Completed rudder and elevator leading edges

I've been working on finishing the last items on the empennage over the last few days.  My wing kit arrived a few days ago, and I'm anxious to start working on the forward spar.  The leading edges on the elevators and rudder needed to be closed up, and I have a small amount of work on the left elevator where the trim tab motor sits, and that's it for the tail section!  

Getting the leading edges of the elevators and the rudder to come together nicely takes a bit of work.  It's easy to roll the leading edges, but it's challenging to get the outer skin to sit flush without any gaps after the blind rivets have been set.  To resolve this, I ended up slightly over bending the outer skin, which allows the two skins to sit flush next to one another.   Bending one section at a time, outboard to inboard, makes the process easier.

Several builders have written that they used a pipe wrench to grip the dowel (3/4 inch) that is used to roll the leading edge.  I found that a steel handle, such as that used for a bending brake, worked much better when inserted into a hole drilled through the dowel.  The wrench was hitting the forward spar of the elevator, limiting the amount the leading edge could be rolled.  Using the steel handle at the inboard end of the elevator by the control horn eliminated this issue.  

After I had the skins rolled, I taped them in place with strips of duct tape and match drilled the holes.  I didn't find it necessary to use the ultra sticky duct tape that some builders use - the standard duct tape worked great, and didn't take the primer or blue vinyl off where I didn't want it removed.  The tape was then removed, the holes deburred (with a scotchbrite pad on the interior surface), and the blind rivets were set.  I wasn't happy with one of the elevators after it was finished, so I drilled out the rivets, slightly adjusted the leading edges by bending the skin a bit more, and re-riveted.  I was very pleased with the results.

Two sections rolled on right elevator

Right elevator leading edge finished

Left elevator leading edge clecoed - ready to be match drilled

Two sections on rudder complete - one to go

Rudder leading edge finished

The completed airplane parts are getting larger!

Trim Tab

Many people make the trim tab several times until they are satisfied with it, so as on the trim tab opening on the left elevator, I practiced making my bends on some scrap aluminum before I made the those on the trim tab itself.  This procedure worked well for me, and I'm happy with how the trim tab turned out.

Prior to making the first bend, I sandwiched the skin between some angled pieces of oak and clamped them to my workbench.  I used double sided tape on the skin to prevent the oak wedge from slipping while the bending was taking place.  I made the initial bend with another piece of wood, which I used to push the skin down toward the forming blocks.  After that was finished, I used my rivet gun with low pressure (approx. 10 psi) with a flush set to complete the bend.  Prior to bending, I made a radius on the oak wedge upper edge, which allows the skin to from a nice radius rather than a sharp angle.  My initial practice pieces had very sharp angles that would eventually crack.  With the bottom side finished, the assembly was turned over, re-clamped to the table, and the process repeated.  The same procedure was then used for the inboard edge.

With all the bends complete, the hinge was drilled and attached to the trim tab and later to the elevator.  The trim tab motor and cover plate were assembled, and the control horn was riveted to the trim tab.   A few of the rivets for the control horn near the trailing edge are a bit difficult to reach, so I riveted the control horn prior to setting the rivets in the trim tab edges.  This allows the trim tab to be opened, which makes it easier to access the more challenging rivets for the control horn.  With that step complete, the remaining rivets were set.

First bend is made around angled oak blocks

Inboard edge bends completed

Control horn riveted to trim tab skin

Hinge riveted to leading edge of trim tab and fit to elevator

Rivets set attaching hinge to elevator

Trim tab motor assembly work

Motor assembly completed

Left elevator (cont.)

With the stiffeners in place and the skeleton riveted together, it was time to bend the trailing edge.  This process is much easier the second time, as you're not as concerned about messing it up.  I made the bend with my wood bending brake, and the skin rests nicely on the skeleton with no clecos installed.  With the trailing edge finished, I was able to bend the tabs on the elevator for the trim tab opening.  After a little practice, I placed a wedge inside the skin with another wedge on top of the skin, clamped the whole assembly to the workbench, and made the first bend of the lower tab.  Then the top tab was bent, and the remaining rivets were squeezed. 

After trailing edge is bent, the skin rests on the front spar

Practice bend on piece of scrap aluminum

First tab bend (bottom) on elevator

Top and bottom bends finished - ready for rivets

Ready to squeeze perimeter rivets

Squeezing outboard rivets

Counterbalance weight attached

Left elevator main structure complete

Left and right elevators side by side for the first time - very cool !

Left elevator

The left elevator construction is virtually identical to the right elevator, with the exception of the trim tab.  While this seems like a small difference, I found that it took quite a bit more time than the right side, although I was very pleased with the results.  I started by deburring all of the skeleton parts and the skin, and removing the vinyl from the rivet lines on the skin.  There is a reinforcement plate that fits where the trim tab servo mounts that requires platenuts, to which the trim tab cover will attach.

Many people rebuild the trim tab several times, so I took that as a sign that practice was in order.  Bending the tabs on the inboard and outboard ends of the trim tab, as well as those on the trim tab opening of the elevator, are some of the more challenging tasks of the empennage construction.  I traced the trim tabs onto some scrap aluminum, cut them out, and clamped them to the wood blocks I fabricated for this task.  I learned how the aluminum responds to various bending techniques, including a low pressure rivet gun, and what I would need to do on the real tabs to make them turn out well.  My practice pieces got progressively better, and after the third one I made the bends on the real parts.  I think it turned out very well.

 

Deburring left elevator parts

Removed vinyl from left elevator skin

Ready for initial assembly

Skeleton coming together

Fitting trim access reinforcement plate

Platenuts installed on reinforcement plate

Skin match drilled to skeleton

Stiffeners match drilled to skin

Riveting skeleton together

Stiffeners riveted to skin