X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from relais.videotron.ca ([24.201.245.36] verified) by logan.com (CommuniGate Pro SMTP 5.1c.4) with ESMTP id 1410202 for flyrotary@lancaironline.net; Tue, 19 Sep 2006 12:26:32 -0400 Received-SPF: none receiver=logan.com; client-ip=24.201.245.36; envelope-from=geryvon@videotron.ca Received: from AMDSEMPRON2400 ([74.56.149.208]) by VL-MH-MR002.ip.videotron.ca (Sun Java System Messaging Server 6.2-2.05 (built Apr 28 2005)) with SMTP id <0J5U00C5GLN0A6F0@VL-MH-MR002.ip.videotron.ca> for flyrotary@lancaironline.net; Tue, 19 Sep 2006 12:25:50 -0400 (EDT) Date: Tue, 19 Sep 2006 12:25:26 -0400 From: Yvon Cournoyer Subject: Re: [FlyRotary] Re: ducted fan questions To: Rotary motors in aircraft Reply-to: Yvon Cournoyer Message-id: <002401c6dc08$435634d0$6600a8c0@AMDSEMPRON2400> MIME-version: 1.0 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2962 X-Mailer: Microsoft Outlook Express 6.00.2900.2869 Content-type: text/plain; format=flowed; charset=iso-8859-1; reply-type=response Content-transfer-encoding: 7BIT X-Priority: 3 X-MSMail-priority: Normal References: Please include me as well, thank you. Yvon. geryvon@videotron.ca ----- Original Message ----- From: "Donald Willard Garrett" To: "Rotary motors in aircraft" Sent: Monday, September 18, 2006 3:40 AM Subject: [FlyRotary] Re: ducted fan questions > Hey! If you are taking this offline, please cc me! > > Donald Garrett flyrotaryNOspam@avamail.net > > Richard Sohn wrote: >> >> ----- Original Message ----- >> *From:* Russell Duffy >> *To:* Rotary motors in aircraft >> >> *Sent:* Sunday, September 17, 2006 6:12 PM >> *Subject:* [FlyRotary] Re: ducted fan questions >> >> ing a ducted fan(not a shrouded propeller). Now that's just way >> too cool Richard :-) Was the fan running directly off the engine, >> with no redrive? Did >> you feel that the performance was better than it would have >> been with a traditional redrive and prop? If I get serious about >> trying this, I'll certainly take you up on your offer to share >> info. Cheers, >> Rusty >> There are plenty of ducted fans, look at the bypass stage of >> every >> turbofan engine. The difference between a ducted fan and a >> shrouded propeller is the blade solidity. This is the ratio of >> the >> fan cross section to the total blade area. A turbofan is around >> "1" and a shrouded propeller, I have seen, may be as low as .1 or >> less. >> My fan with the KAWA engine was running reduced at 3400RPM, in >> order to allow for more solidity with the benefit of lower noise. >> When I changed to direct drive with adjusted solidity at the same >> HP, the fan efficiency went from 70% down to less then 50%, and >> the noise was almost unbearable. >> The fan I flew had six blades, and the test fan on direct drive >> had three blades, which were smaller too. >> BTW the diameter was 26". >> The conclusion is, if you aim for a solidity of 1, or close to 1, >> for a given hp, there is only one fan size and RPM. Now, what >> compromises can be made to arrive at a practical design? Your >> imagination, and expectations, are the only limits. >> My 90+hp design has nine blades at 26", giving a solidity of .6 . >> This is not very good, however, I do not want to make a new >> shroud >> and I also have a given max RPM, which locks me in. Nevertheless, >> the data would be as good as any, knowing the deficiencies. >> So much for now. >> Should we discuss this on another E-Mail? I don't want to bore >> our >> rotor head friends. >> Richard Sohn >> N-2071U >> > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/ >