Hartzell Constant Speed Blended & Not

[Bob Axsom]

Does anyone know the detailed theoretical benefits of the blended airfoil props and the actual high RPM performance difference in both the test environment and the air on an RV. I would just as soon ignore the smoother, quieter and prettier attributes.

Bob Axsom

[Ironflight]

Bob,

Randy did a pretty detailed same-plane comparison on props, and that will at least give you some test results to look at. When I made the decision between the standard and blended airfoil Hartzells, that's where I went, and decided that for a $200 difference, it would be the cheapest 4 or 5 knots I'd ever buy!

Can't help you on the theory....my Aeronautical Engineering education was a long time ago, and CFD was in it's infancy. What little I might remember is probably obsolete....

Paul

[Bob Axsom]

For 5 kts I would be tempted to go the whole ~$5K for a new prop. Do you happen to have Randy's site address?

Bob Axsom

[sprucemoose]

http://www.romeolima.com/RV8/Prop.htm

I think this is the page he's talking about. Lots of good reading.

[osxuser]

He doesn't mention the blended airfoil Hartzell there

[Ironflight]

I guess I have used so many sources over the course of building, I get them confused. It was actually the Fifth 2003 RVAtor that has the article comparing a bunch of props- including the blended airfol....

But it WAS done with Randy's plane! (At least a few of my memory cells still work....


Paul

[Bob Axsom]

I read that article when it first came out but I had already had my prop for three years then so I wasn't about to change at that point. As it is I see that they limited the RPM to 2,500 which is below the peak aircraft speed node I saw at 2600 RPM in a little test I ran with my non-blended prop. The blended airfoil prop looks better at 2500 RPM and may be even "more" better at higher RPM where tip speeds are supposed to start causing inefficiencies. Based on what I know right now I will continue to watch the information that becomes available and probably go to a blended airfoil prop at the next prop overhaul if the information continues to support the supremacy of the blended airfoil prop. In next year's Air Venture Cup I will stay low and run the 500 miles at 2600 RPM, max power lean.

Bob Axsom

[avpro56]

Originally Posted by Bob Axsom

I read that article when it first came out but I had already had my prop for three years then so I wasn't about to change at that point. As it is I see that they limited the RPM to 2,500 which is below the peak aircraft speed node I saw at 2600 RPM in a little test I ran with my non-blended prop. The blended airfoil prop looks better at 2500 RPM and may be even "more" better at higher RPM where tip speeds are supposed to start causing inefficiencies. Based on what I know right now I will continue to watch the information that becomes available and probably go to a blended airfoil prop at the next prop overhaul if the information continues to support the supremacy of the blended airfoil prop. In next year's Air Venture Cup I will stay low and run the 500 miles at 2600 RPM, max power lean.

Bob Axsom

Bob:

I ran the Hartzell HC-C2YK C/S prop for about 55 hours and changed to the blended airfoil prop (HC-C2YR) just before the AirVenture Cup 05 Race. I did see an increase of about 2-3 kts to top speed after installing the blended airfoil prop. Nice thing about it was that all I had to do to make the change was to install a new front bulkhead on the spinner. Everything else was bolt on.

The other nice benefit was that the continous operation below 2250 RPM limitation was removed.

The HC-C2YR prop comes in two lengths, 72 or 74 inch. I bought the 74 inch thinking that if I ever needed to cut down the prop blades 1 inch I could.

Hartzell wanted big money for the Blended Airfoil prop. I tried to buy it through Van's, but their agreement with Hartzell only allowed one propeller to each RV builder at OEM prices. I politely complained about this policy to Hartzell management; I told them that my purchase was an "upgrade" to a newer style propeller and that they shoud consider changing their policy. To my surprise they relented, and informed Van's that I would be allowed the OEM pricing. Van's put me in touch with a few builders, and I managed to swap delivery times with an RV-7 builder in California. Still, it took 4 weeks to get the new propeller.

Is it smoother? Not sure, because I had gone to great effort to dynacically balance both props with my Aces 2020 Balancer. It does look nicer, but of course that has nothing to do with performance. The one drawback is that I like to use a urethane "Prop Gaurd" on my propellers; I have not put one on this prop yet because it looks like it may be too curved out towards the tip to accept the urethane cover. Perhaps I can get the Prop Guard to fit; we shall see.

Best Regards,
Jon Ross
Race 27
Formula RV Blue Class Winner 05

[Bob Axsom]

What great information! It looks like I have to have one - I can't ignore the credibility of your findings. Thanks for pioneering the upgrade OEM pricing as well - that's a great benefit to all of us.

Bob Axsom

[Josep ma]

avpro56 say:

The other nice benefit the blended airfoil prop (HC-C2YR) was that the continous operation below 2250 RPM limitation was removed.

Is that true??
in Vans webStore still say:

**PROP C2YR-1BF/F7496 (I)O-360 (180hp) diameter: 74"
Application: RV-6A, RV-7A, RV-8/8A

**With the following restrictions:
Note: When installed on an engine with magnetos, aftermarket electronic ignition, LASAR system, or FADEC system then the following restrictions apply:
1: Do not operate above 22" manifold pressure below 2350 rpm.
2: Operation above 2600 rpm is limited to takeoff. As soon as practical after takeoff the rpm should be reduced to 2600 rpm or less.
3: FADEC equipped aircraft maximum engine RPM must be limited to 2650 RPM at ALL times.

regads,
Josep Ma
www.telefonica.net/web2/rv7e