If the judges were managing to be completely objective, retracts would only make a difference in as much as they affect the aerodynamics of flight (and if they make it worse -- oops). I suspect that if you get any points from the "wow" factor, it'll wear off as the judges get used to seeing the wheels go up.
I'm sure you're already thinking about this, but it sure seems that you'd want to think carefully about when you want the gear to go up. Too soon and the "wow" factor is of entirely the wrong kind. Too late and you don't get nearly as much "wow" as you'd like. Just right, from a purely aesthetic point of view, would be to start a slow retract right as the wheels leave the ground -- but that really flirts with 'too soon' if anything delays takeoff.
I'd be concerned with the retracts messing up the airflow when I'm trying to achieve a smooth takeoff and level flight (actually, I'm a rank beginner -- I can't reliably achieve level flight yet, so retracts would just give me something to blame other than myself). At worst, you could time things so that the wheels went up after your two laps of level flight, but that would certainly remove a lot of the "wow". At best, any bobbles from the wheels going up would be slow, and could be timed for the climb phase of the takeoff where they'd hopefully get subsumed in the overall climb.
Hi Tim:
My little poem was meant as humor, not as a prediction as to what the judges might like. I've been competing in this event for more than 45 years and well know how judges think. I've judged more than 10 Nats and/or FAI Team Trials as well, so I'm familiar with what judges think from that perspective as well. Judges are impressionable, just like anyone else, but there is no telling just what might impress them... I'm doing the twin for personal reasons and because I believe that it may offer many distinct advantages from a flying perspective. That may yield a better pattern, and I do think that judges might be impressed by that.
I've been toying with the idea of retracts since 1976. I actually started building my Nats ship (The Genesis 46 Mk III that ultimately did win that Nats...) with retracts. My father, James A. Hunt, voiced some of the same concerns that you mentioned. I've recently been working on a book about the Genesis series of airplanes and that story is included in the text of that book. Instead of retyping it here, I'll just drop that segment in here now:
Excerpt from Genesis book:
The really great thing about CL Stunt is that there is always a next season. The great thing about CL Stunt people is that they are always willing to give you another chance. The really great thing about a bad plane is the fact that you can build a new, better one!
And that's just what I did. Over the winter of 1975-’76 I evaluated my entire program and decided that my basic design airplane was good. I just needed to execute every aspect of the program with more thought, energy, commitment and enthusiasm. The enthusiasm part almost got out of control…
I decided to make a real statement and put retractable landing gear in my 1976 Genesis 46 Mk III. This decision was made after talking with my father about practical methods of triggering the retraction and extension of the gear in a two-wire CL system. We discussed some pretty wild and outlandish systems, but then he hit on one that really sounded doable.
Dad told me about bi-metal switches. The idea was to use a bi-metal switch that would be located in the muffler (remember, this was way before we had tuned pipes…). As soon as the engine was started the bi-metal switch would separate or close, depending on how it was setup, and the signal would be given to a servo to retract the landing gear. Of course we would need a delay in the system to allow the model to become airborne before the retraction process would begin and he suggested a simple pullout Free Flight type timer switch to do this. So, all the pilot would have to do is signal the holder to start the timer and launch the plane. When the FF timer bottomed, the circuit to the servo would be completed and the gear would go up. At the end of the flight the engine would shut off and hence the heat source that was keeping the bi-metal switch closed would be gone, and the bi-metal would click in the other direction, reversing the circuit and extending the gear. I know, it sounded a bit complicated to me at first too, but I soon bought into the concept when my father demonstrated how quickly a bi-metal set would heat up and trigger and how fast it would reverse when the heat was removed. I was sold!
Dad even designed our own retractable landing gear units. They were based on very light aluminum frames and a simple but positive toggle lock system. This was used to insure they would not try to extend during flight do to “G” loads.
I went to work making a foam wing core for the new Genesis and devised an accurate mounting system in which I installed 1/8-inch thick Lite-Ply half ribs from the leading edge back to the full-depth spar at the high point of the wing. These ribs had a “land” cut into them to accept a landing gear mount plate. The thought was to capture the retractable landing gear units in a strong structure. Up to that point we had all been gluing a section of the front core piece back into the wing and simply sinking a landing gear block into that piece of foam with a lot of epoxy to hold it in place. That system was heavy, weak and messy. I wanted something that was strong, simple, light, accurate and easy to repeat. That was the first use of the landing gear mounting system that became the norm in the following years for use in foam core CL wings by all of the manufacturers in the United States.
In those days I was covering my wing cores with .045 (3/64) balsa sheeting. I had saved some very light sheeting for this ship and it paid off; it was an extremely light wing! I also continued the use of foam flaps that were cut as a one piece unit with the foam wing core and then covered along with the wing core. Of course the actual sheeting that was used on the flap had the grain running parallel to the leading edge of the flap. The wing’s sheeting ran parallel to the leading edge of the wing core.
I had the wing complete and ready to install in the fuselage when someone asked me if there would be enough drag with the landing gear retracted to prevent the model from “whipping up.” I hadn’t even given that any thought. I decided to take the landing gear out of the 1975 Genesis 46 MkII and have my dad hand-launch it over some lush grass at the field so that when I landed it there would be no chance of scratching the finish.
Well, the first thing I noticed when the plane was airborne was that it flew as if it weighed many ounces less than it actually did. I had felt this to a point years earlier when I flew profile models with the gear off, but this larger ship without the gear was an eyeopening experience. It also turned absolutely equally in both directions and was much easier to transition in the intersections of the figure eight maneuvers. Over all it just flew much, much better than it did with the normal landing gear attached. I was giddy; right up to the point when we flew it in some significant wind without the landing gear. Then the model demonstrated a lot of acceleration in maneuvers. And, that was the deciding factor in scraping the idea of retractable landing gear until we could come up with a method of keeping the model from speeding up when the gear is up. Oh well…
But wait; the wing had already been made to accept the retract units! That’s when I came up with the landing gear plate system that I’m still using to this day in my personal wings and in the wings I produce commercially. The old system had the groove for the landing gear wire exposed along the exterior of the wing, more or less like the systems seen in RC sport planes. The torsion portion of the wire ran in the exposed groove and then bent upwards into the wing where it was anchored in a maple “spur” block. A pair of metal or nylon straps held the wire in place in the grooved block. The new rib system allowed me to install a recessed plate that had a groove running down its center. The same type of anchor spur block was used, but now it could be designed to not only sit atop the plate, but also butt up against the Lite-Ply rib, giving it a tremendous amount of strength with even less weight than with the old system. An added benefit was that now I could craft a form-fitting cover plate and make the entire system virtually invisible. It was lighter, stronger, and more attractive than the old way of doing it. And, it was actually discovered/developed by accident! That’s what I call serendipity. (end)
I hope the above story was entertaining and even instructional about how much thought and research go into new technologies.
Later - Bob Hunt
Topic: New Electric Twin project back on track (Read 116274 times)
