What Serge was referring to was the fact that overhead line tension consists of the centrifugal force minus the 1G force of gravity. That's from inertial components (ignoring aerodynamics). It's physical law.
While one test may equate to ten thousand formulas to you, I have to ask, how is the "test" being conducted? How are you measuring line tension, for example? What kind of controls do you have over the variables? (say wind speed, and model speed?). I'd challenge this notion that some subjective "test" somehow is worth ten thousand "formulas" - perhaps to you, to your way of thinking. But in reality, ten thousand formulas (equations would be a better word) can pretty well express the system dynamics of a model airplane on flying on a tether.
You seem unreasonably hostile toward physics and scientific analysis, Robert. Why? What's been described is simple algebra, the kind you learn in high school. In reality, more serious analysis uses calculus, derivatives and integrals, quadratic equations. At the Newtonian level, physical things beautifully obey laws which are well defined by now. I don't see what is inherently wrong with us using mathematics to understand physical behavior, it works so well, it's another TOOL.
As we investigate and learn about physics and the math that describes it, many of us are impressed by the *beauty* of it all. It's very "clean" and beautiful in the same way that any good design is. The incomplete nature of our understanding the real world has a lot more to do with imperfect data plugged into equations. Often there are seemingly unimportant features which end up being significant to the result. Or vice versa. This "fuzzy" nature of things is well noted in our CL stunt model airplanes.
I always am impressed with and commend people who strive for excellence, working hard. But I submit to you that a truly serious effort needs to involve a lot more than cut and try and seat of the pants evaluations. Here's what I suggest - without delving deeply into integrals and quadratic equations, give the basic ones their due; a starting point. Awareness of the properties of mass and inertia, gravity. Effects of center of gravity, and moment of inertia. Some idea of the actual forces and performance involved, from actual measurement.
So, any real ideas about the specifics of your model? What is its moment of inertia? How about its actual performance? What forces is it experiencing? What are its actual velocities at various parts of its pattern?
Oh, and don't forget - what's the definition of "good"? Specifically, what are we seeking to optimize? What define a great stunt ship? How about its control transfer function. How is it damped? Sure, we want to turn a perfect 5' radius corner. But various analyses, including my own, have concluded that our very best stunters are actually performing a 15' radius square corner (I measured 17' from videos).
Damping characteristics of the control system are particularly important. Overdamped and the ship is sluggish, underdamped, it tends toward instability and oscillation, and critically damped, it is (perhaps) "just right", not overshooting or barely doing so, and (near) optimum in terms of performance. In reality, the control system transfer function is what we "feel" when flying, it's what makes us really like or dislike a model, and a function of how well it flies and how easy it is to fly well.
Yes, the transfer function for the control system is greatly affected by weight. And how that weight is distributed (e.g. moment of inertia). But there's also a myriad of other parameters. Obvious ones include wing loading, size of flaps and elevators and their position relations (flaps dampen the control function, by generating an opposing couple). ((If you really demand highest turn performance for square corners, perhaps you should have an unflapped model - see Serge's and Ted Fancher's work in that direction.))
Note that moment of inertial, distribution of the weight, so terribly important to us, is not so easy to measure directly, at least not "by hand". And the serious computations nowadays break components into small triangular elements, which are all considered to do the analysis. In a cruder but useful manner, by knowing the weight and position of various components of your model, you can calculate and estimate its moment of inertia.
Other complexities - thrust and drag, vertical CG, centers and means for aerodynamic forces. The gear's drag and inertia effects. The quality of the stunt airfoil (I learned to appreciate just how great Al Rabe's airfoils are - watched a profile Mustunt with a broken line perform maybe twenty 8' diameter loops before eventually crashing). Airfoil performance - so very important.
Tip weight, leadout positions, flap design (full width or with stationary tip flaps?) stab/elevator design (aspect ratio, area).
And OMG, engines, props, fuel, line diameter and type.
More than WEIGHT is involved. Begin with as much information and knowledge as possible. Then meticulously work on the problem, never denying yourself any tools, including math. If you have a math barrier, work to remove it.
One other thing, Robert. Please stop with the defeatist attitude: "I will probably never win.." Where is that law written? Look at the facts, you are a prolific builder, master craftsman, and finisher. You're very serious about CL stunt and devote a lot of time and effort to it. I would venture to say you're in the top few percentile of stunt contenders, and you are working very hard to get better.
We both know that we are beyond our physical primes, but remember that CL Stunt is pretty much an old man's game. So, I admonish you to flush the defeatism. Kick some butts at the Nats.
I'll look forward to the photos and details of the contest.
Best,
L.
"And all who told it added something new, and all who heard it, made enlargements too." -Alexander Pope
Topic: Weight Matters? Carried over from SSW (Read 6232 times)