X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 2 [X] Return-Path: Received: from ms-smtp-01.southeast.rr.com ([24.25.9.100] verified) by logan.com (CommuniGate Pro SMTP 5.1.8) with ESMTP id 2030592 for flyrotary@lancaironline.net; Mon, 07 May 2007 14:19:39 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.100; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-103-061.carolina.res.rr.com [24.74.103.61]) by ms-smtp-01.southeast.rr.com (8.13.6/8.13.6) with SMTP id l47IIS6L010219 for ; Mon, 7 May 2007 14:18:28 -0400 (EDT) Message-ID: <000901c790d4$50791ed0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Pinched Duct Date: Mon, 7 May 2007 14:19:55 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0006_01C790B2.C8F2C400" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3028 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0006_01C790B2.C8F2C400 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Bill, Difficult to answer. I record my airspeed, temp and altitude when I fly = and try to exercise some care in collecting that data. But, a few = degrees off the temperature, a few feet off the altitude, etc. could = easily swamp any real speed improvement. It appears that in my flights = previous to the pinched ducts I could get really close to 200MPH TAS, = but never quite get there - like 195-197 mph TAS. I am now confident I = have repeatedly hit and slightly exceed 200 MPH TAS - but, what to = attribute the increase to is the question. =20 Depending on the amount of external diffusion going on the virtual inlet = area could be larger than even my "Lip" area opening - so again, just = hard to say. It could well be as Al indicated - that my "pinched" duct = really does not play any role in the cooling improvement - just a = fortuitous combination of other factors. But, I do have what I believe = is a logical rationale for that approach - whether it holds water = remains to be seen. My cooling system now seems well (if not optimized) matched to my = current installation. Full power take offs on hot days see my cooling = temps elevate to 200F for oil and 210-220F for coolant. Once I hit 120 = MPH IAS the cooling system catches up and starts to eliminate the = cooling deficit. =20 At my normal retired-man cruise of 7- 8 gph, my coolant and oil range = from 155-170F depending on OAT. When I push it to my max fuel = flow/power 10.5-12.5 gph at altitude the temperatures of both increase = until they are in the 190-195F range. This gives me my maximum true = airspeed. So it appears my cooling capacity is about right where I = need it. Certainly a surplus at low power cruise, but just adequate on = take/off climbout on hot days and adequate for full boogie flight. I really don't know how much drag (if any) I have eliminated, but I am = convinced that it is less than if I had more of the core exposed to high = velocity airflow. =20 Sorry, I can't be more definitive about it - I would like to know as = well, but only so much time to get all the wonderful projects on my list = done. Perhaps someone with the inclination and time will someday put = this idea in a wind tunnel and tell us {:>) Ed ----- Original Message -----=20 From: wrjjrs@aol.com=20 To: Rotary motors in aircraft=20 Sent: Monday, May 07, 2007 1:27 PM Subject: [FlyRotary] Re: Pinched Duct Ed, An interesting factor here is that when considering duct inlet = diameter/opening size is usually calculated from the high point of the = opening. Provided the opening is smoothly configured. Since your pinched = duct uses a smooth turn from the high point on the cowl, most of the = time you would calculate the area as the highpoint on the opening for = the purpose of calculating drag. I was talking to Peter Garrison about = this when he visited our EAA chapter. I know the cooling improved, Was = there any increase in speed? Assuming that same throttle position of = course. Bill Jepson=20 =20 -----Original Message----- From: eanderson@carolina.rr.com To: flyrotary@lancaironline.net Sent: Mon, 7 May 2007 5:08 AM Subject: [FlyRotary] Re: Pinched Duct ------=_NextPart_000_0006_01C790B2.C8F2C400 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Bill,
 
Difficult to answer.  I record my = airspeed,=20 temp and altitude when I fly and try to exercise some care in collecting = that=20 data.  But, a few degrees off the temperature,  a few feet off = the=20 altitude, etc. could easily swamp any real speed improvement.  It = appears=20 that in my flights previous to the pinched ducts I could get really = close to=20 200MPH TAS, but never quite get there - like 195-197 mph TAS.  I am = now=20 confident I have repeatedly hit and slightly exceed 200 MPH TAS - but, = what to=20 attribute the increase to  is the question. 
 
Depending on the amount of external = diffusion going=20 on the virtual inlet area could be larger than even my "Lip" area = opening - so=20 again, just hard to say.  It could well be as Al indicated - that = my=20 "pinched" duct really does not play any role in the cooling improvement = - just a=20 fortuitous combination of other factors.  But, I do have what I = believe=20 is a logical rationale for that approach - whether it holds = water=20 remains to be seen.
 
My cooling system now seems well (if = not optimized)=20 matched to my current installation.  Full power take offs on = hot days=20 see my cooling temps elevate to 200F for oil and 210-220F for = coolant. =20 Once I hit 120 MPH IAS the cooling system catches up and starts to = eliminate the=20 cooling deficit. 
 
At my normal retired-man cruise of 7- 8 = gph, my=20 coolant and oil range from 155-170F depending on OAT.  When I push = it to my=20 max fuel flow/power 10.5-12.5 gph at  altitude  the = temperatures=20 of both increase until they are in the 190-195F range.  This gives = me my=20 maximum true airspeed.  So it appears my cooling capacity is = about =20 right where I need it.  Certainly a surplus at low power cruise, = but just=20 adequate on take/off climbout on hot days and adequate for full boogie=20 flight.
 
I really don't know how much drag (if = any) I have=20 eliminated, but I am convinced that it is less than if I had more of the = core=20 exposed to high velocity airflow. 
 
Sorry, I can't be more definitive about = it - I=20 would like to know as well, but only so much time to get all the = wonderful=20 projects on my list done.  Perhaps someone with the inclination and = time=20 will someday put this idea in a wind tunnel and tell us = {:>)
 
Ed
 
 
 
 
----- Original Message -----
From:=20 wrjjrs@aol.com
Sent: Monday, May 07, 2007 1:27 = PM
Subject: [FlyRotary] Re: = Pinched=20 Duct

Ed,
 An interesting factor here is that when considering duct = inlet=20 diameter/opening size is usually calculated from the high point of the = opening. Provided the opening is smoothly configured. Since your = pinched duct=20 uses a smooth turn from the high point on the cowl, most of the time = you would=20 calculate the area as the highpoint on the opening for the purpose of=20 calculating drag. I was talking to Peter Garrison about this when he = visited=20 our EAA chapter. I know the cooling improved, Was there any increase = in speed?=20 Assuming that same throttle position of course.
Bill Jepson 
 
 
-----Original Message-----
From:=20 eanderson@carolina.rr.com
To: flyrotary@lancaironline.net
Sent: = Mon, 7=20 May 2007 5:08 AM
Subject: [FlyRotary] Re: Pinched Duct

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