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HS Spar Stiffener Corrosion

RobLyman

Member
I bought an RV-6 tail kit from someone and have started work on the HS spar. When I first looked at the spar stiffeners I saw what looked like brown sticky tape residue and dirt on the stiffeners. After cleaning and prepping with a scotchbrite pad I discovered that it was not tape residue it looked dark gray. The brown was just dirt and cardboard/paper fibers. It was corrosion. Most (80%) of the corrosion came off the surface, but some is still there after a significant amount of cleaning with a wheel. Do these parts need to be replaced?
 
Got a photo handy? Even if I don't have an answer for you, I'd still like to see it if you don't mind posting it here. I won't be offended if not.
 
Just FYI, I went through 2 sets of these on my -7. One set was pretty nasty right out of the box. The other set was nice and shiny. The first set took quite a bit of scrubbing. I remember asking about this very thing last year (I dinged one of mine and have to smooth it out) and I believe they told me that up to 10% material removal is OK. It'll be interesting to hear what Vans says about this.
 
Material Loss

Hey Rob,
10% material removal is the norm for most metal components on aircraft...more than that, you should discard.
Metal thickness is sometimes hard to measure. Two possible ways are with a very good depth micrometer or an eddy current machine. Folks with non destructive testing equipment can be a bit expensive and they are hard to locate. So you best option is the depth mic.
Good Luck!
Rags
 
dan said:
Got a photo handy? Even if I don't have an answer for you, I'd still like to see it if you don't mind posting it here. I won't be offended if not.
I guess I need a better camera. I tried several times and the flash or the outside light puts too much glare on the aluminum and/or the photo doesn't have enough detail. Maybe I need a better picture taker and not camera!

After doing quite a bit of hand sanding with some sand paper and with a scotchbrite, there are a couple of pits that are not anywhere near the bottom.

It looks like I will be calling Vans for some new ones.
 
Last edited:
Rob,

The problem with pitting corrosion is that unless you get to the bottom of the pit (the real bottom, using a maginfying glass) the corrosion will keep going. 2024 is quite prone to corrosion so it will not stop on its own. My limit would be 0.010 of metal removal in a few odd areas, very well blended. But, do you really want to build metal worm into a new airplane? I think you would be well advised to start with new stiffners.

Pete
 
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