The Good, the Bad and the Ugly

[Konrad]

Konrad, even I am getting slightly over this constant search for problems. Frankly, if you look hard enough for trouble, you will find it.
In this critique it appears to the untrained eye that you have discovered catastrophic problems with a new model design that will severely affect its performance and therefore saleability, and as you know that is not true.
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As you said this is not true! So why did you phrase it like it was what I was saying? I said in post #3 this is at best an incremental improvement. Really I never though I'd have any enfluance on the saleability of anything. Really it is just you and me here.

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Let me say this with absolute certainty: The things you mention as problems in actual fact will have no effect whatsoever on how the model flies or how fast it is. This design is developed from a model which is already on a par with most if not all current F3f models, and has been improved from there.

The fact of the matter is that you are using full sized theory on models which are fractional in scale compared to the subjects that were used to delevop said theories. I have said this before - there is little useable low-speed aerodynamics theory, and if you get down in size to our minute models then most of what is available changes or simply does not apply.

This is blatantly false! The wing junction drag and the pressure gradients are more prominent at lower Reynolds numbers. This is one of the reasons we say bigger flies better. If you think this has little or no effect might I suggest you recalibrate your wind tunnel. I mention the speed jump in the AMA 424 426 and 428 classes when we changed from the BUF Scat Cat wing junction to the Jerry Small QV series of racer with its straight side non tapering wing junction and the classic Hoerner wing tip. That statement that air flow behaves different at low Reynolds number is true. But it is well understood and there are volumes on it. (well, with in the last 30 years) Now if you want to ignore Hoerner and his writing so be it. But please tell me what theories your are subscribing to. You said you do everything with a design purpose and that you are willing to share that with anyone that asks. Having talked at length with guys that run wind tunnels here and in the bay area and in Seattle over a growler of beer trying to get more speed out of my slimers. I can tell you Hoerner is very applicable to our model at the Reynolds number they operate in. Your compitition is well aware of this and is using this knowledge to great effect.

I'm sorry to say that the REDshift as it was produced was a very sub-standard F3F ship. It had all sorts of stability issue with the very large side frontal area and too small a rear wetted vertical area. Its stability was atrocious. Had there been more effort on stability with the understanding of the side area and the interaction of the V-tail angle and aspect ratio. Then Yes, maybe your wing would have been a game changer. But as an aircraft is the sum of its part the REDshift was an also ran at best.

Now working with you and seeing what little you have shown, I think the new bird addresses most of the issues I know about. Other than this wing to fuselage junction. ( Not saying that there is a problem. But by my application of Hoerner there is. Will it be at the problem level we had with the Redshift's stability, heck no. But many designer out there are well aware of the wing junction drag and make an effort to control it.

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This is understandable because you personally have no other theories to go on, and you don't have access to the test results provided by actually testing the model's critical components. As I have said before this is a model that has had everyting well thought out, based on four decades of model design, and the things that go against full-sized theory here either don't apply, or do not have any influence.

Doc. I don't think you have any idea of my aeronautical back ground. All I've said is that I'm not an aerodynamicist. But rest assured I'm well versed in high and low reynolds number fluid flow.

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I love discussion, as I have often mentioned, and also constructive criticism, but this strikes me more as judgement; almost as if I have to pass your examination to get the 'Konrad seal of approval'.

Please do remember, all: This is what Konrad Konrad categorizes into "good", "bad" or "ugly" ONLY.

There is no Konrad seal of approval. As I said I'm alway looking for that incremental improvement. So by the TMP (Toyota manufacture Process) of continual improvement I'm always looking for the better way to skin the cat. My apologies to the cat.

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Please do remember, all: This is what Konrad Konrad categorizes into "good", "bad" or "ugly" ONLY.

You are asking me not only to reveal scalable CAD details of my next model, now you are also asking me to also furnish the detailed theories that led to its final design. With the situation right now and the very real possibiity of plagurism, these are not a reasonable requests.

Cheers,

Doc

Yes, The Good ,The Bad and The Ugly was my attempt to add levity to a subject that had gotten under the skin of some on another thread.

No, I did not ask for any proprietary data. You as an engineer/designer and I at one time a manufacturing engineer know there is nothing that be gained by the area cross sections that isn't already known if applying Hoerner's theories. I was stating that I was ignorant of the cross section area at these two station. And therefore my hypothesis is based on conjecture. I clearly state that I don't know if you are disregarding Hoerner's findings or using some other theories (clearly this is a, it looks right curve as you state this has little or no effect). But from what little data I can gleam it sure looks like Hoerner was thrown out the window. And I know it will have a noticeable effect at high Cl. Much like the few degrees and square inches of area had on the REDshift's stability.

BTW. This thread has nothing to do with any one model. It is my interest in trying to get models with a better fuselage. Heck, better models! For now I hold the Freestyler up as the epitome of the craft. Now I think many model can be brought in line with Hoerner's writtings by simple expansion at the area at the rear of the wing to fuselage junction.

Edit: To remove reference to future projects.

 

[Konrad]

Gentlemen - Time for me to dial in this thread a bit.

Konrad you are pushing peoples buttons, your words are being received as less than friendly.

If you care to discuss this further, by all means do, but please take it down a notch.

Really!! Hell, I was even trying to be a bit funny with the spaghetti western theme.

 

[Konrad]

Here I'm trying to show that while some think the round shape is best as a tail boom, it really isn't. Some will point to the fact that Airbus and Boeing use round section fuselages. But that is mainly because these are pressure vessels and subject to high cycle loads 360 degrees.

With our gliders we don't have a pressure vessel. But what we really are concerned with is stiffness, durability and wetted area (parasitic drag).

Now we know that a beam's stiffness goes up by the square of the distance between the elements (in this case the boom's skin). So for any given radius (R) a triangle places 3 very stiff elements with noticeably less surface area than the classic circle. Now if we are willing to suffer X wetted area of a circular boom we can extend some of the elements out R+. This added "R +" adds so much durability as shown in real life by TUD's Freestyler-5 fuselage. (It is almost bullet proof) All we have to do is look at the poor performance of the ovals and circles of say RCRCM's Strega and Sunbird. OK, there is a lot more going on with the premature failure of the RCRCM product than just geometry.

I hope the drawing makes it as clear as ink why the TUD triangular like fuselage boom is one of the best out there for our gliders.

 

[purview]

The wing junction drag and the pressure gradients are more prominent at lower Reynolds numbers. This is one of the reasons we say bigger flies better.

How do we measure? Are gliding ratios of say 1:50 for a model plane good and for a full scale a pretty bad result?


The flying task of high G turns is not within the "performance approved seal" of non-UAVs. So may the designer have trouble with less than 90°degree angles } - but his statement is clear. James designs are based on knowledge and experience, why not look at the performance and eliminate the dumb thumb and pinching goofs bad'n'good days (please consider it not as an attack, we all love this hobby as best we can dooo... dark matters )


If #23 pic1 is true I would ping at R+ and not as a constant to get more horse power (distance time...)

 

[Doc J]

I'd prefer it if my models were not a part of this thread in future - many thanks.

Over and out.

Doc

 

[Konrad]

I can respect that. I will remove any mention of current or future projects. Again this thread was not about anyone project, brand or designer. It was aimed at the discussion of wing to junction drag. And maybe the fuselage as a whole. Yes I'll give examples of what I'm trying to discuss.

And again folks please remember that an aircraft is so much more than the sum of its parts.

 

[Konrad]

How do we measure? Are gliding ratios of say 1:50 for a model plane good and for a full scale a pretty bad result?


The flying task of high G turns is not within the "performance approved seal" of non-UAVs. So may the designer have trouble with less than 90°degree angles } - but his statement is clear. James designs are based on knowledge and experience, why not look at the performance and eliminate the dumb thumb and pinching goofs bad'n'good days (please consider it not as an attack, we all love this hobby as best we can dooo... dark matters )


If #23 pic1 is true I would ping at R+ and not as a constant to get more horse power (distance time...)

Can you try to put this through Google translate , again.

 

[Konrad]

Qq: how do we know anything about the enhancements. Are these models tested in wind tunnels? Or sim software?

Just curious.

Just applying well established theories, here I reference Hoerner's, Fluid - Dynamic Drag. Yes, many models are run through low speed wind tunnels (TUD claims to do this).

I need to warn you that Sim or Software solutions are often fraught with gross errors. This is because they can only deal with the algorithm they are programed with. They do nothing to find the unexpected. The wind tunnel often finds these surprises. So does field testing. But unlike wind tunnels and testing, changes in a sim are fast easy and low cost. But like I say, you often get what you pay for.

 

[purview]

model plane fuselages are designed without cockpit and pilot. unmanned aerial vehicles can therefore designed with slim fuselages.

So why are there planes (model planes) with high volumes of fuselage diameter in front of the wing? Especially your example of an oldskool Sagitta from simprop has such a fuselage. Despite it it also has a less than 90° wing to fuse angle. That is what Konrad states as as not performance improving during flight, as so as the section of the wing root that is decreasing by diameter. Therefore not good for performance.

Konrad, here are my testing plattform planes for improving my slope flying skillz, especially for F3F, to witch I'm dedicated too
(the one with the red nose we have to put out of the discussion). I tried to figure out which fuse suits better to me.


If I'm following your thread heading, is your statement that good and ugly can not be compared with fluid dynamics and windtunnel testing of how a model plane should look like? Purely not subjective, as finest forms of laws and rules within the art of mathematics, set into GO with computational derived iterations of how it can be, as it be...good bad ugly and not GRU like

This is what the translator puts back when I re-translate: Wie messen wir? Sind Gleitverhältnisse von beispielsweise 1:50 für ein Modellflugzeug gut und für ein maßstabsgetreues Modell ein ziemlich schlechtes Ergebnis?
the translated:

How do we measure? Are gliding ratios of say 1:50 for a model plane good and for a full scale a pretty bad result?

So full scale = 1:1, I god it now!

 

[Konrad]

model plane fuselages are designed without cockpit and pilot. unmanned aerial vehicles can therefore designed with slim fuselages.

So why are there planes (model planes) with high volumes of fuselage diameter in front of the wing? Especially your example of an oldskool Sagitta from simprop has such a fuselage. Despite it it also has a less than 90° wing to fuse angle. That is what Konrad states as as not performance improving during flight, as so as the section of the wing root that is decreasing by diameter. Therefore not good for performance.

Konrad, here are my testing plattform planes for improving my slope flying skillz, especially for F3F, to witch I'm dedicated too
(the one with the red nose we have to put out of the discussion). I tried to figure out which fuse suits better to me.


If I'm following your thread heading, is your statement that good and ugly can not be compared with fluid dynamics and windtunnel testing of how a model plane should look like? Purely not subjective, as finest forms of laws and rules within the art of mathematics, set into GO with computational derived iterations of how it can be, as it be...good bad ugly and not GRU like

This is what the translator puts back when I re-translate: Wie messen wir? Sind Gleitverhältnisse von beispielsweise 1:50 für ein Modellflugzeug gut und für ein maßstabsgetreues Modell ein ziemlich schlechtes Ergebnis?
the translated:






So full scale = 1:1, I god it now!

Still not clear. But I'll try to cover some points.

First a lot of this is dictated by fashion. Folks like to buy model planes that look like full size planes. As a manufacture, sales is the name of the game. So we see a lot of bulbous noses.

The second reason is that in the old days radios where rather large. So we needed a lot of space to house the RX, Servos and Batteries.

That RED nose is a good one to use as an example of the issues with control, and stability as it applies to drag. It is my understanding that the designer saw an issue with how slope planes tracked across the face of the hill. So to control this he added a lot of side area to the front of the nose. So far so good. Unfortunately the laws dealing with stability and control runs counter to this idea. Flight dynamics has shown that adding front side area to an aircraft has a destabilizing effect. This needs to be countered with a lot of drag inducing vertical area in the rear.

I have to salute him for putting his money on this crabbing theory. Unfortunately it did not pan out.

This fuselage also is trying to address the feeling that we need to add far too much mass in the nose to get proper fore and aft CG. Again adding a long nose at first glance would look like a simple solution. Again unfortunately physics again raises its ugly head and introduces the concept of mass coupling. (This has bested many great minds, Ref. the USA X-3 experimental aircraft and MacCready's Gossamer aircraft*). It is because of these two problems that we almost never see a nose as long as the tail.


And No, The Good, The bad and the Ugly are directly tied to fluid dynamics and wind tunnel testing. This is not an esthetic judgment call.

As to what to get, I can't really say. I love the Shintos and the Freestylers. But these are a bit dated. I think just about any of the newer 4 year or less models that have come on the market would be great.

Now there is a new ship coming that I think will be a game changer. The designer has added a lot of what was learned with that Red fuselage to his great wing. If you liked how that wing performed I'd think it best to save your money and wait for this new ship to come on the market.

* The mass coupling of the Gossamer Albatross had to do with the long wings. Again this is a force that the verical stabilizer needs to deal with in high aspect ratio wings. This is why the V-tail angle is coupled (tied) to the aspect ratio of the wing.

 

[Wayne]

I know what Konrad has on order...

 

[Konrad]

Not that what I order means anything!