Month: November 2019

Tonight I match drilled the aft portion of the elevator trim tab hinge, then match drilled the left elevator tip rib assembly, and trimmed the left elevator trailing edge wedge.

This is part way through the match drilling of the aft half of the trim tab hinge. I used a lot of clamps and measured to check that the hinge stayed as straight as possible.

Then I clecoed the elevator tip rib assembly to the forward and aft elevator spars, and bottom skin (left elevator only). I then final drilled the holes common to the spars and tip ribs.

Then I attacked the top skin on the left elevator. The goal is to match drill three holes in the closeout tabs, but before doing so, the closeout tabs need to be supported from behind and in their final position. The first step, which I started on is to trim the trailing edge wedge.

Then the wedge needs to be sanded down on the outboard end where it will eventually butt up against the fiberglass elevator tip fairing. I marked the area that needs to be sanded down, but was too tired to continue tonight.

Well, I wrecked my first part tonight. I’m sure it won’t be the last, but it was a really dumb mistake. Nevertheless, I did make progress, clecoing together the left elevator, and then match drilling the forward half of the trim tab hinge.

First I used a step drill to enlarge a couple of holes on the left forward spar. These are for routing cables for the elevator trim servo. The servo sits inside the left elevator, right behind this spar, and has a push rod that actuates the elevator trim tab. I used the drill press and practiced with the step drill on a piece of scrap. It’s easy enough to use, and the holes came out looking pretty good.

I clecoed the forward spar to bottom skins

Then came the mistake. The plans call for the right rear spar to be trimmed, which is easy enough, except I trimmed the wrong end! Unfortunately there’s no way to fix this, and I need to order a new part from Vans. I trimmed this end:

But I should have trimmed this end:

Moving on, I proceeded with the left elevator. Here it is clecoed up to the bottom skin. You can see the two cut-outs, one for the trim tab in the trailing edge, and one for the servo access plate that will screw into some nut plates that are mounted on the doubler.

Now the drilling starts. The forward half of the piano hinge that holds the trim tab is match drilled to the holes in the rear spar (top flange). First, pilot holes are drilled in both the forward and aft sections of the hinge. Then the hinge is separated, and the forward half pilot hole is clecoed to the elevator spar flange. Then all the remaining holes are match drilled. I worked slowly and carefully to ensure the hinge stayed parallel with the spar. Here’s the finished step:

Last night I bent the elevator skin closeout tabs on both left elevator skins. This required clamping the skins between two pieces of timber, positioning them precisely, and then bending them over. I started the bend using a block of wood, and then switched to the rivet gun with flush set to finish the job. A little squeeze with the hand seamers and they were nice and square.

Between a couple of sessions yesterday and today, I final drilled the tip ribs and counterweight support skins, trimmed the trim tab skins, then fabricated the foam ribs.

Here is one of the tip ribs and counterweight support skins clecoed and in the middle of being final drilled. I had a hard time getting the front flange of the outboard tip rib to fit correctly inside the skin. The prepunched holes weren’t quiet lining up, so I tweaked the flange with hand seamers and eventually got it to work.

Next I trimmed a couple of pieces off the trim tab skins and the rudder skins. The trimmed parts are the close-out tabs on the edges of the trim tab, and on the rudder where the trim tab fits.

Then I made the foam ribs. This step has you cut out the template from the manual, glue it to the foam, then cut with the bandsaw. Finally, sand each rib to the exact shape. These all came out looking great. It was weird to cut up a page of the manual, but that’s the best option. Any copying of the page could result in a scale issue, or some other distortion. The foam blocks were easy to work with, and while a little time consuming, it was an easy process.

I clamped a straight edge to the sandpaper to ensure the ribs remained square.

Tonight I finished a plywood bracket to hold the Horizontal Stabilizer, then rigged everything up and hoisted it onto the ceiling in the garage. There’s just enough clearance on the storage cupboard doors, but I added some small bits of foam to the leading edge just in case.

Then I started on the Elevators, completing the first few steps. I cut out the ribs and sheer clips, fluted and straightened the outside ribs, and clecoed a bunch of stuff together ready for drilling, hopefully tomorrow.

Here are all the elevator parts, except the foam blocks and rudder skins. With this out on the workbench, the storage cupboards are starting to look empty.

Separating the ribs with tin snips:

Clecoed parts ready for drilling: