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HS fwd spar – cleaning up the mess

After putting the kids to bed, and a nice glass of Cab Sav, I decided to head to the shed to see what I could make of the botched relief notch in the HS forward spar. I figured I’d try and clean up the notch using a reamer and needle files and try and get the notch looking ok. If the edge clearances aren’t adequate then I’m going to have to get a replacement part anyway so I may as well use this as a learning opportunity.

Working slowly and carefully with the reamer, Scotchbrite wheel and needle files I was able to do this.


After… (the top one)

I increased the radii of the notch to web edge after this shot but you get the idea. It’s not looking too bad and I got to know my #30 reamer and needle file set a whole lot better. A big thank you to Andrew Tainsh (RV-6 builder @ SABC) who recommended I get a good set of needle files. They sure came in handy tonight!

Once I got the relief notches looking ok, I thought I’d check the edge clearances. The hole diameters are 4/32″ and the closest edge is 17/64″ (more than 8/32″ but not quite 9/32″). IF memory serves, I need at least 2 hole diameters from the hole centre, which by my calcs is approx. 6/32″ from the hole edge. Hmm…I might be ok.

UPDATE (23 Apr 11) : I had a Technical Councillor from the SAAA come and inspect my relief notches and edge clearances. The advice is that they are OK and the part can still be used. Woohoo!

With my new found reaming and filing skills I set to work on the other spar channel. This time the result was much better. It was about now that I realised my mistake the first time “…drill hole #30 in the corner of the flange. Flip the channel over. Using the hole as a guide, drill out to 1/4″ using the Unibit…” FLIP OVER? No wonder I was clashing with the flange. I was drilling from the wrong damn side. *face to palm*

Here’s a shot of the second attempt. It looks somewhat better than the first one.

Here’s the two spar channels side-by-side so you can see how I went too far in on the first attempt.

The plans then call for some dimpling and countersinking to be done on the forward spar. I wanted to practice this on my spare alclad first so I thought I’d call it a night. I read a few steps ahead and noticed an opportunity too good to miss. I clecoed in a couple of ribs between the forward and rear spars and took a photo. Not quite a “it looks like a plane” shot, but if I squint really hard it kinda resembles one. Of course, it could just be the Cab Sav…

Another 1.5 hrs in the build ledger.


About gstrack

Husband and father of 2. Control & Instrumentation Engineer. Flying nut. Gadget geek.


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