Right Wing - Tank (5)

Yesterday I hit the Z brackets with some rattle can primer so that I'd be ready to do some more work today.  Thankfully that primer is just about gone so I can try something else.  It just lays down really strange on corners, as opposed to the Stewart primer that sticks great.  Once the tank is fully built, I'll hit the back baffle with primer anyway, so these brackets will get another dose.  Because of their shape though, it would be really hard to prime up underneath the overhand once assembled on the tank, which is why I did some preemptive priming.  I didn't prime the bottom surface that will butt up against the tank baffle, because that will have a layer of proseal on it.

Today I started with the Z brackets and countersunk the holes for the platenuts and riveted the platenuts on.

I tried to remember a few of the lessons I learned on the last tank and fabricated the inboard attach angle.  I got this one positioned appropriately this time, so it didn't shift while I drilled the holes, like the last one did.  The actual fit is still TBD.  These attach angles fit inside the rib flanges at the nose of the rib, meaning that there will be rivets from the rib/skin protruding through the rib flange around the perimeter of the angle that could interfere with how the angle sits.  I think I've got just enough room around the perimeter of the angle to allow for the rivets, but it's hard to know until it all goes together.  I can always shave a little off if need be.

I fabricated the inboard and outboard rib doublers.  These aren't really doublers in the sense of being in place to just stiffen up an area.  From what I gather, they're really mostly inserted at the nose of the rib to help block all the notches at the rib flanges from fuel leakage - these pressed up against the rib and skin, along with proseal, will keep those big flange notches from leaking.  Just using proseal on its own would be iffy, because the spaces from the notches are pretty significant.

As I was getting my pneumatic squeezer ready for the next task, I noticed that the yoke was wiggling a bit, even though the pins were in place.  It turns out, one of the pins had snapped in half.  I'm not sure how that would have happened, outside of a manufacturing defect.  I'll email Cleaveland Tools about it. I'm sure they'll probably just replace the pin for me.

I match drilled the holes from the attach angle through the inboard rib (and drilled the doublers shown above).  Then I got out the spinning wheel of death - fly cutter - and cut the access hole in the inboard rib.

It didn't seem all that cold today,  but by this point my fingers were ice cold, so I finished up by deburring the access plate doubler ring, match drilling the screw holes to the rib, then match drilling the smaller nuplate rivet holes to the rib.  The rib gets dimpled to accept the rivets for the nutplates, and the doubler ring gets countersunk to go over the dimple.  I limped along with my broken squeezer and got the ring and nutplates riveted to the rib.  With that, I'm done with most of the initial assembly of the tank, outside of match drilling the fuel filler flange and fuel drain to the skin.  Then I will start prepping the parts of this tank (deburr and dimple skins and ribs mostly) and move back to finishing up the right wing prep (deburr and dimple skins and ribs and countersink a billion holes in the spar).

Right Wing - Tank (4)

Lots and lots of drilling on the fuel tank today.  I match drilled all of the rib to skin holes, as well as the baffle.  Then I countersunk all of the holes in the baffle/skin holes and enlarged the holes along the edge for the screws that attach to the spar.

The platenuts for the inboard Z bracket get attached to the spar instead of onto the Z bracket.  I'd forgotten how big of a pain this was on the last tank.  I wish I had done these before I had riveted in all of the ribs.  There is very little room, plus there's a doubler underneath that makes bucking really difficult.

I started prepping the Z brackets for the platenuts using a jig to drill all of the holes.

I had to pause there, because I can't seem to find all of the platenuts I need for the brackets.  If I have to order more, I'll probably just go ahead and order a bunch of various hardware.  I can't exactly get this stuff locally, so just being short one bolt means $5 in shipping.  I'll get some of the most commonly used nuts and bolts, platenuts, washers, etc and hopefully have enough to spare throughout the build.

Right Wing - Tank (3)

To start off the day, I decided to make a 10 minute task an hour long task.  It's Saturday, so why not?  I attached the doubler to the rear spar, which should have been pretty straight forward.  There are a number of holes that need to stay empty because they are used to rivet another part later on.  I carefully kept away from these holes and riveted everything else.  For my very first rivet, I didn't have the squeezer set right and it completely over squeezed, so out came the drill to drill it out and try again.  The second time it went a lot better.  That is, until I got to one very awkward spot and didn't get the rivet seated in the countersink.  So here comes the drill again!  With that one fixed, I realized I had one more rivet to go in the inboard rib flange.  I put that in, squeezed it perfectly, and stepped back to admire my work....that was one of the holes that was supposed to stay empty for now! My drill got a good workout today.  

Next up was making the stiffeners for the tank.

I've made so many stiffeners in the build by this point, they are pretty quick to finish. After cutting, sanding, and smoothing the edges, I attached them to the tank skin and final drilled them.

The Z brackets for the tank baffle were just as time consuming as I remember.  In fact, I don't really remember much about doing them on the last tank.  The orientations of the flanges are not the same, so after my riveting fiasco that started the day, I was careful to check and double check before I started drilling.  Each flange gets one reference hole drilled in them first, then that is used to cleco the bracket to the baffle and match drill the rest.

The end brackets are clecoed on, but the internal brackets have to be blind riveted on in order to test fit everything to the spar.  Hopefully drilling the blind rivets out goes easier than it did last time.

I put the tank onto the spar and match drilled all of the Z brackets to the spar, as well as the outboard end to the splice plate that connects it to the rest of the leading edge.  Then the tank came off the wing again.  Next up will be match drilled everything, finishing the Z brackets, and prepping the spar and wing ribs (countersinking and dimpling).

Right Wing - Tank (2)

I received the replacement rear spar doubler from Van's today. It took all of 5 minutes to deburr and countersink the correct side this time.  I can't remember if I mentioned it before, but for whatever reason, a couple of weeks ago I accidentally flipped the original part over during my prep work and countersunk the wrong side.  Thankfully, all of the mistakes I've made up to this point have been on very cheap parts that are easy to replace!  In the grand scheme of things, I'm more than happy to shell out $10 here or there for replacement parts to get the final quality I want.

I tried to prime this part really quick using the little Harbor Freight airbrush I used on some small parts a month or so ago.  It turns out that my grand plan of just capping the tube of the airbrush and being able to pick it up and spray easily was pretty far fetched. I had cleaned most the airbrush up after my last use, but apparently not well enough.  The tiny, tiny parts were clogged with old primer. I cleaned it up again and got it working okay, but since the whole point of it was to make priming small batches of parts easy and fast, I think I may give up on it and go back to spray can primer.  The spray can primer I have now is just ridiculously smelly, so I'll grab another brand once it runs out.  The airbrush works really well for what it is, but it's just not as convenient for grab and go priming as I was hoping.

I buckled down and got to work on the tank next.  As was the case on the last wing, the tank is much harder to work with than the outboard leading edge.  It still went together far easier this time around though.  I got all of the ribs clecoed in place, so this weekend I can get rolling on fabrication of the other parts.

Right Wing - Tank (1)

Because I'll need the leading edge assembled and mounted to the spar of the wing in order to fit the tank, I went ahead and reassembled it tonight.  As I was doing it, I noticed that the inboard most rib that goes under the joint plate got off center when drilling through the joint plate.  All of the holes are fine except for the very last two, which don't have the edge distance they should.  Van's has said before that a minimal edge distance in these locations is pretty common and not a concern here, but I've sent pictures off to them for this particular case just to verify before I just call it good.

In the meantime, I went ahead and installed the assembly back on the wing just to get it all out of the way.

I was severely lacking in the energy department tonight, so I didn't get very far on the assembly of the tank before my brain started misfiring.  I sanded down the nose of the ribs to even out the flanges (no leading edge skin bump that way) and started inserting them into the skin.  My head just wasn't in the game though, so I decided to hang it up and come back to it another night.

Right Wing - Leading Edge

The real test today - would the lessons I learned doing the leading edge on the left wing actually make a difference and make building this one any easier?  It turns out, yes!  Getting the ribs in the skins this time around was far easier and probably took me 15 minutes, as opposed to the hours and hours it took last time.

Once the leading edge was built in the cradle, I transferred it to the wing itself and started all of the final drilling.

The plate that joins the inboard portion of the leading edge to the tank gave me a little trouble just because of how tight everything is, but after I put some Boelube on it (used for drill bits, but worked fine for just providing a slicker surface), I was able to slide it in and get the holes drilled into the inboard rib.

The leading edge should be left clecoed together at this point, because once the tank is done the two need to be attached to the spar together so the joint can be match drilled.  I noticed that the rib flanges on the very leading edge were not sitting flat though, causing a little bump in the skin.  I forgot that I hadn't taken the ribs to the Scotch Brite wheel to  round off these hard corners before I assembled the ribs with the skin.  There's nothing wrong with it structurally as-is, but I don't want the slight bump in the skin if I can help it.  So I went ahead and pulled everything apart and took a little meat off the nose of the ribs to smooth everything out.

With that, it's time to start the second fuel tank.  I still have a lot of prep work to do on the skeleton and all of the skins, but I'll probably go ahead and work on the tank and then just do all of the skins at once.  Hopefully in a week or two the weather will be warm enough that I can actually spray a little primer in the sun outside.  It worked out fine doing it in the garage, but the primer dust on everything is pretty annoying. The prep work required to get to that point is pretty significant still - lots of cleaning of the skins, then scuffing and dimpling before priming.

Right Wing - Bottom Skins

First on the list for today was to cut the J stringers and get those match drilled to the top skin.

The bottom skins were next.  Nothing exciting to write about - lots of clecos and a lot of drilling.

And just like that, progress goes into rewind.  With the bottom skins drilled, the next step is to work on the leading edge skins, so the bottom skins come back off.

Right Wing - Top Skins

Not much to say for tonight, except drill drill drill.  I finished match drilling the wing walk doublers and final drilling all of the top skins.  I definitely used fewer clecos this time around.  I learned that last time I really did overkill in terms of how many holes I clecoed when lining everything up.

Right Wing - Skins

Tonight I finished riveting the main ribs to the front and rear spars.  Well, mostly.  I had to leave the last two inboard ribs just clecoed to the rear spar for now.  I'm still waiting on a doubler plate from Van's that goes there, but it'll be easy enough to add later whenever it arrives.

After the ribs were all done, I drilled a 3/16" hole into the outboard rib to attach the aluminum angle used for hanging the spar on the wing jig.  Things like this do go faster the second time around.  I still have to read and study the plans to find rivet sizes and measurements, but the overall process is a little quicker just because I don't have to spend the time interpreting the plans and figuring out what they REALLY mean to say.

With the wing hung, I started on the skins.  I measured and laid out the wing walk doubler and got the 3 reference holes per rib match drilled to the punched holes in the top skin.  Then I awkwardly hung the top skins on the spar and got them clecoed in place.  Next up will be clecoing them to the ribs and then drilling to final size.

Right Wing - Rear Rib Assembly

Time to put things back together again!  Before the main spar goes onto the jig, all of the ribs (minus the outboard rib) need to be riveted on.  I did remember a few gotchas from the last wing, so was able to change the order of a few steps here to save me some time down the road.  For example, the rib flange tabs that slide under the spar are supposed to get final drilled later on with the skin and spar.  I learned last time that that's kind of pointless though.  The rib tabs are super flexible, so move all over the place and inevitably get drilled oblong if done with everything else.  Instead, I just final drilled those tab holes to size on their own and did the same for the matching spar holes.  That way the tab can simply be moved into place when it's time to rivet, which given the flexibility should be fine.  Normally you drill things to final size while assembled so you can take out minor variations in layout (even 1/1000" offset each direction between holes in different material can make getting a rivet in a pain), but there are some pieces where that's just not worth it.  I think this is one of them.

I tried out one of my 3D printed bucking bar gauges on the ribs.  This particular one is going to be replaced with a slightly different version, but for the meantime, it worked great!  It creates very consistent rivets, and most importantly, protects the spar from getting dinged by the bucking bar.  Between that and the plastic caps for the long rivet set on the gun, riveting was significantly easier and less stressful than my first round on the left wing.  I got 4 ribs riveted on tonight and will finish the rest next time.

Right Wing - Rib Priming

The sun came out this afternoon and the temperature started to creep up, so I took advantage and got the wing ribs primed.  I had to blast the propane heater in the garage for about 30 minutes, but it worked well enough to bring the garage temperature up to about 65 degrees.  I'm starting to learn how to get the spray gun dialed in pretty well, so little by little I'm gaining confidence that I'll be able to actually paint the plane when it comes time.  With the temperature warm enough (maybe still slightly cool), I was able to move through parts with almost no downtime, so doing all 15 ribs didn't take all that long.

The big downside of spraying primer inside with the garage doors closed is that by the time the session is done, the entire garage has a layer of primer dust on it.  HVLP guns are great, but when you're painting small parts and edges, a lot of primer overshoots and goes into the air.  I could narrow the fan shape to cut down on the overspray, but that would really slow things down, plus it makes it harder to get a good finish because the overlap is more severe vs tapered.  The excess spray dries in the air before it settles on anything, so it doesn't stick, but it sure makes a lot of dust!  While I do have the paint booth I could set up, it's a rather permanent thing and I don't really want to lose space to it until I'm ready to paint the plane.  The booth will have box fans and filters in it to create negative pressure and keep the spray dust to a minimum.  The other thing I've decided based on my priming experience is that I will definitely buy a bunch of LED light strips to hang all over inside the paint booth.  The first coat of primer or paint is relatively easy to see, but the subsequent coats of the same color are really difficult to see unless you have gobs of tangential lighting to see the wet edge.

Right Wing - Rib Prep

Today was all about prepping the wing ribs to get ready for priming.  I'm hoping that the temperatures get back to around 50 tomorrow.  I think that's enough to heat up the garage a bit and get the priming done without too much downtime for drying.

Just like in the left wing ribs, I drilled a 3/4" hole in the bottom portion of each rib web for the wiring conduit.

I've tried every flavor of aluminum prep for priming.  The bottom line is the aluminum has to be cleaned and etched (well, it actually doesn't HAVE to be etched, but my testing has shown that the primer does indeed stick better with the etching, so I think it's normally worth the effort).  How the metal is etched is the question.  In the past I've mostly used the EkoEtch as an acid etch/cleaner.  This stuff works great, but it requires the metal to be rinsed with water afterwards.  When the temp is 30-40 degrees, that adds at least a day of priming since the water doesn't dry quickly.  Instead of using the acid etch, this time I just manually scuffed with Scotch Brite.  That still takes forever on ribs because of all the bumps, especially the fluted spots on the flanges.  Once done with that, I cleaned with acetone until the rag didn't pick up any aluminum.  It took a few hours, but now I'm ready for priming tomorrow. 

Once I'm done with the wing ribs (still have to do the leading edge ribs as well as flaps/ailerons), primer prep should get considerably easier for the rest of the plane.  The wing ribs are just very awkward to do, and the fact that there are so many of them to do is what's killer.  I'm very glad I had already deburred all edges last summer while I was waiting to get the tail.  Having to do that at the same time as the rest of this would have been rough.  Scuffing the big surfaces like skins should be pretty quick, so not that big of a deal.  I've found that for flat surfaces, just putting a Scotch Brite pad onto a random orbital sander makes very quick work of it.

Right Wing - Drilling Ribs

Here we go again!  I pulled the dusty right wing ribs off the shelf and clecoed them to the spar to match drill.  The part that is eventually going to bite me here is the fact that the plans only show a left wing, so there is a little bit of mental juggling to do to make sure you get all of the ribs oriented correctly (meaning if the plans show a rib with an "R" or "L" designation for the flange direction, you have to remember to reverse it for the right wing). 

And of course after the ribs were assembled and drilled for the front and rear spars, then everything came apart again.  You'd think I'd be used to it by now, but it's still kind of depressing how quickly things go from looking like there is progress to just a pile of parts again!  I deburred all of the freshly drilled holes.  Lastly, I grabbed the wiring conduit drilling template I had made for the left wing ribs and marked each rib for the conduit location.  I pilot drilled the holes, but stopped at that point.  Next time I'll pick up by drilling the 3/4" conduit hole and then checking that all of the rib edges are deburred well enough (did that task last summer thankfully!), following by cleaning and prepping for primer.  I'm truly stuck at this point since the ribs have to get primer at this stage, so I'm going to have to just bite the bullet and try to blast the heater in the garage for a while this weekend to get things warm enough.  I've found that the primer still lays down well enough in the cold temperatures, but the drying time is the show stopper.  Whereas the primer will flash off in minutes in the warm temps (60-70's) so I can spray the second coat very quickly after the tack coat, in the cold temps it can take 30-60 min for the first coat to dry.  That really extends a priming session when there are 15 ribs to do!