I’ve been spending the last few weeks finishing up the tail fairings. Lots of filling and sanding – repeat.
Here is the lower rudder fairing. I sanded off the molding for the tail light and then added some foam, epoxy filler, and a fiberglass layer. This will need some iteration until I’m satisfied.
Also on the bottom of the rudder fairing is a flat spot that needed to be added to allow clearance for the tail wheel. This will also take some additional work to finish off.
The top of the vertical stabilizer also got some filler. This one is close to complete, just another iteration and then I can prime it.
The elevator fairings are done and primed. I’m very pleased with how they turned out. It’s not perfect, but more than good enough until final paint. The horizontal stabilizers also have some final filler added and will be sanded and primed next time.
The whole process involves some West Systems epoxy, cotton flox, 60 grit, 150 grit, and 320 grit sand paper. Lots of sanding.
Tail is almost done done, then I can finish up the remaining fiberglass work on the canopy, and then do the cowl. Things are coming together!
I added some more epoxy and filler to the tail fiberglass tip fairings, and while that was curing I spent some time wrapping up additional finish items.
I started by marking the wing root fairings for a 3/16th” gap. I marked the fairing with some black sharpie, and then used a 3/8″ bolt to score a small line, resulting in a 3/16th” gap from the side of the fuselage. I then removed the fairings from the wings and used my snips to cut back to this line. I then filed this edge to smooth out the cut. After this I installed the rubber seal that will bridge this gap, and reinstalled the fairing to the wings.
After this I spent some time inside the cabin installing support braces for the panel. Originally, the design has two large ribs that extend from the firewall all the way back to the panel through the sub panel, making the entire structure very rigid when riveted all together. With my panel design however, I removed those ribs between the sub panel and the panel so that I can fit all my avionics. As a result, I needed to fabricate some new supports that I can install between the sub panel and panel so as to not lose any rigidity. I fabricated the supports out of some 3/4″ angle stock, and cut to length so I could use my avionics trays as the anchor point on the panel, and then drilled two holes through the sub panel for a screw to hold the supports.
While I was in the cabin, I finished securing all the wiring below the seat floors and in front of the spar. Additionally I also added rubber edging to the fuel line passthrough holes in the sides of the fuselage so the steel braided hoses won’t rub against the fuselage. I will additional silicone tape around the hoses to make an air tight seal (or at least more of a seal).
I also added the four remaining wing spar bolts. They are AN4-13A bolts that are inserted from the aft side of the center-section spar into some nutplates on the wing spar. These bolts are often missed as they are not part of the larger main bolts that go through the entire assembly. (The paint marker got a little runny)
February has been a bit of a slower month in making big progress. I’ve spent a few evenings working on several different things. I got some new shelving units from an old storage unit that my mom was getting rid of, and they sat in the hangar for a few weeks before I finally got some time to assemble them and reorganize a lot of the stuff we have.
I spent an evening with my wife moving the old shelves and workbenches to opposite sides of the hangar, and moved the new shelves to the back wall (they’re much bigger) and just general organizing of tools and parts and a lot of clean up.
We also made a trip to the Container Store and got more plastic boxes for stuff. Its always satisfying when putting things back on shelves and seeing how organized it is at the end.
I came back a few days later and worked through a short to-do list of things inside the plane. I needed to shorten the elevator pushrods so that the bellcrank would rotate aft a small amount. When I pushed the elevator fully forward, it would get a little “squishy” and if I pushed harder, it would then hit the forward (down) stop. I figured the only thing that could be causing this is that I was over rotating the autopilot servo, which is attached to the bellcrank. After shortening the pushrods, I reinstalled everything and tested the forward (and aft) stop, everything hit their stops with no problem or squishiness felt anymore. I then torqued all the bolts and marked them with torque paint.
As I was working on the larger aft pushrod, I noticed that the aft fuselage skin still needed to be riveted. Its the portion right under the empennage, totaling ~50 rivets. I’m surprised I didnt notice this earlier, but It would have been caught when I started doing the fiberglass work on the empennage fairing. I realized I needed to remove the horizontal stabilizer in order to sufficiently gain access to rivet these holes. I proceeded to remove the tail and then riveted the aft skin with no issues and then reinstalled the vertical and horizontal stabilizers.
Now that I have the elevator and rudder off the plane, I will be working on the fiberglass tips.
Now that the wings are installed I spent a couple hours working on some remaining wiring tasks inside the fuselage. I drilled two holes through my center section (with the guidance from this post on vansaircraft.com) in order to route my autopilot and right wingtip lighting harnesses forward of the spar. The left side wingtip lighting harness was routed through an existing hole. I will then connect the wires up to the existing wires that were in place already. I also routed the Fuel Level sensor wires through the sides of the fuselage as well. Once these last few connections are complete, the entire avionics and wiring of the aircraft will be complete.
I also took this opportunity to install my wing-walk grip. I ordered custom skateboard grip tape from www.boardpusher.com, and they turned out amazing! I cut them to final size by laying them on the wing and trimming as necessary.
I came back the next day and began wiring up the lighting harnesses and the roll servo. It was a quick job to splice the wires together and secure the bundle forward of the spar.
I got my wingtips out and propped them up on the wings. I connected the included ZipTip wiring connector and powered up the panel. On first try, the left wingtip taxi and landing light both failed to turn on, while the right side worked nominally. I then began to trace the break in the line, starting with just powering the wingtip with a power supply directly via the wiring harness. I went to disconnect the harness, and one of the ground wires separated from the connector. The ZipTips utilize two grounds – one for landing/taxi lights, and one for nav/strobe. I popped the pin out of the connected, re-stripped the wire and re-crimped a new pin. When I plugged it in, everything worked as expected!
With the panel powered up, I also updated the autopilot servo software to the latest version. When it came back online, I calibrated the servo and verified that everything worked as expected. Its fun to see the autopilot try to maneuver the plane!
After rigging the ailerons and flaps and making sure everything was aligned, I needed to remove the wings one more time in order to finish up some critical items. The to-do list included finishing the Root Fairing seals and drilling two more holes for the Pitot and AOA tubes (for the left wing). The Root Fairing seals have about 20 nut plates that need to be riveted to the wing in order to accept the screws that hold everything together. This required removing the wing so I have access to the inboard rib of the wing to install everything.
A few years back, a fellow builder, Vince, told me about a solo method to remove and install the wings using the wing cradle. If it wasn’t for this guidance It would have been quite annoying to attempt this work by myself. The method involves putting the wing cradle under the wing when its temporarily installed in the plane, and then using some plywood clamped to the cradle to prop the wing up in its final orientation.
I used some scrap plywood my friend Norio gave me, and cut it to size such that when clamped to the cradle, it fit snuggly under the wing. I then clamped everything and tightly as I could. I hopped into the plane and began the painstaking process of removing the bolts that had been temporarily holding the wing on. Its quite a tight and awkward fit, but I managed to remove everything. I then slowly removed the wing while it was held up by the wing cradle. Success!
Once I had the wing off, I began the process of drilling, countersinking, dimpling, and installing the nutplates to the inboard rib of the wing. This was pretty straightforward, nothing too challenging here.
I also used this opportunity to drill two additional holes in the side of the fuselage for the pitot and angle of attack lines. Its all quite a tight fit inside this area, so trying to make sure I had everything lined up appropriately. When I initially installed the lines, I mistakenly cut one of them a couple inches too short. In this pic you can see a short segment that is used to attach everything. After taking this pic I added a longer segment in the wing under one of the access panels (where its easier to work) in order to remove this short segment under the floor pan.
I Also needed to attach the nutplate to the fuel tank bracket. This is an AN4 bolt that will slip away in the event that the wing impacts something, in order to prevent the fuel tank from rupturing to minimize the risk of a fire. The bolt here will be safety wired.
Once I had everything drilled, and all the nutplates installed, I reinstalled the wing. The wing cradle method worked absolutely flawlessly, and makes installing the wings solo completely reasonable. I then installed all of the bolts that hold the wing, as this is the final time the wings will come off!
The next day, I went back to the hangar to repeat the entire process on the right wing. This one took me about 50% less time, which was nice. Now that the wings are permanently installed, I can now wire up the wingtip lights, and autopilot servo, which will close out the two remaining avionics to-do items.
With the wings on the fuselage I got the flaps onto the wings so I could fabricate the flap pushrods. I started by cutting the pushrod stock to length. I then tapped both ends of the rods for 1/4-28 rod-end bearings. The plans call to use a CM-4S bearing.
The problem with this is that because it’s an integrated ball into the bearing, there is no way to prevent this from backing out. The instructions call for locktite to hold it in. I will be changing this out to a CM-4M rod-end bearing with a through bolt that can be safety wired. Its much more secure and safe this way.
But while those parts are on order, I still used the default part to do the initial fitting. I installed it onto the flap and then checked the alignment with the bottom of the fuselage. I then cut the hole in the fuselage that the pushrod passes through
When I installed the bearing into the flap I did not put any spacers, but when I put the update rod end bearing I will be centering the bearing so its not rubbing against the side of the fuselage.
With both flaps on the plane, and aligned I was able to test the deflection of both flaps. Luckily everything was symmetric and the full flap deflection was 45deg. This is above the minimum of 40deg for the RV-7.
With the flaps installed, I then began the aileron aligning. I first began by ensuring the vertical-ness of the control sticks in the plane. When I initially aligned the pilots stick, the copilot stick was inboard by about 6deg. So I adjusted the connecting pushrod so that both sticks were perfectly aligned. It’s hard to see in the pic below, but it says 89.7°, which is close enough for me.
I used a long straight edge to align the aileron with the tooling holes on the outboard rib of the wing (per the instructions) and then ensure that it was aligned with the flaps. I then used the aileron alignment tool to ensure the bellcrank-to-aileron pushrod was the right length, and then, with the control sticks in the vertical position I adjusted the main pushrod. Once the left aileron was adjusted I did the same for the right side. Everything was perfectly aligned to within 0.1deg when comparing everything.
I also got the lower fuselage skins drilled to the wing skins. This has to be done now so that I can remove the wings and install all the nutplates. I also temporarily installed the wing root fairings to drill those as well. They will also be attached with screws through nutplates.
The gap between the fairings and the fuselage will be opened up to 3/16″ and then a rubber seal will be added before permanently reinstalling it.
I also recently saw a modification to the canopy installation that I really liked. Its a modification to the canopy lift struts geometry. I found it through this post (thanks Mike). It had some great guidelines, and only a slight modification was needed for my RV-7 (the post is for an RV-6).
I measured 2″ back from the panel for the forward lift brackets. The canopy brackets were 24″ back from the leading edge of the canopy frame. The struts used are Suspa 23.86″ 20lb struts. I also purchased the brackets from there as well.
The initial fitting took some trial and error, but I got it all aligned and double checked the support capabilities. The entire canopy is very well supported all throughout the closing/opening trajectory. Whats really nice about this geometry is that the canopy is supported by the struts throughout the entire cycle, but with the original geometry there is an over-center position in which the struts begin to pull the canopy down, and it is quite unstable.
Here you can see the original geometry vs the new geometry. One other big benefit to this geometry is the increased entry/exit area.
This weekend I hit a huge milestone – my buddy Norio and I installed the wings on the plane!
We started by first leveling the plane to make sure we had the ability to, as well as thinking it would make sliding the spars into the fuselage easier.
Once the plane was level, we began the process of installing the wing. Once we got the main spar on the left wing mostly installed, we needed to make quite a few adjustments in order for the bolt holes to line up. We eventually got the correct dihedral angle which caused the first bolt to slip in nicely. I kept the bolts in the freezer overnight to help shrink them a little, then applied some lube to aid in the bolt install.
I hopped into the cabin to get the second bolt inserted. It took a bit of coercion, as I think there may be some micro-misalignment with the fuselage structure causing quite a tight fit. I used an alignment pin that I built using some store-bought hardware. it definitely helps to get the spar in the right spot.
Once the second bolt was in, I got out and Norio was able to let go of the wingtip. The plane now had one wing! The whole process for the first wing took about an hour, because there was quite a bit of figuring things out with respect to angles and alignment. After taking a quick break, we jumped onto the second wing. At this point, my wife joined us and helped get the second wing installed in about 20 minutes. It was much smoother.
Once both wings were installed with a couple bolts, we began the rigorous process of measuring wing sweep, incidence, and symmetry. We started by first using a laser level to mark a straight line on the ground spanning the wings, that will be used to measure sweep. We then hung four plumb bobs off the leading edge of the wings and began to align them with the laser line. We also aligned the fuselage longitudinally with the laser, so we could later measure the squareness of the whole plane. At this point, we measured the sweep, and both wings were about 1/4″ swept forward. Van’s calls for fore/aft sweep within 1/2″ from center, so it was already within spec, but I knew we could make minor adjustments to achieve a closer sweep angle. A few iterations of adjusting the rear spar, and we got the sweep to within 1/8″ of an inch. This equates to 0.2deg of sweep!
After getting the sweep right, we clamped the rear spar attachment in place. Then we checked the incidence angle. The incidence is measured by spanning a level from the forward spar to the aft spar with a 3″ space above the aft spar. If this angle is 0 deg (or matches the fuselage angle – which was level at 0 deg) then the incidence is correct. Van’s guidance is not so much the precision of 0.0 deg incidence, but that the two wings match. In my case the initial measurement was 0.3deg off from 0 on the left wing, and 0.4 deg on the right wing. At this point we made some minor adjustments by unclamping the rear spar and adjusting it downwards. this brought the angle on the left wing to 0.0deg, and the right wing also to 0.0deg! We clamped the wings, double checked the sweep, and also took a measurement from the wingtips to the aft center of the fuselage. Both those measurements were equal to each other. At this point we wrapped up for the day.
The next morning, we came back and double checked all the measurements with a fresh eye. Everything still measured perfectly. I got out my drill guide and drilled a #30 hole through the rear spar on the left wing. The center of this hole was > 5/8″ from all edges of the rear spars (on both wings) per the structural requirements. I then expanding it to a 1/4″ hole using the guide. After a 1/4″ I drilled the spar to 9/32 and then used a 0.311 reamer to finish the hole. The reason for doing this step is that the bolt is an AN5-10 bolt (measures 5/16″ in diameter), but the hole made by a 5/16″ drill bit is slightly bigger (a few thousandths). For the primary bolt that locks position of the wing, it should be a super snug fit. The bolt measures 0.3125″ in diameter, and the reamer is 15 thousandths smaller than the bolt. We did the same thing on the right wing.
At this point, we called it a day, but I got out the aileron pushrods and inserted them into the wings in preparation for rigging the controls. Similarly with the flaps, I temporarily installed the flaps to ensure that they could fully retract to the underside of the fuselage. Next time I’ll finish the aileron control rigging and flap rigging.
Today I installed the side skirts to the canopy. I began by completely prepping the surfaces of both the skirts and the canopy/canopy frame. Since I bonded the canopy to the frame with SikaFlex, I also am bonding the side skirts to the canopy. This requires following the same steps as before: activator, primer, glue.
Once I had all the surfaces prepped, I applied the activator and then waited the required 10 minutes. then I primed both surfaces and waited 30 minutes. I then applied a generous amount of glue and spread it out, then I clecoed the skirts in place. I needed to add a clamp to the top corners on either side, to get the skirt to sit right against the canopy.
While things were setting up, I also decided to wire up a tail-mounted forward-looking camera. Years ago I added wiring provisions for adding a tail-mounted camera, but did not know what I would do in the long run. I decided to mount a wide angle mini camera to the top of the vertical stabilizer.
I wired the camera up and fed the signal into the Dynon EFIS. I spent some time working on the alignment, and once I was satisfied i tacked the camera in place with some super glue.
I will eventually build up a fiberglass and epoxy fairing to smooth out the transition to the camera. I will also likely need to make this removable, but thats for another day.
Today I finished the riveting the aft skin now that the window is trimmed to the final size. Once I finished riveting I then spent some time finishing the surface prep for the SikaFlex process.
I also added a 1/32″ monofilament line to set the gap between the window and the skin for the SikaFlex.
I also spent some more time adjusting the canopy latch in order to get a better fit. I think it may be getting close, but final adjustments will probably need to be made continuously until I’m happy with it.
My friend Norio came to help with the install. We started by dry fitting the canopy and marking it for exact alignment. We walked through the process and the execution plan.
Cleaning the glue joint
The entire process will involve Sikaflex. It’s a three part marine UV resistant glue. We first wipe down the mating surfaces withe Sika Aktivator 205. This preps the surface for the next step.
Canopy frame primed. Canopy primed
We waited the required 10 minutes for the Aktivator to do its magic then we primed the surfaces with the Sika 209D primer. This stuff is quite nasty. We then waiting 30 minutes. The primer goes through three phases: very runny liquid, tacky, perfectly smooth and cured. At this point we have an hour and a half to apply the adhesive.
Applying adhesive
I started at the top of the frame and began applying the bead of Sika 295UV adhesive. I cut a V notch in the applicator tip in order to get the appropriate amount of glue for the bead. Sikaflex recommend 1/8” thickness to allow for thermal expansion.
I worked my way around the perimeter of the frame, along the sides and then finished off at the front of the frame.
I’ve read many posts about this process and every one of them said that they needed more adhesive. So I was hoping this would be enough
Getting ready to drop the canopy on
Norio and I then grabbed the canopy and prepped to install it. As we put it into place my wife Britney was there to make sure it was aligned to our marks (and take awesome photos).
Carefully going over the propAligning the bubble before dropping into position Aligning and tightening the side clamps
I managed to climb inside to add the final touches and to fill any gaps.
Filling the forward canopy
I just barely managed to fit the applicator tip in the gap above the dash. I then used my finger to create a nice fillet.
I climbed back out and we did some final checks. We ended up adding a ratchet strap to hold the forward part of the canopy down.
I went back the next morning to check the curing of the canopy. Everything looked great! It was a huge relief. I started removing the clamps.
Getting the excess glue off
I propped the canopy up so I could get under it and clean up the areas where there was excess squeeze out of the glue.
I also flipped it over to check for any gaps. I needed to add some glue on the rear of the canopy frame where I didn’t have access during the initial fitting.
First time opening the canopy
The whole experience was really great. The process was quite straightforward once I read through all the Sikaflex documentation (and referenced many posts on Vans Air Force). The whole process took around 3 hours from test fitting to finished install, with an additional couple hours the next day.
RV-7 N890GF 