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Old Oct 10, 2011, 03:41 PM
Grumpy old git.. Who me?
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Quote:
Originally Posted by Cap_n_Dave View Post
Without on-board instrumentation, very little data can be gathered from an RC model. Correlating wind tunnel to real-world will be a bit of a challenge, I think.
+1.. If all the work done on the 'Big step' series if tests has proved anything it's that getting definitive and clear test results from normal sports type R/C models flying in real world conditions is very difficult bordering on impossible.

Steve
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Old Oct 10, 2011, 03:45 PM
just Some Useless Geek
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Really? Really? Go back and take a look at some of Bruce's (viking60) work. Notice the attention to detail Bruce puts into his research, his experiments, the way he collects data, and the reports he presents. Go ahead, read. I'll wait.

Afterwards, please come back here and explain what it is about that kind of research that you find objectionable. If you have more reliable data with better acquisition methods, better documented, more accurate, finer granularity, yada yada yada, then please present them here. Otherwise, how can you object to what science we've been able to perform with our limited resources?

This discussion has been going on for some time now. I don't expect we'll have a definitive answer in the next five minutes, and we may not get one in the next five years. What we've got is a small group of dedicated R/C flyers and experimenters who perform single-variable experiments to determine what works best. Until such time as the instrumentation becomes both sophisticated and reliable enough to more accurately reflect and predict the real world results other flyboys are seeing then I will stick with what I see working.

To repeat: I am not objecting to any wind tunnel results anybody can come up with. But unless those data support the conclusions that we've already seen in actual flying models then I am presuming the experimental model is somehow flawed. Please produce supporting data to convince me otherwise.
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Old Oct 10, 2011, 04:33 PM
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Originally Posted by A Useless Geek View Post
Really? Really? Go back and take a look at some of Bruce's (viking60) work.
Link please.


Quote:
Go ahead, read. I'll wait.
You really want to start an internet fight over this?


Quote:
But unless those data support the conclusions that we've already seen in actual flying models then I am presuming the experimental model is somehow flawed. Please produce supporting data to convince me otherwise.
When I see some data, I may have a comment or two for you.
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Old Oct 10, 2011, 05:39 PM
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Fairplay, South Park, CO
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Switching from single saervo to dual servos for ailerons

Friends,

I just did a quick upgrade on the 59.5" span MH32/KF3P wing. I've installed a second 9 gram aileron servo just alongside the original single servo. This allows using the same control links and horns as were used with the single servo setup.

With the dual aileron servos, I can now use flaperon or spoileron control functions while landing, can adjust for optimum aileron differential travel, and can now also experiment with fine-tuning of the airfoil camber from the transmitter.

I'll be test flying these capabilities on two existing fuselages before building out another new fuselage; I'll post test flight progress reports in the DANCER discussion thread:

http://www.rcgroups.com/forums/showthread.php?t=860461

VIKING
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Old Oct 10, 2011, 11:20 PM
fix-it-up chappie
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Valley Village, CA
Joined Jan 2002
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Quote:
Originally Posted by A Useless Geek View Post
Really? Really? Go back and take a look at some of Bruce's (viking60) work. Notice the attention to detail Bruce puts into his research, his experiments, the way he collects data, and the reports he presents. Go ahead, read. I'll wait.

Afterwards, please come back here and explain what it is about that kind of research that you find objectionable. If you have more reliable data with better acquisition methods, better documented, more accurate, finer granularity, yada yada yada, then please present them here. Otherwise, how can you object to what science we've been able to perform with our limited resources?

This discussion has been going on for some time now. I don't expect we'll have a definitive answer in the next five minutes, and we may not get one in the next five years. What we've got is a small group of dedicated R/C flyers and experimenters who perform single-variable experiments to determine what works best. Until such time as the instrumentation becomes both sophisticated and reliable enough to more accurately reflect and predict the real world results other flyboys are seeing then I will stick with what I see working.

To repeat: I am not objecting to any wind tunnel results anybody can come up with. But unless those data support the conclusions that we've already seen in actual flying models then I am presuming the experimental model is somehow flawed. Please produce supporting data to convince me otherwise.
Not that I don't agree with you in the main, but...

Bruce's work is excellent, but it is not objective. That's not a slight on him, none of us are objective. The only way to know for sure would be to evaluate several airfoils in exactly the same conditions in an extremely controlled environment. Oh, and then have someone else do the same tests in their lab, and get similar results. Anything outside of that is not objective.

That is not to say anything about Bruce or his work. As I said, I think it rather excellent. But it is not scientific, or at least not Scientific with a capital S.

The problem is there is no way to fly a plane, and know definitely everything that is going on. This is a problme for ALL of us. Everyone.

See this on science Bias.

Or this on Confirmation Bias.

Now don't get me wrong. I love me the KF airfoils. My problem is I don't know when I'm looking at data that supports them if the data is the real deal, or conformational bias on my part. There's the rub. It turns out we all edit the info we perceive to make it confirm to our pre-disposed ideas of reality. Oh, and one of the pre-disposed defaults is the idea that "we" are always viewing it "correctly".

I think Cap_n_Dave has the right of it, if you want to get all scientific. The good thing is you can build a KF wing and fly it all day regardless of what anyone says, and it will make you happy. For most of us, that is good enough.
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Old Oct 11, 2011, 01:07 AM
Build straight - Fly twisty
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This interesting stuff on bias should have no bearing on the results of wind tunnel testing.
It may well have a bearing on how some people accept or reject the results, but that's quite another matter.
It's just not true that people do not depart from strongly held views. The Wright brothers argued furiously over many things and after a nights sleep accepted the view of the other and then argued passionately from the reversed positions.
If Springer builds a tunnel and conducts comparative tests, I am sure he will not fudge results in any way.
At the end of testing we will know for sure that: Under *these* conditions, *this* wing section performed *this way* compared to *that* wing section.
That'd do me.
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Old Oct 11, 2011, 01:38 AM
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"We have anecdotal evidence to support this ... " ~ Dogbert
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Old Oct 11, 2011, 01:50 AM
Grumpy old git.. Who me?
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Quote:
Originally Posted by A Useless Geek View Post
Really? Really?

Yes.. really really!
The only testing that Ive seen that is anything like scientific is that done by the Mick's in their 'Big step' tests.
Correct me if I'm mistaken but Viking60's tests, very interesting though they were, did not objectively (i.e measurably, not relying on perception or feeling) compare different (stepped vs. non-stepped) airfoils under identical conditions as would be required for any form of even remotely scientific testing.
Also to be truly scientific the test should really be done 'blind' i.e. the flyer should not know which airfoil he's flying, this rules out bias, which we are all prone to, it's a human trait. Even the Mick's testing failed on this last count so could not really be classed as truly 'scientific' in approach, but they did do a pretty good job non the less.

Steve
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Old Oct 11, 2011, 02:03 AM
Grumpy old git.. Who me?
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PS.. There is an easier way to prove, one way or another, the efficiency of KF airfoils. Rather than spend ages building wind tunnels and doing tests that some might not believe anyway; why not just build a really high performance KF wing glider (say a 1.5m contest spec discus launch glider). Then go along to an organised contest and beat all the other models. That's how you could prove the claims to be true. After you did it a couple of times no one, including me, could argue. No amount of wind tunnel testing however well done would have the same impact.

Steve
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Old Oct 11, 2011, 02:41 AM
just Some Useless Geek
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Oh, boy. This is just going to go around and around, isn't it? Okay, well, you "pure" science guys go ahead and build wind tunnels, conduct your tests, and get back to us, eh? In the mean time, those of us who actually fly model airplanes will be building some KF wings and taking advantage of the characteristics we already know to be there.
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Old Oct 11, 2011, 03:33 AM
Build straight - Fly twisty
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Australia, QLD, Little Mountain
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Quote:
In the mean time, those of us who actually fly model airplanes will be building some KF wings and taking advantage of the characteristics we already know to be there.
The plane I fly most has a KF4 wing, but I can't see it doing anything my conventional symmetrical section wing planes can't do. It does outperform an earlier flat plate wing (except at hovering) and the glide of the KF4 is way better than the flat one.
Please don't get grumpy because some of us wish to seek the truth.
Who knows. The KF may be shown to be better. You'd love us then, wouldn't you?

Quote:
There is an easier way... just build a really high performance KF wing glider... Then go along to an organised contest and beat all the other models.
That does not sound easy to me. And talk about variables.
Like, you could give me the model that won the last World's Champs and there's no way I could win anything with it.
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Old Oct 11, 2011, 05:09 AM
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Originally Posted by Whiskers View Post
Like, you could give me the model that won the last World's Champs and there's no way I could win anything with it.
EXACTLY.

When you think an airplane "flies good" doesn't mean you've confirmed the "airfoil is better."
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Old Oct 11, 2011, 07:39 AM
Grumpy old git.. Who me?
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Quote:
Originally Posted by A Useless Geek View Post
those of us who actually fly model airplanes will be building some KF wings and taking advantage of the characteristics we already know to be there.
'knowing' something to be true without any solid evidence to support that belief is faith not science.. Perhaps KF should be declared a religion and Dick Kline a deity?

(Just funning.. not meant to offend anyone)

By the way, I'm not actually advocating doing wind tunnel testing because I don’t think it will convince the true believers on either side of the fence. As you have already very clearly stated; you "know" KF has benefits, so if the wind tunnel indicated otherwise you would ignore it, your mind is made up already, no 'science' is going to change it.
Equally the guys who follow conventional airfoil wisdom would hardly be convinced by amateur wind tunnel testing done by folks with (in their view) no credentials who are seen as KF enthusiasts, and so biased. So either way people will remain unconvinced.
On top of this some of the claimed benefits for KF like stability and the like would not readily be identifiable in a simple wind tunnel.

That's why I suggested building a plane to use in competition. If you dont think your skills are up to it go along anyway and let some of the top guys have a fly and see how it does in their hands.

Steve

PS.. It's a strange statement to make that those who actually fly model airplanes will build KF wings.. please explain?
I fly lots of model airplanes of many types and have been doing so for over 40 years and have not and I don’t suppose will be making any KF wings. Also consider most other model flyers (who have likely never heard of a KF airfoils). I guess these are all exceptions to your little rule
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Old Oct 11, 2011, 08:07 AM
Jack
USA, ME, Ellsworth
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"..It's a strange statement to make that..."

His statement is probably not any stranger than say, someone who would come to a place where people are primarily discussing the actual results of building KF wings and their experiences in flying them, without having actually done any of the same building and flying, and want to speak to or question the validity of or even argue with some of their impressions.

And to take "real science" from other venues and use that as a basis for counterpoints for arguing some of the impressions is pretty much guess work without some science on both sides of the discussion.

And I don't think anyone is trying to prove that a KF airfoil is better than any other airfoil as much as just trying to understand it better. If you take any two airfoils in the world and compare them you are going to find each to have areas where it is better than the other. And the KF foil has outperformed some airfoils in some areas if you look at (and even better, actually experience!) to entire process from building through flying.

Jack
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Old Oct 11, 2011, 09:23 AM
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Why do you fly?

Friends,

Flying is very much a subjective experience and process. It's all part of why I enjoy it.

Weather conditions are also subjective and continuously variable.... neither 'good' or 'bad', but always subjective.

I fly in the real world, outdoors, in whatever variable conditions Mother Nature might throw at me. It's very much a part of the experience which makes it enjoyable... and sometimes more challenging.

I love high winds in slope flying venues, enjoy flying in it, and sometimes enjoy designing & building aircraft which perform well in those high wind conditions. That type of flying is very 'subjective' - it requires exercising what are referred to as 'pilot skills'. That's why I fly my own designs in slope combat, and perform best as a slope combat pilot when flying the slope ships which I've designed, built, and optimized.

I build a wide variety of miniature aircraft which I enjoy flying in the real world. I sometimes make progressive changes to aircraft configurations (wing shape variables, control surface configuration variations and management, fuselage configuration variables- balance, incidences, etc.) and by flying before and after having made each of those changes, I may have a perception of whether the subject aircraft handles more or less to my 'liking' after having made those changes.

I may have certain changes in handling and performance in mind as a goal of specific changes. And from the unique perspective of the one handling the controls, I may have a subjective perception of whether a specific change which I've chosen to implement has 'improved', 'degraded', or resulted in no perceptible change in a specific performance or handling aspect which I was intending to influence with that specific change which I chose to implement.

Subjective? Exactly and Totally!!! And, by the way, very effective for my own purposes. I design, build, and fly for my own personal enjoyment, and that, too is very subjective.

Occasionally I share some of my observations. I'm certainly not here to 'prove' anything to anyone - if you have anything in the way of both building and 'piloting skills', then each of you can do that for yourselves... (or not, as you might choose....)

Flying is, and will always be a very 'subjective' experience.

FLY!

VIKING
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