Thursday, December 3, 2015

Section: 21
Hours: 8

The first task today was assembling the flap hinge braces. Each pair of braces is double flush riveted. I initially tried back riveting, but I ran into problems because it was hard to position the hinge brace on the back rivet plate without marring the joggle bend. I switched to using the squeezer and the results were much better.

I assembled the spars and ribs for the left and right flaps. I initially thought riveting today would be an easy job- it looked like all the rivets could be squeezed. I started out by clecoing all the parts together to make sure I had everything in the right place for both flaps. I had to pay special attention to the aft ribs- they can easily be inserted upside down since they are nearly symmetrical.

The manual advises you leave off the end rib to facilitate using the squeezer. I discovered there were more interferences for the squeezer than just the end rib. After puzzling over assembly order, I settled on squeezing the nose ribs on first. I removed several of the aft ribs so I could easily reach the nose ribs. Since the ribs are thinner than the spar, I placed the manufactured heads on the rib side. I used a standard yoke on the squeezer and was able to reach all the rivets for all the nose ribs.

Then I riveted the aft ribs. I again placed the manufactured heads on the rib side which meant I had to switch to my 2.5" flange nose yoke for the squeezer to reach around the spar flange. I wasn't able to squeeze the two inboard ribs or the last outboard rib.
Two inboard aft ribs (clecoed ribs in pic) couldn't be squeezed.

Outboard end rib couldn't be squeezed.

Because of the way the rib flanges overhang, I had to use the bent stick set in the rivet gun to reach the rivets for the problem ribs. I bumped the air pressure up to 60 psi and used the tungsten bucking bar with good results. I didn't have to drill out any rivets today. Whoo-hoo!!!
I clamped a couple blocks to support the spar during riveting.

Here's a couple more shots showing orientation of rivet heads.

Next I stripped the blue plastic from the rivet lines of the nose, top and bottom skins. Then I slipped the nose skin on the flap frame and clecoed it. I finished up for the day by clecoing the top skin onto the frame to prepare for riveting tomorrow. I checked for twist in the D box - the digital inclinometer is showing less than 1/10 a degree difference between the inboard and outboard flap brackets- so far so good!

Woody says it's quitting time! Time for dinner!

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