Monthly Archives: June 2017

A day of dimpling

2017-06-24 08.41.12

When I left off last week, I had dimpled the #8 screw holes and hadn’t yet started in on the 3/32″ skin holes.  There are a lot of them!  Because of the way the tank skin is bent, I needed to do some work getting my DRDT-2 set up.  In New York, I had a nice bench with an overhang set up permanently against the garage wall.  For most work here in Texas, I can get away with bolting my dimpler to one of the EAA work tables.  For the leading edge and tank skins, I need a bit of an overhang.  I thought of a bunch of possible ways to set this up.  In the end, I did something very simple and effective.  I used some 3.5″ x 5/16″ lag screws and a piece of 2×6.  This very solidly tied the extension into the table.  A couple of 1″ lag screws holds the dimpler to the 2×6.  It worked very well.

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So I sat in the comfy chair and twirled a dull drill bit in the holes.  I like this method. It is very fast and easy to control.  It just barely takes off the burr while leaving the hole nice and smooth.

I had high hopes of getting in some practice touch and goes, but all thoughts of that were quickly dashed.  It really poured! Even when the airport was in the clear, there were nasty thunderstorms lurking all around all day long.

The DRDT-2 and the carpet covered boxes worked vey nicely.  The dimpling went quickly, but there were still SOOOO many of them!  I finally got all of them done…

Next, I worked on the fuel caps.  There’s a pretty red anodized base and a cheap looking plastic sealing cap. I can get replacement ones made out of machined aluminum, but at $145, it is pretty pricy.  I don’t like the idea of painting the plastic though.  Will likely defer until it is time to paint the plane.  There are some steps, that I’m really excited to get to.   One of them is this shot of the fuel cap base clecoed in.  Pro-seal time is close at hand!

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One clever hint I saw is to set up a swiveling base for the stands.  The Pro-seal is messy and hard to work with on a good day.  These swivels will let me rotate the tank so that I have a good (better?) angle for both applying the sealant and for riveting.  Not quite done in this picture.  I cut these pieces from the end of the 2×6 I used to support the DRDT-2.  Added a rounded edge and then drilled them out for a 5/16″ hex bolt for the axle. We’ll see how they work soon enough.

Next time, I have a few non-Pro-seal tasks to finish on the tank attach brackets and shims. Standard trim, deburr, prime (just the external parts), and rivet.  If I get really saucy, I’ll do the nut plates on the inboard rib (screws pull in the fuel lever sender.  No gasket, only more tank sealant).  If I’m super productive, I’ll do the first set of sealant tasks (closing the tooling holes and adding the fuel flanges and anti-rotation plate).

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Lots of work, but somehow the tanks look the same!

I’m finally back from my month long hiatus.  Some things went as planned, but I didn’t get as much flying in as I hoped.  I had hoped to fly to Fredericksburg for Memorial Day weekend, but the strong area wide thunderstorms put a crimp in those plans.  Somehow in a battle between an 865 pound plane and a Texas thunderstorm, I know who will win!

I did make it up to Denton, TX for my LSA-Inspector course.  I learned a lot.  Much of the course was about how to correctly fill out paperwork to keep the FAA happy, but there was a bit of hands on work.  There was a 60 question test at the end of second day.  I aced it, of course, as it was just a bit of memorization.  This didn’t actually get me my certificate.  I had to go down to the Houston FSDO (Flight Service District Office) to get someone to look at my paperwork in person and get me a temporary certificate.  I’ll get a new Wilbur and Orville FAA card in the mail in a couple of weeks.  I don’t actually need it to work on the plane, but will need it in October when I sign off the condition inspection for N903EN.

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My sister-in-law keeps digging up some of my father-in-law’s old tools (he built a BD-4 and most of a BD-5).  This time, she found a rivet puller and some Avex rivets.

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The last time I took the -12 out, I got a message on the EFIS warning me that the backup battery needed to be tested (It has an internal timer that makes sure the battery is tested once a year).  The test is really simple, actually.  When you shut the EFIS down there’s a button to run a battery test.  The way it tests that the battery will stay up for 45 minutes is to simply keep the display on for 45 minutes and see if there is still battery power remaining.  It passed with flying colors.  I’m good for another year.

 

2017-06-17 12.33.12 HDRI left off last time after getting some of the countersinks done for the tank baffle on the left tank.  I finished off the other 150 countersinks and then started working down the instructions.  Next up was prepping the #8 screw dimples and putting a slight bend in the trailing edges so they hold down better.  I really like these Avery pliers to do that.

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Then I finished up the J-stiffeners.  Just had to unclamp them, deburr, and dimple.

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The instructions suggest using a C-frame to do these #8 dimples as they will come out “crisper” than if you squeeze them.  I used the C-frame on the trailing edges, but ended up squeezing the side ones.

I still have to dimple the interior 3/32″ holes for the ribs, but I need to build an extension for my DRDT-2 for that.

So, I’ll need to make a quick stop at Lowe’s aviation department and get a little lumber so that I can run the dimpler off the edge of one of my EAA tables.  Once that’s done, there are a couple of outside pieces to finish up (countersinking the fuel cap, installing some shims, etc…) and then it’s on to the sealant!  Luckily, my hangar neighbor John used the stuff as an Air Force crew chief, so I’ll have some of his expertise to lean on.

I can hardly wait to get the tanks sealed up since things will happen fast after that.  I will finish up the leading edges (just have to put the landing light lens in) and start installing stuff on the wings.  My fuselage is ordered and should be here in early August!

 

Stiffeners and Tank Brackets

With my wife out of town for ten days, it was time to put some serious time in at the shop!  The tanks have many, many stiffeners that need to be finished off.  I rough shaped the pieces with a file and sander and finished on the ScotchBrite wheel.

Then all the holes have to be dimpled!  Careful to get them the right way!

Next up are the Z brackets that hold the tank to the spar. A lot of the part prep work is done before separating the pieces.  You ream to final size and make all the countersinks right on the whole bar.

Then it was time to cut the pieces apart.  The stock is pretty heavy, so I used the bandsaw.  Then I used a bastard file to trim the roughest part of the edge before finishing the piece on the belt sander (bulk) and ScotchBrite wheel (final).

 

My buddy Carver showed up to help.  He had been thinking about building an RV-12 or -14 as well (which is how he ended up wandering into my shop in the first place), but now he’s thinking about a Zenith Sport Cruiser.  That’s a nice plane too!  Not super zippy, but it is much easier to build and can haul a lot of stuff into some shorter strips.

I set him up working on the J stiffeners.  You drill one carefully measured hole at the end and then work your way across the tank.  He is not a “tool” guy, so I showed him how to use a marking gauge to measure from the end and a punch to start the hole.  Then we got the stiffener lined up and drilled the other holes.

I worked on prepping the Z-brackets.  The orange tape masked out the connecting surface with the tank (as it will get proseal).

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Carver had a bunch of “honey-do’s” to get to so he headed out while I kept plugging away at the Z-brackets.  All but two of them get 3 nutplates each.  So I started working through the pile until I had them all riveted. up.

Then we get to work on the tank skin.  Most of the skin parts are delivered ready to edge finish.  The tank skins still had some considerable tabs left.  I took them flat with the bastard file and then finished dressing the edge with sandpaper and ScotchBrite.

At this point, the tank baffle is inserted and cleco’d in place.  We need to counter sink all the holes.  Every 10th hole is left in its pristine state.  When we finally proseal this in place, the un-countersunk holes serve as a strong anchor to align the baffle.  We wait for the sealant to set up and then do a quick countersink on those holes.  I checked each hole with a rivet to make sure it was just barely flush.  I’ve got the countersink totally dialed in now (good as I have another 100 holes to go!).

So here’s one tank.  J-stiffener in place.  Baffle countersunk (one side).

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I’ll be taking a month long break from building at this point.  The next three weekends are full up.  My wife is back from her trip and it’s her birthday.  That means a straight zero chance of getting out to the airport.  Then we’re taking a trip out to Fredericksburg for Memorial Day Weekend (cool 1942 USO Swing Dance).  Then, I’m finally taking the course so I can get my Light Sport Repairman Inspector rating (to sign off on inspections for the RV-12). When I finally have a chance to get back to the shop, I’ll pick back up on the countersinking.  At that point, it will start to get real!  I’ll be mixing proseal and gluing up parts!