Friday, September 7, 2018

Wing Skins

These skins were a pretty big job.  I guess I'd say the size of the ouboard skins and the sheer number of holes is what makes it time consuming.  I could manage moving around the big outboard skins myself, but going slow and thinking things out was a requirement.

First thing is edge debur all the skins, doublers and J-channel.  Then put the wing walk doublers on.  These add strength right next to the wing root to make an area of the wings you can walk on to get on/off the plane.


 Be careful to orient the doublers correctly.  I saw a guy online who had interference between the J-channel and the wing walk doubler because the doubler was flipped the wrong way top-to-bottom.

On one of the wings I ended up grinding a tiny amount from the ribs where it was interfering with the J-channel also.






The instructions give you an optional step "for aesthetics" to sand down the joint between the inboard and outboard skins into a taper.  I gave it a shot with some 80 grit and an electric sander.

I put the edge of the skin on the edge of a 2x4 and sanded in full even strokes.  I tried to put more pressure on the end of the skin so it would taper.  I don't think I ended up taking off much, maybe 25% of the total thickness, but that was ok with me.  If you really wanted to make that seam even, you'd probably need even more coarse sandpaper.


Commence assembly then match drilling.  Oil that air drill up, its going to get some use!








































Priming these big suckers is actually not that much work compared to the ribs.  Just big flat surfaces.  Scratch 'em up, shoot 'em green.





































I always wait to dimple until after the skins are primed.  The akzo epoxy is bulletproof so it sticks even during dimpling.  Also, preparing the skins for priming with scotchbrite pads is much harder when there are dimples in the skin.  It tears up the pads really fast.

It was difficult to get these monster skins dimpled myself, but between moving the tables around and some physical gymnastics, I made it happen.





































Last you rivet.  There are like 2000 of these suckers to shoot, and it took Dad and I about 14 hours over three days.






You do these in a different order than usual.  Start in the middle of the skins, and rivet outwards.  The double row that joins the inboard and outboard skins is last.





































I did get a new tool to help us back rivet these skins.  I know my buddy Mike J used a straight extended back rivet set to get his done.  I presume he just nudged the bottom of the rib over to get a straight shot at the shop end of the top-side rivets.  I tried out the double-offset set from Cleavland.  It was pricy, like $50, but I think it worked really good and allowed me back-rivet quite a few more than would be doable with a straight set.

The thing you MUST do with this bar though is crank the air pressure.  On my 3X gun I had it at 60 lbs to get the job done.  I would hold the end near the rivet with one hand to keep it from spinning while running the trigger with the other hand.  























 
Done.  What a marathon!
 

Unfortunately I found out in the course of this chapter that a small number of folks I thought were close to me consider my project a joke.  So be it I guess, to each his own.  Doesn't phase me though, I know that this plane is going to be awesome and its going to haul my kids and me to some awesome adventures and memories.  Maybe I even like people betting against me, its motivating as hell.  So onto the leading edges I go!

Sunday, July 1, 2018

Wing Rear Spars

I'm way late getting this section published.  Wanted to get a picture of the kids with them and kept forgetting, oh well.

There are two parts here that are a little tricky.  Getting the holes created in the rear spar doublers and incorporating the Service Bulletin into the build.

For the holes in the rear spar, I first tried drilling large holes then filing out the remainder.  Pretty sure this is how the instructions tell you to do it.

That seemed to be more work than it was worth.  So instead i drilled the perimeter with smaller holes.


Same result, just easier to do.  Once the middle was cut out, I used a half-round bastard file I've had laying around forever.


 Oh and here's a BEEFY stiffener that is warped from the factory from the cutting process.  I stuck in in the vice, put tension on it and whacked it a bunch with a soft-faced hammer to get it straight.

The service bulletin has been out for quite a while by now, but the instructions still say to do it the old way.  They just give you some parts and a set of instructions for fixing an already assembled wing.  Its fairly straightforward, but does require a bit of thinking.  The new aileron hinge design is SUPER strong.  Here's what it looks like when complete.



Next up, wing skins!

Tuesday, May 29, 2018

Wing ribs

Wing ribs are done.  Took a couple months because of the usual excuse (house remodel).  Unfortunately I didn't get many pics.  This chapter was pretty much dominated time-wise by deburring and figuring out where I wanted to run the AoA/Pitot plumbing, power wires, and coax for a Nav antenna.

Here's a stack of 15 ribs, that's enough for 1 wing.



Early on in this chapter I made one of my few mistakes so far.  You have to cut the aft flange off the most outboard ribs, but leave just a little bit of the radius that transitions from the web of the rib to the flange.  Well I tried it with my bandsaw and butchered the hell outta it.  Ordered a new one from Vans and tried the second time with a cutoff wheel on my die grinder.  Worked much better the second time.

Here's looking at a rib attached to the main spar.  Most of them are riveted in the middle, with a AN3 bolt on the outside.  A couple of the outboard ribs don't have the bolt, just rivets.



Here's the mount for the pitot heat controller I put in.  Just some nutplates on one of the ribs close to where I'll put the pitot.  Notice the big hole there too.  That's drilled to 3/4" so a plastic conduit will run thru for wires.



This shows some little wire clips I bought.  I will use these for the Nav antenna coax so it stays separate from the power wires.  Didn't really need them in both wings, but figured it was easy now, extremely little weight penalty and leaves me with more options down the road.


Two last things.  First, priming these was a big job.  My dad and I spent 8 hours scotchbriting them then spraying.  Marathon day.

Also, for AoA/Pitot I used the left wing tooling hole for one tube, but bored another one on the other side of the rib for the other.  I asked Vans if this was ok, they said yup.  Also the plastic bushings they give you (SB437-4) are not the ones you want to use.  They fit the plumbing tube just fine, but the outside diameter requires you to drill an unnecessarily large 7/16" hole.  I found SB375-4 ones on aircraft spruce that only need a 3/8 hole but still fit the tubing just fine

Saturday, March 3, 2018

Wing Spars

Identifying left/right and top/bottom is important on these.  I marked on tape to make it hard to mess up.



As if those huge spars didn't seem long enough, the first thing you do is make them longer.  Match drill four doublers for each spar into the spar extension:



Clamp some J-Channel to the spar flanges and drill a bunch of holes into it.  You don't end up attaching the J-Channel to the spars, this step is just to use the spar as a drill template.  Pay VERY close attention to the plans when they tell you which holes to skip.  The pattern changes a few holes away from the access hole nutplates.  Figure out which holes they are talking about and tape them off.





I skipped around this chapter a bit to get all the pieces that need priming done at once.  The extruded pieces are the wing tiedown points.  They get drilled and tapped to accept eye bolts then match-drilled to the spars.



Here is the spar extension riveted.  First wing rivets!  Building juice optional:



The majority of the work on this chapter is in countersinking all those spar flange holes.  There's a ton of them!



For the nutplate countersinks, the plans specify a maximum size for the top and bottom of the countersunk hole.  I'd say an accurate measurement is mandatory here.  On the tank attach nutplates, my skins weren't quite flush with the spar flange, but it was real close.  Research showed this was OK.


The wing tiedown blocks riveted and bolted:



Aileron actuation brackets on the back side