Trim Tab Hinge Pin

Time: 1 Hour

The last month or so has been slow in the hangar as I have been working a lot at United as well as working projects on the new house. I have been keeping a “punch” list of tasks that needs to be done for projects over the last couple of years. These items didn’t need to be done at that time and it was better for them to remain undone to make the remaining projects easier. One of those items was the trim tab hinge pin. I had originally put a temporary pin in that was shorter and without any bends in it to make it easy to remove the tab as I built the tail. Today I moved on to bend and create a permanent pin and a way to secure it. Van’s would have you just put a bend and safety wire it to a small hole in the small spare of the elevator. I wanted to do something a little nicer. I wanted to use a piece of hinge with its eyelet and create a tab to put a screw through. I made some measurements and came up with a plan. I would drill out the two rivers on that spare and put a #8 nutplate there utilizing the bottom river hole. I would drill another rivet hole for the second rivet in the nutplate and enlarge the top original rivet hole for the screw. I made some test bends in a scrap pin and came up with the perfect setup. I then reproduced the shape on a new pin. I then shaped a piece of hinge so that it had one eyelet and drilled a #19 hole in it for the screw. I dimpled the bottom hole in the nutplate and countersunk the spar for the top rivet. I did it this way since the single sided nutplate is pretty tight to try to dimple both holes. Once I had both rivet holes finished and the hole for the screw done and cleaned up I riveted the nutplate in place. I then cleaned up the shape of the hinge tab and bent the tip of the pin so that the tab could not fall off. I put the parts back together and slid the pin in place securing it with a #8 screw. Turned out really nice and clean. It’s little details like this that make the build fun, most people will never see this but it makes me happy knowing I spent the extra time to make it clean and functional.

Elevator Trim

Time: 2 Hours

I have had the elevator electric trim motor since I bought the tail kit so that I could work the mount it needed into the right elevator. During the time I was installing most of the wiring I ran the necessary wires, shielded 5 wire, to the horizontal stabilizer. I just had it bundled up where it exited the horizontals rear spar. I decided to get that wiring finished up since I will be installing that elevator soon. I’m using the Deans micro connectors commonly used in the remote control toy world. These need to be soldered to make the wire connections and are perfect for these small wires. I planned on running the wire from the stabilizer through a snap bushing that is in the elevator with enough to hang out the opening where the trim motor gets screwed in. That way I could mount the elevator and have the wires/connectors easily accessible so I could make the connections before mounting the motor. The extra slack in the wires can be easily tucked to the side of the motor as it’s is mounted. After a quick test the the motor functioned correctly I completed the wire connections with shrink tube to protect the joints. I installed the motor into the elevator and temporally installed the elevator. Dynon has a setup and calibration for the trim to identify the full travel of the motor in both directions. Once that’s done you are good to go minus identifying the trim location for takeoff. That will come later during flight testing. Once that’s done I will set that position in the Dynon setup and a green line will show on the trim indication so you can easily set takeoff trim. Here is a video of the trim as I move it through it’s full up and down travel. https://www.rv8-hangar.com/wp-content/uploads/2018/12/img_2504.trim-1.mov

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.

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20130629-220829.jpgI 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.

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20130629-221327.jpgI then flipped the elevator over at set up for the opposite skin.

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20130629-221623.jpgBy 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.

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20130629-221739.jpgI then I matched drilled the holes and pop riveted as per the plans.

20130629-222017.jpgI repeated the process with the right elevator.

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20130629-222133.jpgI then placed the electric trim in the left elevator and hooked the linkage to keep the trim tab from flipping around.

20130629-222939.jpgWith 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.

20130629-223016.jpgYou 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.

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20130629-223150.jpgBig 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.

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20130627-173232.jpgOnce 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.

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20130627-173519.jpgThen I marked the inboard edge of the tab side hinge to make it the shape match that of the skin and spar.

20130627-173828.jpgOnce 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.

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20130627-175015.jpgWith 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.

20130627-175120.jpgThe 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.

20130627-180028.jpgThe gap is now perfect and even. I rechecked the trailing edge alignment with a straight edge and it matches perfectly.

20130627-180201.jpgA 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.

20130627-181036.jpgNow 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.

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20130627-181830.jpgI 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.

20130627-182403.jpgRiveting 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.

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20130628-151921.jpgNext up, rolling the leading edges of the left and right elevators.

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! πŸ™‚