X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-bw0-f206.google.com ([209.85.218.206] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3819579 for flyrotary@lancaironline.net; Thu, 20 Aug 2009 14:21:00 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.218.206; envelope-from=msteitle@gmail.com Received: by bwz2 with SMTP id 2so69984bwz.19 for ; Thu, 20 Aug 2009 11:20:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=4FpVXwRky76P/KbcwGIFNIlGOf8QSzV6u/Q8mmlCWiE=; b=mPKIe5xnJEHq7UINd0nT5H+hctLgfcRWyWzPdhCFIYKsZvCrbdOFwJ/x6IwSRJExFB Rzq8yW1lFKteCAOdJImVd6a8P9F+zTYK4JQjEC7ZPtoU2+LL6WmBpuOdjkEqEoYm3Ss4 EVY5Zg5Ho1sCmzy0CaAgQjzLfqe0rsTjLsT1o= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=Xe1LZ85d9XDyRyZ5icr1qLDtfhsBOObIxslNfpIxbQ2zEQk8u9BmRQ35661EPWiXY/ Eal/zEEtLoQnmMqaRJC/lbXujFS8yW2cJIHInICTpa1Pk1xd8RRijlCE8zj1NePXvZM8 ymSE8ZfGHR9S56ml8QJ+l9FJbE6IIN4tRwBdM= MIME-Version: 1.0 Received: by 10.204.162.130 with SMTP id v2mr89864bkx.70.1250792421584; Thu, 20 Aug 2009 11:20:21 -0700 (PDT) In-Reply-To: References: Date: Thu, 20 Aug 2009 13:20:21 -0500 Message-ID: <5cf132c0908201120u6945f928q652388cc4028b5f2@mail.gmail.com> Subject: Re: [FlyRotary] Cowl Flap From: Mark Steitle To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=00032555967ef9f1d4047196cd46 --00032555967ef9f1d4047196cd46 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Ed, I installed a cowl flap on my Lancair. In an attempt to improve the hot weather cooling, I enlarged the exit area by cutting a rectangular hole of approx. 4 x 15 and added a 1-1/2" lip to the bottom leading edge to help coax the air out of the cowl. I later installed a servo-actuated cowl flap so I could open and close it as necessary. I chose to go this route rather than adding a thermostat to the cooling system. I leave it open during tax= i and climb, and close it once in cruise with temps stabilized. Works as advertised. Mark S. On Thu, Aug 20, 2009 at 12:16 PM, Ed Anderson wr= ote: > Interestingly, if I correctly interpret the extract on exit area I took > from a study on aircraft liquid engine cooling, it would seem to imply th= at > a =93free floating=94 cowl flap would seek its own/best position with reg= ard to > minimizing cooling drag. The flap would open more if the air pressure on > the cowl side exceeds the free air pressure at its exit into the airstrea= m > and would be closed by the airstream until the pressure on both sides of = the > cowl flap equalized. > > > > At least that is what it appears to say to me. However, minimum coolin= g > drag may not/will not always be conducive to maximum cooling. In some > cases, like in climb, you may not mind more drag if your cooling is bette= r > by opening the flap more than optimum for minimum drag. > > > > So I imagine, you would still want a control level/servo motor to control > the extension. There is more pressure on the flap than you might think. = I > think it was Bill Eslick that tried a cowl flap and believe he eventually > abandoned it =96 but, not certain if he did or exactly why (I think I kne= w at > one time {:>) =96 Bill, speak up! > > > > Ed > > > > Ed Anderson > > Rv-6A N494BW Rotary Powered > > Matthews, NC > > eanderson@carolina.rr.com > > http://www.andersonee.com > > http://www.dmack.net/mazda/index.html > > http://www.flyrotary.com/ > > http://members.cox.net/rogersda/rotary/configs.htm#N494BW > > http://www.rotaryaviation.com/Rotorhead%20Truth.htm > ------------------------------ > > *From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] *O= n > Behalf Of *Tracy Crook > *Sent:* Thursday, August 20, 2009 10:14 AM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] Re: Cowl Flap/Exit was [FlyRotary] Re: back in the > air > > > > Count on Ed to supply the technical background :-) That's another good > rule of thumb on the maximum inlet area too (.3 * core area). More > doesn't do you any good. > > Main point is, You don't have to be a rocket scientist to make this stuff > work if you follow a few basic rules of thumb. (The right ones that is, > there are a lot of bogus ones floating around as well :>) > > Tracy > > On Thu, Aug 20, 2009 at 9:49 AM, Ed Anderson > wrote: > > Past a specific inlet area to core frontal area (this ratio in the vicini= ty > of 0.30, no additional flow is achieved by further opening of inlets =96 = the > exit area becomes the controlling factor. As Tracy stated, probably bette= r > to look to a cowl flap than mess with your inlets if you are getting good > cooling with your present inlets. > > > > Here is an extract out of a study of cooling of small aircraft engines th= at > points out the two functions of your exit area. > > > > *Exits* > > * * > > The exit has two basic functions: to regulate the cooling air > > flow and to exhaust the cooling flow into the external flow so > > as to result in minimal drag penalty. To adequately perform > > the regulation, the exit must act as both a throttle and a pump. > > Throttling is necessary in cruising flight to minimize the cooling > > drag by reducing the cooling flow to that sufficient to meet > > cooling requirements. > > > > In ground operation and in climbing > > flight, the exit must act as a pump to induce sufficient cooling > > flow through the system. Both of these functions can be performed > > by a hinged flap. The fundamental principle here is > > that for any subsonic flow system, the flow rate through the > > system will always adjust itself so that the static pressure at the > > exit will match the local external flow static pressure surrounding > > the exit. The static pressure at the exit is controlled by the > > exit area. > > > > Thus, regulation is obtained by varying this area. > > Opening the flap beyond the contour of the airframe creates a > > low-pressure region that induces additional flow through the > > system. It became common design practice during World War > > II to serve the exit flap to a coolant temperature sensor to optimize > > the system operation. > > > > > > Ed Anderson > > Rv-6A N494BW Rotary Powered > > Matthews, NC > > eanderson@carolina.rr.com > > http://www.andersonee.com > > http://www.dmack.net/mazda/index.html > > http://www.flyrotary.com/ > > http://members.cox.net/rogersda/rotary/configs.htm#N494BW > > http://www.rotaryaviation.com/Rotorhead%20Truth.htm > ------------------------------ > > *From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] *O= n > Behalf Of *Tracy Crook > *Sent:* Thursday, August 20, 2009 8:49 AM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] Re: back in the air > > > > "So far its looking like I could stand to shrink both inlets a little - > maybe a lot. " > > Mike, > Glad your EC2 & cooling issues are under control. I'd go with a cowl fla= p > to restrict air flow (and increase exit velocity) rather than reduce inle= t > size. Probably less fiberglass work for the cowl flap as well. > > Won't go into the mind numbing formulas and laws that govern the principa= l > but here is what I have boiled them down to: > > It is not the absolute SIZE of the cooling inlet that determines drag but > the *amount of air that goes through it*. > > Main thing is to make sure the air that is diverted around the inlet ha= s > a clean path. (you've done a good job there). Restricting the inlet wil= l > also restrict the flow but why reduce your options for other conditions (= hot > weather, max climb, etc). > > Tracy > > On Wed, Aug 19, 2009 at 11:30 PM, Mike Wills wrote: > > I seriously considered a water oil exchanger. Fluidyne also made some of > those that looked really good. Dont know if they still do. > > > > Ultimately decided not to go that route. So many people were having cooli= ng > issues when I was designing my system and it seemed that using seperate a= ir > oil exchangers would ease potential debug hassles. > > > > I'm mostly happy with my choice. Its working well so far. And using a $25 > wrecking yard RX-7 oil cooler was about as cheap as it gets. My only > complaints so far are that I am not real happy with the looks of the extr= a > scoop I added for the oil cooler, and my braided stainless oil cooler lin= es > are fairly long and heavy. > > > > I probably will redo the cowl somewhere down the road after I get a good > handle on just how well the cooling is on hot days. So far its looking li= ke > I could stand to shrink both inlets a little - maybe a lot. On my flight = the > other day coolant temp never went over 180. And that included taxi from t= he > extreme west end of the airport to the other end of an 8000' runway. > > > > Mike Wills > > RV-4 N144MW > > > > > --00032555967ef9f1d4047196cd46 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable
Ed,
=A0
I installed=A0a cowl flap on my Lancair.=A0 In an attempt to improve t= he hot weather cooling, I enlarged the exit area by=A0cutting a rectangular= =A0hole of approx. 4 x 15 and=A0added a 1-1/2" lip to the bottom leadi= ng edge to help coax the air out of the cowl.=A0 I later installed a servo-= actuated cowl flap so I could open and close it as necessary.=A0 I=A0chose = to go this route=A0rather than adding a thermostat to the cooling system.= =A0 I leave it open during taxi and climb, and close it once in cruise=A0wi= th temps stabilized.=A0 Works as advertised.
=A0
Mark S.
=A0
=A0=A0=A0

On Thu, Aug 20, 2009 at 12:16 PM, Ed Anderson <eanderson@= carolina.rr.com> wrote:

Interestingly, if I correctly inter= pret the extract on exit area I took from a study on aircraft liquid engine= cooling, it would seem to imply that a =93free floating=94 cowl flap would= seek its own/best position with regard to minimizing cooling drag.=A0 The = flap would open more if the air pressure on the cowl side exceeds the free = air pressure at its exit into the airstream and would be closed by the airs= tream until the pressure on both sides of the cowl flap equalized.

=A0

=A0 At least that is what it appear= s to say to me.=A0 However, minimum cooling drag may not/will not always be= conducive to maximum cooling.=A0 In some cases, like in climb, you may not= mind more drag if your cooling is better by opening the flap more than opt= imum for minimum drag.

=A0

So I imagine, you would still want = a control level/servo motor to control the extension.=A0 There is more pres= sure on the flap than you might think.=A0 I think it was Bill Eslick that t= ried a cowl flap and believe he eventually abandoned it =96 but, not certai= n if he did or exactly why (I think I knew at one time {:>) =96 Bill, sp= eak up!

=A0

Ed

=A0

From: Rota= ry motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Tracy Crook
Sent: Thursday, August 20, = 2009 10:14 AM
To: Rotary= motors in aircraft
Subject:= [FlyRotary] Re: Cowl Flap/Exit was [FlyRotary] Re: back in the air

= Count on Ed to supply the technical backgro= und :-)=A0 That's another good rule of thumb on the maximum inlet area = too=A0 (.3 *=A0 core area). =A0 More doesn't do you any good.

Main point is, You don't have to be a rocket scientist to make this= stuff work if you follow a few basic rules of thumb.=A0 (The right ones th= at is, there are a lot of bogus ones floating around as well :>) =A0
Tracy

eanderson@carolina.rr.com> wr= ote:

Past a specific inlet area to core = frontal area (this ratio in the vicinity of 0.30, no additional flow is ach= ieved by further opening of inlets =96 the exit area becomes the controllin= g factor. As Tracy stated, probably better to look to a cowl flap than mess= with your inlets if you are getting good cooling with your present inlets.=

=A0

Here is an extract out of a study o= f cooling of small aircraft engines that points out the two functions of yo= ur exit area.=A0

=A0

Exits

=A0

.

Ed Anderson

Rv-6A N494BW Rotary P= owered

Matthews, NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/maz= da/index.html

http://www.flyrotary.com/

http://memb= ers.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryaviation.co= m/Rotorhead%20Truth.htm

From: Rota= ry motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Tracy Crook
Sent: Thursday, August 20, = 2009 8:49 AM
To: Rotary = motors in aircraft
Subject:<= /b> [FlyRotary] Re: back in the air

= "So far its loo= king like I could stand to shrink both inlets a little - maybe a lot. "= ;

Mike,
Glad your EC2 & cooling issues are under control.=A0 I'= ;d go with a cowl flap to restrict air flow (and increase exit velocity) ra= ther than reduce inlet size.=A0=A0 Probably less fiberglass work for the co= wl flap as well.

Won't go into the mind numbing formulas and laws that govern the pr= incipal but here is what I have boiled them down to:

It is not the a= bsolute SIZE of the cooling inlet that determines drag but the amount of air that goes through it.
=A0 Main thing is to make sure the air that is diverted around the inle= t has a clean path.=A0 (you've done a good job there).=A0 Restricting t= he inlet will also restrict the flow but why reduce your options for other = conditions (hot weather, max climb, etc).

Tracy

rv-4mike@cox.net> wrote:=

I seriously considered a water oil exchanger. Fluidyne also mad= e some of those that looked really good. Dont know if they still do.=

Ultimately decided not to go that route. So many people were ha= ving cooling issues when I was designing my system and it seemed that using= seperate air oil exchangers would ease potential debug hassles.

I'm mostly happy with my choice. Its working well so far. A= nd using a $25 wrecking yard RX-7 oil cooler was about as cheap as it gets.= My only complaints so far are that I am not real happy with the looks of t= he extra scoop I added for the oil cooler, and my braided stainless oil coo= ler lines are fairly long and heavy.

I probably will redo the cowl somewhere down the road after I g= et a good handle on just how well the cooling is on hot days. So far its lo= oking like I could stand to shrink both inlets a little - maybe a lot. On m= y flight the other day coolant temp never went over 180. And that included = taxi from the extreme west end of the airport to the other end of an 8000&#= 39; runway.

Mike Wills

RV-4 N144MW