VAF Forums

VAF Forums (https://vansairforce.net/community/index.php)
-   RV-12/RV-12iS (https://vansairforce.net/community/forumdisplay.php?f=73)
-   -   Refining Prop Pitch... (https://vansairforce.net/community/showthread.php?t=159962)

Piper J3 04-27-2018 11:23 AM

Refining Prop Pitch...
 
I?m trying to find optimum prop pitch for my RV-12/912 ULS/320TT. Most of my flying is below 4000 MSL and airport is 870 MSL grass runway. If I?m going somewhere I?ll flight plan ~ 7000 MSL.

I?ve been adding a couple tenth?s degree pitch and today I have performance listed in table below with one person aboard and half fuel.

Engine is running smooth and seems happy. Temps are all good.

Question - Do you think 4920 rpm is too slow for full power climb?
-

rvbuilder2002 04-27-2018 01:11 PM

Quote:

Originally Posted by Piper J3 (Post 1256025)
Question - Do you think 4920 rpm is too slow for full power climb?
-

I do.

You have likely crossed over to the coarse side of ideal, where additional pitch wont really give you any more speed but will degrade climb.

Driftdown 04-27-2018 02:23 PM

For overall best performance (climb and cruise) the best RPM is 5600-5650, set at wide open throttle (WOT), flown straight and level, at your typical cruise altitude. Here in Florida, that is 3500 ft MSL for me.

scottmillhouse 04-27-2018 04:23 PM

I agree, way too coarse. I wasted a lot of time way over pitching mine but at that climb RPM I was seeing 128 knots at 5500 with Dynon Betty yelling at me for going too fast. Flattened a lot to about .2 coarser than Van recommends getting about 5080 at 75 knots but I climb after initial about 85 closer to 5200. My SNF trip at 3500' solo I was seeing 120 TAS at around 5360 at 25.4 MP. Hot weather and time will tell on climb performance but for now it appears I gained about 5 knots in cruise for my long cross countries from my initial pitch setting.

At this pitch I'm also getting 5600- 5700 WOT at around 3500', goes to redline above.

DHeal 04-27-2018 05:38 PM

Over-pitching your prop has the potential to damage your engine. See Figure 1 of ROTAX's SL-912-016R1 at:

https://legacy.rotaxowner.com/si_tb_...912-016-r1.pdf

I use the numbers Driftdown noted above and am happy with the balanced climb/cruise performance.

Phantom30 04-27-2018 10:35 PM

I?ve played around both over and undered pitched....finding Van?s recommended pitch of 71.4 to be dead on for overall performance.

Finding a good digital level was a trip, but once I got one. I can dial in both blades to within .1 degree of each other.

Driftdown 04-27-2018 11:13 PM

Quote:

Originally Posted by Phantom30 (Post 1256152)
I?ve played around both over and undered pitched....finding Van?s recommended pitch of 71.4 to be dead on for overall performance.

Give us some performance numbers.
During straight and level flight, what is the maximum achievable engine RPM, when throttle is wide open?
At that maximum RPM, what is your indicated airspeed?
During the takeoff run, at full throttle, what is your RPM at rotation?
During climbout, at that RPM, what is the climb rate (and airplane weight)?

Phantom30 04-28-2018 06:35 PM

Quote:

Originally Posted by Driftdown (Post 1256153)
Give us some performance numbers.
During straight and level flight, what is the maximum achievable engine RPM, when throttle is wide open?
At that maximum RPM, what is your indicated airspeed?
During the takeoff run, at full throttle, what is your RPM at rotation?
During climbout, at that RPM, what is the climb rate (and airplane weight)?

Will give info in a few days...as i?m On my way down from Idaho to get plane in Phoenix.

joedallas 04-29-2018 05:15 AM

Best digital leval
 
Ric

I would like to know what digital level you used to get them that close.

Thanks

Joe Dallas




Quote:

Originally Posted by Phantom30 (Post 1256152)
I?ve played around both over and undered pitched....finding Van?s recommended pitch of 71.4 to be dead on for overall performance.

Finding a good digital level was a trip, but once I got one. I can dial in both blades to within .1 degree of each other.


DaleB 04-29-2018 06:59 AM

Quote:

Originally Posted by joedallas (Post 1256401)
I would like to know what digital level you used to get them that close.

I bought this one (https://www.amazon.com/gp/product/B006JR8XBG). It claims 0.05 degrees resolution with +/- 0.2? accuracy. Needless to say I was skeptical and ready to return it.

What I have found is that, while I can't speak to its absolute accuracy in every situation, it is dead on at 0 and 90, at least as close as I can test it. More importantly to me, its measurements are perfectly repeatable. The same angle will measure exactly the same, every time.


All times are GMT -6. The time now is 04:49 AM.