Installed nutplates for flap hinge pins

November 21, 2011 – I have finally installed the nutplates that will secure the flap hinge pins. I got the right one done several days ago, but as soon as I installed the second rivet, I realized that I had installed the nutplate upside down. The big issue was that I had countersunk the rivet holes in the flap brace.  STUPID!!! So after I calmed down and regrouped, I made a doubler and installed it. The countersinks are now on the correct side and the nutplate is installed.

Time: 2:00

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Flap hinges drilled and hinge pins bent

November 15, 2011 – Once I got the wing-side flap hinges in place with Carlos’ help last week, I continued to drill the hinges.

Because I had inadvertently dimpled the flap braces (where the flaps attach to the wing) I had decided to countersink the hinges to clear the dimples, then install a strap to add strength. The straps would also help make up for less-than-ideal edge distance on the hing half.

Hree’s the countersinking in progress. You can also see how close the edge distance is from the holes to the edge of the hinge.

Once the hinges were countersunk, I clecoed them back in place and drilled the straps. I think this will work out fine, and will provide additional strength.

After the hinges were drilled, I started making the hinge pins. I chose to go with the option of having two pins per flap, each fed from the center of the flap. I temporarily placed the flap in place, and marked where the hinge cutout was so I knew where to bend the pins.

I bent a 90-degree angle in the pins, then went approximately .7″ from that 90-degree bend and bent a 45-degree angle in the correct direction. I made sure the pin was in the correct position and had pin to spare on either end. Here’s the first pin bent and in place:

…and the second:

I cut pieces of leftover hinge, which will be secured to the flap brace with a screw and nutplate. This will lock the pins in place.

Time: 3:55

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Started drilling flap hinges to wing

November 7, 2011 – Over the last week or so I set up to drill the flap hinges to the flap brace on the wing trailing edge.

I decided to cleco the bottom wing skins into place. I’m REALLY glad I did because I found out that the flap braces are not necessarily in the correct position to align the flaps with the ailerons when attached, as seen below:

If I had clamped the flap to the brace, then adjusted to the aileron, it would have been way off.

My next problem was how to hold the skin and the brace together so I could also clamp the hinge in place to correctly drill it. I had read about how other people used rivets to temporarily hold everything together, but it seemed that some of those people went overboard on the size of rivets they used for this. I picked four spots along the brace where it seemed that a cleco did the most good keeping everything tight and aligned, and I laid out rivets at those locations. I’m just using the same -3 rivets that will be used to rivet everything together at the end. I countersunk the skin and used a short rivet to hold the flap brace in place.

When I rivet the hinge in place, I’ll just shoot these like all the others. I don’t believe the countersinks in the skin will pose a problem, because those are surrounded by regular dimpled holes, and I’ll also be putting a strap on the backside. More on that later.

A friend of mine from work, Carlos, came over to see the project and to give me a hand with the alignment of the flaps for drilling. I tried to handle it by myself, but the fine adjustments were a pain, and I was afraid I’d drop a flap.

I had drawn the line along the hinge at 1/4″ as a guide for edge distance. With the trailing edges aligned, we were on the low (edge) side of that line. A little less edge distance than I would like, but again, I’m going to put a strap behind everything, so I’d have extra structural support. We placed a small c-clamp at each end and did the adjustments as needed.

The plans call for a 1/4″ gap between the flap and the aileron; other people have gone with 3/16″. I decided to split the difference and got a nice 7/32″ gap.

The trailing edges in that picture don’t appear aligned because the flap is not held in trail with the aileron.

When we were happy with the positioning, I drilled a couple of holes on each end, just to hold it all in place. Here’s the outboard and the inboard clamp setup:

I removed a flap to expose the hinge and make it easier to drill the rest of the holes.

Thanks Carlos!

Time: 4:40

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Flaps finished! (kinda)

October 22, 2011 – The flaps themselves are complete. All that’s left on them is to drill the wing half of the hinges to mount the flaps. That will come after the ailerons are fitted and rigged.

I located roughly the halfway point for the hinges where I cut out the eyelets to allow for the two-hinge pin method of securing the flaps. The hinges are 56″ long, so I measured and marked at 28″

I removed that one eye in the flap-side hinge, and the two surrounding it on the wing-side half of the hinge. Then I marked where that would fall on the flap brace mounted on the wing.

Hopefully, the hinge cutouts and the flap brace will be situated so I can secure the pins cleanly. If not, I’ll just run a plate across a lightening hole in the brace.

I primed the flat surfaces of the hinges, especially because I wanted the mating surface to be primed.

Then I riveted the hinges to the flaps. No big deal; I was able to use the squeezer on all of them.

I set the flaps up in the wing trailing edges just for storage.

Time: 1:30

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Flaps assembled

October 18, 2011 – I have finished with the assembly of both flaps, except for installing the hinges.

I riveted the upper skins to the ribs, then I installed the inboard and outboard end ribs. With the “aft spar” as part of the lower skins, you don’t have access to put in solid rivets at the trailing edges, so you have to install blind fasteners.

The nutplate for the flap control rod also made things a little interesting as far as installing that skin rivet right there, but with a little patience, it can get done.

You also have to remember to install the shims where the upper and lower skins overlap.

That got me down to the aft two fasteners in the outboard ribs, where you can’t fit a bucking bar. I used my normal indirect back-riveting method here.

I’m ready now to attach the hinges, after I cut the slots for the hinge pin installation.

Time: 4:55

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Began assembly of flaps

October 7, 2011 – Not a bad way to start a long weekend. I started riveting on the flaps.

I began by installing the doublers for the flap control rods on the inboard ribs. I also installed the nutplate for the rod end. The plans call for a flush rivet for the side that does not go through the doubler. I didn’t see the sense in removing material there, so I just used a regular rivet.

I also installed the corresponding angles onto the inboard ends of the spars.

I then placed the ribs (except for the end ribs) in place on the lower skins. I installed the rivets in the aft ends of the ribs attaching them to the faux spar of the lower skin. On the first flap I installed the rivets from the aft end. Didn’t really like the result, so on the next flap I installed the rivets from the rib side. Much better result. I used a squeezer in both cases.

I then riveted the ribs to the lower skin.

Once both lower skins were done, I started on the right flap by sliding the lower skin into place in the upper skin, then I riveted the two skins together along the row on the bottom where they overlap. The first picture below shows the two skins “exploded” to show their relative positions. The second picture shows them nested in place.

Here’s a shot of the rivets from the inside:

After that row of rivets was done, I clecoed the upper skin to the ribs. I’m ready to do those rivets next.

Time: 2:05

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Flap drilling continued

September 19, 2011 – Now that the main structure of the flaps (ribs, skins and hinges) are drilled, it’s time to move on to other parts of the flaps. The spar where the hinge attaches gets countersunk. I removed the bottom skins and left the hinges in place to add as a guide for the pilot of the countersink.

I’m debating whether I want to countersink the top side of the spar. The plans call for dimpling, but I think the spar is too thick for that. I’ll have to do a little more research on that, plus I, like many other people before me, dimpled the flap brace that’s attached to the wing. It is NOT supposed to be, so I may add a doubler to that when I attach the hinge to the wing. That comes later on, though.

There is an angle and a bent doubler attached to the inboard rib of each flap. This is where the flap control rod attaches. I cut the angles to size and laid out the fastener pattern per the plans.

When I had one drilled to #40 holes, I clamped the two together, since they are identical left and right, and drilled the other one.

I clamped the angle in place on the spar, using a drawn center line as a guide, piloted the holes in the spar to #40, then took the holes up to the required #30 (1/8″).

I bent the control rod doublers to the approximate 6.3 degrees that Van’s calls for, then clamped it in place and back-drilled to the rib and the angle.

The aft-most hole in the apex of the doubler aligns with a hole in the rib. That hole gets taken up to 1/4″. This is where the control rod rod end attaches. I used 2 core drills to take the hole up from 1/8″ to 1/4″. I prefer core drills and reamers for larger holes because they make a much cleaner hole than a regular drill bit.

After all this was done, I took everything apart for dimpling and prepping for paint. Part of this process is the usual labeling of parts using wire and aluminum tape, and removing the blue film from the rivet holes on the skins.

Time: 5:20

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Started flaps

September 12, 2011 – I started the flaps by sorting and clecoing the ribs to the spars. It was a little mind-bending putting the left- and right-handed ribs in the correct locations.

The bottom skins for the flaps are interesting in that they have the aft spar bent into them. The short inner ribs get riveted to that “spar”. The instructions allow for spacers to be installed as required. I don’t think any of mine require spacers at this location except for one. This is what the typical gap looks like for me:

The flaps hinge at the lower skin, and the hinge must be drilled at this point. I started by drawing a line along the length of the hinges on both sides at 1/4″. This will ensure that the hinge is straight and that I will have good edge distance for the rivets.

With these lines drawn, I clamped the hinge in place, and made sure I could see the line through the lower skin rivet holes.

I drilled all of the holes in the hinges.

After the hinges and the bottom skins were all drilled, I slid the top skins in place and clecoed them.

The top skins require shims at the trailing edges of the inboard and outboard ribs. I made these per the plans. They are 1 7/8″ by 5/8″. You drill a rivet hole in a specified position, then put the shim where it belongs to drill the other holes. I drew a center line from the first placement hole so I would know the hinge was in the perfect spot.

When I put the shims in place, and clecoed them, I could see the center line that I’d drawn. I knew I could drill the second hole.

I then drilled all the remaining holes for the top skin.

This is the left flap. I still need to drill the top skin for the right.

Time: 3:10

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