January 20, 2021
I didn't like the way the manual explains fitting the tank attach brackets and the baffle. The manual describes drilling holes in the center of each flange of the tank attach Z brackets, then bolting the brackets to the wing spar. Then you trial fit the baffle to the brackets and by elongating the holes in the bracket one way or the other get the baffle to fit just right (If it doesn't fit right the first time). This method works but it is rather tedious and requires some trial and error.
On the second tank I tried something a little bit different. I drew the lines, drilled and bolted all of the attach brackets to the spar, just as the manual says except that I didn't drill the holes on the baffle side of the brackets. Then I placed the baffle on the brackets and clecoed the tank skin to the spar and the baffle (Having a rib or two clecoed to the skin helps). Once everything was lined up I drilled the baffle to the most inboard bracket with a #31 drill and put a cleco in three of the holes. Then I removed the skin and drilled the rest. Then I drilled the ribs to the baffle and brackets with a #30 drill.
I just installed that tank last night and it fit perfectly.
One more tip on drilling the rivet holes in those brackets. You want to try and make sure that the rivet holes don't get too close to the web of those brackets. The rivets that are going to go there are blind rivets and you need all the room that you can get for the rivet puller to pull those rivets. Also remember that you are going to be covered in the black nightmare (Pro-seal) when you are doing all this and that stuff magnifies any problem. I ground the top off of the cheapest rivet puller that I could find until it almost quit working and I just got the rivets pulled on the first tank, and they were right on the centerline of the flange. On the second tank I fudged a little and move the flanges the right way to get the rivets closer to the edge of the flange (Not much though, mind your edge distances) and they pulled quite easily. I had a little trouble getting the bolts in on the inboard bracket (remember it is backwards because the bolts go through platenuts that are riveted to the spar instead of the bracket), but that one doesn't get blind rivets anyway so keep it fairly well centered and give yourself some room on the rest.
If I could build one more tank I think I could get it perfect. :-( AHHHH!!! NO MORE PRO-SEAL!!! I'll do a really good job on the big tanks on the RV-10. :-)
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