Aero Mail - 2010/05
Correction: AMA Indoor Nats dates
Gene Smith’s March 2010 FF sport column lists the dates of the AMA Indoor Nats as June 2–6. The event will actually take place from Wednesday, May 26 to Sunday, May 30. Our apologies for the error. —MA Staff
Skymasters and Honor Flight
Thanks for publishing the article “Skymasters and Southeastern Michigan Modelers Help Communities” (March 2010 “In the Air,” page 12). An error crept into the section on the Honor Flight. This was Chris Hass’s first Honor Flight but the 28th mission from Detroit.
Joe Hass Skymasters Member
A Satisfied Author
I was very, very surprised yesterday when a friend called to congratulate me on the ShyFox article (in the March MA). I assumed it had been “non-selected” for publication!
After getting over the shock, and struggling through the rest of the day at work, I rushed home to see if my copy had come in the mail. The USPS came through, so I settled in to see how it came out.
I was pleased that you managed to work with the plans; I had assumed that they would have to be inked to make them legible, but they held up pretty well after reduction. Don’t know how you did that!
I am old-school and like the look of hand-drawn plans and especially plans with lots of details to study. Modelers’ candy! The editing to condense the text was smooth and retained the flavor well.
The build photos came out fairly well, but I could have done better on the composition. Next time I will take more pictures so there are more to choose from. And yes, I need to figure out how to capture a racing plane in flight...
Thank you for the excellent presentation of the materials. I have already received messages from modelers who expressed interest in various features illustrated and in building the actual plane. This is a good way to keep control line racing alive.
Dave “McSlow” Hull Manhattan Beach, California
Full-Scale Unseen Forces
An article titled “Lifting Things With Unseen Forces” appeared in the January 2010 issue of Model Aviation. This brought to mind a flight in a full-size glider many years ago that might have been called Lifting Things With Seen Forces.
This was in conjunction with the burning of dead vegetation around a reservoir some seven or eight miles from our airport. The smoke could be seen rising almost vertically for several thousand feet, then flattening out at the top in the form of a long, shallow cumulus cloud that appeared to be continually building on the upwind side and decaying on the downwind. This looked like something interesting enough to be worth checking into.
I towed off in my old Midwest Utility glider behind an 85-hp J-3 Cub, released at 2,000 feet in fairly strong lift, and headed for the reservoir, working a few thermals along the way.
As I approached, it became clear that the smoke, rather than being a continuous flow, was instead showing a classic thermal pattern. First, a bubble would begin to form on the ground. As it grew, signs of internal bubbling and churning would become obvious, progressively increasing in intensity as the bubble expanded. Finally, upon reaching a certain size, this would break loose and rise in the form of a column, with the base remaining in contact with the ground as it continued to feed the ascending current.
As I flew into the first of these smoky thermals, lift was 800 feet per minute and I was able to climb to 5,600 feet before reaching cloud base. At that point I departed upwind for a breath of fresh air and to wait for the next thermal to form.
I watched from here as the bottom of the plainly visible column broke away from the ground and followed the rest of the thermal skyward. Within a few minutes, another bubble began to take shape, characterized by the same bubbling effect as before, and when it made its upward move, I returned to meet it.
This continued until around five o’clock when the fires died down, at which time I squeezed out every foot of altitude possible and headed back toward the airport. Thermals were no longer working this late in the day and, in the dead air, it was a long stretch for the slow Midwest with its less-than-impressive speed and L/D performance. Making it back to the airport was not a one-hundred-percent foregone conclusion, but a long, straight-in approach terminated with touchdown just past the runway threshold with all of ten feet to spare.
A theory some years ago stated as fact (based solely on observation of RC glider flights) that thermals were formed by three or four mini-thermals being born first and then joining together to form the main thermal. This was based on opinion rather than any sort of proof, and was probably the bubbling effect that I had observed rather than a multiple-baby-thermal hypothesis.
The "Unseen Forces" article mentioned thermals forming at night, and a later flight touched on this theory, although relating more to lift rather than to thermals per se.
After putting on a glider demonstration at an airport some 50 miles from home, I made a late-evening takeoff and towed back to our field, arriving at 2,000 feet and some 40 minutes after sunset.
The air was dead calm, warm, and unbelievably glassy smooth with not the slightest ripple to be felt anywhere. Upon releasing from the tow plane, I was surprised to find the rate of sink to be just half of what it was normally. Instead of the usual 250 fpm down, the variometer showed a descent of only 125 fpm, meaning that the overall air itself was rising at the rate of 125 fpm.
The condition prevailed evenly over the entire area and continued clear to the ground. I had no way of knowing how high it went and no individual thermal activity was present. This was apparently a case of the ground releasing heat that had accumulated during the day with the result being one huge area of lift many miles in scope.
It might be logical to assume that the condition could have been present even before sunset if the winds were completely calm and air temperature had dropped lower than that of the ground. Any horizontal air movement, though, even the slightest of zephyrs, might conceivably disrupt what appeared to possibly be a very fragile situation.
How this phenomenon could be used for model flying is unknown to me.
Al Cleave New Braunfels, Texas
Transcribed from original scans by AI. Minor OCR errors may remain.
