frame ram/arbor, which was attached to the 3X rivet gun. I used some scrap lumber to level the parts with the cupped set in the C-Frame, inserted the rivet, aligned it with the C-Frame cupped set, and set the rivet. This technique worked really, really well. All the rivets were set successfully with no re-dos and no “smiles”. I definitely recommend this technique to everyone who has access to a C-Frame. There are a couple of things to consider, though. First, my cupped set, which I also use with the pneumatic squeezer, is now a permanent attachment to the C-Frame die holder. All of the rivet hits and pressure on the set and holder made it impossible to separate the tools, and I had to buy a new cupped set for my squeezer and a new die holder for the C-Frame. The flat set in the C-Frame arbor also needed to be replaced. The stem of the flat set broke off inside the arbor, and there is no way to get it out. The flat set still works with the arbor, but nothing else will fit. Once again, a quick visit to the aviation tool supplier was needed for a new arbor and flat set. Even with the tool issues, riveting with the C-Frame was totally worth it!

The final task in this step is to ream the bolt holes in the bulkhead and bulkhead bars, and install the bolts that attach the bulkhead bar assemblies to the bulkhead. The directions on the order to ream the holes makes a lot of sense when you're actually completing this step. First you ream the outboard holes in insert that bolt, then secure the bulkhead bars in place with a cleco (a bit difficult since the cleco hole in the bars and the bulkhead didn't align very well), ream and bolt the inboard holes, then finish by reaming and bolting the two center holes. Once again I used the electric drill on low speed and the 5/16” drill guide to keep things aligned during the reaming process. The AN5 bolts, washers, and nuts are installed with a torque wrench set to 100 – 140 in-lbs (I used 130 in-lbs based on a 15 in-lb drag measurement). Pay attention to the drawings in the plans – the inboard bolts use three washers, and the outboard bolts only use two.
[Pneumatic Squeezer, 1” Yoke, 3X Rivet Gun, Back-Rivet Set, Back-Rivet Plate, 22” C-Frame, Cupped Set, Flat Set, Torque Wrench, 1/2” socket]

  Feb 25, 2024     25-01 - Forward Mid-Fuselage Bulkheads (Plans) - (2.5 hours) Category: 25 Mid-Fuse

2/25/24 – 2.5h
It's time to start working on the fuselage kit! I received the fuselage kit nearly a year ago (March 30, 2023), and I put all the parts in temporary storage after completing the inventory and initial sorting. Finishing the wings took longer than I had planned for, but it turns out the delay on starting the fuselage kit worked out for the best.

Vans is working through a number of issues right now that affect my build. The Chapter 11 bankruptcy and business reorganization delayed delivery of my finish kit, which gave me time to finish the wings and start the fuselage without being rushed by another kit coming in. The finish kit was planned for crating and delivery in March/April 2024, but that date is likely slipping due to the company reorganization efforts. I have re-ordered the kit at the new (higher) prices and I hope Vans is able to get it out soon.

The second issue at Vans that affects my fuselage build is the inclusion of laser-cut parts in my fuselage kit. Vans has analyzed the inventory of laser-cut parts to determine their service lives, and categorized each part to either be replaced or used as is. In my case, 32 parts need to be replaced, including several used in this first step. I've ordered the replacement parts, and Vans is working through the orders to get parts shipped. Once again, my delayed start on the fuselage kit worked to my benefit. I don't have to re-do a lot of steps to remove and replace laser-cut parts that have already been assembled. The down-side, of course, is that I'm limited in what I can do now while I wait for the replacements.

The delay and issues at Van's resulted in other changes that I'll need to work through as part of the fuselage build. One of the biggest changes is the landing gear parts are now delivered with the fuselage kit and not the finish kit. My fuselage kit was delivered before that change took effect, so I have to work with Vans to get the landing gear parts with my finish kit as originally planned.

I stumbled across another change while reviewing the service bulletins, notifications and letters, and revisions and changes in the Service Information and Revisions section on Van's Website. Seven chapters in the build instructions, including this one (chapter 25), were updated last week (February 15th, 2024) for a flap motor update. The updated flap motor was not delivered as part of my fuselage kit, so it's time to get with Van's to see if I can return the motor I received for a credit on the new one, and also to see if I can get updated plans. It appears the only change to this chapter of the plans is the reference to the Mid Fuselage Brace as F-01405F-1 instead of F-10405F on sheets 25-01 and 25-02. This part is not permanently assembled in this step – just temporarily cleco'd in place to help brace and align other parts that are riveted and bolted together in this step of the build. I reviewed plan OP-65, RV-14 Flap Motor Retrofit to see if I could find the difference in the “dash 1” version of F-01405F-1. The difference is the gap in the flange of the F-01405F Mid Fuse Brace has been widened by 3/32” on each side (total 3/16”) to provide clearance for new Flap Motor Brackets. It doesn't look like the change will appreciably affect section 25 of the build, but it is definitely something that has to be addressed as the flap motor and housing come together in later steps.

*****
UPDATE: I asked Van's technical support about the flap motor retrofit, and the implications for my build. The short answer from Van's is the ES 85615-10 linear actuator supplied with my fuselage kit will “give you years of trouble free service” and the ES-FA-PA-270-12-5 Flap Motor is provided as a retrofit kit if the supplied flap actuator needs to be replaced in the future. I plan to go with the motor and parts I have, and ignore the plans updates that apply to the retrofit kit.
*****

The Section 25 plans don't appear to contain any new build techniques with the exception of several holes that are reamed .311 in the assemblies. The plans recommend reaming using a drill press set at low speed and lubricant, and cleaning the reamer before every hole. The plans also included the following guidance for best results while reaming:

“Lube the reamer, then insert it into the hole in the bar of the bulkhead assembly.

Begin slowly turning the reamer while pushing it through the web of the bulkhead assembly. Avoid applying any side load.”

Incorrect reaming technique has apparently led to some issues in the build, so I'll take extra care to make sure I get it right. There are also a couple steps for machine countersinking that appear to be missing - notably countersinking the bulkhead bars so they can be double-flush riveted.