OK- you tell me why it works -using wind tunnel data .
Believe it ot not you don't need tunnel data to make something work.
Lots of stuff that was designed by wind tunnel research turned out to be a flop.
NOT because of the tunnel - simply because real world use shows up flaws that paper work and controlled enviroments don't/ can't / never will.
Tunnels beat guesswork - I am not a fool.
I never alluded to any explanation of why the stuff works - simply that it does work-
You have to do actual hands on stuff , eventually .
Where are you going to get a tunnel which runs at 10 mph airflow ?
I guess they exist - I don't kno who uses em tho -
You really don't think light weight broadens usable CG range?
Lower loadings = lower angles of attack needed to provide same amount of lift.
So the craft can maneuver at lower angles of attack and will recover to lower angles of attack that is, recover from departure conditions (stalled ) much more readily.
This is not a true statement?
Take any powered plane - fly it - now add weight - keeping speed the same - and see if you can't find the same effect.
eventually it will stall and never take off.
How does lower loading increase CG range ?
It simply reduces the critical nature of the cg --control can become pretty ham fisted in fact .
Attempts at exceeding stall angle have to be really intentional -as opposed to the typical full scale design which must be carefully kept with in the "envelope".
stability can be traded for maneuverability .

Dick,

In this post, you say that 'you never alluded to any explanation of why the stuff works', but just a couple posts ago you said: "I do try to explain why my stuff works".

I don't think that low wing loading broadens the stable CG range. I have already said that it may broaden the usable CG range by making an unstable or barely stable plane flyable, due simply to the lower airspeed at which it can fly. However, your statement with which I took issue originally, and still do, is that "if a plane is light enough, CG doesn't matter". That is a different statement, and is particularly unaccaptable in a beginners' guide to aerodynamics.

Flying at a lower angle of attack does not give a broader usable range of CG locations. Nor is recovery from stall what stability is about. Is that your explanation?

banktoturn

Dick, as I said, micro UAV research is quite active, but even when doing "normal" low Reynolds number research the tests are frequently done at tunnel speeds below 10 mph. The setup I have the most personal experience with usually operates between 6 and 35mph, although we have tested at even lower speeds.

Great! -So - I would guess you have tested designs using very low loadings at very low speeds ?
sound like a natural for "loitering " stuff.
I have to cut and try to see what is going on.
Is there data on craft having loadings of aprox 5 oz per square ft flying at 10 mph?-20 mph?
Tunnels really don't show how wing loading enters in tho -does it ?
only angles of attack?

and

Tunnels give you information on drag, lift and pitching moment coefficient. It is not dimensional, so it is valid for any wingloading as long as the Reynolds numbers tested fit into the flight envelope of the actual vehicle.

As for what are actually built for micro UAV research using the data obtained from the tunnels - loadings differ, but the very low loadings are not very interesting since, as I explained in the first post, they have a very definate size limitation. As equipment gets smaller and lighter, instead of lowering the wing loading the tendency is usually to make the aircraft even smaller. Physical sizes for those that actually fly are typically between 12" and 6" wingspan, although they are always trying to get even smaller and I wouldn't be surprised if someone such as the guys from AeroVironment have actually flown something smaller than that.

I understand.

Dick,
Everybody knows that by reducing the wingloading will reduce the stall speed - that's just part of the old "hard" rules, which you don't seem to appreciate so much…
But, since an airplane rotates about its centre of gravity, it either flies or dies depending on its CG location…

Uh???

Luis

You know -- it's one thing to know where to look up rules -
It's quite another to learn how to apply/ massage/ modify them.
Don't evaluate me .
You really don't know what I appreciate.

You are unnecessarily arrogant (and WRONG)
I think I will hang around other forums and with other more open-minded and humble individuals, and not waste my time in this thread
Luis R. Urbina, MD, FCCP

thank you for your unsolicited testimonial.

Maelstrom,

It ain't bragging if you can do it. Dick Hanson.......arrogant? Perhaps.
Dick Hanson.......extremely knowledgable??......... undoubtedly; and he can
certainly do it, and has...... repeatedy. At times you must reach carefully past
the sharpest thorns to pick the prettiest rose.

Chuck Earnest

PS:
I just hope Dick Hanson is not a commercial airline pilot, where CG does matter. He has the arrogant attitude that results in aviation fatalities. Regardless of how much he may know, he is conveying the wrong message for those who don't know as much or have his experience. For those of us who live in the real world CG is extremely important. When you are flying a model airplane you better set your CG within a range that allows you to control it properly. Sure if you have a more powerful engine you can get away with a totally unconventional CG, or if you have extremely large control surfaces (depending on which way you are moving the CG), but from there to saying that CG is irrelevant is a dangerous stretch.
And, Chuck, don't stick up for him. Arrogance is not kosher. No matter how much you know. Actually, the more you know, the more you realize how little you really know. And if that doesn't make you humble nothing will. There is something called narcissism, and it is not a flower.
Luis

Luis,

With all due respect; do not set youself up as an expert as to who I should "stick up" for or who I should not. Also, I do hope you realize that there have been many lives lost in developmental aviation by those who "push the envelope". I dare say that most non-experimental aviation fatalities occur not because of unknown factors, rather know factors which are ignored. I, personally, would fly with Dick or in any aircraft of any flavor he cares to design and build. Just for the record, I was a pilot until I lost my medical cert. and have been involved in model aircraft since the middle 1950's. I am somewhat familiar with both sides of the coin. I am sure that all the advances in any endaevor one might name were not made by perfectly "balanced" (by everyone's standards) individuals. I do not think that discovery is tied to personality. If it were, we would still be sitting in caves, beating on a rock, and complaning that "we ain't never going to have television".

This thread seems to oscillate from theoretical areodynamics to the practical side of things, depending upon which sacred cow the posters are trying to worship. If one is to learn, one must look past the labels, personalities, prejudices, and any other perceived personal faults of either the student or teacher. If one digs through a pile of cow poopie, he is likely to find the seed of a tree. Years ago, I attended an event called "solo de-brief". It is held as each class of Naval Aviators at Naval Air Station, Corpus Christi, Texas, complete their solo flights. You could not, generally speaking, find a more cocky,
self-assured, and yes, some might say arrogant, group of people if you had three months to look and an unlimited expense account. Thank God for them. I only mention this to say: Do not discount self-assurance and the ability to "do it" as arrogance, which in itself is not necessarily a bad thing.

Sense of humor.......... one of the most effective offenses or defences one can possess. Hmmmm......? Narcissism; now we are branching out into psychology......... I don't think this thread is long enough. I'll just take your word for it that narcissismis not a flower. Sure sounds like one, though.

Regards to all.

Interesting group of people
The point I was interested in is in CG on extremely lightly loaded airframes
My finding was that cg really is not critical on these highly powered lightly loaded models.
My statement " if it is light enough CG does not matter" really offended some
Why?
I get name calling.
I respond -
more name calling.
I really expected better .
Solch ist das leben.
This is not a good way to handle any debate or discussion - especially from those who post their "letters" after their names.
Just to put certain individuals at ease -
I have never advocated willy nilly cg placements for the conventional airframes .
Also, have models which will trim and fly as free flights (Seniorita, for one) on low power.
Spent lots of time setting up planes for those new to the hobby.
My thought was to encourage discussion on rather new approaches to models - not be condemned for scratching the sacred cows of some reader.
To the true professionals who responded - thank you .
I ain't mad - not even hurt -
just a bit disappointed.

Ok Dick, maybe your intentions have been good, maybe you've just been misunderstood….
Finally, I just like to put a simple question:

Is there any case in the real world where an airplane's CG doesn't matter?

Perhaps, after the crash?

For those of us who know Dick, we would probably characterize him as intelligent, innovative, resourceful, quick-witted, thought provoking, open minded, and fun to be around. I'm sure others that know him better than I could add even more. FWIW, I am proud to know him and consider Dick both a friend and mentor. I do not consider him arrogant, self-admiring or egotistic...I hope in time others will see him in the same light.

As for CG placement on the foamies I've found that the vertical position of the CG plays a large part of my opinion of their handing qualities. I find that making sure that the thrustline passes through the CG eliminates large pitching and yawing moments with power changes. I continually tweak the thrustline and battery position until I'm happy with it. Also I found that things we never really see on normal aerobatic models like gyroscopic precession and prop normal force have a lot to do with the stability and control (S&C) of the foamie. Originally (before good batteries light strong materials and small equipment) we had to use very large props and small airframes to obtain hovering thrust. On some of my original designs I had 14" props on 30" span models. What was funny was doing knife edge passes with zero rudder deflection because the moment generated from the prop normal force balanced the directional stability. Once the weight of the models was reduced we could run smaller props and get rid of these prop effect issues. The only other time I'd seen prop normal force be significant enough to cause real S&C problems was on flying wing UAV's. I find these models very interesting from an S&C viewpoint. I also feel like they 3-D better than my 40% aerobats but seriously lack the precision that you can obtain with a larger model...I hope to change that eventually.

All the best,

George Hicks

Well --- I am not sure -
On full scale stuff like airliners absolutely CG is very important - When I started travelling a lot - we frequently had to "move to the front , please --".

But just take a real look a t a extremely lightly loaded , highly powered plane -these types act very indifferently to cg .
Why?
take the "impossible" plane which weighs nothing -bu is say - 500 sq inches--
There is no inertia if it weighs nothing - so control inputs simply have to keep it flying at angles whch do not exceed stall.
Impossible?
OK let's make it weigh a gram - now it is heavier than air .
again inertia is extremly low making it still very controllable even with the entire 1 gram situated at the rear.
I thought some guys who were into abstract thought ,would see that .
Too heavy - cg is of no value
absolutely - why bother
My point was -- fix the real problem .
I certainly did no expect some of the comments I got -
but I asked for it . Should have seen em coming.
Hving read some other threads on really odd tstuff - I thought this would be fun.

And apparently it's important for reasons having nothing to do with longitudinal flying qualities...

..........................and the well thought-out, informative, well-meaning comments just keep on a' commin'..........

We are amused.........


C. Earnest

If one digs through a pile of cow poopie, he is likely to find the seed of a tree and may be able to build a house or just a model airplane, in case the tree is of balsa...
But CG or not CG is still the question.
Sense of humor is one of the most effective offenses or defences one can possess...

adam_one.

aaaaaaaaaaa-men.

C. Earnest

C Earnest,

What does "CV in sight" mean?

Shoe,

It's a phrase near and dear to a Naval Aviator's heart:

CV (carrier) has been sighted...

BTW, are you the same "Shoe" that used to be in the JEFCO group? If so,
do you lstill have that beautiful D.F. F4 "Playboy" jet black Phantom?

C. Earnest

PS: I think that perhaps it may be time for a new tag line........

That's what I thought. How many traps?

Different Shoe