Friday, January 30, 2015

The Bug

February. The worst month of my life. We aren't even there yet, and here I sit with a fuzzy head, an aching chest, and a cough that engages my gag reflex in a most disconcerting way. The weather gurus are predicting another half foot of snow, timed perfectly for my Monday commute across town. It's dark for more than half of the 24 hour day.

What's not to like?

I have, over the years, learned not to make important decisions in February when my seasonal depression is at its peak and having an undue influence on my general outlook on life. The month of February is the closest I get to something akin to clinical depression.

There was a time, though, still fresh in my mind, when I didn't suffer nearly as greatly. I remember a time when I would be outside, or near enough to, with temperatures in the teens doing productive work, and enjoying it. It was, in fact, a spell of time that I had such an overarching interest in a project that I was working on that weather, daylight, and day-to-day frustrations were pushed lower on the intensity scale than normal.

This is a nostalgic view, of course, and even in the very beginnings of my annual doldrums I recognize that. That said, nostalgia may soften the sharp edges of the past, but it does not invent the memory of good times out of whole cloth. The more difficult and frustrating times may lose some of their potency, and the highlights may shine brighter in reflection than they did as the happened, but even after applying the filter of time those memories remain valid.

I miss building.

I miss blogging about building.

I miss always having something to do with my time.

As much as I enjoy owning and flying a brand new, state of the art airplane, I feel like I lost something on the day it was deemed to be "done."

This did not start today. It did not start this week, or even this month. I've tried coming up with other things to do, but I built the RV-12 for a reason: building an airplane was something that I had always wanted to do. As it turns out, it still is.

It's tricky, though. I have no interest in replacing the 12. It does a great job at satisfying just about every one of my aviation needs. Nor do I have any interest in building another 12 - that would seem pointless in the same way that I don't have the desire to own a vacation property: I like variety.

So, what aviation needs are not served by my nifty little machine?

Well, it certainly is handy for flying out to visit folks, or to go to nice places like the Ohio Bass islands easily. It's great for giving rides to people that have never been in a small plane before and watching their eyes light up when they take the controls, even briefly.  It's even a great way to travel a hundred miles or so for an average meal at an airport diner.

That last one there - the one where I'm flying hundreds of miles for a burger that I wouldn't have driven ten miles for. That's the tell. It's not the burger that is the appeal of those trips, it's the act of flying. And this is where the 12, although comfortable and capable, falls just a wee bit short. Yes, it's flying, but it's flying thousands of feet above the ground, enclosed in a wind proof capsule, surrounded by metal.

Nothing wrong with that at all, but it lacks something of the very essence of flying. The wind in your hair, the scents of the land you're flying over, the intimacy of being only hundreds of feet off the ground, the freedom to frolic in three dimensions in the way that only an airplane strong enough to stay in one piece at +6 and -3 Gs.

This is the type of flying that would complement that of the 12, not replace it.

It's like I've always said, when it comes to airplanes, you need at least two but no more than five.

So where does one come across a machine that provides all of that?

Open cockpit biplanes.  Wood, fabric, simple instruments, and just enough modernity to keep from getting lost.

That's what I would like to build.

Fortunately, kits exist for that, and they are pretty reasonably priced. Take, for example, the Fisher Flying Products Youngster V:

Fisher is an established kit manufacturer with decades of experience behind them and a fleet of no less than fourteen different airplanes running the gamut from ultralight airplanes all the way up to an 80% scale replica of the venerable de Havilland Tiger Moth.

The Tiger Moth replica is an attractive option, but at double the cost and almost twice the size as the Youngster, I just don't think it fits the "low-cost" requirement and also is just too big.  The single-seat Youngster evokes the Mitty-esque sense of the early heydey of sport flight much better.

The Fisher planes are wood and fabric (well, Dacron these days - authenticity often equates to maintenance burden and unreliability) kits, designed for first-time builders on something of a budget. The wood is aircraft-grade Sitka spruce for things that are built up of stringers and birch ply for the solid skins. Engine options include a 50hp Rotax two-cycle or a 65hp Volkswagon engine.

A lot of people look askance at VW powerplants on airplanes, but just as many are equally distrustful of the Rotax 912 I have in the RV-12.  Their viewpoint is not entirely unfair. VW engines have been used in homebuilt planes since the very infancy of the genre, and as with anything that has been around for awhile, they have gained and kept a reputation based on issue with the earliest efforts. This is why you don't fly to Europe in a Wright Brothers jumbo jet.

The modern aviation VW engine pretty much just uses the original engine case to house critical components beefed up for aviation use. One of the leading providers of aviation grade VW engines describe some of the enhancements:

The Crankshaft.

The heart of the engine is the crankshaft. It has to be able to absorb, dissipate and transmit. Our 82mm forged E4340 steel crankshaft is made specifically for aircraft use. It features a rectangle flat milled key for the prop hub. The crankshaft has a 3 degree taper on it that is mated to our Force One prop hub. The bolt that retains the hub is a fine thread bolt that is 3.5" long. The threads in the crankshaft are machined in the crankshaft about 3" down from the end. For the first 1.250" the thread is relieved so the pulling or retention loads is placed at the rear of the thread in the larger diameter of the crankshaft. This crankshaft is made specifically for the rigors of driving a propeller. It is not an "out of the box" automotive crankshaft as used by one competitor. In the 25+ years this current crankshaft design has been manufactured, it has never suffered a failure. Our E4340 crank is manufactured from a forged billet and machined in the USA. 69mm crankshafts are made from a 4140 forging.

The Force One Prop Hub and Main Bearing.

While not totally unique to aviation, it is in many respects when combined with our crankshaft. We recognized from early on from a number of crankshaft/prop hub failures with 82mm crankshafts and shrink fit and short tapered hubs, that perhaps it was not the best way to build stroker engines for longevity.

The Force One Prop Hub rides in a engine lubricated bearing that the case is machined out for. The Force One Bearing is pressure lubricated, utilizes 2 seals for oil control. The total bearing area has 4 to 5 more surface area than does a standard #4 position, VW bearing. But the important point is the hub is supported in the bearing instead of being attached forward of the bearing, as is the case when using a shrink fit or standard tapered prop hub. As the fit between the hub and the crank is on a 3 degree taper, it can be removed repeatedly without wearing out either tapered surface. With shrink fit hub, the .002" interference fit will eventually erode with multiple removals.

With our Force One Hub, we can still use the brass distributor drive gear to drive a secondary or primary ignition system. Another competitors crankshaft does not have the brass gear on the crankshaft and cannot use a primary or secondary ignition in the distributor hole.
They also offer an optional second ignition system, which would definitely be on my must-have list.

It's hard to figure out the total cost of the engine package, of course, because you have to add in things like the engine mount and propeller, but I'm estimating that it would top out at just about the same cost as the airframe. The airframe kit is very complete, up to and including the covering fabric. It sells for $8,700, but you have to throw in a few hundred for crating and shipping. They also sell the kit as three separate subkits, but that only serves to triple the additional charges associated with getting the thing to your door.

Where would I keep it? There is a small, grass runway airport no more than five miles from my house.

One thing that's still an open question, and a relatively big one at that, is how much of it could be built in my basement - one aspect of building the 12 that no amount of nostalgia can gloss over is just how hot and cold it can get working out in the hangar!

So, will I do it?

I don't know. I try to never make decisions like this in February.

Monday, January 19, 2015

Location, Location, Location...

Things everyone knows about locations:

  - Don't build your house near a pork rendering plant, or (literally) a stone's throw from a high school, the criticality of the latter being dependent on the number and size of glass windows that face it.
  - Don't wear Maize & Blue to the Ohio State / Michigan game when it's in Columbus.
  - Don't buy sushi at a 7-11 (unless it's a treat for your cat).
  - Don't count your cards when you're sittin' at the table. There'll be time enough for that...

And here's one that not many people know, unless they've built and flown an RV-12:
  - Don't mount a $400 oil pressure sensor directly on an engine.

Luckily, there is now a somewhat cheaper replacement for the $400 sensor, and I think RV-12s are now shipping with a different type. That said, I believe the newer sensor is still attached directly to the engine where it is likely to meet the same fate as the two previous models.

In addition to the lower cost replacement sensor, there is also a nice little kit that you can buy that relocates the sensor to a presumably less dangerous neighborhood. It's sold by Aircraft Specialty, the very same folks that sell the fuel and brake lines that I have used to upgrade those provided by Van's.

At first glance, it doesn't seem all that cheap at $144.95, but when you consider it more deeply you will see that it's a bargain. It comes complete with everything you need but minor hardware such as a #14 size Adel clamp, an AD3-5A bolt, a dab of thread sealant, and whatever you like to use to restrain and protect engine hoses.

If your existing Honeywell sensor is already fried, you will also need a replacement. I went with the one that Lockwood Aviation sells since it's a direct replacement for the one I had and I wasn't in the mood to experiment:

Product: Oil pressure sender, 1/8 npt, 4.2ma
Part Number: GAOPSNDHK
Price : $129.95

These are the factors that I considered before parting with the cash for the kit:

  - Even the lower cost sensor that replaces the $400 one is $130. Mine failed at 70 tach hours.
  - Replacing the sensor in it's location on the engine is more difficult that replacing one mounted on the firewall.
  - The wire that runs from the Skyview to the pressure sensor has to be routed alongside the engine. This can be problematic.

For a person of moderate skills, the relocation is pretty straightforward. For those that are more.... challenged when it comes to skills, well..... keep reading.

As I mentioned in a previous post, my sensor died a week after Kyle, Cable & Wiring Guru for The Jackson Two, suffered an identical loss. Always willing to let him figure out the tough stuff first, I drove down to see how his relocation went. As we will see, it was a wasted trip, at least insofar as the wiring goes.

Performing the leak check:

Spoiler: it leaked. He had a small drip where the new fitting attaches to the threaded connector on the new sensor. A little bit more wrench fixed it right up.

I always like to go into Jackson proper for lunch at a great little place called Arch and Eddies. We got there before they were open, so I got a chance to visit one of our customers from the day job.

I was sorely tempted to buy some of the Crick-ettes, simply for the raw enjoyment to be had by pre-placing one somewhere in the break room at work and waiting for a co-worker to notice it, at which point I would casually just pick it up and eat it.

That plan fell through when I realized that I really didn't want to eat a cricket, no matter whether it came in a box as a "food product" or not.

I don't think I'm alone in that; I couldn't help but notice that they had plenty on hand. As in, all of them - not a single box sold.

When I got around to doing my own installation, I started by removing the big oil hose fitting that sits directly under the old oil pressure sensor to provide better access for wrenching it off of there. I figured there might be some oil in the line that would prefer to lubricate the hangar floor, so I used a food storage bag as a prophylactic:

The fitting that goes in where the old sensor was is one of those that go in with quite a bit of resistance and also tend to leak a bit. I learned with the brake fittings, which are very similar, that using a little thread sealant with a Teflon additive addresses both of those issues:

With the lubrication provided by the thread sealant, I got a nice, tight fit.

The new sensor does not come with the wire needed to attach it to the Skyview, but I figured I didn't need it - I would just cut the existing wire off of the old sensor.  With that done, the only meaningful purpose for the old sensor was to cut it open and see why something that simple costs over $400. After all, they're like $35 for a Lycoming engine.

Well, it all comes down to analog versus digital, it seems. The sender for my Lycoming was purely mechanical - all it had to do was deliver a variable resistance to a mechanical gauge. The Skyview, being nothing more or less than a digital computer, needs that analog signal converted to a digital representation, and that require some electronics. Not $400 worth, of course, but maybe $129 worth.

I went ahead and pulled the original wire back away from the engine. It was attached to the Skyview wires with a pair of terminals, which made it easy to remove it entirely. I propped the two Skyview wires against the engine mount to keep them from falling back into the bird's nest of wires down in that no man's land.

I pared back the insulation, then cut off the unneeded black wire.

This is a very important part of the instructions:

The sensor comes with a plug and two crimp-on terminal female pins. If you screw up attaching one of those pins, you're done until you can get replacements. If you crimp them on before pushing the wires through the holes in the plug, well, you're done for awhile.

You also want to be very careful to get the correct wires in the correct holes, for the exact same reason. With that in mind, I very, very, VERY carefully lined my wires up to match the drawing of the plug provided in the instructions:

I also bent the exposed wire double to make sure there was enough wire for the crimps to grab ahold of.

With that done, I fastened the new oil line to the fitting on the engine. I figured that oil might have trouble getting through the line if it had air in it, so I prepared the open end of the line to allow for a little overflow as I pumped oil into it.

I had decided that I did not want to drill a new hole in the firewall to mount the new Adel clamp, so I chose an existing bolt to use as the mounting location. The easiest place to put the new Adel appeared to be adjacent to the brake fluid reservoir. I routed the new oil line up and across the engine.

To pump oil into the new line, I just moved the prop the same way I would if I was trying to 'burp' the engine. After five or six rotations, I was surprised to see that I wasn't getting any oil at the end of the new oil line.  I went around to the other side of the engine to see what could be wrong.

Remember that I removed the input line and stuck it in a baggie?  You do? Well, you could have spoken up!

With the input line attached, it took just a few more turns of the prop to fill the new line.

It was a simple matter to remove one of the bolts from the brake fluid reservoir.

The additional thickness of the Adel clamp meant that I would need a longer bolt. This is why I keep bags of them handy.

It was just as easy to mount the Adel clamp and the sensor. You can see the fitting here that also benefited from some of the thread sealant - it's the white band between the hexagonal  top of the sensor and the new fitting.

Unfortunately, the new hose was about an inch too short to let the sensor sit vertically, but a little offset was enough to allow the attachment of the line and still provide enough slack to account for engine vibration and/or movement.

If you're wondering how much the engine moves, consider the other problem that I fixed while I had the cowlings off:

There was a pretty good gap there already, but clearly it wasn't enough. I used the ScotchBrite wheel to make more room.

With everything all plugged in and wired up, I cranked up the Skyview, only to be faced with a severe disappointment:

That big red X meant that I had gotten the wires reversed, despite my best effort.  How could that have happened??

Lets's look at that diagram again:

Oh, DUH!!!

The diagram obviously shows the wires going into the sensor itself, not the front of the plug as I had mistakenly assumed.

Given that I didn't want to cut off the terminal pins (remember: I had no replacements) to swap their locations in the plug, I reversed the wires with a pair of splices instead. That did the trick!

I ran the engine for a good five minutes during which the gauge held a steady 72 psi, and not a single drop of oil leaked from either of the new fittings.

I'm calling this one DONE!