X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from outbound-mail.nyc.untd.com ([64.136.20.164] verified) by logan.com (CommuniGate Pro SMTP 5.0.3) with SMTP id 871958 for flyrotary@lancaironline.net; Sun, 11 Dec 2005 22:14:32 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.136.20.164; envelope-from=jbker@juno.com Received: from webmail52.nyc.untd.com (webmail52.nyc.untd.com [10.141.27.192]) by smtpout01.nyc.untd.com with SMTP id AABB334ZMAXHSESA for (sender ); Sun, 11 Dec 2005 19:13:47 -0800 (PST) Received: (from jbker@juno.com) by webmail52.nyc.untd.com (jqueuemail) id LBY6DP88; Sun, 11 Dec 2005 19:13:15 PST Received: from [63.21.161.198] by webmail52.nyc.untd.com with HTTP: Mon, 12 Dec 2005 03:12:40 GMT X-Originating-IP: [63.21.161.198] Mime-Version: 1.0 From: "jbker@juno.com" Date: Mon, 12 Dec 2005 03:12:40 GMT To: flyrotary@lancaironline.net Subject: Re: [FlyRotary] "P" factor? Re: Static Engine RPM X-Mailer: Webmail Version 4.0 Content-Type: multipart/alternative;boundary="--__JWM__J41c6.167eS.2781M" Message-Id: <20051211.191315.4403.91871@webmail52.nyc.untd.com> X-ContentStamp: 24:12:4138576375 X-MAIL-INFO:3ef0bdc0e91549e9750d15692121d405844465c4fde4b1e46090804d6529012074bd908d2975d9d9046101e975e0bde9b120a5dd24a499d5a4d1d199d0f4f461394081b400ed9530c554b03db59d8d91708514e1c1a1391d50ad74 X-UNTD-OriginStamp: Y+Mfppm2QyGfnY/dq+iW1bmAvmUxZtEGGbpN3hRlVsTSLUNqrGH/rA== X-UNTD-Peer-Info: 10.141.27.192|webmail52.nyc.untd.com|webmail52.nyc.untd.com|jbker@juno.com ----__JWM__J41c6.167eS.2781M Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Content-Type: text/plain
Ed, Charlie England is going to get us for posting new at top, but = seems like this post is going that direction so I didn't reverse the fli= ght pattern
 
I think you are correct on both counts that P factor is actually th= e torque generated when the prop runs a non-zero angle of attack and wha= t you are feeling may be the swirl effect on the flying surfaces. You ha= ve demo'd the swirl effect from a plane taking off in front of you (reme= mbering your  harry T/O behind Finn there)But I do think that = when the thrust line does not line up with the CG of the airplane there = is also a steering effect right or left depending on the angle of the en= gine mount and yours aggrevates the swirling force.
 
Bernie, no prop to fly with til after Christmas
 
Hi Georges,
 
The "P" direction  factor only changed when I changed from the= 2.17 to the 2.85 (with the opposite propeller rotation) .  The sho= rtening of the prop slight reduced the "P" factor but did not change its= direction.
 
One thing I think I should mention.  I used to think the force= was caused by the "P" factor, but after reading an article about the ef= fects of Torque, "P" factor and Airstream whirl, I came away with a diff= erent understanding.  Apparently "P" factor is a factor primarily w= ith tail draggers as it is caused by the effect of the  relative wi= nd and the prop blades  not being perpendicular to the relative win= d (until the tail comes up).  With a nose gear, the blades are perp= endicular (at least until lift off) and therefore the "P" factor is mini= mal.
 
Apparently the real cause of the rather powerful force that wants t= o push the nose to the left or right is the swirling air caused by = the spinning prop.  Think of a cork screw.   With my prop= now spinning CCW (from pilot's perspective) the corkscrew of air is swi= rling CCW as well.  It appears the distance from prop to vertical s= tabilizer is such that the air corkscrews around so that more of it hits= the left side of the fuselage and vertical stab than the right.  T= his air forces the tail toward the right and the nose to the left, there= by requiring right rudder to counteract the force.
 
Sounded reasonable to me.  Not to say there is not torque or "= P" factor but given the magnitude of the turning force I would say the a= ir swirl probably is the major factor.
 
Ed A
 
 
 
Ed A
----- Original Message -----
Sent: Sunday, December 11, 2005 8= :53 PM
Subject: [FlyRotary] Re: Static E= ngine RPM

Hi! Ed
I guess I missed something, how can the P-factor be in the"opposite= " direction after shortening the prop 2"?
Georges B. 
 
-------Original Message-------
 
From: Ed Anderson
Date: 12/10/05 14= :54:00
Subject: [FlyRota= ry] Re: Static Engine RPM
 
 Hi Bernie,
 
Good point, Yes, you are correct the engine moun= t is still the same.  However, since it only causes 1/2 ball deflec= tion in cruise, I not certain that the mount is that far offset in the w= rong direction.  Guess I should add a few washers and find out - ju= st kidding.  One of my numerous projects is to fabricate some new e= ngine mounting brackets (keeping the same mounting frame) with the offse= t to the opposite side. 
 
Besides, its really the increased ROC that reall= y tells the story.  I consistently get over 1500 fpm and even get u= p into the 1700 fpm range on cold days lightly loaded.  Previously = it was in the 1000-1200 fpm range.
 
Ok on the prop, Bernie. 
 
I'm planning at this time to fly out to Bill Esl= ick flyin in Feb weather permitting - make a nice long flight for your 9= .
 
Ed A
 
 
=
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Hi Ed,
 
Don't forget to add that the P-factor is now in the opposite direct= ion and I believe you did not change angle of engine mount to offset thi= s. I'm not questioning that you get more thrust with this set up, j= ust questioning if your criteria of lack of rudder is a good indica= tor.
 
Took your prop and the sensenich to plant city and left both with t= hem. Will probably be able to pick them up on the way home from Memphis = after Christmas.
 
Cheers and Merry Christmas in NC,
Bernie
 

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