stunthanger.com
Design => Stunt design => Topic started by: Kim Mortimore on June 24, 2013, 10:20:41 PM
-
...continuing from Strange airfoil:
However, I do enjoy intentional experiments very much, and I came up with what I hope will be a good one, better than the shelf idea. I'll open a new topic for it.
Speaking of intentional experiments, flight trimming a plane seems to me like a series of small experiments. Earlier this year I trimmed an Imitation, and found the experience both educational and highly rewarding. It's the most advanced design I have attempted to trim. Previously I had tended, like a lot of people, to stop trimming when it got "good enough". One former member of our club used to shout "don't change a thing" at every opportunity. By not following that instruction I ended up with a better-performing plane, and a deeper, gut-level grasp of the interplay among the various trim adjustments. It's one thing to know the principles and another to experience them in action. Much fun was had. And of course I have much more to learn.
The new experiment involves fixed flaps. Our club has caught Skyray fever recently, and they are sprouting like rabbits. I was flying the club Skyray last Saturday (an orthodox kit Skyray: .20FP BBTU, no adjustable leadouts, crashed and repaired). I noticed that the plane stalls in the last corner of triangles, and the stall can be reduced somewhat by softening the corners (no surprise there). It occurred to me that this plane might be a good opportunity to try adding fixed flaps temporarily with tape and pins to see if the stalling improves or if fixed flaps are mostly decorative. I'm curious if anyone has tried this experiment before: the same plane with and without fixed flaps.
-
If you want something even more interesting, try fixed, deflected flaps.
-
If you want something even more interesting, try fixed, deflected flaps.
Is this a serious suggestion? It's sometimes hard to tell with Howard The Cryptic. If yes, would this be a pair of flaps, one deflected up, the other down?
-
If yes, would this be a pair of flaps, one deflected up, the other down?
That would certainly be interesting in the eights.
-
There are too many interacting factors at work.
Just shoving fixed flaps onto a Skyray is going to tell you more about increasing the wing area, or decreasing the tail moment arm, than it is going to tell you about fixed flaps by themselves.
-
Is this a serious suggestion?
Of course. It shows you what flaps can do in the absence of hinge moment. I had an airplane once called the Cow. I don't remember its original purpose, but I outfitted it with large, fixed, split flaps on the bottom of the wing. It flew at approximately 4 MPH and turned really tight insides. The Cow was the precursor of the aircraft shown at the left. The Cow would not have done a respectable stunt pattern.
-
The Cow would have made an interesting Slow Combat plane. You tool around at 4 mph a foot off the ground, then wait for the other guy to come up behind you and snap a nifty 3 foot loop as he whizzes past, hopefully without cutting your own streamer.
Would you mind describing in more detail, or posting a sketch of the strange movable flaps on the blue Streak, if it's not too much trouble? Thanks.
-
The Cow would have made an interesting Slow Combat plane. You tool around at 4 mph a foot off the ground, then wait for the other guy to come up behind you and snap a nifty 3 foot loop as he whizzes past, hopefully without cutting your own streamer.
Would you mind describing in more detail, or posting a sketch of the strange movable flaps on the blue Streak, if it's not too much trouble? Thanks.
That was exactly my plan. I figured that I'd win a match or two that way just by going the entire 5 minutes without a pit stop.
The cross section of those flaps is an equilateral triangle. When they are deflected 35 degrees or so, the upper surface (for an inside loop) is faired to the main surface of the wing. They are the moral equivalent of split flaps, but they go both ways. I think they have merit for stunt.
-
The new experiment involves fixed flaps. Our club has caught Skyray fever recently, and they are sprouting like rabbits. I was flying the club Skyray last Saturday (an orthodox kit Skyray: .20FP BBTU, no adjustable leadouts, crashed and repaired). I noticed that the plane stalls in the last corner of triangles, and the stall can be reduced somewhat by softening the corners (no surprise there). It occurred to me that this plane might be a good opportunity to try adding fixed flaps temporarily with tape and pins to see if the stalling improves or if fixed flaps are mostly decorative. I'm curious if anyone has tried this experiment before: the same plane with and without fixed flaps.
Hard to tell unless you also ballast it up to the same wing loading. Just adding fixed flaps will increase the wing area much more than it adds to the weight so it should help considerably.
Brett
-
That was exactly my plan. I figured that I'd win a match or two that way just by going the entire 5 minutes without a pit stop...
The term "hollow victory" springs to mind, though it could be an amusing way of saving your real equipment until you get to the bada$$ hombres on the elimination ladder you really want to tangle with.
...The cross section of those flaps is an equilateral triangle. When they are deflected 35 degrees or so, the upper surface (for an inside loop) is faired to the main surface of the wing. They are the moral equivalent of split flaps, but they go both ways. I think they have merit for stunt.
This isn't April first. Could it be The Joker's birthday? Well, he said he was serious. OK. At neutral you have 30 degrees of down flap from the point of view of the underside of the flap. At 35 degrees of deflection you have 65 degrees total. Sounds like a dive brake. How long is a side of a Flight Streak-sized equilateral flap?
Hard to tell unless you also ballast it up to the same wing loading....
Brett
Excellent idea, easily done. Thanks. That makes two experiments: one practical, the other more theoretikul-ish...kinda sorta.
...Just adding fixed flaps will increase the wing area much more than it adds to the weight so it should help considerably.
Brett
Hope so. That's the practical experiment.
-
How long is a side of a Flight Streak-sized equilateral flap?
About 2.5", as I recall.
-
Just build another one, light. With balsa instead of ply ribs. If you are inclined to experiment try moveable flaps with a longer tail movement and a 30% larger stab/elevator. Experimenting on a crashed and repaired plane... all kinds of questions. Are there any warps now or misalignment. How heavy. If the aim is to find something out about aerodynamic changes, best start with a straight well built blank slate. Stalling on the third turn in a triangle can also be a function of inadequate power or over control, hitting too much elevator. Less elevator may allow the plane to power through. After spending nearly nine hours judging classic Advanced at Brodak a couple of weeks ago, I must note ;), that crashed and repaired profile is not the only plane around having 3 rd corner triangle issues.