Right Wing & Aileron Prep

I clecoed the leading edge to the right wing today.  Before doing that, I upsized the hole that is predrilled in the bottom side of the skin for the tiedown location.  After doing that and mounting the leading edge, I realized that apparently the predrilled hole was off.  The hole I had drilled with the unibit was off-center by a significant amount. It's an irritation for sure, but thankfully I was able to make the hole line up to the tiedown bracket well enough by increasing the diameter by about 1/16".

Next step was to start on the stiffeners for the ailerons.  There are a lot of these things!  I'm going to build both ailerons at the same time - things seem to go a lot faster this way.  Since I've fabricated stiffeners before. this time it went much, much faster.  When I did it before, I was very exacting about marking and cutting the stiffeners to exact sizes.  It turns out that exact dimensions for these really don't really matter.

After quite a while behind the bandsaw, belt sander, and scotch brite wheel, I had all of the stiffeners done.

Right Wing - Rear Spar Redo

I picked up the replacement rear wing spar last weekend, and today I got everything redone and swapped back onto the right wing.  It's amazing how much easier it is the second time around, mostly because I didn't have to spend hours scratching my head trying to figure something out on the plans (it helps having a completed wing to reference too).  Instead of going step by step through the instructions, this time around I took a number of liberties in the order I did things based on some lessons learned while finishing up the left wing.

First step was getting all of the holes final sized and match drilled where appropriate, then preparing everything for primer.  Priming only took a few minutes since it was 90 degrees outside and the primer dried pretty much instantaneously.  I went ahead and dimpled all of the rear spar flanges before I assembled anything.  Far easier than doing it when it's on the wing stand.

The doublers went together really quickly and before I knew it, I had the spar clecoed to the ribs and ready to rivet together.

Riveting went really well (all squeezed rivets).  There were a couple of holes in two rib flanges that were on the big size due to the original rivets being drilled out sloppily, so for those ribs I just drilled another hole and added an extra rivet to the spar.

And just like that, the skeleton is back on the wing stands.  At this stage before, I was staring down having to do a ton of work with skins, tanks, and the leading edge.  Having those pieces all done and ready to attach makes this part far more enjoyable!  I will go ahead and get the leading edge and tank temporarily set onto the spar just to get them out of the way, but next I'm going to shift gears back to the ailerons and flaps.  I'll wait to rivet on the leading edge and wing skins when I have help in a few weeks.

Ailerons

The shop is a bit of a mess at the moment.  I moved the left wing off of the stands and onto the storage cart, and moved the right wing spar to the workbench.  Yesterday I drilled out the rear  spar/rib rivets on the right wing in preparation for getting the new rear spar this weekend.  Removing the old spar was a non-event and didn't take long at all.  As soon as I have the new rear spar riveted onto the right wing, I'll get the wing mounted on the stands so I have my table space back.

I started on the ailerons today.  I decided to build both the right and left at the same time just for efficiency.  I still need to go to the store and get some thick MDF to create a super flat surface to build the ailerons and flaps, but it was nice to get rolling on something different than plain old ribs and skins for a while.  First I put the end ribs (that attach to the counterbalance tube) and doublers in place on each end of the spar and match drilled them.

The next step took a little head scratching to figure out what the instructions meant (the instructions are getting less and less detailed now, just assuming you'll be able to follow the drawings at this point).  Basically, in order to drill the counterbalance tubes to the end ribs, you have to ensure that the end ribs are held in the correct lateral position.  This is done by flipping the leading edge skin over and clecoing it to the bottom of the ribs and spar.  Easy enough to do, but it just wasn't obvious what to do based on the instructions.  Next up will be drilling the counterbalance tubes and starting the skins and stiffeners.

Left Wing - Aileron & Flap Gap Fairings (3)

I finished up the left wing aileron and flap gap fairings today.  I deburred, dimpled, and scuffed the parts (for both wings) and primed them.  This was the first time I'd sprayed the normal primer in a while, so I had to play around with the gun settings for a while to get things dialed in.  I have enough primer left to finish up the wings, but I'll have to order more for the fuselage.  That means I need to decide if I want to move to an epoxy based primer for the cockpit, or if I'll just stick with the same primer and paint the cockpit instead.  From what I've gathered over the years, the epoxy primers are tough enough on their own for high wear areas (especially since I'll be putting interior panels and carpet in), but the standard primer would probably get pretty beat up without a harder paint finish.

If only riveting all areas was as easy as this.  Except for a couple of spots, the squeezer worked fine.  It didn't take long at all to get both gap fairings riveted on.

Left Wing - Aileron & Flap Gap Fairing (2)

 I wanted to be able to work on the ailerons and flaps without having to crawl around on my knees, so I flipped the left wing over and moved it over to the rolling cart.  This is where it'll live for a few years until I'm ready to rivet on the bottom skins.

Since I still have work to do though, I rolled the wing cart over into my normal work area.  It's tight, but there's enough room to finish up with everything without taking up another bay of the garage and forcing a car to live outside (yet).

I got the gap fairings match drilled and started deburring and dimpling.

Left Wing - Aileron & Flap Gap Fairing

Today I received the shorter offset rivet set (for universal heads) that I ordered.  I needed this in order to buck many of the rivets in the flap bracket assembly.  The longer set that I had was long enough that the rivet gun wouldn't fit in the rib bays.  I'm not a huge fan of the offset sets because they tend to spin in the gun and are harder to control, but sometimes there just isn't much of a choice.  It didn't take long to get all of the flap brackets and attach angles finished up.

Next up are the aileron and flap gap fairings that create a kinder path for the air to flow.  They attach to the aft side of the rear spar and also the top skins.  I started to cleco them in place, but quickly realized that working on them with the wing on the stands was going to be a lot harder than it needed to be.  This weekend I'll relocate the wing to the rolling cart, where it can sit nose down.  That way the aft portion that I need to work on will be easier to access.  There are a lot of holes to prep and rivets to set, so I'd rather be comfortable doing it.

Left Wing - Flap Brackets (2)

Each flap bracket (3 per wing) gets two attach angles - one that rivets to the rear spar and bracket and one that is primarily riveted to the skin and bracket.  For the first angle, it was a simple matter of clamping them in place and match drilling through the holes in the rear spar.  Then the same is done drilling through the holes in the bracket.

The second angle ultimately has to be flush with the skin.  To accomplish that, I just needed a flat reference from the rear spar flange to the rib flange.  Easy enough with a speed square.

Like the other angle, these were also just clamped and drilled to match the holes in the bracket.

For the angle that gets riveted to the skin, those holes need to be drilled by referencing the holes pre-punched in the skin.  I hung the lower skins back on the wing so I could do the match drilling.

The skins fit great except for the middle bracket cutout, which was just a hair too narrow.  After I pulled the skins back off I hit it with a file to open it up a bit.

The last thing for the day was riveting the angles in.  The inboard angle went fine, but the middle bracket angle was a nightmare for some reason.  I think the spar holes and angle holes were slightly off, because every time I put a rivet in I clinched it, probably because they were at a slight angle.  I drilled out multiple rivets and had the same problem over and over.  I finally emailed Van's to see what they would think of just adding two additional rivets to the spar/angle to make up for the bad rivets.  If this is okay, I'd rather go this route, since continuing to drill the rivets out will inevitably cause the holes to enlarge.  If Van's doesn't want me to put additional rivets in, I'll have to remake the angle piece and try to get the holes aligned better.

Side note - this rattle can primer doesn't like to be beat around with tools.  It's fine when things go well, but for this problem angle, by the time I had tried to buck the rivets a few times, the primer was in rough shape.

Left Wing - Flap Brackets

I'm finally moving on from playing in proseal!  I have to say, while I'm no longer afraid of working with the stuff, I'm definitely glad to move on to some other types of build again.  The brackets that attach the flaps have a little minor fabrication to be done of some aluminum angle.  Van's doesn't label the angle stock, so I had to dig around in the crate to figure out which pieces to use.  A few of the pieces are pre-cut to length because they also have a bend that the factory puts in one edge (to clear the wing's rear spar flange).  The others are cut from a long piece of angle.  I cleaned everything up and deburred the edges.

I primed all of the attach brackets with rattle can primer.  Since the lower half of the brackets will stick out from the skin and get wiped off down to bare aluminum and re-primed when I actually paint the plane, I didn't bother pulling out the Stewart primer for just these few parts.  It's amazing how much softer the rattle can primer is though. Granted, I suppose I'm not really giving it any time to cure.  I just let it dry and started putting things together right away, so I'm sure that's why it didn't hold up very well.  It's good enough for a layer between mating parts though, so it'll do the job just fine.

A lot of the holes that have to be drilled in the ribs to match the brackets are in very tight quarters.  Too tight to get a regular drill in.  I had read this ahead of time in the instructions, so I bought a right angle drill attachment.  A regular right angle air drill is ridiculously expensive for some reason, but for $30 I got a nice Dewalt right angle setup that uses hex bits.  It has multiple attachments, so can either be driven directly by the drill, or it also has a flexible shaft.  I just used it directly attached to the drill for this work, but I can definitely see how the flex shaft could come in handy someday.  A worthwhile $30.

After drilling all of the brackets (3 for the flaps), I got them riveted in place.  It was a mix of using the squeezer and the rivet gun, depending on the rivet location.  The bottom row of holes, as well as the holes by the rib flange (lower wing surface) don't get riveted until the angle pieces I made above are match drilled and riveted at the same time.

The instructions have you pull a string line between the inboard and outboard flap brackets to ensure that the middle bracket hole is lined up properly prior to drilling it to the rib (the internal most rib is the only one that is completely pre-drilled, but the middle and outboard ribs just have two holes drilled in the ribs for reference, then the rest of the holes get match drilled from the pre-drilled brackets).  I think this instruction must be a leftover from when this middle rib didn't have any holes drilled in it though.  With the reference holes that the rib came with, there's really no way to move the bracket.  I double checked with a string line though, and sure enough it's spot on as-is.

On the middle attach bracket, there's really no way to rivet the lower row of rivets by the rear spar and follow the best practice of having the manufactured head on the thinner material.  Because of the SB fix that Van's calls out to reinforce the aileron attach bracket (rare reports of cracking without it), the extra piece of angle makes getting a rivet set in there pretty impossible.  I'll just have to flip the rivet direction here and put the manufactured head on the other side.  The only reason the standard is to put the manufactured head on the thin material side is to minimize puckering of material.  Since this rib is already riveted to the solid bracket in so many places, that's not really going to be a problem though.

Right Fuel Tank - Fixing a Leak

 A couple of days ago I leak tested the right fuel tank.  Everything looked good except for one small area at the outboard top corner where the baffle and outboard rib meet.  These corners are notorious for having leaks because of how they have to be put together (put a huge blob of proseal sticking up in the corner and hope it smooshes down just right in all of the right places when the baffle is pressed down - there are actual gaps it has to fill, whereas in all other areas it's sealing two tight surfaces together).

The leak can be seen where the bubbles are coming out between the baffle and the skin between the last two rivets.  The other bubbles are just from spraying the solution.

Luckily, this area is right inside where the fuel cap filler flange is, so access was easy.  I pulled out my borescope and stuck it in so I could see what the proseal looked like in the corner.  As expected, it was kind of a mess.  It's super thick because I put a big blob there, but apparently there were still gaps somewhere.  To fix it, I just used a gloved finger and spread a bunch more proseal over the corner and along the edges.  It's a lot of sealant, but after leak testing again (a few days later - I'm late updating) it seems to have done the trick.  No more leaks.  If I remember to, I may do one more leak test on each tank just before I install them on the wings for good.

Right Fuel Tank - Finished!

Calling the fuel tank "finished" before it's leak tested might be jumping the gun a bit, buy I'm optimistic.  Today was a long day, but once you start closing things up, there aren't a ton of great stopping points.  All in all, it went pretty well.  I modified a few processes from the first tank, did better at some things, and created new mistakes with some things.

One lesson from today is that when there is something that needs to be done, I need to mark it in a very obvious way, otherwise I just forget all about it.  Case in point, in my final inspection of the internals of the tank, I decided there were two small areas at the front of two ribs that I wanted a little more proseal on.  Because I hadn't mixed up the proseal yet, I didn't have any handy to just dab on at the moment.  Fast forward a while and as I started riveting on the baffle, I remembered.  Too late.  I think it's probably okay because I was just going to add more out of an abundance of caution, but I won't know for sure until I leak test everything.

One thing that got me on the first tank as well as the second tank was the fit of the baffle.  I don't know what the deal was, but on both tanks, the lower side skin was skewed by maybe 1/64", so the holes for the baffle/skin joint were slightly off.  The baffle went together with clecos just fine, so I didn't notice the issue until I started putting rivets in (they wouldn't go in).  I'm still not sure what happened, especially since the exact same thing happened on both tanks. I had to hit each hole with a reamer to just knock a little bit off of the hole.  Even with that, the rivets wouldn't sit perfectly flat (because the skin in that area is countersunk, not dimpled - the dimples would have had a lot more forgiveness).  They are just slightly at an angle - just enough to be able to catch a fingernail on one edge of the manufactured head.  The top skin is perfect, so I'm not losing much sleep over it.  It won't be noticeable for anyone who isn't out to find errors and crawling around under the wing!  It was just a bit strange to have this happen on both tanks.

After finishing the baffle/skin joint, I got the Z-brackets installed, then sealed up the access plate.  I flipped the tank over to let gravity do its work and pull the proseal down onto the baffle joint while it sets up.  Before I put the access plate on, I took a quick look, and at least as far as I could see, there is a nice bead of proseal along the baffle.  It's pretty cool out right now, so I'll probably give it 3 or 4 days before I leak test it all.