Last Halloween my homebuilt, Melmoth 2, celebrated its fifth birthday-if age be counted not from conception (in which case it would not be five but 26) but from first flight, and if being an inanimate object parked in a hangar be called celebrating.
Melmoth 2 was not really finished in 2002, but what original-design homebuilt ever is? It was ready to fly. I have continued to work on it since then at a rate of 10 hours or so a week. I've made many changes, added a lot of weight-185 pounds and counting-and somewhat improved its performance. But there's still plenty to do.
Little has changed in the overall configuration. Other than a couple of air inlets and some minor fairings over the flap tracks and exhaust pipe-the latter intended less to reduce drag than to keep exhaust stains off the fuselage-the only change to the external aerodynamics has been the addition of upturned wingtips. I had built the wing without tips hoping to be able, if necessary, to tailor the dihedral effect-the ability to pick up a wing with rudder-after flight testing. As it turned out, an adjustment was necessary. The tips I added, with 45 degrees of sweep and 30 degrees of dihedral, brought the roll-yaw coupling into the acceptable range. These aren't winglets, by the way. It took me a while to get used to their look of having been added merely to comply with the dictates of fashion; I prefer the appearance of the more austere, clip-tipped wings of the 1950s.
Not surprisingly, the wingtips had no discernible effect on speed or rate of climb. The only change that has yielded a distinct speed increase so far was the addition of nosewheel doors. I had always intended to have them, but had been stalled by my inability to come up with a way to operate them with a mechanical linkage-bellcranks and pushrods being, obviously, morally purer than springs and cams. The mains are fully enclosed, and their doors open and shut under the control of a complicated but aesthetically rather satisfying (to me, at least) mechanical linkage. The problem with nosewheel doors in general is that they have to open very quickly when the gear is coming down and stay open very late when it's coming up, and wait around the rest of the time. It's hard to make a purely mechanical system that does nothing for a long time and then suddenly does a lot. Many nonhydraulic systems solve this problem by spring-loading the doors open and having the gear engage some sort of lever or stirrup on the way up, pulling the doors closed behind it. I finally gave up trying to figure out a prettier way and followed the crowd.
I had not considered the open well a big source of drag because I supposed that since it was a sealed cavity in a flat surface, air would just blow past it. Wrong: Closing the well reduced the total drag of the airplane by nearly 10 percent.
In the process of adding the wingtips I had to decide whether to provide access to the attachment of the pitot head, which was mounted on the end of the then-tipless left wing. I decided not to; why would I ever need to get at the pitot head?
Then last year, on the occasion of my biennial static/transponder check, the mechanic announced that he had discovered a leak in the pitot plumbing. I was surprised, since the plumbing consists almost entirely of lengths of aluminum tubing with epoxied aluminum sleeves at the joints. What could leak? Bowing, however, to authority, I went through the system, starting at the panel and working outward. I found nothing. Having finally arrived at the pitot head, I concluded that the leak must be there, securely buried inside the wing. I excised a hunk of the trailing edge, burrowed forward through the foam core, and finally extricated the pitot-only to find that it too was leak-free.
The leak, to make a long story short, turned out to be in the shop's testing equipment. But now I had cut up the pristine left wingtip, and so-in for a dime, in for a dollar-I sawed off its trailing edge, hinged it, and put a little servomotor into the cavity where I had excavated the foam. Thanks to the shop's leaky test equipment, I now have roll trim. It's not very powerful, but a single-engine plane shouldn't need powerful roll trim, and few have it at all. It's sufficient for trimming out fuel imbalances early in a flight; when the airplane is in balance an electronic timer, which switches tanks at seven-minute intervals, takes over.
Engine cooling gave me some trouble. At first, the oil temperature was high; flushing out the cooler, which, like the engine, had been sitting around for 20 years collecting varnish, fixed that. Cylinder head temperatures were uneven, with the right rear and left front cylinders running considerably hotter than the others. The engine, a 200 hp Continental TSIO-360, is obviously designed for downdraft cooling, and I was using updraft; but that did not explain the strange disparity in cylinder temperatures. For a long time I could not understand what it was about those two cylinders, located diagonally opposite one another, that made them hotter than the others.
