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Empennage

HS ribs – done

Last night I managed to get a good build session in. I finished edge finishing and deburring the last 2 ribs. Then it was time to scuff them. I had to get rid of those pesky white sticky labels. Fortunately Un-Du made quick work of them. It’s acid free, photo safe, and won’t mark/etch/stain – or so the label claims – so I figure it’s safe to use on alclad. I’ve never used it before. After I gave it a go, I must say it works really well. It evaporates fairly quick but you only need a few drops of this stuff before you can scrape the labels off.

Then I scuffed the ribs with a Scotchbrite pad. I’ve read quite a few builder’s blogs and they all recommend scuffing before dimpling or fluting. Makes sense. Then I used my hand seamers to make all the flanges perpendicular to the webs. I did this by eye which I reckon is good enough. When I did this I noticed that the ribs all had a noticeable bend in them – if you could imagine someone bending over backwards – that’s kinda what they were doing after I did the flanges. Now I understand why fluting is required. So out came the fluting pliers and without too much bother, the flanges were perpendicular and the ribs were flat and flush against the table top. I didn’t need too much pressure using the fluting pliers. I just gave a slight squeeze between each flange hole and then checked. Only had to give a second squeeze here or there. Here’s the result. HS ribs scuffed, straight and fluted (except for the inner main and nose ribs which you don’t flute yet).

Then the plans call for the the inner main ribs to have the forward flanges marked for 4 drill holes. These holes are used for the dreaded main rib-forward spar-nose rib union. Many builders have had edge clearance problems on the nose rib aft flange (the one I had to notch previously). This is why I left more flange on the rib than the plans called for. Brad Oliver (awesome builder’s website rv7factory.com – see my links section) and many others stated that they would have also made the main rib drill holes closer together than what the plans call for also. In order for me to get an idea of how much closer together I would need, I placed all the parts in their respective locations, then used a steel rule to measure where the holes were called for.

Then I compared these marks to where these holes would eventually be match drilled on the nose rib. I chose to make each hole about 1/16″ closer to the centre than what the plans call for. I then went back to the main rib and marked the new locations. The result of this checking back and forth can be seen in the following photo. The smaller, outer sharpie lines show the spacing of the holes as per plans. I can see why people get concerned about edge clearances. The longer, inner lines are my adjusted hole locations. I’m going with my adjusted spacing as they provide better edge clearance on the flange notch.

As I am building both left and right stabilisers at the same time I marked the inner ribs for both sides. I marked the ribs left and right as the hole marks were slightly different. Not by much (~1/32″) but enough for holes not the line up if you got the ribs mixed up. Then I marked up the other holes which go through the forward spar reinforcement angles. Again, I increased the edge distance clearance slightly. Here’s the result.

Felt like I made good progress this session. Build time 2.5 hrs.

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About gstrack

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

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