Paul Lipps (designed) "elippse" propellers

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gschuld

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I have been researching propeller designs and I am intrigued by the designs of Paul Lipps. He seems to be breaking all the established standards of propeller design, and if Reno racing can be used as a benchmark, the designs have been enjoying great success. Below is the multi Reno winning biplane Phantom with a Lipps designed, Craig Catto built prop. The Phantom has gone from a 3 blade Lipps/Catto to the current 4 blade Lipps/Catto. Not what one would expect for a race prop. The below article, written by Paul Lipps, shares the design theory behind his creations. A good read for those interested in prop design.




http://www.biplaneracing.com/files/Issue77_8-13.pdf

One of the aspects(of the many) of his designs that particularly interest me is the drastically different way his props appear to function near the spinner. The current trend over the last bunch of years for high speed planes(Lancairs/Mooneys/ Sam James cowls) is to design cowls with round inlets spead fairly far apart from the spinner and root of the prop. This is intended to avoid the root of the propeller's clubbing effect common to most propellers and place the inlets where the air is being pulled in a much cleaner fashion out further on the prop. Makes sense to me. Now if you look at one of Paul Lipps designs, the full laminar flow cross section is in full action from the spinner out. No apparent clubbing effect, plus the chord is very deep and the pitch is steep just out from the spinner. I presume that this shape would only increase the amount of air being shoved into an inlet, especially at low rpm situations on the ground when many planes need it most. Paul seems to greatly favor small inlets right up against the spinner with his designed props, the very thing that all the go fast guys have been getting away from with more common designed props.
As I am in the planning stages on a new KR-2s build, and designing a very efficient prop/engine/cowling/cooling system combination is high on my priority list. As I intend to design and build the cowling from scratch, the spinner size/cowling inlet shape is something that I would like to be fairly confident with going in as it effects the lines/shape/overall look of the front end of the fuselage.
Having inlets near the spinner certainly makes the inlet diffuser shape easier to design for the fiberglass hard topped cooling plenum. The problem is if I went that route it is unlikely that I would have a Lipps designed prop initially as Paul designs props based on carefully gathered data gathered from the actual plane. I would be thrilled if a Paul Lipps designed prop ended up in the hands of another Corvair powered KR-2s (Mark Langford:)) so some established data could be collected. It would probably be good if I could get an idea of what Craig Catto would charge for say a Lipps designed 54" 2 or 3 blade. Catto props are not cheap, and they shouldn't be considering how intricately built they are.

Vari-prop is supposed top be making "Elippse" blades for both constant speed and in flight adjustable propellers for the RV line. I am interested to see how well they do. I haven't heard whether any "stock" fixed pitch Elippse designed props will end up on the market.

I'm curious whether this prop design will start changing the accepted norms?

George
 

pwood66889

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I have a book on prop design, George, that takes that very track. Called "Propellers: The First, and Final Explanation," it is self-published by Mr. Jack Norris of Notrhridge, California.
Mr. Norris contends that a prop is more than a rotating wing. It is an "airscrew," and gets the best results by imparting a bit of speed increase to a huge amount of air. He opins that thrust goes to zero at the tips, so the large paddle blades in vogue now just convert your avgas into noise!
When was that Contact! article published? And I wonder if Mr. Norris was who Mr. Lipps was talking about in his last paragraph.
Percy in NM, USA
 

Mike Armstrong

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Percy, what did you think about Jack's book? Among the many forums and lectures I attended at Osh this year was Jack Norris's propeller lecture. I remember he abruptly stopped talking during his lecture once to point out the noise of an aircraft as it flew overhead. He said something like...'hear that? thats the sound of inefficiency'. His lecture was very interesting and meant to be a 'simplified' explanation of props but it was still largely over my head. I was hoping his book was easier to understand, is it?


Mike
 

gschuld

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Percy,

The article was in issue#77 of Contact Magazine mailed July 23, 2004. Yes, I have heard of Jack Norris's book as well, but have not bought a copy for myself yet. Neat props though. I will continue to look into it. Paul Lipps has been involved with the vansairforce.com (RV forum) and has some interesting things to say there regarding current testing on an RV-6.

George
 

sonex293

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I have seem comments between Jack and Paul that indicate they are in agreement on many aspects of prop design. I have Jack's book, but haven't started it yet.

--
Michael
 

Cameron

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I've read Jack's book. It's worth reading if you are fascinated by propellers, how they, work, etc. but, it is different. Its hard to explain what I mean without reading it for youself. It was worth reading though and he does mention Lipps in it. If I remember right, he credits him for designing some very efficient props.

The other book that is packaged in the same volume is quite good as well.
 

pwood66889

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You are quite correct; Mr. Norris has a unique (to say the least) style. Lots of repetition, font changes, bolding, etc. But I believe his thinking is sound.
The problems:
* getting use/a hold of his design computer program
* manufacturing props to those specifications
* testing them out.
Until such is done, I just don't know. It could be a million dollars of engineering for 2 cents worth of improvement.
"A flight test is worth a thousand expert opinions."
'Tex' Johnson

So Lipps' article is from 2004. Doesn't seem to have set the world on fire. At least not around here, where the temps are 40's day, 20's night.

Percy
 

Cameron

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"A flight test is worth a thousand expert opinions."
'Tex' Johnson


A good quote, I like that.
 

gschuld

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I agree, Paul Lipps and his "Elippse" propeller designs certainly have not become part of the mainstream. I understand Vari-prop is to be introducing both constant speed and in flight adjustable propellers designed for "ellipse" blades by Paul. There is at least one RV flying with I believe a fixed pitch Elippse custom prop for testing. I am typically very skeptical when someone claims to re-invent the wheel so to speak, especially in aviation. The fact that his prop designs are on the three fastest Biplane class racers at Reno has to atleast support his design thoeries on some level.
Obviously, comparing high rpm Reno racers and the rest of the general aviation world are not exactly apples for apples. Mr. Lipps did mention that the combiantion of the large chord and high pitch at the root of his propellers tends to slip a bit until enough airspeed is attained for the prop to really bite so to speak. This may be more or less of an issue depending on the specific design and application but a potential of low air speed prop (cavitation?) is a concern. Another issue, mentioned by Percy, is being able to manufacture these props. No matter how you look at it, they are more complicated in shape. As far as I know, all custom "elippse" props build to date are wood core with a very significant fiberglass layup. I believe Craig Catto has built most if not all of the Lipps designed props for the Reno racers. At least one other prop maker has also made props from Lipps designs(don't recall offhand), but I can't imagine that there are too many prop makers out there that are set up to build these custom composite props. I would love to know if an all wood(no glass) 2 blade prop could be built with his design. Perhaps something like a small increase in the thickness of the blade section would be necessary to make up for the potential lost strength, but I would love to see something like an alternating wood(maple/walnut) lamination using 3/16" layers carved into one of his shapes. It would look wild.

George
 

Tom Nalevanko

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I saw Jack Norris at our EAA Holiday Party this evening. He mentioned that he has a website for his book. Check it out: Blank Jack mentioned that he sold about a thousand copies and readers seem to be pleased.

Jack was at the party with Millie, dancing up a storm... They got married in '46 and the next day bought a new Luscombe to fly from Ohio to California. Well the three of 'em are all still together with the plane at KCMA. Super!
Blue skies,
Tom
KCMA
 

Tom Nalevanko

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It is too bad that the forum links a url to the name of the page. In Jack's case, he has not gotten around to naming it so it is Blank. The url is "http://www.propellersexplained.com/"
 

rtfm

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Hi,
So, what's with the underlining, bold, underline AND bold text? Which begs the question - what about the oft-neglected italics? Is this guy some sort of italics hater? What did italics ever do to him? :)

Seriously though - it makes for difficult reading... Can't help the knee-jerk reaction to lable the guy a crank. From what I've read, he isn't a crank (underline intentional, if a little ironic in context). Reading his web site is kinda like stumbling upon a cowboy-era snake-oil advertisment. Now don't get me wrong, I kinda like those old snake-oil guys. But in the 21st century. A little weird...

Duncan
 

Topaz

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Hi,
So, what's with the underlining, bold, underline AND bold text? Which begs the question - what about the oft-neglected italics? Is this guy some sort of italics hater? What did italics ever do to him? :)

Seriously though - it makes for difficult reading... Can't help the knee-jerk reaction to lable the guy a crank. From what I've read, he isn't a crank (underline intentional, if a little ironic in context). Reading his web site is kinda like stumbling upon a cowboy-era snake-oil advertisment. Now don't get me wrong, I kinda like those old snake-oil guys. But in the 21st century. A little weird...

Duncan
Apparently the post to which you're referring has been deleted, but it brings up a little bit of typography information. Since I do this for a living... ;)

Underlining really has no place on a style palette. An underline is simply a proofreader's mark that means "italicize this text". And that's all. Italics are the proper way to emphasize a particular word in a line of text.

Underlining came into use in 'final' text with the invention of the typewriter. Manual and machine typesetting done professionaly even before that time used the italic to emphasize text. But the typewriter, intended as a less-expensive office device, would've required that every character be duplicated in the mechanism to carry the italic version of the letters and numbers, which would be too expensive and bulky for an office device. And that's also how the underscore "_" character came to be invented. It didn't exist until some typewriter manufacturer decided it was cheaper to add one character to the glyph set than duplicate them all in italic. He was protecting his profit margin.

Boldface is just a weight of a particular typeface. Traditionally it was only used for emphasis in headlines and other 'display' type, or in cases where the whole line was set in bold for stylistic reasons. But at least it has a precedent in being used for emphasis. Underlining in typed or typeset text, like using two hypens in place of an em dash ("--" instead of "—"), is just another hold-over from the age of the typewriter, which was a very dark time for typography indeed. Setting two spaces after a period and before another sentence also comes from the nineteeth century, when newspaper typesetters were paid by the line of type—if they could 'pad out' the story with some extra spaces, they got paid more. Might not have a lot of effect in one article, but throughout an entire page... Correct usage is a single space after the period, no matter what your typing teacher told you. ;)

Unfortunately, people got so used to seeing these things done incorrectly that it looks 'normal' to them now. Which is a shame, since doing it the 'right' way really is very much more readable. Just as you've pointed out, Duncan.

[/typographical history rant]

We now return you to your homebuilt airplane design channel. :gig:
 
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pwood66889

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Thanks for the "typographical rant," Duncan.
Yes, I agree that Mr. Norris' use of typography dilutes his message. But I feel his message is valid, in that the science is there.
Percy in NM, USA
 

freedive57

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Norris' book is in need of an editor, desperately. It's still worth reading. I don't know of another book like it. He's an original thinker, and like some other guys in experimental aviation (Kent Paser comes to mind, that Stull guy in Texas, and another Texan, Leeon Davis, etc.), he has accomplished a lot and has shared his experience. I'm glad he wrote the book. It takes some re-reading but will definitely change your thinking about props, and about engine management for efficiency, too.
 

pwood66889

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Like I said, Duncan, Mr. Norris' style is "interesting." It is left as an exercise to the reader to see what he is actually saying. It does make sense when one boils it down.
I stand on what I have said. Some one needs to get that code (GW BASIC, I believe) and build props from it, then test `em out. It could be a world beater for all we know.
Percy in NM, USA
 
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