Brake hoses

December 27th, 2020

To complete the plumbing of the brake system I bought a set of teflon-lined, steel-braided brake hoses from TS Flightlines. Tom was great to work with, and I'd recommend his services to anyone in need of aircraft plumbing.

I really only needed the two hoses that go between the firewall and the brake calipers, but I decided to go ahead and replace all the interior hoses with this new non-life-limited teflon stuff too. As a bonus, the new hoses are thinner and lighter than the old ones they're replacing.

A few strategic tie wraps keep the hoses from binding on each other:

I also replaced the plastic "ice maker" tubing from the brake reservoir to the passenger pedals. I had to experiment with hose routing and fitting angles to make sure these hoses remain well clear of the avionics and wiring mounted above.

Forward of the firewall, one hose splits off towards each brake caliper:

In this overview shot you can see that the left side brake hose has a straight shot down the gear leg to the left brake caliper. The right side brake hose, on the other hand, takes a circuitous route across the engine compartment to reach the right gear leg:

The hoses are affixed with small lengths of split plastic tubing that are stuck to the gear leg with plain old black electrical tape. This seems a little cheesy until you realize that an adel clamp would be heavier, bulkier, and wouldn't properly clamp onto the tapered gear leg anyway.

Down at the caliper there's plenty of slack to allow the brakes to work. The use of flexible hoses instead of rigid aluminum tubing along the gear legs is more expensive but almost trivially simple compared to the plans method.

Here are some detail shots of the right side brake hose… first it crosses behind the diagonal engine mount tubes, with adel clamps to affix it near the breather hose:

Then it dips down and under the prop governor cable, curves around in front of some electrical components, and then finally proceeds down the right gear leg. Altogether this hose is affixed to the engine mount in four places, which was a fun exercise in adel clampery.

Then from there it's another straight shot to the right side brake caliper, again with the same tape treatment to fix it to the gear leg:

There's no brake fluid in these lines yet, but at least all the plumbing is there now.

Fuel tank attach brackets

December 26th, 2020

Another item that's shown in one of the plans drawings but not really mentioned in the assembly instructions is the F-796A fuel tank attach brackets. These protrude from a spot on the forward fuselage, and get bolted to the corresponding mounting ears on the forward ends of the wing fuel tanks. I don't need these brackets yet themselves per se, but the mounting of them also involves a series of parts on the inside of the fuselage, which is a job I need to complete.

The interior parts for mounting each tank attach bracket are a piece of angle and a stackup of aluminum spacers:

I cut and shaped these to fit between the lower longerons, on the forward side of the F-902 bulkhead. This required unhooking the fuel tank vent plumbing and moving it out of the way. My recommendation to anyone reading this is to install these parts much earlier, so you don't have to rejigger your vent lines like I did.

I drilled the upper and lower bolt holes by match-drilling through existing rivet holes. Then I installed the tank attach bracket with a temporary hardware store bolt in its upper mounting hole, and match-drilled its lower bolt hole through the centerline of the mounting parts below. That step was much easier once I picked up a 12" long 3/16" drill bit. The rivets visible under the bracket in this photo are just sitting in their holes to help keep things aligned.

After drilling and deburring everything, I primed and painted the mounting angles with my interior color (Rustolem Dark Pewter textured) and painted the steel attach brackets with Dark Machine Grey enamel. While I was having a painting day, I also painted the spar gussets from the last post in the same interior color.

I had to enlist Mary's help to drive the rivets, which are in an inconvenient spot for solo riveting:

I made sure that I'll be able to bolt the tank attach brackets in place when I need to, but I'm not going to attach them just yet because they seem like a real knee-banging, pants-tearing jobsite hazard.

Back inside of the fuselage, I was able to reshape the fuel vent lines and re-clock the elbow fittings to clear the newly-installed mounting angles. Thank goodness for soft 3003 tubing.

Spar gussets

December 24th, 2020

The taildragger RV-7 has a pair of hefty aluminum gussets (F-7114) that bolt to the main spar and the lower fuselage longerons, fulfilling the same purpose as the main gear weldments which would be there in a tri-gear RV-7A. The plans don't really say when to attach these parts, other than you obviously need to have them in place before you mate the wings. I'm not to that stage yet, but I'm trying to get everything possible done inside the fuselage, so I decided I'd better check these gussets off the list.

First I made a set of drift pins by cutting down some appropriately-sized hardware store bolts and grinding a the ends to a taper point. By chucking a bolt into a hand drill and spinning it against my belt sander, I was able to make a nice taper fairly quickly, and it warmed my hands up to boot. A quick pass with some emery cloth made the ends nice and smooth.

Before doing anything else, I used the taper pins to check that the factory-drilled bolt holes in the spar were okay. There was a brief moment of panic when I could only get about half of them to go in, but with the aid of a hole gauge I figured out that the actual problem was that the F-704C/D plates were slightly misaligned with the corresponding F-704E/F bars that they were riveted to. This must have been due to the quickbuild factory failing to bolt the plates and bars together properly before match-drilling and riveting. I decided the best fix would be to carefully file the holes in the F-704C/D plates only, leaving the bores in the much more structurally significant F-704E/F bars untouched. This was fiddly, but I managed to make it work. In this photo you can see how out of alignment the parts were before I finished this repair:

I bolted the gussets to the forward face of the spar using short hardware-store bolts. You have to reshape the bent flanges on this part to make it fit properly, but it's no big deal if you go slow with the hand seamer. I drew a centerline on the outboard flange and used a paint stick to prop up the gusset at the correct angle to pick up the existing holes in the lower longeron.

From the outside of the fuselage I match-drilled into the gusset through the existing rivet holes, clecoing as I went. Here you can also see the temporary hardware-store bolts I used to affix the gussets in place while drilling:

Not too bad, plenty of edge distance:

I repeated this process for the other gusset, then drilled the five holes in each part up to #10 to accept an eventual row of bolts. Then I removed the gussets, deburred, and got them ready for painting. These won't actually be installed until the wings go on, so in the meantime I'll just shoot some paint on them the next time we get a decent day for painting.

Finished panel installation

November 21st, 2020

Before I moved across the country and put my project on hiatus, I had been working on a partial panel redesign to incorporate G3X Touch displays. I left the radio stack alone, but I had Steinair cut me two new pieces for the left and right halves of the panel so I could change the displays around. The main change was to replace my previous GDU 37x (7" portrait) displays with a GDU 465 and a GDU 450 (10.6" and 7" landscape screens). Electrically everything was nearly plug-and-play, with just a few wires needing to be moved around to accommodate the change from three displays to two. I also took the opportunity to replace the steam gauge backup instruments with a G5 electronic instrument, which is what the round hole on the pilot's side is for.

That's the last thing I was working on back in 2015, and more recently I found that I'd left myself plenty of loose ends to tie up, both literally and figuratively. When I finally reached a point where I couldn't proceed any further without having the panel installed for good, I took the pieces to a local powder coat shop to have them finished. It took a while, but I eventually got everything back and looking sharp in matte black:

On the reverse side of the panel, I riveted the nutplate rings for the Garmin displays:

I had Aircraft Engravers make me a set of panel placards in 0.020" Lexan, a few of which are shown here prior to installation. These are engraved and paint-filled on the reverse side, so the markings are protected on the front side and can't be scratched. Should hopefully be tough as nails.

The placards have an adhesive backing – here I'm carefully aligning the biggest placard before sticking it down:

Detail view of the placards on the left side of the panel:

All the controls at the bottom of the radio stack have their own labels:

For the final installation, the flap switch spacer needed a bit of thickness adjustment – no problem to shave off a few hundredths on the mill:

Here's the new panel after being physically screwed in place. As part of this sequence I also had to attach the air vents to the panel, since a few of the vent mounting screws are obscured by the panel plates.

This is the mounting bracket for the G5 instrument. It just barely clears the panel substructure. I'd like to say I planned it this way, but truthfully I just got lucky.

At this point I had a few items in the panel that needed to be installed with soldered connections, including the TO/GA button shown here. I used a pair of magnetic helping hands stuck to a clamp to keep things from moving around while I did the soldering.

I rethought my previous idea of having a start button on the stick grip – now I have a more traditional ignition/start key in the panel. Here you can also see the placard labels for the TO/GA button and the alternate engine air cable.

This is the knob for the rotary heat vent control. The knob fits tight to the input shaft, but there's some play in the gear mechanism, which allows the knob to wobble. To fix this, I made a simple friction washer out of thick felt, to fit between the knob and the panel:

All the knobs and most of the small devices on the right side of the panel are installed here. With the felt washer in place, the heat knob moves smoothly but shouldn't be able to wobble from vibration.

The 3.5mm auxiliary audio jack is soldered in place, with plastic shoulder washers to electrically isolate it from the panel. Here you can also see how I used black oxide coated button head screws and washers to attach the panel and the devices in it:

On each side of the cockpit I installed the labels for the map light dimmer knobs, although I'll leave the potentiometers themselves hanging loose until after I set the rivets that live just behind here:

After lots of work tidying up and securing things, here's what the behind-panel wiring looks like. There are still a few loose wires outstanding, waiting for the top skin to be installed, but I think it looks pretty good for now:

Here's all the non-removeable panel components installed, and the electrical wiring complete and ready for careful testing:

The pilot's display and G5 are shown installed here. There are six annunciator lamps and a test switch in the panel, all of which are waiting for a set of labeled lenses that I've ordered from Aircraft Engravers. So for now they are just pretty colored lights with no text on them.

And after some methodical circuit-by-circuit testing, here it is all lit up. Somehow in the past five years I managed to develop one short circuit (in the pilot's right headphone audio channel) but I managed to repair the offending wire and now everything appears to be working as designed.

Here's the panel in darker lighting conditions, showing the backlit rocker switches. Even at minimum brightness the LED lamps in these switches are pretty bright – I'll deal with that later if need be.

One consequence of taking five years off from building is that parts of my panel have become positively antiquated. The GNS 430Ws especially are getting pretty long in the tooth, being now two generations out of date, although these particular units are practically brand-new. I did give serious consideration to tearing them out and rewriting the ratio stack for a more modern navigator, but in the end decided that I should stop redoing previous work and just focus on driving towards the finish line.

Late summer update

September 20th, 2020

I have been working on various small jobs on the airplane project on and off all summer, but not much photo-worthy has transpired, so I've been remiss in posting updates. Mostly I've been finalizing wiring and panel details, securing wires that need to be secured, and finishing up the end stages of a panel overhaul which I'd begun before I moved, and hadn't mentioned here yet (more details on that later).

Believe it or not, a lot of work has been done here, although it's not at all apparent just by looking at it:

The panel plates and roll bar components are currently off getting powder coated, and when they're finished I should be able to install them for good.

Years of abuse and several hundred instances of me climbing in and of of the fuselage have left some chips in the cockpit paint, so I took the opportunity to touch up the cockpit rails and seatback bulkhead now while the panel is removed. Luckily the paint I used for my interior is still made (Rustoleum Textured in "dark pewter").

I've also been spending a lot of time working on another aviation-related thing which I will reveal eventually, so stay tuned for that…