Empannage Done!

Time: 6 Hours

Today I had one goal, to finish the elevators and essentially finishing the empannage. All that remained was to roll the leading edges of the left and right elevators. So I started by setting up the pipe rolling jig that I used for the rudder. I decided, based on the results from the rudder, to go up to a 1″ diameter conduit from the 3/4″ I used for the rudder.

I also decided to try a different approach at where I taped the pipe to the skin. On the rudder I taped the pipe right along the edge of the skin. When the bend was done I had a small gap between the skin at the top of the rudder getting wider as you got to the bottom. On the first elevator I taped the pipe at the outboard even with the skin. I then took a measurement from the spar to the pipe. I matched this measurement at the inboard section. This angled the pipe in a little at the inboard section compared to the outboard. I then rolled the skin giving me a really nice roll.

I then flipped the elevator over at set up for the opposite skin.

By taping the pipe at a equal distance on the entire length of the skin the gap that resulted was pretty much equal for the entire length. I had to massage the skin a little in the middle section to get it to lay perfectly flat.

I then I matched drilled the holes and pop riveted as per the plans.

I repeated the process with the right elevator.

I then placed the electric trim in the left elevator and hooked the linkage to keep the trim tab from flipping around.

With those leading edges done the major building points of the empannage are done. The only pieces left are the fiberglass tips which are really finishing parts.

You can wait to do these parts when you finish the aircraft or any point I between. I think that I will start the elevators and the top of the rudder. The bottom will have a light in the tail section and I will work on that later in the build. So now I have around six weeks before the wings get here to study up on fiberglass and the techniques. So I cleaned up elevators and brought them into the house for safe keeping and to be on display.

Big accomplishment for me! Next up learning to fiberglass.

Trim Tab

Time: 5 Hours

The task for yesterday was to finish up the trim tab. The first order of business was to figure the exact placement of the hinge on both the tab and the elevator. The plans give you the measurement on the outboard edge of the trim tab side, 3/8″ outward from the last hole on the skin/spar. So I lined up the edge to see how the barrels of the hinge lined up.

Once I established the length and placement of the hinge I drew a line 3/16″ from the straight edge of the hinge. This was the center point of the flange of the hinge and a marking point for match drilling.

Then I marked the inboard edge of the tab side hinge to make it the shape match that of the skin and spar.

Once I had the shape right I clekoed the hinge to the tab and matched it up to the elevator. I had two goals: keep the inboard edge of the tab in alignment with the elevator and keep the trailing edge of the tab in alignment with the trailing edge of the elevator. According to Van’s they are both important but the trailing edge is the most. Once I had both of those goals lined up I drilled the two end holes of the elevator side hinge.

With the two edges in perfect alignment the outboard edge was not, this was due to the cut I made being out if square with the leading edge of the tab.

The plans call for a minimum gap between the outboard edge of the trim tab and the inboard edge of the elevator of 3/32″. The forward edge of the tab had a gap of 7/64″ so I measured the same at the trailing edge of the trim tab. I then removed the trim tab from the hinge and checked the line I just made and it ended up perfectly square with the leading edge of the tab. So I took the tab to my Scotch-Bright wheel and worked the edge to the line on the top and bottom of the tab.

The gap is now perfect and even. I rechecked the trailing edge alignment with a straight edge and it matches perfectly.

A couple of nights I wrote about the hole that I figure 8’d on one of the riblets. After a good night sleep I decided that a small doubler would be a better solution for this problem. This would sandwich the bad hole between two good pieces of metal. It just worked out that there where two holes, one forward and one aft of the bad hole. I measured the length giving me good edge distance and the width. I then cut the doubler from some scrap sheet that Van’s supplied with the empannage. I matched drilled it to all three holes and all looks good.

Now that those tasks are done I could now disassemble the tab to take care of the edges, dimple and scuff all the parts. The dimples in the riblets were a lot of fun but made easier by using the pop rivet dimple dies. The top edge of the tab spar needs to be countersunk rather than dimpled like the matching spar in the elevator. This is so that the hinge could sit flat on the spar which it couldn’t do if the spar was dimpled. I rolled up the carpet on the work bench and used the matched drilled holes and countersunk the flange.

I then cleaned all the parts for priming and started that process. While the parts where drying I riveted the elevator side hinge. This was a little difficult to get to the shop head but I had several different size flush heads for the squeezer that worked.

Riveting the tab was pretty easy, I just had to do a little thinking at the sequence of rivets as my tab was a little different from the plans. The inboard edge I had the skin, riblet, the two trim horns and the doubler to deal with. Some of the rivets for the horns were inside of the riblet and some were on the outside of it. So a little planning was in order. Once I had the plan it went pretty quick. I then lined up the hinge and inserted the pin. All the edges looked great and the motion was perfect.

Next up, rolling the leading edges of the left and right elevators.

Left Elevator & Trim Tab

Time: 6 Hours

After taking care of some work realated business I was able to get into the hangar after lunch. To start was to rivet the substructure of the left elevator. This job went pretty smooth with the help of the pneumatic squeezer. I did have one rivet get damaged due to the die in the squeezer slipping off the head as I pulled the trigger. So out came the drill and I replaced it without too much trouble.

Once you have the substructure all riveted together its time to slip it into the skin. Before you can do that you need to add a “gum wad size” of RTV silicon at the ends of the stiffeners. This helps with vibration cracks in the future.
You rivet the entire skin except the top flange of the trim tab spar, as you have to wait until you are ready to rivet the hinge with it. So I added some blue tape to remind me to not rivet these holes.I riveted every other hole then removed the cleko’s and finshed the rest.The four outboard most rivets on the trim spar call for MK-319-BS blind rivets, but I was able to get the first two with my 4″ no-hole yoke in the pneumatic squeezer. So just the last two are bling rivets on the top and bottom.
After I finished riveting the skin I did a once over to check all my work and found that the last rivet on the inboard bottom had swelled between the skin and rib. This is due to the flange and skin not being tight together and allowing the rivet to swell in between as well as under the flange. So I drilled it out and figured it was due to me not being able to get a good squeeze on it. So I admitted defeat and used a blind rive as it will never be seen once painted.All finished except for the trim tab.Next up was to bend the trailing edge of the trim tab. So I brought out the wood brake that I built. It took just a few pushes on the brake and the bend was complete.As I discussed before my plan was to avoid the bending of the ends of the trim tab. I bought a couple extra ribs to cut up and make riblets for each end of the trim tab. I decided to take on the longer side first as it would have to be cut on an angle.I had to cut a relief into the top of the riblet to be able to sit inside of the tab spar.Next up was the smaller side which had a straight cut and the same relief detail.Once I was satisfied with the fit and how they turned out I broke out the dremal and cutting wheel.Here is the fit after the trim tab ears were trimmed off and the riblets were touched up. I matched drilled both ends and found only one error on my part. The bottom of the trim tab has two horns that are riveted to the tab and make for an attach point for the electric trim. One hole was off by 1/16″ causing a figure eight shape. So I will treat that hole as a normal hole and add another rivet next to it. This piece only has 2 rivets in it normally so I will have a little extra with three.

Next up will be to tackle the trim tab hinge. This is a little bit of a bear to make sure everything lines up and you maintain good gaps. I was in the hangar for 6 hours and figured I was a little tired and this was a good place to call it a night.

More Left Elevator

Time: 1 Hour

Got home last night from another fun day of dodging and weaving around thunderstorms. Was feeling a little tired but wanted to get a little time in the hangar. First task was to countersink the top flange of the trim tab after my mistake if dimpling it. Then I wanted to get all of the understructure primed so that I could get some riveting done today. No pictures of last nights work since you have seen a ton of parts being primed! 🙂