FYI: New SB 18-07-05 on RV-12 Sensenich Props
DHeal joedallas Well Known Member DonFromTX Well Known Member DaleB Well Known Member TomVal Well Known Member
Looking at this photo, I’m struck by three things. 1- The surface finish of the entire part (ignoring the paint) is riddled with irregulaities- not done to...
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Van's Air Force
Thats what I did but the plane needs to be exactly level

Not so… Refer to Page 07 of Section 47 Construction Drawings. The plane does not need to be level at all and can even change angle between measurements.

The prop pitch angle is relative to the canopy longeron regardless of aircraft level. Each time the prop is moved recheck the digital level on the longeron before measuring the blade pitch. If the aircraft “level” has been disturbed while moving the prop simply re-zero the digital level on the canopy longeron before continuing to measure blade pitch.

It is not necessary to remove spark plugs or even upper cowling.

Tools required include a good quality bubble level and two wooden spacer blocks to level prop hub. Mark blocks L-R, forward and top-side so they are placed same exact position on hub each time. Likewise, mark bubble level so it is not “reversed” for each use.

I use Vans sheet metal TOOL-00002 Prop Pitch Bracket and same Craftsman Multifunction Digital Torpedo Level # 48295 as shown in construction drawings. For each measurement of blade pitch first place digital level on longeron and verify zero and re-zero if necessary. Next place the magnetic base of the digital level on the Prop Pitch Bracket (PPB) and finally place digital level/PPB onto the prop. Use gentle finger pressure to seat the PPB against the front edge of the prop.

I have not found tightening of the front prop hub to influence final blade angle. I snug only outer bolts and leave center bolts loose while adjusting blade pitch. When one blade pitch is correct, snug outer bolts even further before setting second blade.

Total time for above procedure is approximately 30 minutes and will attain relative pitch between both blades to within 0.1° angle.

Not With my Inclinometer

SPI

0.10 dg Resolution Digital Combination Protractor and Inclinometer

SPI Tronic Price $243.97

0.10 dg Resolution Digital Combination Protractor and Inclinometer

Accuracy (Degrees) 0.1 (Level 10 ); 0.1 (Plumb 10 ); 0.2 (Maximum Error)

.1 Degree = 6 minute arc . 2 Degree = 12 Minute arc

With four moves of level and the built in error of .2 in the level how is this possible ?

Keeping the aircraft level makes this more possible ?

MY view

Joe Dallas

Not so… Refer to Page 07 of Section 47 Construction Drawings. The plane does not need to be level at all and can even change angle between measurements.

The prop pitch angle is relative to the canopy longeron regardless of aircraft level. Each time the prop is moved recheck the digital level on the longeron before measuring the blade pitch. If the aircraft “level” has been disturbed while moving the prop simply re-zero the digital level on the canopy longeron before continuing to measure blade pitch.

It is not necessary to remove spark plugs or even upper cowling.

Tools required include a good quality bubble level and two wooden spacer blocks to level prop hub. Mark blocks L-R, forward and top-side so they are placed same exact position on hub each time. Likewise, mark bubble level so it is not “reversed” for each use.

I use Vans sheet metal TOOL-00002 Prop Pitch Bracket and same Craftsman Multifunction Digital Torpedo Level # 48295 as shown in construction drawings. For each measurement of blade pitch first place digital level on longeron and verify zero and re-zero if necessary. Next place the magnetic base of the digital level on the Prop Pitch Bracket (PPB) and finally place digital level/PPB onto the prop. Use gentle finger pressure to seat the PPB against the front edge of the prop.

I have not found tightening of the front prop hub to influence final blade angle. I snug only outer bolts and leave center bolts loose while adjusting blade pitch. When one blade pitch is correct, snug outer bolts even further before setting second blade.

Total time for above procedure is approximately 30 minutes and will attain relative pitch between both blades to within 0.1° angle.

SPI

0.10 dg Resolution Digital Combination Protractor and Inclinometer

SPI Tronic Price $243.97

0.10 dg Resolution Digital Combination Protractor and Inclinometer

Accuracy (Degrees) 0.1 (Level 10 ); 0.1 (Plumb 10 ); 0.2 (Maximum Error)

.1 Degree = 6 minute arc . 2 Degree = 12 Minute arc

With four moves of level and the built in error of .2 in the level how is this possible ?

Keeping the aircraft level makes this more possible ?

MY view

RV-12 owners who are adjusting their propeller pitch and actually flying their airplane usually learn quickly that the accuracy of the degree value on their tool is not important. Since most people adjust pitch based on what they see for cruise RPM / airplane performance, all that matters is that the reading on the tool be repeatable.

All of the digital levels I have used, regardless of their specified tolerance, have had very repeatable readings. I.E., you can set them down on a fixed / non-movable object (specific spot on your shop floor) for years and it will read the exact same value every time.

So, as long as you use the same tool, and the exact same procedure (always position the digital level on the blade measuring tool the same way, etc.) the measurement value is very repeatable. At least close enough that removal of the prop and re-installation to a specific measurement results in the same max. RPM in the same flight condition, and in this situation that is all that matters.

In the end, we don't need to know whether the pitch value is 70.8 degrees or 70.9 degrees. Only that we know how much change we made, or that we successfully adjusted back to the same # that we were using previously.

As mentioned, if the digital level is always zero referenced to the cockpit side rail (recommended in the RV-12 documentation), then it will never matter where the airplane is sitting when you are adjusting the propeller pitch. You could do it parked on a hill and your desired pitch value (hopefully recorded in your log book) could still easily be set.

BTW, the tightening order/process of the hub bolts does have an influence on the blade angle. as you alternate back and forth on the bolts while tightening, it is rocking the hub back and forth as well. This can move the blade angle very slightly. With practice, you can use this to your advantage as you are coming up on full torque by adjusting your tightening sequence slightly to get the blade to go that last tenth of a degree towards the value that you want.

Because very few digital levels read in hundredths, even if you have the exact same value on both blades there is still a potential for there being a .1 to .15 degree difference (set your digital level on a hard surface and see how much you can lift one end before the value changes to the next tenth). It is for this reason that I always strive to get both numbers the same. Experience has shown that if I do, the level of smoothness is worth the time.

I can set up the blade pitch on an RV-12 in 15 - 20 minutes. I have had some practice but this is attainable by anyone with practice as well.

One important thing that helps a lot is devising some sort of tool that can be hooked on the blade to give you more leverage to rotate it. Our tool is about 3' long. The additional leverage provided by the tool is what allows for making a very small movement in the blade pitch

Not The Point

Scott

I also believe you can set the blades within .1 to .15 degrees to each other,

with proper use of a Digital Inclinometer, same end up, rotation from the same direction and the same place on the prop and only one reference point.

The point of my post was to confirm if you want to be a close as possible and you are using a none precision Digital Inclinometer

KEEP THE AIRCRAFT STATIONARY

MY View

RV-12 owners who are adjusting their propeller pitch and actually flying their airplane usually learn quickly that the accuracy of the degree value on their tool is not important. Since most people adjust pitch based on what they see for cruise RPM / airplane performance, all that matters is that the reading on the tool be repeatable.

All of the digital levels I have used, regardless of their specified tolerance, have had very repeatable readings. I.E., you can set them down on a fixed / non-movable object (specific spot on your shop floor) for years and it will read the exact same value every time.

So, as long as you use the same tool, and the exact same procedure (always position the digital level on the blade measuring tool the same way, etc.) the measurement value is very repeatable. At least close enough that removal of the prop and re-installation to a specific measurement results in the same max. RPM in the same flight condition, and in this situation that is all that matters.

In the end, we don't need to know whether the pitch value is 70.8 degrees or 70.9 degrees. Only that we know how much change we made, or that we successfully adjusted back to the same # that we were using previously.

As mentioned, if the digital level is always zero referenced to the cockpit side rail (recommended in the RV-12 documentation), then it will never matter where the airplane is sitting when you are adjusting the propeller pitch. You could do it parked on a hill and your desired pitch value (hopefully recorded in your log book) could still easily be set.

BTW, the tightening order/process of the hub bolts does have an influence on the blade angle. as you alternate back and forth on the bolts while tightening, it is rocking the hub back and forth as well. This can move the blade angle very slightly. With practice, you can use this to your advantage as you are coming up on full torque by adjusting your tightening sequence slightly to get the blade to go that last tenth of a degree towards the value that you want.

Because very few digital levels read in hundredths, even if you have the exact same value on both blades there is still a potential for there being a .1 to .15 degree difference (set your digital level on a hard surface and see how much you can lift one end before the value changes to the next tenth). It is for this reason that I always strive to get both numbers the same. Experience has shown that if I do, the level of smoothness is worth the time.

I can set up the blade pitch on an RV-12 in 15 - 20 minutes. I have had some practice but this is attainable by anyone with practice as well.

One important thing that helps a lot is devising some sort of tool that can be hooked on the blade to give you more leverage to rotate it. Our tool is about 3' long. The additional leverage provided by the tool is what allows for making a very small movement in the blade pitch

I want to replace the nordlock washers as they seem to be loosing there effectiveness

can anyone tell me the vans part number or the outside diameter as the only ones I can find here ( australia) are only 13.5 mm ( .5" ) diam and I think the originals have a bigger outside diameter

Yes, the Nord-Lock washers used for the prop are a larger OD than the ones normally associated with that size bolt head. I found this out the hard way when I went to a large nut & bolt supplier locally and bought some replacements ... only to find out the outside diameter of the Nord-Lock Sensenich uses on the prop bolts were a much larger OD than the ones that were sold to me at the nut & bolt supply.

I ended up ordering new ones directly from Sensenich ... they were cheap. The Nord-Lock part number printed directly on the washers is 85397-1 and the OD measures out at 21/32" if that helps. Below is a link to my Blog that has a photo of a Nord-Lock washer from Sensenich being measured ... if you zoom in you can clearly see the part number on the washer.

http://www.dogaviation.com/2017/10/the-first-condition-inspection-tips-for.html