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  #1  
Old 09-15-2019, 09:21 AM
cduster cduster is offline
 
Join Date: Aug 2019
Location: Hertford, NC
Posts: 22
Default Curing a slow and hot Rocket: Prop

In the quest to get my HR2 up to speed, I guess I need to learn a little about the prop. It is a Hartzell HC-M2YR-1BF with F8475JH-4 blades. Whats the opinion of this prop, is it the right one for the application?
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  #2  
Old 09-15-2019, 11:11 AM
Pdtofly Pdtofly is offline
 
Join Date: Jan 2012
Location: Reno, NV
Posts: 270
Default HR2 prop and blades

I had the original rounded blades on mine years ago, but replaced them with the blended airfoil ones. I think they run a little smoother. These are what I have on mine now. DHC-M2YR-1 BFPX/F8068DX

Both Mark F. and John H. can hook you up with them.

Brian
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  #3  
Old 09-17-2019, 10:46 AM
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F1Boss F1Boss is offline
 
Join Date: Aug 2006
Location: Taylor Texas
Posts: 777
Default Not quite right

The J blades are for the Glasair 3 - not the Rocket. Sorry!

The blended airfoil blades are much better tuned to the Rocket speeds. If you hustle up, I can get you a prop at 2019 prices. Current delivery is mid - October. Your current spinner will fit up, so you can figure on spending bit over $10K for the newer design prop.
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"Not everyone needs a Rocket. Some folks, however, shouldn't live life without one.
You know who you are."
Budd Davisson, 1997
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  #4  
Old 09-23-2019, 07:56 AM
cduster cduster is offline
 
Join Date: Aug 2019
Location: Hertford, NC
Posts: 22
Default

Quote:
Originally Posted by F1Boss View Post
The J blades are for the Glasair 3 - not the Rocket. Sorry!

The blended airfoil blades are much better tuned to the Rocket speeds. If you hustle up, I can get you a prop at 2019 prices. Current delivery is mid - October. Your current spinner will fit up, so you can figure on spending bit over $10K for the newer design prop.
So, in this part number F8475JH-4, the "J" is the blade shape or twist?

In your opinion, how many knots is this prop costing me? Right now, I think its average TAS at 8500' and 24 squared is just under 180 knots.
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  #5  
Old 09-23-2019, 09:45 AM
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Toobuilder Toobuilder is offline
 
Join Date: Jul 2009
Location: Mojave
Posts: 4,409
Default

Odd. Just looked at my prop log book and my blade pn is 8475J-4. (no "H" suffix to be found). The locals around here including the prop shop and Harmon himself indicate the "J" is the twist and works best on the Rocket.

That said, at 24 squared and 8500 you should be way over 180 KTAS unless you are significantly LOP. That is getting down to RV speeds. At the same altitude and slightly less MP, I routinely saw 200 KTAS at peak EGT. (11.5 GPH). And I'm only running 260 HP.

For those that have flown with both the paddle and Blended blades on the same airplane, can anyone comment on any measurable performance difference?
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

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  #6  
Old 09-23-2019, 10:10 AM
RV Jerry RV Jerry is offline
 
Join Date: Jan 2009
Location: Chino, CA
Posts: 195
Default

A friend of mine switch from J blade to blended airfoil said he saw no difference in speed maybe very slightly better climb but was smoother, I have J blade on my Rocket and am faster than him, this is just one example others may be different
Jerry
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  #7  
Old 09-23-2019, 04:11 PM
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F1Boss F1Boss is offline
 
Join Date: Aug 2006
Location: Taylor Texas
Posts: 777
Default way back when...2011...

A couple fellas got together and decided to actually test different props on one particular plane. I'm trying to recall names - Jim Ayers had a RV3 with a LOM engine in it. That fella is no longer with us.

I am not sure who's ship they did the testing with. Ted Rutherford's? Also passed..

I recall they tried a range of RPM - the std Rocket prop (80"/D blades) was almost the fastest in the end, and the MT 3 blade was not able to keep up. I'd like to have this document for comparison with the current set of props.

The Blended airfoil @ 80" was not included in this test as far as I know, but I could be wrong. I recall one prop simply going faster than the rest as the RPMs came up past 2700..sounds like Reno testing on the BA prop if you ask me.

By golly I found it - left my memory mistakes in the 1st part. I still don't think they tested a BA prop.

http://www.vansairforce.com/communit...ight=jim+ayers

"The flight test data I obtained in a HR2 was with 2 blade Hartzell's and the 3 blade MT propellers.

The HR2 had the "D" twist 2 blade Hartzell, and the owner already knew that at full throttle the aircraft slowed down by 3 mph when going from 2600 RPM to 2700 RPM.

We focused on full throttle performance at 5,000' for the Reno Air Races.

The 3 blade MT Rocket propeller (198-52 blade) was 2 mph faster, but had the same characteristics as the "D" twist 2 blade propeller.
The HR2 slowed down by 3 mph when we went from 2600 RPM to 2700 RPM.

The "J" twist 2 blade Hartzell gave the same performance as the 3 blade MT propeller.
Except, going from 2600 RPM to 2700 RPM, there was a 3 mph INCREASE in airspeed.
And going from 2700 RPM to 2800 RPM, there was another 6 mph increase in airspeed.

This was on a stock 260 hp Lyc. IO-540 engine.

From another source using a 330 hp Lyc. IO-540 engine, this Rocket pilot saw an airspeed decrease when going from 2600 RPM to 2700 RPM using a "J" twist Hartzell.

Sometimes there are no simple answers.

Jim Ayers"
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Mark

"Not everyone needs a Rocket. Some folks, however, shouldn't live life without one.
You know who you are."
Budd Davisson, 1997
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