Archive for the ‘Tip fairings’ Category

Red beacon

Sunday, October 28th, 2012

I've been planning to put some kind of red flashing ground-recognition beacon on the airplane all along, and this weekend I finally got around to making it happen. For years I've been pondering exactly what kind of beacon I need and where to mount it – see here and here for details of previous plans that didn't get completed, plus thoughts on red beacons in general. What ended up working in my favor is the fact that, while I was trying to figure out what to do, the state of the art in LED technology has advanced to the point where it now makes more sense to use LEDs rather than xenon strobes or halogen flashers for this application.

The particular unit I picked is the Vertex LED lighthead by Whelen. These guys are known in aviation circles for making certified strobes and nav lights, but they make lots of automotive products too. This one is designed to work as a warning light for a cop car or other emergency vehicle, but it happens to also be the perfect size for an airplane too. Here's a photo I grabbed from the internet since I forgot to take a "before" shot prior to getting started:

I played with various mounting positions until I decided which one I liked best – it turned out to be the top of the tail, just like on your grandpa's Cessna. Then I got out the rudder cap and started cutting away at it with a unibit and Dremel tool.

The light will be held in place by two little pieces of scrap angle that will attach to the inside of the rudder cap.

A view from the bottom side. The beacon heatsink just fits into the widest point of the rudder cap.

That has the added advantage of putting the beacon about halfway back from the leading edge of the vertical stabilizer – farther back than on a Cessna – where the light shining directly forward will be blocked instead of getting into the cockpit and annoying me by glaring off the instrument panel.

The circuit board inside the beacon is flush with the top of the rudder cap. Now we just need to do something about the exposed shoulders of the heatsink sticking out into the breeze.

I covered the beacon with saran wrap and then laid up several plies of glass tape over it in a smooth shape:

It's a little late in the season to be doing fiberglass work – i.e. the temperature is a bit low in the garage – but for small projects you can cheat and use a heat lamp to get the resin to cure in a reasonable amount of time.

After sanding the initial layup, I installed the beacon again and followed up with a flox/cabosil mixture to build up the contour and give me a nice sharp edge around the opening for the lens.

I also laid up some flox inside the rudder cap to give the body of the beacon a nice solid shoulder to sit on, as well as thickening up the inside of the lens opening to avoid having a knife edge there.

After letting that cure and sanding it back down, the general shape of the "bump" for the beacon was basically done.

I applied one more coat of dry micro with a squeegee to fill in the low spots, then sanded it smooth.

A quick spray of primer dressed it right up. I'm quite happy with how the shape turned out. There are some small surface imperfections but I'll let the painter deal with those.

The beacon lens is very low profile. I still need to countersink the mounting holes in the sides, but that can wait until I get back the drawer full of #4 tinnerman washers I loaned out.

Now that it's all sanded smooth and blended in, the slight swell for the beacon is hardly noticeable:

What's that, you say you want to see my new rudder-mounted ground recognition beacon in operation? Very well:

It's hard to properly capture with the camera, but trust me, this thing is plenty bright.


Canopy work aborted

Saturday, March 31st, 2007

After putting some protective tape over the end of the slider frame latch tube, I flipped the canopy over and laid the frame inside.

The goal is to get the frame aligned on the previously marked centerline, in the fore-aft location that results in the best fit along the center spine tube. Then you mark the location of the latch tube and drill a 5/8" hole. I got as far as marking the hole location, but the temperature didn't get up nearly as high as I thought it would, so I had to give up on drilling/trimming the canopy for another day. Bah.

In an effort to find something else to do, I dug up the subpanel pieces, dimpled the top rib flanges, and clecoed the whole works into the fuselage.

Then I deburred the forward top skin, which I hadn't yet bothered to do. I dimpled where I could reach along the edges, leaving the holes along the firewall undimpled for now – the cowling attach hinges still need to be match-drilled there, much further down the road. Then I packed up the skin and drove over to John's to use my DRDT to dimple the rest of the skin. Not a very efficient use of building time, but it felt like a good day to spend a couple hours driving.

Somewhere in there I did some more filler work on the left horizontal stabilizer tip fairing. I've had this clamp for at least ten years and I'm pretty sure this is the first time I've ever used it.

Also, I stopped at Lowe's and tried to buy a new belt sander, but they were out. Bah.

Misc stuff

Sunday, March 25th, 2007

I spent the whole day in the garage but didn't take many pictures. I guess I didn't actually get all that much accomplished – mostly I puttered and cleaned up the garage. It was great to be outside in the nice weather though.

One of the pre-tail-mounting chores I've been meaning to do is drilling the holes for the strobe and nav light wires that will go through the vertical stabilizer spar into the rudder. I picked the same location as Dan for much the same reasons – with the taildragger there aren't many other good choices for where to run these wires. I drilled a 5/16" hole for the strobe cable and a 3/16" hole for the nav light wires. Both holes are a little oversized so I can use a few layers of shrink tubing and some RTV to protect the wires from chafing.

Another day, another round of filling and sanding empennage fairings. I'm just doing a little bit every work session, fitting the glass work in between other tasks that are more fun.

I rearranged the garage a bit, and made a little table out of a sheet of plywood and a couple sawhorses. This is where the canopy is going to sit while I work on it. Yes, I've decided to work on the canopy some more before I put the airplane on the gear and mount the engine. Matthew convinced me that it'll be easier to get to it while it's down low and not high up on the wheels. Plus it seems to be warm enough these days to start thinking about working with plexiglass again.

I got out the canopy frame to make sure it still fits – yep:


Installed empennage gap fairings and horizontal stabilizer

Saturday, March 24th, 2007

The plans call for you to install nutplates along the F-709 bulkhead where the fiberglass empennage fairing and the forward end of the aluminum empennage gap fairings will attach, and then drill and tap holes in the longeron underneath the stabilizer to attach the gap fairings along the rest of their length. I decided to install nutplates everywhere instead of tapping the longeron – a tapped hole has no ability retain a screw and I remembered how one or two of these screws were always backing out on my old airplane.

Installing nutplates here took only a few extra minutes and was no big deal to accomplish. I did check with Van's before I did this, since I was wondering if the extra rivet holes would do anything structurally back there. Here's what they said:

Date: Tue, 12 Dec 2006 07:38:14 -0800
From: Van's
To: Matt
Subject: Re: Nutplates for empennage fairing

It's OK, but why would you want the extra expense and work?

Vans

I think they must have an automated process that sends that reply anytime they receive an email that starts with "Is it okay if I…"

After double checking my todo list to make sure I wasn't forgetting anything, I vacuumed out the tailcone one last time and bolted the horizontal stabilizer on for good.

Here is one of the empennage gap fairings installed. The topmost hole is left open because it's shared with the fiberglass empennage fairing. I used the hand seamer to get the forward edges of these fairings to lay down nicely on the fuselage skin. I'm not sure what to do about the forward end of the rubber channel – maybe I'll trim it at an angle to try and help keep the wind from peeling it up.

Before turning in I reattached one of the horizontal stabilizer tips and put on another coat of filler to help smooth out the forward edge where the fiberglass and alunimum come together.


Empennage fairings part VII

Sunday, March 11th, 2007

Still not too much time to work on the project lately. I did have a chance to reinforce the balsa ribs on the horizontal stabilizer tip fairings with a mixture of epoxy and flox, and to fit and install the 4-40 nutplates that will hold the fairings on.

I mixed up the usual batch of micro filler and smoothed out the transition between the tip fairings and the stabilizer, with an extra blob at the nose to allow a perfect fit after it's all sanded down later. I also put a big glob of filler on the outboard corners – a lot of this will get sanded off, but what remains will be the the first step of building up the tip fairings to match the contour of the elevator tips.