X-Virus-Scanned: clean according to Sophos on Logan.com From: "Tracy" Received: from mail-yk0-f176.google.com ([209.85.160.176] verified) by logan.com (CommuniGate Pro SMTP 6.0.9e) with ESMTPS id 6997091 for flyrotary@lancaironline.net; Thu, 24 Jul 2014 12:09:52 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.160.176; envelope-from=rwstracy@gmail.com Received: by mail-yk0-f176.google.com with SMTP id 19so1910399ykq.35 for ; Thu, 24 Jul 2014 09:09:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=subject:references:from:content-type:in-reply-to:message-id:date:to :content-transfer-encoding:mime-version; bh=ZUIhEgt3Ug0Mmn0Jsvuw+RLcbaQKb1ZtR40ZhiEMmBQ=; b=xzoBTI06oq6tkOxPVUhh+w1pL7RMSaibUT87MJjsRsoA+POiTHGrnPZL2MBP8XXI20 WD2iJ98aC6XAKwrMfDyYO1+n/vnFVwNxI9Ipaqo7NU/pqPZa6RyissOrh2KCcBiapMlE 7noTm3SfyyAMGEl+M8lxfQpU2HH8o2YzNvTq24sdpw55Q2RXqMBrBGYWiW7fwG0s1BtD AcZyM07q+yEbqaQs9oKyDm5XZp1wHVEsCJZGQTOMmGv/J/h3PLBBx2bXByjSdKu8IJAo xmGvb53ZUKXjE7tcRpdYol9+37p56sisum72rWUzgN92VxH3ZOZMcOrAV10QFLVFXEGD 6HbA== X-Received: by 10.236.54.10 with SMTP id h10mr14136091yhc.24.1406218156190; Thu, 24 Jul 2014 09:09:16 -0700 (PDT) Return-Path: Received: from [192.168.1.4] (62.sub-70-209-18.myvzw.com. [70.209.18.62]) by mx.google.com with ESMTPSA id h94sm14897339yhq.35.2014.07.24.09.09.13 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 24 Jul 2014 09:09:14 -0700 (PDT) Subject: Re: [FlyRotary] Re: Rv7 renises p port References: Content-Type: multipart/alternative; boundary=Apple-Mail-9D24AE3D-9FDE-47D0-84C5-35864E3CB7EA X-Mailer: iPad Mail (11D257) In-Reply-To: Message-Id: Date: Thu, 24 Jul 2014 12:09:11 -0400 To: Rotary motors in aircraft Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (1.0) --Apple-Mail-9D24AE3D-9FDE-47D0-84C5-35864E3CB7EA Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Charlie is right. Consider that an airplane flying with the wing at 0 deg. A= OA does not fall out of the sky :-) My average speed in the 2004 Sun 100 race was 217.58 mph which includes stan= ding start takeoff and climbout. Prop was a 74 x 88, RPM was 7250 with a 2.= 85 : 1 drive. If you calculate that out it comes to 212 mph with zero 'slip= page'. Draw your own conclusions! Tracy Sent from my iPad > On Jul 23, 2014, at 22:59, "Charlie England" = wrote: >=20 > Ice sails, desert sails, and now, even unlimited class sailboats can sail f= aster than the wind. 'Negative slippage'. :-) >=20 > A more significant point might be that pitch numbers are virtually meaning= less, unless you're comparing two props from the same prop maker with the sa= me blade plan form. Even then, it just tells you which has a finer pitch tha= n the other. >=20 > Variables can be: whether the pitch is measured on the back side of the bl= ade or through the chord line, where along the diameter the pitch angle is m= easured (due to blade twist), and no doubt others I'm not smart enough to th= ink of at the moment.=20 >=20 > Bottom line is that unless there's an identical airframe flying an identic= al prop, the pitch number isn't a reliable indicator of speed. >=20 > FWIW, >=20 > Charlie >=20 >=20 >=20 >> On 7/23/2014 7:45 PM, James Osborn wrote: >> I don't know jack about slippage, but I think it is the percentage differ= ence between actual distance traveled and theoretical distance traveled if y= our propeller corkscrewed through the air with no thrust. I found a prop sl= ip calculator online and for 86 inch pitch, 2.85 gear ratio, 7000 rpm, 180 m= ph, I get 10% slip. Granted the calculator was for boat propellers, but I d= on't think it matters as long as the units are correct. There has to be som= e slip because there would be no thrust otherwise. So what is considered a r= easonable or good amount of slip? Using Bill's numbers 86 inch pitch, 2.85 g= ear ratio, 7000 rpm, 200 mph, I get 0% slip. That can't be right! >>=20 >>=20 >>> On Fri, Jul 4, 2014 at 7:19 AM, Bill Bradburry wrote: >>> Christian, >>>=20 >>> It seems that you have a lot of prop slippage at cruise. I think that a= t >>> that prop rpm you should be getting 200mph if you had no slippage. >>>=20 >>> Bill >>>=20 >>> -----Original Message----- >>> From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] >>> Sent: Thursday, July 03, 2014 4:01 PM >>> To: Rotary motors in aircraft >>> Subject: [FlyRotary] Rv7 renises p port >>>=20 >>> Well hi all >>> Just thought I'd throw out there the mods I,ve done to the renises in an= >>> rv7'. >>> Well the p ported engine is now back in the plane and running well, over= the >>> standard short manifold that was originally in the plane I have gained >>> around 400 static rpm, same prop and gearbox combo, 2.85 ratio, this equ= ates >>> to allot more hp at takeoff, just shy of 2300 prop rpm, I'm running a pr= ince >>> p tip prop at 68" x 86" pitch, >>> At 8000 ft it is turning 7000 at 180 mph tas which is an improvement of 2= 5 >>> mph on previous tests, . So next plan is bigger prop and less pitch to l= et >>> it rev to 7500 in strait and level. >>>=20 >>> Cheers >>> Christian >>> Rv7 renises Aus >>>=20 >>>=20 >>> Sent from my iPad >>> -- >>> Homepage: http://www.flyrotary.com/ >>> Archive and UnSub: >>> http://mail.lancaironline.net:81/lists/flyrotary/List.html >>>=20 >>>=20 >>> -- >>> Homepage: http://www.flyrotary.com/ >>> Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/Li= st.html >=20 --Apple-Mail-9D24AE3D-9FDE-47D0-84C5-35864E3CB7EA Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 7bit
Charlie is right.  Consider that an airplane flying with the wing at 0 deg. AOA does not fall out of the sky :-)

My average speed in the 2004 Sun 100 race was 217.58 mph which includes standing start takeoff and climbout.  Prop was a 74 x 88, RPM was 7250 with a 2.85 : 1 drive.  If you calculate that out it comes to 212 mph with zero 'slippage'.   Draw your own conclusions!

Tracy

Sent from my iPad

On Jul 23, 2014, at 22:59, "Charlie England" <flyrotary@lancaironline.net> wrote:

Ice sails, desert sails, and now, even unlimited class sailboats can sail faster than the wind. 'Negative slippage'. :-)

A more significant point might be that pitch numbers are virtually meaningless, unless you're comparing two props from the same prop maker with the same blade plan form. Even then, it just tells you which has a finer pitch than the other.

Variables can be: whether the pitch is measured on the back side of the blade or through the chord line, where along the diameter the pitch angle is measured (due to blade twist), and no doubt others I'm not smart enough to think of at the moment.

Bottom line is that unless there's an identical airframe flying an identical prop, the pitch number isn't a reliable indicator of speed.

FWIW,

Charlie



On 7/23/2014 7:45 PM, James Osborn wrote:
I don't know jack about slippage, but I think it is the percentage difference between actual distance traveled and theoretical distance traveled if your propeller corkscrewed through the air with no thrust.  I found a prop slip calculator online and for 86 inch pitch, 2.85 gear ratio, 7000 rpm, 180 mph, I get 10% slip.  Granted the calculator was for boat propellers, but I don't think it matters as long as the units are correct.  There has to be some slip because there would be no thrust otherwise.  So what is considered a reasonable or good amount of slip?  Using Bill's numbers 86 inch pitch, 2.85 gear ratio, 7000 rpm, 200 mph, I get 0% slip.  That can't be right!


On Fri, Jul 4, 2014 at 7:19 AM, Bill Bradburry <flyrotary@lancaironline.net> wrote:
Christian,

It seems that you have a lot of prop slippage at cruise.  I think that at
that prop rpm you should be getting 200mph if you had no slippage.

Bill

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Thursday, July 03, 2014 4:01 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Rv7 renises p port

Well hi all
Just thought I'd throw out there the mods I,ve done to the renises in an
rv7'.
Well the p ported engine is now back in the plane and running well, over the
standard short manifold that was originally in the plane I have gained
around 400 static rpm, same prop and gearbox combo, 2.85 ratio, this equates
to allot more hp at takeoff, just shy of 2300 prop rpm, I'm running a prince
p tip prop at 68" x 86" pitch,
At 8000 ft it is turning 7000 at 180 mph tas which is an improvement of 25
mph on previous tests, . So next plan is bigger prop and less pitch to let
it rev to 7500 in strait and level.

Cheers
Christian
Rv7 renises Aus


Sent from my iPad
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