X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.101] (HELO ms-smtp-02-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 1030414 for flyrotary@lancaironline.net; Sat, 11 Mar 2006 00:55:09 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.101; envelope-from=echristley@nc.rr.com Received: from [192.168.0.253] (cpe-066-057-036-199.nc.res.rr.com [66.57.36.199]) by ms-smtp-02-eri0.southeast.rr.com (8.13.4/8.13.4) with ESMTP id k2B5sLLp011983 for ; Sat, 11 Mar 2006 00:54:22 -0500 (EST) Message-ID: <4412660D.7040504@nc.rr.com> Date: Sat, 11 Mar 2006 00:54:21 -0500 From: Ernest Christley User-Agent: Mozilla Thunderbird 1.0.7-2.1.fc4.nr (X11/20051011) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: NACA's, Cooling and Sport Aviation Mag.. References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Symantec AntiVirus Scan Engine rijakits wrote: >How can one calculate/computer analyze/test all different >variations efficiently before starting to cut metal (or sticking glasfibers >together....)? > > > You'd need one of the rather expensive packages that do computational fluid dynamics and a few years to learn how to use it. After that, you'd need a wind tunnel to verify what the package is telling you. They all make some base assumptions to simplify the calculations, and not every package makes the same assumptions. Then there is the problem of computer round off errors (a problem that Mother Nature doesn't suffer from). Even if all the initial assumptions were correct and you used it flawlessly, the computer may still give you the wrong answers. >Anyone knows a source for reports on the difference between NACA-low >pressure cooling systems versus Ram pressure systems? The real interist >thing would of course be the Drag-difference at the same cooling >results..... > > Either it's all still classified, or NASA sort of gave up on this sort of testing around the end of WW2. Everything was going to jets, and there were much more expensive fish to fry. Unfortunately, this was about the time that the questions we're asking were about to be answered. Very few hombuilders have the budget or patience to make 100 variations on a duct and test them in a laboratory grade wind tunnel. -- This is by far the hardest lesson about freedom. It goes against instinct, and morality, to just sit back and watch people make mistakes. We want to help them, which means control them and their decisions, but in doing so we actually hurt them (and ourselves)."