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  #11  
Old 06-04-2011, 06:10 PM
vernhendershott vernhendershott is offline
 
Join Date: Dec 2007
Location: Spruce Creek, FL
Posts: 370
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Quote:
Originally Posted by Driftdown View Post
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?
Here it is again:

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

If it does not work it is the first link in the third message in this thread.

Best regards,
Vern

Last edited by vernhendershott : 06-04-2011 at 06:13 PM.
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  #12  
Old 06-04-2011, 08:18 PM
dick seiders dick seiders is offline
 
Join Date: Jan 2006
Posts: 875
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Tried a Warp Drive protractor on my prop today. Appeared to be about 4 degrees of total travel (19 to 23). Set it up at midpoint (21). Static run up at 4900. Climb out at 5050, At level off rpms moved to 5400. Back to drawing board.
Reset prop 1/2 degree further into pitch (20.5). Static run 4950. Climb out 5300. Rpm quickly moved to 5600m on nose level then ran into some wind shear (very bouncy) so throttled back to 5000, and engine sounded rather strange like maybe a fuel problem. Each time I gave it more throttle it was ok then reducing rpms resulted in more weird sounds .Headed back to runway rather quickly in case there was about to be a problem. A number of local airport advisors told me I was experiencing prop flutter which they defined as the prop unloaded (neither pulling nor pushing) on the gear box which creates the sound and a little vibration.
Any of you ever have it? At any rate I liked it so very little I reset the prop again, and getting a bit more aggressive moving the blades I discovered there is 5 degrees of total travel. I used my aiming point at number 3 mark on the hub (Sensenich recommendation) and wound up about 3.4 (which coincidentally is where it was before I changed the hub). In degrees that tranlated to 19.9 on the range of 18 to 23. (the blades can easily be set within 1/4 of 1 degree). I will post results of flight test planned for tomorrow.
Appreciate any feedback
Dick Seiders 120093
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  #13  
Old 06-04-2011, 08:55 PM
BigJohn BigJohn is offline
 
Join Date: Nov 2008
Location: Gloversville, NY
Posts: 1,470
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Dick,

In my experience it is important to get the two blades set to as close as possible to the same pitch. Using the little fixture I built and a digital level I can set my blades to within .1 degrees of each other. That will minimize vibration. As to the pitch angle that you want, it depends on whether you are looking for best climb performance or best speed at cruise. Your static runup at 4900 is a bit low - that would give you a real cruise prop. My advice is to come close to a static runup of around 4950 to 5000, with the blades set as close to the same pitch as you can get it. Then fly it for a while. You may need to adjust the pitch again after you get 20 or 30 hours on the engine.

When you are checking the WOT static RPM try to do it in a no wind condition. Any wind at all will affect the RPM you get.

As to the "noise" - not sure. Haven't heard it. How bad was the turbulence? Try the same test in calm conditions.

One last comment. I had a dynamic prop balance done, and it made a HUGE difference in vibration level. But first, get those blades set equally.

Best of luck to you - I find this "tweaking" phase enjoyable.

John
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John Peck, CFII, A&P, EAA Tech Counselor, Flight Advisor.
RV-12 N37JP 120176 Flying since 2012.
VAF paid through 10/2017. Best bargain in town.
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  #14  
Old 06-05-2011, 05:28 PM
dick seiders dick seiders is offline
 
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Test flight #1 today was with prop indexer set at 3.4. Static run was 5050 rpm. Climb out at 5350. Level off and quickly went to 5500. Speed 110 kts. I experienced 3 small burbles that were very short duration compared to flight the day before. When the burble occurred the rpm dropped from 4750 to 4700, and immediatly returned to 4750 when burble stopped. Still don't know what that is. Could be a very small amount of moisture in gas, or maybe the prop blades were not in sync. Don't know just guessing.THe burble occurred only one time before several weeks ago when during climb out I turned from rt crosswind to rt downwind. Wind speed was about 8 kts. Change in direction of wind on prop maybe created the burble? Yesterday the winds after climb out were very turbulent when the burbles occurred. Anyway back to the prop. For test flight two I reset the indexer to 3.7 by making a very small move to increase pitch. The entire movement of indexer is only about 1.5 increments. Static was 4950. Climb out at 5050. Temp on the ground 33C. When leveled off I could get 5800 wot. Temp at 3000 was 26C and my cruise at 5500 was 118 kts. No burbles occurred. That's the best cruise I've had thus far. Conclusion: I like the performance generally. I still prefer a little better climb out but I believe air density was around 3500 so that likely affected it significantly. I plan to fly it for a while at this setting. Later may try to tweak it a bit to the climb end, but maybe not. 118 kts true w/o wheel pants is pretty good. Comments appreciated. Thanks.
Dick Seiders 120093

Last edited by dick seiders : 06-05-2011 at 06:44 PM. Reason: 3.0 changed to 3.4 added spd of 110 kts.
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  #15  
Old 06-05-2011, 06:24 PM
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MartySantic MartySantic is offline
 
Join Date: Apr 2008
Location: Davenport, IA
Posts: 1,369
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Dick,

The burble (shudder, hesitation or engine miss) sounds very similar to what I experienced and may have nothing to do with the prop adjustments you are making.

In fact, the momentary engine shudder with a gas smell in the cockpit that I experienced came on my flight just after a prop pitch adjustment. So far it has not recurred after draining all of the gas (I put it in the car) and added fresh gasoline from a high volume station. My problem may have been vapor (bubbles) in the fuel lines. Download the data from the Dynon, import the data into Excel and plot the RPMs, fuel pressure and fuel flow. Pressure oscillations and wild fuel flow changes not related to an RPM change could mean you have seen a problem similar to mine.

See my thread.... http://www.vansairforce.com/communit...ad.php?t=72330

As far as prop pitch goes, setting the prop using the index marks, the bubble protractor is not the way to go. I used the bubble protractor and found using a fisture and a digital level, the blades were close to 1 degree apart. See this thread.... http://www.vansairforce.com/communit...djustment+tool
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Last edited by MartySantic : 06-05-2011 at 06:26 PM.
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  #16  
Old 06-05-2011, 06:51 PM
dick seiders dick seiders is offline
 
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Thanks, guys. I will fab. the holder and digital level to insure blades are same angle.
Dick Seiders
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  #17  
Old 06-05-2011, 07:10 PM
BigJohn BigJohn is offline
 
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Location: Gloversville, NY
Posts: 1,470
Default I agree with Marty....

... I don't think the hesitation is due to the prop. Why not try a test flight with some 100LL. Even if you don't like the idea of using 100LL full time, one tank won't hurt anything.

Your pitch setting sounds about right for now. Only change it if you find the blades do not match.

How is the vibration level? Do you feel any shaking in the stick? If you do, consider getting a dynamic prop balance. It made a huge difference in my airplane.

John
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RV-12 N37JP 120176 Flying since 2012.
VAF paid through 10/2017. Best bargain in town.
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  #18  
Old 06-05-2011, 07:51 PM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 2,534
Default Engine burbles

I agree with Marty and BigJohn. The fuel is forming little bubbles (vapor) either in the fuel lines or in the carburetor bowl. The problem is most prevalent at full throttle on a hot day, especially during climb out on second takeoff when the engine (and fuel) is hot from the prior flight.
Joe Gores
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  #19  
Old 06-06-2011, 12:01 PM
JohnF JohnF is offline
 
Join Date: Jan 2005
Posts: 458
Default Prop Hub

I have been adjusting, then flying the RV-12 with trial and error Sensenich ground-adjustable prop blade settings. I believe I now have the prop about where it should be. Here are the results of today's trial from KANK airport at 7525-ft msl, density altitude 9,800-ft:

Take off climb at 68-mph WOT showed 5,040 rpm (climb rate 650 fpm +)
Level flight WOT at 8.870-ft msl showed 5,550 rpm
Two 180-degree legs at 5,250 rpm showed showed
IAS 110/110
TAS 129/127
GPS 142/121

Will leave things as they are and check again from time to time.

Last edited by JohnF : 06-06-2011 at 12:41 PM. Reason: correstion/addition
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  #20  
Old 06-06-2011, 07:22 PM
dick seiders dick seiders is offline
 
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Big John, no vibration of any significance. I plan to have prop balanced after flying enough hrs to find that I am satisfied with the pitch. I think the burble may have been a combination of wind, change in throttle setting, and maybe the prop blades being unmatched a bit. After last set of pitch I could not reproduce the burble using the same remaining fuel I've had in the tank for all four test flights.

John F., wow on the TAS. I would'nt change anything either.
Dick Seiders
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