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Prop Pitch

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george.mueller(at)aurora.
Guest

Posted: Mon Dec 01, 2008 6:46 am Post subject: Prop Pitch

Is there anyone on this list with a flying 701 with a Rotax 912UL (80HP) and a warp drive three blade prop?  What pitch (measured at the tips) do you have on the prop and what kind of climb and cruise are you seeing?  With me (230 lbs), my BRS chute and full tanks I am about 50 lbs shy of gross and am seeing 500 fpm climb and 75 mph cruise at about 5400 rpm.  Is this normal performance?  I only have about 5 degrees pitch on the prop which gives me 5650 rpm with full throttle in straight and level flight at about 2000 MSL. 

 

 

 

George in Milwaukee 

N701GM  55hours flying

 

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John75142

Joined: 05 Dec 2007
Posts: 56
Location: Kaufman, TX

Posted: Mon Dec 01, 2008 7:46 am Post subject: Prop Pitch

Seems like I recall others setting (at) 12 deg. but not 100% sure as I do not  have this set up.

  

 John (Scratch building 701) 50% done/100% to go

Kaufman, Tx

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_________________
John Short

zsmith3rd(at)earthlink.ne
Guest

Posted: Mon Dec 01, 2008 8:50 am Post subject: Prop Pitch

George,



I'm in the office, not anywhere near a prop, so this is from faint memory.



First of all, I do recall that it was something on the order of 15 degrees but definitely not measured at the tip.

Mine is a 912, three-blade Warp Drive, RPM limited to 5500.



Long version of old story:

Prop came with the Warp protractor, but at the time an old WWII pilot/crop duster/A&P was still alive and offering advice.  

He loaned me a high-dollar prop protractor complete with wood case, and promised to hurt me if I damaged it.

He offered that any protractor needs to be placed at the 'widest' place on a prop in order that the protractor sit across as much width as possible to insure repeatable measurements.

He went on to instruct that the blade being adjusted need to be 'level' using a small bubble level each time, and at the same point on each blade; that the 'number of degrees' will vary from station to station along the blade, and what ends up being 'correct' is what you get.

Said differently, because the 'twist' in the blade changes as you move outboard, the resulting protractor reading changes as you move it along the blade.  Therefore, according to this receipient of the 'Charles Taylor Award', you simply pick a wide place, mark it with masking tape (on each blade) and apply the protractor.

Following his instructions, I set mine, then fired it up.  Had too much at 20 degrees, so I reduced it 2 degrees and tried again.  Still too much.  After three more attempts I was satisfied.

A run-up on the ground gave me 5400 and slid the tires on wet grass.  On takeoff it would go to 5500 RPM at about 40 knots, but never above about 5550.



The preceeding was on a pusher airplane.  On the 701 (same engine, tractor prop) I've not done a final setting, but did set the pitch a few degrees too much specifically to limit RPM until I'm ready to adjust it.



One other comment about measuring at the tip:  My old friend was really specific about NOT using a narrow portion of the blade.....too easy to have one or two degrees difference between blades and then have them tracking all over the place. He stressed that placement of the measuring device will dictate the 'reading' you get; and that the pitch YOU get may not agree with what some other fellow gets who placed his protractor at a different station (distance from the hub) on the same prop.

Hope this makes sense!  



Have a great week, best regards, and surely somebody will jump in with truth & justice!



Zed

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zsmith3rd(at)earthlink.ne
Guest

Posted: Mon Dec 01, 2008 8:51 am Post subject: Prop Pitch

George,



I'm in the office, not anywhere near a prop, so this is from faint memory.



First of all, I do recall that it was something on the order of 15 degrees but definitely not measured at the tip.

Mine is a 912, three-blade Warp Drive, RPM limited to 5500.



Long version of old story:

Prop came with the Warp protractor, but at the time an old WWII pilot/crop duster/A&P was still alive and offering advice.  

He loaned me a high-dollar prop protractor complete with wood case, and promised to hurt me if I damaged it.

He offered that any protractor needs to be placed at the 'widest' place on a prop in order that the protractor sit across as much width as possible to insure repeatable measurements.

He went on to instruct that the blade being adjusted need to be 'level' using a small bubble level each time, and at the same point on each blade; that the 'number of degrees' will vary from station to station along the blade, and what ends up being 'correct' is what you get.

Said differently, because the 'twist' in the blade changes as you move outboard, the resulting protractor reading changes as you move it along the blade.  Therefore, according to this receipient of the 'Charles Taylor Award', you simply pick a wide place, mark it with masking tape (on each blade) and apply the protractor.

Following his instructions, I set mine, then fired it up.  Had too much at 20 degrees, so I reduced it 2 degrees and tried again.  Still too much.  After three more attempts I was satisfied.

A run-up on the ground gave me 5400 and slid the tires on wet grass.  On takeoff it would go to 5500 RPM at about 40 knots, but never above about 5550.



The preceeding was on a pusher airplane.  On the 701 (same engine, tractor prop) I've not done a final setting, but did set the pitch a few degrees too much specifically to limit RPM until I'm ready to adjust it.



One other comment about measuring at the tip:  My old friend was really specific about NOT using a narrow portion of the blade.....too easy to have one or two degrees difference between blades and then have them tracking all over the place. He stressed that placement of the measuring device will dictate the 'reading' you get; and that the pitch YOU get may not agree with what some other fellow gets who placed his protractor at a different station (distance from the hub) on the same prop.

Hope this makes sense!  



Have a great week, best regards, and surely somebody will jump in with truth & justice!



Zed

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Tommy Walker

Joined: 12 Jan 2006
Posts: 442
Location: Anniston, AL 36207

Posted: Mon Dec 01, 2008 12:05 pm Post subject: Re: Prop Pitch

Hi George,



We finally set our Warp Prop at 12 degrees at the tip using the warp protractor and the prop blades level.  At gross weight with me an a pax, full fuel, we get about 5350 rpm on climout at 60 mph and 850-900 fpm (assuming our VSI is correct).  We can easily go to 5500 rpm in level flight at max throttle.  we are cruising around 70-75 at 4800 rpm.  We have a 912ULS 100 HP.



Regards,



Tommy Walker

Do Not Archive.

PS I like Zed's idea.  You could measure one blade at 12 degrees at the tip, then check the measurement at the widest part of the blade, then do the other two at that setting.



[quote="george.mueller(at)aurora."]Is there anyone on this list with a flying 701 with a Rotax 912UL (80HP) and a warp drive three blade prop?  What pitch (measured at the tips) do you have on the prop and what kind of climb and cruise are you seeing?  With me (230 lbs), my BRS chute and full tanks I am about 50 lbs shy of gross and am seeing 500 fpm climb and 75 mph cruise at about 5400 rpm.  Is this normal performance?  I only have about 5 degrees pitch on the prop which gives me 5650 rpm with full throttle in straight and level flight at about 2000 MSL. 

 

 

 

George in Milwaukee 

N701GM  55hours flying

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_________________
Tommy Walker
N25A - Anniston, AL

b.carl@sympatico.ca

Joined: 20 May 2008
Posts: 77

Posted: Sun Dec 07, 2008 6:10 pm Post subject: Prop Pitch

I've got a 912 ul with 70" WD 3 blade but my config  is Amphibs. I often fly at or near gross of 1200# and like to set 8.5 to 9.5'  as a compromise for climb and  cruise.

 This should give you 5100-5200 static on  ground.

 Carl

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