Table of Contents

  1. Horizontal Stabilizer
  2. Organizing the Parts
  3. Practice Projects
  4. Why an RV-7?
  5. Links

Horizontal Stabilizer

Rear Spar Assembly

View this post on Instagram

A post shared by N1337G (@n1337g)

The HS-609PP doublers required very little rounding to sit flat against the spar web, the bottom doubler needed a bit more than the top. I made 3-5 light passes with a vixen file followed by a couple heavy passes on the scotchbrite wheel. Then I made one light pass across all eight edges with the vixen file, followed by one more heavy pass on the scotchbrite wheel to get the required 1/32 fillet on the edges.

I used a 40-grit flap wheel on the angle grinder to round off the ends of HS-609PP, which was a bit like sculpting butter with a blowtorch. Then I used a finer grit aluminum oxide wheel on the die grinder to fine tune the radius. They're not perfect, but I think they're as close as they need to be... although I reserve the right to be vain and go after them with the die grinder a bit more (they'll be visible until the elevators are attached, a long time).

View this post on Instagram

A post shared by N1337G (@n1337g)

Match drilling the #30 holes in the doublers was quick and easy. The high speed air drill makes this incredibly fast, I love that thing. I had a little trouble hanging up the bit at first: the trick is to ease into the trigger until full speed, then hold full speed until you've pulled the bit all the way out of the hole.

I had more trouble with the #21 holes: I think a slower drill would do better at those, so I'll try using the electric drill next time. I managed to make it work with the air drill though.

Drilling the 413-PP elevator hinges was easy. The 412-PP hinges presented a new problem for me: there are only two holes, and one cleco fastener couldn't be trusted to ensure the hinges stayed in the same place when the other cleco was removed, square to the midline of the spar and parallel to each other.

I was probably a little more precise about this than necessary: I used a pop rivet resting in the hinge hole as an alignment check, and used the calipers to measure the hinge gap width with the clecos all in and set it back there once the cleco was out, and a C-clamp to prevent the hinge from "hopping" out of alignment when I started drilling. It worked pretty well.

Ideally, I could've clamped it in place with both clecos in, then removed a cleco and drilled, but no matter what I tried I'd end up moving it a bit when I took the cleco out. I was afraid to really screw down the clamps because I might have bent the hinge. A shim of the right size between the doublers could have solved that problem, that might be a better way to do it...

Organizing the Parts

I decided the easiest way to do this would be to create a list of all the parts in the order they were used. If that sounds like a lot of work... it’s not! With the power of computers, it took me about ten minutes.

First, I just manually point-and-click copy-pasted the text out of the PDF viewer into a text document, which took about five minutes. There are automated tools for doing this... but the ones I tried were confused by the bi-column landscape format, and would interleave the paragraphs.

Luckily for us, Vans has a very nice and consistent part numbering scheme. All I need to do is take the text, and put it through a software filter that takes out every word that isn’t a part number. I’ll pass that output through a sorter that removes duplicates (so the parts only show up the first time they are used).

I’m lazy, so I wrote a kludgey filter that gives false positives:

grep -Po '\w+\-[\w\-]+' rv7-emp.txt | cat -n | sort -s -u -k2 | sort -s -n -k1 |
cut -f2-

I had to manually scroll through the result and delete false positives like the word BACK-RIVET, which took 2-3 more minutes. After that, I had my list! Computers!

HS-609PP	HS-603PP	HS-609PPs
HS-708		HS-412PP	HS-413PP
HS-411PP	HS-411BPP	VA-146
HS-411APP	HS-411		HS-00001
HS-702		HS-714		HS-710
HS-00006	HS-00005	HS-706
HS-707		HS-601PP	VS-808PP
VS-803PP	VS-410PP	VS-412PP
VS-704		VS-705		VS-706
VS-707		VS-411PP	VS-801PP
VS-901		F-712		VS-702
R-915		R-901-L		901-R
R-901		R-904		R-902
R-917		R-405PD		R-606PP
R-607PP		R-608PP		R-903
R-912		R-913		R-901R
R-916		R-710		R-918
R-901-R		R-909		E-614-020
MK-319-BS	E-701-L		E-720
E-720J		E-720K		E-720L
E-720D		E-720E		E-720F
E-615PP		K-1100-06	E-00001A
E-610PP		E-611PP		E-702
E-703		E-704		E-714
E-713		E-709		E-701-R
WD-605-1-R	E-701		E-606PP
E-705		WD-605-1-L	WD-415
E-619-1-020	E-607PP		E-619PP-1-020
E-718		E-717		E-721
619PP-1-020

Practice Projects

View this post on Instagram

A post shared by N22ET (@rv7.n22et)

Control Surface

Back-riveting the stiffeners turned out nearly perfect, I've really got that part of this figured out. I used the squeezer to set the ribs, the first ended up with crooked shop heads because I wasn't holding the squeezer true, but I was able to fix it for the second set (and all subsequent ones).

The first skin went on very easily. The second skin... not so much. I have huge hands, and it was extremely difficult to get my hand between the skins to hold the bucking bar for riveting the spar. I really loused this up and had to drill out every single rivet multiple times... it turned out I was using the incorrect length and they were too long. I also turned the pressure down from 30 to 20 PSI, which helped a lot. Moral of the story: double check the length of the rivet, and start with too little power.

The trailing edge didn't turn out super great: it bowed a bit in the middle, and one end the holes ended up misaligned. For some reason, the 3/32 clecos kept popping out of the holes as I was riveting, I need to figure out why that was happening.

I cheated and put pop rivets in the final rivet down the ribs: I could not figure out how to get that rivet set to save my life, despite trying to make the plate described in the instructions. I think this is one of those things I need to see somebody do in person...

Overall, I felt like I learned a lot, and it would be much better if I did it a second time.

Sign

I back-riveted the nutplates to the L shaped pieces that join the visible skins, used 30psi on the tank reg and felt like I started to get a much better feel for it. I forgot to deburr the holes I think… not going to redo it since its a sign, but this is definitely going to be part of the checklist.

I decided to countersink the faceplate for flush rivets, since I wanted to practice that. I used the drill press with a foot switch and it worked very well, I was extremely pleased with how it turned out.

I really struggled with the universal rivets until I realized I was just using too much power. 20-30PSI on the regulator is plenty.

Toolbox

I used the hand squeezer on the round head rivets. Need to measure them to see if they’re up to snuff, but they look alright. It was difficult to hold the squeezer true while exerting enough force on it.

I back-riveted the flush rivets with the pneumatic gun. These turned out terrible, although I felt like I was getting more of a feel for it towards the end. We started with 90PSI, which was hilariously too much. I used 60PSI for most of them, which was probably still too much. The trigger has a nice reliable variable action to it, I think with a bit lower pressure it’ll work better.

I decided to be lazy and try to free hand drill the #30 holes for the handle hinges, since the bit was already in the drill… shockingly, it slipped on one, hence the crooked handle. The handle rivets are squished because I wasn’t thinking and back-riveted them, oops.

I really need 1/8 clecos: they’re on backorder, all I have are 3/32 and 5/32, so I had to improvise with clamps. It worked… but was imprecise, I ended up with a few ovular holes in the front stiffener.

Background

View this post on Instagram

A post shared by N22ET (@rv7.n22et)

Why the RV-7?

My mission is just flying around for fun with no real destination, sometimes solo but usually with my wife Robin. We’d like to be able to travel longer distances in the airplane, but at least 3/4 of our flying will be local, so we don’t want a big fast airplane that’s expensive to sightsee in. Our only “must haves” are tailwheel, and side-by-side seating.

The RV-7 is really perfect for us: its main limitation is how much load it can carry, but we weigh 300lbs together, so we’ll be under gross with maximum baggage and fuel. With an IO-320 up front, it’ll cruise ~170KT true at 8000ft on 75% power, burning 7-8 gal/hr. Lean of peak at lower power settings, we should get 150KT at 5-6 gal/hr. Should we decide we want to, we can easily “upgrade” to a IO-360 or IO-390.

What other kits did we look at?

We started out looking at high wing taildraggers, just because that’s what all my flying experience has been in. They support more modern engines, which was a high priority at first.

The first kit we looked at seriously was the Kitfox S7. It would have lower operating costs than the RV, but we’d rarely have a chance to enjoy its off-field capability, and it would be lucky to cruise at 90KT. For local sightseeing it’d be a great airplane, and with the Rotax 914 we could easily fly in and out of Denver on the hottest day of the summer. But the slow cruise speed combined with tiny fuel tanks just make it an impractical airplane to travel in. The kit itself is also nearly $10K more expensive than the RV-7, and it would take a decade to pay for itself via the reduced operating costs.

In the same vein, I also looked at the Rans S21. Rans claims a 500-700 hour build time, which is less than half what any other kit claims. This is an amazing airplane: you can carry 180lbs baggage, 50 gallons of fuel, and two big adults. With the Rotax 914, Rans claims Vc is 110KT, and you could cruise 8 hours and land with VFR reserves. Same drawbacks as the kitfox essentially, although the fuel tanks help make travelling more practical. It’s also even more expensive, about $13K more than the RV-7.

Both the S7 and the S21 would be fun economical planes to own, but ultimately they're just not practical for our travel mission. We want something that can cruise faster. They're also expensive kits, and the bang you get for your buck isn't what we're looking for.

The RV-9 was the first RV I looked into. In terms of efficiency and low operation cost, it definitely wins because we could run it with an O-235. It achieves the extra efficiency more or less by sacrificing the structural beefiness needed to do aerobatics. We really want to be able to do loops and rolls in our airplane... so that ends up being a dealbreaker for us. Cost is equivalent to the RV-7 kit, firewall forward would be a bit cheaper.

The RV-12 is an amazing LSA, but an LSA doesn’t really match our mission. If I could put a 914 and a tailwheel on it, that would be very tempting, but those aren’t realistic modifications for a first time builder. Maybe someday...

The RV-14 is a little roomier and has more useful load than the RV-7, but we don’t need either of those things, so it’s not worth the extra kit cost (+$11K). It’s also less flexible on the engine, requiring 200HP, and it cruises slower than an RV-7 with the same engine.

Choosing an N-Number

I used this script: https://gist.github.com/jcalvinowens/fcb02c54c1e9cc4982ba102f6cee1a57 ...to find the N-numbers with the fewest number of spoken syllables. I submitted three to the FAA at the end of February, we’re waiting to hear back.