X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 30 Jun 2014 16:10:22 -0400 Message-ID: X-Original-Return-Path: Received: from carbinge.com ([69.5.27.218] verified) by logan.com (CommuniGate Pro SMTP 6.0.9e) with SMTP id 6957568 for lml@lancaironline.net; Mon, 30 Jun 2014 11:24:19 -0400 Received-SPF: none receiver=logan.com; client-ip=69.5.27.218; envelope-from=jbarrett@carbinge.com Received: (qmail 23173 invoked from network); 30 Jun 2014 15:23:44 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; h=X-Originating-IP:From:To:References:In-Reply-To:Subject:Date:Message-ID:MIME-Version:Content-Type:X-Mailer:Thread-Index:Content-Language; s=default; d=carbinge.com; b=OShb6eklsxT5XhE+cviX021J4whafJ+YdqXQM1f9Or0gsnQSi2gH7uX1P/DbIz1YZjczuDG7wUl1nsCOK6vqxWxxV+ac0l5/ou+MLpfCeKFIvct95GX7XfOxyYSe/p1Oec9v5xDGEOaDwuAMY8ESkW3jsydsVrSPLqxnOdL8Zwk=; X-Originating-IP: [208.53.115.208] From: "John Barrett" 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 08:23:43 -0700 X-Original-Message-ID: <0e7e01cf9477$47bfe090$d73fa1b0$@com> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0E7F_01CF943C.9B610890" X-Mailer: Microsoft Office Outlook 12.0 Thread-Index: Ac+UcQ5ZlR3jkV60TpayHFgRI85R1wABVF5g Content-Language: en-us This is a multi-part message in MIME format. ------=_NextPart_000_0E7F_01CF943C.9B610890 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit I understood from conversations with some prop designers a few years ago (can't recall who) that the fewest number of blades to get the job done is most efficient. One blade would be best except for obvious balance issues. So the remaining factors include how much HP one blade can absorb. I seem to remember that three was the minimum for an engine that goes much over 300 HP at least for the hubs and props we were looking at for the IVP. This info may have come from MT because I was looking at the five blade MT vs four. My understanding at that time was that more blades result in quieter smoother ops but give up small amounts of efficiency. Don't believe anything I say here. The memories are about 10 years old. John Barrett From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Stevens Family Sent: Monday, June 30, 2014 7:39 AM To: Lancair Mailing List Subject: [LML] Re: Two-blade or three-blade prop for I-550 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_0E7F_01CF943C.9B610890 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

I understood from conversations with some prop designers a few years = ago (can’t recall who) that the fewest number of blades to get the = job done is most efficient.  One blade would be best except for = obvious balance issues.  So the remaining factors include how much = HP one blade can absorb.  I seem to remember that three was the = minimum for an engine that goes much over 300 HP at least for the hubs = and props we were looking at for the IVP.  This info may have come = from MT because I was looking at the five blade MT vs four.  My = understanding at that time was that more blades result in  quieter = smoother ops but give up small amounts of efficiency. =

 

Don’t believe anything I say here.  The memories are about = 10 years old.

 

John Barrett

 

From:= = Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of = Stevens Family
Sent: Monday, June 30, 2014 7:39 = AM
To: Lancair Mailing List
Subject: [LML] Re: = Two-blade or three-blade prop for = I-550

 

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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