X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from el-out-1112.google.com ([209.85.162.176] verified) by logan.com (CommuniGate Pro SMTP 5.2c1) with ESMTP id 2496876 for flyrotary@lancaironline.net; Mon, 19 Nov 2007 21:26:35 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.162.176; envelope-from=rwstracy@gmail.com Received: by el-out-1112.google.com with SMTP id r23so691773elf for ; Mon, 19 Nov 2007 18:25:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:sender:to:subject:in-reply-to:mime-version:content-type:references:x-google-sender-auth; bh=LutrQWVCQcloPsHcBQTwouh+vyYhIjUJyAkWsYeuyCQ=; b=dA3rL+7+6D87/n9VdDOSIsjLYWdlPLoFnZt0uPJgrbPBs0xdfSDqLGjl6EU3VCFk+sR8c+PDAS3iLbSqfvQJBnNt6f18HEzunrkr7hUcpvu5ADj4d+xEKmxlltfKQxEN/fG6wMRTRNaWCP0Ewik5MQjgAT3rBBeur6G+HphrdbQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:sender:to:subject:in-reply-to:mime-version:content-type:references:x-google-sender-auth; b=pAhSLQBgdMYMQATqWDSxAmEgZ7I8tQjUv+F2CW0lBXZTOb1bQeaA8gSWSODoBTsPsl+gF2lRUIIH9Cl/j70c3KtEnQ+aEC+dyMspeBNSDerdD35H5tSRg18OA76mm6VcLi3ZfgMZ9AaOghSnrsTDhTp+wI77eoS28xJPZClKKDg= Received: by 10.142.126.17 with SMTP id y17mr1383858wfc.1195525557850; Mon, 19 Nov 2007 18:25:57 -0800 (PST) Received: by 10.142.98.2 with HTTP; Mon, 19 Nov 2007 18:25:57 -0800 (PST) Message-ID: <1b4b137c0711191825ub57c01agd02fa55c081c3de0@mail.gmail.com> Date: Mon, 19 Nov 2007 21:25:57 -0500 From: "Tracy Crook" Sender: rwstracy@gmail.com To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] Re: Thick vs Thin was : Diffuser Configuration Comparison In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_19463_262838.1195525557847" References: X-Google-Sender-Auth: c2fdb1a895263075 ------=_Part_19463_262838.1195525557847 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline On Nov 15, 2007 10:14 PM, David Leonard wrote: Tracy Crook Wrote: > This is where it starts to go badly wrong and/or misses the whole > > point. The main object of using a thick rad is to use fewer CFM > > (lower mass flow rate). If you want to assume same mass flow, there > > is no advantage *(and probably a disadvantage) for a thick rad*. > > > > Ah HA! You heard it folks, right there in black and white. Not so fast there Dave! I DON'T want to assume the same mass flow. That is the core of my argument. The thing that I want to argue about (so I can learn something if I'm wrong) is my contention that the cooling system with the lowest AIRCRAFT drag is the one with the LOWEST MASS AIRFLOW. > > > If 2.75" IS a thick rad, then I must be on your side of the discussion all > along, as my rad is 3" thick. Yet it is as wide and long as I could > reasonably fit under the cowl. > And your airplane is probably faster than mine. But only when you crank up some boost with that turbo! And keep in mind I am not arguing from the standpoint of which system will cool the engine the best, I'm looking for the system with the lowest cooling drag. This contest should be framed in terms of which airplane would go fastest on a given amount of HP (or fuel flow), all else except cooling system being equal. > > This brings me to my final point (promise I won't make anymore points). > Use the widest-thinnest radiator you can reasonably fit under the cowl and > make appropriate ducting. I guarantee that you don't want to use the > thickest-narrowest rad you can fit. That would not cool well at all. > -- > David Leonard > Hey, wait a minute! Why didn't you take your own advice? I'm sure you could have found a radiator thinner than 3". Did you mean to say widest & thickest? That would be the combination to use to insure the best chance of cooling adequately (but not necessarily the lowest drag or weight). Bernie Kerr did use the widest & thinnest approach on his RV-9 and it had lousy cooling. Tracy (never promises not to make more points : ) ------=_Part_19463_262838.1195525557847 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline

On Nov 15, 2007 10:14 PM, David Leonard <wdleonard@gmail.com> wrote:

Tracy Crook Wrote:
This is where it starts to go badly wrong and/or misses the whole
point.  The main object of using a thick rad is to use fewer CFM
(lower mass flow rate).   If you want to assume same mass flow, there
is no advantage (and probably a disadvantage) for a thick rad.
 
Ah HA!  You heard it folks, right there in black and white.
 
Not so fast there Dave!  I DON'T want to assume the same mass flow.  That is the core of my argument.   The thing that I want to argue about (so I can learn something if I'm wrong) is my contention that the cooling system with the lowest AIRCRAFT drag is the one with the LOWEST MASS AIRFLOW. 


If 2.75" IS a thick rad, then I must be on your side of the discussion all along, as my rad is 3" thick.  Yet it is as wide and long as I could reasonably fit under the cowl. 
And your airplane is probably faster than mine.  But only when you crank up some boost with that turbo!    And keep in mind I am not arguing from the standpoint of which system will cool the engine the best, I'm looking for the system with the lowest cooling drag.  This contest should be framed in terms of which airplane would go fastest on a given amount of HP (or fuel flow), all else except cooling system being equal.
 

This brings me to my final point (promise I won't make anymore points).  Use the widest-thinnest radiator you can reasonably fit under the cowl and make appropriate ducting.  I guarantee that you don't want to use the thickest-narrowest rad you can fit.  That would not cool well at all.
--
David Leonard
Hey, wait a minute! Why didn't you take your own advice?  I'm sure you could have found a radiator thinner than 3".  Did you mean to say widest & thickest?  That would be the combination to use to insure the best chance of cooling adequately (but not necessarily the lowest drag or weight).   Bernie Kerr did use the widest & thinnest approach on his RV-9 and it had lousy cooling.
 
Tracy (never promises not to make more points : )
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