ELIPPSE propeller for RVs

[gasman]

Originally Posted by elippse

Don't jump ahead, Roberto! Larry will do lots of before and after testing to see if there is a measurable performance increase to brag about. I'm hoping that the Reno experience is a harbinger of things to come, but let's wait and see.

And Monte, I'm not at all familiar with this hub, but from what Larry tells me, it has seen lots of activity on airboats. Some of you are familiar with the somewhat different shape of my designs, and how the prop has a concave planform taper as it approaches the tip, where it goes to a point. It does not have most of the lift, not thrust, in the outer portions as in most props, but instead, as with an elliptical wing, it has an elliptical lift distribution which goes to zero at the tip, thus minimizing span-wise flow and tip vortex. Since the lift is distributed all along the blade as opposed to being mainly outboard, this should bring about rather benign bending forces at the hub.

Another benefit of this taper is that the mass outboard is considerably reduced, thus greatly reducing centrifugal loading on the hub. Outboard mass reduction also helps when considering the inertial load when the prop is accelerated and decelerated on each power pulse; think of the whip at the tip of a fishing pole when casting. This minimizes the in-plane stresses where the blade emerges from the hub. I think that this is what is taking place on those blades which are having cracking problems from the big power pulses on these IO-360s.

All told, I am hoping that this will not take its place among the many tales of recent CS and ground-adjustable hubs that seem to have these cracking problems. I'm not sure what this thing is about EIs being hard on CS props. LSE ignition has very precise timing on all cylinders, whereas a magneto has somewhat random small variations in timing around a mean. It could be that this very timing precision is able to excite the various resonances in some blades, whereas the magneto would throw off the periodicity somewhat, and so not produce as high an excitation amplitude. But that is really saying that the prop has resonances that are on the borderline of being properly damped.

So far neither Tom on his biplane props nor I on my FP three-blade prop have seen any cracking in the hub region. Klaus is always tapping my prop with a coin in the region where the transition takes place from blade to hub. With my higher pitch angles there, in the 65-70 degree region, the transition angle is not as great as it is on the many props that have root pitch angles of about 45-50 degrees, so there is less twist to the laminate in going from the blade to the hub and so less chance of de-lamination. 'Hope this addressed some of your concerns!

I hope there are many of you attending Reno this year. If you are, be sure to get a pit pass and come see the real world of Experimental Aviation, where it's taking place and not just being talked about. One of my prop designs will be on a Sport plane, two on F1s, and at least four on biplanes. Along with that, one of the racers will have my super-secret compact augmented cooling-exhaust system.

As with my blade designs, when you see this you will have a hard time believing it can work! Just be aware, we have applied for a patent on it! And maybe by Oshkosh, Klaus will be able to show our new dual-redundant EFI. Two sets of drivers, two pressure-controlled pumps that require no return line to the tank. He has been flying this on his plane for three years now, as well as having raced it at Reno twice, and has wowed lots of pilots with its ease of starting on his hand-propped EZ, as well as how well it maintains A-F with change in altitude.

As with the ignition, it's got lots of cool outputs that tell you pump pressure, MAP, and, both pulse and analog fuel flow. Every effort is being made to have a safe product. The control laws are in hardware, there is no software, so except for some minor circuit changes that may arise, there will be no software upgrades to implement from time-to-time.

I am ready for this prop that needs no hydraulic connections.

Where do I find this prop?

[Mike S]

That post is over 3 years old.

[PCHunt]

In the computer industry, this would be referred to as "Vaporware".

[gasman]

Originally Posted by Mike S

That post is over 3 years old.

Correct! So, where is the prop?

[SHIPCHIEF]

I suppose that if you want one you should call Paul L or Craig Catto. Paul L has stated in the past that Catto builds to his design.
Detractors aside, I see no serious downside to trying an Ellipse prop, and at least one RV-6 150 HP has flown with one, so what's the rumble?
I have a Catto 2 blade on mine, but I'm not flying yet. If an Ellipse prop is going to be used on another RV, then someone is going to have to buck up and have it built. It's not like Paul has an obligation to build a generic RV prop any more than other custom prop builders.

[hevansrv7a]

When you call Craig Catto, be sure to ask how his prop did on a Pitts when compared to Paul's, just this year.

[elippse]

The prop I designed for Tony Higa's biplane gave about 4.2mph less at 70 rpm more than his old metal prop. I told Tony that I was disappointed and something went wrong either in the design process or in the making of the prop. I gave him a check at Reno for the full price of the prop and its spinner, but asked him to hold on to it until he gets some drag reduction changes made and then to use this prop for data gathering for another design, at which time he'll return the prop to me so that I can do some measurements to see if it agrees with the design templates at every inch. Was that what you were referring to, Howard?

[fehdxl]

FWIW, here's an Ellipse prop in flight on the way home from LOE today.

http://www.flickr.com/photos/5460059...7625090360814/

Best,

-Jim

[ccrawford]

Originally Posted by PCHunt

In the computer industry, this would be referred to as "Vaporware".

Not sure about that, seeing as I have one.

Originally Posted by gasman

I am ready for this prop that needs no hydraulic connections.

Where do I find this prop?

You can find more information here:

http://www.variprop.com/

[hevansrv7a]

Originally Posted by elippse

The prop I designed for Tony Higa's biplane gave about 4.2mph less at 70 rpm more than his old metal prop. I told Tony that I was disappointed and something went wrong either in the design process or in the making of the prop. I gave him a check at Reno for the full price of the prop and its spinner, but asked him to hold on to it until he gets some drag reduction changes made and then to use this prop for data gathering for another design, at which time he'll return the prop to me so that I can do some measurements to see if it agrees with the design templates at every inch. Was that what you were referring to, Howard?

Paul, I was suggesting that anyone contacting Craig for an Ellipse prop should raise the subject rather than my trying to repeat a fragment of a conversation accurately. I try not to be a pointless detractor nor a gossip. I was not there, at Reno. The conversation that I had was about other things. I admire your honesty in posting this and your "customer orientation", too. As you know, I admire your very impressive wins, but I'm a critic in the sense that you seem, to the uneducated such as me, to be experimenting rather than following proven principles. That's OK as long as it is understood. It worked for Edison. Serendipity has its virtues. You, Craig Catto, Lonnie Prince and many others have produced props with a number of innovative designs. Sometimes they work better, sometimes they don't. That's why we are called experimenters as a group.