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  #1  
Old 06-29-2010, 09:06 AM
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Tony_T Tony_T is offline
 
Join Date: Dec 2008
Location: Lacey, WA
Posts: 1,365
Default Sensenich Prop Adjustment...

The plans say to set the prop pitch full on the initial installation. I followed this instruction, but after torqueing the bolts I referred again to the hub index marks and it looked like they had moved a little. I let it go. My static rpm was 5200, and the first test card indicated that I had ferocious take off and climb (for 83 cubic inches), but was only seeing 102 knots in level flight at 5500 RPM, with enough throttle left to overspeed the engine. My prop was definitely underpitched.
I contacted Van's for more advice on pitching the prop, and found out that Scott will have an in-depth article in the next RVator of their experience with this prop and how to adjust it. Scott also made a fixture of scrap alum angle that contacts the trailing edge and back of the blade and then uses a digital level to measure the blade angle.
I took Scott's idea and modified it a bit to come up with my version of the MPPF (McDaniels Prop Protractor Fixture). This little fixture contacts the trailing edge of the blade and the back of the blade in 3 places and uses Scott's sighting notch to line up with the paint strip on the front of the blade.
Scott, I hope you don't mind me going on like this about your idea, but it really is a good one.


I found a nice little digital level on the internet for $24.99 and it even has a tripod screw attachment so I could bolt it to the MPPF:


Here is the protractor in use:


I found the device to be repeatable to about 0.1°. And, I found my blades to be 1° different from each other! That is way too much. The Sensenich instructions say to set the blades within 0.25° of each other if you have a protractor. I was able to readjust the pitch and set the blades to within about 0.1° of each other.
I am now getting 115 knots at 5360 (without pants), and the engine will not pull more RPM in level flight, so I may be slightly over pitched. I think I will leave it this way for a while until I get more time on the motor, then make a final adjustment.

So, it looks like that small amount of adjustment we are restricted to by the stops in the hub are ideal for this aircraft. But, the hub index marks are rather crude and you need a protractor to do the job well.

Thanks Scott, for your great idea, and I am sure everyone will be looking forward to the next RVator.

Tony
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E-LSA RV-12 ULS

Last edited by Tony_T : 02-14-2012 at 10:16 AM. Reason: spelling
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  #2  
Old 06-29-2010, 11:29 AM
Peterk Peterk is offline
 
Join Date: Mar 2008
Location: Texas
Posts: 1,378
Default Good Job

Awesome Tony! What is your static WOT now? I have mine at 4900 but that simply by lots of trial and error...I like your idea better. Plus I didn't know the blades could be different angles...I thought when you move one, the other moves as well. How do you alter that? Thanks.
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  #3  
Old 06-29-2010, 11:58 AM
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Geico266 Geico266 is offline
 
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Location: Huskerland, USA
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Default

Sure beats the trial and error method! Very cool Tony!
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Last edited by Geico266 : 06-29-2010 at 10:02 PM.
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  #4  
Old 06-29-2010, 01:03 PM
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MartySantic MartySantic is offline
 
Join Date: Apr 2008
Location: Davenport, IA
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Default

Sounds like a very good idea!! Thanks!!

Also a lot of good info on setting the prop in these two threads.

http://www.vansairforce.com/communit...rop+protractor

http://www.vansairforce.com/communit...rop+protractor
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RV-12 N128MS ----- Now Flying
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  #5  
Old 06-29-2010, 03:07 PM
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MartySantic MartySantic is offline
 
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Default

Quote:
Originally Posted by Peterk View Post
Awesome Tony! What is your static WOT now? I have mine at 4900 but that simply by lots of trial and error...I like your idea better. Plus I didn't know the blades could be different angles...I thought when you move one, the other moves as well. How do you alter that? Thanks.
It is true if you move one blade the other will also move but if you depend on that, the blade pitch can easily be one degree different, blade to blade. You have to use a protractor or Scott's/Tony's fixture and a digital level. Great idea!!
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  #6  
Old 06-29-2010, 08:28 PM
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Tony_T Tony_T is offline
 
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Location: Lacey, WA
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Default

Quote:
Originally Posted by Peterk View Post
Awesome Tony! What is your static WOT now? I have mine at 4900 but that simply by lots of trial and error...I like your idea better. Plus I didn't know the blades could be different angles...I thought when you move one, the other moves as well. How do you alter that? Thanks.
My static RPM was 4900 but there was some wind blowing at the run-up area, so it may actually be less. I am going to adjust to produce airspeeds anyway, I would like to have a fast cruise close to the 120 knot limit (with pants) and a comfortable cruise at about 100-105 knots about 4900 RPM.

Like Marty says, there is enough play in the hub system that the blades can be 1? different from each other even though they are designed to move together.

Make the protractor. There are commercial ones to consider, but this one works and, for me, making stuff is what "experimental" is about .

Tony
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  #7  
Old 07-05-2010, 09:22 PM
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Jetguy Jetguy is offline
 
Join Date: Aug 2008
Location: Texas, Fort Worth
Posts: 1,237
Default Prop Adjustment

I followed Your lead and bought the Sears Craftsmen Digital Torpedo level and set it up in a similar method and found my prop off .8 Degrees between the two blades. After a fine tune adjustment I cant say for sure I am going faster but it does seem like the engine is running much smoother.

http://www.sears.com/shc/s/p_10153_12605_00948295000P

John
RV12 N1212K
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  #8  
Old 07-06-2010, 04:40 AM
meadeduck meadeduck is offline
 
Join Date: May 2008
Location: Marietta, Ga.
Posts: 220
Default prop adjustment

We loosened the prop adjustment, strapped a laser pointer on the blade, rotated the blade to each end of its extreme and made a mark on the ground at each extreme point. Then we divided the distance on the ground into even increments and made an appropriate adjustment. We repeated the measurement for the other blade.
Meade and George
N612RV
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  #9  
Old 08-18-2010, 03:04 PM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,070
Default Packing Crate Prop Protractor

Packing crate Prop Protractor

I made a prop protractor out of scrap wood from the packing crate. The protractor touches the prop at two points. If you want to be technical, it is actually 3 points if you count the left and right ends of the little 2" square piece of plywood fastened to the bottom of the 2x2. Fastening the plywood with one screw will allow the plywood to be rotated to align with the prop. The forward end of the 2x2 should be slightly heavier than the aft end in order to keep the vertical 2x2 in contact with the prop. A piece of painter's tape located 22.5 inches from each prop end serves as a left - right alignment indicator for the protractor. The end of the prop needs to be exactly the same distance from the floor every time the pitch angle is measured. Even though I filed away the vertical 2x2, it is not necessary to make it curved. Straight is OK. I filed it because I fastened the vertical 2x2 too close to the prop. The relative pitch is measured with a ruler from the oil tank up to the 2x2. The actual angle of pitch is not known. But it is easy to measure (in distance) the span from course to fine pitch and to measure difference, if any, between the two blades. The object is to have both blades pitched at exactly the same angle, whatever it is. As long as the distance between the oil tank and the 2x2 remains the same for both blades and is repeatable each time the prop is rotated 180 degrees, then it must be accurate. No matter how the pitch is measured, the results must be repeatable to assure accuracy. The distance from the prop to the oil tank is about 24 inches. A small change of pitch results in a big change in distance between the oil tank and the 2x2. That is what gives the packing-crate-prop-protractor a high resolution. A 1/32" measurement error at the oil tank translates into 0.075 degree pitch error. If a builder prefers a laser level, he could still make a similar wooden bracket to hold the level. The laser level could either sit on top and be aimed at the wall or be fastened to the vertical side and be aimed at the floor.
I temporarily replaced the nord-lock washers with hardware store washers while adjusting the prop. That allowed me to tighten and loosen the bolts several times without fear of wearing out the bevels on the nord-lock washers. After I was satisfied with the pitch angle, I loosened one bolt at a time and put the nord-lock washers back in.
Joe
Update 11-7-2011 The packing crate protractor is NOT very accurate. I now use a laser level aimed at the floor.
See Picture:
http://public.bay.livefilestore.com/...tor.jpg?psid=1

Last edited by Mich48041 : 11-07-2011 at 06:29 AM. Reason: Added Update
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  #10  
Old 08-18-2010, 05:23 PM
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MartySantic MartySantic is offline
 
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Default

Joe.....Well done. You are sure resourceful!!
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