Return-Path: Sender: (Marvin Kaye) To: flyrotary Date: Tue, 25 Mar 2003 04:08:18 -0500 Message-ID: X-Original-Return-Path: Received: from fed1mtao07.cox.net ([68.6.19.124] verified) by logan.com (CommuniGate Pro SMTP 4.1b1) with ESMTP id 2085472 for flyrotary@lancaironline.net; Mon, 24 Mar 2003 22:53:31 -0500 Received: from Leonards ([68.8.249.39]) by fed1mtao07.cox.net (InterMail vM.5.01.04.05 201-253-122-122-105-20011231) with ESMTP id <20030325035328.ZSWM1451.fed1mtao07.cox.net@Leonards> for ; Mon, 24 Mar 2003 22:53:28 -0500 From: "David Leonard" X-Original-To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Thick or Thin? The debate continues X-Original-Date: Mon, 24 Mar 2003 19:53:31 -0800 X-Original-Message-ID: <000001c2f282$1a40a670$27f90844@Leonards> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.3416 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 David Leonard The Rotary Roster: http://members.aol.com/_ht_a/rotaryroster/index.html > > Tracy wrote: > D@*x!, lost another 2 hour message to the blue screen of death. That does it, I can't debate the issue any more. Your time is far too important to spend this much time debating what is really a minor point. In the range of the possible radiator designs your thick vs. my thin are really very close to the same thing. IMHO, this is all just minor theory points.. > Tracy replies: > > OK here is the guts of what I blathered on for two hours about: > > You are correct about the importance of the velocity of air in the drag > equation. But the air velocity through the rad is of no (or very minor) > importance. > > The velocity that matters is the velocity of the air at it's *source*. > That, of course, is the speed of the air rushing past the airplane that we > snagged to run through our cooling system. Since this speed is the same > regardless of what radiator is sitting inside the cowl, the *only* factor > that makes any difference is how much of that air we used. More air = > more > energy = more drag. > > Tracy > Yes, except. The forward energy used to slow down that incoming air is offset by any thrust you may be able to obtain from the exiting air (or, if you prefer, there is also significant drag at the exit point, this drag is inversely proportional to the speed of the exiting air). Like in a jet engine, what matters is the difference between the intake and exhaust velocity. And this is where I disagree with your first point, the rad is the main determinant of this difference in velocity between intake and exhaust (given optimum ducting- which I'll admit is darn near impossible). The more energy you loose passing air through the rad, the less you will be able to speed it for smooth exit. And it is velocity through the rad (because of its cubed effect) that is the primary determinant of energy loss there. > >> Homepage: http://www.flyrotary.com/