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Author Topic: the notions of Can't vs Can  (Read 1053 times)
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packardpursuit
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« on: June 12, 2017, 04:24:46 PM »

Now THIS, IMHO, is an outstanding modelling accomplishment:
 https://www.youtube.com/watch?v=xDtqUg8R6Jw
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kukailimoku
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« Reply #1 on: June 12, 2017, 07:02:19 PM »

The fuse is a balloon?

Wow.
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Hepcat
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« Reply #2 on: June 12, 2017, 07:37:12 PM »

PP
It is a clever fake of some sort. Did you want us discuss how it was done?
John
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PB_guy
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« Reply #3 on: June 12, 2017, 08:02:49 PM »

See also: https://www.youtube.com/watch?v=_BhFxcXsf58
Quote
Published on Dec 4, 2015
-Airbus A310 by Martin Müller at different locations-
The main goal was to design a model which would not only look scale, but would fly like the original – not too fast, but not too slow either. As the model was planned to have all characteristic features, like functional flaps, retractable landing, lights etc. it was clear from the beginning, that the construction needed to be very light. An inflatable fuselage appeared to be the best solution.
The A310-200 was selected for various reasons, but especially for its fuselage-wing-blending and landing gear arrangement. Martin also wanted to copy the originals control method via spoilers, i.e. no outboard ailerons.

While the start of this project was triggered at the model-hobby-spiel in Leipzig 2010, it was the same fair which saw the premiere a year later.
Not quite finished yet, the Airbus A310 performed the first test flights there.
In the meantime the model got more powerful motors, full scale lighting and the paint job was completed.
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packardpursuit
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« Reply #4 on: June 14, 2017, 12:13:52 PM »

"It is a clever fake of some sort. Did you want us discuss how it was done?"

No, I pretty much wanted to illustrate the difference between achieving a model goal successfully, rather than the usual blather from "negative nellies" who  have been saying for years scale like flight is impossible because of "Reynolds numbers", scale airfoils won't work etc. 

This fellow obviously traversing realms of model flight technology most won't even acknowledge.

Light weight is the obvious single major factor making scale like flight speeds possible. Some have speculated, over on RCG, that the fuselage may be filled with helium. Does it really matter?

I was thinking about how this kind of positive thinking might cross over into my areas of interest. Mainly FF, CL, and RC scale.

I don't care if it was done with smoke and mirrors. Model magic is where one finds it. This is model magic. Grin Grin Grin

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PB_guy
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« Reply #5 on: June 14, 2017, 12:42:43 PM »

More info on that interesting model, the helium-filled fuselage and Martin Müller can be found here:
http://www.tested.com/art/makers/601963-martin-muller-designs-rc-vehicles-fly-appropriately-scaled-speeds/
ian
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Flyguy
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« Reply #6 on: June 14, 2017, 01:51:08 PM »

Thanks for the link, interesting. The indoor jet really is really dramatic, retractable gear and flaps as well, and for outdoors he doesn't use the helium because he needs the extra weight!

I wonder what RC receiver/servo/battery he's using, I didn't see that mentioned.
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Yak 52
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« Reply #7 on: June 14, 2017, 05:01:16 PM »

It really is a sensational model!

Shame it had to end like this:
https://static.rcgroups.net/forums/attachments/2/2/8/6/5/a7638269-169-IMG_6775.JPG

 Wink
the notions of Can't vs Can
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Pete Fardell
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« Reply #8 on: June 14, 2017, 05:45:52 PM »

... "negative nellies" who  have been saying for years scale like flight is impossible because of "Reynolds numbers", scale airfoils won't work etc. 

...Some have speculated, over on RCG, that the fuselage may be filled with helium. Does it really matter?

With respect, if we're talking about the challenges of scale aerofoils, Reynolds numbers etc. I think it DOES matter if it was helium filled, and was rather disappointed to hear that might be the case. Bit disappointed to see the fuselage is a balloon too.

I certainly couldn't have made it myself though and agree it's a fine model. Really enjoyed the video, so thanks for posting the link.
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Rich Moore
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« Reply #9 on: June 14, 2017, 05:54:00 PM »

It's bad enough already when a motor bursts. Imagine if the whole model went 'POP!' or raspberried around wildly (although it might help me get a bit more duration)
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Yak 52
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« Reply #10 on: June 15, 2017, 07:55:14 AM »

...

No, I pretty much wanted to illustrate the difference between achieving a model goal successfully, rather than the usual blather from "negative nellies" who  have been saying for years scale like flight is impossible because of "Reynolds numbers", scale airfoils won't work etc...

It's not a scale airfoil though is it. It appears to be Jedelsky construction outboard of the nacelles giving a very thin curved plate. Exactly what is needed for slow flight at low Reynolds numbers.

The model is beautifully optimised for a particular goal - the appearance of realistic flying. It doesn't meet a very high criteria for scale fidelity from a static judging perspective though - but that's ok, it's not designed for that.

The outstanding achievement here is that the designer has a clear understanding of the limitations imposed upon model flying (by physics - not by a lack of imagination or negativity), and has used this understanding and some serious ingenuity to work around the limits to his goal. Positive thinking doesn't really come into it.

https://laughingsquid.com/wp-content/uploads/2015/03/dsc0457-750x499.jpg
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fred
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« Reply #11 on: June 15, 2017, 01:15:51 PM »

Amazing model /accomplishment No arguement.
  Elephant in the room question tho seems as to the Why?
of a Big model in a barely adequate to needs space.
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dosco
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« Reply #12 on: June 16, 2017, 08:09:19 AM »

The balloon fuselage idea is interesting ... and not all that off from the 'real deal' pressurized fuselage. Of course, the real deal doesn't collapse upon itself when deflated ...

-Dave
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frash
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« Reply #13 on: June 16, 2017, 10:30:38 AM »

This is a marvelous model aircraft and is incredibly slow and graceful.

If you scope out the effect of helium, the stiffness is important, but the lift is less than expected, about enough to lift the empty bag for the helium.

This will be mixed metric and English units because that is how I think. <Sorry>

Air is mostly nitrogen of molecular weight 28 and about 21% oxygen of MW 32. Therefore for estimation purposes, MW of air is ~29. Helium MW is 4 and hydrogen is 2. Lift is the difference between the volume of air displaced and the volume of helium or 25 g per 22.4 liters at standard temp (25 deg and 1 atm at sea level).

Visualize that the volume of helium is 21 2-liter soft drink bottles (array of 2*2*5  +1 bottle as tail cone) or almost 44.8 L. Then the lift is only 2*25 g or almost 2 oz. No correction was made for the additional helium required to make the fuselage stiff but we know that inflation pressure is about 30 psig (3 atm) in our automobile tires. In my short stint with a toy RC blimp firm, we never credibly measured the He pressure in a toy blimp.

Don’t let the helium distract us from the impressive achievement of this model.

Fred Rash
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Warhawk
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« Reply #14 on: June 16, 2017, 10:36:03 AM »

I think we owe Mr. Muller a bit of gratitude for showing what can be accomplished with the powered balloon technology.  I've seen the dirigible-type of RC helium balloons, but the realistic appearance, and the ability to fly in areas you wouldn't expect (like malls, indoor arenas of most types, etc.) surely makes his efforts good ambassadors for our hobby.  Visiting his site, he's working on 1/43 scale "Drift" cars, and a very light-weight jet.  I wonder how he got the fuselage balloons made?

Justin
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packardpursuit
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« Reply #15 on: August 08, 2017, 04:20:07 PM »

I find it interesting that larger than normal indoor FF scale models seem to be a trend.

Years ago, at he IPMS, I recall Tony Nacaratto's able demonstrations of a very large and slow flying M.Farman monoplane, to a very enthusiastic indoor crowd. It too, was magic, every time I was priviledged to see it.  It was indoor R/C and electric, both relatively new concepts, at the time.

I suspect he helium bag as seen in photos of the airliner, is rather easy to fabricate with templates and soldering gun w/blade tip.  The ard part is setting up the templates and arriving at proper cutting/sealing temp. and rate of cut (speed). You can see the nose is a formed light weight shell.
Ive seen nothing to suggest the airfoils are overly non-scale!
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dosco
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« Reply #16 on: August 09, 2017, 05:44:14 AM »

I find it interesting that larger than normal indoor FF scale models seem to be a trend.

Years ago, at he IPMS, I recall Tony Nacaratto's able demonstrations of a very large and slow flying M.Farman monoplane, to a very enthusiastic indoor crowd. It too, was magic, every time I was priviledged to see it.  It was indoor R/C and electric, both relatively new concepts, at the time.

I suspect he helium bag as seen in photos of the airliner, is rather easy to fabricate with templates and soldering gun w/blade tip.  The ard part is setting up the templates and arriving at proper cutting/sealing temp. and rate of cut (speed). You can see the nose is a formed light weight shell.
Ive seen nothing to suggest the airfoils are overly non-scale!


On a mildly related note, in 1990 or so, I was at the Columbia Rotunda and watched Dave Aronstein's (coconut-scale) Cessna Caravan fly. It was spectacular.

-Dave
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LOUCRANE
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« Reply #17 on: August 10, 2017, 04:26:42 AM »

I was amazed at one factor in particular: Most scale models in flight do not have a realistic "rate of progress."  ...by which I mean the apparent speed in terms of - crudely put - plane-lengths per unit time. A C-17 landing looks slow, although its length makes the time for "one plane length" to pass a point more possible in terms of the science of flight involved.

So, he used a hydrogen-filled balloon instead... Almost looks too slow!

Nice work! Enjoyed it...
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/LOU
Hepcat
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« Reply #18 on: August 10, 2017, 06:26:45 AM »

reply to #17
That is interesting Lou because in my first reply, when I said it was faked in some way I thought it had been filmed in slow motion (if that is still the corect term for making the action look slow).
John
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DavidJP
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« Reply #19 on: August 10, 2017, 06:40:10 AM »

I agree with what Yak52 says in post 10 above - and after all I don't see he is setting out to have it regarded as a class one scale model?  Good achievement using modern technology.  Thank you for posting the topic.   
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packardpursuit
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« Reply #20 on: August 10, 2017, 01:36:21 PM »

DavidJP

Thanks for joining in. I found your comment interesting and thought provoking. Let me ask you, was the subject offered in any way shape or form as suggesting this was supposed to be or meet some named or pre-concieved scale criteria OTHER than scale like speed?? Cheesy Cheesy

The argument about scale speed has been on going for many years. Indeed many can't seem to agree on what it is, exactly. After much head scratching and Hmmm'ing, ive decided that scale speed is a true set of factors that can be scaled. So many fuselage lengths past an imaginary point, etc. Howeve,r I like to think of it a bit differently.  Let's  see if any agree/disagree.

For convenience, lets use an imaginary 1/4 scale "Whatever 140" to envision the mechanics.  Let's say a real Whatever is  passing in front of our fixed Vantage Point, at one mile out and 1000 ft altitude. Speed is 100 mph. and takes 10 seconds to travers one mile, defining our angular  field of view, left to right and upward. Now imagine our perfect outline 1/4 scale mode, from same VP,  at 1/4 mile out, at 250ft up and traveling at 25 mph. It will match the EXACT same time and angular frame as the full size. Angles and time remain constant, which aren't scalable, while the distances and dimensions, are.

I like LOUCRANE's "rate of progress" notion!

That our models aren't readily capable  flying at scale speeds is another matter entirely. However, convincing  scale like speeds are achievable if one cares to employ reasonable practices. I believe it's more mental than physical.  Just as one can suggest scale detail on a less than perfect model, one can also suggest scale like speeds with HOW one flies said models.

I think it telling that the notion of exact scale attribute (either as a negative or a positive) gets mentioned regularly in these kinds of discussions. On one hand, scale like speeds get poo-pood because, after all  rubber scale/sport scale models aren't very scale anyway, or on the other-other hand, this relatively crude but near totally believable flying Airbus model has to have, apparently some mention for being less than perfectly executed. Hence my frustrated comments about can't vs CAN. 

There is one point where every model attains exact scale speed. That's when it's sitting on a shelt or whetever instance where it's not flying. Real airpalnes remain parked for long periods of time. They always look like they should, 100% of time. Our model not so much. I understand why some say they don't need exact scale outline  and shapes because they cant see them when it's up 250 ft. I also understand deviation from scale for flight performance enhancement, however this could be limited to a greater extent.Please see this as less an appeal for greater exact scale inclusion but an observation that more scale like finess is more appreciated especially when our model is sitting or flying by, closer to our vantage point.
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F4FGuy
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« Reply #21 on: September 27, 2017, 02:45:42 AM »

OK Packard,

I'm baaaaaack.  Just can't resist any longer! I must agree, this is a marvelous example of the possible! It's also an interesting study in making choices.
This man knew that to fly at realistic speeds,and indoors at that, he must choose between exact outline, and flight envelope.
He also knew that the speeds he envisioned, he would have a problem with Rn values. His solutions to these problems are nothing short of brilliant.
Structurally, the use of a pressurized flexible wall tube is perfect. The helium makes little difference, it's the slight pressurization that gives it stiffness.
All in all a masterful engineering job.

Ron Burn (F4FGuy)   
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