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13 Oct 2021

22-02 ->3: Aileron Structure & Counterbalance Preperation

The first replacement parts in the project

Like most sections, 22-02 starts with some basic deburring. Easy - how can you stuff that up?

Well, it turns out you can. I was way too overzealous with buffing the "edges" of the nose ribs and made the edges of the tiny nose tabs way too thin - so much so, when i flexed them, one of them snapped off. No bother, off to the Van's webstore for some $14 parts, with $42 shipping via Fedex - and that's in USD! The second go, i was a lot less 'zealous' :) 

The areas that were supposed to be treated gently

Sucks living so far from the US (this is in AUD)


The tiny tabs snapped off the rib on the right.


Moving on, once i got the replacement ribs, all the deburring went as standard. 

There was a bunch of countersinking the doublers at the ends of the ailerons so flush rivets can be used - this all went fine. 








Counterbalance 

Next up was the prep of the counterbalance. The plans are pretty wordy in this regard, but make sense (mostly!) if you follow them closely. Basically the process is as follows:

  • No need to have all the doublers clecod to the end ribs - the clecos get in the way when clecoing the skin together.
  • Cleco the nose ribs, spar and nose skin together with the counterbalance just sitting in position - Top Tip: the counterbalance is jammed in pretty tightly, so make sure it is flush with the end skin before you cleco the top skin down - it can't be moved afterward. 
  • Match drill #40 the 2 end holes in the counterbalance only and cleco in place.
  • At this point, the counterbalance and the nose ribs are held in place by the clecos holding them to the nose skin - you can remove the clecos holding in the spar, and remove the spar. 
  • This is where the plans got confusing - they want you to drill the nose ribs to the counterbalance (through the 2 little tabs at the front of the ribs). The bottom hole can be match drilled using a long #40 bit, by putting the bit through the lower hole in the nose rib aft flange (see photo below). 
  • The top hole cannot be match drilled in place. They ask you to use a long drill bit to "mark the counterbalance" as per Step 2 and Figure 1 on 22-05 - however you can't even do this, because the skin is in the way? I think the Figure 1 image wants you to put the drill through the rib tab notch gap in the very corner of the rib and the skin, but i could not get this to work. It would not line up with the hole in the rib tab very well at all.
  • In any case, at Step 1 on 22-05 you are supposed to remove the nose skin! But if you do this, you end up with the nose ribs held to the counterbalance with only one cleco on the lower hole. Impossible to ensure alignment. The words and the figures don't gel well on this step. Step 1 words don't match with Step 2 / Figure 1 image. Anyhoo.
  • So what i did was: re-install the spar following the match drilling at Step 1 (clecod only to the rib flanges and not the skin), then remove the nose skin. I could then proceed with Step 2 (marking the hole location of the top little tab on the nose ribs). 
  • Once it was marked, the counterbalance is removed and the holes drilled #40, #30 then #27 for a little -6 size pan head screw. The ribs were also drilled to #27. 
  • You then attach the nose ribs back to the counterbalance using a panhead -6 screw and a little nylock. I did not have any temporary nuts in this size, so i used the nylock. If you are not going to prime anything this is the final installation, however i will be priming the ribs and the counterbalance - so these nuts will be thrown away and new ones used (hopefully i have enough). 
  • Once the nose ribs are attached, it is all clecod back together and you can match drill the remaining holes from the nose skin to the counterbalance #40, then #30. 
  • Everything was removed and deburred.

The pipe was already of the required dimension, so the ends just needed a little deburring


Cleaning off all the tooling oil so i could work on the parts without making a mess. This is just a rag being pushed through.



This is how i match drilled the lower of the 2 tabs for the nose ribs.

This is how the plans call for doing the marking - with the nose skin in place (challenging) and with the aft spar removed. The words in the step prior to this asks you to remove the skin?? This leaves the ribs floating, unless the spar is put back in place. Who knows.


With the spar in place, the nose ribs maintain much better alignment. Otherwise they just rotate around the lower cleco. I used the drill to 'mark' the tube for removal and drilling later. A lot easier to do with the skin removed.


This is how i installed the hardware - i may put the screws the other way around for final installation. 


Priming the Counterbalance

The plans have the following statement:
However, talking to my TC he advised than 304L Stainless (what the tubes are made from) can still develop rust over time, so i decided that i should prime them. The Stewart Systems EkoEtch is a water based primer, so i decided to use something else. I had a can of Tempo A701 spray paint, so i used this. The datasheet says is is good for stainless and does not need to be overcoated. A copy of the datasheet can be found here.

To prime the tubes they need to be cleaned, so i cleaned inside and out using EkoClean. I then scuffed inside and out with a scotchbrite. I first tried to make a little 'tampon' to pull through the tube - but this didn't work that well. A better solution was to wrap a dowel in a scotchbrite, staple on the ends so it didn't slide, and tape over the ends to make it easier to slide in and out. The tube was then cleaned with EkoClean again, cleaned with acetone and sprayed inside (as best as i could) and out. 

The 'tampon' didn't work very well

This worked much better

Scuffed and ready to be painted

I masked off all the holes to stop paint dripping out when i painted the inside.







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