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Jef Raskin article on aerodynamics in Fly RC Magazine - 2/12/2005 3:40:27 PM   
Ben Lanterman



Posts: 1284
Joined: 10/27/2002
From: St. Charles, MO, USA
Status: offline 		I am having a lot of difficulty trying to "resist the urge to curse, flame, degrade, insult or embarrass someone in your post".

I wrote this letter to Fly RC this morning while I was still ranting and cursing. Has anyone else read the article by Jeff Rankin in April Fly RC magazine?? Here is what I wrote to them............

Good morning,

I enjoy your magazine but......... Isn’t anyone at Fly RC bothered by the total lack of science and accuracy put out by Jeff Raskin in the April issue? He is right only on one point - that the air molecules don't have to come together at the trailing edge of the airfoil. He spends 85 percent of the article talking about the concept that the popular explanation of lift in books have had this wrong for years (Note that this is not what is in any modern text book used by professionals in the field). Apparently just those read by Jeff.

Then he says, "The wing moves air down, and therefore the wing goes up for the same reason a rocket goes up when it sends gasses down". - To say that the downwash is the mechanism of lift is totally wrong - that is like saying the tail wags the dog!

Thousands of aero engineers have been hard at work for 100 years studying the pressures above and below the wing and getting PHD's based on the math and knowledge of how the differential pressures on the wing are the direct cause of lift on the wing. There are hundreds of studies about shaping the wing to optimize the wing shape to maximize the efficiency of the wing to make these pressures. Then along comes Jeff and throws the whole thing in the garbage can with his concept that we don't have to worry about that, it is just the reaction to the downwash, like a rocket exhaust, that causes the lift.

Look at rockets for a second -

Mass rocket x acceleration of rocket = Mass exhaust x acceleration of exhaust. But only because they are connected by F=ma. Its simple - Mass exhaust x acceleration of exhaust = Force of exhaust (which is reacted on the rocket nozzle as a force) That force on the nozzle is a Force on rocket = Mass rocket x acceleration of rocket.

He is saying that the wing moves air down, and therefore the wing goes up. But he ignores the basic lift mechanism of the wing. He looks at what happens AFTER the lift has been produced by the wing and says that is the lift mechanism.

Jeff's approach is like seeing a pile of elephant poop and saying that it is what causes the elephant to move. Not that it is the result of metabolic processes that allow the elephant to move, not the muscles and the "combustion" processes that convert sugars into energy in the cells of the body controlled by an elegant set of nerve cells.

Jeff is just, oh, so wrong! If you paid him for the article you just got swindled!!

The wing lift is produced as a result of the angle of attack of the wing causing flow variation in the air. Those variations result in a pressure field that is lower on top of the wing and higher on the lower surface of the wing. The differential in pressures is the direct cause of lift on the wing. The wing can be moved only by a Force, remember Force = mass x acceleration (remember that a force is needed to counter the gravity acceleration for level flight).

I have been an aeronautical engineer for 40 years and have been involved in numerous wind tunnel tests where pressure taps were put on the top of the wing to measure and analyze these pressure fields on the wing. The integral of those pressure fields is, not surprisingly to us, the total lift that is measured on the model by its internal strain gauge balances.

Next time you feel like publishing something approaching the science of aerodynamics how about running it by an aero engineer to check it for accuracy? It would only take a minute and stop the efforts of people like Jeff who are just wrong. Please include me on that list. I am one such person, there are many that are much better qualified than I am that would be more than happy to look over your articles before publishing.

Ben Lanterman
Aeronautical Engineer Purdue 1965
Aero Dept. at McDonnell Douglas working on F-4, F-15, F-18 and other projects.
Presently retired, Active RC modeler for 40+ years.

< Message edited by Ben Lanterman -- 2/12/2005 4:26:58 PM >


_____________________________

Ben Lanterman
       Post #: 1

RE: Jef Raskin article on aerodynamics in Fly RC Magazine - 2/12/2005 4:50:31 PM   
HighPlains


 

Posts: 2664
Joined: 3/2/2003
From: Over da rainbow, KS, USA
Status: offline 		Not a Mac fan? Jef is the guy that "invented" the Macintosh operating system (I may have left out a few steps). Of course Xerox had this little research office in Palo Alto Ca that had already invented most of everything we use now in computers, but since Xerox made copiers, their management didn't think that object computing fit their corporate model. Anyway, the kids at Apple (a bite of knowledge or was that a byte?) got to see the future, and everything was as it should be until another kid did the future a little bit cheaper and by being a lot more clever outperformed blue and everyone else.

See, just like you need to know a little about aerodynamics to fly (quoting from his article), you need to know a little about computers to read email.

Keep the torches lit, Ben. Science!

_____________________________

In politics if you want anything said, ask a man. If you want anything done, ask a woman - Margaret Thatcher

(in reply to Ben Lanterman)
       Post #: 2

RE: Jef Raskin article on aerodynamics in Fly RC Magazine - 2/12/2005 5:06:18 PM   
Tall Paul



Posts: 4655
Joined: 6/23/2002
From: Palmdale, CA, USA
Status: offline 		I enjoy reading Raskin's versions of aerodynamics.
His planes (the ANABAT) fly, so I guess he must have something right.. as if it takes much to get a sloper to work.
His explanations of "why planes fly" are the amusing parts when he writes.
Completely out of his field, which is computers.
It's a different approach.
I'd be more surprised if the magazine editors were up to critiqueing his stuff though.
They'd be more impressed by the reputation than the words, and presume the words matched the reputation.

_____________________________

Sparky Paul
http://www.angelfire.com/indie/aerostuff

(in reply to HighPlains)
       Post #: 3

RE: Jef Raskin article on aerodynamics in Fly RC Magazine - 2/12/2005 7:27:59 PM   
Ben Lanterman



Posts: 1284
Joined: 10/27/2002
From: St. Charles, MO, USA
Status: offline 		HighPlains - actually this is being written on the fastest G5 mac that money can buy. Six hard drives, tons of ram, more power (insert Tim the Tool Man's grunt here). I am a fan of his work regards to computing and have had a version of nearly every Apple computer since the Apple I. The first MacIntosh was a marvel and I had one at home and at work. Great stuff.

He then assumes that since he is a good computer guy that anything he comes up with on aerodynamics is right too, apparently without reading any accurate literature on the subject. He must read the pulp fiction type of presentation that was and still is wrong. He should know better, it is bad science. If he would do some work on the subject before spouting in print he would be more credible.

Agreed Paul - actually we know that anyone can make an airplane fly and not know a thing about aerodynamics! I see it happen everytime a kid throws a paper airplane and most of the first decade of airplane designs (the Wrights excluded - at least they tried to understand). Heck I made dozens of nice flying airplanes as a kid and didn't know anything except a rough idea that aerodynamics was like what Jeff is expounding about. I have since found that I was wrong.

I think there must be some ego trip that come in to play in Jeff's writings. Big computer science guy knows more than all the stupid aero types messing around with things they don't know. He comes along and saves all of us from the wrong concepts that we have been laboring under for all these years.

It would be like me telling him that his concepts about computers are wrong since we all know all you have to do is flip the switch on a box and the computer works. Obviously I know that nothing happens in the box. Oh yes, I need to spend a lot of time talking about the misunderstanding that early scientists had about electricity flowing from positive to negative.

I wish he would stop the nonsense. Want to bet he never does enough work on the subject to know enough to knowingly retract what he wrote. Ego tooooo big.


_____________________________

Ben Lanterman

(in reply to HighPlains)
       Post #: 4

RE: Jef Raskin article on aerodynamics in Fly RC Magazine - 2/13/2005 3:31:13 PM   
dick Hanson



Posts: 10035
Joined: 12/12/2001
From: slc, UT, USA
Status: offline 		Boy -I hope you got all of that out of your system.
You don't agree with Raskin - so be it .
I don't think he really cares.wether or not his ideas pass the criteria others deem important.
He gets the results he wants , operating in his own fashion.
I don't think he was trying to tread on anyone's toes - he just wrote his opinions.
To be a bit pointy fingered - why should modelers be concerned with data which primarily applies to vehicles travelling in far higher size/ speed weight envelopes?
This stuff is all for fun and relaxation.
Ask your heart doctor wether or not this approach is better .
Ben -I gave up worrying about other's opinions years back.
You may change them -but at what cost to you?

_____________________________

I am watching you
Libby

(in reply to Ben Lanterman)
       Post #: 5

RE: Jef Raskin article on aerodynamics in Fly RC Magazine - 2/13/2005 6:10:02 PM   
onewasp


 

Posts: 1360
Joined: 12/11/2002
From: USA, USA
Status: offline 		Ben,

Unfortunately xxxholes are xxxholes regardless of net worth or perceived excellence in other fields.

Unfortunately the world is filled with them. They seem to thrive on the controversy they create and become legends in their own minds.

Even IF they have reached 'excellence' in one field they really identify themselves by asserting themselves (legend in their own minds) in a field in which they have little or nothing to offer.

xxxhole------about the only word in the language without an adequate synonym.

He has thoroughly defined himself-------forevermore.

My thoughts.

< Message edited by onewasp -- 2/14/2005 4:30:08 PM >

_____________________________

The ground reached up and smote my airplane

(in reply to HighPlains)
       Post #: 6

RE: Jef Raskin article on aerodynamics in Fly RC Magazine - 2/13/2005 7:04:40 PM   
Ben Lanterman



Posts: 1284
Joined: 10/27/2002
From: St. Charles, MO, USA
Status: offline 		Agreed with everyone even Dick, surprisingly ......... except - there is a fundamental desire in most engineers and modellers to want to understand what they are doing. In your writing you indicate that. Understanding aerodynamics even in a simplified version still should be right. I think the average modeller is entitled the best efforts to present why his airplane flies. For those of us who overpower our monsters it is not that important but there is a whole bunch of guys who fly gliders in competition that take this stuff to heart. A lot of guys wonder why a flat plat wing works, why camber, how flaps work etc.. It doesn't have to be presented in terms of vortex theory and the Euler equations of motion but....... it shouldn't be dumbed down to the extent that Jeff does. The full scale aerodynamics isn't that much different from model sized aerodynamics, there is just a Reynold's number effect, certainly the basics are still valid.

It is a shame Jeff does it. Last month he wrote an excellent article on perspective and how it influences what you see as you try to fly the model.

With what he has said about aerodynamics - it isn't just an opinion that might be as good as the next guy's - it is just totally wrong. Then to use the forum of a monthly column to continue spouting it is nonsense. It is insulting to all of the many thousands of us that spent 4 years in college (many more) and worked in the industry.

Actually it is bad for the heart to keep it inside, venting is better.

I would encourage everyone that disagrees with him to write the editor, Tom Atwood, at

toma@flyrc.com


_____________________________

Ben Lanterman

(in reply to dick Hanson)
       Post #: 7

RE: Jef Raskin article on aerodynamics in Fly RC Magazine - 2/14/2005 1:06:10 AM   
Johng



Posts: 1817
Joined: 1/24/2002
From: Deland, FL, USA
Status: offline 		I haven't seen the Raskin article, but I don't think Ben is making stuff up.

So, we are talking about the science of flight. There is no room for opinion, though Dick mentions the word twice. It does not apply here. If the guy was saying what Ben relates, he shouldn't be published, and Ben should be complaining. The force of lift is as much fact as the force of gravity. It's not my opinion that I weigh this much, , it's a physical fact. Same with the way lift is generated. It would be opinion as to whether I look good weighing this much, and opinion can come into play with the assessment of flying qualities, but not the physics of it. There's understanding - or there's ignorance. But opinion counts for nothing with regards to the facts.

I see another firestorm about the downwash chicken, the bernoulli egg, and if poultry flies , and as soon as that's started I'm gone.

_____________________________

John

(in reply to Ben Lanterman)
       Post #: 8

RE: Jef Raskin article on aerodynamics in Fly RC Magazine - 2/14/2005 3:49:01 AM   
Ben Lanterman



Posts: 1284
Joined: 10/27/2002
From: St. Charles, MO, USA
Status: offline 		Chuckle, that was funny John. Get the article, it is worth reading.

I would put the article text on here but would probably get in trouble.

My friend here in St. Charles, MO is Dave Evans, he was the head of the whole aerodynamics department of the St. Louis part of Boeing. We did the fighters and a few other things at this location, used to be McDonnell Douglas. Now, mind you, there is no higher level to get and still be in the aero dept, he was the head honcho (whatever that means) big weenie, etc... He is retired now and we fly RC models together. A nice guy.

He said he started to read the article and saw immediately where it was going and thought it not worth finishing, that it was wrong.

I was just a misguided mid level aero engineer, but guys, Dave was the head of the whole thing and a heck of a good engineer, non better in St. Louis in aerodynamics. He didn't like the article. What does that tell you??

Not opinion, just sound engineering evaluation. Opinion is OK in religion, girls, steaks, things you eat that go crunch, beers, whiskeys, wether or not 3D is flying and things that scare you. Opinion isn't a part of being precisely accurate in a discussion of physics of which aero is just a subset.

Granted the modelling press is there to entertain and educate and mercy knows Fly RC is a very good magazine. But we need to hold the modeling press to a high standard of accuracy since a beginner interested in models and why they fly tend to believe what a learned person like Jeff says. Why teach the beginner wrong or incomplete stuff. It is only a matter of a few words to do it right. A well educated modeler just might enjoy the hobby a little more knowing how and why things work.

Totally different subject, Dick, did those little square hardwood sticks really hold the motor? I had to look twice to see them. I understand that everything clamped together tightly makes a rigid structure but I sure would have the urge to skin the sides of the box with quarter inch ply. That motor must be a beautifully smooth running machine. If I were you I would have needed to explore the flight characteristics of the airplane a year or two in order to write the article :-)


_____________________________

Ben Lanterman

(in reply to Johng)
       Post #: 9

RE: Jef Raskin article on aerodynamics in Fly RC Magazine - 2/14/2005 4:29:44 AM   
dick Hanson



Posts: 10035
Joined: 12/12/2001
From: slc, UT, USA
Status: offline 		I have never had a problem using this technique.
To be blunt - I consider most fuselage setups (arfs ) to be grossly overweight - not too strong- just too heavy.
And - why would you use slabs of plywood up front ?
ultimately you have to pull on the longerons -so why not design a pylon or mounts -which will not twist and fasten directly to the longerons .
My Bucker was built in 1989 -and has flown with Tartan twin- G62 (not a good plan) ZDZ 80 singles -twins and a ZDZ60 - total aircraft flying weight as ranged from 16 lbs 9 ozs to 18 lbs -- 1790 squares .
there is one piece of quarter inch ply in it -the engine mount plate -
Also it flew at the TOC before I got it back from Steve. ( 2nd place 1990)
structurally still tight as a drum .
I do have a few years time in grade at designing structures - -commercial (high tonnage presses) machinery as well as models airyplanes -
I broke some stuff figuring out how far I could go but that is what I wanted to see.

_____________________________

I am watching you
Libby

(in reply to Ben Lanterman)
       Post #: 10

RE: Jef Raskin article on aerodynamics in Fly RC Magazine - 2/14/2005 5:12:38 AM   
Ben Lanterman



Posts: 1284
Joined: 10/27/2002
From: St. Charles, MO, USA
Status: offline 		I don't have a "feel" for the big airplanes sturcturally. What I meant was to enclose the squares with small pieces of ply which would make a ply box with the square wook in each corner. It would resist torsonial loads better. Could put one lightening hole in the center of each one without much loss. I guess I tend to think that the shaking and power involved is really going to tear apart the front of the airplane but again I simply don't have as good a feel for what is required as you do.

I would probably hang the engine on 1/4 inch aluminum plate welded into full length aluminum longerons, and then wonder why it didn't fly as well as yours.

How did you tie the engine mount plate into the longeron structure? Does the front of the model twist any when the throttle is changed quickly? I have been to Joe Nall but for safety never got up close enough to the running motors to really see what is happening and I can't tell much when they are sitting still with the cowl on and not running.

The biggest motor I ever used was a Quadra 38cc gas on a World Engines Robin Hood. 100 inch wingspan. The sides of the airplane were 1/4 inch ply from the nose to aft of the wing TE but I don't remember what the firewall was. One or two layers of 1/4 inch at least - Of course I glassed all of the inside joints. I could have driven stakes with the fuselage. No wonder it didn't have much vertical performance :-) Takeoff was a really looong process.

Dick, you do know that if you need to get rid of any of those old airplanes that are just taking up space and/or if you want to let me see the structure first hand and investigate it for, say, 10 years or so, you can send them to -

Ben Lanterman
3432 Covington Parkway
St. Charles, MO 63301

Not going to work is it..... well I'll keep trying... catch you in a weak moment......


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Ben Lanterman

(in reply to dick Hanson)
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RE: Jef Raskin article on aerodynamics in Fly RC Magazine - 2/14/2005 5:26:10 AM   
Tall Paul



Posts: 4655
Joined: 6/23/2002
From: Palmdale, CA, USA
Status: offline 		The firewall on my Byron's 1/4 scale CAP 21 was 1/4" ply, epoxied and glassed to the -styrofoam- fuselage.. the fuselage was made exactly the same way a picnic cooler would be. 1/2'" (more or less) foam cylinder.
More than sufficiently strong for the task, with a US Engines 35 cc motor.
I have a SIG Big Bingo kit, which is a liteply forest! Just about everything is 1/8" liteply.. seriously overbuilt in my estimation.
If I build it, there's gonna be a LOT of balsa where the ply is... Like the trailing edge sheeting..Ply???? The center plates for the horizontal and vertical are liteply plates, full outline.. ????
Heavy isn't better.

_____________________________

Sparky Paul
http://www.angelfire.com/indie/aerostuff

(in reply to Ben Lanterman)
       Post #: 12

RE: Jef Raskin article on aerodynamics in Fly RC Magazine - 2/14/2005 1:57:53 PM   
LouW



Posts: 804
Joined: 1/1/2003
From: Moreland, GA, USA
Status: offline 		I haven’t seen such religious fervor and denial outside of a “Holy Roller” revival. To get the credential thing out of the way, I am a graduate aeronautical engineer (Georgia Tech ’52) with many decades of experience in aircraft development and flight test. I am also a professional pilot and flight instructor. I have spent countless hours reducing and plotting data from manometer boards, oscillographs, tapes, etc. and interpreting the results. I have no question at all regarding the validity of the wing’s pressure field being the source of lift, and I have great respect for the aerodynamic principles that I have used throughout the years.

However, as a lift-producing wing causes an asymmetrical pressure field with it’s passage, the certain, and consistent result is the deflection of a mass of air downward. The mass acceleration is always proportional to the lift being produced. While it isn’t much use in design, and is largely ignored, it is a fact all the same.

Reality is that the pressure field concept and the momentum concept are equally valid (though obviously not equally useful) ways of looking at the same phenomenon.

(in reply to Ben Lanterman)
       Post #: 13

RE: Jef Raskin article on aerodynamics in Fly RC Magazine - 2/14/2005 2:31:28 PM   
dick Hanson



Posts: 10035
Joined: 12/12/2001
From: slc, UT, USA
Status: offline 		Oh -the 100 on the standoffs -
the standoffs were straight grained rock hard maple -end grain ,drilled 1/4" and pulled tight using 1/4 20 (overkill)thrubolts.
This wood is extremely resistant to crushing loads .
You are right on the triangle supports -I do use these on my own stuff (this plane was for a customer) but use 5mm thru bolts to tie structure together.
I will look for pictures of motor support to longeron intersections.
found a decent one - the boxes are light ply - with triangle stock in each corner -which is attached to each of four longerons on latest models .
The open framed fuselage had spruce diagonals added after picture was shot -
the model 11 lbs at 1280 squares 40 cc engine - incredible power to weight setup.
My newest stuff is lighter - really .
The performance of my electrics has convinced me that earlier concepts were simply too heavy and underpowered .
For me .