Matchdrilled Right Tank Ribs and Baffle

May 26, 2011

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Not many pictures tonight, but I did get the tank matchdrilled.

But first, I got some things ordered from Van’s today in preparation for the tank sealing process:

  • 60 x BUSHING SB375-4 Snap Bushings, 3/8 (1/4)
  • 1 x DUCT NT 5/8-25 Nylon Conduit
  • 30 x BUSHING SB437-4 Snap Bushings 7/16 (1/4)
  • 2 x IF-4/6 RV-4/6/6A/7/7A/8/8A Wing tank flop tube
  • 1 x MC-236-B2 Tank sealant with accelerator QUART KIT
  • 1 x FUEL TANK TEST KIT Fuel Tank Test Kit

Of course, once I placed the order, I remembered that I buggered up the inboardmost rib of the right leading edge and needed a new one. I need to remember to order that one, and BEG Van’s to send it in the same shipment.

I decided to go with 2 flop tubes. (Flop tubes allow the fuel pickups to flop around in the tank, and therefore sustained inverted flight.)

One school of thought is that if you have two flop tubes and they get stiff, you could increase your unusable fuel (they don’t flop good no more) in either the upright or inverted attitudes. People therefore put one flop tube in and one rigid pickup. This means you have to switch tanks to your “aerobatic” tank before doing negative-g aerobatics. (How often will I do sustained inverted flight? Probably not very much.)

Anyway, I weighed the pros and cons, and came to the conclusion that the aesthetics of not having a single tank for aerobatics, and therefore a checklist item or a special placard, outweighed the possibility that after 10 years, my tube wouldn’t flop as floppily as it did when it was young.

Every couple years, I’ll open up the tanks and verify adequate flopitude. They are only $38, so it’s probably worth replacing them every 5 years anyway.

So, now that I’ve settled on duel flopicity, let’s get back to building.

I decided while matchdirlling, it would be easiest for me to do it while it was on the spar, so up on the spar the tank went.

(Be careful though, Van’s notes to matchdrill off the spar to avoid damaging the spar. This is really only a concern with the baffle holes (about the 10 most inboard ones). Take the tank back off the spar do matchdrill those.)

No action shots today, but much cleco-moving.

Back off the spar for baffle drilling.

Next up is fuel tank stiffeners, then a lot of prep before assembly of the fuel tanks.

1 hour.

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Started Countersinking Right Main Spar

February 26, 2011

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This work session was really the same as the last, but because I’m trying to log stuff in categories, I split them up.

I felt like I had a half hour left in me, so I grabbed my countersink cage and banged out some of the spar countersinks that need to be done before riveting the wing skins on. (Riveting the wing skins on is a long way off, but it was a nice little task I could knock off the list.)

A shot of the inboard countersinks.

Oops, looks like I missed 4 holes here. I’ll hit those tomorrow.

A shot of the outboard countersinks.

0.5 Hours.

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Mucho Leading Edge Work

January 3, 2011

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Warning: This is a long post with lots of pictures. I’ll try to keep commentary to a minimum. (Oh, and I just took the pups for a run outside, and it was cold, so please excuse the typos…my fingers are still a little frozen.)

Well, today was a day off for me (New Year’s Day observed) where everyone else had to go to work, so I got a ton of work (on the airplane!) done. It was really cold last night (and today on our run…brrr), so as soon as I was ready to get out into the garage to work, I turned on my portable heater and turned right back around to go inside.

Hmm. I guess I can devinyl some leading edge skins while the garage heats up and I keep warm with coffee.

Here's the right leading edge.

Right leading edge upside down.

More right leading edge

Left leading edge, upside down. (That hole is the stall warning vane access panel. More about that later.)

Left leading edge again. (That small strip of devinyled leading edge on the left side of the picture is the stall warning vane rib attachment. Again...more later.)

That was about an hour of devinyling, so when I took my leading edge skins outside, it was not too bad temperature-wise. Thanks portable heater!

Note: I am working a little out of order. Technically, I should be prepping the main ribs for priming, then riveting those ribs to the spars, then setting the wing stand up, and then adding the leading edge. Since I’m waiting on some scotchbrite wheels for the rib prep part, I’m jumping ahead to the leading edge stuff.

Here, I’ve got all of the right leading edge ribs (except the inboard, undrilled rib) clecoed into the leading edge skin. Many people have trouble here, but if you follow the directions (which I kind of did), you start from the front end of the rib, top and bottom, and then you are okay from there. The biggest trick I found was to push the rib forward (towards the nose) as you are maneuvering the rib into place. I have long arms, so I could see the holes line up from the back, then reach around and stick a cleco in.

I like my modular leading edge/tank cradle. (No comments about my split triangular piece of MDF, please.)

Anyway, then I put the leading edge on the spar, and stood back in amazement. (Amazement at the size of the assembly, and that all the holes freakin’ line up! I know this is a prepunched kit, but still, everything just always lines up. Thank you Vans!)


The dogs must have sensed my excitement…they came out to see what was happening.

Ginger: "Shouldn't you have prepped and primed all of these ribs first?"

Jack (tentatively): "Whoa, that leading edge looks good, but I'm going to stay here...the concrete is cold on my paws."

After playing for a few minutes, they went back inside (it turns out they came out to ask me to turn on the gas fireplace….okay, okay, I will).

On to the left leading edge.

This is an awesome sight. It finally looks like I'm building an airplane in here.

After setting both leading edges on the spar (and securing them from beneath with some #30 clecos through the main spar), I noticed that the spar really needs to be straight and level to proceed, even though it’s not fully assembled yet.

So, even though I know I’m going to take this all down soon, I went ahead and leveled the spar using the trusty (and calibrate-able) iPhone app from Stanley.

I couldn't decide whether negative or positive 0.0 was better, so I left it with negative. My wing stand mechanism sure made this easy. Every 1/4 turn of my adjustment nuts was about 0.1° change. Easy to dial in.

Then, I needed to address the spar bowing in the middle from the weight of all the components. (Once the skins are on the wings, they provide that support, but until they are, there is no (what I’ll call) lateral rigidity.

A variation on a (wing stand) theme. a threaded rod between two 2"x4" blocks.

I thought about this a long time ago, and I didn't know if it would work. It worked great. I know it's not permanent right now, but still, very elegant setup, if I do say so myself.

Oh yeah, I snagged this picture to elaborate on the reason for the larger angle off the outboard rib from the other day. See how the skin overlaps the edge of the rib and spar? I won’t have to notch my support angle to accommodate the skin now.

With the larger angle, there is plenty of room for the skin overhangs.

Okay, time to remove the spar sag.

I tied a piece of string between the top edge of two clecos (actually, it didn’t need a knot…the cleco clamped the string enough).

It's about 1-hole-diameter distance above the hole.

Same on the other side.

Before removing the sag, you can see how much bow there is (look at the row of primed countersinks).

There's about a 1/2-3/4" of bow in the middle of the spar.

A few cranks of my adjustable homemade jack, and the middle of the spar shows the same distance with the string. This was equally as easy to dial in.

Nice and level. (Ooh, that "flush" rivet on that nutplate isn't so flush. I might need a rivet shaver...)

Then, with everything level, I clecoed the leading edge skins to the spar.

Leading edge skins now clecoed to the spar.

Now I can move on to the inboard leading edge rib. It comes undrilled, so first thing, I kind of held it in place and made little marks where the holes were going to go.

You can see my very faint marks.

Then, back to the workbench for fluting (between the hole locations) and flange bending (to 90°).

I had to pretty aggressively flute in some places. Some of these ribs are better than others.

Okay now I need the…what is it?

W-423 Joint Plate.

Okay where is it. I’m sure there are two of them, one for each wing…

[searching shop storage …hmmm…and the airplane room upstairs…hmm…]

Grrr. Where did they go?

Upon closer inspection of the plans…


That was easy.

I marked my half inch line and then pondered how I was going to fit this round (straight) peg into the square (rounded) hole.

This goes in there.

[Many loud, frustrated grunting noises…]

Ahh, there we go.

Then, after careful measuring, checking, drilling, remeasuring, and rechecking, I had the right joint plate and inboard rib drilled.

That was annoying. There was no good way to clamp everything, so everytime I drilled a hole, the rib shifted on the other side.

This one turned out pretty good. 11/16″ all around. I repeated that exercise on the left wing.

I don't have the perscribed 11/16" flange that I am supposed to on the left wing for the tank nutplates because everything moved around a little.

It’s only 1/16″ short in some places. I’m assuming I can make it work with 10/16″, but if I can’t, I’ll just redrill a new joint plate.

Anyway, I was staring at the opening for the stall warning vane, so I got curious and fished out the (separately packed…not really part of the original wing kit) stall warning components. They have this doubler that fits in this hole, with a couple locator tabs (in case you are modifying an existing leading edge that was not prepunched with this access hole). Since mine already has the hole, I snipped off the tabs.

These directions are crazy complicated, but they ended up being mainly for retrofit into an existing wing. For new construction, it's pretty straightforward.

I definitely need the access plate doubler and cover no matter what, but I did give some thought to whether I am going to install the stall warning vane.

I am planning on using the Dynon AOA vane, which will give me good stall warning (I believe it is calibrated during some demonstrated stalls for the highest AOA seen during stall for any flap configuration). For awhile, I kept thinking that I won’t need the Van’s vane (and I was a little miffed that they cut a big hole in my leading edge!), but then the CFI in me woke up and thought of a few things.

Every once in awhile during a rotation or flare, I might get a little chirp of the stall warning. Everyone does, and it can’t hurt to have a small reminder, separate and therefore redundant from the Dynon Air Data Computers (ADCs…wait, I think dynon calls them ADAHRS…or air data, attitude and heading reference system) during slow speed maneuvering. The Dynon is based on pressure differential (between the front and the angled top of the pitot probe), and the other is based on direction of relative wind (the vane just lifts up and compresses a microswitch when the relative wind pushes up on it).

I’m going to go ahead and install all of the provisions for both. It will be pretty easy to get everything installed, and just leave the little vane out if I don’t want it in the end, but I have to fill all the rivet holes anyway, might as well not rule out any future decision changes.

I’ll probably install both; you can’t be too aware of low speeds, and frankly, it will probably help resale to have the more traditional stall warning.

Anyway, I drilled the doubler plate to the leading edge.

Then, I found the leading edge vane support rib. They come as a pair of two; one for the RV-9, and one for the RV-7,8. It was obviously while holding it up to one of the leading edge ribs that the one with the sticker on it is the correct one.

So I wouldn’t forget, I tossed the other one in my scrap pile.

The one on the right is the one for the RV-7 (and -8).

Whew. Good day. I’ve made good progress in the last few days. Tomorrow, back to work, but hopefully I can keep this up.

Oh, and for the record, I hardly had enough 3/32″ (silver) clecos to do both leading edges at the same time. I just ordered 100 more, but I am going to need way more that that to keep working on both wings at the same time. This might be a good time to work on one wing at a time…or break down and order the 500 or so that Vans suggests.

3.5 hours.

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Finished Left Rear Spar

December 12, 2010

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Well, I know I’ve been bombarding you with new posts lately (not!), but I did get a fair amount done today. As you can tell from the title of the post, I finished the left rear spar.

More importantly, I made an investment to my health this week.

I present to you…(triumphant music)…a heater.


This is a pretty sweet heater. It’s small, only cost $20, and by no means will it heat the garage, BUT, the garage is no longer (literally) freezing, and I can work in front of the workbench comfortably for a whole day. It will provide me with two heat settings and has a little fan in it. I set it in the corner of the workbench (as pictured above), and after about 5 minutes, I have to turn it down to the low setting. After about ten minutes, it is pretty comfortable where I’m standing in front of my workbench. And, now that I think about it, it does take the chill off the rest of the garage. Even for the one day I’ve really used it while I was finishing the floors, it has totally earned its cost back.

Okay, back to the airplane. I finally found my stepdrill, and made a couple holes in my W-707E.

Step-drill to the rescue. Had I planned this a little better, I would have done three smaller holes.

I clecoed W-707E back onto the rear spar and flipped it over to use the dremel to clean out the rest of the aileron pushrod hole.

I'm about to flip the spar over and use the dremel to clean up the hole.

I'm not totally done here, but you get the idea.

After that, I moved on to dimpling the reinforcement plates where I won’t be able to dimple them later.

4 #30 dimples along the left (outboard) edge, and #40 dimples along the top flange.

I also dimpled the flange of the rear spar where the reinforcement plates will go.

Then, after a little more scuffing and cleaning, I shot primer on the spar.

I love this color. Makes me happy.

And the left W-707E and W-707F.

After a couple hours inside while the primer dried, I came back out and studied the rivet callouts.

Looks like I can set 7 rivets here right now. All size "square," which is AN470AD4-8.

5 of the 7 set. Nice shop heads, huh?

I moved along the reinforcement fork, using clecos as indicators not to rivet certain holes yet.

I chose to put the shop heads on the aft side of the rivet (these are manufactured heads). I like shop heads, and it makes inspection easier.

Moving outboard, I studied the same callout for the middle reinforcement plate, or W-707E.

Looks like I can set five here, of size "upside down triangle," which are AN470AD4-4.

Manufactured heads

Shop heads.

And repeat with the outboard reinforcement plate.

6 here, I think. More upside-down triangles.

Manufactured heads.

Shop heads.

Then, I couldn’t help but grab the right spar and put them both up on the workbench.

It feels good to have both rear spars done.

Look at the difference in paint color. Left spar (just finished) is on the right.

More difference in paint color.

Anyway, all the rivets were symmetrical from right side to left side, which doesn’t mean I’m correct, it just means that if I did make any mistakes, I made them twice!

Now, all that’s left on the spars is to finish up the left tiedown. Then, I really need to make some wing stands and finish up some rib deburring.

Tonight was a good night. 56 rivets, and it feels really good to get something big put together.

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Onward and upward!

Tank Attach Nutplates, Left Upper Spar Flange

October 23, 2010

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After getting a ton of housework done, I managed a quick half hour in the garage to finish up the nutplates on the left spar.

I took some pictures, but they are just like the ones from the previous post, so I’ll be short with the descriptions.




I found it a little quicker (and less tiring on the drilling arm) to do 4 at a time. I’d countersink four sets of holes for the nutplate attach rivets, then cleco one side of a K1100-08 nutplate in, squeeze the rivet, and then take out the cleco and rivet the other side in. Then move on to the next four.

I’m sure it didn’t actually save me any time, but for some reason it seemed quicker.


Just squeezed the first four rivets on this flange.



Nice looking shop heads, if I do say so myself.



Another angle, I guess?



Remove the cleco.



Put in the other rivet (man, I was really camera happy today...)


Everything was going great until the VERY LAST RIVET.



For some reason I lifted up the squeezer as I set the rivet.



Another angle (except it's the same angle). Sorry.


After successfully drilling the rivet out. I was left with a crooked nutplate. Hmm.


Problem solving time!


I didn’t have a clamp small enough to hold the nutplate in place while I reset the rivet, so I grabbed one of the #8 screws (forgot the part number, sorry), and screwed it in gently.


Wuhoo! I think this is going to work!




(Screwed in gently) because I hadn't countersunk yet. This worked great.



See, I told you it worked great.


Last, but not least, I squeezed the AN426AD3-6 rivets for the K1000-4 nutplates near the spar root.


Flush side...



Nutplate side.


64 Rivets, ONE drilled out  in 0.5 hours.

Oh, and then I went for a run with the pups. (And by run, I mean rollerblade.)

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Left Spar Arrived from Vans

September 21, 2010

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I was home at lunch today randomly (so I could pick up more propane for tonight’s planned grilling session), when I passed a FedEx Express van.

Hmm. That’s weird. Last Thursday, I got an email from Jessica at Van’s saying they had shipped my left spar back to me via FedEx Express, and it was supposed to arrive tomorrow.

Using some critical thinking skills (and the realization that I had NOT been diligently tracking my package over the weekend), I figured the FedEx Van was in the neighborhood for me. I flipped around and followed the driver back to the house. (It’s amazing how incrementally excited I got after each turn back toward the house.)

Anyway, the spar arrived, and it was, in fact, a new, undamaged spar.

Came in its own cute little crate.

No damage!

I didn’t post a lot about my left spar before, because I wanted to see how it would end up before posting to the world, but here’s a quick summary. My left spar, as received in the wing kit, had a pretty small dent in the lower inboard flange. While it was probably airworthy, I was concerned that I didn’t know how much margin on top of limit load I had lost (if any). Also, would there be any residual stress in the area of the deformation, and what long-term stress cracks should I anticipate based on this dent? Do I have to disclose this damage if I ever sell the airplane?

(Background: The airplane is designed for +9/-6 Gs, and the limits placed on the airplane are +6/-3 Gs. The idea is that a spar with damage might really only be good for 8.8 Gs now, or maybe 8.5 Gs (or, admittedly, 8.999 Gs…it was a really small dent).

(Philosophical question: If you could quantify the new margin, and a spar was good to a known 8.5g instead of 9g, and you were still limited operationally to 6g, would you accept it? I still don’t know the answer to this. I think an 8.5g spar would meet the design intent of the airplane (but Andrew! what about 8.4g?!), but what if I accidentally over-g the airplane, something breaks, and I am falling helplessly to the ground. With a “perfect” spar, at least I know it was all my fault. With a dented spar, I’d be cursing Van’s the whole way down.)

(Dear Mom. There is no way I’ll ever over-g the airplane. Stop worrying. It was just for discussion purposes.)

If we could quantify what I’ve lost if I continue to build with the damaged spar, I may be okay to proceed with enough residual margin, but I have a hard time putting a spar in my airplane knowing it isn’t perfect structurally and not being able to quantify what I’ve lost. For the record, I’m an engineer… this has nothing to do with the small scratches and scotchbriting everyone has on their spars. I’m talking about material deformation.

Anyway, Gus and I talked (about loads…bending, drag, torsional, etc., but I’ll leave that out of here for now), and they really don’t have the capability to do an analysis on a spar flange like that, so he agreed to send me a replacement spar if I could send the other one back. (They can do an ultimate load test on a completed wing, just for future trivia.) Luckily, since this was shipping damage, ABF has picked up the shipping tab. (ABF customer service was less than optimal).

I feel a little guilty about standing ground about the damaged spar, but I think some of that has to do with work (if a spar had come into work like that, we would have either immediately rejected the part and sent it back, or performed enough engineering analysis to deem it acceptable as-is or with a repair). I want to be able to take my airplane to +6/-3 Gs and not always question whether my margin is the same as everyone else’s.

(I’ll leave out the more philosophical discussion about whether the margins on top of the posted limits are equal given the widely-ranging construction practices and skills that appear to be out there in the build community. I have to assume the airplane is designed to fly with plenty of margin after being built by a below-average builder, but can still pass Tech Counselor and DAR/FAA inspections.)

Ultimately, Van’s did a great job managing my concerns and communicating quickly and effectively about the whole problem. I really do appreciate their commitment to customer service, and their willingness to listen to my engineering concerns about the defect.

Thank you, Van’s.


Back to building!

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Right Rear Spar Doubler and Reinforcement Fork

September 8, 2010

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The next step on the rear spars is to trip the W-707D and W-707G Rear Spar Doubler and Reinforcement Fork to size.

These parts are shared between the RV-7 and RV-8 (and maybe more, I’m not sure), and must be trimmed if you are building the -7.

This is a tricky trim job, though, because many people have future troubles with drilling the rear spar to the fuselage and maintaining the required edge distance for the hole in THESE PIECES.

It would be best not to overtrim, and leave even less margin than what is already there.

The plans and construction manual both point to Dwg 38, which is of course not included as a full-scale sheet in the wing kit, so I got out my preview plans and started staring.

Even though I’m only working on the right side for now (will bring the left wing up to the right side’s progress when I get the replacement spar from vans), I’m going to do both sides of this now while I’m all mind-prepped to do it.

A snapshot of the applicable portion of Dwg 38. Looks like I should start measuring and marking. (No cutting yet, though!)

Keep in mind here that you measure from the edge you are about to start cutting away, so once you start cutting there is no double-checking your measurements.

Of course, I'm being dumb by doing the right side first (left is shown in the drawing above.)

Here are both lines drawn, measured, double-checked etc. It's still all making sense, so that is a good thing.

The bottom cut off. (For you OCD types, I realize I should have made the other cut first, which would have been a little less cutting overall, but oh well).

I decided to cleco the two smaller pieces together first, then transfer the lines to the bigger forks, and do those separately.

Ready to transfer the lines.

Of course, I didn’t get any in-progress shots of the fork cutting, but it went well. I then clecoed the left and right assemblies together and grabbed this shot after a few passes on the scotchbrite wheel.

At the end of this project, I am going to go back and count how many toes ended up in all the pictures. Here's...{counting}...6 more.

After some time on the scotchbrite wheel, I have two ready-to-cleco parts.

Nice and scuffed.

Then, I clecoed the doubler plate and reinforcement fork to the right rear spar and started matchdrilling.


I had a hard time deciding if I should enlarge some of the rib attachment holes in the fork and doubler plate to final size, and I decided I would. I couldn’t find anyone who said it would be a bad idea, and now I’ll get to deburr and prime all of the rear spar components.

I did leave the majority of the rear spar “future” holes alone, though. I guess per the directions (indirectly, just in step order), I’ll drill those after priming the rear spar.

Here's a picture from the backside (actually, front side) of the spar.

Of course, I was careful to mark and enlarge to #40 the flange holes that need to be dimpled now (the reinforcement fork prevents the female side of the dimple die from getting behind these holes).

I didn't actually dimple, though. I need to leave something for tomorrow.

After taking everything apart and deburring holes, I have a few pieces ready for priming, and a rear spar with some remaining deburring before priming.

I scuffed the rear spar where I had already drilled and deburred to help remind myself what I have left to deburr.

Today’s hour was a good one; a few things ready to prime, and just one deburring and priming session away from being able to rivet the rear spar assembly together.

I need to go buy some more Napa 7220 Self-Etching Primer.

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