ELEVATOR TRIM TAB 

The elevator trim tab is basically a simple piece to build.  As with all of the other parts in this kit, the holes are pre-punched.

Trim tab bending block Trim tab bending with mallet

The first thing to do on the trim tab is to bend the end ribs.  I made a block from a piece of hard wood for this task (LH photo).  I was skeptical about this bending procedure until I actually tried it.  The plans called for using a rivet gun with a flush set, but I decided to try it with a mallet instead (above right).  I am satisfied with the results. 

 
Trim tab inboard end  

The inboard end gets riveted after the trailing edge is formed.  In the  photo above the rivet holes can be seen.  After I squeezed the trailing edge I transferred these holes to the opposite "rib."  I then dimpled the holes for installation of countersunk blind fasteners. 

Extra hole due to improper dimple attempt The repair

The next process is to dimple the spar attach holes.  Care must be taken to not go too fast.  These two photos above show the first of the two errors I made (one on the trim tab and one on the LH elevator) by trying to go too fast.  I squeezed the trigger on the pneumatic rivet squeeze that I was using to dimple the trim tab before I the dimple pilot was in the rivet hole and I made a hole beside the rivet hole.  (If you are wondering what the circle around the outside of the damaged rivet hole is, it is a reflection of the camera lens.)  There were no cracks so I decided to make a simple repair to cover the damage for cosmetic reasons.  The photo at the right shows the repair after installation.  I thought about filling the hole with some Marine-tex epoxy putty but I decided to cover it instead.  The little strap will add a little strength but not much.  As you can see from these photos and the ones that follow, I accomplished a lot in one day. 

Trim tab parts after prime Trim tab clamped to keep it straight

The building of the trim tab is straight forward for the most part.  I etched, alodined and primed the parts (Upper left photo).  I then formed the trailing edge by squeezing.  See the rudder assembly photos for this procedure.  The parts were then all attached to each other per the plans with clecos.  The entire assembly was clamped to the work bench beneath a straight block of wood to keep it straight.   The plans called for counter-sinking the hinge attach holes in the hinge and dimpling the same holes in the trim tab skin.  I decided to dimple the holes in the hinge instead.  It worked out OK.  There was some distortion because the hinge material is so soft.  Straightening was easy enough though.  I did not save any time so countersinking (Like the plans call out!!!) would have been more than efficient.

 
Another view of the clamping and squeezing technique  

In the photo above, you can see that the block of wood was holding a decent amount of pressure on the tab to keep it straight during assembly.  I got so engrossed in the assembly that I didn't take any other photos of the process.

Bottom view of completed tab Top view of completed tab

These two photos show the completed trim tab.  Except for my little patch I was relatively satisfied with the way it turned out.

ELEVATOR TRIM TAB UPDATE

On February 22, 2003, after a period of 7 months of inactivity on the elevator trim tab, I decided to re-evaluate the repair strap that I put on the trim tab.  The damage was actually minimal and the worst that could happen is that a crack “might” develop from vibration some day.  If this happens, I feel confident that it would be caught on an inspection.  I removed the strap and re-installed the blind fasteners.

Repair removed. Added fastener in formed rib.

While I was working on the trim tab, I decided that the small rib formed by bending the elevator top and bottom skins at the outboard end of the trim tab needed a little more work.  The plans call out to bend the skins to form this rib but no fastener is called out.  I decided that a fastener was needed and I drilled a hole, dimpled the same with the “Pop” rivet gun dimple die and installed a CR3214-4-2 Cherry-Max fastener in the hole.  I checked the trim tab for fit one more time and I had a little more clearance.  It was rubbing the elevator before.

 

Final fit check of trim tab.