Another long building delay is over. I went to Osh Kosh, traveled a lot, looked after ill friends and family, and did some consulting work. Now the weather is improving I’m determined to get the project back on track.
I finally finished the empennage fairings. Spent way too much time fiddling around with the horizontal stabilizer tip fairings. That’s now all behind me, except for some fill priming. I’ll probably put a layer of glass tape across the HS tips to metal transition, just to ensure there will be no cracking in that area.
With that all done, it’s now time to attach the empennage to the fuselage. We lifted it into place, and everything fitted really well. After a match drilling session, it is now time time to take it off, debur, prime a few parts, and then attach it permanently.
It’s time to dig out the empennage and start some preparation for attaching it to the fuselage. I have to take the tail feathers off, but before doing that it’s best to deal with the empennage fairings – can’t put off fibreglass work any longer. As supplied the fairings require some trimming, and in general fit reasonably well but far from perfect. Here’s what I did to each part:
The elevator fairings – I didn’t like the uneven gap around them, and the front side had a gap in the centre of about 2mm. I used good quality 3M electrical tape as a release agent, scuffed the sides and front of the fairing, and applied a mixture of West Systems epoxy and micro-balloons around the exterior with the fairing cleco’d in place. Once this set, I sanded off the excess micro down to the tape, removed the fairing and then removed the tape. I had to repeat this operation in a few sections. I also epoxy’d a narrow strip of 0.025″ Alclad around the interior along each rivet line. I decided to use nutplates to attached the elevator fairings, so they can be detached if I need to adjust the elevator counterweights, so I used #6 nutplates held in place with NAS1097 rivets. I dimpled the elevators with #6 die, and used countersink #6 screws to complete the assembly.
For the bottom rudder fairing, I used the same method. I also added a metal backplate into which I can screw the tail-light.
For the top rudder fairing, I added the interior Alclad strip as well, even though I riveted it to the rudder. I didn’t like the idea of the rivets cracking the fibreglass as they were set. The front side of the top rudder fairing had a significant gap, which I built up with a layer of glass and flox, and finished with micro. I continued a thin micro application right across the front surface of the rudder balance arm, since this is a permanent attachment.
For the horizontal stabilizer fairings – I trimmed them, and using a balsa-wood insert covered in packing tape, applied a layer of glass and then two internal layups. After trimming I used some micro to build the edges back up a bit for the nominal 1/8″ clearance, with a concave inner surface that the elevator counterbalance arms can swing across.
The empennage fairing – I covered the tailcone, HS and VS surfaces with packing tape, layered flox along the surfaces where the fairing rests on metal, and cleco’d the fairing in place. I did this in two parts – the horizontal sections first, then after release and cleanup, the vertical stabilizer. The flox released OK, and to clean the packing tape residue off the metal surfaces I used Eucalyptus oil followed by Acetone. I then trimmed the fairing down to the trim lines, first with a Permagrit dremel cutting wheel, and finishing off with a sanding disk in the die grinder. I also trimmed and sanded any excess flox that had run down across the interior of the fairing. The end result was a fairing which fitted tightly against all surfaces. I’m going to fill some of the screw holes, with the fairing properly fitted like this it is not necessary to have as many screws along each edge.
Now I have a lot of pinholes to fill. I plan to do these with the epoxy / squeegee method, then will apply a coat of epoxy primer followed by a fill primer to complete the surface work. Overall the fairings have been quite a bit of work, spread out over several weeks. Weather is cold at present, and even using the “fast” hardener I’ve sometimes had to leave a heater on in the workshop overnight to get proper curing of the epoxy.
I put together the trim servo assembly and attached the cables. I haven’t decided what type of electrical connector to use, so for now I temporarily dangled an RJ-45 connector off the five Ray Allen servo wires. After a bit of juggling I was able to feed the two trim cables through the horizontal stabilizer bushings, the elevator bushing, and out the inspection cover hole on the bottom of the elevators. I marked where, on the read deck flange, some material will need to be ground off in order to accommodate the cables.
Having done that, there was no way to screw on the elevator inspection covers, per the plans. I recall reading about this anomaly – one of the few times where Van’s plans lead the builder astray – but for some reason I had still blindly followed the instructions and riveted the WD-415 cable attachment brackets to the inspection plates per page 9-15 step 7. I drilled out the inspection plate rivets, removed the attachment brackets, and threaded these onto the cables seperately. Then I simply cleco’d the inspection plates back in place. I know some people pop rivet these on during final assembly, meaning they have to be drilled out if (when) the trim cables have to be replaced. Not really a bad solution, replacement parts from Van’s only cost a few dollars.
I set up the trim adjustments, without being too fussy since it all comes apart again. The video is correct – the left trim tab does not travel “up” beyond the trailing position, only the right tab does.
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.
Riveting the elevator trailing edges was straightforward. The same angled squeezer die I made for the rudder worked fine and both elevator trailing edges are perfectly straight. I’m really sold on the method, no rivet gun required means less chance of unintended stretching/curving of the trailing edge. Like almost everyone else, I had trouble with the aft most outboard rivets on each elevator. There’s very little room there. The usual fallback is to use MS-319-BS pop rivets. I’ve got a few stainless steel cherry max rivets coming in various lengths for these sorts of situations, so I’ll wait for those.
I also fitted the hinge halves to each elevator and trim tab, and fitted the trim tabs. Used a squeezer for all of this riveting as well. There’s not much clearance and it’s important to not squash the hinge. None of the yokes I had worked for the elevator, so I cut the shaft off a 3/8″ x 1/4″ flush die, ground it smooth, and used a bit of gorilla tape to hold it in place on the fixed side of a 4 inch thin nosed flat yoke. This gave the required clearance to get around the back of the hinge bracket, while still being thin enough to get into the narrow gap in the first place (see pictures).
After closing up the first trim tab and riveting the hinge in place, I went to do the last operation – pop rivets on each end of the trim tab – only to find out that these were specified as countersink rivets, and I had not dimpled the holes. It was impossible to get the ends apart to dimple the holes at this point, so I’m going to have to use flush pop rivets on the right hand elevator. No big deal structurally or drag wise, just something to mentally beat myself up for as long as I own the plane. For the other trim tab, I was able to get the outboard side opened up enough to get a squeezer in there and dimple the holes, so that is one out of four sides done per the plans. I may put a layer of glass over the outboard side that has non-flush rivets, it would only be for aesthetics but there’s enough room to do it.
Now the tail-cone is out of the way, it’s time to go back and complete some jobs I shelved at the time. In this case, the elevator trailing edges and foam ribs, which were not done at the time because I didn’t have any pro-seal. For the trailing edges, I am using the same method as I did with the rudder (described here). In fact I used the same 50 x 50 x 5mm section of angle, just a different side and cut in half to separate the two parts that the left and right elevators were previously match drilled to.
This was my first experience with Pro-seal, a gooey substance that absolutely sticks to everything, especially latex gloves and workbenches. Hopefully I got it all done without gluing an elevator to a workbench. I only used the pro-seal for foam ribs (2 each elevator, 3 each trim tab), preferring to use 3M F9460PC double sided tape for the elevator trailing edges (less mess and avoids gluing the elevator to the straight edge).
I included the previously match drilled (half) hinge on the trim tabs when I cleco’d them up after the foam ribs were glued in place. Once the pro-seal cures it is all ready for riveting.