X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.3) with ESMTP id 870943 for flyrotary@lancaironline.net; Sat, 10 Dec 2005 17:46:15 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.100; 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-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id jBAMjRWe018816 for ; Sat, 10 Dec 2005 17:45:28 -0500 (EST) Message-ID: <000d01c5fddb$6e7d0780$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Elippse Propeller Date: Sat, 10 Dec 2005 17:45:33 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000A_01C5FDB1.8549EB60" 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_000A_01C5FDB1.8549EB60 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Interesting for certain. =20 I have 88" of pitch which is much more than my original prop which had = 72" turning 5600 rpm using the 2.17. There is no question that my = acceleration on take off and rate of climb is significantly improved = with the slower turning 74x88" prop. The key (I believe - not being a = prop designer) is swinging the longest prop you can which bites a = bigger disk of air. My new prop started out with an 8" larger diameter = (now 6" larger) which I believe made the difference. The older 68x72 = prop would be tearing up the air 6000 (engine rpm) but, it always felt = to me like it was trashing the air, but just wasn't pushing a whole lot = backwards. At 5200 rpm and 2.17 the old prop was turning 2400 rpm. At 6000 and = 2.85 the new prop is only turning 2105 rpm - yet the new prop is clearly = out pulling the old prop. Again I think the key is the length. Part of = the blade may indeed be stalled with 88" of pitch but the outer = unstalled portion I suspect more than makes up for it. Since that = region of the prop is also further out from the disruptive influence of = the cowl, there is probably better efficiency provided your tip is below = 80% sonic (slower turning makes that more likely). Also looking at the power difference at the two different rpms, I = calculate 160 at 5200 and 180HP at 6000, whether that is accurate = absolute power it shows a possible 12.5% increase. The disc area carved = out by the 74" prop is approx 18% more although its speed is approx 13% = less. So I think more area, more HP and more pitch appears to add up in = my case to considerably better low speed performance. The top speed = appears not to have changed, still a shade under 200 MPH around 197MPH = for both props. So, don't have answer except I think the diameter of the disc your prop = carves out of the air has a very significant impact (especially at = lower airspeeds and lower prop rpm). I do recall one prop designer said = for maximum take off performance swing the biggest prop you have = clearance for. =20 Interestingly enough before I had the prop shortened, I was a Tracy = Crooks and was doing a run up to get some exhaust sound readings. It = was a cool morning and the engine was turning around 5800-6000. Tracy = and I (as well as the sound meter) could hear the prop blade stalling = and unstalling (apparently as the blade rotate different orientation = with respect to the cowl and effect the airflow enough to cause it to = stall and that point and then recover). You could hear a distinct "wop! = wop! Wop!" sound as the prop stalled and unstalled.=20 In summary, I believe if you have two props of the same diameter and one = with a much larger pitch then static blade stall may be more of a factor = than if you take advantage of a longer bladed prop, increase its pitch = and slow its speed as we are able to do by changing gear boxes - of = course, not being a propeller designer, I could be all wrong about the = above. just my 0.02 worth Ed ----- Original Message -----=20 From: Kelly Troyer=20 To: Rotary motors in aircraft=20 Sent: Saturday, December 10, 2005 10:57 AM Subject: [FlyRotary] Elippse Propeller Guys, Here is an exchange I just had with Paul Lipps the designer of the = "Elippse" prop blades.........Those of you that have heard about his blades in = "Contact" mag. and "Sportsman Pilot" mag. may find this info of = interest.....FWIW -- Kelly Troyer=20 Dyke Delta/13B/RD1C/EC2=20 -------------- Forwarded Message: --------------=20 From: keltro@att.net (Kelly Troyer)=20 To: "Paul Lipps" Subject: Re: Elippse Propeller=20 Date: Sat, 10 Dec 2005 07:54:00 +0000=20 Paul, Thanks for the info and suggestions......I have e-mailed Grand = Aero for info on your blades with the numbers for my a/c , engine , etc.... Thanks again, -- Kelly Troyer=20 Dyke Delta/13B/RD1C/EC2=20 -------------- Original message from "Paul Lipps"=20 Hi, Kelly! I don't make props, I only design them. I have designed a prop = blade for Grand Aero that will be used in a three-blade, = ground-adjustable hub. It's been designed for the RV-series of planes, = and will easily accomodate 150hp-200hp for cruise speeds in the 170 mph = to 220 mph region. One thing I might caution you about, though. You = mention only turning 2100 rpm because of your gear ratio. Takeoff with = the prop adjusted for that low a cruise rpm would require a fairly high = blade angle. The blades would be stalled over a large portion during the = early stages of the takeoff run, and so would not give much initial = thrust, making for a longer takeoff. If possible, you might consider a = different gear ratio allowing you to set the blades at a lower angle, = giving much better static and takeoff thrust. The three-blade prop on my = Lancair turns 2230rpm static, 2440rpm in a climb at 115mph IAS, and 2800 = rpm at 201 mph cruise at 10,000' dalt. This should give ------=_NextPart_000_000A_01C5FDB1.8549EB60 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Interesting for certain. 
 
I have 88" of pitch which is much more than = my=20 original prop which had  72" turning 5600 rpm using the = 2.17. =20 There is no question that my acceleration on take off and rate of climb = is=20 significantly improved with the slower turning 74x88" prop.  The = key (I=20 believe - not being a prop designer) is  swinging the longest = prop you=20 can which bites a bigger disk of air.  My new prop started out with = an 8"=20 larger diameter (now 6" larger) which I believe made the = difference.  The=20 older 68x72 prop would be tearing up the air 6000 (engine rpm) but, = it always felt to me like it was trashing the air, but just wasn't = pushing=20 a whole lot backwards.
 
At 5200 rpm and 2.17 the old prop was turning = 2400=20 rpm.  At 6000 and 2.85 the new prop is only turning 2105 rpm - yet = the new=20 prop is clearly out pulling the old prop.  Again I think the key is = the=20 length.  Part of the blade may indeed be stalled with 88" of pitch = but the=20 outer unstalled portion I suspect more than makes up for it.  Since = that=20 region of the prop is also further out from the disruptive influence of = the=20 cowl, there is probably better efficiency provided your tip is below 80% = sonic=20 (slower turning makes that more likely).
 
Also looking at the power difference at the two = different=20 rpms, I calculate 160 at 5200 and 180HP at 6000, whether that is  = accurate=20 absolute power it shows a possible 12.5% increase.  The = disc area=20 carved out by the 74" prop is approx 18% more although its speed is = approx 13%=20 less.  So I think more area, more HP and more pitch appears to = add up=20 in my case to considerably better low speed performance.  The top = speed=20 appears not to have changed, still a shade under 200 MPH around 197MPH = for both=20 props.
 
 
So, don't have answer except I think the = diameter of the=20 disc your prop carves out  of the air has a very significant impact = (especially at lower airspeeds and lower prop rpm).  I do recall = one prop=20 designer said for maximum take off performance swing the biggest prop = you have=20 clearance for. 
 
Interestingly enough before I had the prop = shortened, I=20 was a Tracy Crooks and was doing a run up to get some exhaust sound=20 readings.  It was a cool morning and the engine was turning around=20 5800-6000.  Tracy and I (as well as the sound meter) could hear the = prop=20 blade stalling and unstalling (apparently as the blade rotate different=20 orientation with respect to the cowl and effect the airflow enough to = cause it=20 to stall and that point and then recover).  You could hear a = distinct "wop!=20 wop! Wop!" sound as the  prop stalled and unstalled.
 
In summary, I believe if you have two props of = the same=20 diameter and one with a much larger pitch then static blade stall may be = more of=20 a factor than if you take advantage of a longer bladed prop, increase = its pitch=20 and slow its speed as we are able to do by changing gear boxes - of = course, not=20 being a propeller designer, I could be all wrong about the = above.
 
 
just my 0.02 worth
 
Ed
----- Original Message -----
From:=20 Kelly = Troyer
Sent: Saturday, December 10, = 2005 10:57=20 AM
Subject: [FlyRotary] Elippse=20 Propeller

Guys,
   Here is an exchange I just had with Paul Lipps the = designer=20 of the "Elippse"
prop blades.........Those of you that have heard about his blades = in=20 "Contact"
mag. and "Sportsman Pilot" mag. may find this info of=20 interest.....FWIW
--
Kelly Troyer
Dyke=20 Delta/13B/RD1C/EC2




--------------=20 Forwarded Message: --------------
From: keltro@att.net (Kelly = Troyer)=20
To: "Paul Lipps" Subject: Re: Elippse Propeller
Date: Sat, = 10 Dec=20 2005 07:54:00 +0000

 Paul,
  Thanks for the info and suggestions......I have e-mailed = Grand=20 Aero for info on
your blades with the numbers for my a/c , engine , = etc....
 
Thanks again,
--
Kelly Troyer
Dyke=20 Delta/13B/RD1C/EC2




--------------=20 Original message from "Paul Lipps"

Hi, Kelly!
    I don't make props, I = only design=20 them. I have designed a prop blade for Grand Aero that will be = used in a=20 three-blade, ground-adjustable hub. It's been designed for the = RV-series=20 of planes, and will easily accomodate 150hp-200hp for cruise = speeds in the=20 170 mph to 220 mph region. One thing I might caution you about, = though.=20 You mention only turning 2100 rpm because of your gear ratio. = Takeoff with=20 the prop adjusted for that low a cruise rpm would require a fairly = high=20 blade angle. The blades would be stalled over a large portion = during the=20 early stages of the takeoff run, and so would not give much = initial=20 thrust, making for a longer takeoff. If possible, you might = consider a=20 different gear ratio allowing you to set the blades at a lower = angle,=20 giving much better static and takeoff thrust. The three-blade prop = on my=20 Lancair turns 2230rpm static, 2440rpm in a climb at 115mph IAS, = and 2800=20 rpm at 201 mph cruise at 10,000' dalt. This should give
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