X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from smtp101.vzn.mail.mud.yahoo.com ([68.142.203.45] verified) by logan.com (CommuniGate Pro SMTP 5.2.1) with SMTP id 2830106 for flyrotary@lancaironline.net; Thu, 03 Apr 2008 00:11:08 -0400 Received: (qmail 68815 invoked from network); 3 Apr 2008 04:10:47 -0000 Received: from unknown (HELO ?192.168.1.44?) (pjmick@verizon.net@71.111.117.110 with plain) by smtp101.vzn.mail.mud.yahoo.com with SMTP; 3 Apr 2008 04:10:46 -0000 X-YMail-OSG: _ro5jEoVM1kMv5AFP9mJB5dF8jrlO2hI3pmggskvDR6Ac.nb0BtRY1b58VQqVbVyyastP6wZCYM75ftDaosT0t0sPjAJvestrQmXl2sxCTmwBsKw6h0- X-Yahoo-Newman-Property: ymail-3 Message-ID: <47F462D3.9060109@verizon.net> Date: Wed, 02 Apr 2008 20:53:39 -0800 From: Perry Mick User-Agent: Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 To: flyrotary@lancaironline.net Subject: Re: [FlyRotary] Re: Prop selection Content-Type: multipart/alternative; boundary="------------070405030204040303050503" This is a multi-part message in MIME format. --------------070405030204040303050503 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit I assume you still might have our 62" diameter limit with your LimoEZ. We can work backwards from that. Limit tip speed to 800 fps. Tip travel in one rotation = 62" * Pi = 195" = 16.2 feet. 800 fps / 16.2 feet = 49.3 rps = 2957 RPM Thus you see that a 62" prop really wants to be run at 2950 RPM, which is right where I am with my 2.17 drive and 6400 engine RPM. If you have a 2.85 drive and a 2957 prop, your engine speed would be 8428. So if you are running a 10,000 RPM redline Renesis engine the 2.85 would be appropriate. Otherwise the 2.17 might be better, unless you put longer legs on your bird and use a larger diameter prop. You add more blades when you have excess HP to absorb. Or you can use larger chord blades. Pitch is inches of forward travel per rotation. So if you want to go 220 mph with your 2957 RPM prop: 220mph = 323fps = 3872 inches per second 3872ips / 49.3rps = 78.5" pitch My prop is pitched 68" and gives me a speed of 49.3rps * 68" = 3352ips = 279fps = 190 mph = 165 knots, my cruise speed almost exactly. Perry http://www.mickaircraft.com/duckt.htm ----- Original Message ----- Perry, I was planning on using a RD-1C with my 89 P Port. Any suggestion on a prop? Does increasing the number of blades achieve a similar affect as using a 74" prop? I need to go to prop 101. JoeBerki Limo EZ --------------070405030204040303050503 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit I assume you still might have our 62" diameter limit with your LimoEZ.
We can work backwards from that. Limit tip speed to 800 fps.
Tip travel in one rotation = 62" * Pi = 195" = 16.2 feet.
800 fps / 16.2 feet = 49.3 rps = 2957 RPM
Thus you see that a 62" prop really wants to be run at 2950 RPM, which is right where I am with my 2.17 drive and 6400 engine RPM.
If you have a 2.85 drive and a 2957 prop, your engine speed would be 8428.
So if you are running a 10,000 RPM redline Renesis engine the 2.85 would be appropriate. Otherwise the 2.17 might be better, unless you put longer legs on your bird and use a larger diameter prop.

You add more blades when you have excess HP to absorb. Or you can use larger chord blades.

Pitch is inches of forward travel per rotation. So if you want to go 220 mph with your 2957 RPM prop:
220mph = 323fps = 3872 inches per second
3872ips / 49.3rps = 78.5" pitch

My prop is pitched 68" and gives me a speed of 49.3rps * 68" = 3352ips = 279fps = 190 mph = 165 knots, my cruise speed almost exactly.

Perry
http://www.mickaircraft.com/duckt.htm

----- Original Message -----

Perry,

I was planning on using a RD-1C with my 89 P Port. Any suggestion on a prop? Does increasing the number of blades achieve a similar affect as using a 74" prop? I need to go to prop 101.

JoeBerki

Limo EZ

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