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!