Empennage


Empennage Fairing 3

My Doug Bell tailwheel fork arrived today – I got the black painted version from FlyboyAccessories. I wanted to link it all up to see how everything fit. I then set it aside. The tailwheel is all but install – only a few bolts to torque and attach the rudder cables and she’ll be good to go.

Next, I gave the empennage fairing a little love. I checked fit versus the aluminum fairing that is installed underneath the horizontal empennage. And then I cleaned it up and gave it another good spray of filler primer.

While that was drying up I worked on the lower aluminum fairing and rear cover plate. Van’s instructions call for tapping the longerons to accept screws and then machine countersinking the skins. I’ve read that some people just rivet this part on, as there’s never really any reason for it to come off. I have to say, I’m not highly impressed with this part or Van’s method for attaching it, but I don’t see any reason to rivet it either. When in doubt, I’ll stick with the Van’s method.

First step was to match drill the fairing, and then debur and dimple. Next step was to drill everything to a #36 – then machine countersink the skins and longerons.

I’m pretty happy with the results.


Empennage Fairing 2

Next up in the empennage fairing is basically cleaning everything up and making it a smooth surface. I use Rage Gold body filler for final prep. Obviously the outside needs to be smooth, but I also want the inside to be relatively smooth so that it doesn’t scratch things too badly when taking it off yearly for inspection.

Using two saw horses a great way to position the fairing for work.

img_2152.jpg

img_2155.jpg

After filling everything to my satisfaction it was time for a layer of filler primer. This serves two purposes – first its going to need to be primed anyways and fill pinholes, but secondly it also serves to make flaws more obvious. Areas that aren’t smooth enough, are poorly rounded, or aren’t flat will show up much easier under a layer of primer than before.

And there were definitely imperfections, however, not nearly as many or as bad as I though. In fact I was quite tickled with myself how well it has come out so far!

img_2186.jpg

Here’s a good view of one area with some imperfections. The intersection of the new overlap is a bit rough.

img_2187.jpg

img_2185.jpg

img_2189.jpg

img_2188.jpg

After this I pulled the empennage back apart so that I could install the nut plates at the points I plan to attach the fairing.

img_2229.jpg

There are some other things I need to figure out here – such as the back access plate.

img_2231.jpg

And the aluminum horizontal stab fairing.

img_2232.jpg

I countersunk the fiberglass for torx screws. I was super happy with the countersinks, or the strength of small screws through relatively thin fiberglass. I decided to go with the Tinnerman washers (ACS calls them countersunk washers). I actually think they look better with the tinnerman washers installed.

img_2451.jpg

I will have a total of 4 screws on each side. Two on the horizontal empennage upper surface, and then two more back behind the elevator horn. I call that success in my book!

img_2452.jpg


Empennage Fairing 1

Okay. Seems like every post in the past year begins with an apology about the lack of keeping the log up to date. Today is no exception. This post will encompass the past two months or so that I’ve intermittently worked in the shop. While I haven’t been good about updates, I have been doing an OK job of taking photos. I’ve recently started work again on the plane, with my first project to tackle all things related to the empennage. First among these was the empennage intersection fairing.

As I’ve done the fastback modification to the fuselage, my empennage fairing supplied by Van’s isn’t going to come close to working. My approach was to cut the fairing into three sections, and then fiberglass the gaps.

Here is the fairing sitting on the attached tail feathers. You can see the cut – there is an identical cut on the opposite side.

I put packing tape on the airplane to make clean up a snap. (Be sure to use some tape of decent quality – use cheap stuff like I did, and – well you’ll see a bit later)

In addition to glassing the gaps created by the cut, I want to make sure I have minimum gaps and a nice tight fit. Here in the next few photos you can see some of the current gaps. I also want to use as few screws as possible for the attachment points.

My approach to glassing it was fairly simple. I secured the fairing with clecos, and then put two strips of fiberglass over top. A thick 3″ strip, and a thinner 2″ strip.

I used my trusty bag of lead shot to weight down the front portion as there are no clecos or holes in this section. The bag of lead shot does a better job anyways!

I also want my fairing to wrap around the front of the horizontal empennage just slightly. This is a pretty popular modification, and relatively simple. I can tell I am a bit out of practice, as my application of fiberglass here was a bit rushed and sloppy. I should have taken the time to split the front of the strips I was using, and have more careful measurements.

Next, I removed the fairing, and applied flox underneath the outer strips to fill the void. I then applied two strips of fiberglass to the inside of the fairing. Don’t overdo the flox, the idea is just to ensure there are no gaps between the inner and outer fiberglass. Now, here’s another mistake that you should avoid. DO NOT fold fiberglass over from one side to the next. I know better than to do this. I even thought to myself when I did it – “I shouldn’t probably do this – its going to give me air pockets and be a pain later.” But, again, being out of practice I’ve forgotten to listen to my sensible side and did it anyways. My sensible side was right – it was problematic later on. End of the world? Certainly not. But a mistake I should have avoided.

After it set up, I did some basic trimming and shaping. You can see its starting to really take shape.

Now its time to start filling in the gaps. Use flox and micro as appropriate. Micro for flat surfaces – flox for anything near an edge or requiring any strength. I used a small amount of micro¬†to fill in the gaps between the fairing and the surfaces. This micro was only a very small amount and served as a distance guide for a subsequent application of flox, and then finally a layer of fiberglass. This made the fairing a little thicker at points, but the gaps are gone and I’m hopeful the extra thickness will help prevent the empennage for curling / bowing due to heat changes.

The rest of this story is primarily filling, and sanding. Repeat.