My name is Mark, and I made a Big Mistake in my Build

[CharlieWaffles]

This is a cross-post of my blog entry today and while it was a stupid mistake and one that isn't likely to be repeated by others, it hopefully has redeeming value to others. While we aren't building space shuttles as we often hear, it still needs to be treated with respect and work needs to be done the right way. In this tale, you'll see how one little mistake in reading the plans one late night had a ripple effect. Luckily this was caught in time and penance to the plane gods is now underway.

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I have hesitated to write this entry since last night when I discovered this issue. It is rather embarrassing mistake and one that even as I write this I can't believe I made. However, I long ago set an expectation with myself that I needed to do this project the right way and if anything stuck in my mind after leaving the workshop, then it needed to be addressed.

As I was preparing the wings yesterday for attaching to the fuselage, I was giving the wings a visual once over. I had already known before I even touched the wings that I wanted to review everything as it's been almost two years since the wings were finished up and placed into storage. In that time I have picked up some additional skills and wanted to look at the wings with a fresh set of eyes.

As I was reviewing the torque assembly in the wing root area (the tubes that connect the flight controls and the aileron) I noticed there was some rust and corrosion on the tubes and weldaments. The tube is aluminum and the weldaments are powder coated steel. I had primed the exterior like I usually did but I was noticing the rust and corrosion at the seams of parts and near rivets. This led me to believe the problem was INSIDE the tubes, not the outside. I didn't think much more about it but it stayed in my mind. I used a scotchbrite pad to scuff the surface and the rust mostly disappeared. But it was clear it was coming from somewhere.

During the wing attach work last night I mentioned I had seen the corrosion to another builder and he was intrigued and wanted to see what had happened. I showed him and he was surprised to see it as well. I mentioned I had primed it inside and out, just as Van's had called for and so I was surprised. It was then that I mentioned HOW I primed it and thus the crux of the story. I mentioned "....well, I primed the inside just as Van's said - with Liquid Plumber". David, the other builder looked at me like I was crazy. I said "yea, I thought it was weird too, but Van's is cheap and they do unusual things". I even pulled out the plans and found the section where the tubes are made and pointed to the paragraph. Right there, in black and white it said "the inside of the tube should be primed. We recommend Liquid PRIMER..."

Ugh, now, either my plans have magically changed or at some point I misread that statement. I very much remember a late night of getting to that paragraph, I don't have any liquid plumber" and running off to Home Depot. All the while I was thinking this was an unusual method, but hey, Vans is unusual sometimes.

Well flash forward two years and the liquid plumber - while dry at the time of assembly, is mildly corrosive to metal. It was clear that the chemicals in the solution were reacting with the metals and were causing rust (on the steel weldaments) and corrosion on the aluminum pieces.

There are several places that uses these closed tubes - in fact, all of the control surface with the exception of the flaps use these tubes of varying dimensions.

Today I went back to the hangar and opened up the wings. I found that all of the control tubes in the wings were also showing signs of corrosion at the rivet joints as well. I subsequently remove all of the control tubes in each wing (the torque tube assembly in the wing root), the torque tube to bellcrank pushrod and the bellcrank to aileron pushrod. Because of the assembly technique, the only way to be absolutely sure what was inside the rods was to cut it open. Sure enough, all of the tubes were either etched (aluminum) or considerably rusted (weldaments). It was clear it was a good idea to remove all these pushrods.

I also opened up the tailcone and removed the bellcrank to elevator pushrod as it too is a pushrod style control. Similarly to the other tubes, the only way to be sure was to open it up. There was no visible corrosion on the outside like on the wing pushrods, but this wasn't good enough to be sure it was ok. I cut it opened and found it was properly primed inside with primer - not liquid plumber. I believe that since this was done at the same time as the tailcone, I had properly read that paragraph. But now it needs to be redone due to the testing.

I then thought about the other control rods in the fuselage in the forward portion of the tunnel. I thought about removing all the items to get to the pushrods and it was a lot of stuff to remove just to inspect them, especially sine the tailcone pushrod had proven to be ok. Perhaps it was just the wings I thought.

I chunked the parts I removed in the recycle bin and called it a day. When I got home, those control rods in the tunnel were rattling around in my head - clearly something wasn't settled and it triggered my "make sure it is absolutely ok". So I had decided I would open the tunnel tomorrow and do an inspection. I took a few minutes in the mean time and looked through my log. Sure enough, there were two entries that mentioned Liquid Plumber. The aileron actuation section for the wings had it right in the log entry - as my removal and testing clearly showed. And low and behold, the second entry was for the elevator control system tubes in the tunnel - had it plain as day "used liquid plumber for the primer". At least now it's confirmed.

So I have made up my replacement parts list and will sulk into Vans tomorrow and pick up the replacement parts. Will they wonder why I suddenly went from being almost done to ordering a bunch of control rods and fittings? Probably not, but at least their balance sheet will be a little higher for the week.

In the end, I wound up a bruised builder ego (I am once again humbled), a little lighter in the wallet and ultimately happy this was discovered now rather than later on.

[kiwipete]

Mark

Thanks for posting. Good safety attitude. At least now you'll feel confident in those tubes.

I've always just poured my normal primer in and rolled the tube around then let it drain and dry. But you have to be careful as if the end fittings aren't in then the thickness of the paint can make them too tight to fit.

Cheers

Peter

[roee]

Mark, thanks for sharing. I think this mishap does provide a valuable learning opportunity.

This particular mistake is pretty unique, and would probably never have been repeated by anyone. But I do think it illustrates a broader issue that's very common, and there is a universal lesson here to take away. That lesson is, don't just follow the directions or the drawings unquestioningly.

Van's usually does things pretty well, whether by conventional or unconventional methods, but on occasion something may really not be quite up to snuff. And also, just as easily, the builder could misinterpret something, as we saw in this example. So when you come across something that doesn't quite pass the common sense smell test, it's a good idea to dig a little deeper and get to the bottom of it. Don't just do what you're told out of blind faith in Van's. When you come across something questionable, question it. You might find out that it's right after all, but now you'll understand why it's right. You will have learned something. Or, you might find out that it really was wrong, and you'll have the opportunity to make it right.

In this example, (mis)reading the directions to prime the parts with liquid plumber should have raised a red flag warranting further inquiry, so that was obviously a miss. But kudos to Mark for the diligence to re-inspect the structures when taking them out of storage, which allowed him to find the problem at that point. Kudos for noticing the signs of corrosion, and for then following up on it. For realizing that something was amiss, figuring out exactly what happened and why, and then taking the necessary measures to correct the problem (replacing the affected parts).

[pilottangocharlie]

Sometimes you gotta put the pride aside and laugh at yourself. Thanks for the interesting read!

[zilik]

While your story is atypical in the build cycle it did make me chuckle only because I could see myself reading the line "use liquid primer" and comprehending "liquid plumber".

[tkatc]

Funny story. Thanks for posting. Use the tubes for irrigating your lawn. I'll bet the flow rate is outstanding!

[N427EF]

I know it was not that funny to you but you did the right thing and those tubes will not be on your mind after you get them done right.

I think this will add a new dimension to the primer war.
Liquid Plumber or henceforth known as Charlie Waffle special.

[TS Flightlines]

Mark my friend, I dont think that any of us in this business have gone mistake free. Your mind was telling you something wasnt right, but you couldnt put your finger on it. Fortunately for you, you keep awesome build records, and found your problem. Its also a great testament to you that you have someone else come look at this before you test flew it.
I'm proud of you for sharing this with us. After all-----you are building an airplane, not a washing machine, and not everyone can do it.

You will be fine, and have a beautiful, well build RV10.
Tom

[DonFromTX]

I kept waiting for the punch line, too late for April Fools, then finally realized you were serious!

[aarvig]

I am often up until 1 or 2 in the morning working on my project and I could see myself do this exact same thing. It was a lesson for me to knock off if I am tired and to pay special attention to the plans.
It takes a real man to admit when he's wrong...and you sir are a real man. Thanks for your honesty and for sharing. It has taught me a lesson.