X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from wproxy.gmail.com ([64.233.184.201] verified) by logan.com (CommuniGate Pro SMTP 5.0.4) with ESMTP id 889107 for flyrotary@lancaironline.net; Mon, 19 Dec 2005 19:15:13 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.233.184.201; envelope-from=wdleonard@gmail.com Received: by wproxy.gmail.com with SMTP id 71so1155609wra for ; Mon, 19 Dec 2005 16:14:28 -0800 (PST) DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; b=c1XYFRx2VWNpER3ns2U2YNreH4N0YA56CIYIn39Ub4aKFfte6T9UFOMD3aAjBVB7Yj0s5fWv4W4ZIOosUb7AZZVLTL1ilgf/7UVWtihb5x/o6V4d1O+49B/nJLy7UeGgxI7deqfQSyQdEDGz+vY0qcJ3DgsFKJeX6z2D7TbtDv0= Received: by 10.65.189.12 with SMTP id r12mr4906388qbp; Mon, 19 Dec 2005 16:14:28 -0800 (PST) Received: by 10.64.151.9 with HTTP; Mon, 19 Dec 2005 16:14:27 -0800 (PST) Message-ID: <1c23473f0512191614k3a84d523xf807e0d4ed90aeef@mail.gmail.com> Date: Mon, 19 Dec 2005 16:14:27 -0800 From: David Leonard To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: Props In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_61_21021668.1135037667993" References: ------=_Part_61_21021668.1135037667993 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Bully, if there is nothing otherwise wrong with your engine, that will be plenty for flight. I predict you will get an additional 500 RPM on take of= f roll and even more than that in flight. When I was flying normally aspirated I got only 4600 on take off roll (4200 static) and that was plent= y to beat all the cessnas. If you are doing that at 50" you will be making a lot more power than I was. Just how big is this MONSTER prop? The formula I have for tip speed (ft/sec) is: Prop RPM * Diameter * 0.00436 This must be an approximation because it doesn't take into account aircraft speed, which properly should be a factor. Dave Leonard On 12/19/05, Bulent Aliev wrote: > > Thanks Dave. it makes me feel better now that I know I was wrong. My > problem now is: I can spin my "monster prop" (static) up-to 4000RPM and 5= 0" > MP I don't think I can get much more in motion and may not get enough rpm > for flight. I'll see first how much difference it will make on fast taxi. > John Slade also will bring his Performance prop one day, so we can compar= e > them. BTW the prop tip speed formula given to me was: > Prop D" x 3.1416 x RPM divided by 720 > Buly > > On Dec 19, 2005, at 6:06 PM, David Leonard wrote: > > Oh, BTW Bully. You will also note that at 6000 RPM the prop is doing > 2750 which a lot of certified props will turn, even if 74"long. > > Also, short prop are not necessarily less efficient, its just that the > speed of peak efficiency is shifted to a higher airspeed, and probably th= at > peak is a little more narrow. > > Dave Leonard > > > On 12/19/05, Buly wrote: > > > > Yesterday somebody gave me the formulas to calculate the prop tip > > speed. I did some calculations and looks like us with the 2.17 > > redrives are kind of painted in the corner. Hope I'm wrong, but if I > > want to keep the tips from going supersonic, I have to cut down the > > prop to 64" or keep the engine below 5500 RPM. The choice is either > > inefficient prop and adequate power, or efficient long prop and not > > getting all the power from the engine? Am I wrong? > > Buly > > atlasyts@bellsouth.net > > > > > > > > > > -- > > Homepage: http://www.flyrotary.com/ > > Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/ > > > > > > -- > Dave Leonard > Turbo Rotary RV-6 N4VY > http://members.aol.com/_ht_a/rotaryroster/index.html > http://members.aol.com/_ht_a/vp4skydoc/index.html > > > Bulent Aliev > atlasyts@bellsouth.net > http://home.bellsouth.net/p/s/community.dll?ep=3D16&ext=3D1&groupid=3D164= 323&ck=3D > > > > -- Dave Leonard Turbo Rotary RV-6 N4VY http://members.aol.com/_ht_a/rotaryroster/index.html http://members.aol.com/_ht_a/vp4skydoc/index.html ------=_Part_61_21021668.1135037667993 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline
Bully, if there is nothing otherwise wrong with your engine, that will= be plenty for flight.  I predict you will get an additional 500 RPM o= n take off roll and even more than that in flight.  When I was flying = normally aspirated I got only 4600 on take off roll (4200 static) and = that was plenty to beat all the cessnas.  If you are doing that at 50&= quot; you will be making a lot more power than I was.
 
Just how big is this MONSTER prop?
 
The formula I have for tip speed (ft/sec) is:
 
Prop RPM * Diameter * 0.00436
 
This must be an approximation because it doesn't take into account air= craft speed, which properly should be a factor.
 
Dave Leonard

 
On 12/19/05, Bulent Aliev <atlasyts@be= llsouth.net> wrote:
Thanks Dave. it makes me feel be= tter now that I know I was wrong. My problem now is: I can spin my "mo= nster prop" (static) up-to 4000RPM and 50" MP I don't think I can= get much more in motion and may not get enough rpm for flight. I'll see fi= rst how much difference it will make on fast taxi. John Slade also will bri= ng his Performance prop one day, so we can compare them.=20
BTW the prop tip speed formula given to me was:
Prop D" x 3.1416 x RPM divided by 720
Buly

On Dec 19, 2005, at 6:06 PM, David Leonard wrote:

Oh, BTW Bully.  You will also note that at 6000 RPM the prop is d= oing 2750 which a lot of certified props will turn, even if 74"long.
 
Also, short prop are not necessarily less efficient, its just that the= speed of peak efficiency is shifted to a higher airspeed, and probably tha= t peak is a little more narrow.
 
Dave Leonard

 
On 12/19/05, Buly <atlasyts@bellsouth.= net > wrote:=20
Yesterday somebody gave me the f= ormulas to calculate the prop tip
speed. I did some calculations and loo= ks like us with the=20 2.17
redrives are kind of painted in the corner. Hope I'm wrong, but if = I
want to keep the tips from going supersonic, I have to cut down theprop to 64" or keep the engine below 5500 RPM. The choice is either= =20
inefficient prop and adequate power, or efficient long prop and not
= getting all the power from the engine? Am I wrong?
Buly
atlasyts@bellsouth.net




--
Homepage:  http://www.flyrotary.com/
Archiv= e and UnSub:  =20 http://mail.lanc= aironline.net/lists/flyrotary/



--
Dave Leonard
Turbo Rotary RV-6 N4VY
http://members.aol.com/_ht_a/rot= aryroster/index.html
http:= //members.aol.com/_ht_a/vp4skydoc/index.html




--
Dave Leon= ard
Turbo Rotary RV-6 N4VY
http:/= /members.aol.com/_ht_a/rotaryroster/index.html
http://members.aol.com/_ht_a/vp4sk= ydoc/index.html =20 ------=_Part_61_21021668.1135037667993--