Return-Path: Received: from sccrmhc13.comcast.net ([204.127.202.64] verified) by logan.com (CommuniGate Pro SMTP 4.2b3) with ESMTP id 85148 for flyrotary@lancaironline.net; Sun, 23 May 2004 00:18:38 -0400 Received: from rv8 (c-24-21-140-241.client.comcast.net[24.21.140.241]) by comcast.net (sccrmhc13) with SMTP id <20040523040259016001157be> (Authid: n3773@comcast.net); Sun, 23 May 2004 04:02:59 +0000 Message-ID: <003001c4407a$d565c1a0$f18c1518@rv8> Reply-To: "kevin lane" From: "kevin lane" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: engine mount geometry Date: Sat, 22 May 2004 21:02:55 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_002D_01C44040.27170080" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 This is a multi-part message in MIME format. ------=_NextPart_000_002D_01C44040.27170080 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Messagemike McGee and I were just talking about my setup, I.e. going = from a left turning mount to a right. he pointed out that this is = exactly what Tracy just did with his -4. we guessed that he didn't = change the engine mount geometry, but perhaps offset the vert stab = instead. perhaps I could mount my engine "best fit" and compensate with = the stab as well. if I attempt to put 1 1/2 degrees in the engine, the = left rear rubber mount is too close to the block. I could possibly = offset that one mount point, or, make it tight, and offset the stab more = than normal. I can't even think about what changes a higher cruise = speed might make(hopefully that will be true, right rusty?) thanks for the measurement, it helps to hear from several sources. = there are always many solutions, despite freed Breese's fixed answer of = "buy a new mount" and "it's way too complicated to explain to you". I would like to hear what you guys say about this geometry. does the = vert stab offset create drag? is one way better than another? will = higher cruise speeds affect the alignment, I know it affects rudder = trim? Kevin Lane Portland, OR e-mail-> n3773@comcast.net web-> http://home.comcast.net/~n3773 (browse w/ internet explorer) ----- Original Message -----=20 From: Russell Duffy=20 To: Rotary motors in aircraft=20 Sent: Saturday, May 22, 2004 4:26 PM Subject: [FlyRotary] Re: engine mount geometry I am fabricating the bed mount plate for my 20B in an rv-8. my = understanding, from Tracy's advice, is to offset the engine about 1 1/2 = degrees to the right if I use his 2.85 drive.=20 Hi Kevin, Sorry I didn't think of this before, but last weekend, I measured the = offset of my friends RV-8 prop, but never did the math to see what it = came out to be. Basically, I put the prop horizontal, and measured from = the tail, to each tip. The difference was 2 inches, on a 74" prop, = which works out to 1.55 degrees right offset. =20 The reason I measured this was to see what his offset was, because he = says he doesn't need any rudder in cruise. My RV-8 also required no = rudder in cruise, and neither of out planes had any offset in the vert = stab. Curiously, the same measurement shows that my RV-3 (-B drive) has = 1.25 degrees of left offset, and I need a buttload of left rudder in = cruise. The only thing I can concluded is that there is right offset = somewhere in the in the tail. I can't tell if the vert stab is offset, = but it might be. There could also just be something crooked that I = can't spot. I didn't build the tail, and fuselage, or I'd know if = offset was put in. =20 Since I'm going to the -C drive later this Summer, I'm more than a = little interested to see how the offset works out. Since there already = seems to be some other right offset force at work, I'll probably try = flying the -C drive with the left offset still in the mount. If I'm = careful, it shouldn't be dangerous, and then I can decide if I need to = remove the current offset. If I have to remove it, I'll shim the mount = a half inch on the left to do it. I'll also reposition the cowl to keep = everything lined up. The prop won't quite be centered, but I defy = anyone to notice. =20 Cheers, Rusty ------=_NextPart_000_002D_01C44040.27170080 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
mike McGee and I were just = talking about=20 my setup, I.e. going from a left turning mount to a right.  he = pointed out=20 that this is exactly what Tracy just did with his -4.  we guessed = that he=20 didn't change the engine mount geometry, but perhaps offset the vert = stab=20 instead.  perhaps I could mount my engine "best fit" and compensate = with=20 the stab as well.  if I attempt to put 1 1/2 degrees in the = engine, =20 the left rear rubber mount is too close to the block.  I could = possibly=20 offset that one mount point, or, make it tight, and offset the stab more = than=20 normal.  I can't even think about what changes a higher cruise = speed might=20 make(hopefully that will be true, right rusty?)
thanks for the measurement, = it helps to=20 hear from several sources.  there are always many solutions, = despite freed=20 Breese's fixed answer of "buy a new mount"  and "it's way too = complicated=20 to explain to you".
I would like to hear what you = guys say=20 about this geometry.  does the vert stab offset create drag?  = is one=20 way better than another?  will higher cruise speeds affect the = alignment, I=20 know it affects rudder trim?
Kevin Lane  Portland, OR
e-mail-> n3773@comcast.net
web-> http://home.comcast.net/~n3773
(browse=20 w/ internet explorer)
----- Original Message -----
From:=20 Russell=20 Duffy
Sent: Saturday, May 22, 2004 = 4:26=20 PM
Subject: [FlyRotary] Re: engine = mount=20 geometry

I am fabricating the bed mount plate for my 20B in = an=20 rv-8.  my understanding, from Tracy's advice, is to offset the = engine=20 about 1 1/2 degrees to the right if I use his 2.85 = drive. 

 
Hi=20 Kevin,
 
Sorry = I didn't think=20 of this before, but last weekend, I measured the offset of my friends = RV-8=20 prop, but never did the math to see what it came out to be.  = Basically, I=20 put the prop horizontal, and measured from the tail, to each = tip.  The=20 difference was 2 inches, on a 74" prop, which works out to 1.55 = degrees right=20 offset. 
 
The = reason I measured=20 this was to see what his offset was, because he says he doesn't need = any=20 rudder in cruise.  My RV-8 also required no rudder in cruise, and = neither=20 of out planes had any offset in the vert stab.  Curiously, the = same=20 measurement shows that my RV-3 (-B drive) has 1.25 degrees of left = offset, and=20 I need a buttload of left rudder in cruise.  The only thing I can = concluded is that there is right offset somewhere in the in the=20 tail.  I can't tell if the vert stab is offset, but it might = be. =20 There could also just be something crooked that I can't = spot.  I=20 didn't build the tail, and fuselage, or I'd know if offset was = put=20 in.  
 
Since = I'm=20 going to the -C drive later this Summer, I'm more than a little=20 interested to see how the offset works out.  Since there = already=20 seems to be some other right offset force at work, I'll probably try = flying=20 the -C drive with the left offset still in the mount.  If = I'm=20 careful, it shouldn't be dangerous, and then I can decide if I=20 need to remove the current offset.  If I have to remove = it,=20 I'll shim the mount a half inch on the left to do it.  I'll also=20 reposition the cowl to keep everything lined up.  The prop = won't=20 quite be centered, but I defy anyone to=20 notice.  
 
Cheers,
Rusty
 



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