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These Song Lyrics Seem Apt for Tim and RichardQuote:
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Last edited by NC14310; Oct 22, 2018 at 03:54 PM.
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NASA does show a correction page ---
https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html Note the page title --- ' Incorrect Theory #1' ........................................ I still recall the Indian and African elephants comment, (post #27). i.e. true statements. ....................................... Quote:
Or can you get lift from not accelerating air down ? Or it isn't Newton ? Can you demonstrate otherwise ? Every one love to make their own interpretation of what is actually written. ? |
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I know not what course others may take, but as for me,
The written word always needs a second or third look. The written word is typically nothing more than an interpretation of undocumented and or unproven thoughts. |
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The 40 % typically weighed 38/40 lb dry The 1/5 scale , 11 lbs or less The object was never to get scale like performance In order to fly the models, standing in one spot, you need to have relatively, far more power. This allows you to pack the maneuvers into a smaller space. This was all done 20 30 years ago Today , we do the same maneuvers with 9 ounce electric models in a 50 ft box Tumbles are impossible Just as in nature, the aircraft performance is tied to size If you go to indoor aerobatics, you can throw your reference books away. |
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Last edited by richard hanson; Oct 21, 2018 at 11:14 AM.
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Was the invention of writing a mistake? YOUR object. Other people might have different objectives. You seem to have trouble with that. Quote:
I suspect more open-minded people involved in indoor aerobatics would disagree with you. |
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You got me
I have nothing to rely on but experience |
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For 'scale like performance' (if you mean flying), just fly on calm days ---
6 m span, 5 kg weight (some people can build very light) --
The thread -- Douglas Globemaster C 124 Scale 8,85:1 by Thomas Maier . |
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That is a very good approximation of scale like flight
The scale stuff I have flown in the past was always far too heavy and so was spooky to fly One friend now past, built award winning scale models but they were all bricks A couple of us would fly the models for exhibitions and it was always nerve wracking The advent of electric power has certainly changed all this Creating the illusion of scale flight is tricky The huge team built models ,flown in Europe do a good job of this and now some ultra light indoor electrics can achieve the slow smooth look Tho it all looks right, most of it is still too fast if you are a freak for textbook scale And those critics ,typically have no experience at doing it |
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Air has to be accelerated downwards? Nope, acceleration is not force, it's a result of the application of force. Does the plane accelerate upwards? And yet lift is applied to it. And you keep on not understanding what the third law actually says. Go and re-read Newton's principles of motion. |
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Me thinks Tim is having a bit of fun.
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In your first post of this thread. You’re having difficulty properly interpreting words that you’ve written. Perhaps that explains your difficulty in properly interpreting the words on a K-12 web page. BTW, they’re still laughing at you. |
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Last edited by ShoeDLG; Oct 22, 2018 at 06:05 PM.
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What does "scale like" mean to you?Quote:
Achieving this requires building light, slow flying models. That's perfectly all right, if realism goes no deeper than flying straight and level. The traffic pattern flown by that Globemaster model was ridiculously tight. Watching the video, it was immediately obvious that this was a model as soon as it began to turn. "Dynamic scaling" uses a different principle. We can't scale down the Earth's gravitational field, so the idea is that the model "sees" the same acceleration as the full scale for similar maneuvers. A 2G turn, or 4G loop, will be the same for both. This forces the design in a different direction. Keeping acceleration constant requires a 1/4 scale model to fly at 1/2 scale speed, the square root of the scale ratio. It also requires it to complete a maneuver in 1/2 the scale time. Which makes sense - everyone knows smaller models naturally respond faster, because of their lower inertia. It turns out mathematically that "dynamic scaling" requires the model's weight to vary as the cube of the scale factor - so a 1/4 scale model would have 1/64 the full scale weight. A "scale speed" model requires weight to vary as the fourth power - so a 1/4 scale would have 1/256 the full scale weight. Wikipedia gives the following for the full scale Globemaster: https://en.wikipedia.org/wiki/Dougla...Globemaster_II Span: 53 m Weight: 45984 kg - 88220 kg For the model in the video, the scale ratio is 53/6 = 8.83 The corresponding weight ranges are: Dynamic scale: 66.7 lb - 128 lb Scale speed: 7.55 kg - 14.5 kg Looking at these results, the model is probably flying a bit slower than scale speed (traffic pattern airspeed is unfortunately not noted), but it's pretty close. Running the calculation the other way, this model is the dynamic equivalent of a full scale Globemaster weighing only 3446 lb! Which explains why its maneuvering ability is completely different. Which is "right"? That depends - what are you trying to do? If you just want to build the lightest possible models and fly in slow motion, no one can say you nay. |
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Logic as an Optional Extra (like air conditioning or power seats)
re: Poor Newton's Almanack
When folks point out to me that someone has done something not logical I tend to ask them, "How long have you been living on this planet?". We even have world leaders who to this day consistently demonstrate the effective use of non sequitur "reasoning" as applied to "What I say goes" or "Whatever I say is true" (in the moment). The ways of the French Sun King Louis XIV still lingers .... just try keep your heads on folks while things sort of work themselves out. "A mind is a terrible thing (etc.)" Nevermind (G. Radner as R. Roseannadanna) |
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Forgive me
From Poor Richards Almanac: This being a modeling science forum, I thot I wouldst pontificate a bit on scientific changes in modeling, specifically, scale models. My first kit was a scale model of Frank Hawks ,Time. Flies I was 13. And had an. Atom 09 to power it with The completed controline model taxied at a good clip but alas and alack, was never to fly. Cut to much later, I decided my second scale model would be a P51 Top Flite kit This one flew but my instructor snapped it on landing I was informed that warbirds are necessarily heavy to fly scalelike This seemed to be a generally accepted std Further experiences in flying others scale designs, showed scale typically meant heavy Fast forward to 1990s Scale arfs from Japan started to arrive These were-ply balsa designs which again, prooved to be overweight Jump to the advent of good electric motors and li po batts then 2.4 radio The imports became injected molded epp , which were far lighter than the wood stuff In the space of less than 20 years, we got Light strong foam Very efficient electric power Radios which were free from frequency conflicts The current crop of foam arfs are light, strong and as far as I have see , capable of far more scale like performance than the stuff we labored over back when A Oddly enough, the rather rounded and blunted and strange thick airfoils worked just fine Many times they worked better than the painstakingly built wood and silk designs As gliders some were also quite good and some, well, not so good but all in all Better than the scale foils and sharp trailing edges etc, we were told were important for proper flight. So we learned, there is always room for improvement and re evaluation of accepted teaching It has been a very interesting journey and it isn’t,over yet |
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