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[August 27, 2008]

After we collected our daughter from Williamstown, we had an unbelievable amount of baggage to contend with. It barely fit in Dave Noland's SUV -- crossover, actually -- and just about filled M2, behind the front seats, to eye level. The thing next to my right foot is a bathroom scale that I brought along from LA, anticipating something like this. Actually, the stuff added up to less than 250 pounds, so the weight was not a problem so much as the bulk. We landed at Taunton, MA, an airport with security arrangements that verge upon the paranoid, and, apart from a sightseeing trip out Cape Cod, M2 will remain there until we return to California in a couple of weeks. I used to skydive at Taunton when I was in college, and once came within five seconds of augering in when I somehow failed to locate my ripcord handle. I landed in a clearing among trees in somebody's yard, not far from the airport, feeling like one of those troops who hoped that the Normandy farmyard into which they descended did not belong to a flintlock-toting petainiste.

[August 17, 2008]

Not surprisingly, we left later on Wednesday than we had planned. We stopped for the night at Gallup instead of somewhere in Kansas, flew to eastern Indiana the next day, and arrived at Orange County (Montgomery, NY) at noon on Friday. Block performance did not match the spot numbers observed during local flights. In theory the plane gets 21 nmpg at 170 knots. In theory, you pick up an average 10 knots or so eastbound from the prevailing wind. But throw in a wind that perversely blew much of the time from the northeast and convective activity that had us at 2,000 agl a lot of the time, and we averaged 145 knots and 17.4 npmg. But the midwest is quite a bit more interesting from 2,000 feet than from 12,000, and the time passed quickly. Used one quart of oil and something like 127 gallons of fuel. The only thing, besides the wind, that didn't work perfectly was my David Clark headset, which began soaking my neck with silicon breast-implant goo somewhere in Nebraska.

[August 11, 2008]

We're leaving Wednesday for the east coast, and so today I was giving the plane a once-over that included draining the sumps. This is something I seldom do, because in almost six years I have never found any water or anything else in them, and the quick-drains have tiny O-rings that drip when little bits of dirt get stuck under them. Sure enough, the left one started to drip after I drained the sump -- nothing in it, as usual. Normally I can get it to stop dripping by letting a rapid stream of fuel flow through it -- I collect the precious stuff in a jar and pour it back into the tank -- but this time that didn't work, and so I had to remove the drain assembly from the airplane to clean the O-ring. This is a difficult and messy job that inevitably includes spilling a pint or so of fuel on the ground by way of my armpits. Eventually I got the drain out, however, and cleaned it. In the duct above it I discovered a little mass of trapped tank scum. On close examination it proved to include quite a variety of mysterious substances and, tragically, the corpses of two ants. Viz:

[August 9, 2008]

I was at Santa Rosa, north of San Francisco, yesterday and Thursday, being a judge in a contest run by the CAFE foundation as a part of a multi-year NASA-sponsored effort to improve the technology of general aviation airplanes. NASA is offering substantial cash prizes for the achievement of various goals. The ultimate target is a PAV -- personal aerial vehicle -- that is quiet, efficient, and capable of largely autonomous flight, including automatic navigation and landing. Originally this year's field was to consist of five competitors, but only three ended up participating: a Slovenian-born Pipistrel Virus (34-foot span version), an Urban Air Lambada, and a Flight Design CT, both of the latter built in the Czech Republic. All three are two-seat LSAs with Rotax engines, although the Virus had forfeited its LSA status by installing a variable-pitch propeller. The Lambada is a motorglider with a long, complicated wing; the Virus and CT are polliwog-shaped high-wing designs. The Virus is the more gracile of the two. The Lambada is an old-fashioned airplane, well-behaved in flight and gadget-free. It has the most unmistakeable aerodynamic buffet prior to the stall that I have ever seen; the entire airplane shakes violently, and the engine jumps up and down visibly in its mounts. The Pipistrel is loaded with high-tech equipment, including various electronic displays and an autopilot with altitude hold. It has camber-changing flaps and sailplane-type airbrakes, and a correspondingly varied set of cockpit controls. The CT is most like a conventional small trainer, with the expected controls and round instruments in the expected places. In the picture below, the airplanes (not counting the deceased Douglas in the background) are, left to right, the CT, the Pipistrel, and the Lambada, whose outer wing panels have been removed. The Lambada, which was still involved in some inflight data collection when the photo was taken, is carrying two temporary CAFE pitot-static booms under its wings.

I found the CT to be the least pleasant of the three in flight. I was surprised, in fact, that an airplane with its handling qualities could even come to market. It is directionally unstable; if you floor a rudder pedal the ball goes over the the edge of the inclinometer and just stays there; if you roll without rudder the effect is the same. I thought those flying qualities went out with the Fokker Triplane. It was also much slower, both climbing and cruising, than the Virus, which achieved a top speed of 163 mph in last year's competition; the CT's owner blamed its lethargy on an unhappy choice of a propeller for this contest.

I had a long conversation with Pipistrel's 24-year-old chief designer, who expounded some aerodynamic concepts I had never heard of. It struck me that in different cultures, different ideas are taken for granted, so that, for instance, all sorts of physical disorders are attributed in France to the liver, an organ that goes almost unnoticed in the US, except among drunks.

[August 2, 2008]

I completed the neutral-point hunt yesterday with a flight with 200 pounds of ballast, CG at 40%. The flight was unremarkable and the resulting data set fell nicely into line with previous ones. The stick-fixed NP is evidently at FS130, which is 60% of MAC, just as DWT said. I am setting the aft limit of the CG envelope at FS125, or 45% of MAC. I did discover that there is insufficient trim authority for fast cruise with aft CG. I am currently using only one of two trim tabs, and I expect that hooking up the other one will solve this problem.

[August 1, 2008]

On Tuesday I added another 50 pounds of ballast and did another stick force sweep, which confirmed the neutral point location finding from the first two. I plan to do one more today, with the CG at 40%. This is equivalent to four 170-pound occupants, 40 gallons of fuel and 50 pounds of baggage, and is the design aft limit. It provides a 7-inch static margin, which is pretty ample. In order to go farther aft, I would need to get more sand.

During Tuesday's flight the angle of attack indicator hung in the middle of the gauge. It turned out that the plastic face plate under the needle had cracked and sprung out sufficiently to interfere with the needle. I made a new face plate out of aluminum. It is somewhat crudely painted -- I never have the patience to do things like that well -- but it will serve. A remarkable thing was that when I called Safe Flight, the New York manufacturer of the device, to get some guidance about dismantling it, I talked with Joe Inserro, the same person I talked with when I first got the instrument 35 years ago.

[July 28, 2008]

I was looking through some old documents relating to the design of Melmoth 2 and I was surprised to find that some very early estimates of weight and drag were not too far from the truth. For example, a 1983 weight buildup arrived at an empty weight of 1,375 pounds. The actual weight at the first flight was 1,397. Since then quite a bit has been added, so I don't know how self-congratulatory I should be about the first estimate, but an undated, handwritten document that I think also dates from the 1980s has "Assuming We [ie empty weight] = 1600 lbs," which is not too far from the present value of 1,585. I also did a drag breakdown (handwritten, undated) that came up with an F of 2.5 square feet, which was almost exactly right if you made (as I did) the most pessimistic assumptions about laminar flow on the wings. The current estimate is about 2.3 sq ft.

A dot-matrix printout from an old longitudinal stability program I wrote puts the power-off neutral point at FS 124.11. That seems too far forward; Digital Wind Tunnel puts it at 129.97 or about .60 mac. Today I did a couple of flights to measure static longitudinal stability as a function of CG location. I first flew with a forward CG (113.43; .25 mac is 117.86, and mac is 35.26). I then loaded 100 pounds of sand (in bags) into the baggage compartment, which moved the CG to 118.40. (Actually, I added 10 gallons of fuel as well, but that has a relatively small effect on the CG location.) On both flights, I trimmed for 120 knots, then, without retrimming, accelerated to 160 and then slowed to 90, recording the stick forces required to maintain speeds at intervals of 10 or 20 knots. On the ground, I plotted the results and eyeballed a straight line through each series. Now, in principle I am measuring pounds of stick force per knot, but not having calibrated the Futek I'm just calling it millivolts (mV) per knot. The forward CG line has a slope of .27 mV/knot; the more aft one .19. I just about gasped when I extrapolated to the CG location at which the stick force slope would be zero, that is, the neutral point: 130.2. Given the many approximations involved in the test, that result is for all practical purposes identical to the one computed by Digital Wind Tunnel. It was interesting to see that although the airplane was obviously less stable with the ballast, it didn't feel subjectively worse; it still had good speed stability on final approach and felt normal throughout the speed range. Tomorrow I will add another 50 pounds and repeat the test.

[July 25, 2008]

I intended to make the first flight test with the stick force sensor, which I installed yesterday. But I got involved in plumbing the bubble catcher, and used up all my time on that. Here's the stick force thing:

I had to make the L-shaped adaptor between the bullet-shaped sensor, hereinafter "the Futek," and the sidestick mount. The red and blue wires coming out of it are for a press-to-talk switch. The two shielded conductors coming out of the Futek carry both the incoming excitation voltage, which I'm taking from the airplane's 12-volt bus (the airplane electrical system is 28 volt, but the Futek is limited to a maximum of 20 volts), and the output voltages, which are on the order of a few millivolts. One group is for the lateral axis, the other for the longitudinal. I tested it by lifting the weight of the elevator with the stick; it registered around 8 mv, and was quite well damped, so I think it should be possible to get good readings in flight. I have it hooked up to a $15 digital voltmeter that reads in increments of .1 mv, and I'm looking at the X axis, that is, pitch, only. Javier Arango, who will be the ultimate user of all this stuff, is ordering a data logger that will store continuous stick force information in two axes, as well as about ten other channels of data which we have yet to dream up (stick position would be an obvious candidate). Flight path and three-axis rate and acceleration information will be recorded by the Appareo gadget described on June 14.

Today's progress, such as it was, consisted of beginning to connect the lines between the synchronizer, the bubble catcher, and the hydraulic actuators for the flaps:

What you're seeing is the compartment beneath the back seats. The front of the airplane is to the left. The floor panels and the seats are supported by four carbon-fiber rails. Each aft-facing rear seat is located by several pins and locked down by a single bolt. The aluminum door in the middle of the floor will eventually have the oxygen outlets under it. The structure along the left side of the picture is the rear spar and main landing gear well; on the right edge are the tracks for the retractable boarding steps. About a third of the synchronizer plumbing is in place.

[July 17, 2008]

We got back from Cape Cod last night at midnight.

I flew a bit today, and thought a bit about what I need to do between now and a month from now when, if all goes according to plan, we will return to Cape Cod, this time in Melmoth 2. One big item is the leak in the right wing tank, which will require removing the wing. That's not a particularly difficult job, or at least it shouldn't be -- it's been on and off many times -- but I don't exactly look forward to doing it. It will pay some dividends, however, such as an opportunity to weigh a wing in its more or less completed form. That in turn will tell me the weight of the fuselage, and allow me to recalculate the actual factor of safety of the wings. It was 10 (ultimate) with two aboard when I designed the plane, but I underestimated the fuselage weight then. The reason for wanting to fix the wing tank leak now, rather than continue to let it go, is that it is located fairly high up in the tank and isn't a problem when there is less than 25 gallons (that is, 50 total) in it. That's fine for local flying, but for a cross-country trip I like to be able to carry 60 or 70 gallons (the total capacity is 142).

Another thing I want to get out of the way is the experimental determination of the neutral point. I described the procedure on June 14. Knowing the neutral point would help to determine the weight limit for rear seat passengers, among other things.

[June 18, 2008]

I finally got the bubble catchers assembled. Temperatures at the airport are forecast to be in the 97-109 range tomorrow and the next day, so I may not get this installed. Still in shock over the Lakers' total capitulation to the Celtics, I am going to Cape Cod to recuperate for three weeks -- plus my son is getting married there on July 12 -- and won't get the flaps moving on their own power until the latter part of July. Here's what the bubble machine looks like. Each tower is an inch in diameter and four inches tall.

[June 14, 2008]

As part of Javier Arango's project of collecting flight test data on his WWI airplanes, I ran some tests in my airplane with an Appareo GAU1000 flight data recorder which Javier had acquired. This is a little self-contained gadget about the size of a Rubik's cube. It costs $2,000, and performs what would have been considered miracles a decade or two ago, but are now merely routine digital tricks. Using GPS and solid-state gyros and accelerometers, it records location, speed, altitude, acceleration in three axes, pitch and roll rate, and so on. Display software allows you to replay your flight, a la Flight Simulator, but I find that aspect less interesting than the ability to measure a lot of variables like pitch attitude, roll rate, takeoff acceleration, and so on. One puzzling thing, however, is that the reported rates of climb are on the low side, not just in terms of my expectations but also in terms of the altitude changes and times recorded by the instrument itself. I suspect a programming error, but I have e-mailed the manufacturer to try to clear this up. The sevice samples its various parameters ten times a second, then smoothes and stores them at quarter-second intervals. Data can be downloded to Excel for futher manipulation. I expect to have a lot of fun with this (until Javier takes it back).

Another gadget Javier got, and which I am going to test first, is a stick force gauge. You can locate the neutral point with this thing by observing the stick force necessary to hold a speed 20 knots, say, below the trimmed speed, and then putting a couple of hundred pounds of sandbags in the baggage compartment and repeating the experiment. With an aft CG the stick force will be less, and a straight-line extrapolation through these two values to a stick force of zero gives you the CG location for zero longitudinal stability. Of course the thing that really matters is pilot comfort, and so the decision about how far forward of that point to put the aft limit of the CG range is a subjective one; but it will be interesting to compare the measured value with the one calculated by Digital Wind Tunnel. Likewise the phugoid period, which can be conveniently measured by the Appareo.

On Friday I picked up the bubble catchers from Flyte-Weld, and will start installing them on Monday, by which time I expect to have recovered from the depression and paralysis brought on by the collapse of the Lakers on Thursday.

[June 4, 2008]

Nancy and I went away for a week to stay with friends near Fort Bragg, on the Northern California coast. Their house overlooks the ocean and a rare (for the area) sandy beach, and we spent hours each day playing "beach boccie," which is a ballistic form of boccie ranging over both dry sand and smooth, wet -- but deceivingly undulant -- tidal flats. It was a lovely time, marred only by our having to drive ten hours each way because Los Angeles chose the day of our departure to undergo a freakish weather phenomenon preclusive of flight (at least for Nancy and me). It was interesting however, that the seats of my 12-year-old Geo Prizm were fidget-free for both long drives. I'm using those seats as models for my pilot's seat, but probably in vain because what matters is no doubt the depth and elasticity in a seat, not just its superficial shape, and those I cannot duplicate.

Today I finished making the parts for the bubble-catchers and took them down to Flyte-Weld, the welder near Burbank Airport whose work I was so pleased with a couple of years ago when I started this seemingly endless flap-actuation project. Chris Mogenson, the Hephaestos of this sooty forge, said he'd do the welding himself -- it's really a job shop whose welders do things by the hundreds, not four at a time -- but that it wouldn't be ready til late next week. I guess I need to find something else to occupy me in the meantime.

I've been having a hard time with the nylon tubing and fittings that I'm using. The description in the Aircraft Spruce catalog of how to assemble the stuff is pretty sketchy. To complicate matters, the 1/8-inch NPT threads on the nylon fittings are smaller than AN standard -- that is, they correspond to a portion of the tapered tap closer to its tip -- and they are really too small for a snug fit in holes that were tapped for AN pipe threads. Conversely, if you size a hole for the nylon fittings, you can't even start an AN fitting in it. I don't know whether an assembly lubricant should be used on the hose connections, or whether a thread sealing material, like teflon tape, or compound, like Tite-Seal, would be appropriate for the pipe threads. I have found nothing online. Of course, I'll figure it out eventually for myself, like most other things; but it's annoying to be so ignorant about such a commonplace product.

[May 20, 2008]

After trying to fill the synchronizer cylinders and lines without introducing any bubbles, I finally concluded that I need a bleeder in each of the four lines from the master cylinders to the actuators. Filling them is just too difficult and uncertain otherwise. These bleeders are actually air traps: vertical cylinders about 4 inches tall with a pressure-tight cap on the top. They're something like an inverted gascolator. Fluid enters and leaves at the bottom, but remains in the cylinder long enough for bubbles to collect at the top. I had one of these in Melmoth 1 and it worked fine. But this will delay the operation of the flaps for another couple of weeks, because I'm going to be away the week of May 23-30. Actually, even when the flap are operating they won't be working, because until I add the middle tracks they can't be used in flight.

[May 10, 2008]

The electrical connections for the flap are done. They were very simple, but some head-scratching was required to figure out how the flap and airbrake were wired, since I did not have a wiring dirgram for them. (Much of the plane has been built impromptu, without drawings, and although I always tell myself how important it is to document everything, I seldom get around to doing so.) I spent a while trying to puzzle out whether I had the flap valve rotating the right way; there was a 50-50 chance that I had it backward, and that the flap would go up when the handle went down. That would be easy to correct by simply swapping the cables at their connection points, but as far as I can tell from comparing the flap valve to the gear valve, I happened to get it right the first time.

I have worried quite a bit about the difficulty of bleeding the lines between the synchronizer and the flap actuators, but it occurred to me this morning that it is actually easy to purge air from the cylinders themselves, and the only bubbles that would be likely to be present would be in the lines. Since the internal cross-section of the smallest cylinder is some 30 times larger than that of the line, and since air does not compress to zero volume, even a four-inch-long void in a line would produce a shift of less than 1/8 of an inch in the position of the flap.

[May 7, 2008]

I had my first hydraulic flood today. The first of many, I'm sure. I was installing the flap actuating handle, and in the course of setting it up I cycled the flap control valve several times. The hydraulic pump wasn't running, but fluid ran from the reservoir to an open connection under the back seats, where the synchronizer is. By the time I noticed what had happened, the reservoir was practically empty, but the well under the seats wasn't.

The flap handle is now in place and working, except for the electrical connection, which I will do tomorrow. Like the gear and airbrake handles, the flap handle rotates a pulley which drives a two-way, center-closed valve, located under the passenger's seat, by means of a cable loop and a second pulley on the valve stem. The cable, which is about eight feet long, runs through flexible conduits. Those for the gear and airbrake are teflon-lined bicycle-brake cable housings; for the flaps I tried 3/16" nylon tubing, which is lighter and seems to work equally well. On the handle there is a cam that actuates the hydraulic pump by means of a single microswitch. The normal position of the handle is centered; to raise or lower the flaps, gear or brake you move the appropriate handle in the appropriate direction and hold it until the action is completed -- a matter of four or five seconds for the landing gear. You then return the handle to the central, valve-closed position. The hydraulic pump runs whenever the handle is out of center. I used this system because the more conventional one in Melmoth 1, which was also hydraulic but with electric rather than manual control, required a bunch of solenoid valves and microswitches and and quite a lot of plumbing and wiring. This one has no solenoid valves, three microswitches, and little plumbing or wiring.

The pictures below give some idea of how the system looks. The first one, below left, shows the flap handle mechanism not yet installed. The pulley, handle, and microswitch are visible, as are the cable, its nylon housings, and the barrel-and-set screw thing that keeps the cable from slipping on the pulley. The next picture shows the handle in place in the panel; the NACA 4415-shaped grip is removable so that the handle can pass through the slot. When it is in its center, neutral position, the handle rests in a detent. The handle, which slides in and out about 1/4-inch with respect to the pulley, is spring-loaded forward and must be pulled slightly aft to clear the detent before being raised or lowered.

The last picture shows the other end of the cable loop. This is the hydraulic jungle under the right front seat (it is also visible, viewed from below, in the entry for January 31, 2007). The gray thing, lower left, is the hydraulic pump, which came from a T-33. The flap valve is the thing with the large, thin hexagonal nut holding it to a green aluminum mount. The cable and its barrel lock are just visible to the left of the check valve with the stamped assembly date of 1966. I hope I can remain functional for as long.

[April 30, 2008]

Last week I got 15 feet of high pressure nylon tubing from Aircraft Spruce, but it turned out that I needed 16 feet. While waiting for the additional tubing to arrive, I took the partially-built flap handle out of the panel in order to complete it. The first problem was to figure out what I had had in mind when I made it, some time back in the 1980s. It gradually became apparent that there was supposed to be a limit sensor that would shut off the hydraulic pump when the flap was fully retracted. This is a feature that the other hydraulic services on the airplane -- landing gear retraction and air brake -- do not have. You just hold the handle in the up or down position until the cycle is complete -- you can tell by a change in the sound of the hydraulic pump -- and then restore it to its neutral center position. When I originally built this thing I didn't anticipate the self-bleeding feature of the hydraulic synchronizer, which requires that the pump continue to run briefly even after the flaps reach their fully retracted position. So I discarded some ingenious-looking little levers and springs and was able to carve away some portions of the handle structure -- saving, I'm sure, a number of grams -- and added a cam and microswitch to turn the motor on at any time the flap handle is not in the neutral position.

During periods of mental idleness I've been trying to figure out how best to fill all the flap-related lines and cylinders with hydraulic fluid without admitting too many bubbles and also without making a huge mess. It's not going to be easy.

[April 16, 2008]

Having fixed the leaky cylinder -- a pipe-thread poblem, as usual, solvable with Tite-Seal -- and hooked up the correct end of one actuating cylinder to a master, I confirmed that the travel ratio was precisely what I had calculated that it should be -- not surprisingly, the value of pi having been known with sufficient precision since at least the time of Archimedes. Next, I had to make internal stops to limit the travel of the master cylinders. I machined these today, and the cylinder travels are now within .003 or less of the intended values. So far, so good. Tomorrow I will epoxy the stops into the cylinders, reassemble them once and for all, and install them in the frame.

I had occasion to look at some old photographs of tuft tests of Melmoth 1's double-slotted flap. The quality of the flow attachment was astonishingly good. Here is a shot, taken some time in the 1970's with a camera mounted on the tail, just as I was about to touch down -- in other words, at close to the maximum lift coefficient.

[April 14, 2008]

Today for the first time I connected one of the master cylinders to some of the flap actuation cylinders (the purpose of the master-slave arrangement is to synchronize the four actuating cylinders). Hydraulic fluid is messy at first, like a baby. I found that one actuator cylinder leaked; I sprayed fluid all over the place when a hose connection that I hadn't sufficiently tightened popped off; and I attached the wrong side of the inboard actuator to the master cylinder -- I didn't realize this til I was driving home -- and so the travel measurements I took didn't mean anything. Tomorrow I'll repeat today's experiments, I hope with better results and less splatter.

[March 31, 2008]

I have been derelict. Our son and his fiancee visited from New York, Easter came and went, and there were various household and work duties to discharge -- in short, I have not progressed much. But I have at least installed a good deal of the under-floor plumbing for the flaps. For the first couple of days that I worked on that, I made no progress at all; mostly I just sat in the back of the plane staring at the empty space, shifting the synchronizer and the not-yet-installed oxygen bottle around to see how they would best fit, and trying to decide how to route tubing and locate connections so as to ensure accessibility and minimize the number of expensive fittings needed. It's somewhat like a jigsaw puzzle -- slow at first, but gradually gaining speed as more and more pieces fall into place.

Yesterday I had an e-mail exchange with George Braly of GAMI (the manufacturer of, among other things, injectors whose orifice diameters are tuned to each cylinder in order to ensure even mixture distribution) about the specific fuel consumption of my engine. The question arose because I was asked to repeat some of the windmilling glide tests I did a while ago and wrote about in Flying, and in order to draw conclusions from these tests it is necessary to know two basic parameters that govern the drag of the airplane. One is CDo, the parasite drag coefficient, and the other is e, the span efficiency factor, which is a correction applied to the geometric aspect ratio in calculating induced drag. I obtain e, which is 0.86, from computer analysis using Cmarc; CDo, which is harder to ascertain, comes from comparing measured performance with calculated performance. Performance calculations involve two semi-unknowns, propeller efficiency and specific fuel consumption. My performance calculation program, in Loftsman, uses mathematical models to approximate these parameters, which vary with speed, power, and various other conditions. I had obtained performance charts for my Hartzell propeller which indicated that its efficiency was higher than I thought -- I had assumed a peak of .86, but Hartzell claimed .89 -- and the question now was whether I could pin down sfc with equal precision (and credibility). The program was saying .44 to .45 lb/hp-hr at 55% power, and Braly thought that .44 was a plausible number. But in the course of the discussion he mentioned that the EGT at which best sfc is achieved gets closer to peak as power diminishes. In other words, one should run 75 degrees Fahrenheit LOP (that is, on the lean side of peak EGT) at 70 or 75% of power, but only 25 LOP at 55%. This was interesting to learn, though the actual impact of the information on fuel consumption is probably very slight. Braly also alluded to the well-known general principle that best efficiency is achieved at the lowest rpm and highest manifold pressure consistent with engine limitations; but the applicability of that rule is influenced by the propeller, which may become less efficient, not more, at a given true airspeed, as rpm drops. The loss of prop efficiency with diminishing rpm is very gradual, however, and so it may not really be a significant factor at all.

Unfortunately, the more optimistic view of the efficiency of the propeller, while in no way affecting the performance of the airplane, has obliged me to revise my estimate of its CDo from 0.0214 to 0.0222. How humiliating!

[March 11, 2008]

I finished riveting the flap synchronizer frames today -- my rivet gun couldn't manage the 3/16-inch AD rivets, but my 12-ton hydraulic press upset them nicely -- and was able to mock the thing up to better visualize the plumbing. It looks kind of cool, if you don't realize how stupid it is.

[March 9, 2008]

Although I can't operate my flaps yet, I can analyze them with CFD. Here are a couple of images of streamlines that I found very interesting. The first view, from above, shows the large amount of spanwise flow associated with the deflected flap, and particularly the vorticity generated at the flap root. The second view -- same streamlines -- is just to clarify the relationships in the first. Streamline colors correspond to pressure, and therefore inversely to velocity, with the red end of the spectrum being low pressure/high velocity, green neutral, and blue high pressure/low velocity. The green color of the model is arbitrary.

[March 7, 2008]

In the last three days I've flown twice to Mojave to look in on Ray Henning and his T-18, and once to Apple Valley to touch bases with John Roncz. Roncz had unexpectedly gone to Tehachapi, so I missed him, but the air was very smooth and so I was able to perform the test of cooling drag described on February 16. At 8,500 feet and my customary cruising fuel flow of 8 gph, which is about 55% power, opening the cowl flaps seemed to reduce indicated airspeed from 139 knots to 137. The two-knot difference corresponds to 0.1 sq. ft. of equivalent flat plate area, or about 5% of the total parasite drag.

I chased the T-18 for a while yesterday while Mike Melvill and Ray flew in the T-18. It climbs very well -- 1,500 fpm up to 8,000 feet at Mojave (field elevation 2,538) -- and the airspeed indicator matched mine, which is accurate, perfectly. Ray had earlier mentioned a high cruise of 168 mph indicated at 10,000 feet, which works out to over 200 mph. And he has not yet put the wheel pants on. He has the odd-looking Thorp pants, which cover only the inner half of the wheel; the stock joke about them is that they only slow the airplane down a little. Here's how it looked through my optically imperfect rear window; the dry lake is on Edwards AFB, and the snow-covered peak is 10,000-foot Mt. Baldy in the San Gabriels:

I'm getting close to assembling the flap synchronizer frames. They involve a great many parts that took forever to fit and drill, but I hope to rivet them Monday if I manage to alodine them over the weekend.

[February 24, 2008]

While I grimly revisit the Gestalt of metal airplane construction by drilling holes in what will be the frame supporting the flap synchronizer, others are more interestingly occupied. Last Tuesday Ray Henning trailered his blinding T-18 to Mojave, where Mike Melvill, never one to waste any time, helped put it together and then took it out for a test. The wind was gusting to 29 knots by the time he was on the runway, and besides the tailwheel steering was unacceptably sensitive, so he confined himself to a short lift-off. Yesterday, after replacing the tailwheel springs, Mike made a flight that was cut short after 15 minutes by the non-operation of the alternator and consequent loss of radio communication. Apart from the electrical problem, everything was good, including -- always importantly -- the stall.

I feel a bit envious, like someone who has college-age kids and whose friend has a new baby. Ray, I suspect, must be greatly relieved and impatient to fly the plane himself. He will have to be careful to avoid any heading that places the sun in a position in which it reflects into the cockpit from a wing. The joke going around Mojave is that the airplane took four years to build and 12 to polish.

[February 16, 2008]

Back home, and flew for a little while. I was looking for smooth air in which to perform a simple test. I was curious whether opening and closing the cowl flaps affects overall drag enough to have a noticeable effect on speed. I've never detected any, but I thought that perhaps a more sensitive test than indicated airspeed would be vertical speed. If I trimmed for level flight with the cowl flaps closed and then opened them, the plane would begin to descend if the drag increased. After repeating this test a few times, I ought to begin to get a consistent impression. Unfortunately, today was not the day. It was bumpy at all altitudes.

Costa Rica hands with birdwatching proclivities will marvel to learn that I took this picture within 12 hours of arriving in the country:

[February 6, 2008]

I'm going to Costa Rica fora weeka. M2 is staying here. No exciting updates til I return.

[January 29, 2008]

During a break in the rain late last week I flew seven touch-and-gos. I've never flown touch-and-gos in Melmoth 2 before, and they turned out to be instructive. I realized that because I usually approach the airport on a long straight-in from the northwest, I had grown accustomed to flying the VASI glide path from a couple of miles out. That was a mistake; it's way too shallow for my airplane or, I suspect, any light airplane. Besides, Whiteman has a telephone pole sticking up right at the end of runway 12, and even though I probably clear it by 30 feet I always feel as though it's about to gouge a hole in the underside of my wing. If you're on the VASI glideslope and miss the pole by a good margin, you have to drop down rapidly to land on the numbers and make the midfield turnoff -- which I seldom managed to do. Flying a series of circuits I realized that a steeper approach felt more comfortable, made for a more natural flare, and allowed me to touch down on the numbers.

For about a week I've been working up the courage to ask one of the local shops if I could use their shear and brake to make the channel elements for the flap synchronizer. A lot of shops, and individuals, don't like to let visitors use their equipment. Today I finally got up the courage to ask. I hadn't even finished the sentence when the mechanic said, "Sure, come on over, they're right there." I had all the parts made inside of an hour.

[January 22, 2008]

Today I found, in a nondescript metal building on San Fernando Road, just east of the old home of Industrial Metal Supply (where, between 1968 and 1973, I bought most of the metal for Melmoth 1), a sheet of .050 2024-T3, which I need for the synchronizer frame. It's become quite difficult to find aircraft alloys in small quanities -- "remnants", as they're called. Industrial, in a new and grander location a mile away, now carries only 6061-T6 and 5052. 5052 is too weak and soft to be of much use, but 6061-T6 is suitable for some applications and is weldable, unlike the stronger aircraft alloys 2024 and 7075. Burbank Metal Supply resembles the old Industrial in miniature, with stacks of miscellaneous materials, aluminum and stainless steel, some pristine, some scuffed and scratched, leaning against walls and stacked in racks. Irv Kaye, who walks very fast and has a somewhat scholarly air, was friendly and helpful, digging through piles of sheet until he found the one, two by three feet, that I needed. It cost $25 -- about eight times what it would have cost when I was building the first Melmoth.

Now I must find someone equally cooperative who will let me use a shear and brake to cut and bend the parts.

I should explain again what this synchronizer does. The flaps are hydraulically operated and are tapered, so the outboard actuators travel a shorter distance than the inboard ones. The job of the synchronizer is to apportion the flow of hydraulic fluid to the actuating cylinders in such a way as to keep the tips and roots in the proper relation to one another and to make sure the flaps move simultaneously. The four cylinders in the synchronizer do this by moving different amounts, kept in step with one another by the single bellcrank to which they are all attached.

Burt Rutan has repeatedly said that I don't need flaps -- his Catbird, an airplane similar to mine, doesn't have them -- and it's true that I have been flying for five years now without them and without missing them. But when I said a few days ago that this was a case of art for art's sake, I could have been speaking of any number of aspects of my airplane that are not really necessary -- or for that matter of the airplane itself.

[January 17, 2008]

Having assembled the cylinders and begun to mock up the flap synchronizer on a piece of tooling plate, I am beginning to feel that this is a case of art for art's sake, unjustifiable by any rational calculus balancing effort and reward. To say nothing of weight. But now that I am this far down the road, I may as well continue.

[January 5, 2008]

Yesterday I spent a couple of hours machining a few final pieces for the flap synchronizing system. One of the things I did was take a little material off each of four end caps for the cylinders. These are 3 inches in diameter, and I took away material to a depth of .140 in. over a width of about .6 in. It disappeared into a mess of chips and didn't look like much, but if you calculate the volume removed it turns out to be about a quarter-pound of aluminum. I guess that was worth 20 minutes. As someone in rehab from Christmas, I can testify that machining is faster than dieting. So those parts are at last done, and this afternoon I degreased, acid-etched, and alodined them in the kitchen sink.

[January 1, 2008]

Well, that's over.

Yesterday was the first time in a week that I've gotten out to the airport and either flown or worked on the plane. I did a little of each.

Nobody has ever asked what the Latin quotations on the home page and on the "Cooling" essay mean. But I'll explain anyway. The one on the home page, "album mutor in alitem..." is from an ode of Horace (Quintus Horatius Flaccus, 65 BC - 8 BC), in which he somewhat grotesquely imagines himself transformed by the fame of his poems into a far-flying bird; literally, it means "I am miraculously changed into a white bird, and light feathers sprout from my fingers and shoulders..." It gets weirder when his legs develop crusty chicken skin; but enough. On the "Cooling" page, the phrase is from the Transformations (usually called "Metamorphoses") of Ovid (Publius Ovidius Naso, 45 BC - 17 AD, a sexy old goat). Telling of the schemes of Dedalus for escaping from imprisonment on Crete, he wrote that the mythical tinkerer "sent out his mind into unknown arts," namely, flight -- sort of like me fumbling around with engine cooling, an art not called "baffling" for nothing.

It never ceases to amaze me that these 2,000-year-old texts come down to us intact.

[December 20, 2007]

Having leaned toward using composites for the supporting framework for the flap master cylinders, I leaned back toward aluminum after reflecting about just how, in detail, I would achieve the desired bearing strength at the cylinder pivots and compressive strength between them. It seemed as though it would be a comparatively complicated layup (two of them, in fact, since the apparatus is sandwiched between two frames, mirror images of one another), with very little weight saving, if any, over an aluminum trusswork of simple bent-up channels riveted to corner gussets of 1/8-inch plate. The corner gussets will be the bearers for the cylinder pivots and the central bellcrank (the "starwheel") to which they are all connected.

It was not until this afternoon, actually, that I ran through all the numbers to ascertain exactly what the stresses are. I am apparently of the "Build first, analyze later" school of design, like the people who did that bridge in Minneapolis. Actually, there were no surprises, since I had a good approximate idea of the forces involved just from mental calculations which I perform, in a fanciful effort to stave off Alzheimers, while falling asleep at night. The main piece of enlightenment that came out of today's more formal calculation was that it is not necessary to regulate the hydraulic pressure in the master cylinders to a lower level than that in the bleeder cylinder; all can run at 500 psi without inflicting excessive loads on the structure. I still need to machine five clevis fittings to join the the hydraulic cylinders to the starwheel, and then I believe it'll be O-ring and hydraulic fluid time.

My hangar neighbor Ray Henning, who has finally finished his T-18 (I think it's been about 30 years in the making), gave me some nylon tubing which will be an excellent, and economical, alternative to the many Aeroquip hoses I had stupidly intended to use.

It will be truly disheartening if this elaborate apparatus does not work as planned.

[December 9, 2007]

Yesterday Captain Tom Huff, the CO of the Naval Test Pilot School at Patuxent River, Maryland, stopped by on his way to the Air Force Test Pilot School graduation at Edwards, and we flew to Camarillo for lunch. I had him fly the plane on the way there, hoping for his assessment of it. Of course if he had thought it stank he probably would have been too polite to say so, but I got the impression that he liked it pretty well. For me, it was a pleasure to watch a skillful and precise professional pilot -- Huff is an F-18 guy, mainly, but he also flies a 210 -- fly my plane, after watching myself fly it for so long. I imagine that playwrights and composers seeing their work performed get a similar pleasure; another person brings something fresh to your perception of the familiar thing. Huff made a nice landing at Camarillo, and I made a rotten one at Whiteman, just to round out the experience.

I've been working steadily on the flap retraction system; the main thing that remains to be made, apart from the center tracks, is the frame that holds the four synchronising cylinders in the proper relation to one another. Originally I was planning to make it of .080 aluminum plate, but at some point it dawned on me that the loads between mounting pivots of the cylinders and that of the starwheel that keeps them in step with one another are compressive, and therefore need something with better column properties than thin plate to keep them in place. I kicked around various options and am currently planning on composite; it seems like the least expensive option, and the simplest to tool.

[November 28, 2007]

On September 17 I wrote about removing the fuel filter and finding in it a great deal of debris consisting, mostly, of bits of carbon fiber and light-colored grit that I think must be epoxy particles released by sanding. I discovered today, to my very great surprise, that by simply holding my Canon PowerShot A80 against the eyepiece of my microscope I can take a pretty good photomicrograph. Here are three shots, the first of the (almost) clean side of the filter, the second of the dirty side, and the third of some of the powder that I scraped off the filter surface. The carbon fragments are on average a couple of thousandths of an inch long.

[November 13, 2007]

I flew up to Paso Robles again, this time to talk with a machinist, Richard Galli, who is creating 10 reproduction LeRhone rotaries for Javier Arango. Everything on these engines is machined from huge hunks of solid steel billet -- no castings -- and Galli seems to me a genius with a mill and a lathe. I have no idea how he manages to make some of these parts -- which were originally made, however, in 1915, with machines much inferior to his but, he says, with no less precision in the final results.

The flights up and back -- about an hour each way -- were very smooth, with visibility unlimited and cloudless skies and an OAT of 9 degrees C at 12,000 feet. The autopilot and GPS tracker are working again; now I need to learn the millions of features of my old but highly serviceable Lowrance. So far, like, I suspect, many pilots, I have pretty much confined myself to the "GOTO" command. The other day I could have used the "runway extension" feature, which draws a line several miles out from the runway centerline. It was so murky in Los Angeles that I couldn't see Whiteman's VASI lights until I was inside two miles.

The plane seems to me to have slowed down a bit; I need to put it up on jacks and see whether the landing gear doors have gone out of adjustment. Then again, maybe the overall coating of dust and ash is disturbing the laminar flow.

[November 6, 2007]

I changed my oil today. It took three hours. Every time I do it I promise myself that I will come up with some kind of quick-drain to replace the stock drain plug; but I never get around to it. The problem is that there is very little room between the drain plug and the nose strut in its extended, and even less in its retracted, position. Getting at the plug to remove it is difficult, and made more so by the fact that the engine and the oil are hot. There are various kinds of quick-drains on the market, but even the "low profile" one in the Spruce catalog looks to me as if it takes up too much space. I need a drain that protrudes no more than 1/4 inch below the boss on the sump. I have an idea of how to make one, but as the misery of the oil change recedes in memory I will probably lose the impulse to do it, just as I have on every previous occasion.

[October 31, 2007]

Just got back from almost three weeks on the east coast, where, among more ordinary activities, I logged .7 in a Black Hawk at Pax River. Having been relieved of most of its military equipment, it climbed 3,000 fpm straight up.

By the way, the Peter Garrison who flew a Seneca into a building in Vancouver on October 19 was not I. I am not sure which of us was the real Peter Garrison, but in any case I am now the remaining Peter Garrison.

[October 5, 2007]

On Tuesday Russ Hardwick and I flew up to Paso Robles for lunch at Michael's, an airport restaurant of the better sort or, better, a restaurant of the better sort that happens to be located at an airport. We parked in front of the restaurant, alongside a handsome Lancair 360. After lunch we got into a conversation with the owner of the Lancair, who had bought it from someone who had had it built by a professional builder. "There are the people who like to build," the pilot declared, "and then there are the people who like to fly." Obviously, he preferred to fly and assumed that I preferred to build.

On the return, while descending into Whiteman, I throttled the engine back to idle and compared rates of descent with fine and coarse pitch. (The subject was on my mind because I had written in a couple of recent Aftermath columns that glide can be extended by putting the prop in coarse pitch.) Fine pitch, which causes the engine to turn at higher rpm and therefore absorbs more energy, yielded 1,200 fpm, against 1,000 fpm for coarse pitch. Now I am curious to know the zero-thrust sink rate; theoretically, it should be around 750 fpm under the same conditions. This figure, which emerges from my computer simulation, implies that the engine is absorbing about 15 horsepower when the propeller is in coarse pitch. I have a 1972 Lycoming report, Peformance Characteristics of the Continental IO-360-D Model Engine, which includes a plot of friction horsepower against rpm; it shows a nearly straight-line variation between 12 hp at 2,000 rpm and 28 hp at 2,800 rpm. (A close fit, if anyone cares, is 5.16x^2 - 4.27x.) I'm not sure whether this includes pumping losses, which could be at least partly eliminated on the test stand by plugging up the intakes and exhausts. I'm also not sure whether it's better to have the throttle open or closed in a power-off glide, or whether it even makes an appreciable difference. A vacuum cleaner runs faster with its intake plugged, but it's not a positive-displacement pump and so the analogy may not be a useful one.

To measure zero-thrust sink rates, I would have to put a microswitch on the engine block behind the propeller flange and detect the point at which the crankshaft, which has measurable end play, shifts from thrust to drag. Knowing the zero-thrust sink rate is one way to measure drag; the rate of sink represents the release of potential energy at a known rate, and can be translated into horsepower at least as reliably as fuel flow can.

Speaking of sink, I tried a lean climb on the trip to Paso. Rather than climb at 1,000 fpm at 28/2500 and 12 gph with a rich mixture, I set up 27/2400 and 8.4 gph at about 50 deg. F lean of peak, which gave 500 fpm. I later ran the math and found that the lean climb saves 0.2 gallons or, at current prices, about 90 cents; on the other hand, it takes about three minutes longer to cover the first 40 miles of the trip. Is my time worth 30 cents a minute? Depends whom you ask.

On Wednesday and Friday I worked at Homer Knapp's machine shop -- he is a motorcycle machinist and pilot whom I first met in the early 1970s in John Thorp's circle -- on the flap synchronization cylinders. They are now honed and the barrels and caps are threaded. There is still some machine work to do on the caps, but the honing and threading operations have loomed before me for years now and I'm glad to have them finally taken care of. Homer did the first three barrels and had me do the fourth, which I only slightly messed up. I did the inside threads on all four caps without ruining any of them -- a minor miracle.

On Thursday I bit the bullet and took my autopilot over to Mid-Continent Instrument at Van Nuys airport for repair; I also removed my quaint eight-day wind-up clock, which would run for barely eight minutes on a full winding. I thought it needed cleaning, and took it to the local watch repair place in Echo Park only to learn that the elderly horlogier had "passed." For the past two days, however, the clock has been ticking away merrily on my drafting table, evidently more at home there than in the airplane. Perhaps, like many people, it prefers lying on its back.

I got a message this afternoon that the autopilot is fixed and the bill is $185. Not bad for an airplane part. I can amortize it with 200 lean climbs.

[September 20, 2007]

I flew around for half an hour just to remind myself of where the buttons and knobs were. I was somewhere north of the San Fernando Valley, climbing through 6,000, scanning the sky like mad because this is the area through which flights inbound to Van Nuys and Burbank pass, when I briefly looked at the instruments and then looked out again to see a King Air passing in front of me a few hundred feet away. It was incredible that I could have failed to notice it moments earlier, since I was being quite conscientious about looking for traffic. It's difficult, after an experience like this, to have a lot of faith in "see and avoid." It also makes it seem particularly strange that Cessna's new light sport airplane, the 162, which is featured on the cover of Flying this month in a picture so murky that the airplane can barely be distinguished from the background, is a perfect clone of the 150, an airplane so notoriously difficult to see out of that its mere existence demonstrated the value of pure chance in avoiding midair collisions. Evidently the designers at Cessna, who should know, feel that visibility plays a relatively minor role in air safety.

[September 18, 2007]

I found the filter element at Kal Nelson's, or rather at K&P International, which has replaced Nelson's, the disappearance of latter enterprise being, as an employee of the new one said to me with a mysterious smirk, "a long story." After installing the new filter element, I cut the old one apart. It consists of 27 square inches of resin-coated paper. Under the microscope it is revealed to be a dense tangle of glossy orange fibers whose diameters are on the order of a few ten-thousandths of an inch. I found that the dirty side was loaded with a lot of debris but far from clogged. None of the long glass or carbon fibers had found their way to the clean side, but a few particles of amorphous whitish stuff resembling salt had, together with some very small fragments of carbon. Some of these, however, may have been transferred to the clean side by my less than professional handling of the sample. The filter seems on the whole to have been very effective. Possibly, however, it would be a hazard in freezing conditions if there were any water in the fuel. If the filter, which has no bypass, managed to become clogged with frost, it could shut down the engine. It would perhaps have been better to put it in the engine compartment, where it could have been kept warmer and would, besides, have been easier to get at.

The pictures below show the compartment that is below the pilot's thighs. The airbrake has been propped open to allow access to the compartment. The black object with the groove down the middle that runs across the top of both picures is the main spar. The filter housing is the bright aluminum thing on the left. Immediately to its right is the fuel shutoff, whose handle is on the other side of the bulkhead; to the right of that is the gascolator -- a genuine antique. Then comes a shaft that is part of the backup manual gear-lowering mechanism, and then, vanishing from the edge of the picture, is the electric boost pump. The next picture takes up where the first leaves off, with the electric boost pump (the red and maroon thing with the yellow label on the bottom); the two aluminum valves are fuel tank selectors, one controlling feed and the other return. They may be operated manually or electrically; the motor is the tan cylinder above the valves. The two springs are return springs for the airbrake, which is the black surface at the bottom of the picture; the cylinder that operates the airbrake is just above the springs. The back end of the hydraulic pump is at the extreme right.

There are some photographs of the other end of this action-packed compartment at January 31, 2007.

[September 17, 2007]

I have been making the fairings for the middle flap tracks at a relaxed pace, one a day. Today, having finished the fourth of six pieces, I thought I would go flying, but then decided first to drain the sumps and gascolator and check the fuel filter. The fuel tank sump drains disgorged, as usual, a few largeish grains of this or that -- you can never tell what the stuff is -- and no water whatever. They have never shown any water, although the tanks are never close to full; I suppose this is my reward for living in a dry climate. Often one or the other of them begins a slow drip after being drained, and it becomes a big production to get rid of whatever bit of smut is sticking to the tiny O-ring. This time that didn't happen, and I proceeded to the gascolator, which is located above the airbrake in the wing centersection. It always drains very slowly, yielding a deep blue liquid -- the dye in the avgas seems to collect here -- and a small amount of finely divided black grit that almost looks like some sort of melanoprotozoa when random turbulence -- or Brownian motion -- stirs it up. The gascolator, too, was kind enough to re-seal without starting to drip.

I then opened up the fuel filter, which, just between us, I have not looked into since 2002. The filter uses a pleated paper element, and there was quite a lot of scum in it; in fact, when I had mined most of the stuff out of the pleats it amounted to perhaps half a cubic centimeter of what appeared, once dry, to be a fine gray powder. Under a microscope, however, it revealed its true identity: a pick-up-sticks-like maze of black and transparent shafts of graphite and glass, mixed with clumps of shapeless light-tan debris which I take to be epoxy dust. Using as a gauge one of Nancy's hairs, which, by the way, was astonishingly clean and regular in shape, resembling an acrylic extrusion, and which I mic'd at .0017 inch, I estimate that the fibers are about two or three ten-thousandths of an inch in diameter. Most are three or four thousandths long, but a few are as long as .010 inch. I'm awfully glad I put in the filter; most airplanes don't have extremely fine fuel filters like this, but the debris the filter caught could have caused no end of trouble in the injectors.

I imagine that the filter element must be pretty well riddled with this gunk, and that I need to replace it rather than attempt to clean it. (It is customary, in any case, to replace paper filters and not to re-use them.) The element is a Purolator part, AN6237-1. I thought I had a couple of spares, but I could not locate them in the hangar. (Actually, it would have been miraculous if I had.) The local parts shop, Vista, didn't have one, but said they could get one by tomorrow. I decided instead to try my luck at Norton Sales, which has incredible amounts of incredible stuff, but, incredibly, didn't have this. I then thought I might find it online; all of the places offering it for sale, however, are electronics parts suppliers, so I'm afraid that if I order one I'll end up with a capacitor or something instead. Nothing at Aircraft Spruce. I'll try Luky's tomorrow -- the somewhat diminished avatar of the once magnificent Joe Factor Sales -- and then Kal Nelson; if those fail I'll be back at Vista, where I hope it doesn't turn out that they can't get them after all.

[September 8, 2007]

I revisited the stress analysis of my flaps more than three years ago (see March 11, 2004), and found that the loads that I assumed when I built them in the first place, some time well back in the twentieth century (why didn't I make my programs print the date on everything?), coincided closely with the new calculations -- showing, for one thing, that the old methods worked as well as the new ones, at least for this sort of rough analysis. But I have no records of what calculations I used to size the attachment points for the middle flap track. There are receptacles in the rear spar for four 1/4-inch bolts, two top and two bottom. The bolts are certainly adequate; but what provisions I made in the surrounding structure to spread the tensile and compressive loads, equal to the weight of a small car, into the skins and ribs, I don't know. I must have assumed, since I was completely absorbed in the design at the time, that I would never forget its details. Now, 15 years later, I have. I have lots of photographs of the wings under construction, but none of them shows how the lower attachment, the one in tension and the more critical of the two, connects to the ribs and skin, or what local reinforcements I may have added to the sandwich core, or whether I locally doubled or tripled the skins (as I should have). There are a few shots of the upper attachment, and I assume the lower ones were similar. In any case, they no longer seem to me adequate. This is a critical area, because a failure here would threaten the integrity of the aileron pushrods, and so I am having to redesign the attachments from scratch, more or less as though the original hard points did not exist. This should never have been necessary; one should document everything, either with drawings or photographs, no matter how unforgettable it seems.

My ancillary interest in Latin has drifted away from Vergil and, because my daughter will be reading Ulysses later this year and I am revisiting it after an absence of 45 years, alit upon a bit of ecclesiastical hocus-pocus to be intoned over the dying: liliata rutilantium te confessorum turma circumdet. This seems to me to mean "May a lily-bearing throng of blushing spirit-guides surround you." Perhaps some pilot-priest, if such there be, could set me straight about these inexplicably rosy-cheeked confessors. It is interesting to note, by the way, that the wish that follows this one is "iubilantium te virginum chorus excipiat" which means "May a chorus of rejoicing virgins receive you." Evidently, Muslims are not the only ones who expect to be greeted by virgins at the pearly gates. Seriously, however, it's quite obvious that the virgins here are symbols of angelic purity, and we may as well assume that their Islamic counterparts are as well, and not the frolicking lapdancers that many people seem to suppose.

[September 6, 2007]

Through good luck, it turns out that the fairings for the outboard flap tracks (see October 26 or December 4, 2006) will also work for the middle ones, and so I can re-use the original molds. This is the opposite of what usually happens, which is that I plan a part to serve several purposes and then find that it really won't serve any. Each fairing consists of three parts. It always feels as if it should be possible to make several at once, but today I managed just one. No hurry.

I have been thinking a lot lately about how to translate the famous line of Vergil, sunt lacrimae rerum et mentem mortalia tangunt. Taken in isolation it seems very beautiful and poignant and has a Japanese pity-of-things flavor, hardly the sort of thing you expect from pius Aeneas. In context I think the effect is much more mudane. But this matter is probably more suitable for some other website.

[August 29, 2007]

On the 22nd I had lunch with Mike and Sally Melvill at Mojave. In an effort to prevent the inside of the cockpit reaching the boiling point of plastic while the airplane was parked -- 20-knot winds made it impossible simply to leave the windows open -- I spread a white sheet over the seats and most of the floor. This seemed to help, although the Safe Flight angle of attack meter was still frozen when I took off -- heat has that effect on it -- and didn't begin indicating until ten minutes into the flight. It seems as though the cover ought to be on the outside, although it is awfully inconvenient to have to stretch a big canopy cover over the airplane in a stiff wind. I wonder how I dealt with this problem in the first Melmoth; I don't remember it being a big concern, other than the one time I burned my hands on the seatbelt buckle after parking in 114-degree temperatures at Palm Springs.

In the week since then I have not flown; I have been making a few final additions to the left flap, and next week will do the same to the right.

[August 16, 2007]

On the 14th I flew up to Oakland for lunch and returned in the afternoon. Southbound a little north of Gorman I had to get an IFR clearance to penetrate the smoke from a fire -- it is called the Zaca fire, I have since learned -- that I had somehow remained unaware of until that day, but that has been burning for a month in the mountains north of Santa Barbara and has consumed 84,000 acres. Just before I entered the opaque smoke, there was an extraordinary view to the west of a wedge of turquoise sky between layers of russet; unfortunately, I didn't have a camera with me to capture it.

During the flight I observed the continuous slight -- two or three amp -- charging of the battery that I have come to recognize as the sign of low battery water; I checked it yesterday and it was indeed low. This unexpected charging was a great and seemingly alarming puzzle a couple of years ago; now it's just a piece of routine service.

My progressive shaping of the seat back cushion is paying off; it seemed quite comfortable (but the flight, admittedly, was short -- less than two hours). Now I feel as if the seat bottom needs a deeper hollow for the buttocks, which will result in more thigh support. I'm taking off just a little at a time; I don't want to go too far.

[August 14, 2007]

Yesterday I had an opportunity to re-weigh the airplane. It has gained 180 pounds since its first flight, lord knows where, and now weighs about 1,575 empty. I have to say "about" because there was around 53 gallons of fuel aboard, and I have to say "around." The empty CG has also moved aft by more than an inch. The news from scales is seldom good. I was trying to comfort myself when I happened upon the specifications of a Cozy Mk IV, which supposedly weighs 1,000 pounds empty and cruises at 220 mph on a 180 hp Lycoming. That made me feel even worse.

[July 24, 2007]

While preflighting the plane on Friday I noticed what appeared to be a nut lying in one of the small drain holes that are supposed to let rainwater out of the cowling. Opening the side of the cowl, I discovered that the object was actually the head of a bolt. The nut was lying nearby. They had previously secured the turbocharger to a brace that is intended to keep it from vibrating fore and aft. I had just read a few days earlier that one should not use self-locking nuts in the engine compartment, and this seemed to bear out that rule. I replaced the bolt, whose threads were peened flat, with a new one of the drilled variety, and I replaced the self-locking nut with a castle nut and cotter pin.

I learned yesterday that Hans Georg Schmid had died in the crash of the Express 2000 in which he had intended to make two circumnavigations of the globe via meridians. He had just taken off from the airport at Basel, Switzerland, bound for Oshkosh, a 5,000-mile nonstop -- he loved long flights, and had circumnavigated the Earth before in a VariEze (or Long-EZ, I'm not sure which) -- when he either encountered downdrafts or could not develop full power, and struck the roof of a building a couple of miles from the runway.

I felt some connection to this project because my friend Hans Kandlbauer had been its chief engineer and aerodynamicist; I had also helped design the tip tanks. Although the airplane was very fully equipped (glass cockpit, etc) and loaded with 450 gallons of fuel, it had a 315-hp Lycoming and should have had a pretty reasonable rate of climb. For reasons that are not yet clear, Schmid, a retired Swiss Air Lines pilot with 16,000 hours, had elected to take off southward, with a light wind behind him and rising terrain and buildings ahead, whereas if he had taken off northward he would have been flying over flat and unpopulated terrain. The airplane was relatively unproven; it had just emerged from its 25-hour initial flight restriction, and this was, I believe, the first time it had flown with a full fuel load. Below, the airplane on its first flight, June 13, and Hans Georg in the shop in December, 2005.

[July 12, 2007]

It is often the case that, once the answer to a question is known, one is tempted to see whether one could have arrived at it analytically.

Theory of Wing Sections (p. 195) gives a CL increment of 0.6 for a 20-degree-deflected plain flap. Assuming that because of the dropoff in the spanwise lift distribution near the tip the effective CL is only a third of the theoretical value, that gives 0.2 * 1.2 * 205 * .87 * q for the maximum rolling moment, where 0.2 is the CL increment, 1.2 is the area of the flapped portion of the tip, 205 is the distance in inches from the centroid of lift of the tip to the CG, .87 is the cosine of the dihedral angle, and q is the dynamic pressure, which is roughly 16 lb/sq ft at 70 kias (rotation speed) and 64 lb/sq ft at 140 kias (typical cruising speed). The rolling moments from a fully-deflected trimmer run roughly from 700 lb-in at the lower speed to 2700 lb-in at the higher.

The next question is: How do those values compare in magnitude with possible fuel imbalances? Using Loftsman's tank analyzing routine, I obtained the weights and spanwise centroids of fuel loads from empty to full and made the following graph, which shows the incremental effect of each unbalanced gallon of fuel:

Each wing can hold about 70 gallons of fuel. As fuel is added the CG of the fuel moves outward, and the space occupied by added fuel moves outward as well. Consequently, the moment contributed by each additional gallon increases much more rapidly when the tanks are nearly full. At cruising speed and full tanks, the trimmer can neutralize an imbalance of 2700/1200 or around 2.3 gallons; with a more typical fuel load of 40 gallons, however, the figure is nearly 7 gallons.

Analysis by Cmarc, using the inviscid option (which is somewhat unconservative, that is, optimistic) and fully-deflected ailerons, gives a rolling moment at 70 kias (close to the flaps-up stalling speed) of about 45,000 lb-in -- obviously sufficient to counteract any probable fuel imbalance. But it is also obvious that the effect of the roll trimmer is very small compared with that of the ailerons, and that an aileron trim tab would have been a more powerful roll trimming device. Duh.

[July 11, 2007]

I finally test flew the roll trim flap. The good news is that there is no noticeable adverse yaw or side force from full deflection; the bad news is that there is not much rolling moment either. At approach speed you can barely tell whether the flap is deflected or not. At 140 kias the effect is much more marked, but by the time you've reached altitude and accelerated to cruising speed the fuel imbalance that the trim is supposed to compensate for will probably have burned off anyway.

The flap travel is about +-20 degrees. I was interested to see that with the flap going downward, separation occurs at or slightly before half travel. The rolling moment continues to increase, but probably at a lower rate that it would if the flow remained attached. The hinge is in the upper surface; the lower surface has a well-faired radius at the joint, and it is possible that the flow over it remains attached up to a larger deflection; but I can't see that side from the cockpit.

It remains only to paint the flap and forget about it.

[June 29, 2007]

A correspondent (Frank Shoemaker) inquired about the kind of analysis needed for a modification like the addition of the trim flap. Another (Paul Lipps) wrote to point out that a spring trim on the stick works just as well, and is simpler than an electrically operated flap. I concede Lipps' point without debate.

How much analysis I would do would depend on the type of movable surface I was adding. In this case, it is a trailing-edge flap attached to a MAC servo. The servo is a linear jackscrew, and so the flap is locked in position at all times and is not susceptible to flutter. (Even if it came loose from the servo, I think that it is too small and light, and the wing is too massive and stiff, for mutual excitation to occur. That is just an intuitive judgment, however. The flap might buzz, or even tear itself off the wing.)

As far as stress analysis is concerned, I never did any stress analysis of the upturned tips in the first place. I considered it self-evident, based on experience with foam-cored structures, that they would be strong enough. They have a spanwise ply of unidirectional carbon in both upper and lower surfaces as well as the two-ply 45-degree glass torsion box. I also figured that even if one failed it would not be a safety of flight issue. After building them I tried to bend one and found it to be sufficiently stiff that in my opinion air loads would not break it at up to 200 knots (Vne).

One can, however, do a back-of-an-envelope stress analysis. Dynamic pressure at 200 knots is 132 lb/sq ft. CFD analysis of the spanwise lift distribution suggests that the tips achieve only about 60% of the CLmax of the wing at their root (BL 200), tapering to zero at the tip. With the trim flap set 20 degrees down I would very conservatively assume an average CL of 1.0 for the tip, which has an area of 1.6 sq. ft. Because the tip tapers from a root chord of 21 inches to a tip chord of only six, I would put the spanwise centroid of pressure 5 inches from the inboard end of the tip. This works out to a compressive load in the skin at the root of 1.6 * 132 * 5 / 3 (3 is the section depth in inches), or around 330 pounds. This root moment can be simulated with a 20-pound force applied (by hand) to the tip of the structure. Of course the moment curve is different; a concentrated load at the tip puts an unrealistically large bending moment at mid-span. But in any case this is a limit-load test, not ultimate.

The flap itself, which is piano-hinged along its entire leading edge, undergoes only torsional loads, for which it is manifestly adequate. I added a strong rib to the inboard end, with a nutplate where the actuator attachment goes, and bagged a two-ply layup over it to ensure shear continuity between the end rb and the skin. There is no rib at the outboard end.

In the process of adding the trim mechanism, I hollowed out some of the foam core at the root of the left tip; also, making the trailing edge into a movable flap interrupted the torque box. To remedy these defects, I closed out the cove, added a glass shear web where the foam now ends, closed the nose of the flap, and placed a four-ply reinforcement in the unsupported portion of the upper skin, which, as a thin curved compression member, is the most critical element in bending. The reinforcement also serves as an anchoring surface for the servo motor. Most of these modifications are in the aft portion of the tip, however, whereas the principal load is carried by the fore portion, which remained unchanged.

When putting a flap on a swept panel, you always have to choose between aligning the end gaps with the airstream and making them more or less normal to the trailing edge. The latter option avoids interferences, but I find it aesthetically unacceptable, and so I opted for the former, with the result that the end gaps have to be larger than I would like.

[June 24, 2007]

Having hacked up the left winglet in pursuit of the nonexistent pitot leak, I decided that I may as well put in the roll trimmer. This involved cutting up the winglet even more, but by now I was hardened to it. I have a little trim motor that I bought in 1987, and have been storing since then in a cool dry place, for this very purpose. The trimming surface is a flap on the winglet. Because the winglet has a 30-degree dihedral angle, the trim surface will actually produce some lateral force that will have to be neutralized by the rudder. Probably it will be too small to notice, and in any case the point of the trimmer is just to reduce the stick force due to a temporary fuel imbalance at the beginning of a flight. Imbalances occur mainly when the plane has been parked for a long time on a slanted surface, or one main gear strut is less fully inflated than the other. It's just been a minor and occasional annoyance up to now, but I can imagine that with more fuel that I usually take on, and the center of gravity of the fuel consequently farther outboard, it could be quite a nuisance. On the other hand, when I get around to moving the aileron hinges aft in order to provide more aerodynamic balance and reduce their hinge moments, an asymmetrical fuel load may not be such a problem.

[June 14, 2007]

I finally got the pitot-static sign-off today. Adjusting the transponder was not excessively expensive. The funny thing was that when we repeated the pitot test the pressure still bled down. Then it finally occurred to me to ask the technician to remove his test attachment from my pitot tube and put his thumb over the end of it and repeat the test. It still bled down. So the leak was in their equipment, not in my system.

[June 12, 2007]

Wrong. That was not the leak. Today, at first, I concluded that the leak must be in the pitot head itself. I extracted it from the wing with some difficulty and submerged it in water while pressurizing it with my dental gadget. A stream of bubbles rose from what turned out to be a drain hole that was clogged with something or other. I cleared the hole, and then when I covered it the pitot head held pressure. But it now seems as if the whole system is holding pressure, so something I did at some point in the last two days, I don't know what, must have sealed the mysterious tiny leak, wherever it was.

The radio shop, of course, has not yet even looked at my transponder.

[June 11, 2007]

It was surprisingly difficult to locate the leak. I tried pressurizing the system and painting all the joints with soapy water, to no avail. I broke the plumbing down into segments and tested them one by one, using a dental syringe (quite a handy thing, actually; you're supposed to squirt between your teeth with it, I suppose, but it just happens to generate 200 knots in the ASI when fully compressed) and an inches-of-water gauge that I had forgotten I had, but found in a cabinet while looking for a second ASI. I sawed out a chunk of the trailing edge of the left tip and dug out the blue foam stuffing to uncover the short length of vinyl hose that runs from the pitot tube to the 3/16-inch aluminum tube that connects the wingtip to the instrument panel. I finally concluded that the slow leak was where the vinyl tube slipped over the copper tube sticking out of the pitot, which is the standard heated type. I hope I'm right; if it's not there, I have no idea where else it could be.

[June 10, 2007]

I took the plane to the local radio shop for the biennial pitot/static certification, which is required even for VFR flying here because Whiteman is within 30 nm of LAX. The first problem that arose was a leak -- slow, but not slow enough -- in the pitot plumbing; the second was that the transponder's pulse timing had drifted off and was outside the tolerances for the test (the end result being that it transmitted inaccurate altitudes, even though the encoder was generating accurate ones). The radio guy who I hope will be able to fix the transponder was away for the week, and so we borrowed an AT50A from another airplane and completed the altimeter and encoder checks, which were fine. I'll find out Tuesday about the transponder -- I have a bad feeling the guy is going to say, "Can't fix it, you'll have to buy a new one, but here, we have a great deal for you." Meanwhile, I've been trying to track down the pitot leak. I have a feeling that it's where the tip extensions attach to the wing, which is bad, because I was uncharacteristically reckless there and made no provision for getting access to the pitot tube. Now I'm going to have to cut some holes in the tip to get at the thing, but I guess I can view this as a divine nudge toward installing roll trim, which an airplane with full-span fuel tanks needs.

[June 3, 2007]

I made round trips to Mendocino and to Paso Robles in the past week. Nancy was with me on the Mendocino trip, and she didn't find her seat, which used to be the pilot's seat, overly comfortable. I didn't love the new pilot's seat either. I decided that one problem was that the seat back was not sufficiently concave (about an axis parallel to my backbone), and so support was mainly being provided to the center of my back. I ground some more concavity into the seat back after that trip. It felt better on the hangar floor, but on the next trip, an hour-long flight to PRB, I felt that my back was getting sore again. By this time I was starting to wonder whether the whole business was not just my imagination, but I tried putting a lumbar support, which I unzipped from a little seat-cushion-plus-lumbar thingum that I had from Oregon Aero, behind me. That immediately felt a great deal better, and seemed pretty comfortable for the return trip -- or at least it allowed me to feel that the locus of dissatisfaction was now the seat bottom rather than the back.

I used to get a sore back (and shoulders) playing the piano. I wonder whether it's really that certain activities, among them flying and piano playing (for me, at least, and possibly for those who heard me play), produce muscle tension that is absent when, say, I am sitting in a movie theater or in an easy chair reading a book. Or, more likely, I am simply getting older, and more prone to aches and pains. I don't remember the seat being a major source of concern when Nancy and I flew for 15 hours from Alaska to Japan in 1976; and Melmoth 1's seats were much cruder than Melmoth 2's.

The trip to PRB was for Chuck Wentworth's annual barbecue at Antique Aero. A whole slew of interesting airplanes showed up, including, among the military types, a Zero, a couple of P-40s, a Sea Fury, and the expected herd of Mustangs. Most of these were extremely spiffily painted and polished, but the one I liked best looked somewhat war-weary, its aluminum dull and its paint chipped. It looked like the real thing.

[May 23, 2007]

Russ Hardwick and I flew to Page, AZ on the 21st to visit a couple of slot canyons. I had been working for the past week on the duct that leads air from the flush scoop on the right hand side to the controllable ventilator (from an '89 Camry) for the back seats. The duct is a fairly elaborate thing with a diffuser about a foot and a half long (a diffuser is a gradually expanding duct, intended to reduce the velocity of air flowing through it without allowing the flow to separate from the tunnel walls). At the end of the diffuser is a flow reverser that turns the air about 150 degrees and feeds it into the ventilator, which faces forward because the seats face aft. The reverser even has a turning vane in it; it's all very fancy.

When Russ and I left for Page, I hadn't yet tested the ventilator in flight and I didn't know how much air would come out of it. I did know that there was no way for people in the front seats to adjust the ventilator, but I figured that it was a warm day in LA and it was warm in Page, and so it wouldn't be a problem if it were open.

It was already apparent when we were taxiing that the ventilator was doing a pretty good job. It really went to town after we took off, discharging torrents of air into the cabin. This was not too objectionable at first, but then we climbed higher and higher to stay above the inversion and the turbulence, and the outside air got colder and colder. The ventilator happened to be aimed right between the two front seats. My right shoulder and Russ's left froze until we let down at Page. It's remarkable that a NACA scoop more than ten feet back from the nose of the airplane, where the boundary layer must be pretty thick, and behind the point of maximum fuselage width, can still pull in so much air.

[May 9, 2007]

I flew to Santa Ynez for lunch. The air was extremely calm -- groundspeed exactly matched true airspeed -- and I got a good speed point. Speed takes a very long time to settle down -- several minutes. As I have often mentioned before, I determine drag area (or drag coefficient -- they amount to the same thing) by comparing observed performance with computed performance, using the performance prediction routine in my lofting program, Loftsman. The computer output is one or two decimal points more precise than in-flight observation; for example, when my fuel flow indicator flickers back and forth between 6.9 and 7.0, I call it 6.95, but it could be any number within two or three hundredths of that. Airspeed can be measured within maybe half a knot, assuming zero calibration error. Here is the Loftsman output for a weight of 1,900 pounds, a density altitude of 10,400 feet, and a power setting of 26 in Hg and 2,000 rpm. The collective EGT was about 60 degrees lean of peak. Indicated airspeed was 133 knots.

The items, from left to right, are true and indicated airspeed in knots, drag in pounds, thrust horsepower required (a function of speed and drag), estimated propeller efficiency (based on a highly generalized curve), brake horsepower required (which is thrust horsepower required divided by propeller efficiency), percent of rated power, ratio of parasite to induced drag, engine specific fuel consumption (again based on a generalized curve), fuel flow in gallons per hour, specific range (that is, nautical miles per gallon), and, finally, the "CAFE" product of true airspeed and miles per gallon. The highlighted line corresponds to yesterday's measurement.

The last item, which I call the CAFE product because it was the crux of the scoring formula for the old CAFE efficiency races, is related to the "Carson speed", the speed at which you get the "best" combination of speed and efficiency (as distinct from the L/D or best range speed, at which you get the best efficiency, regardless of speed). The best speed to fly, on this basis, would have been closer to 140 kias.

Cylinder head temperatures, with the cowl flaps closed, were:

1. 175 C.
2. 170
3. 170
4. 170
5. 150
6. 180

On the return trip I used a slightly higher power setting (26.7/2,200, fuel flow 7.8 gph) and saw a somewhat different temperature distribution:

1. 185
2. 160
3. 180
4. 175
5. 150
6. 190

So the general pattern is: #1 and #6 are warmest, #5 (not #2, as I always thought) is coolest, and the others are somewhere in between. The previously observed coolestness of #2 correlated well with its being the first cylinder to reach peak EGT; it was therefore running leaner, and hence cooler, than the others. The present observation does not correlate with anything in particular, but suggests that the earlier pattern was just a coincidence. At this point the cooling is sufficiently well-behaved that I think I will just stop paying attention to it.

[May 8, 2007]

I realized yesterday that for years I have been referring to the left front cylinder as #5. It is #6. I went back and corrected the error all through this narrative (I hope).

What else have I been doing wrong for years?

Cylinders on my engine are numbered from back to front, with odd numbers on the right because the cylinders are staggered with the right side farther aft. (Multiple engines, on the other hand, when they are on the wings, are numbered from left to right, like freeway lanes.) My engine's oil cooler is mounted on the crankcase directly behind the #2 (left rear) cylinder.

The reason the lack of finning on the exhaust port surface is not a problem with downdraft cooling, I think, is that air emerges from the baffle passages at high velocity, and so heated air is continually scavenged from the unfinned surface. When the flow is going in the other direction, however, air converges into the baffle passages from a wide range of angles, and does not pick up a lot of speed until it enters the baffles. The revised baffle provides a converging channel over the exhaust port, and also adds baffling that wraps around the undersides of the cylinder, increasing the velocity of airflow there.

[May 5, 2007]

Success again. I redid the baffles on the right rear cylinder (which modification took three days rather than the expected one) and pulled its temps down by 50 degrees F or so as well.

Yesterday was a peculiar-looking day, with a shelf of dense clouds over the San Fernando Valley but lots of clear areas to the west. I started a 1,000-fpm climb westward once I was out from under Burbank's Class C. The CHTs were running around 150 C with the cowl flaps fully open. I closed down the aft vents to half an inch or so and went up to 10,500 feet without the hottest cylinders getting above 200 C. The target (ie factory recommended) temperature is 370 F or about 185-190 C. Continuing westward, I set up 27/2300, or around 55% (8.2 gph). With the cowl flaps closed as far as they would go (1/4-inch gap at the aft ends) the temps settled at around 150-175 C. (Different cylinders are still at different temperatures.) The oil temperature is still a rather high 97 C.

Incidentally, the reason I keep bouncing back and forth between Celsius and Fahrenheit is that my CHT gauge is calibrated in Celsius, while Continental's documentation is in Fahrenheit.

The #2 cylinder, the one next to the oil cooler, is still the coldest, and #1 and #6 are still the hottest, , but the disparities are much reduced. I guess that further tinkering with the baffling could bring the CHTs still closer to one another, but I'm not sure it would matter.

After pointing westward for a while I checked the GPS groundspeed and found that I was doing 90 knots. So I turned around, and then I was doing 220. Too bad I wasn't going to Arizona.

[April 27, 2007]

Success. The revised baffling on left front cylinder brought the temperature down by about 50 deg. F; it is now in line, +-20 degrees, with all the other cylinders save one, the right rear, to which I should be able to apply the same treatment next week. The problem with the cylinder is that it has no finning to speak of in the vicinity of the exhaust port:

My baffles previously ended even with the centerline of the cylinder; the trouble with that arrangement, as I now see it, was that it did not provde enough air velocity, and therefore heat transport, on the lower half of the cylinder. I modified the baffles by extending them down around the bottom of the barrel and the inboard part of the head, and providing a barrier about 3/4 of an inch away from the finless portion of the casting around the exhaust port. The revised baffle looks like this:

The way in which the baffle, which is lying down on my junkheap of a work table with its lower edge to the right, matches the cylinder should be fairly clear. I'm sure that still more improvement is possible -- the barrier near the exhaust port is pretty crude -- but this went a long way. Here's the way it looks installed:

[April 24, 2007]

It finally occurred to me -- showing that if I think about something long enough, even the most obvious fact about it will eventually become apparent -- that what my two hottest cylinders, the left front and right rear, have in common with one another is that their exhaust ports are not next to another cylinder. The suggestion is that whatever flow guidance is provided by a neighboring cylinder for cooling air passing by the exposed side of the port, which has practically no finning, is not being provided by my baffles. This clue at least gives me something to work with.

I should have the flap actuator plumbing finished by the end of this week and be able to resume working on the synchronising cylinders. It's increasingly clear that I won't have the flaps working by Oshkosh -- my somewhat arbitrary target -- unless some phase of the project proves less, rather than more, time-consuming than expected. That would be unprecedented, however. Well, maybe they'll be working -- but only on the ground.

[April 17, 2007]

The NACA scoop for back seat ventilation works nicely. I tufted the inside of the fuselage behind it, and the tufts were straight and steady in flight, indicating a strong flow with little turbulence. What I want to do now is diffuse it over a distance of about two feet and turn it around 180 degrees toward the back seats (which face aft). I sat in the new pilot's seat for this flight; it's not right yet. More foam grinding ahead. Cruised around for half an hour making squiggles on the GPS map. 137 kias at 7,500 ft DA, 7.6 gph -- a bit below par. It's interesting to note that opening the cowl flaps about 1/2 inch pulls CHTs down by 40 deg F, but does not have a measurable effect on speed. Tomorrow I think I'll wash the plane -- it's embarrassingly dusty -- and then get back to the flap hydraulics.

[April 13, 2007]

Two weeks later and I'm still installing hydraulic lines. It's weirdly time-consuming, to say nothing of expensive (AN and Aeroquip fittings are not being given away these days, unfortunately), but I'm getting there. I took a short detour this past week to cut a Concorde-shaped hole in the right side of the fuselage for an air vent for the back seats. I haven't flown yet to see whether any air actually comes in through it. It's one of those flush NASA affairs, and it's hard to understand how it can work very well once the boundary layer has grown to a depth that's comparable to that of the inlet channel. I'll test it on Monday.

I've also been grinding away at the foam on the pilot's seat and then sitting on it for a minute or two to see how it feels. It's hard to judge; even park benches feel comfortable at first.

[March 31, 2007]

Something about me seems to be extremely irritating to upholsterers. On Friday I was shown the door by the second one. I was not heartbroken; he seemed to me to be even less conscientious and competent than the first, who was no great shakes. But at least I ended up with a bunch of foam, glued rather haphazardly to the seat frame, at no charge. It's just as well that he decided to kick me out before he covered the seats, because the way he had shaped the foam was not very comfortable anyway. I'm going to try my hand at it, imitating the seats in my Geo Prism, which seem fairly comfortable.

In the meanwhile I've been adding the plumbing to deliver hydraulic fluid to the outboard flap actuators, and thinking a lot about an alternative cooling air intake configuration that might make it easier to equalize temperature among the cylinders. Just thinking; there are plenty of other things to work on first. But it's something to do while going to sleep.

Here's the environment of the outboard actuator:

The flap has been lowered to reveal the cove just inboard of the aileron; the latter can be seen, deflected upward, in the lower right corner. The diagonal pushrod is the aileron actuator, supported, in the upper left corner, by one of several idlers. An inspection plate has been removed, revealing the outboard fuel quantity sender (partially in shadow) and an aluminum block (bottom center) with blue fittings protruding from its top and bottom. The purpose of the block is to provide an anchor for the ends of flexible hoses going to the actuator, which will be installed just outboard of the aluminum flap track, between it and the fuel quantity transmitter. The paired lines, which run about ten feet inboard to the fuselage, are what I've been installing; they are 3/16 inch in diameter, and are secured to the upper surface of the cover at 15-inch intervals by tiny phenolic pillow-blocks.

[March 14, 2007]

I flew for half an hour to test the effect of the exhaust pipe insulation on the temperature of the left front (#6) cylinder head. It went up. This was not entirely unexpected; the exhaust pipe is in intimate contact with the cylinder head, and if stays hotter because of the insulation, some of that heat would migrate into the head. It was a question of whether the benefit of not preheating the air approaching the cylinder baffles would outweigh the ill effect of keeping the pipe hotter. It didn't.

A speed point -- density altitude 10,000 ft., weight 1950 lbs, fuel flow 7.5 gph, IAS 138.5 kts -- confirms once again the value of 2.25 sq. ft. for F.

I took my pilot's seat to the tapiceria -- upholstery shop -- across the street from Whiteman for an estimate. The amiable and copiously tatooed owner said it would be around $200 to do the second one -- $150 labor and $45 for the foam. I already have the covering material from my unhappy episode with the uphostery guy on the airport, who wanted half again as much money for the same job and then did it badly.

[March 12, 2007]

It was 90 degrees today, but there was a good breeze at the airport and for some reason the metal hangar does not become unbearable on hot days. Neddy, my large, long-haired and black dog, seemed pretty comfortable sprawled on the asphalt. I did some laminating in the back of the plane and noticed that for the first time this year I had to take care not to drip sweat on the epoxy-soaked glass cloth. The anchorages for the inboard flap actuators are now in place, and I have nearly finished making the hard points that will be secured near the outboard ends of the flaps to anchor the flexible hoses going to the actuators. Once those are in place, I will be able to plumb the hydraulic lines from the fuselage to the outboard actuators, and then get on with the synchronizer. On Friday, tired of fiddling with the flaps, I wrapped the exhaust pipe below the left front cylinder with insulating stuff, but I have not yet flown the plane to determine whether the proximity of the pipe is actually the reason for that cylinder running hotter than its neighbors.

[February 28, 2007]

I spent a jolly hour or two on my knees in the back of the plane, sanding out clearance for the flap actuator, which passes though a couple of bulkheads in a very confined space. At first I tried to do it with files, rasps and sandpaper, and I reminded myself of those patient prisoners who break out by filing their way though steel bars with dental floss dipped in floor dust. I then had the inspiration to saw a slot in a piece of 3/8" aluminum rod and slip the end of a 20-year-old, and hence tightly curled-up, piece of 40-grip Norton abrasive cloth in it. This, chucked in an electric drill, cut through fiberglass and plywood beautifully. At the end of an unusually long afternoon I had the left actuator working without interference though its entire travel. The right one will be easier because now I know what needs to be done, but harder because I'm right handed, and it's on the wrong side for holding a drill motor while hunched up on my knees.

[February 27, 2007]

I went to get some O-rings at A.C. DePuydt, Inc. I love that place. It's located in an LA suburb with the arresting name of Commerce. You go to the Will Call counter with your tiny order for a dozen rings. They always have what you want, even weird sizes without AN or MIL numbers, and after they're pulled it from inventory they send you around to the cashier, who is always charming, and in no time the invoice has been typed up and you're out the door with a little brown paper bag in your hand. This time the bill was $5.14. I think they have a $5 minimum; they give you extra O-rings to fill in the gap. I took them to the hangar, where a bunch of hydraulic cylinder parts that I'd made over the past couple of weeks were waiting for them.

I started to assemble the four hydraulic cylinders that will operate the flaps. I found that the silver-soldered joints between the shafts and the pistons for the outboard cylinders were leaky -- I submerged them in water and applied compressed air to the hollow shafts -- and I'll need to put some epoxy inside. On the inboard cylinders I had threaded the shafts and the pistons and used penetrating threadlocker,