X-Virus-Scanned: clean according to Sophos on Logan.com From: "James Osborn" Received: from mail-oa0-f51.google.com ([209.85.219.51] verified) by logan.com (CommuniGate Pro SMTP 6.0.9e) with ESMTPS id 6997225 for flyrotary@lancaironline.net; Thu, 24 Jul 2014 13:11:28 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.219.51; envelope-from=rxcited@gmail.com Received: by mail-oa0-f51.google.com with SMTP id o6so4120085oag.10 for ; Thu, 24 Jul 2014 10:10:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=mAjfenemzutiDgcpSrOMZpukWaadwdmd4v1I95ipFO8=; b=a2jkEAgIdqFFrKfCTBqn3ogx7uUFVkrouiZWyZOdkn4vIa9p9CygTAafOhwODS54Bv Cjtytrq1N9Ovo/3VblQA669PAf+6dgAG+EkLSbR8lSQ0JNJIm+kgxvhKsqKACWrbMOh3 dv6zliojKLlcvzNKGKhgMg5K2MoIWmRa9d9oME4YKaYLeS50OnXRHib6v2lEwTYfldyd ESE+PVsAOj0Phgvd6HF51Mec3xE0/zQgxolwvhHfdJiDwSd92Rp0Cl9rU4lnhKBHeqwR whRNkyVLWKb/AdH2JcxomoEBFwv7rHr07Q2Rrrx95ks2y3xBHAAGMiUnA6hyiF1sFW+K Hqlg== MIME-Version: 1.0 X-Received: by 10.60.140.234 with SMTP id rj10mr15183467oeb.6.1406221377576; Thu, 24 Jul 2014 10:02:57 -0700 (PDT) Received: by 10.202.107.77 with HTTP; Thu, 24 Jul 2014 10:02:57 -0700 (PDT) In-Reply-To: References: Date: Thu, 24 Jul 2014 10:02:57 -0700 Message-ID: Subject: Re: [FlyRotary] Re: Rv7 renises p port To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=047d7b4725eaafa30404fef36d7c --047d7b4725eaafa30404fef36d7c Content-Type: text/plain; charset=UTF-8 Interesting points and very clever of both you and Charlie! So if there is zero or negative slippage, does it mean that the effective pitch used in the calculation is wrong (hard to nail down as Charlie said) or just that the airfoil cross section of the blade is generating thrust at zero slippage? Maybe what I said that slippage cannot be zero (intuitively) would only be true for a symmetrical blade cross section? As you said Tracy it is possible to fly at 0 degree AOA, but this is because it is a non-symmetric wing airfoil cross section, right? Agreed, I miss the e-mail addresses in the headers. For example, which Tracy? You can't get a clue from the headers anymore... On Thu, Jul 24, 2014 at 9:09 AM, Tracy wrote: > 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" > 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 >> -- >> Homepage: http://www.flyrotary.com/ >> >> Archive and UnSub: >> http://mail.lancaironline.net:81/lists/flyrotary/List.html >> >> >> -- >> Homepage: http://www.flyrotary.com/ >> >> Archive and UnSub: >> http://mail.lancaironline.net:81/lists/flyrotary/List.html >> > > > --047d7b4725eaafa30404fef36d7c Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Interesting points and very clever of both you and Charlie= ! =C2=A0So if there is zero or negative slippage, does it mean that the eff= ective pitch used in the calculation is wrong (hard to nail down as Charlie= said) or just that the airfoil cross section of the blade is generating th= rust at zero slippage? =C2=A0Maybe what I said that slippage cannot be zero= (intuitively) would only be true for a symmetrical blade cross section? = =C2=A0As you said Tracy it is possible to fly at 0 degree AOA, but this is = because it is a non-symmetric wing airfoil cross section, right?

Agreed, I miss the e-mail addresses in the headers. =C2=A0Fo= r example, which Tracy? =C2=A0You can't get a clue from the headers any= more...


On Thu, Jul 24, 2014 at 9:09 AM, Tracy <flyrotary@lancair= online.net> wrote:
Charlie is right. =C2= =A0Consider that an airplane flying with the wing at 0 deg. AOA does not fa= ll out of the sky :-)

My average speed in the 2004 Sun 100 race was 217.58 mp= h which includes standing start takeoff and climbout. =C2=A0Prop was a 74 x= 88, RPM was 7250 with a 2.85 : 1 drive. =C2=A0If you calculate that out it= comes to 212 mph with zero 'slippage'. =C2=A0 Draw your own conclu= sions!

Tracy

Sent from my iPad

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

=20 =20 =20 =20
Ice sails, desert sails, and now, even unlimited class sailboats can sail faster than the wind. 'Negativ= e 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 a= n 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. =C2=A0I found a prop slip calculato= r online and for 86 inch pitch, 2.85 gear ratio, 7000 rpm, 180 mph, I get 10% slip. =C2=A0Granted the calculator was for boat propellers, but I don't think it matters as long as the units are correct. =C2=A0There has to be some slip because there would be no thrust otherwise. =C2=A0So what is considered a reasonable or go= od amount of slip? =C2=A0Using Bill's numbers 86 inch pitch, 2.85 = gear ratio, 7000 rpm, 200 mph, I get 0% slip. =C2=A0That can't be ri= ght!


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. =C2=A0= 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
--
Homepage: =C2=A0http://www.flyrotary.com/

Archive and UnSub:
http://mail.lancaironline.net:81/lists/flyrot= ary/List.html


--
Homepage: =C2=A0http://www.flyrotary.com/

Archive and UnSub: =C2=A0 http://mail.lancair= online.net:81/lists/flyrotary/List.html


=20

--047d7b4725eaafa30404fef36d7c--