HighPlains

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During the war, both sides had the opportunity to test captured aircraft of the opposing side. The Germans didn't see any advantage to the Mustang's wing because their wind tunnels couldn't produce an airstream that was clean enough to see the laminar effect.

rmh

Thats why they produced a lot of greatly advanced designs?
We nit picked whilst they advanced technologically.
Fraqnkly "airfoils for models" while interesting - -is highly over rated in actual effectiveness.
There are preciousfew model applications where a particular airfoil can show an advantage
for the HUGE majority - athe structure and weight are of far greater importance -
I attended a lot of the TOC events- worked at the last one - did scale event at Nats once (2nd) and generally tried to come up with some type of a profile for successful models -in general
In order of importance
1 weight - scaling down any design requires a large rescaling of weight in order to provide good flyingcharacteristics
2 structure - innovative structure provides -for weight reduction




3 airfoils even in competitive aerobatic events the airfoils used are all over the place
in speed events -as thin as possible

HighPlains

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German engineering has been very good for a long time. But when the job is to make sauage, the type of meat is less important. Just the quantity.

da Rock

The design envelope of model airplanes pretty much blows off the necessity for special airfoils. There almost isn't an envelope.

We've got almost no special performance requirements like the P51's long range bomber escort needs.

We don't have to lift cargo and go somewhere with it. We don't have to make a profit. We don't even have to keep the passengers alive (and prove almost every day that our models wouldn't) much less provide for passengers.

We actually do have some special events like pylon and soaring that make good use of special airfoils, but the vast majority of our birds do very well with simple profiles that adequately supply what little is needed. And little is needed.

rmh

X actly!
The slope soaring event I went to yesterday demonstrated this very well
ALL the models use the same airfoil (well for all practical purposes the same .
The airfoil was really based on -
ready?
the thickness one can get away with with out the wing breaking
typically 7%. These were all high density wings skinned with carbon fiber
You could use em for Ginsu knives.
the task for a slope soarer is to use gravity and uprising wind to provide speed .
almost the opposite of a powered , fixed wing machine which needs to fight gravity and wind!! I am not saying selecting a "airfoil is not necessary, just that you MUST get your basic task figgured uot before selecting a shape.
There simply are no "good or bad airfoils just task specific types and even without a Doctorate , anyone can apply logic and get close enough for our purposes.
When I was a kid I was mystifed by the Davis wing (B24) and the Laminar flow (P51.)
what the ____ was so special about these shapes - I looked and looked and came away wondering .

Late on I saw that these were task specific shapes which, if operating out of their SPECIFIC design
criteria, were in some cases , no good at all.
I don't recall seeing any other craft using thses shapes at a later date - but then I really never looked very hard
Did anyone else copy these profiles?

My favorite design Turkey is the B36 - who was responsible for that?

Ben Lanterman

Rotaryphile - I wouldn't wonder that a scaled down Mustang airfoil wouldn't work well in an aerobatic airplane. Remember the Mustang was designed primarily for long range, once it got there if it could hold it's own in combat that was good too. I have no doubt they tried to minimize drag over a fairly small specific set of cruise parameters which means it is less than spectacular for other uses.

Dick you are missing what I am saying - I think. You said the good Dr must work with the same problems you or I will see in a model. You asked why should he be able to predict a better airfoil for an unknown subject ?

It doesn't defy logic. Airfoils can be judged without respect to a subject. One will have greater drag at a given angle of attack, another less separation, etc. You can judge one against another quite easily.

The good Doctor can predict a better airfoil because he has spent a lifetime of study in theoretical and practical airfoil development. There is a heck of a lot of math and science in the field that just working in the model industry won't give you. I have a meager four years at Purdue and 30 years in industry and realize just how little I know about it. Pick up any theoretical aerodynamics text and you'll find out rather quickly there is a lot more to it. It turns out the good Doctor was interested in model airplanes so he spent time in looking at model airplane sized airfoils in a good wind tunnel and took measurements.

What he found was that there were differences that were measurable, not just guessing but real measurable differences. Then with a knowledge of what the airfoils were to be used for - scale, free flight, slope soaring and so on - he could give a person the BEST airfoil that was practical. Not just a "this works OK" kind of airfoil. Aerodynamics is a very exacting science in spite of what a casual glance around the flying field would indicate.

Let's look at a real world case. In the real world, like the F-15 design procect, we designed a perfect shape around the engines, inlets and cockpit. The airfoil wasn't picked out of a hat, rather it was carefully selected. Based on initial computer studies it varies continually from root to tip to be the best setup at all angles of attack and speeds. It was a major task. Pressure taps were used to determine that distribution and oil droplet studies were made to determine boundary layer movements. Shadow graph photos and video were made to check shock patterns. Then the force and moment data was analyzed at all conditions of angle of attack and sideslip.

Then the airplane models were studies and modified to make it better. Note that we were using MODEL sized airplanes to check these things out. The sub/super sonic model was 4.7%. Another was 7.5%. I believe the low speed model was 13% or so (can't remember right now). These were model sized airplanes. We easily found that little differences in configurations and airfoils with airplanes as small as 4.7% of the full scale airplane made big differences in data results. Even extremely small differences in the airfoil could be seen in the data. The final airplane indicates that the small sized model approach works well.

But after all the airplane exterior design was done, then we let the structural and weight engineers try to make the airplane light and strong. Not the other way around.

By the way the 4.7% model is about the size of my GWS foamy ducted fan F-15. That is also the size of the airfoils that the good Doctor was testing. I would expect his data to reflect very small changes just as ours did. His work is entirely proper and a great source of information. I believe a lot of the major sailplane manufacturers use his airfoils. Anyway he found differences in his airfoils and was able to suggest one that would work well for a given condition - the flying scale model.

The fact that you can make wings as sharp as knives and that a 2412 or whatever airfoil works fine doesn't mean anything special. It just means that they will work if we put enough power on the front or that the wind is blowing strong enough. Sometimes a good configuration will come out of cut and try but it is a heck of a lot easier if you know what would work the best to start with. If you are going to build an airplane why settle for less than the best? I just don't understand that approach.

There are good and bad airfoils in a contest where a matter of fractions of a second determine first or second place.

We need to try to do more than just try to make things work. Isn't an aerodynamics forum a chance to do something that is better than just work?

Ben

sir crashallot

bassicaly your saying theres thousands of aerofoils of all different shapes and sizes all designed for different purposes, its just a case of finding one that when shrunk to model size and weight and speed and what the flight characteristicks are required will not cause or create any major flying issues, sorry if that sounds abit confusing but i couldnt put it any better[&:]

Ben Lanterman

Yes, and if the good Doctor says it is the best to use for a given purpose I tend to carve it in granite. I am a long time fan of his. Remember though, most airfoils are tested and selected based on model size and then enlarged to full size. Some times some strange things may come up that need little "fixes" but not toooooo often. If the airfoil is tested and used in model size it is pretty good stuff.

sir crashallot

hence why allot of airplane manufactures pay designers to have lots of models made of diferent wing sections to allow the computers in the wind tuinnels moniter the wing sections and show and point out the good behavers and the bad behavers, and the results aree based on the computers calculations i get it now

rmh

Ben - Most aircraft start out with a known powerplant and materials from which to construct the airframe
pretty basic stuff
However - IF one has to make a compromise (there's that word again) strength will trumph all else
The Sukhoi 29 was designed with the best compromise possible till the wings started coming off-

can you predict a better airfoil for a given task?
sure -
just as you can predict that a dog will lick an ice cream cone-given the chance.
Can the calculated "best shape" beat a really good SWAG by someone with a lot of experience?

I have my own opinion on THAT answer
based on experience.
Without which - niether approach works.
It's really tough to predict results when one looks only from ones' own vantage point
I recall reading about the pilots who test flew the German jet fighters after WW11 and wondering how they could have been so advanced in thinking and execution -yet they lost the war .
(crystal balls?)

sir crashallot

what about the su31 the wing snapped in half on me[:@] stupid black hoarse kit and from day one of taking it out of the box i kept saying to myslef that wing dosnt seem thick enough nor able to cope with flight, that thing was horid when trying to land it with throtle back at a fast idle it wanted to fall out the air continuasly.

da Rock

Not really. The results are real world results that were measured when real air was pushed over real test shapes. They then may apply formulas to adjust the resuts to a standard. And nowadays they use computers to crunch those numbers.

Also, did you know that a lot of windtunnel work was done at model sizes? They would of course have given their resuts exactly as they will outside the tunnel give or take differences in weather etc.

sir crashallot

yeah i watched a video on youtube of them testing a 747 i think it was had 16 ft wingspan too completely carved then molds made and glassed model made from them. then if i remember correctly they fitted tiny little sensors to the wing to measure the pressures of air, temperature and many more not to mention some flow senses to detect what angles the air was being thrown in and so forth, a real interesting video, il go see if i can find it as it may come in handy for anyone thinking aerodynamics and windflow is nothing but a myth

HighPlains

My Feedback: (1)

In May of 1940 Roosevelt called said "I should like to see this Nation geared up to the ability to turn out at least 50,000 planes a year.

We did it, they didn't.

In 1942 we built nearly 48,000
In 1943 we built nearly 86,000
In 1944 we built over 96,000
In 1945 we built 46,000

In total the USA built over 303,000 airplanes to the Germans less than 120,000 from 1939 to 1945.

Sausage in volume.

Moreover, our designs were later, larger with more power, thus the designs could grow in firepower, and pilot protection. A Mustang is much bigger and more powerful than a Me-109. And the Jug larger still.

rmh

Yes we could out produce them -that was our advantage
technoligically we were not in the same class - aircraft -guns tanks etc..

BUT the choice to outproduce was the right one for us and to out produce we took what was available and churned it out. I was just a kid but I payed attention
After the war the Russians and the USA stole as much of the German technology as they could (people and all) and used it practically as it was - for many years.
The A bomb technology we got from
German Jews .
Politics plays very strange games with technology

sir crashallot

well il contribute for us british, we sacrificed our pots and pans to make spits from them so at least i can get a funny vission of an me109 being chased by a pan wit a roundal stuck to it

HighPlains

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Leó Szilárd was from Budapest Hungary. He was the first to conceive of the chain reaction. He wrote the letter to Roosevelt that Einstein signed and forwarded.

HighPlains

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Spitfires got the glory, Hurricanes did the work.

sir crashallot

yeah iv heard that, but on a documentry i saw in different ways the spitfire and the huricane where in fact equal aponants
While the Spitfire was faster and more manoueverable the Hurricane could take much more damage.
The Spitfire out-classed the Hurricane, and that's why it stayed as the front-line fighter and the Hurricane was reduced to secondary roles
rearming for the Spitfire was 26 minutes. That of the Hurricane, only 9 minutes from down to up again.
The Spitfire was an all metal fighter, slightly faster, had a faster rate of climb and had a higher ceiling, while the Hurricane had a fabric covered fuselage, was quicker to repair and withstood more punishment. With the for's and against's of both fighters they came out about even. The majority of German planes shot down during the four month period were destroyed by Hurricanes. For much of the Battle of Britain, the Spitfires went after the German BF 109s at the higher altitudes, while the Hurricanes attacked the bomber formations flying at lower altitudes. This cost the enemy a total of 551 pilots killed or taken prisoner. During the war a total of 14,231 Hurricanes and 20,334 Spitfires were produced. The famous Rolls-Royce 'Merlin' engine evolved through 88 separate marks and was fitted in around 70,000 Allied aircraft during the six years of war.

In the hectic battles in the sky over southern England many pilots returned to base utterly exhausted and routinely fell asleep as they taxied their plane to a stop. Ground crews often had to help the sleeping pilot from the cockpit after he returned from combat.
It was the impliamentation of the two planes that made them so effective. Instead of trying to phase of Hurricaines or put them in reserve duty or something, they specialized and used the spittfires to busy the fighters while the slower hurricaines powered through the lumbering bombers.
If the Spitfire was never made, there would be no planes to distract the enemy so that the Hurricanes could shoot them down. But if there were no Hurricanes made, then there would be no plane to actually shoot down the enemy. The two planes kind of tie together and come as one.

The Spitfire was far faster and the design of the Aircraft allowed it to be upgraded over 20 times and was still in service with the RAF until the early 1950's. It had it engines mountings stretched to take far greater power plants. It was one of those planes that say if it looks right it feels right and you never hear a bad word spoken about it from any of the pilots. The pilots always reckoned that you strapped the plane on to you and it became one with you.



a few quick searchs of info about both planes revealed if either one wasnt designed we would have lost, both planes contributed a hellof allot to the war so in theory they isnt a sole winner, to me and probably many others who care to read about both planes there infactmore like brother and sister taking the bull by the horns and splitting it and sharing the battle between them.

so to me there both equal

da Rock

There's a statistic about the Hurry.

It shot down more A/C in the ETO than any other single fighter did, Allied or Axis. That would include P-51s etc.

da Rock

BTW, that Merlin that went into so many a/c......... The US built 'em too, so some of the Merlin powered a/c like the Mustang were sporting Packard-Merlins.

We not only stuck those into Mustangs but into Warhawks.

Did you know that the fastest Mustang of the era was powered by an Allison. They finally put a decent supercharger onto the sucker.

sir crashallot

no i never new that but i do now, when it comes to warbirds like the spit mustang hurricane and so forth there all beutifull looking planes they all have somthing distinct about them, itmay bee that before them it was all biplanes and these where revolutionary at there time and these where the first monoplanes and they had a need for them not to win trophies but to keep our heritages intact and the same, these planes created during the ww2 period are infact heros to us, the technology for airframes and engines devolped so fast in such short time that no wonder they had so many diferent engines fitted all with different specs to try and squeeze that last bit of power and speed out of the airframes.
i do often wonder with todays technology, what could be done with these vintage airframes could there designs ever be made even better than the standard that they where back then. and what levels of achievement could be gotton from them

Ben Lanterman

On the F-15 we didn't compromise the aerodynamics for strength. We said this is what the aerodynamic shape would be (must be) and the strength and materials engineers made it happen (and they did a great job). I don't understand why a compromise is necessary. Aerodynamics doesn't really require a compromise in strength of the airframe until you get to the high speed aircraft where the knife thin airfoils are dominate. but they are the exception - not the rule.

Can the calculated best shape developed by a competent engineer beat a really good SWAG by someone with a lot of experience - sure. What you are trying to get me to believe is - that a person with no aerodynamic engineering background and without the computer capability of the good Doctor can make a better airfoil selection for a given purpose by just using a SWAG approach. That is nonsense. That is like taking out your own appendix. Wouldn't you prefer to have a Doctor that knew where and how to cut? It isn't tough to predict airfoil results if you are using the programs that the good Doctor uses. It helps to know what you are doing.

Remember the old propaganda that the model magazines used to write about all the time - somebody would write that they just used a french curve and drew the airfoil and - look - they won the NATS and isn't it great. That did model science a great disservice every time it was written.

Concerning the Germans - I saw on several specials that they had decided to keep the two main airplane fighters they had going into the war (Bf and Me) throughout the entire war (with updates of course). Hitler just didn't think he needed anything else. Then he came to the English Channel and stalled. The number game caught up with him. Those "great" jets came too late and too little to do anything. Advanced thinking and engineering didn't pan out when it came to execution and putting the jets into service. A few jets against the bombs coming from the "aluminum sky" that was over head most of the time were pretty useless. They lost the war because of the good reasons noted in the other posts - the jets or lack of them had nothing to do with it.

And indeed the Mustang airfoil was developed by engineers using the available math and wind tunnel tools available.

sir crashallot - I totally agree, it would be fun. Keep the airframe shape for nostalgia , use modern motors (piston only of course, need the sounds), modern materials, update aero stuff where it could be improved and see what comes out.

Ben

sir crashallot

the stang willbe 70 - 72 inch wing and i have a nice strimmer engine sat waiting for the dremmel and dimand cutting disks to be brought towards it to shed some weight, its a 25cc and the only strimmer i knew that could start with a quarter of a pull. hopefully it can be made into a nice growler for the stang, i really do wish it would have the balls b to turn a big 4 blade prop by the way (BALL BEARINGS iwas refering to). still no worrys its a fair way off being built need to get all the design work sorted and adapt what info i have and try to encorporate all the info im learning about it aswell as almost 1300 reference photos

she will be dressed in the tuskeege colours as the all red tail looks beutifull on the stangs[8D] thanks for everyones input and dont forget the thread is not closed if you have an idea for its aerodynamics let me know,

how badly do drop tanks affect flight performance as it would be nice to be able to drop them if i fly her at our club shows as the kids that attend love anything like that, a few years back someone had a massive twin with a crago door at the back what opend, well he filled the cargo bay up full with sweets and toffees, got all the planes out the sky for 15 minutes while he did a run past and dropped all the sweets off onto the field we then told all the kids to go get the sweets you should have seen the faces of the kids though when we said that they were glowing,

topspeed

The size makes a big difference. I referred to 1/12 scale sized planes flying with original AC power to weight ratio. If you make a really lite plane ( low wing loading ) and try to fly "scalespeed" ( here I refer to the 1/4 sized plane going 1/4 speed ) then I assume well proven nearly symmetrical foils perform better.