X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao107.cox.net ([68.230.241.39] verified) by logan.com (CommuniGate Pro SMTP 5.1.11) with ESMTP id 2250626 for flyrotary@lancaironline.net; Wed, 08 Aug 2007 14:15:10 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.39; envelope-from=alventures@cox.net Received: from fed1rmimpo01.cox.net ([70.169.32.71]) by fed1rmmtao107.cox.net (InterMail vM.7.08.02.01 201-2186-121-102-20070209) with ESMTP id <20070808181432.EUPP7349.fed1rmmtao107.cox.net@fed1rmimpo01.cox.net> for ; Wed, 8 Aug 2007 14:14:32 -0400 Received: from BigAl ([72.192.132.90]) by fed1rmimpo01.cox.net with bizsmtp id ZWEX1X00W1xAn3c0000000; Wed, 08 Aug 2007 14:14:31 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: electric fans Date: Wed, 8 Aug 2007 11:14:24 -0800 Message-ID: <000001c7d9f0$54f26a60$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C7D9AD.46CF2A60" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C7D9AD.46CF2A60 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Here is my experience with an auxiliary cooling fan. For my pusher = canard Velocity, I got pretty good draw through the in-cowl radiator from the negative pressure from the prop - but not enough. I added a 10" high performance Spal fan ( http://www.jaycorptech.com/showproduct.aspx?productid=3D11&categoryid=3D2= ) which mounted very nicely on 16 x 11 radiator. It pretty much gives me = unlimited time waiting for takeoff; and is a good way of reducing in-cowl temps by letting it run for awhile after shutdown. =20 I did not notice any decrease in cooling during flight after installing = the fan, nor do I notice any difference whether it is left on, or not, = during flight. =20 It's rated at about 1000 cfm, and I find it draws about 11 A. If I find = the coolant temps above about 180F before I get cleared on the runway, I = turn it on. It is on my checklist to turn it off prior to takeoff.=20 =20 Al=20 =20 =20 -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anderson Sent: Wednesday, August 08, 2007 6:03 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: electric fans =20 Humm, =20 Rusty, I think a fan might be useful for ground operations, but once airborne, my calculations indicate it would likely hinder airflow more = than help it. =20 Here's the rationale. =20 Normally, duct design calls for slowing duct air velocity down to 0.1 cruise speed or 0.3 Climb speed (Horner). So if your cruise climb is = 120 MPH IAS then the air flow in the duct should (ideally) be around 0.3 * = 120 =3D 36 MPH. That is 36 MPH or 52.8 feet/sec. =20 With a core with a face area of say 200 sq inch. That would give 52.8 * 200/144 =3D 73 cubic feet/sec or 73*60 =3D 4400 CFM of air flow = through the core. I personally doubt a fan would do anything more than hinder that = much air flow. If you are not getting that much air flow, then I believe attention to the ducting would be more productive than adding a fan. = But, that is just my opinion based on back of envelope calculations.=20 =20 Again, for ground and taxi operations, I agree, a Fan would undoubtedly help, but I don't believe it would help once airborne. =20 FWIW =20 Ed =20 . =20 ----- Original Message -----=20 From: Russell Duffy =20 To: Rotary motors in aircraft=20 Sent: Wednesday, August 08, 2007 9:16 AM Subject: [FlyRotary] electric fans =20 Greetings, =20 I've only been skimming through the cooling posts, but I haven't seen = much talk of electric fans. I was thinking about this during my drive time yesterday, and it seems to me that we have exactly the same need for an electric fan as a car does. =20 =20 - Packaging limits size and location of radiators. - Ducting optimized for normal cruise speed, fan compensates at low = speeds. =20 It would seem to me that the best situation would be to optimized your = inlet and ducting for normal cruise flight, then use a fan during climb. The drawbacks would be weight, drag, and perhaps bearing life on the fan, = but the positives could make up for these I think. =20 =20 From what I've read, it's common to use a switch to tie the motor leads together, which keeps the motor from completely freewheeling when = unpowered in cruise. It would seem that you can reduce the drag and bearing = problems that way. I would also think a clever guy could provide a switch mode = that allows you to generate alternate electricity from the freewheeling fan. = =20 Just something old to think about again.=20 =20 Rusty =20 ------=_NextPart_000_0001_01C7D9AD.46CF2A60 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message

Here is my experience with an = auxiliary cooling fan.  For my pusher canard Velocity= , I got pretty good draw through the in-cowl radiator from = the negative pressure from the prop – but not enough.  I added a = 10” high performance Spal fan (http://www.jaycorptech.com/showproduct.aspx?product= id=3D11&categoryid=3D2) which mounted very nicely on 16 x 11 radiator.  It = pretty much gives me unlimited time waiting for takeoff; and is a good way of = reducing in-cowl temps by letting it run for awhile after = shutdown.

 

I did not notice any decrease in = cooling during flight after installing the fan, nor do I notice any difference = whether it is left on, or not, during flight.

 

It’s rated at about 1000 = cfm, and I find it draws about 11 A.  If I find the coolant temps above = about 180F before I get cleared on the runway, I turn it on.  It is on my = checklist to turn it off prior to takeoff.

 

Al

 

 

-----Original = Message-----
From: Rotary motors in = aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anderson
Sent: Wednesday, August 08, 2007 6:03 = AM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: = electric fans

 

Humm,

 

Rusty, I think a fan might = be useful for ground operations, but once airborne, my calculations indicate = it would likely hinder airflow more than help it.

 

Here's the = rationale.

 

  Normally, duct = design calls for slowing duct air velocity down to 0.1 cruise speed or 0.3 Climb = speed (Horner).   So if your cruise climb is 120 MPH IAS then the = air flow in the duct should (ideally) be around 0.3 * 120 =3D 36 MPH.  That = is 36 MPH or 52.8 feet/sec. 

With a core with a face = area of say 200 sq inch.  That would give 52.8 * 200/144 =3D 73 cubic = feet/sec  or  73*60 =3D 4400 CFM of air flow through the core.  I personally doubt a fan would do anything more than hinder that much air flow.   If you are not getting that much air flow, then I = believe attention to the ducting would be more productive than adding a fan.  But, = that is just my  opinion based on back of envelope = calculations. 

 

Again, for ground and taxi operations, I agree, a Fan would undoubtedly help, but I don't believe = it would help once airborne.

 

FWIW

 

Ed

 

. 

=

----- Original Message = -----

Sent: Wednesday, August 08, 2007 9:16 AM

Subject: [FlyRotary] electric fans

 

Greetings,

=

 

I've only been skimming = through the cooling posts, but I haven't seen much talk of electric fans.  I = was thinking about this during my drive time yesterday, and it seems to me = that we have exactly the same need for an electric fan as a car does.  =

 

- Packaging limits size and = location of radiators.

- Ducting optimized = for normal cruise speed, fan compensates at low = speeds.  

 

It would seem to me = that the best situation would be to optimized your inlet and = ducting for normal cruise flight, then use a fan during climb.  = The drawbacks would be weight, drag, and perhaps bearing life on the fan, = but the positives could make up for these I = think.  

 

From what I've read, it's = common to use a switch to tie the motor leads together, which keeps the = motor from completely freewheeling when unpowered = in cruise.   It would seem that you can reduce the drag and bearing problems that = way.  I would also think a clever guy could provide a switch mode that allows = you to generate alternate electricity from the freewheeling = fan.  

 

Just something old to = think about again. 

 

Rusty

  

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