X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.103] (HELO ms-smtp-04-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.3) with ESMTP id 871897 for flyrotary@lancaironline.net; Sun, 11 Dec 2005 21:15:37 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.103; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-025-165.carolina.res.rr.com [24.74.25.165]) by ms-smtp-04-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id jBC2En1u004130 for ; Sun, 11 Dec 2005 21:14:49 -0500 (EST) Message-ID: <001b01c5fec1$d9a5c470$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: "P" factor? Re: Static Engine RPM Date: Sun, 11 Dec 2005 21:14:57 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0018_01C5FE97.F085E230" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0018_01C5FE97.F085E230 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Georges,=20 The "P" direction factor only changed when I changed from the 2.17 to = the 2.85 (with the opposite propeller rotation) . The shortening 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 effects = of Torque, "P" factor and Airstream whirl, I came away with a different = understanding. Apparently "P" factor is a factor primarily with tail = draggers as it is caused by the effect of the relative wind and the = prop blades not being perpendicular to the relative wind (until the = tail comes up). With a nose gear, the blades are perpendicular (at = least until lift off) and therefore the "P" factor is minimal. Apparently the real cause of the rather powerful force that wants to = 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 swirling CCW as well. = It appears the distance from prop to vertical stabilizer 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. This air forces the tail = toward the right and the nose to the left, thereby 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 air swirl = probably is the major factor. Ed A Ed A ----- Original Message -----=20 From: Echo Lake Fishing Resort (Georges Boucher)=20 To: Rotary motors in aircraft=20 Sent: Sunday, December 11, 2005 8:53 PM Subject: [FlyRotary] Re: Static Engine 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.=20 -------Original Message------- From: Ed Anderson Date: 12/10/05 14:54:00 To: Rotary motors in aircraft Subject: [FlyRotary] Re: Static Engine RPM Hi Bernie, Good point, Yes, you are correct the engine mount is still the = same. However, since it only causes 1/2 ball deflection in cruise, I = not certain that the mount is that far offset in the wrong direction. = Guess I should add a few washers and find out - just kidding. One of my = numerous projects is to fabricate some new engine mounting brackets = (keeping the same mounting frame) with the offset to the opposite side. = Besides, its really the increased ROC that really tells the = story. I consistently get over 1500 fpm and even get up into the 1700 = fpm range on cold days lightly loaded. Previously it was in the = 1000-1200 fpm range. Ok on the prop, Bernie. =20 I'm planning at this time to fly out to Bill Eslick flyin in Feb = weather permitting - make a nice long flight for your 9. Ed A = =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Hi Ed, Don't forget to add that the P-factor is now in the opposite = direction and I believe you did not change angle of engine mount to = offset this. I'm not questioning that you get more thrust with this set = up, just questioning if your criteria of lack of rudder is a good = indicator. Took your prop and the sensenich to plant city and left both = with them. Will probably be able to pick them up on the way home from = Memphis after Christmas. Cheers and Merry Christmas in NC, Bernie =20 =20 =20 ------=_NextPart_000_0018_01C5FE97.F085E230 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Georges,
 
The "P" direction  factor only changed when I changed from the = 2.17 to=20 the 2.85 (with the opposite propeller rotation) .  The shortening = of the=20 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=20 caused by the "P" factor, but after reading an article about the effects = of=20 Torque, "P" factor and Airstream whirl, I came away with a different=20 understanding.  Apparently "P" factor is a factor primarily with = tail=20 draggers as it is caused by the effect of the  relative wind and = the prop=20 blades  not being perpendicular to the relative wind (until the = tail comes=20 up).  With a nose gear, the blades are perpendicular (at least = until lift=20 off) and therefore the "P" factor is minimal.
 
Apparently the real cause of the rather powerful force that wants = to push=20 the nose to the left or right is the swirling air caused by the = spinning=20 prop.  Think of a cork screw.   With my prop now spinning = CCW=20 (from pilot's perspective) the corkscrew of air is swirling CCW as = well. =20 It appears the distance from prop to vertical stabilizer is such that = the air=20 corkscrews around so that more of it hits the left side of the fuselage = and=20 vertical stab than the right.  This air forces the tail toward the = right=20 and the nose to the left, thereby requiring right rudder to counteract = the=20 force.
 
Sounded reasonable to me.  Not to say there is not torque or = "P"=20 factor but given the magnitude of the turning force I would say the air = swirl=20 probably is the major factor.
 
Ed A
 
 
 
Ed A
----- Original Message -----
From:=20 Echo=20 Lake Fishing Resort (Georges Boucher)
Sent: Sunday, December 11, 2005 = 8:53=20 PM
Subject: [FlyRotary] Re: Static = Engine=20 RPM

Hi! Ed
I guess I missed something, how can the P-factor be in=20 the"opposite" direction after shortening the prop 2"?
Georges B. 
 
-------Original=20 Message-------
 
From: Ed Anderson
Date: = 12/10/05=20 14:54:00
To: Rotary motors in=20 aircraft
Subject: = [FlyRotary]=20 Re: Static Engine RPM
 
 Hi Bernie,
 
Good point, Yes, you are correct the = engine mount=20 is still the same.  However, since it only causes 1/2 ball=20 deflection in cruise, I not certain that the mount is that far = offset in=20 the wrong direction.  Guess I should add a few washers and = find out=20 - just kidding.  One of my numerous projects is to = fabricate some=20 new engine mounting brackets (keeping the same mounting frame) = with the=20 offset to the opposite side. 
 
Besides, its really the increased ROC = that really=20 tells the story.  I consistently get over 1500 fpm and even = get up=20 into the 1700 fpm range on cold days lightly loaded.  = Previously it=20 was in the 1000-1200 fpm range.
 
Ok on the prop, Bernie.  =
 
I'm planning at this time to fly out to = Bill=20 Eslick flyin in Feb weather permitting - make a nice long flight = for=20 your 9.
 
Ed A
 
 
=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Hi Ed,
 
Don't forget to add that the P-factor is now in the = opposite=20 direction and I believe you did not change angle of engine mount = to=20 offset this. I'm not questioning that you get more thrust with = this set=20 up, just questioning if your criteria of lack of rudder = is a=20 good indicator.
 
Took your prop and the sensenich to plant city and left = both with=20 them. Will probably be able to pick them up on the way home from = Memphis=20 after Christmas.
 
Cheers and Merry Christmas in NC,
Bernie
 
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