16-02 -> 04: Riveting Wing Top Skins

Well, this section took a LOOONG time! 

The riveting of the top skins on the left wing began on 14 Jan 2021 and the last rivet on the right wing top skins was 30 Apr 2021. The delay was basically due to needing a riveting partner as i elected to backrivet all the skins.  

Setup

I used the workbench extension for my wing spars and setup the wing spar to be level using a string line along the length of the spar flange holes, as well as a digital level to ensure that there was no twist in the spar. The wing skins were then clecod on. 

Spar was clamped to the bench at one end..

and screwed through a tooling hole at the other end. 

A digital level was used to ensure there was no twist. 

I used a very large offset backrivet set and for all the rib to skin and spar to skin rivets, with the exception of those on the rear spar where there were doublers - this tool just didn't fit there. For those i used various bucking bars and the swivelling mushroom set. 

Big Berfa!

This massive set needed about 60psi to get a rivet set in 6-7 hits. 

The cardboard was there to protect the spar flange

Some of the more difficult rivets required some bucking bar modification. 

and a bit of high-ropes work. 

here the offset footed bar had to be ground to clear the manufactured heads of the rivets on the inner rear spar doubler 

A squeezer was used to install the rivets on the first rib, and the screw holes where the wing gap fairing will be located, was countersunk with a #21 initially until it bottomed out on the threads in the nutplates, then a #30, as the pilot of the #30 nests inside the threads of the nutplates nicely. 

The offset nutplates are clecod on, then a screw inserted to hold them in place while the rivets are squeezed. 

I get by with a little help from my friends

Since i was backriveting all the top skins, i could not have done it without some excellent bucking bar partners:

Dad on the bar

John, my father in law

Kingsley, looking pretty serious!

My once chief pilot, Mark Rooke (trying to look serious).

This bloke.

Every good artist signs their work!

Outboard Aileron Brackets

Closing out the section was the last task - to rivet on the outboard aileron brackets. These were done with the short cupped set and long offset set, and tungsten bucking bar. 

Look mum - no clecos!

Purdy

The leading edges and fuel tanks have already been done, so the next step is to install them on the wings!

COVID: Working out of order

 A short post to explain why it seems like i'm working on multiple sections at once! 

Due to COVID, i have been unable to rivet the top wing skins to the spar / rib assembly. I know a few builders have done this solo, but i would prefer to back rivet these using a long back-rivet set i have borrowed from a mate of a mate; so for now the top wing skins completely ready for installation, but are in storage for now. 

Since they were on hold, i decided to keep moving by beginning work on the leading edges. Again, i got to a bottleneck with this section. I completed the riveting of the leading edges however, since the top wing skins are installed with the spar shimmed to level on the work bench, I could not complete the chapter by riveting the leading edges to the spar. 

So, moving on to the fuel tanks! 

16-02: Wing Skins Prep / Wing Skins on Hold

Next up was working on the 4 wing skins. These consist of a thicker inboard skin (0.032") and a thinner (0.025") outboard skin, as well as 2 doubler plates underneath the "wing walk" area (over the 4 inboard most ribs, underneath the inboard wing skin).

Blue Stick

As always the first step is to remove the blue around the rivet lines, and to lay out the wing walk doublers on the skins to get the right part in the right place (and label them). I have found using a wooden stick is better than a metal ruler, as it does not sink any heat out of the soldering iron.

Wing Walk Doublers

16-02 starts with clecoing the wing walk doublers in place and match drilling the skins. 

The J stiffners were put in place to check for any interference - the forward wing walk doubler needed some TLC on both the forward edge (to clear the spar) and also the aft edge (to clear the J stiffner flange). 

The forward wing walk doubler interfered with the J stiffner... 

...and also contacted the spar flange and had to be relieved.

 Wing Skin Overlap

Next, the area where the 2 wing skins overlapped needed to be filed / sanded to reduce the thickness, such that the 2 skins together, equal the same thickness as the fuel tank skin forward of where they overlap. To do this i used a file initially, then sand paper. The skins were clecod to a piece of MDF in order to keep them in place and flat (and to check the thickness). 

Looking back from the "tank skin" (aka a piece of 0.032" scrap) toward the reduced thickness wing skin overlap

At the trailing edge, the 2 skins needed a little TLC so they didn't catch on each other. 

Here you can see how the skins just slightly interfered with each other - a piece of sandpaper was used to open this gap up (to the thickness of the sandpaper)

Prime Time and Dimpling

Next up the skins were cleaned, etched and primed

The holes were deburred where there was a little lip left by the punch

Before priming

While being etched and scrubbed

Hung out to dry (after being rinsed with the hose)

Being primed

This is the feathered edge of the paint spray - only a light coating was sprayed on the skins - no need to go too thick, but need 100% coverage. 

After priming, the skins and wing walk doublers were dimpled. 

Dimpled???? 😶

Yes - i elected to dimple ALL the ribs, the wing walk doublers and also the skins. Sub-Structure dies were used on the ribs and also the wing walk doubler skins. The wing fairing screw holes will be countersunk as per the plans (countersunk through the skins, doublers and ribs). 

Wing walk doublers dimpled

Dimpling the inboard skin

Dimpling the outboard skin

Pausing the Wing Skins

Due to COVID and the enforced lockdown in our home state here, i am unable to get my bucking partner (my dad) over to help with the backriveting. So rather than try and do these solo, i have decided to move onto the wing leading edges.