X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 30 Jun 2014 10:39:09 -0400 Message-ID: X-Original-Return-Path: Received: from pt-smtp-02.commander.net.au ([218.214.227.99] verified) by logan.com (CommuniGate Pro SMTP 6.0.9e) with SMTP id 6957192 for lml@lancaironline.net; Mon, 30 Jun 2014 08:13:42 -0400 Received-SPF: pass receiver=logan.com; client-ip=218.214.227.99; envelope-from=stevens5@swiftdsl.com.au Received: (qmail 23583 invoked from network); 30 Jun 2014 12:13:05 -0000 Received: from unknown (HELO StevensPC) (218.215.192.175) by pt-smtp-02.commander.net.au with SMTP; 30 Jun 2014 12:13:05 -0000 From: "Stevens Family" X-Original-To: "'Lancair Mailing List'" References: In-Reply-To: Subject: RE: [LML] Re: Two-blade or three-blade prop for I-550 X-Original-Date: Mon, 30 Jun 2014 20:13:03 +0800 X-Original-Message-ID: <000601cf945c$a6734cf0$f359e6d0$@swiftdsl.com.au> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0007_01CF949F.B498D6E0" X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQI8rf5aJSzFosPF9vD++yAo9Xhv+JqvWsFw Content-Language: en-au This is a multipart message in MIME format. ------=_NextPart_000_0007_01CF949F.B498D6E0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit I am interested in this subject, because I purchased a partly built kit some years ago, (which I am still building!) which came with an MT 3 bladed constant speed prop. In my conversation with a builder in South Australia recently, he mentioned that he had swapped out his 3 Blade MT prop for a 2 blade prop, and increase his cruise speed by 7 knots. (Can't recall if that was 7 Kts indicated, or 7 Kts TAS.) Not sure how this fits with the graphs which indicate the 3 blades are more efficient! It was my understanding that because a 3 bladed prop generates 3 tip vortices against only two on a 2 bladed prop, it is less efficient. Rob Stevens Perth, Western Australia. From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Charles Brown Sent: Monday, 30 June 2014 7:38 PM To: Lancair Mailing List Subject: [LML] Re: Two-blade or three-blade prop for I-550 I've enclosed the spreadsheet provided to me by Les Doud of Hartzell. In 2009 his phone number was Phone: 937-778-4262 . He believes that the 3-blade is more effiicient than the two blade even in cruise. I have a hard time believing that, and my airplane with 3 blades has not lived up to the prototype Legacy's performance with the 2-blade as documented in the CAFE report; and the 3-blade is heavier and more expensive to buy and overhaul. Of course, my airplane is probably not as clean as the prototype. But the 3-blade prop sure looks cool. ------=_NextPart_000_0007_01CF949F.B498D6E0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

I am interested in this subject, because I purchased a partly built = kit some years ago, (which I am still building!) which came with an MT 3 = bladed constant speed prop. In my conversation with a builder in South = Australia recently, he mentioned that he had swapped out his 3 Blade MT = prop for a 2 blade prop, and increase his cruise speed by 7 knots. = (Can’t recall if that was 7 Kts indicated, or 7 Kts TAS.) Not sure = how this fits with the graphs which indicate the 3 blades are more = efficient! It was my understanding that because a 3 bladed prop = generates 3 tip vortices against only two on a 2 bladed prop, it is less = efficient.

 

 

Rob Stevens

Perth, Western Australia.

 

 

From:= Lancair = Mailing List [mailto:lml@lancaironline.net] On Behalf Of Charles = Brown
Sent: Monday, 30 June 2014 7:38 PM
To: Lancair = Mailing List
Subject: [LML] Re: Two-blade or three-blade prop = for I-550

 

I've = enclosed the spreadsheet provided to me by Les Doud of Hartzell. =  In 2009 his phone number was Phone: = 937-778-4262 .  He believes that the 3-blade is more = effiicient than the two blade even in cruise.  I have a hard time = believing that, and my airplane with 3 blades has not lived up to the = prototype Legacy's performance with the 2-blade as documented in the = CAFE report; and the 3-blade is heavier and more expensive to buy and = overhaul.  Of course, my airplane is probably not as clean as the = prototype.

 

But the 3-blade prop sure looks = cool. 

 

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