Plan form of RC WINGS

[Texas Buzzard]

Those of you who have been into RC for a while might recognize the name Randy Rudolph. He was from Dallas,Texas and he died just a very few years ago. He was a designer-contest flier- and a cool guy.

Several times a year his designs were published in various modeling magazines. "Flying Models" publish aproximately a dozen of his designs.

Later in his life his RC designs were usually small - 0.15 cu in glow or smaller. He was the Guru of the 0.049RC clan.

HERE IS WHAT THIS THREAD IS ABOUT - - -IT IS ABOUT WING PLAN FORM.

Randy Rudolph said a number of times that "THE WINGS OF POWERED RC PLANES SHOULD HAVE A WING THAT IS NON-TAPERED.THE ELLIPTICAL PRETTY-PRETTY TYPE ARE FOR SHOW - NOT FLYING.

RANDY HAD LOTS OF EXPERIENCE. HIS DESIGNS FLEW WELL. HIS WINGS HAD PARALLEL LEADING AND TRAILING EDGES. ( THEY WERE RECTANGULAR)

i WOULD HOPE THAT SOME OF YOU WITH SOME EXPERIENCE WITH VARIOUS PLATFORMED WINGS WOULD THROW OUT SOME COMMENTS.

WAS RANDY CORRECT WHEN HE SAID," TAPERED WINGS ARE FOR BIRDS, SAILPLANES AND FIGHTERS. The RC POWERED MODEL WILL FLY "BETTER" IF IT'S WINGS ARE SQUARE TIPPED AND OF AN ASPECT RATIO CLOSE TO 6 + -1.
whatduyousay?

[nmasters]

I say blanket statements are always wrong ;)

--Norm

[vintage1]

Could not agree more.

Aspect ratio and thickness and camber and washout are far more relevant to most designs than exact section or planform.

Elliptical is marginally better for speed. That's all. Straight taper nearly as good.

[JetPlaneFlyer]

Define what 'fly better' means and maybe you will get a sensible answer.

Some possible definitions of 'fly better':

Fly Faster (in a straight line)
Fly Faster (round turns)
Fly Slower
Aerobatic performance
Maximum duration on lowest fuel/battery consumption
'Safe' handling

What do you want :confused:

[vintage1]

What do you want :confused:

Tartan covering film? :D :D

I'll get my coat...

[Brandano]

I say blanket statements are always wrong ;)

--Norm
Lovely, but the smiley somewhat spoils it.
That said, I am forced to disagree on principles alone :)

[banktoturn]

Those of you who have been into RC for a while might recognize the name Randy Rudolph. He was from Dallas,Texas and he died just a very few years ago. He was a designer-contest flier- and a cool guy.

Several times a year his designs were published in various modeling magazines. "Flying Models" publish aproximately a dozen of his designs.

Later in his life his RC designs were usually small - 0.15 cu in glow or smaller. He was the Guru of the 0.049RC clan.

HERE IS WHAT THIS THREAD IS ABOUT - - -IT IS ABOUT WING PLAN FORM.

Randy Rudolph said a number of times that "THE WINGS OF POWERED RC PLANES SHOULD HAVE A WING THAT IS NON-TAPERED.THE ELLIPTICAL PRETTY-PRETTY TYPE ARE FOR SHOW - NOT FLYING.

RANDY HAD LOTS OF EXPERIENCE. HIS DESIGNS FLEW WELL. HIS WINGS HAD PARALLEL LEADING AND TRAILING EDGES. ( THEY WERE RECTANGULAR)

i WOULD HOPE THAT SOME OF YOU WITH SOME EXPERIENCE WITH VARIOUS PLATFORMED WINGS WOULD THROW OUT SOME COMMENTS.

WAS RANDY CORRECT WHEN HE SAID," TAPERED WINGS ARE FOR BIRDS, SAILPLANES AND FIGHTERS. The RC POWERED MODEL WILL FLY "BETTER" IF IT'S WINGS ARE SQUARE TIPPED AND OF AN ASPECT RATIO CLOSE TO 6 + -1.
whatduyousay?

Randy was incorrect. Untapered wings do not have the lowest induced drag, or the highest roll rates, or the best lift distribution for the lightest wing structure. For an RC plane for which any of those things matter, a tapered wing may very well be better. An untapered wing is simpler to build, and less likely to suffer from tipstall, which may lead some to conclude that it's 'best'.

banktoturn

[Texas Buzzard]

Define what 'fly better' means and maybe you will get a sensible answer.

Some possible definitions of 'fly better':

Fly Faster (in a straight line)
Fly Faster (round turns)
Fly Slower
Aerobatic performance
Maximum duration on lowest fuel/battery consumption
'Safe' handling

What do you want :confused:
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Jetplane flier asked a question. Did he notice that in my "original" post I had quotaion marks around the word BETTER?
I think this is what we see in the original post.""WAS RANDY CORRECT WHEN HE SAID," TAPERED WINGS ARE FOR BIRDS, SAILPLANES AND FIGHTERS. The RC POWERED MODEL WILL FLY "BETTER" IF IT'S WINGS ARE SQUARE TIPPED AND OF AN ASPECT RATIO CLOSE TO 6 + -1.""
These were RANDY"S WORDS from a magazine article.....and YES I too wondered what Randy was thinking when he made his statement. We will have to guess based in WHAT TYPE OF FLYING RANDY WAS DOING. IT IS AN EDUCATED GUESS.
I have seen Randy fly two times. Both times it was a Fly-In. We had a few Fly-In TYPE of compititions such as 1. How many touch and goes done in a TWO MINUTE TIME LIMIT. 2. SHORTEST Dist. FOR Lift off. 3. Maximum No. of Loops in Two min.Total for T.O. ,Loops and LANDING. That kind of flying was the usual.
Randy was never a winner but he was up ther in the top one third. So JetPlaneFlier can determine the manuvers we are talking about. Nothing Exotic at all but TO ME it seems these manuvers were what the ordinart pilot at my field does roitinly. Climb, hard oe sharp turns, loops, T.O and landings.
***** This is my additional comment.***** When I am thinking about Randy's planes and how they fly it seems they do the ordinary flight manuvers as well and as Safely as any other wing. They don't TIP STALL like the Spifire Planform wing ( Pointy or Eliptical wing) does when opening throttle at very slow speeds.
So JetPlaneFlier asked for a DEFINITON of "BETTER". IMHO,Randy meant that the Square Tipped Wing avoids Tip Stalls. Here let me "define" my use of the word Tip Stall; My usage of the term is from my experience.
Lets say you have a ship with a wing loading of More that 16 oz/sq. ft.
It has a wing of an exagerated taper OT it looks like a Spitfire wing (eliptical) . You are landing and on final you are "dragging" it in. You see you know you have to "go around".[/B[B]] You advance the throtle suddenly and the plane makes an unwanted manuver- uh, oh - your in trouble. Nest pa?
Randy's plans and planes were designed for the novice or average fliers. t's my opinion that he knew he needed to provide a bullet-proof design for them; therefore, his affinity for the square tip had a reason behind it.
Good eye, JetPlaneFlier. You recognised the word "BETTER" forced you to ask - - -"Better for what".

[JetPlaneFlyer]

Buzzard,
Randy had a very valid point for the type of flying he did i.e. general fun/sport flying where outright performance is second place to safe and predictable handling... No point having the highest performance model out there if you take it home in 100 pieces ;)

To be honest, aerodynamic considerations aside, the main issue I'd have with parallel chord wings is that they don’t look as nice as a tapered wing (to my eye anyway)... A very subjective and non scientific reason I have to admit.

Steve

[vintage1]

Frankly I can't think of anything that a parallel chord wing is good for, other than ease of building.

[JetPlaneFlyer]

Frankly I can't think of anything that a parallel chord wing is good for, other than ease of building.

Safe stall ?

[Texas Buzzard]

JetPlaneFlier , "Buzzard,
Randy had a very valid point for the type of flying he did i.e. general fun/sport flying where outright performance is second place to safe and predictable handling... No point having the highest performance model out there if you take it home in 100 pieces

To be honest, aerodynamic considerations aside, the main issue I'd have with parallel chord wings is that they don’t look as nice as a tapered wing (to my eye anyway)... A very subjective and non scientific reason I have to admit."
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I agree with you 101%. Yes sir, for everyday flying Randy's wing will suffice!

Yes, square wing are aesthetically second rate to the the Pretty Eiptically shaped wing. But hey, asthetics is a quality that doesn't make it fly, maybe it is practicality and what has been proven by years of flying. By the way IN ALL OF THESE POSTS I AM MAKING ABOUT RANDY RUDOLF'S PLANES, I AM NOT TALKING ABOUT LIGHTLY LOADED ELECTRICS OF 12 OZ rtf AND A WING LOADING OF 4 TO 6 OZ ! No, I AM TALKING ABOUT PLANES UP IN THE 12 TO 14 OZ/SQ. FT. RANGE and HIGHER. . SOME OF THESE LITTLE ELECTRICS W/ WING LOADINS OF 5 OZ/ SQ. FT. WILL FLY WELL ENOUGH FOR THE AVERAGE GUY WITH ENOUGH POWER. THEY DON'T HAVE TO WORRY ABOUT AERODYNAMICS! FLAT WINGS WILL FLY!> ....AND I WILL STICK WITH THAT.
In the pst three years I must have built 35 of these 6mm Depron "THINGS" that fly well enough to have fun and bring them home too. Ha,Ha, Ha WE HAVE TO HAVE THE TOOL THAT WILL FIT THE JOB. You don't swat flies with a sledge hammer.
.................................................. ...................................

I am just now finishing a 60" w.s. all balsa, stickbuilt, 50 oz, 726 SQ INCH WING AREA, 0.40 glo powered that resembles a LAZY BEE (original w/ high wing) but the fuse has been shortened some. It has 4 channel w/ ailerons too. THERE IS A REASON FOR THIS MADNESS.
While flying the CRAZY PANDA on RealFiight Simulator I found with CG moved back some and having ailerons I could almost fly it in tight circles without loosing altitude ---its CWAZY !! Just start a turn w/ ailerons play the throttle to 50% or so, feed in enough up to maintain altitude and then tighten it up.....it will stay there in one place chasing its tail, ha ha !
So we build our "TOOLS" to fit a certain "TASK". Some want to go fast, some want to Fly Aerobatice (3-D) and some of us just want to fly for Phun.

[BMatthews]

For casual sport flying there's no doubt that a constant chord has some advantages. But along with those come some disadvantages as well.

The advantages are that the whole wing is operating at one reynolds number. And in our sizes where a little can make a big difference this should not be taken lightly. To real world performance it means that the whole wing will tend to stall at the same time so to avoid tip stalling there's only a tiny bit of washout needed. For casual flying a constant chord wing also will have good roll damping when upset.

The disadvantages that come with this are increased drag due to strong wing tip vortices. Smaller tip chords automatically produce smaller vortices for any given angle of attack. For aerobatic models constant chord isn't as good as tapered because of the same damping effect that is a plus on a casual design for relative newbies. But taper it too much and you have a recipe for harsh tip stalling.

So was Randy right? The answer is "it depends"......

[JetPlaneFlyer]

To real world performance it means that the whole wing will tend to stall at the same time so to avoid tip stalling there's only a tiny bit of washout needed.

Actually on a constant chord wing the root will stall well before the tip (because of downwash reducing the AoA at toward the tip). So you get a gentle and safe stall. With constant chord no washout should be needed for tip stall reasons and therein is its advantage.

[vintage1]

I haven't found that in practice. Most tip stalls seem to happen when you are slow and put on yaw..the inward side of the yawed wing stalls, whether its constant chord, tapered or elliptical.

It seems more related to aspect ration than wing planform. The worst models I have for this are very slight constant taper. My elliptical winged stiff seems fairly immune.

[JetPlaneFlyer]

I've never flown an eliptical wing RC model so i cant comment from first hand experience... However I know Spitfire models have a nasty reputation unless the wing has washout.

Some of the straight taper wing models I've flown have been real nasty for tip stalls. The worst tip stalls I've experienced came when flown fast in high G pull up's and turns, these resulted in violent flick rolls (often in the opposite direction to the turn), on a couple of occasions were unrecoverable :mad: .
I've never experienced this in a parallel chord wing.

[ZAGNUT]

his last name was Randolph, rudolph was a reindeer...

[JetPlaneFlyer]

rudolph was a reindeer...

I hate to be the one to break this to you..

The whole Rodolph / Santa thing... it's all a big hoax that adults use in an attempt to blackmail children into behaving themselves... sorry:(

Steve

[vintage1]

I've never flown an eliptical wing RC model so i cant comment from first hand experience... However I know Spitfire models have a nasty reputation unless the wing has washout.

Some of the straight taper wing models I've flown have been real nasty for tip stalls. The worst tip stalls I've experienced came when flown fast in high G pull up's and turns, these resulted in violent flick rolls (often in the opposite direction to the turn), on a couple of occasions were unrecoverable :mad: .
I've never experienced this in a parallel chord wing.


Teh trouble is that more often than not something wrong gets blamed. I did a Miles Magister, stll working on it..almost straight chord wings, and already it looks like its a bit of a tip staller (rear CG didn't help either). Its got a pretty thick wing too. MY elliptical wing model is far far nicer.

There is a hugely complex play between wing shape, dihedral, adverse yaw effects and lord knows what else when one wing stalls. We would all like to be able to pin it down to one thing, but what experience I have had suggest it cant be solely laid at any particular door.

If you want to see tip stalls in a parallel chord wing pick any sailplane of that type and do a slow turn in it.

YOUR experience relates top fast high wing loading models. Maybe there elliptical is Bad. In slow machines it aint.

All these fancy diagrams refer to wings in a straight airflow. However no one really cares what part of a wing stalls when its in a straight airflow: what counts is how it stalls when its yawed and one half is travelling faster than the other. And probably, if it has dihedral, at a completely different angle of attack. Not to mention possible blanking effects of a fuselage.

So I stand by my positin:

1/. Of all the things that affect model lane performance, the shape of the wing for a given aspect ratio and section is probably the least important.

2/. square wings are slightly worse than any other wing shape for almost anything. Except ease of build :D.

I personally have not seen any relationship between planform and tipstalls in the models I have built and flown. CG, dihedral and fin area have been far more important in affecting spiral stability at or near the stall.

[Brandano]

There's also another possible cause for tip stalls on a straight wing, especially at high speeds, high AR and with reflexed airfoils: aerodynamically induced wing twist. In the best case the stall will unload the wing, in the worst cases the wing will just flutter or fold back. A little sweep should help there, as well as moving the spars a little forward.

[nmasters]

Okay, now that I'm in a less smart a*s :eek: mood and have some time to write. I would agree with Mr Randolph except that just about any deviation from an elliptical planform results in increased induced drag and increased wetted area i.e. parasite drag. Also taper, elliptical is just fancy taper, decreases the inertia that retards both the initiation and stopping of roll. The attached chart shows the induced drag increment for several planforms at AR = 15. The three columns under E= are for varying degrees of washout. Notice that the hershey bar has 1.127 under 0 degrees, that means that an untwisted constant chord wing has 12.7% more induced drag than an untwisted ellipse of the same span and lift. Looking under 3 degrees we see that the induced drag penalty is only 2% at high speed and increases to 6% at low speed and of course the stall of this wing would be really docile. Unfortunately Compared to an ellipse of the same root chord and span that hershey bar has about 20% more wetted area so even though you can get the induced drag down with a few degrees of washout there's still a non trivial parasite drag penalty. I think the most important factor in choosing a planform for a model is make sure the Reynolds number at the tip at minimum flying speed is above the critical Re of the local airfoil. Although this thread is about planform I think Mark Drela's broader comments about wing design (http://www.rcgroups.com/forums/showthread.php?p=10371993&highlight=taper%2Fwashout%2Fairfoil#post10371993) are appropriate here.

--Norm

[eflightray]

Now I admit to knowing very little about aerodynamics, I just build and fly models, but I do find some of these threads down here of interest to read.

I hope this question isn't too OT to this thread, but I would be interested in comments about the wing tips in this link - Twin wing with tips linked (http://www.rcgroups.com/forums/showpost.php?p=10678906&postcount=16)

Looking at the tips I would imagine all sorts of turbulence being created, but for good?, or bad?, or at model size not too relevant?.

[nmasters]

Wing interference really complicates things. Interference is usually destructive but it can be constructive. Joined wings can be very efficient if designed right. I wouldn't second guess Macboffin. He's been at this stuff a long time, both professionally and as a hobbyist.

--Norm

[Texas Buzzard]

his last name was Randolph, rudolph was a reindeer...

Yes Sir. You are Correct. How did I do that? I typed Rudolf. WOW!
Sorry RANDY.

[Texas Buzzard]

Now I admit to knowing very little about aerodynamics, I just build and fly models, but I do find some of these threads down here of interest to read.

I hope this question isn't too OT to this thread, but I would be interested in comments about the wing tips in this link - Twin wing with tips linked (http://www.rcgroups.com/forums/showpost.php?p=10678906&postcount=16)

Looking at the tips I would imagine all sorts of turbulence being created, but for good?, or bad?, or at model size not too relevant?.
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Most all models can be made to fly if you are not too picky about performance.

We get away with "murder" with odd designs. The FAA would never ceritify maybe half of our models for flight. But thats the fun of it. As long as we don't go over the AMA weight limits we can fly it.

I thank you for the photos of that BIPLANE ("twin winged bird").

[Texas Buzzard]

N. Masters, may I ask a stupid question? Thankx.

Your next to last post had a chart showing various data for variously shaped wings with an aspect ratio of 15 to 1. Now we all know that is the wing of a man-carrying sailplane. A model sailplane with an A.R. of 15 to 1 is a rare bird indeed.

MY QUESTION IS: What do these numbers mean to us? Some planforms on the chart have a "poor" beside some of them. POOR FOR WHAT?
Do you use this info in your designs?

Sorry but I cannot see the relavalence. Thanks before you answer. ( My best floater , a sailplane called the "Gentle Lady" by Goldberg, has no taper nor eliptical tips. )

[bwalt822]

JetPlaneFlier , "Buzzard,
Randy had a very valid point for the type of flying he did i.e. general fun/sport flying where outright performance is second place to safe and predictable handling... No point having the highest performance model out there if you take it home in 100 pieces

To be honest, aerodynamic considerations aside, the main issue I'd have with parallel chord wings is that they don’t look as nice as a tapered wing (to my eye anyway)... A very subjective and non scientific reason I have to admit."
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I agree with you 101%. Yes sir, for everyday flying Randy's wing will suffice!

Yes, square wing are aesthetically second rate to the the Pretty Eiptically shaped wing. But hey, asthetics is a quality that doesn't make it fly, maybe it is practicality and what has been proven by years of flying. By the way IN ALL OF THESE POSTS I AM MAKING ABOUT RANDY RUDOLF'S PLANES, I AM NOT TALKING ABOUT LIGHTLY LOADED ELECTRICS OF 12 OZ rtf AND A WING LOADING OF 4 TO 6 OZ ! No, I AM TALKING ABOUT PLANES UP IN THE 12 TO 14 OZ/SQ. FT. RANGE and HIGHER. . SOME OF THESE LITTLE ELECTRICS W/ WING LOADINS OF 5 OZ/ SQ. FT. WILL FLY WELL ENOUGH FOR THE AVERAGE GUY WITH ENOUGH POWER. THEY DON'T HAVE TO WORRY ABOUT AERODYNAMICS! FLAT WINGS WILL FLY!> ....AND I WILL STICK WITH THAT.
In the pst three years I must have built 35 of these 6mm Depron "THINGS" that fly well enough to have fun and bring them home too. Ha,Ha, Ha WE HAVE TO HAVE THE TOOL THAT WILL FIT THE JOB. You don't swat flies with a sledge hammer.
.................................................. ...................................

I am just now finishing a 60" w.s. all balsa, stickbuilt, 50 oz, 726 SQ INCH WING AREA, 0.40 glo powered that resembles a LAZY BEE (original w/ high wing) but the fuse has been shortened some. It has 4 channel w/ ailerons too. THERE IS A REASON FOR THIS MADNESS.
While flying the CRAZY PANDA on RealFiight Simulator I found with CG moved back some and having ailerons I could almost fly it in tight circles without loosing altitude ---its CWAZY !! Just start a turn w/ ailerons play the throttle to 50% or so, feed in enough up to maintain altitude and then tighten it up.....it will stay there in one place chasing its tail, ha ha !
So we build our "TOOLS" to fit a certain "TASK". Some want to go fast, some want to Fly Aerobatice (3-D) and some of us just want to fly for Phun.


Can you give a list or chart of what intensity of speech that your color/font combinations mean. I cant pick out what is most important :eek: :confused:

I agree with whoever said that square wings help with making a stable gentle wing. There are numerous aerodynamic advantages to be had depending on what you want to do.

[vintage1]

MY QUESTION IS: What do these numbers mean to us?

The obvious cheap shot, is "obviously, not a lot :) "

However let me mitigate the sting by saying they didn't mean a lot to me either... ;)

[nmasters]

What do these numbers mean to us?
They mean the same at model scale as at full scale. You pay a price for deviating from an elliptical lift distribution and extra wetted area. The difference between big and small airplane design is that model designers have to be careful that the tip never drops bellow a critical Reynolds number. If a given amount of taper would cause any part of the wing to stall from low Re then obviously you shouldn't taper the wing that much. This is a compromise between three different phenomena:
induced drag due to planform effects
early stall due to low Re
and parasite drag due to wetted area

That link I gave in post # 21 addressed the low Re problem and the chart shows the relative efficiency of different planform shapes. You pointed out that that chart is specifically for an AR of 15:1 so I spent most of my Saturday afternoon tracking down a different graph. This one shows the induced drag increment for three untwisted wings of different aspect ratios compared to an ellipse of the same AR. The Y axis is the induced drag increment. The increment of the elliptical wing would be zero so the relative efficiency of each wing is proportional to its distance from the the X axis. Note that this graph is for wings without washout, the right amount of twist can move any data point closer to the X axis by bringing the lift distribution closer to elliptical. But twist only corrects the span load for one AoA and does nothing to reduce the wetted area.

Some planforms on the chart have a "poor" beside some of them. POOR FOR WHAT?
In this context “poor” means “poor span efficiency”. I too was disappointed that prof Strojnic didn't include real numbers in those places but it's still the most complete chart of this kind that I've seen. Since the book is about high efficiency aircraft he probably didn't feel a need to crunch the numbers for cases where the result was already known to be worse than the worst wing on the chart, which is the hearshey bar

Do you use this info in your designs?
I decided to give away my RC gear in 1996. The fun went out of building shortly after that :( Since I don't build I don't design anymore either and I didn't have as much data then so, no, I didn't use it. Most of my planes were constant chord tailless gliders.


( My best floater , a sailplane called the "Gentle Lady" by Goldberg, has no taper nor eliptical tips. )
I bet it has just enough twist to make the lift distribution elliptical at minimum sinking speed.

--Norm

[Texas Buzzard]

Can you give a list or chart of what intensity of speech that your color/font combinations mean. I cant pick out what is most important :eek: :confused:

I agree with whoever said that square wings help with making a stable gentle wing. There are numerous aerodynamic advantages to be had depending on what you want to do.

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Hey, Hey bwalt822,
Gee Whiz WALT, I don't have a Chart that tells the reader with what intensity of speech I am intending. I don't. I know that you are intellegent enough to "pick out what is most important". You did "pick up" on the fact that some parts are more important -cool!
Maybe I should aplogise to you for posting here as if I was teaching a group of High School students. I have become acostomed to trying to make my main points stand out for the reader.
If you had taught H.S. Phusics and Chemistry as I have for 38 YEARS ( there I go again....ha ha ). If you had taught H.S. Physics and Chem 2 for 38 years You too might have my habit of EMPHASIZINGING with what ever tool you had at your disposal. Here I have Bold Fonts, Color and Underline.
I guess I defeated my goal and that was to give an opinion and/or information. I think you were distracted....but you are one of the intellegent ons. WHy did I type that? It did bother you Walt that I tried to emphasise with THE AVAIALABLE COLOR AND BOLDNESS. IT IS AVAILABLE - IF IT'S NOT TO BE USED THEN IT WOULDN'T BE THERE.
LASTLY, IT COULD BE THAT MY AGE ( 79 YEARS)IS A FACTOR. YOU YOUNG "WHIPPER SNAPPERS (HA HA ) THINK I AM yELLING AT YOU IF i MAKE A WORD BOLD. I CAN HONESTLY GUANRATEE THAT I AM NOT YELLING.
IF ALL THIS IS NOT GOOD ENOUGH TO EASE YOUR MIND THEN YOU HAVE THE OPTION OF NOT READING MY POSTS. REMEMBER THAT I DID APOLOGISE TO YOU WALT AT THE BEGGINING.
Texas Buzzard , McAllen, Texas age = 79 years. And yes I flew this week end, 6 flights. Oh yes, WALT, I didn't use any color....doggone it!!

[Texas Buzzard]

nmasters, I will print a bit from your very thoughtful post.
From "nmasters": "The increment of the elliptical wing would be zero so the relative efficiency of each wing is proportional to its distance from the the X axis. Note that this graph is for wings without washout, the right amount of twist can move any data point closer to the X axis by bringing the lift distribution closer to elliptical."

This part of your poat gave me an entirely NEW reason or understanding of why I use washout on all gliders and trainer type A/C. As the blind man said,"Oh now I see." From 45 years of dabbling with 2-M and 120" Sailplanes off and on I know that the resistance to Tip stalls increases with 2 to 3 degrees of wash out at the tip. I have visualised that the tip was still flying when the inboard section had stalled. I still hold to that theory.

But your graph doesn't talk about tip stalls, does it?
But now I will venture a hypothesis. Correct me if I fall off the wagon.
Your graph and thinking it seems is telling us that a truely eliptical wing will fly almost like one of my non-tapered wings with 3 degress of washout over the last 30% of the half span.
Thanks for making me think, nmasters....you did a good job of explaining that.
nmasters, Vintage is an Engineer from Caimbridge and I have a Masters in Chemistry from Univ. of Texas so if we both didn't understand that graph, I suppose some text neeeded to accompny it.
You are letting the eliptical wing with no washout to be the Zero (0) point and are comparing the other wings to 0. As I remember an eliptical wing first stalls near it's inboard area and goes outward faster along the T.E. Isn't that correct;therefore it's tip stalls last?
Lets see if I understand what the graph was trying to tell us? You are saying that a truely eliptical planformed wing will fly, that is resist tip stalls, like a wing with no taper and has a squate tip( but has washout) will fly. A runon sentence but understandable. HOWSZATT?

[Texas Buzzard]

I will give the source after I give this entry concerning charateristics of an elipyical wing. Please notice that this writer says that an eliptical wing gives no stall warning. It has a sudden stall and iusually accompnied by a roll to one side,i.e., this is a classic spin entry.

Here is the partial text. "The elliptical wing is the ideal subsonic planform since it provides for a minimum of induced drag for a given aspect ratio, though as we shall see, its stall characteristics in some respects are inferior to the rectangular wing. It is also comparatively difficult to construct. The tapered airfoil is desirable from the standpoint of weight and stiffness, but again is not as efficient aerodynamically as the elliptical wing. In order to preserve the aerodynamic efficiency of the elliptical wing, rectangular and tapered wings are sometimes "tailored" through use of wing twist and variation in airfoil sections until they provide as nearly as possible the elliptical wing's lift distribution.

This is the address for that article. <http://www.dauntless-soft.com/PRODUCTS/Freebies/Library/books/FLT/Chapter17/WingPlanform.htm> copy and paste.

While it is true that the elliptical wing provides the best lift coefficients before reaching an incipient stall, it gives little advance warning of a complete stall, and lateral control may be difficult because of poor aileron effectiveness.
In comparison, the rectangular wing has a tendency to stall first at the wing root and provides adequate stall warning, adequate aileron effectiveness, and is usually quite stable. It is, therefore, favored in the design of low cost, low speed airplanes."
IMHO I think Randy Randolph was emulating what is writen in this post. He was concerned about tip stalls and over all stall characteristics.

[nmasters]

The tapered airfoil is desirable from the standpoint of weight and stiffness, but again is not as efficient aerodynamically as the elliptical wing. In order to preserve the aerodynamic efficiency of the elliptical wing, rectangular and tapered wings are sometimes "tailored" through use of wing twist and variation in airfoil sections until they provide as nearly as possible the elliptical wing's lift distribution.

This is the address for that article. http://www.dauntless-soft.com/PRODUCTS/Freebies/Library/books/FLT/Chapter17/WingPlanform.htm


IMHO I think Randy Randolph was emulating what is writen in this post. He was concerned about tip stalls and over all stall characteristics.

Hmmm... Why does the illustration on that page look familiar? Oh yeah, I drew a similar chart for a thread on RCG last year (http://www.rcgroups.com/forums/showthread.php?p=8074860) . Those drawings show only planform effects. Planform is not the only geometric property of a wing. A wing also has cross sections, twist, surface texture and possibly a whole slew of devices that may be glued onto the basic shape. Say we take the highly tapered wing from that chart and twist it a few degrees. Now it will stall inboard. When compared to a hearshey bar that is twisted to have the same basic lift distribution the tapered wing weighs less, has less area and the mass is concentrated nearer to the root. It also maintains a nearly eliptical lift distribution over a wider range of angle of attack. All of this means that the tapered and twisted wing can climb faster, glide farther and roll faster than the constant chord wing. The only advantages to the constant chord wing are that it's simpler to design for docile handling and quicker to build. “Better” depends on the application but the type of wing you and Randy Randolph preferred is definitely not the all round choice. Actually there isn't an all round best wing. There are any number of performance points the designer can aim for and produce specialized airplanes. There are also just as many ways that an incompetent pilot can crash a good airplane.

--Norm

[Texas Buzzard]

I learned a new way to compare the rectangular "square wing" to an elliptical wing. Now we know that when choosing a wing for our own designs: and being aware of the possible Reynolds Number effect of a proposed wing we have to make some COMPROMISES. Don't aircraft designers always make compromises?

In designing a new radio antenna the engineer does his calculations, makes his drawings and then someone builds it. MOST OF THE TIME when the new antenna is tested he will find that some fine tuning is demanded for maximum efficiency. He has to make some changes. This was learned way back in the 1920's. It's still true today.

I have a friend who is the Chief test pilot for a small aircraft company in San Antonio, Texas. They don't build small airplanes they build primarily twin engined cargo and Executive Types.

He asked me a year ago if I wanted to watch , with me on the ground - insurance issues... while he tries to TEACH a new version of a twin cargo plane to fly.

That was quite interesting to me. "TEACH AN AIRPLANE TO FLY"? After talking a few minutes I realized he was doing what we RC types do when testing a newly designed A/C. We Trim them, maybe add or reduce the fin or the control surfaces and we play with the C of G and balance laterally. Engine thrust may be altered too. Yeah, we "teach our planes to fly".

Manufactures of full-scale A/C do what we do, they "teach the airplane to fly."
This bring a thought to mind concerning that elliptically plan formed wing. BACK TO COMPROMISES AGAIN! We find from graphs and a bit of math that wing "A" ( elliptical ) and wing "B" ( square wing with washout) differ in Le by about 12%.
The question is this: Is it worth the extra trouble of building wing "A" just to achieve a 12% efficiency in lift when performing a straight and level climb? Ho often will we be flying straight and level....and also climbing? Randy Randolf was a bit like Roy Clough; they both were prolific builder's and designed for the average builder so they could be published. Their planes were good enough for most modelers who are Fun-Fly guys or Sunday Fliers.

Yes the purely elliptical wing has some advantages over the square wing but HOW MUCH? Is the average builder going to cut out 20 or 40 ribs of all different sizes? No, 99% of the time. The Spitfire wing was the prettiest wing ever back when I was 12 years old - it still in. I have only built ONE Spitfire because of the difficulty of the rib cutting. So now this old thread has served it's purpose......we all got to thinking about some things we think are important. Pic shows a man in a box - remind me of Me. Thanks guys.

[william vargas]

Hi I'm looking for some info to design my own airplane I want something that let me know what are the measures that I have to take in consideration for the wings and I need everything about proportions can you give me some ideas please?

[william vargas]

Hi I would like to design my airplane but first I need to know what I should know before I start drawing... besides the model that I want ofcourse.So basically what I need to know is how to determine the measure that the wings should have with respect to the fuselage and all the info that you can share with me, I will appreciate it.

[JetPlaneFlyer]

William,
There is no simple answer to your question, aerodynamics is a very large and quite difficult subject and to try to tell you all you need to know on the subject in one message is beyond my capability.

The most practical and safest way forward for you is to find a successful model that most closely resembles in both looks and flight performance the design you have in mind and copy the main features from it... Make whatever changes you want to the styling to make the model 'your own' but keep the overall design similar to the original.

I also came across this diagram on a previous post which gives some rules of thumb for models of conventional layout: http://www.palosrc.com/instructors/basicdes.pdf

Steve

[nfhill]

Hi I would like to design my airplane but first I need to know what I should know before I start drawing... besides the model that I want ofcourse.So basically what I need to know is how to determine the measure that the wings should have with respect to the fuselage and all the info that you can share with me, I will appreciate it.

William, welcome to RCGroups.

I recommend "Basics of R/C Model Aircraft Design" by Andy Lennon, ISBN#0-911295-40-2. $20 very well spent. Also, keep asking questions.

Nick