X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 01 Jul 2014 16:36:15 -0400 Message-ID: X-Original-Return-Path: Received: from [107.14.166.229] (HELO cdptpa-oedge-vip.email.rr.com) by logan.com (CommuniGate Pro SMTP 6.0.9e) with ESMTP id 6959148 for lml@lancaironline.net; Tue, 01 Jul 2014 11:27:38 -0400 Received-SPF: none receiver=logan.com; client-ip=107.14.166.229; envelope-from=Wolfgang@MiCom.net X-Original-Return-Path: Received: from [74.218.201.50] ([74.218.201.50:1375] helo=lobo) by cdptpa-oedge03 (envelope-from ) (ecelerity 3.5.0.35861 r(Momo-dev:tip)) with ESMTP id 95/A8-02848-743D2B35; Tue, 01 Jul 2014 15:27:03 +0000 X-Original-Message-ID: <3BF3A9CAF44B49C4A4D10918926F9359@lobo> From: "Wolfgang" X-Original-To: "Lancair" , "John Barrett" References: Subject: Re: [LML] Re: Two-blade or three-blade prop for I-550 X-Original-Date: Tue, 1 Jul 2014 11:27:00 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00B0_01CF951F.600CA540" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5512 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5512 X-RR-Connecting-IP: 107.14.168.142:25 X-Cloudmark-Score: 0 This is a multi-part message in MIME format. ------=_NextPart_000_00B0_01CF951F.600CA540 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable "the fewest number of blades to get the job done is most efficient" The only reason for more than two blades is you have too much HP.=20 More blades (more blade area) will let you convert that extra HP to = thrust. You can produce only so much thrust for a given blade area and speed = before you get blade stall. Wolfgang ----- Original Message -----=20 From: John Barrett=20 Sent: Monday, June 30, 2014 4:10 PM Subject: RE: [LML] Re: Two-blade or three-blade prop for I-550 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.=20 =20 Don't believe anything I say here. The memories are about 10 years = old.=20 =20 John Barrett=20 =20 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 =20 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. =20 =20 Rob Stevens Perth, Western Australia. =20 =20 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 =20 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. =20 But the 3-blade prop sure looks cool.=20 =20 ------=_NextPart_000_00B0_01CF951F.600CA540 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
"the fewest=20 number of blades to get the job done is most = efficient"
The only reason for more than two = blades is you=20 have too much HP.
More blades (more blade area) will let = you convert=20 that extra HP to thrust.
You can produce only so much thrust for = a given=20 blade area and speed before you get blade stall.
 
Wolfgang
 
----- Original Message -----
From:=20 John=20 Barrett
Sent: Monday, June 30, 2014 = 4:10 PM
Subject: RE: [LML] Re: = Two-blade or=20 three-blade prop for I-550

I=20 understood from conversations with some prop designers a few years ago = (can=92t=20 recall who) that the fewest number of blades to get the job done is = most=20 efficient.  One blade would be best except for obvious balance=20 issues.  So the remaining factors include how much HP one blade = can=20 absorb.  I seem to remember that three was the minimum for an = engine that=20 goes much over 300 HP at least for the hubs and props we were looking = at for=20 the IVP.  This info may have come from MT because I was looking = at the=20 five blade MT vs four.  My understanding at that time was that = more=20 blades result in  quieter smoother ops but give up small amounts = of=20 efficiency.

 

Don=92t=20 believe anything I say here.  The memories are about 10 years = old.=20

 

John=20 Barrett

 

From: Lancair = Mailing=20 List [mailto:lml@lancaironline.net] On Behalf Of Stevens=20 Family
Sent: Monday, June 30, 2014 7:39 AM
To: = Lancair=20 Mailing List
Subject: [LML] Re: Two-blade or three-blade = prop for=20 I-550

 

I am interested in this subject, because I purchased a = partly built=20 kit some years ago, (which I am still building!) which came with an MT = 3=20 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=20 for a 2 blade prop, and increase his cruise speed by 7 knots. (Can=92t = recall if=20 that was 7 Kts indicated, or 7 Kts TAS.) Not sure how this fits with = the=20 graphs which indicate the 3 blades are more efficient! It was my = understanding=20 that because a 3 bladed prop generates 3 tip vortices against only two = on a 2=20 bladed prop, it is less efficient.

 

 

Rob Stevens

Perth, Western Australia.

 

 

From: Lancair = Mailing=20 List [mailto:lml@lancaironline.net]=20 On Behalf Of Charles Brown
Sent: Monday, 30 June 2014 = 7:38=20 PM
To: Lancair Mailing List
Subject: [LML] Re: = Two-blade=20 or three-blade prop for I-550

 

I've enclosed the spreadsheet = provided to=20 me by Les Doud of Hartzell.  In 2009 his phone number=20 was Phone:=20 937-778-4262 .  He believes that = the 3-blade=20 is more effiicient than the two blade even in cruise.  I have a = hard time=20 believing that, and my airplane with 3 blades has not lived up to the=20 prototype Legacy's performance with the 2-blade as documented in the = CAFE=20 report; and the 3-blade is heavier and more expensive to buy and = overhaul.=20  Of course, my airplane is probably not as clean as the=20 prototype.

 

But the 3-blade prop sure = looks=20 cool. 

 

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