Author Topic: High Aspect Ratio Wing (Read 3937 times)

Bill Gruby · « **on:** May 26, 2007, 01:13:18 PM »

OK Everyone who knows;

If I am the only one in the dark here so be it I'm asking anyway:

What exactly is a "High Aspect Ratio Wing" and how does it differ from conventional wings? By conventional I mean the ones we always use. What does it do "Performance wise"? This is not a trick question, I DON'T KNOW AND I WANT TO. I hope that covers it enough to get some kind of answer?

"Billy G"

EDIT If someone knows a site that I can access to get the info I want please post it. Thank-you

don Burke · « **Reply #1 on:** May 26, 2007, 01:35:29 PM »

The aspect ratio is the span squared divided by the area. Or the span divided by the average chord for a straight tip planform.

The '57 Nobler with a span of 50.5" and area of 550 sqin has an A/R of 4.6. Anything higher than this would most likely be considered high A/R.

Bill Little · « **Reply #2 on:** May 26, 2007, 01:36:32 PM »

Hi Brother! AFAIK, I don't know of a site that covers it, but I'm sure there are some.

The "lower" the aspect ratio, the wider the chord is in comparison to the wingspan. So a "higher" aspect ratio is one where the wing is skinnier in chord compared to the wingspan.

It is the ratio of chord (average chord??) to wingspan.

From Randy Powell's remarks, and others, the wing is easier to turn the higher the aspectr ratio, but it's more likely to bounce in turbulence.

Pretty technical there, huh??

EDIT: Whilst I was typing, so was Don!

I would go with his info, but I was close...............

Bill Gruby · « **Reply #3 on:** May 26, 2007, 02:26:46 PM »

Don and Bill;

If I have this correct this is what I have right:

Wing Span = 82 area= 1072

82 X 82 = 6724 / 1072 = 6.27 Aspect Ratio

If I am correct is it good or bad?

"Billy G"

Tom Niebuhr · « **Reply #4 on:** May 26, 2007, 02:41:35 PM »

Bill,
That is correct.. What are you building with an 82" span??

Where are the P-38 pictures?

Bill Gruby · « **Reply #5 on:** May 26, 2007, 02:56:45 PM »

Thank-you Tom;

Now second half of the question please is this good or bad. Maybe you need more info? What I am building is still in my head, and Pat Johnston is standing by. I gave him some sketches and we are working it out. sorry thats all I can say right now cause things change as we are going along. If I pull this one off-----------?
I will get pictures together this week and send them to you at "Blue Sky Models" You may do with them what you wish OK

"Billy G"

frank carlisle · « **Reply #6 on:** May 26, 2007, 03:28:06 PM »

I prefer a short stubby wing for my airplanes rather than a long narrow wing. The low AR wing turns just right for me and it doesn't pendulum like a high AR wing.

I would say that how and what you are applying your numbers to will determine how successful the project is.
Lots of the guys on the forum use the IILR system. And the application of IILR seems to work in most cases.

Bill Gruby · « **Reply #7 on:** May 26, 2007, 03:42:02 PM »

If I am reading all of you right then there is no real advantage to the higher ratio? Correct? In all actuality whatever you come up with you live with. IILR-----If It Looks Right?

"Billy G"

Bill Little · « **Reply #8 on:** May 26, 2007, 03:44:19 PM »

Quote from: Bill Gruby on May 26, 2007, 03:42:02 PM

If I am reading all of you right then there is no real advantage to the higher ratio? Correct? In all actuality whatever you come up with you live with. IILR-----If It Looks Right?

"Billy G"

If it looks right, or more commonly, TLAR. That looks about right. Same same.

I believe what you are doing will be just fine.................. and no, I ain't tellin'! LOL!!

Bill <><

Bill Gruby · « **Reply #9 on:** May 26, 2007, 03:56:35 PM »

"Billy G"

Are you sure you know?

Bill Little · « **Reply #10 on:** May 26, 2007, 03:57:26 PM »

Quote from: Bill Gruby on May 26, 2007, 03:56:35 PM

"Billy G"

Are you sure you know?

Know WHAT?

?

Bill Gruby · « **Reply #11 on:** May 26, 2007, 04:14:27 PM »

"Billy Boy";

Your words "and no, I ain't tellin?" Must mean you think you know sumthin, but are you sure what you think you know is what I know or are you ------------------------------THINKING WHAT I AM THINKING? Or maybe you are over thinking, all this thinking is givin me a "HEAD ACHE", so I think I will stop thinking for a while. I Think I got it all in here?

"Billy G"

minnesotamodeler · « **Reply #12 on:** May 26, 2007, 07:59:14 PM »

The higher the aspect ratio, the more efficient the wing --to a point (everything has its limits). A high-aspect wing will produce more lift with less area than its opposite. As was mentioned, think soaring planes, etc. Maybe you want that; maybe you don't. I think a low-aspect wing is probably more forgiving on trim, adverse conditions, etc.

I experimented with high-aspect combat wings in the 60s (so did a few hundred others, I think). it would turn really nice, but I never found a clear-cut advantage, and the construction was always a booger making it tough enough to hold up to the turns.

--Ray

Bill Gruby · « **Reply #13 on:** May 26, 2007, 10:57:17 PM »

Ty and Ray;

Thank-you both for your input. Now Ray my above figures are in error, the Aspect Ratio should be 5.67 : 1, That should be about the right number correct?

"Billy G"

Arch Adamisin · « **Reply #14 on:** May 27, 2007, 12:03:10 AM »

Guys,
What kind of trim problems are we talking about? We've models with aspect ratios ranging from 6.2 to 7.7 and haven't had any problems what so ever trimming any of them. Maybe we flew them too nose heavy and that condition eliminated some of the trim issues. Most of our models were balanced about 25% MAC to start with and then adjusted to get the right feel.

Arch

minnesotamodeler · « **Reply #15 on:** May 27, 2007, 06:40:27 AM »

The most successful combat wings I played with went up to 8:1 AR (6" chord x 48" span). By the way, simplest computation is span divided by average chord. Bill, your first figure is correct if the numbers are right (82" span, 1072 sq. in. area--82x82=6724, /1072=6.27 MOL). I tried more extreme versions with decidedly mixed results. One thing such wings tend to is shorter nose/tail moments, otherwise they start looking like a dragonfly or something. I found them much more sensitive to very small CG changes, such as running your fuel load out. Warps were magnified. Crosswinds could be adventuresome. LO guide location was critical. But when all was just right, boy could they turn! And glide forever.

--Ray

Bill Gruby · « **Reply #16 on:** May 27, 2007, 07:18:14 AM »

RAY;

My computation for "Wing Area" was off? (Dumb mistake) It should be:

Wing Span 82"

Wing Area 1184 sq. in.

Now it's 82" X 82" / 1184 = 5.68 : 1

This is better right? I'm gettin better at this stuff. "Billy G"

Alan Hahn · « **Reply #17 on:** May 27, 2007, 08:00:18 AM »

If you look at some of the RC combat planes, the aspect ratio looks pretty high to me. And those babies are looping all over the sky. They aren't much for rolling due to the high moment of inertia about the longitudinal axis (but that is something we don't normally do in CL!). The problem with the high AR wing in CL is (I guess) the long lever arm that the long wing provides. On the inboard, the control lines can exert a strong torque and in general, a gust of wind can roll the plane pretty easily.

I don't think there is a lot of science in CL, but there is a lot of past experience, which probably indicates that the high AR isn't going to work out ---at least not in some vastly superior way to what we have. But there is always that tantalizing feeling that perhaps just maybe something may be there which hasn't been explored yet.

minnesotamodeler · « **Reply #18 on:** May 27, 2007, 12:28:08 PM »

Alan, I think you're exactly right. Seems like aerodynamics, at least at the CL model level, is much more an art than a science, with experience being the key factor--simple reason, it's easy, safe and inexpensive to build a model and try something new. It's not like we have to climb inside our creations and trust our lives to them (good thing, too).

Unique thing I see is, we can't control our relationship to the wind like untethered planes can--have to go through every phase, every lap. So our designs have to fly well in a headwind, in a tailwind, in a crosswind, 3/4 or 1/4, etc., all at once, no trim adjustments allowed between. Low AR wings seem more forgiving of changing conditions like that. That old Nobler at 4.6 AR is I guess a supreme example. But I do love to experiment!

The really interesting thing I've found, at least for me, is that a LITTLE wind is beneficial--I find it more difficult to fly in a dead calm than about any other condition. For one thing, I can't figure out where to put the maneuvers. Then there's the "hitting your own turbulence" phenomenum. And since I learned to fly in Okla., maybe I'm just more used to flying in wind than not.

--Ray

PatRobinson · « **Reply #19 on:** May 27, 2007, 12:33:33 PM »

Bill,
A higher aspect ratio wing improves a wings lift to drag ratio which means it is more efficient than a lower aspect ratio wing which results in in some of the flight characteristics good and bad that have been discussed. When you make your wing longer you also change it's "Span Loading" which is the ratio
of a planes weight to the wings length. This is usually expressed in ounces per foot. I recommend reading Dennis Adamisin "Eclipse" article in Flying Models for his discussion on span loading. Span loading is more efficient because as the longer wing move through air it has more available molecules of air to work against than a shorter wing so it can carry a heavier load. Please note, if you build a big enough low aspect ratio wing you can also increase its span loading without increasing the A/R. You will also probably improve it's Reynolds number ( some times called scale effects). You can Google Reynolds number and find out more than you want to know but to simplify it for this discussion the wider the wings chord the higher it's Reynolds number. Most conventional stunt planes Reynolds numbers are in the 250,000 to 300,000+ range at 50-53 mph and the number for a given chord will increase as the speed increases say up to 55-59 mph.
Now Bill let's plug all this in so it can make some sense for you. If you intend to fly a plane at a given speed and you are going to build a wing of a given area then,if you increase the aspect ratio then you are going to reduce the chord of the wing and especially the tip chord and if you reduce the tip chord too much then the airfoil effectiveness can be reduced which may lead to the tip stalling or causing trim problems. so Bill, a designer needs to balance aspect ratio and Reynolds number when creating his wing. Fortunately, problems with low Reynolds numbers are infrequently talked about on stunt planes.
Bill, I reccomend that you go to the Design forum and read the Randy Powell and Dennis Adamisin thread for a lot more detail about all the high aspect ratio airplanes they built and the results they had with them.
It's very informative. I remember years ago that I had conversations with Dennis Adamisin and with Windy "U" who were each flying high aspect ratio wing airplanes at different contests and in different years but each of them gave the same answer to my question about trimming high aspect ratio wings.
"Yes it takes more work to trim a high aspect ratio wing airplane than a low aspect ratio wing airplane but the result are worth it to me and I am always
trimming and fine tuning my airplanes anyway so it really doesn't matter."
Well Bill, I hope this helps your understanding a little more without overloading the brain cells.

Best Wishes ,
Pat Robinson

Bill Gruby · « **Reply #20 on:** May 27, 2007, 01:24:43 PM »

Thanks Pat, allen, and my amiego Ray;

So far so good, I understood perfectly Pat. I am going to search for the threads you mentioned and see where they take me. Ray you are right experimenting is fun, this new one is starting to look better all the time.

"Billy G"

It would seem, "The Game Is Afoot"

Randy Powell · « **Reply #21 on:** May 28, 2007, 12:30:13 PM »

There was an extensivbe discussion on this in the Design area. I won't go into it again. As said above, there are good and bad points. Lift potential of the wing is better with high aspect ratio but some problems have to be overcome. It's like any thing else, I suppose. Every thing is a trade off.

Bill Gruby · « **Reply #22 on:** May 30, 2007, 04:54:30 AM »

One last question?

I have a little knowledge now having read the other threads in the Design Section. All the discussion here has been based on the "Nobler" ratio of 4.6:1, what happens, if anything, if you go below this ratio? Say 3.8:1?

"Billy G"

don Burke · « **Reply #23 on:** May 30, 2007, 10:37:08 AM »

Check out the Netzeband "DOODLEBUG" series. RSM has kits.

minnesotamodeler · « **Reply #24 on:** May 30, 2007, 01:02:17 PM »

You get a "trick" airplane that will out-slob the BiSlob: Hang on its prop, flop over within its own length, etc. Basically a flying stall. Lotsa fun but little practical value.

I saw a "combat" wing one time, forget what it was called, whose chord was bigger than its span, I guess the ultimate in low aspect ratio. Its claim to fame was that it turned so tight it would "cut its own streamer", a fact demonstrated several times. Of course it did it by stalling and flopping over backward into the streamer, a technique seldom useful in the combat circle...

--Ray

Dennis Adamisin · « **Reply #25 on:** May 30, 2007, 07:34:16 PM »

I have purposely stayed out of this thread, to see what course it would take. Its no secret where I would weigh in on the subject, but that is really not important.

I want to make a suggestion to anyone who wants to gain aspect ratio and marginally improve their span loading in a no risk "cheater" way without changing wingspan on your classic bird: sweep back the wing tips ala Shark 45, Fancher-everything, or even Adamisin-Eclipse.

What this does is encourages the trailing vortex to stay outboard a little farther. The farther out this shed-air is the longer the effective wingspan, even if the ACTUAL wingspan does not change.

CASE IN POINT: Lets take the Cardinal, as an example of a modern but classic styled bird that most have seen or are familiar with. The "Classic" shaped wingtips allow the air to exit the wing roughly 3" INBOARD of the max wingspan point near the leading edge. If the Cardinal tips were reversed (and slightly reshaped for aesthetics) the air COULD exit the wing roughly 3" further outboard than it does now - thats in essence a gain of 6" wing span without actually CHANGING the wing span.

See pix of the last "Nobler" winged bird I built, in 1969. These wing tips were the same span as the Nobler but this wing would fly more efficiently than a Nobler because of the swept tips.

Want some empirical proof? Go visit your local RC sailplane field and see how many "classic" wingtips you see! Those folks LIVE for high AR and EFFICIENCY, and grab every opportunity they can...

proparc · « **Reply #26 on:** May 30, 2007, 07:59:12 PM »

Dennis, what do you look like now? Do you look like Bob Lampione lol. Or Jack Sheeks? Do you have kids and if so, do they steal your contest grade wood?
And, what are your plans for building a new ship and do you have enough pull to convince Dawn Cosmillo to get back into it and join us?

It's great to see you back.

Dennis Adamisin · « **Reply #27 on:** May 30, 2007, 08:50:16 PM »

proparc:
What do I look like now-funny you should ask. I was in the hospital today visting my Mother. The Nurse came in and asked if I was her BROTHER.

Worse yet, there were WITNESSES

Jack Sheeks just keeps getting better - I think he must have one of those paintings up in the attic.

Have not seen "Champoine" since the early 1970's or so. Bet he is still his studly self!

I remember seeing Dawn fly, but that's about it. Besides, she was like the Prom Queen and me the geek with the white socks! Cannot imagine I carry much clout there...

Gordon Tarbell · « **Reply #28 on:** May 30, 2007, 09:47:02 PM »

What about the addition of spill plates on the wing tips (ala one of Al Rabes early F-8's) and elevator/stabilizer assembly? Would that work as well as the flaired wintips?

Randy Powell · « **Reply #29 on:** May 31, 2007, 02:09:54 PM »

Another way to go is what Eather did with his Firecracker. Very wide at the root chord and highly tapered wing with fairly narrow chord at the wingtip effective lengthing the span without the structure.

I agree on the tips. Makes a difference.

Bill Gruby · « **Reply #30 on:** May 31, 2007, 05:02:39 PM »

Wow;

The knowledge here is fantastic. My original question was answered to my satisfaction quite a ways back. Now Dennis has seen fit to add something I never would have given a thought to, "The Wing Tips". Thank-you Dennis.

Now Randy jumps in with the "Tapered Wing" again something I would not have given any thought to. Thanks Randy.

"Billy G"

Dennis Adamisin · « **Reply #31 on:** May 31, 2007, 05:35:04 PM »

Billy G:
Not only that but I see about half way through the thread you learned how to calculate ASPECT RATIO!

Gordon:
I have no direct experience with tip plates - really should not comment about them. They are still on the un-done experiments list!

Have also never tried a highly tapered wing like Randy mentioned - though it obviously works for Brain E! Biggest risk to worry about with high taper ratios is that tip stalling becomes more likely.

Bill Gruby · « **Reply #32 on:** May 31, 2007, 06:20:49 PM »

Dennis;

Again Thank-you, I am a retread of a different kind I guess? I am not trying to reinvent anything, I just feel that after all this time, it's time to know why things do what they do. I have taken these things for granted much to long."Dang" I hope that made sense, it was supposed to. I am asking all this because after all these years I am going to start flying competition for the first time, local level for now but who knows?

"Billy G"

don Burke · « **Reply #33 on:** May 31, 2007, 07:52:53 PM »

The rule of thumb for tip plates is to make them a Chord thickness bigger all the way around to get the desired effect, elimination of "spillage" from top to bottom due the difference in pressure. i.e. a 1" thick wing would have a 3" high plate. Not very pleasing appearance IMO.

Author Topic: High Aspect Ratio Wing (Read 3937 times)

Alan Hahn