22-09: Riveting Aileron Trailing Edges

The riveting of the aileron trailing edges was done in the same manner as the flaps.

First, the trailing edges were cleaned and etched. They were dried in the sun then given a clean with some acetone. I then applied the VHB tape to both sides and let it sit for a day. 

I started on the right hand aileron - the trailing edge was clecod into position using the square tube (from the flaps) on the top side of the skin. I then checked to see if the aileron was true, by placing it on the known flat table, and checking for any twist. You can see from the winding sticks there is a very very slight twist in the aileron. Approx. 3/32nd of a twist.  

So before removing the tape and bonding the trailing edge in place, i decided to weight the aileron to the known flat table, and try and get some of the twist out. I used whatever i could find that was heavy. 

I then removed the tape on the trailing edge, and let it setup overnight. I then checked the twist once again and it seemed a bit better. With the aileron still weighted down, i set the rivets for the counterbalance to the skin. 

I was then able to remove the weights and gently stand the aileron up. I used the same method for riveting the trailing edges as the flap - I used the pneumatic squeezer, and first partially set the rivets with a modified parallel set, then with modified set which matched the angle of the trailing edge. 

Nice and straight

This shows a partially set and finally set rivet. Along with how the sets align with the top and bottom surfaces for each step. 

A partially set rivet is on each side - the one in the middle is fully set.

On the top is a normal flat die. On the bottom a normal flat die, but one which has been ground down on one side to clear the skin a bit more, and allow more of a set of the rivet. 

On the top is the same flat die. On the bottom, a modified die which has been ground to the same angle of the skins. This final sets the rivet into the dimple. 

After riveting, i placed the finished aileron on the bench and checked for twist again. The weighting really helped - the twist was 1/16th  - i think that is acceptable. Of note, the left flap was perfect - no twist at all before or after riveting. 

Of course, i had to skip ahead and install the ailerons on the wings. 

Nice and straight and aligned with the flaps in reflex (full up) position.

The left aileron - also very straight.

It really aligns with the flaps well. So impressed with this kit.

This means - Chapter 22 is done! But not without a bit of waggling... 

22-08: Aileron Bottom Skin Riveting

Before i committed to riveting the bottom skins, i setup the trailing edges for countersinking so i could cleco the trailing edges in place and check for twist on the aileron. 

The countersinking was done in much the same manner as the other trailing edgessuc as  for the rudder and the flaps.

Checking for Trueness

Since i went to such an effort to check the leading edge assemblies were true, i thought it was a good idea to also check the bottom skin. This called for on page 22-08, Step 7. 

The digital level hasn't worked very well for me, however using winding sticks seems to work a bit better. Here i have setup the aileron so it is high enough to allow the use of the sticks and suported across its length. The bottom of the aileron isn't completed flat, so this check is not 100% accurate. 

I marked the centre of gravity of each stick, and placed them so the centre was aligned with the same rivet at each end. The idea of the sticks if you can sight down the length of the aileron, and the amount of blue tape should be even if there is no twist. There was small amount of twist present in each aileron, so i was able to twist this out. Then i gently stood the ailerons up (hopefully not twisting them out of shape). Fingers crossed.

These marks show the centre of gravity of the stick

This is the left hand aileron before riveting.

This is the left hand aileron after riveting. 

This is the right hand aileron before riveting.

After fixing the trist, these looked farily straight, so after standing up, i was able to remove the trailing edge, and reach in to rivet the bottom skin to spar rivets. I used the small tungsten bucking bar, and the gun set to around 30psi. I used a swivelling mushtoom set. The -3.5 rivets called out were too short, so i used -4 length.

I placed some tape on the aileron to allow me to set every 10th rivet (round 1), then the ones in the middle of those (round 2), then the ones in the middle of those (round 3) etc. 

To get to the last rivet in the line - the ones which hold the tiny tab from the end rib to the spar and skin, i had to use a non-swivelling mushroom set. These tabs were lifting off the assembly quite a bit. To fix this, i placed a plastic tube on the rivet and pushing really hard on the bar side, i set the rivet partially. This swelled it a bit, and held the tab in place. I could then remove it and set the rivet fully. 

I used this set to get into the corner rivet. Danger Will Robinson!

The tube is supposed to push the rib down using the force of the buking bar until the rivet can set. But it will not set fully with the tube in the way.

Here it is partially set - only a few hits with the gun to get it here, but a lot of pushing on the bucking bar.

Here it is final set. 

Once the bottom skin was done, i clecod the trailing edges back in place along with the square tube (at every second hole) and used pull rivets on the end ribs. 

Preparing the Trailing Edges for Tape

Next up i cleaned, etched and scrubbed both trailing edges and left them in the sun to dry. Once dry i wiped with acetone, and applied the VHB tape to both extrusions ready for attaching to the trailing edges in the next few days. 

Clean!

22-07: Nose and Top Skin Riveting

Riveting ribs to the nose skin

Next step, the plans have you rivet the nose ribs into the nose skin. There are the 2 nose ribs already attached to the counterbalance, and the inboard end rib. I clecod these in place, as as you can see the skin is all over the place. Apparently this is normal. 

I was able to set most of the rivets using the squeezer. The 2 forward most, upper skin rivets are marked as MK-319-BS rivets on the plans. They call for drilling to #34 - i don't have one of those. Everywhere else in the plans it says #33 - so i just used that. In addition, i needed to use a MK-319-BS rivet on each of the 1 x lower forward most holes. Since i installed the screws holding the counterbalance with the screw heads in the tube, i could not get a squeezer in there with the screw 'tails' in the way. I also ended up using a MK-319-BS rivet on the forward most bottom hole on the inboard rib, because I did not have a squeezer yoke with enough reach to get this rivet. 

You can see the lowest rivet on the left hand side of the image - i could not get a squeezer in there due to the tail of the screw being in the way. This got a MK-319-BS.

It is very disconcerting to see this waviness - but it is apparently normal. 

Pull rivets were used also on the top 2 forward most holes.

The lower rivet here on the bottom skin had to be a pull rivet - the squeezer did not have enough reach. 

Before the spar goes in, the tiny inboard doubler was riveted to the spar. 

Next up, i clecod in the spar. I noticed that the #30 holes where the spar clecos to the ribs were not in great alignment. They needed a lot of help to get the clecos in. I thought the spar might have a twist in it, so i checked the spar for twist using some winding sticks, and gave it a little tweaking to get it true. 

I then clecod the spar in place and checked for twist again. And there was a lot of twist! Not knowing what to do, and assuming it was not a good idea to rivet the skins on in this state, i asked a question about Aileron Twist on the VAF Forums.

The response was basically to twist the assembly to be true before i rivet the skins on. Scott from Van's reckons this is normal, but my experience from the flaps is that if you start with a true spar before any skin riveting is done, you are a lot better off. It is much harder to take out twist with the skins installed.

It doesn't feel right for this to fit so badly...Nothing in the kit so far has been so far off.

This was how i used the winding sticks.

As you can see, there is a fair amount of twist present in the assembly.

The get the twist out, i basically set the assembly on the bench spar side down and clamped one end of the spar to the table. The other end of the spar was clamped to a long board for leverage, and i applied a gentle twisting moment to the parts. 

One end clamped to the bench - the blocking is to get the spar up off the bench becuase the spar is still held to the ribs with #30 clecos.

The other end is clamped to a long board to provide some twisting moment. 

I gently applied some twist to the whole shebang. 

This was what it looked like after the twist - a bit better i think. 

The pull rivets were then installed which attach the spar to the rib flanges. I did one rivet on each rib, then re-checked for twist. This is how i came out once the ribs were riveted on. Happy i took the time to correct for this - i don't think it would have been corrected just by riveting on the top skins, and would have been much harder to twist out once the skins were on. I will re-check regularly of course as i continue riveting. 

The whole process was repeated for the right assembly which came out nicely once the spar was riveted to the ribs:

I had a home schooler in the shop today 'helping out'

Riveting on the top skins

Putting the top skin in place wasn't too bad if you take your time and put the inboard end of the skin in place first - this has a tiny doubler where the large screw gets installed later, and with this in place you need to sort of slide the skin outboard to get it to fit. I initially tried to install it with the outboard end first and it was impossible. Once it was in place it got clecod at every second hole, and i used the trailing edge alignment tube to brace the trailing edge of the skin straight throughout the riveting process. These were done with the mushroom set on the outside of the skin and my small tungsten bar on the inside, in various orientations to avoid the stiffeners. I used about 30psi. The plans called for -3.5 length rivets for these but i felt they were too short, so i used -4.

Riveting the end ribs to the spar - using big bertha.

To get the AD4-4 and AD4-6 rivets installed, i placed the aileron upside down on the table. To reach into the space between the rib doublers etc, I purchased a new tool - a long 12" cupped set. This thing used about 60psi to work nicely. It fit fine on the inboard end of the assembly, but to get the outboard end i had to grind the side off the tool - don't you love having to modify a tool you've had for 5 minutes!! 

It fit fine here on the inboard end. 

But bumped into a doubler on the outboard end. 

Nothing some grinding can't fix. 

The only SNAFU was that i set the first rivet, then thought it needed another hit, but the tool had slipped off a little. oops. Smiley time. The rivet drilled out fine using a #31 to snap off the head, then a #40 bit down the centre, and punching it out. 

SMILE!

I am definitely getting a lot better at drilling rivets out - here i drilled right down the shank and made a little tube. This gives the rivet something to collapse into when you punch it out. If you don't drill down like this, it is very hard to get a long rivet out. I also use a 3/32" pin punch so the hammer force is on the end of the tube - almost like pulling the rivet out. I find this helps to prevent the rib flange bending. I also waitied to drill this out until all the others were set. Punching it out with only clecos holding the flange down would end in disaster.

That comples the top skins - next up is to countersink the trailing edges, and install the bottom skins.