Monthly Archives: July 2017

A not very auspicious start to the tanks…

My wife was out of town for the week, so I figured to get some extra shop time in.  I spent a couple of evenings finishing up the prep work for the tanks.  My hangar neighbor John was going to help me get started.  He was an F-16 crew chief and had some familiarity with the grey goo they call tank sealant.  It seemed better to have a go at this with someone who used this before.  The Rans Raven he’s building has a roto-moulded tank, so he had it a lot easier!

The tank skins were slightly deformed from sitting out so long.  The nose was decidedly more pointed than round, so I did a dry fit of the ribs to see if it would come back into shape.  That part worked out, but it was slow going just to get the ribs to line up.  I made a rib shaped spreader that helped some and I polished and pointed my bent up 3/32″ pin to make a drift pin.  With the ribs in place, the pointy-ness disappeared and I got a good fit.

I still had a little prep work to do on the end ribs.  I riveted on the nut plates (used to secure the fuel tank float).  They didn’t need any sealant because I’ll form a tank sealant gasket when I do the final install later.

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Then I cleaned up the edges of the anti-rotation collars that hold one of the fuel fittings in place.  I decided that it would be a good idea to check to make sure that the nut fit into the collar correctly…. It very much did NOT!  I had to file and clean the edge quite a bit to get a good fit.  This would not have been very easy to do once the fitting was installed on the rib (would likely have had to drill it out and re-mount it!).

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That gave me all the parts I needed to get started!  In anticipation of John’s arrival (he is SO not a morning person), I got everything prepped and laid out.  I pulled the sealant out of the fridge (keeping it frozen or cold prolongs the shelf life), set up the C-frame to rivet the tooling holes closed, and got my dixie cups and popsicle sticks ready….

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At this point, I don’t have a lot of pictures because my gloved fingers were covered in sticky grey goo.  But I can tell you, it did not go well at all.  We started by trying to rivet in the VA-141 fuel flanges.  I tried a squeezer, but the rivet set caught on the edge and I couldn’t get a straight shot at the rivets.  I tried shooting the rivets instead, but I ended up clenching them AND distorting the flanges.  We tried drilling out the rivets, but we ended up messing up the holes.  We declared the whole adventure a total loss.  I’m ordering new parts from Van’s and we’ll try it again.

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So, with that out of the way, we moved on to the really expensive parts!  There are 11 stiffeners to install on each skin.  You have to make sure that each rivet is well coated in goo before pushing through the holes.  We used clear packing tape to hold the rivets in place and back riveted the stiffeners in.  This was the first time John had seen back riveting.  I like it because I always get such nice, clean rivets.  The first 10 stiffeners went really well.

Now all this time it is really raining as a huge storm cell passed right over head (much better building day than a flying day).  I closed the big hangar door because the rain was pushing inside.  John went next door to close up his.

While he was over there, I set up the 11th stiffener, prepped the holes, taped the rivet line, slipped the stiffener in place…. Then I looked down.  There was water FLOWING though the hangar.  It was pouring through the bottom of the wall seam and running a half inch deep in places.  This was not a good day to have my electrical cords down on the ground!

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Then the power went out!

The power came back on again a couple minutes later.  I was just prepping to rivet the last stiffener anyway (air powered!) with a headlamp.

So I spent the next hour pulling boxes and electrical off the floor and sweeping water out of the hangar.

Sigh!

I’ve ordered new end ribs and flanges.  They’ll come with the fuselage kit that will show up in early August (it also contains a new horizontal stabilizer skin — the old one had a big ding in it from an early back-rivet fail).

I won’t get a chance to get back to the shop this month since I’m taking a trip out west for my niece’s wedding.  It will be nice, some day soon, to do those trips in the RV-14!  But for now, it will have to be commercial.

When I do get back, I’ll rivet the stiffeners into the left tank, seal the rivet lines, and get ready to start putting ribs in place.  They’ll be tanks soon enough.

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Tank attach brackets

I finished up countersinking the fuel cap brackets and moved on to the tank attach brackets. These have a bearing, some shims, and three different kinds of nutplates that need to be attached.

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As always, first I had to find everything.  I had put the shims by the brackets themselves when I was hunting up everything at the start of the chapter, but it took a while to dig out all the nutplates.  The MS21051-L08’s in particular were a bear to find.  They are in bag #3015.  They are the only nutplates in there.  The spreadsheet of parts was very helpful! I separated the shims on the bandsaw and carefully deburred the holes (the instructions note to do a good job with this, particularly on the #8 screw holes).

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The shims have to be trimmed to match the ends of the attache bracket.  The narrow shim in particular has a very slim edge clearance to the outer nutplate hole.  I carefully sanded them down on my sanding disk to get the a close clearance.

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I marked the “primer line” on the attach brackets and started clecoing the nutplates in as I found them.  I’m substituting K1100-08 for the K1100-08D because I’m going to use “oops” rivets instead of dimpling the tiny shims.  I’m afraid that the shims will warp badly in the dimpler.  The hole on the end, in particular, is way too close to the edge for my to think about dimpling.

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I filed the cut marks off of the brackets before running them through the Scotch  Brite wheel.  The initial edge was a little sharp.  So I donated a few more drops of “Blood, toil, tears, and sweat” to the project.

The RV-12 was feeling a bit neglected.  The early low clouds had finally risen.  My son Ryan came down for the afternoon, so we fired up 3EN and did some pattern work.  He is getting ready to start his flying lessons, so I let him do one of the takeoffs and one of the landings.  He did a great job!

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I primed up the external parts of the brackets and shims and countersunk the brackets.  The picture shows a test fit.  The bracket lays tight to the skin and the shims have sufficient clearance.

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The final step for the day was to rivet the flange bearings onto the brackets.  This is where I really like working both right and left together.  I’m able to make sure I’ve got everything set up correctly.  The nice mirror image gives me some assurance that dyslexia didn’t bite me here.  I don’t show the riveting, but it came out pretty nice.

I have a few more things to finish up before diving into the Proseal.  I have to rivet some nutplates to the shims and then the shims (with more nutplates) to the brackets. I’m using the NAS 1097 rivet trick here rather than dimpling to avoid warping the shims.  I got the light countersinks done, but then had to jet to meet my wife for BBQ at Killen’s.