Mounted the vertical stabilizer, elevators and rudder today – so for the first time, all control surfaces are together on the Empennage. Today also happens to be the 1 year anniversary of the arrival of the Empennage kit! I’m glad I built a sturdy wheel-around cart for the tail cone, because once it is all assembled, the rear end is quite heavy. I wouldn’t really like to work on the thing while it was balanced on a workbench.
[30 Aug] Update: I finished adjusting the rudder, and installed the elevator pushrod. I also tried putting the empennage fairing in place, and it looks like a good fit.
Continuing on with the empennage attach steps, I match drilled the elevator control horns for the push rod bearing, and set the completed elevators aside. I made up the four spacers for the horizontal stabilizer attachment brackets. Whenever I have to make several small, matching parts like this, I always as much as possible try to cut them together, and mostly de-burr them together, before doing a final de-burr individually. This way they match up properly.
I set the horizontal stabilizer up on the tail-cone, and match drilled the rear spar mounting holes. With these bolts in place, only a small adjustment was required to bring the alignment true. I fretted about drilling #12 directly through the 1/2 inch plus stack-up of Aluminium, but using a new 12 inch drill and plenty of Boe-lube, the front mounting holes were easy enough to do. I took everything apart, de-burred, then bolted the horizontal stabilizer back in place. Amazingly, the alignment tip-to-front-centre was still exactly right.
Next job will be to mount and match drill the vertical stabilizer.
Today I started the empennage assembly procedure, beginning with attachment of the elevators onto the horizontal stabilizer. There are some special tools I bought a while ago to help with this, simple cheap tools from Avery but well worth having as it turns out. One tool is for screwing on the bearings, and the other is a set of temporary pins so you don’t have to fiddle around with AN-3 bolts during initial trial assembly. In addition, I made up a crows-foot spanner, for (ultimately) torque-ing up the jam nuts, by cutting up a 9/16″ straight ring spanner, bending things around a bit, and welding it back together along with a 1/4″ drive socket at the far end.
I had trouble believing this, but both elevators – with bearings set up per the instructions – fitted with perfect alignment and no further adjustment required. A consistent gap along the length of the elevator leading edges, as well as the counterbalance arms. Up and down rotation through the required angles with no interference. I never cease to be amazed by the quality of the Van’s kit and instructions.
I drilled the centre bearing hole in each elevator horn, and re-fitted both elevators. Although the plans call for a #17 drill, I found that a #16 drill (larger) fitted through the drill bushing, so that’s what I used. With each elevator in the trailing position, the horns are closely matched. Next step is to drill the pushrod bolt holes.
Rolling the rudder leading edge was straightforward. I found that I needed to work the upper sections with a piece of 1″ OD pipe, in order to get enough bend on them. With my 1 1/4″ rolling tool, the sections didn’t fit together cleanly enough at the top where there was not as much depth to work with.
Unlike the elevators, for some reason Van’s did not punch the rivet holes out to #30 for the rudder, so I had to match drill them. I drilled them #33, then drilled with a #30 reamer, to minimize the amount of material that had to be removed to de-burr the holes, since the skins are so thin to start with.
For a litany of reasons, I’ve had to take a break from building over the past 6 weeks or so. Now it is time to get back to work!
I have a few empennage jobs to catch up on – including rolling the leading edges. The technique I used was described here. I made up a rolling tool by welding some 3/8″ sockets inside a piece of 1 inch ID galvanized water pipe. This is sold in Australia as “fire pipe”, and has a 3.2 mm wall thickness. The OD is around 33 mm, near enough to the 1 1/4″ that Van’s specify. I drilled three 5mm holes in each end, then welded the sockets in place through the holes, filling the holes up with weld and then grinding the excess down flat with an angle grinder. Finally, I sanded the surface of the pipe to remove any rough points.
I put masking tape on the inside surface of the leading edge skins, to avoid any chance of scratching from the steel pipe. Scrap wood was used to ensure the rolling tool was aligned properly as it was strapped on with Gorilla tape. The wood spacer was then removed, and the section was rolled. After rolling, the Gorilla tape can be carefully torn off, and the masking tape removed.
In the pictures, some flecks of primer can be seen lying around. These come from the blue vinyl, where the primer doesn’t adhere. Primer doesn’t come off any of the Alclad, the adhesion is way too good to be bothered by Gorilla tape.
If the rolling tool is made 670 mm long, a single tool can be used for all sections of the elevators, as well as the rudder.