Friday, December 29, 2006

A fairly riveting tale

Time has been tight the last few days but I made some progress on the leg fairings. It's been difficult to get to the hangar for any meaningful amount of time, so I stopped by long enough to cart home the drill press and as many other tools and such as I could fit in the Subie and carted it all down to the provisional basement shop.

The goal was to get the hinges installed on the leg fairings to hold them closed at the back. I cut some hinge material to a length that would leave some overhang on each end of the fairing for clamps to get a grip on and clamped it into place. I then drew a line centered on the hinge and running the length of the fairing. This is mostly for show, of course, and should not be construed as providing any effective means of keeping me from drilling a line as straight as a Navy formation the day after a three day shore leave in the Phillipines. Any excuse to use my Harbor Freight drill press is welcome, though:

I clecoed every hole as I went, horribly paranoid that I'd get one drilled off center. This practice so sorely taxed my extraordinarily limited cleco inventory that purely out of necessity I soon got over my fears. They looked nice all in a row, though:

After countersinking the holes (I love working with glass - countersinking by hand is easy, easy, easy), I squeezed in the first set of rivets. They're small rivets and squeeze easily. It was easy to get at the first row since the fairing could be opened, but the second row was a bit more difficult. I had left the hinge wire in the hinge as long as I could, again out of a minor case of alignment paranoia, but now it had to be removed. Just to be overly safe, I pulled it out just enough the allow the fairing to be opened enough to fit the rivet squeezer in, and worked my way down to the end a rivet and a pull on the hinge wire at a time.

It took about an hour to finish up both fairings. I had Egg's iPod setup down there with me playing a series of beautiful clarinet solos recorded at one of my father-in-law's concerts and ex-copilot Hogarth at my side. Quite an enjoyable morning, truth be told.

I'm a huge fan of El Nino weather (at least the type we get), and took advantage of today's uncharacteristically moderate temperature to run over to the hangar and get the notchs cut in the tops of the leg fairings to form the tabs used to clamp the fairing to the leg. Once I got the die grinder and cutting disc all set up, I realized that I hadn't trimmed off the excess hinge material before riveting it on. Well, just the job for the cutting disc! I believe I was on the sixth cut of the eight required cuts when I broke the cutting disc, and darned if it wasn't my last. Ah well, I always enjoy a trip to Harbor Freight. New pack of discs and a few cuts later, the fairings are clamped to the legs. Well, after a protracted struggle with the hose clamps, stubborn little buggers that they are.

I'm going to turn that clamp around so the screw head is facing forward. I also need to do something about this:

The fairing is thicker than the gear leg, so the tab is being pulled down by the clamp. I'm afraid that could cause undue stress on the tab, and I don't want to be fixing it all the time. I'm thinking about cutting a thin aluminum doubler plate to rivet inside the tab to give it more strength, and to thicken that area up a bit so the tab doesn't have to bend as much.

Saturday, December 23, 2006

How fare the fairings?

Quite well, thanks. With the rough fitting finished yesterday, today's goal was to get the leg fairings mounted. The overall plan is to get the leg fairings aligned and mounted, then go back to working on the upper and lower intersections later. This allows me to defer the fitting problem I noticed yesterday with the lower fairings, but that's not the actual reason to back burner them for now. The gear leg fairings have to be aligned with the in-flight airflow so they don't act as forward rudders and impart unwanted yaw input in flight. Since it is the alignment of the leg fairings that is aerodynamically critical, it needs to be done before fitting the uppper and lower intersection fairings. The responsibility for any required give & take (positionally speaking) will be borne solely by them.

The starting point for today was with both leg fairings clamped to the legs:

The final alignment will require the plane to be up on jacks, but for now I had a nearer term task: the leg fairings are prevented from swivelling around after being aligned by means of a hose clamp that goes around a tab created by a couple of notchs cut in the top of the leg fairing. In order to cut the notchs in the right place, the fairings had to be pretty closely positioned to their final alignment.

I started by running some twine from each leg fairing back to the rear of the plane, where I duct taped the loose ends to a pair of jack stands:

The strings were held in place with pieces of tape:

It was the inside string on each side that I primarily interested in, and I wanted them each to run parallel to the centerline of the airplane. The centerline was determined by dropping a plumb bob from the center at both the front and rear of the plane, and connecting the two spots on the hangar floor with a chalk line. Each inner string was then measured for equal distance from the centerline at the front and back:

With the strings correctly aligned, it was easy to then align the leg fairings. I marked the lines I will later cut to make the tab that the hose clamp will hold. I've read that these tabs can be problematic as stress and vibration can break them, so I brought the leg fairings home along with my two-part epoxy and some fiberglass cloth. It's too cold in the hangar for the epoxy to set up. Once the chemicals get up to room temperature later tonight, I'll lay up some reinforcing flberglass in the areas that will become tabs.

I also spent some time planning the next steps. I'm planning on installing some rivnuts in the side of the fuselage and cowls and use screws to hold the fairings in place. Rivnuts are pretty cool - just as with a blind rivet, you don't have to have access to the back side of the surface to install them. You just drill a hole and push the rivnut in. It has a flange to hold it against the surface. You then screw a rivet puller mandrel into the rivnut and squeeze the handles. That pulls the mandrel, which causes the walls of the rivnut to compress against the inside of the surface.

Well, I wanted to practice installing some rivnuts in a lower consequence environment than the actual airplane. As you'll see, that was a fantastic decision! I tried both a size 8-32 and a size 6-32. The 8-32 went ok (it's on the left in the picture below) but required quite a bit of squeezing. I started on the 6-32 and was just noting how much easier it was to squeeze than the 8-32 when POP! went the mandrel. It just broke in half, leaving the remainder of its original length deep inside the rivnut. Had this happened on the airplane, I would have been (please forgive the vernacular) screwed. At this point, I do believe I will be using the 8-32s.

Here's another little job that I'm going to be facing. The blue fitting with the slant-cut face is the fuel tank vent, and as currently configured, it would be covered by the upper fairing. This I do not want. The slant-cut part is just a simple AN fitting that has been cut/ground down, so what I'll do is order an unmolested fitting of the same size and a matching female fitting. I'll get a short length of aluminum tube and borrow a flanging tool to make a short extension by attaching the female fitting to the end of the tube. I'll slant cut the end of the tube where it emerges from the fairing to preserve whatever the intended effect was of the slant-cut of the original fitting. I'll have to replace the male fitting too, and without even looking at the plans I fearlessly predict that getting to the other side of the fitting to remove the fuel vent tube is going to be an absolute bugger.

Oh, I'll see what I can do about touching-up the rusty spots on the leg mounts.

Friday, December 22, 2006

Fairing the gear legs

I've been flying around with the new wheel fairings for a few months now and actually have myself 90% convinced that they aren't going to fall off or in some way run afoul of the rotating bits down there, so I finally started changing out the old aluminum leg fairings for new fiberglass fairings. This also entails replacing the old upper intersection fairings with new, and adding lower leg fairings where none had existed previously.

As I've said before, what with this being essentially a hand made airplane there is no such thing as "off-the-shelf" parts. That said, pre-made fiberglass parts are available (at a fairly dear price!) that theoretically enable novices such as myself to at least get two-thirds done with a project (by starting us out half way) before throwing in the towel. They do the hard part of creating the molds and laying up the glass, and leave the easy stuff like fitting and installation to us. It's a pretty fair deal all in all, and I relish in the regulatory freedom that allows me to do it. And hey, it's fiberglass, and you all know what I say about working with glass: the great thing about it is you can trim a lot of material away quickly and easily. The horrible thing about it is, of course, that you can trim a lot of material away very quickly.

The first step is pretty obvious: remove the old stuff. Here's the naked leg exposed (and yes, I do expect an uptick of Google hits from using that phrase):

Probably more for reasons of ease in production than any kind of necessity, the gear fairing as it comes out of the box is far larger than what the final trimmed length will be. I made an eyeball measured rough cut on the left fairing and fitted it to the gear leg. The unmolested right side fairing is propped up for comparison:

The upper fairings come as a closed piece, but there's no way to install it that way. The old fairing was cut open in the back to allow it to slide over the gear fairing, so I went with that strategy. It was easy to get a nice, straight cut with a hacksaw:

Once the cut was made, I could slip the upper fairing into place and get an idea of how much more the leg fairing would need to be trimmed to get it to a length that allowed the upper fairing to fully enclose the leg fairing. You can see that there's still a good half inch of the leg fairing sticking out the back of the upper fairing in the picture below. It ultimately required another 3" to be trimmed off the top of the leg fairing to achieve the best fit. I, as is my wont, removed 3.5".

As I shortened the fairing, I had to keep reminding myself to trim from the top rather than the bottom so I could slide the fairing higher up the leg, thereby reducing the width that the upper fairing needed to cover.

Here's all the pieces/parts thrown into the general vicinities of where they will ultimately end up:

I haven't trimmed away any of the excess material around the lower fairing, but I can already see that I'm going to have a fit problem between the Team Rocket lower fairing and the Van's wheel fairing. I'm stumped as to how to better fir the lower fairing. I have a heat gun, so I could try heating the piece to see if I can get it to re-shape, or I could build it up with more fiberglass. The jury is out.

This is what it will look like when done (well, in general. I don't intend to use the making tape, for example, and there will be a lot of trimming on the upper fairing. Oh, and there will be paint, too.):

I posted a question in the Vans Airforce forum regarding what to do with the lower fairing, and in the meantime I'm going to go ahead and get the leg fairing properly mounted. That will require a little more cutting, a little bit of additional glass layout, and a fairly complicated operation intended to correctly align the leg fairing with the in-flight airflow. I'm actually kinda dreading that last part.

Later: less than an hour after I asked, I have a couple of answers. One suggests laying up some glass on the wheel fairing and the other calls for major rhinoplasty on the fairing. The wheel fairings aren't painted yet, so it would be no big deal to add more glass.

Sunday, December 17, 2006

Starting to hibernate

The weather has been unseasonably warm this weekend and I did take advantage of it for a short flight yesterday, but for the most part I've been concentrating on in-house projects. Yesterday we had winds from the south at 11 gusting 15 and a high overcast at about 25,000' which was fine for a short hop to exercise the equipment and brain, but wasn't really a clarion call to spend a lot of time outside.

Since I was to be flying simply for the sake of flying, I picked an item from my practice list to work on. I deciced to do a few stalls, then investigate the edges of the stall around the type of crossed-control situations that cause spins. One of the more deadly traps a pilot can fall into is the "stall-spin" while landing. A number of things can lead to the stall-spin, but they fundamentally all share some constants: cross-control input (right rudder & left aileron, for example) and insufficient airspeed (or excessive angle of attack; they go hand-in-hand for the most part). A stall-spin from the landing pattern typically occurs on the base to final leg turn, where your altitude doesn't allow for a recovery before hitting the ground.

I started at 4,500' and slowed to stall speed, adding more and more rudder as I slowed. I counteracted the rolling tendencies from the rudder with opposite aileron. The normal stall in the RV-6 is a bit more abrupt than that of the typical rental, but not shockingly so. The cross-controlled stall (aka spin entry) is similar, but much more spectacular. A couple of fast burbles and BAM! I'm facing 180 degrees opposite heading and the nose has dropped to what appeared to be a nearly vertical attitude. Releasing the controls (keeping the rudder in would have kept the rotation going and I would have been in a spin) and gently pulling out of the resulting dive resulted in at least a 500' drop, probably more, before I achieved level flight. I climbed back up and did a few more like that, and some of the more benign straight ahead stalls before heading back to an acceptable crosswind landing.

As I arrived at Bolton, I assessed my normal landing pattern in light of what I had just learned about the stall characteristics of my plane. I fly a fairly wide pattern and I usually try to compensate for the winds just like we all practiced in those interminable ground reference maneuvers way back when, so I don't typically present myself with a reason to over bank or get my airspeed too slow. I did seem to keep a slightly keener eye on the airspeed indicator, though....

The hibernation project that allowed a brief 20 minute flight to sufficiently address my flying needs is to assess and review another piece of PC hardware attached to my PC-based flight simulator. Every now and then, a new piece of gear comes along that addresses a long-hated hassle in the control interface between human and virtual airplane. The most recent had been the NaturalPoint TrackIR system that captures my real-world head movements and translates them into the electronic commands that command an indentical movement in the virtual world. TrackIR, by far, was the coolest thing that every happened to fight sims. With the computer view tracked to physical head motion, it was as close to actually being in a cockpit as you can get, except for one thing: to operate switches, knobs, etc. it was necessary to "look" at the knob, then click on it with the mouse cursor. Well, that wasn't that easy. It was very hard to hold my head still enough to keep the knob from moving away from my mouse cursor. There was a way to lock the view while I clicked on the knob, but that was extremely invasive to the flying experience. Similarly, I also hated having to use the keyboard to type certain commands, primarily digits associated with menued ATC responses.

Enter the CH Products Multifunction Panel (MFP). It's basically a collection of 25 individual buttons, very much like the buttons on your keyboard. Each button can be placed anywhere on a 9" x 6" clear plastic surface. A printed picture can be inserted underneath the plastic surface. Each of the 25 buttons can be programmed to emulate a keyboard stroke. These mappings can then be used within the flight simulator to perform various functions.

After a few hours of figuring out how to program it, I had a configuration that let me set comm and nav radio frequencies, set the CRS and HDG bugs on the PFD, choose appropriate responses from the ATC menu, and use the Direct and Menu buttons on the GPS. I then made a series of IFR flights in the G1000 equipped Cessna 172, Mooney Something-or-Other, and Beechcraft Baron. The difference was astonishing! After swearing never to "fly" without the TrackIR again, I easily spent 4 hours using the 2D panels (no TrackIR) and the CH MFP. Once I get my USB hub moved from the other PC onto the fligth sim PC, I'll be able to use both!

Beyond being more realistic, it was also much easier to interact with the radios and ATC by using the buttons. It helped that I had taken a screenshot of the G1000 from within the flight sim and printed it on my photo printer. That made it easy to locate the buttons I needed to perform various functions with just a glance over at the MFP.

I have a lot more research to do with the MFP before I can write a full review, but so far this looks like it will be on the list with the TrackIR as another must-have item for flight sim flying.

Tuesday, December 12, 2006

A tour of Columbus

Sunday morning I decided to make one more attempt at getting the microphone to work by purchasing a cheap little amplifier to boost the microphone signal a bit more, but to no avail. I'm going to have to give up on the audio for now.

The weather was nice, albeit with winds from the southwest at 10 gusting 15. That's right down the runway at Bolton, so it wouldn't be a problem. I thought I'd head over to MadCo to gas up, but take an aerial tour of Columbus on the way. Well, it's not exactly "on the way" - it's actually the exact opposite direction. The plan was to climb above the class C airspace that surrounds Port Columbus Airport and tour the OSU campus on the way downtown. With the relatively high pressure and cool temps, the climb to 5,500' went very quickly.

I'm getting better at managing the limited resources of battery power and recording tape in the camcorder, and in fact I thought I had this video thing down to a science. Well, not quite as it turns out. It seems that the camera must have gotten bumped and knocked slightly off alignment since it now has a constant bank to the right, but I didn't notice it until I got back and was watching the tape on the computer. When I realized that I had been leaning to the left in my chair for 10 minutes, it finally hit me that the camera wasn't level.

Here's the video:

(this video was captured at 640x480, so you can click on it to go to its page on YouTube and watch in a larger window)

I couldn't find anything to talk about in the last few minutes of narration, so I just left it silent. That's when I really wish I had engine and comm radio sounds in the background!

Sunday, December 10, 2006

Time for a Bleg

A "bleg" is a blog beg, for those of you not in the know. Here's the deal: I'm having far more difficulty getting an external mike to work with my Canon ZR 200 than I had imagined possible. The ZR 200 has inputs for external video and stereo audio, via a plug that came with it. The plug has RCA inputs for audio and video, and works fine when I attach something like a VCR to it. It also works fine with the bullet cam attached as you've no doubt seen in previous posts. But... I just can't get it to work with an external microphone. I tried a passive mike, a powered lapel mike, and a powered lapel mike run through an amplifier. Nothing seems to generate any sound into the camcorder. I even tried unplugging the RCA audio plugs from the camcorder and plugging them into a stereo. Still no audio. I'm now quite sure there is something I'm missing in my Lego-style glomming together of cables, adaptors, and microphones.

The fundamental question is this: how can I get an audio signal from a powered lapel microphone with a 1/8" stereo mini-plug into an RCA plug audio recorder?

Saturday, December 02, 2006

Still no audio

The little microphone I ordered arrived a couple of days ago, so today seemed a great opportunity to try it out. It fit nicely in one of the cups of my headset, but the adaptor that I had to match the mini plug of the microphone to the RCA input of the camcorder was the wrong size. I'll have ot make a visit to Radio Shack to find the right adaptor. I didn't know it wasn't working until after I got back to the house, but the video turned out well enough that I decided to narrate it again and put it up on YouTube:

The landing at Urbana was middling bad, but the return to Bolton later in the day was much better. Neither was as good as what I can do without the winds, though.

In the video I mention a 172 on downwind at Urbana. That guy confused me a bit. He called on the CTAF about 8 miles south of the airport and indicated that he would be landing on 20. I waited until we were six miles out and announced that I'd be making a left downwind approach to 20. "You're going to make left downwind?" he asked, as if that was some kind of surprising decision. Apparently he had been planning on crossing the runway to make a right downwind, which makes no sense at all because 1) it would take longer, and 2) would violate the standard left pattern rule which states that unless a landing pattern is defined as unstandard (right traffic), then it is standard left traffic. Oh well, he did the right thing by following me into left traffic, so all ended well.


I fiddled around with the microphone this morning, and the problem does not appear to be with the adaptor as I had originally thought. I can barely get the new microphone to work on the PC, much less with the camcorder. I don't know if it's a problem with the microphone, its battery, or the way in which I'm trying to use it, but I'm becoming passimistic on the question of whether I will be able to capture the ambient flying sounds in the way I want. That's a shame because I think my narrations aren't nearly as interesting to listen to as the real sounds would be. Drat.