X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from nm9.bullet.mail.sp2.yahoo.com ([98.139.91.79] verified) by logan.com (CommuniGate Pro SMTP 5.4.6) with SMTP id 5645898 for flyrotary@lancaironline.net; Tue, 10 Jul 2012 14:20:51 -0400 Received-SPF: none receiver=logan.com; client-ip=98.139.91.79; envelope-from=ceengland@bellsouth.net Received: from [98.139.91.64] by nm9.bullet.mail.sp2.yahoo.com with NNFMP; 10 Jul 2012 18:20:17 -0000 Received: from [68.142.194.244] by tm4.bullet.mail.sp2.yahoo.com with NNFMP; 10 Jul 2012 18:20:17 -0000 Received: from [66.94.237.124] by t2.bullet.mud.yahoo.com with NNFMP; 10 Jul 2012 18:20:17 -0000 Received: from [127.0.0.1] by omp1029.access.mail.mud.yahoo.com with NNFMP; 10 Jul 2012 18:20:17 -0000 X-Yahoo-Newman-Id: 651215.76073.bm@omp1029.access.mail.mud.yahoo.com Received: (qmail 39833 invoked from network); 10 Jul 2012 18:20:17 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bellsouth.net; s=s1024; t=1341944417; bh=5kLfwl3FvfsZSEcGmSN5wN+uLGnyOVTfCSrg2rc7KEQ=; h=X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Message-ID:Date:From:User-Agent:MIME-Version:To:Subject:References:In-Reply-To:Content-Type; b=yFOD7VH7imMg3+ToiA5LQP1vIqgBiH3qbIRxhJRPKRlV3mYfCj03kK7WLLkl04TWIIKWaiZpBc0yXo1bT49pATe5ACnbAUnK8Prc2NNuODGlr1E9FzH8ufej47j8Oz1P0LMXtTH+dXgMR89gwOpnrZuBJC7kAy0TKx2W1p04F6M= X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: FjaauVQVM1ka4CHy4DcndzjrSyCOfIM81MWOkstPvBCqC7s OKl_QUjNAdu33.rfqp0eAMjEa_GXAGTPd2J.XdKaonZuW7wERFDoGl8Y4MwE wWE1JbaBf7XZ3m8fEcT2NVrOTdUF9OQLqKPp3d7CiEyIKxaJz_KSXog7Auhv H539hLpHw4Y4gfUB1rDnD5v8LxMmlzLIg.HUgnuFapedCboUd42d2KF8eBZn 8ejSvd1sTCpmWDCbvZbxkfqq1QgyRUQMrU1dPBjtIYyNbNLfC90tpr9kCAup VY6A5OS8Jm5ckZj1TQ2W.sujX15.INwZb25jzA7z2ONOzAYeW_F7lvnVd97r DmudFiNi52IwVxY3ns.84U4kGfz4MJyBjvc.FV4jhOgmpl339voDDmXTJLv9 VUTFkJUNJDj7fug_m5nzIeorifCC0KlcifBgnvznRQIvXPlhn3Uc19NAu9Q6 DpdztgPrZ4AiOVni01whUnLqrc3NmF5IkZY4fXKYeJSBv8KiMhONtl1c1sMs v1trbvPy_fc877FWZS6Hfaurr18TWg61quKg- X-Yahoo-SMTP: uXJ_6LOswBCr8InijhYErvjWlJuRkoKPGNeiuu7PA.5wcGoy Received: from [192.168.10.30] (ceengland@98.95.124.87 with plain) by smtp107.sbc.mail.mud.yahoo.com with SMTP; 10 Jul 2012 11:20:16 -0700 PDT Message-ID: <4FFC725F.3040705@bellsouth.net> Date: Tue, 10 Jul 2012 13:20:15 -0500 From: Charlie England User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1 MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: On the step References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------080504030608040309000703" This is a multi-part message in MIME format. --------------080504030608040309000703 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Here you go: http://www.vansaircraft.com/public/rv-7per.htm Van's numbers are: 75% cruise at 8k ft is 207 statute mph. This is with a constant speed prop, but even with a wood fixed pitch, he shouldn't lose more than 5 mph unless he has it pitched for climb (not much need for that with 200 hp...). If google's math is right, assuming 200 mph cruise that would be 173+ kts. Assuming 150 hp, .45 lbs/HP/Hr properly leaned fuel burn & 6 lbs per gallon fuel weight, that's ~11.25 gal per hour fuel burn (say 11.75 gph for sloppy and/or paranoid leaning practice). I bet he's burning a lot less than that, right? I bet that he's running at far less than full throttle at 8000 ft & turning closer to 2400 rpm than the rated 2700 required to get 75% power at that altitude. Charlie On 07/09/2012 10:38 PM, Bill Bradburry wrote: > > Hi Charlie, > > I don't have any idea what Van's performance numbers are?? Where > would I find those? > > Bill B > > ------------------------------------------------------------------------ > > *From:*Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] > *On Behalf Of *Charlie England > *Sent:* Monday, July 09, 2012 3:45 PM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] Re: On the step > > Hi Bill, > > There's something seriously outside the norm if he's only getting 150 > kts at 8k ft full throttle. Any properly built -7 will come very close > to Van's spec performance numbers. The fixed pitch prop would have > little effect on cruise, if pitched properly for the plane & HP. 160 > hp -7's with FP props can easily hit that cruise figure. > > Charlie > > > On 07/09/2012 02:02 PM, Bill Bradburry wrote: > > Brian, > > Getting "on the step" might get you at your terminal velocity/hp/rpm > equilibrium sooner, but no matter when, at some time it will all level > out at the equilibrium point. You might be able to dive and pick up > 9% more, but it will not hold and will eventually bleed off the same > point no matter how you got there. > > It seems true that you can judge the rotary hp by its rpm, but in the > case of the shallow dive, you are actually reducing the load on the > prop and the engine uses the hp not needed to pull the plane to > increase the prop rpm. When the load from the plane comes back, when > you level out, the rpm will drop back because the hp is now being used > to pull the plane as before. If this didn't work this way, you could > carry a plane with a 3 hp lawnmower engine up to 30K feet and drop it > out and the engine would be producing 10,000 hp by the time it got > down to sea level!! It would then level out and maintain mach 2!!! :>) > > My next door hangar neighbor has an RV-7 with a 200HP fixed pitch prop > and he is pretty consistently running 150 knots of true airspeed at 8K > feet. You could probably use him as a guide for performance on your > plane. At 8K feet he is at close to 75% power. Say 150 HP. > > B2 > > ------------------------------------------------------------------------ > > *From:*Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] > *On Behalf Of *bktrub@aol.com > *Sent:* Monday, July 09, 2012 12:43 PM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] On the step > > I commented on here recently about how I took a cross- country flight > to Walla Walla from Everett, Wa recently and was only seeing 140-150 > mph cruise at 11,500 feet. It got me to thinking- I was getting about > 6200 rpm on the engine which is 2175 at the prop. So, I'm a little > overpropped/ underpowered. > > So, there's the old chestnut about how you can get a few more knots > from an airplane in cruise if you go a little above your cruise > altitude and then descend to your cruise altitude, thereby getting "on > the step" . Some pilots swear by this, others dismiss it. I have a > theory- if I climb to a cruise altitude and stay at full throttle > while doing so, I will only get the engine to run up to a certain RPM > and therefore a certain hp will be achieved, and no more and so the > airplane will settle into an equilibrium at a certain speed- say at > whatever hp/speed - 140 mph at 6200 rpm- lt's say x hp. > > Now, If I were to descend to my cruise altitude in a shallow dive, I > will be acheiving a higher rpm and hence horsepower, say 6800 rpm and > horsepower will be x + 9%x for a hp of 109% of the hp achieved at 6200 > rpm, so I should be able to achieve and maintain a higher cruise > speed if I descend to my cruising altitude. ( I picked 9% arbitrarily > for the sake of argument) . > > Anyone want to shoot me down on this one? > > This is just an theory, If I want to go faster first I have to clean > up my drag. My cooling scoop is effective, but obviously draggy. And > It needs a flap on it. That's a project for this winter. > > Brian Trubee > --------------080504030608040309000703 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Here you go:
http://www.vansaircraft.com/public/rv-7per.htm

Van's numbers are: 75% cruise at 8k ft is 207 statute mph. This is with a constant speed prop, but even with a wood fixed pitch, he shouldn't lose more than 5 mph unless he has it pitched for climb (not much need for that with 200 hp...). If google's math is right, assuming 200 mph cruise that would be 173+ kts. Assuming 150 hp, .45 lbs/HP/Hr properly leaned fuel burn & 6 lbs per gallon fuel weight, that's ~11.25 gal per hour fuel burn (say 11.75 gph for sloppy and/or paranoid leaning practice). I bet he's burning a lot less than that, right?

I bet that he's running at far less than full throttle at 8000 ft & turning closer to 2400 rpm than the rated 2700 required to get 75% power at that altitude.

Charlie


On 07/09/2012 10:38 PM, Bill Bradburry wrote:

Hi Charlie,

 

I don’t have any idea what Van’s performance numbers are??  Where would I find those?

 

Bill B

 

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Charlie England
Sent: Monday, July 09, 2012 3:45 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: On the step

 

Hi Bill,

There's something seriously outside the norm if he's only getting 150 kts at 8k ft full throttle. Any properly built -7 will come very close to Van's spec performance numbers. The fixed pitch prop would have little effect on cruise, if pitched properly for the plane & HP. 160 hp -7's with FP props can easily hit that cruise figure.

Charlie


On 07/09/2012 02:02 PM, Bill Bradburry wrote:

Brian,

 

Getting “on the step” might get you at your terminal velocity/hp/rpm equilibrium sooner, but no matter when, at some time it will all level out at the equilibrium point.  You might be able to dive and pick up 9% more, but it will not hold and will eventually bleed off the same point no matter how you got there.

 

It seems true that you can judge the rotary hp by its rpm, but in the case of the shallow dive, you are actually reducing the load on the prop and the engine uses the hp not needed to pull the plane to increase the prop rpm.  When the load from the plane comes back, when you level out, the rpm will drop back because the hp is now being used to pull the plane as before.  If this didn’t work this way, you could carry a plane with a 3 hp lawnmower engine up to 30K feet and drop it out and the engine would be producing 10,000 hp by the time it got down to sea level!!  It would then level out and maintain mach 2!!!  :>)

 

My next door hangar neighbor has an RV-7 with a 200HP fixed pitch prop and he is pretty consistently running 150 knots of true airspeed at 8K feet.  You could probably use him as a guide for performance on your plane.  At 8K feet he is at close to 75% power.  Say 150 HP.

 

B2

 

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of bktrub@aol.com
Sent: Monday, July 09, 2012 12:43 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] On the step

 

I commented on here recently about how I took a cross- country flight to Walla Walla from Everett, Wa recently and was only seeing 140-150 mph cruise at 11,500 feet. It got me to thinking- I was getting about 6200 rpm on the engine which is 2175 at the prop. So, I'm a little overpropped/ underpowered.

 

So, there's the old chestnut about how you can get a few more knots from an airplane in cruise if you go a little above your cruise altitude and then descend to your cruise altitude, thereby getting "on the step" . Some pilots swear by this, others dismiss it. I have a theory- if I climb to a cruise altitude and stay at full throttle while doing so, I will only get the engine to run up to a certain RPM and therefore a certain hp will be achieved, and no more and so the airplane will settle into an equilibrium at a certain speed- say at whatever hp/speed - 140 mph at 6200 rpm- lt's say x hp.

 

Now, If I were to descend to my cruise altitude in a shallow dive, I will be acheiving a higher rpm and hence horsepower, say 6800 rpm and horsepower will be x + 9%x for a hp of 109% of the hp achieved at 6200 rpm, so I should be able to achieve and maintain a higher cruise  speed if I descend to my cruising altitude. ( I picked 9% arbitrarily for the sake of argument) .

 

Anyone want to shoot me down on this one?

 

This is just an theory, If I want to go faster first I have to clean up my drag. My cooling scoop is effective, but obviously draggy. And It needs a flap on it. That's a project for this winter.

 

Brian Trubee

 


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