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-   -   New prop hub installation (http://www.vansairforce.com/community/showthread.php?t=72772)

dick seiders 06-01-2011 12:10 PM

New prop hub installation
 
Received new hub,(SB from Sensinich) and installed a day or two ago. When I first installed prop last year I set pitch about 60% of full. Worked fine and climbed like (you know). Followed directions this time and set the prop for full pitch. WRONG!
Just took it up this am . Temp 34 degrees c light crosswind at 6 kts. It took forever to get airborne well anyway about 1000' and it climbed like a man older than me. I believe I was 2 mi. from the field by the time I arrived at 2000'msl. Landing was a treat as well as I could not slow it down, and crossed the fence at 77kts. instead of 55. I guess the point is I am going back to 60% of full before flying again. Just wanted to share this with all as I was quite surprised at the significance of the change in flying characteristics of the RV12 in this prop configuration. Anyone else have any prop stories? They may be helpful to those now building/flying that haven't yet ventured there.
Dick Seiders

DonFromTX 06-01-2011 12:19 PM

But, tell us how fast was it once you got to cruise! I have been surprised at the LACK of prop pitch settings information on this forum. Are there figures someplace that gives one the information he needs to choose a pitch setting? What does Vans recommend?

Tony_T 06-01-2011 12:59 PM

Prop Pitch info...lots available
 
Quote:

Originally Posted by DonFromTX (Post 546941)
But, tell us how fast was it once you got to cruise! I have been surprised at the LACK of prop pitch settings information on this forum. Are there figures someplace that gives one the information he needs to choose a pitch setting? What does Vans recommend?

Hey Don,
There is no lack of discussion on the forum on prop pitch:

http://www.vansairforce.com/communit...ght=prop+pitch
and:
http://www.vansairforce.com/communit...ght=prop+pitch

are just two of many threads with past experience, results, pitch tool, speeds experienced, RVator article, and recommendations by the experts at Van's.

Bottom line -- you need to use a digital prop tool and set the adjustment in small (0.3) increments, until optimized for your mission.

Tony

rvbuilder2002 06-01-2011 01:01 PM

Use the production acceptance procedure
 
If an RV-12 bulder flys all of the prescribed flight tests documented in the P.A.P., it will lead them to an optimized prop. pitch.

dick seiders 06-01-2011 02:42 PM

Lots of interesting information, but I was looking for best approx. position to get good climb rate as well as top speed. Climb to me in the Hotlanta temps. we enjoy here is more importent than top speed. I am in the process of installing wheel pants to help with the speed. The rpms and climb rates mentioned lead me to believe my 60% of full pitch was a good place to be. I usually peaked at 5300 on climb at 75-80 kts with climb rates comparable to my (former) constant speed equipped RV6A, and when leveling off had to reduce throttle to hold the rpms to 5500 max. My speed at 5500 was only 114 kts at 3000 msl however and this am at full pitch made only 116. Of course I didn't fly long today as mentioned earlier as my max rpm was about 4700 on climb and about 4900 -5000 in level flight. That's not a good place to be.
Dick Seiders

vernhendershott 06-01-2011 05:39 PM

Quote:

Originally Posted by dick seiders (Post 546985)
Lots of interesting information, but I was looking for best approx. position to get good climb rate as well as top speed. Climb to me in the Hotlanta temps. we enjoy here is more importent than top speed. I am in the process of installing wheel pants to help with the speed. The rpms and climb rates mentioned lead me to believe my 60% of full pitch was a good place to be. I usually peaked at 5300 on climb at 75-80 kts with climb rates comparable to my (former) constant speed equipped RV6A, and when leveling off had to reduce throttle to hold the rpms to 5500 max. My speed at 5500 was only 114 kts at 3000 msl however and this am at full pitch made only 116. Of course I didn't fly long today as mentioned earlier as my max rpm was about 4700 on climb and about 4900 -5000 in level flight. That's not a good place to be.
Dick Seiders

Hi Dick,

It is hard to get the prop set to exactly the same position each time it is apart due to the very fine adjustment required to get the setting on the first blade and then getting the second blade the same with out moving the first blade again.

I have found that it is helpful to know from your experience what ground static RPM gives you the performance you desire. Here in Florida (flat and sea level) we like about 4900 RPM as a starting point. Van's, if I recall correctly suggests about 4980 RPM. Most of our people want to end up with just being able to make 5500 RPM at full throttle at 1000 feet and we usually end up trying three times to get it right.

Best regards,
Vern

jte65 06-01-2011 08:26 PM

setting the pitch
 
I just received my prop hub back last from the SB repairs last Friday. However, before sending it off, I checked my prior settings. I don't have the digital tool but do have a bubble version. Mine were both set at 21.5 degrees using the prop measuring tool that Tony T and others have described combined with a bubble protractor. When the hub came back, I simply reset them both to exactly 21.5 degrees again. Everything is perfect (static, climb, and full throttle cruise RPM).

Of course, others may have different settings to achieve the same result due to differences in tools and technique being used to measure and set the blades. However, the little "T" tool (as I call it) and bubble protractor have worked very well for me. Very reproducible.

Jeff

dick seiders 06-03-2011 09:48 AM

Thanks to all for the feedback. I will go for the angle checks. Is a tool necessary? Once assuring the prop is in a precise level horizontally can I not just check blade angle with a digital level?
Dick Seiders

vernhendershott 06-03-2011 10:06 AM

Quote:

Originally Posted by dick seiders (Post 547474)
Thanks to all for the feedback. I will go for the angle checks. Is a tool necessary? Once assuring the prop is in a precise level horizontally can I not just check blade angle with a digital level?
Dick Seiders

Hi Dick,

The tool in the following thread only take a few minutes to make from leftover material from the kit. It provides the way to have a firm three point contact on the blade so that you get the same reading each time allowing you to set one blade and check the other to be sure they are the same and know that your readings are both done exactly the same.

http://www.vansairforce.com/communit...ght=prop+pitch

You might also make a prop stand out of one of the 2 x 2 boards that came on the crates. I cut a slot in one end and then cut it to the right length so that the prop is level with the board under one end of the prop. Dead level is not as important as taking the reading the same way on each end. Use the board under the left hand blade at a fixed point under the tip of the prop, take the measurement on the right blade. Then flip the prop over and repeat. This allows one person to do the job even if adjustment is required.

Best regards,
Vern

Driftdown 06-04-2011 04:57 PM

Hey Vern,

Thanks for the post, but the link provided, came back with "The system cannot find the file specified."

Did you pull the plug on the link?


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