A little Elevator Work

We flew up to St. Louis to visit friends and family for the Memorial Day weekend. So, of course, nothing to report there. Except that every cross country trip reiterates the reasons for this airplane: it's speed, comfort, the advanced avionics, and it will do it all a lot cheaper than renting. This last flight back could have been cut by almost an hour! Can't wait.

The plans call out for solid rivets to attach the elevator skins to the small aft spar. This is fine where it's cut out for the trim tab, but where the skin extends beyond spar...not so much. Access to the area is really difficult especially when the upper and lower skins come together. The plans tell you to make a special bucking bar to reach inside the skins or just install with blind rivets on this one side. Well, I decided, after looking at the strength values of the rivets, to just install both sides with the blind rivets. Primarily so both sides look the same and it will be a lot easier. Plus there is no risk of damaging the thin skins.

With that I proceeded to install the MK-319-BS blind rivets and discovered they are slightly oversized. The #40 holes are a little too small. What I really needed was a #33 hole, but after scouring town this drill bit is nowhere to be found. So I settled for a 3mm drill bit...pretty close. Tried it on a piece of scrap and it's perfect. I opened up the holes in the elevators and popped the blind rivets in. They work great and it was real easy. (0.5)

Elevator Ribs

I finished back riveting the ribs to the elevator skins. I love back riveting it's quick, easy, and the parts come out looking great. I then riveted the aft spar on. All in all, a quick yet productive evening. (2.0)

Elevator Work

The doublers that install around the trim cable cutouts stiffen the elevator skins and have several nutplates installed. The nutplates rivet holes need to be dimpled. So I had to modify one of my dimple dies by grinding down one of its edges to clear the back side of the nutplates. It worked well and the doublers came out great. I then began backriveting the ribs to the skins, but I'll have to finish that maybe tomorrow. (2.0)

Elevator and Trim Work

This past weekend I worked on the elevators and trim tabs. The trim tabs have a lot of detail work to them for such a little part. You have to bend the edge tabs in and finish bending the skins themselves among a few other things. Both the elevators and trim tabs have foam ribs in them to stiffen the skins. The skins need to be scuffed and masked before they are primed in the areas the ribs will go. So I finished the trim tabs, scuffed the skins, and primed the last parts. After a few minutes in the warm sun the parts were dry and I started final assembly of the elevators. Fri (1.0) Sat (3.0) Sun (6.5)

Trim Tab Hinge Pin Solution

I was reading ahead in the plans and found that they secure the trim tab hinge pin to the spar using safety wire. This is probably ok, but I feel it would need a close inspection before every flight to ensure that the safety wire isn't corroding away or wearing through. I've seen safety wire wear through on a Cessna 172 door and would hate for this to meet the same demise. I wanted to come up with something a little more permanent. So I went to the Van's Airforce website which is a forum for RV builders to discuss....well almost everything airplane. With a quick search I came across a solution that I like...reposted below.

This will be my plan, simple.

 

"I struggled with finding a way to secure the hinge pin on the elevator trim tab until I saw this technique used on some RVs that I looked at up at Air Venture.

As supplied in the kit, the hinge is longer than what's needed. When you trim the hinge to length, be sure to NOT cut the hinge pin. Leave it long and extending past the end of the elevator as shown above. Now bend the hinge pin so that it will lay across the web of the spar.

Take a spare piece of hinge and cut out one eye. Drill a hole in it for a #6 screw. Slip it over the hinge pin and locate the position of the screw hole in the web of the spar. Remove everything and attach a #6 nut plate behind the hole. The nut plate will fit on the forward side of the elevator trim spar web where it extends past the edge of the inside elevator rib. When you're done, you'll find that you will be able to get a long bladed screwdriver on the screw even with the trim tab mounted and in-place.  "

Trim Tab Jigs

The trim tab mounts to, and is part of, the elevators; so I still consider this elevator work. It's notable though, how many jigs and fixtures need to be made to make, or finish making, the pieces for such a small part. I made a jig last night to make the trim tab clamps and I continued this jig fashion into tonight to cut out the foam ribs that go inside the trim tab. I wanted to ensure a good perpendicular cut, so, enter the jig. Also you need to make a homemade brake to finish bending the skins from some 2x8's and hinges. It should work well for what I need. So hopefully I can get back to airplane parts instead of building things to build things! (1.5)

Back to Elavators

Didn't get much done today. I cut out some support clamps to help make the trim tabs. I made a make shift jig to help in making them all the same when cutting them out on the table saw. (1.0)