X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from qw-out-2122.google.com ([74.125.92.24] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3819421 for flyrotary@lancaironline.net; Thu, 20 Aug 2009 12:32:08 -0400 Received-SPF: pass receiver=logan.com; client-ip=74.125.92.24; envelope-from=rwstracy@gmail.com Received: by qw-out-2122.google.com with SMTP id 3so8970qwe.25 for ; Thu, 20 Aug 2009 09:31:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:received:in-reply-to :references:date:x-google-sender-auth:message-id:subject:from:to :content-type; bh=3whH/gsd/yVcgi4xqbEOniYJwJ9jWzQz+L+nDDvqxt4=; b=a752DdAhS0vTWzwewm1dFCxxnPjMunEQjrv/0Hl4r0m67Azo/7czLKbZ7Wr/k/dDdE 8NhPlaf2frKpcXjxDDjfaWkqGlY3YBTkrp/IgcY3nkWv9JLoYGEPCltnZKEiUWQu2hkS ouAGZhIbcE0nRzcTnjb7hOqQ0O/K2w33iTPBk= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:content-type; b=D/gu8xtUjadsUUMKhRcWCB46/CXTuHmjADVTIA9fR1G1nf0VfasIu7JcHopYsb/APC nmxuW6Ccp3lm4v2c68/pgYUTM50AwEfK7AXD7SrzOnCeSrfRRwOvjCOyWswKVyw9bZJD 5UAHQZeAcr9sjSLa+eu1mgjqXSNjp/tExK/wU= MIME-Version: 1.0 Sender: rwstracy@gmail.com Received: by 10.224.42.75 with SMTP id r11mr7678134qae.321.1250785887083; Thu, 20 Aug 2009 09:31:27 -0700 (PDT) In-Reply-To: References: Date: Thu, 20 Aug 2009 12:31:27 -0400 X-Google-Sender-Auth: 2a1f3140a67e032f Message-ID: <1b4b137c0908200931h7be1727k29fff6263e32c03a@mail.gmail.com> Subject: Re: [FlyRotary] Re: Cowl Flap/Exit was [FlyRotary] Re: back in the air From: Tracy Crook To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=000feaf1dc997e84430471954867 --000feaf1dc997e84430471954867 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable "What are you going with on your 20B?" I assume you mean for radiator? I used an off the shelf Griffin rad 12 x 1= 8 x 2.625" core. Just barely shy of 2 ci / HP. Just completed first low speed taxi test on the RV-8. Squawks were failed position light on left wing (LED type) and oil leak due to loose oil line fitting. Tracy On Thu, Aug 20, 2009 at 11:41 AM, Thomas Mann wrote: > Tracy, > > What are you going with on your 20B? > > I=92m not to this point yet but the question has been rattling around in = my > head. > > > > T Mann > > > > *From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] *O= n > Behalf Of *Tracy Crook > *Sent:* Thursday, August 20, 2009 9:43 AM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] Re: Cowl Flap/Exit was [FlyRotary] Re: back in the > air > > That's a more complicated question than a ROT can resolve. > > The simplest we have been able to reduce it to is a core VOLUME > requirement. A volume between 2 and 3 CUBIC inches per HP seems to work > OK. The thinner the rad (and larger the core *frontal area*), the lower > core volume you might get away with (at a cost of more drag!) The thicke= r > the rad, the higher Ci/HP value you should aim for. Lots of other fact= ors > involved as well. Location, room available, duct size & quality, cruise > speed of aircraft, etc, etc. > > Note that we haven't included oil cooling cores in the discussion at this > point. Oil is about 1/3 of total cooling in the rotary. > > Tracy > > > > > > > > > > On Thu, Aug 20, 2009 at 10:21 AM, Bryan Winberry < > bryanwinberry@bellsouth.net> wrote: > > With this ROT in mind, would a cowl that has an inlet area of say 50 sq.i= n, > be overkill? This would support about 150 sq.in. of core area. > > IOW, what=92s a good core area for the rotary? > > Bryan > > > ------------------------------ > > *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 > > > > > > > --000feaf1dc997e84430471954867 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable "What are yo= u going with on your 20B?"

I assume you mean for radiator?=A0 I= used an off the shelf Griffin rad 12 x 18 x 2.625" core.=A0 Just bare= ly shy of 2 ci / HP.=A0

Just completed first low speed taxi test on the RV-8.=A0 Squawks were f= ailed position light on left wing (LED type) and oil leak due to loose oil = line fitting.=A0

Tracy

On = Thu, Aug 20, 2009 at 11:41 AM, Thomas Mann <tmann@n200lz.com> wrote:

Tracy,<= /p>

What are you g= oing with on your 20B?

I=92m not to t= his point yet but the question has been rattling around in my head.

=A0

T Mann<= /p>

=A0

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Tracy Crook
Sent: Thursday, August 20, 2009 9:43 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Cowl Flap/Exit was [FlyRotary] Re: back in = the air

That's a more compli= cated question than a ROT can resolve.

The simplest we have been able to reduce it to is a core VOLUME requirement.=A0=A0 A volume between 2 and 3 CUBIC inches per HP seems to work OK.=A0 The thinner the rad (and larger the core frontal area), the lower core volume you might get away with (at a cost of more drag!)=A0 The thicker the rad, the higher Ci/HP=A0 value you should aim for.=A0=A0 Lots of other factors involved as well.=A0 Location, room available, duct size & quality, cruise speed of aircraft, etc, etc.

Note that we haven't included oil cooling cores in the discussion at= this point.=A0 Oil is about 1/3 of total cooling in the rotary.

Tracy

=A0

=A0





On Thu, Aug 20, 2009 at 10:21 AM, Bryan Winberry <bryanwinberry@bellsouth.net> wrote:

With this ROT in mind, would a cowl that has an inlet area of say 50 sq.in, be overkill? =A0This would support about 150 sq.in. of = core area.

IOW, what=92s a good core area for the rotary?

Bryan

=A0

From: Rotary 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

=A0

Count on Ed to supply the technical backg= round :-)=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 stu= ff work if you follow a few basic rules of thumb.=A0 (The right ones that is, there are a lot of bogus ones floating around as well :>) =A0

Tracy

On Thu, Aug 20, 2009 at 9:49 AM, Ed Anderson <eanderson@carolina.rr.com> wrote:

Past a specific inlet area to core frontal area (this ratio in the vicinity of 0= .30, no additional flow is achieved by further opening of inlets =96 the exit ar= ea becomes the controlling factor. As Tracy stated, probably better to look to= a cowl flap than mess with your inlets if you are getting good cooling with y= our present inlets.

=A0

Here is an extract out of a study of cooling of small aircraft engines that poin= ts out the two functions of your exit area.=A0

=A0

Exits

=A0

The exit has two basic functions: to re= gulate the cooling air

flow and to exhaust the cooling flow in= to the external flow so

as to result in minimal drag penalty. T= o adequately perform

the regulation, the exit must act as bo= th a throttle and a pump.

Throttling is necessary in cruising fli= ght to minimize the cooling

drag by reducing the cooling flow to th= at sufficient to meet

cooling requirements.

=A0

=A0In ground operation and in climbing<= /span>

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 princ= iple here is

that for any subsonic flow system, the = flow rate through the

system will always adjust itself so tha= t the static pressure at the

exit will match the local external flow static pressure surrounding

the exit. The static pressure at the ex= it is controlled by the

exit area.

=A0

=A0Thus, regulation is obtained by vary= ing this area.

Opening the flap beyond the contour of = the airframe creates a

low-pressure region that induces additi= onal flow through the

system. It became common design practic= e during World War

II to serve the exit flap to a coolant temperature sensor to optimize

the system operation.

=A0

=A0

Ed Anderson

Rv-6A N494BW R= otary Powered

Matthews, NC

eanderson@carolina.rr.com<= /a>

http://www.andersonee.com

http://www.dmac= k.net/mazda/index.html

http://www.flyrotary.com/

ht= tp://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryav= iation.com/Rotorhead%20Truth.htm

From: Rotary 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: [FlyRotary] Re: back in the air

=A0

"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.=A0 I'd go with a = cowl flap to restrict air flow (and increase exit velocity) rather than reduce i= nlet size.=A0=A0 Probably less fiberglass work for the cowl flap as well.

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

It is not the absolute SIZE of the cooling inlet that determines drag but t= he amount of air that goes through it.

=A0 Main thing is to make sure the air that is diverted around the inlet ha= s a clean path.=A0 (you've done a good job there).=A0 Restricting the inl= et will also restrict the flow but why reduce your options for other condition= s (hot weather, max climb, etc).

Tracy

On Wed, Aug 19, 2009 at 11:30 PM, Mike Wills <rv-4mike@cox.net> wrote:

I seriously considered a water oil exchanger. Fluidyne also made some of those that loo= ked really good. Dont know if they still do.

=A0

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

=A0

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

=A0

I probably will redo the cowl somewhere down the road after I get a good handle on jus= t how well the cooling is on hot days. So far its looking like I could stand = to shrink both inlets a little - maybe a lot. On my flight the other day coola= nt temp never went over 180. And that included taxi from the extreme west end = of the airport to the other end of an 8000' runway.

=A0

Mike Wills

RV-4 N144MW

=A0

=A0

=A0


--000feaf1dc997e84430471954867--