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Paul Lipps (designed) "elippse" propellers

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gschuld

Well-Known Member
Joined
May 9, 2007
Messages
438
Location
Toms River, New Jersey
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.


elippse-prop3.jpg


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
 
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