X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imo-m25.mx.aol.com ([64.12.137.6] verified) by logan.com (CommuniGate Pro SMTP 5.1.10) with ESMTP id 2190431 for flyrotary@lancaironline.net; Fri, 20 Jul 2007 22:04:02 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.6; envelope-from=Lehanover@aol.com Received: from Lehanover@aol.com by imo-m25.mx.aol.com (mail_out_v38_r9.2.) id q.d0e.edbab15 (39332) for ; Fri, 20 Jul 2007 22:03:16 -0400 (EDT) From: Lehanover@aol.com Message-ID: Date: Fri, 20 Jul 2007 22:03:16 EDT Subject: Re: [FlyRotary] FW: [FlyRotary] Re: Thrust measure. To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1184983396" X-Mailer: 9.0 Security Edition for Windows sub 5366 X-Spam-Flag: NO -------------------------------1184983396 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en In a message dated 7/20/2007 7:26:24 P.M. Eastern Daylight Time, =20 Panzera@Experimental-Aviation.com writes: =20 From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On=20 Behalf Of Lehanover@aol.com Sent: Thursday, July 19, 2007 11:21 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Thrust measure. =20 In a message dated 7/19/2007 9:22:55 P.M. Eastern Daylight Time, =20 Panzera@Experimental-Aviation.com writes: With all due respect, what does measuring static thrust do for us?=20 Pat =20 Just guessing here but I suspect that a propeller with huge static thrust=20 might be better for the crop duster or bush plane than little pencil thin h= igh=20 speed prop from a formula one plane with little static thrust. More static =20 thrust comes from disc area just like the helicopter blades.=20 =20 Look at an airboat prop. 4 big blades. Wide chords. Large diameter. Works=20 with much turbulence in the inflow. Takes a fully loaded boat off the grass= =20 from a standstill, and right up to 80 MPH. =20 =20 My ideas may not be the complete list of information that could be=20 recovered. Mr Lipps would know much more. Perhaps you could get Mr Lipps to= comment?=20 Paul was it? I enjoyed his talk at Jean this year. Thank you for that effo= rt.=20 My pleasure.=20 I just did a key-word search through our current =E2=80=9CAll Paul Lipps= =E2=80=9D issue of=20 CONTACT! Magazine, for the word =E2=80=9Cthrust=E2=80=9D.=20 _www.ContactMagazine.com/backissu.html_=20 (http://www.contactmagazine.com/backissu.html) =20 Here=E2=80=99s one short paragraph where Paul mentions static thrust. All o= ther=20 mentions (and formulas) of thrust are related to dynamic thrust.=20 SINGLE BLADE MYTH=20 One of the myths that has been propagated in the aviation community, to the= =20 point that it is =E2=80=9Cgospel=E2=80=9D, is that the most efficient prop=20= is a single=20 blade; all higher number of blades falling further and further short of thi= s=20 paragon. Did you ever consider that a single-blade prop, developing thrust=20= on only=20 one side of the plane as it revolves, would cause the engine to cone=20 violently in its mounts as it is twisted by the prop? The European=E2=80= =99s latest=20 turbo-prop transport, the A400-M, has eight-blade props! The Boeing MD-90= 0=20 helicopter has a five-blade rotor. A popular regional turbo-prop airliner h= as a=20 five-blade prop. Hasn=E2=80=99t anybody filled these plane-makers in on the= errors of=20 their ways? In a recent edition of Kitplanes, the author of an article on p= rops=20 uttered the same fallacy. He maintained that multiple blades interfere with= =20 each other. When I pointed out to him that at 200 mph and 2800 RPM, the bla= des=20 on my three-blade prop follow three distinct helical paths through the air,= =20 and each blade is 25=E2=80=9D ahead of the previous blade at the same point= of=20 rotation, he rather lamely explained that in static conditions interference= occurs.=20 STATIC? Who uses static thrust? Airplanes are meant to fly, not pull=20 tree-stumps! I know from several conversations with Paul that he cares very little about= =20 static thrust. =20 He designs high speed props for fast home builts and racing planes. None of= =20 them have much in the way of static thrust. Propeller thrust might be useful in designing propellers.=20 At a gathering we had some time back, we had two nearly identical Corvair=20 engines running on separate test stands. They had completely different prop= s on=20 them, one made for a Pietenpol, the other for a single place Sonerai. They=20 both spooled up nicely to 2700 RPM. The Sonerai prop made a lot of wind for= =20 sure. The Piet prop made so much wind one couldn=E2=80=99t hardly stand or=20= breathe=20 behind it.=20 Here=E2=80=99s a shot of me, behind my test rig, running the Sonerai prop a= t full =20 tilt.=20 _http://www.experimental-aviation.com/Corvair/Images/WCCC/Event/TuftTest.jpg= _=20 (http://www.experimental-aviation.com/Corvair/Images/WCCC/Event/TuftTest.jpg= )=20 =20 If we had thrust measuring equipment I=E2=80=99m certain it would show us t= hat the=20 other engine/prop combination was easily making 2x the static thrust I was=20= =20 making.=20 Big picture, what does that really prove?=20 If you start the test with all of the questions answered, it is of little =20 value. If you have a pile of props you have borrowed, trying to find one for the=20 Pietenpol, The ones with the highest static thrust would be the place to st= art.=20 The Pietenpol is a big load to get rolling. When you are lined up and add=20 the power, is that static thrust or dynamic thrust?=20 When the Ag Cat shudders in the top of a turn with 1,200 pounds in the=20 hopper, do we need the little pencil thin high speed prop or the 12' Hamilt= on=20 standard 4 bladed with the huge static thrust?=20 =20 Could I bolt the Pietenpol prop to the Sonerai and expect 2x thrust at=20 altitude? No way. I=E2=80=99d probably climb like crazy but max out at 110=20= mph.=20 Yes that is correct. But you know that. The sum total of all you know from=20 years of exposure provides that to you. What if you didn't know that? What does it tell us about the engines? If we could measure HP we could be=20 sure that they were making the same power... but what does these static thr= ust=20 measurements tell us about HP output?=20 Very little. If both engine turn the same prop the same RPM, I suggest that= =20 they have the same HP. We did swap props however. My friend ran my Sonerai prop on his engine and=20 got the same RPM. I didn=E2=80=99t put his prop on my engine however. But f= or me, his=20 ability to swing my prop on his engine at the same static RPM tells me that= =20 the engines were making identical power. Thrust told us nothing.=20 It is hard to imagine a prop dyno not recovering thrust information.=20 A prop dyno as opposed to a water brake? =20 In this case the dyno is for measuring the engine power by having a=20 propeller absorb the output of the engine, just as a water brake would on a= n engine=20 dyno.=20 I=E2=80=99m having difficulty seeing the need for knowing static thrust at=20= all, that=E2=80=99 s why I asked the question in the first place.=20 So if it=E2=80=99s hard for you to imagine a prop dyno not giving static th= rust=20 info, please tell me what one can gain from knowing this information?=20 For experiencing propeller stall.=20 Ok... I=E2=80=99ve seen countless little red biplanes hang from their prop=20= at=20 airshows; certainly the prop is =E2=80=9Cstalled=E2=80=9D, and knowing that= the engine/prop=20 combination can produce thrust to counter the gross weight in order to allo= w the=20 plane to hover is useful information to this small group of pilots. But how= =20 many of us really need that info?=20 Well, those props are actually not stalled at all. Props stall just like=20 wings. The angle of attack is too high and the flow separates from the uppe= r=20 surface. Much lift (thrust in this case) is lost, and the engine is unloade= d to=20 some extent, and gains RPM as the load is lost. The propeller will remain=20 stalled until power is reduced, and or aircraft speed is increased. The ang= le of=20 attack of a fixed pitch propeller is a function of relative wind through th= e=20 disc. So higher speed of inflow may un-stall the blade and, or, reducing=20 propeller RPM may un-stall the blade. The slower the inflow (low static thr= ust?)=20 and the higher the pitch, the more likely the stall may occur. It feels lik= e=20 a slipping clutch and has caught many pilots cold. It is counter intuitive =20 to reduce power on take off and some people will just not do it, and find =20 themselves landing again with the engine howling madly. =20 When you build one of those planes that can hover, you really do need to=20 know how much static thrust your prop will produce. It has to be some perce= ntage=20 more than the full gross weight of the plane. When you see one accelerate=20 straight up out of a hover, the static thrust must be way more than the pla= nes=20 weight. =20 For comparing one prop to another. =20 Yes, you can compare one to another for a given situation, that being makin= g=20 wind while not moving. But that does that really tell us???=20 Say for example you have XYZ prop installed in a plane you have countless=20 hours in. You measure the static thrust at 350 lbs at 2250 prop RPM. Now y= ou=20 install an ABC prop that your buddy says should work better for you and you= =20 get 280 lbs at 2250... or you get 385 lbs at 2340 RPM. What do we now kno= w=20 about prop ABC? Is it better or worse than prop XYZ? Bear in mind, we know=20 everything there is to already know about XYZ, but what have we learned abo= ut ABC=20 now that we know what each prop produces in the matter of thrust? =20 In one case you have the same data point from the two props. In the second=20 case only one. If the reason for the test is static thrust, the XYZ is =20 "better". So for accelerating from stopped on a short runway, Or a stall re= covery=20 XYZ is the winner.=20 =20 Lately for making movies in a side view of blade flexing in single rotor =20 installations.=20 Ah... yes, running a prop on the ground can tell you a lot of things. That= =E2=80=99s=20 why I have such a rig. =20 But measuring thrust had no part of the revelations from said prop in the=20 video. =20 Pat There is of course no such thing as the static in static thrust. The low=20 pressure area in front of the prop produces flow through the disc. One reas= on=20 the larger disc (bigger diameter) produces more thrust. Larger diameter has= =20 more mass moving through the disc. Props designed for very high speeds trade= =20 high velocity of mass for lower velocity and greater mass. =20 =20 In this case the device to measure thrust was just part of the engine dyno=20 display that was proposed as a trailer installation for running a rotary at= =20 Sun&Fun and other venues. It was not the sole purpose of the engine stand. =20 Lynn E. Hanover=20 ************************************** Get a sneak peek of the all-new AOL a= t=20 http://discover.aol.com/memed/aolcom30tour -------------------------------1184983396 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en
In a message dated 7/20/2007 7:26:24 P.M. Eastern Daylight Time,=20 Panzera@Experimental-Aviation.com writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>

From:On Behalf Of=20 Lehanover@aol.com
Sent: Thursday, July 19, 2007 11:21= =20 PM
To: Rotary motors in= =20 aircraft
Subject: [FlyR= otary]=20 Re: Thrust measure.

 

In a message d= ated=20 7/19/2007 9:22:55 P.M. Eastern Daylight Time,=20 Panzera@Experimental-Aviation.com writes:

With all due=20 respect, what does measuring static thrust do for=20 us?

Pat

 
Just guessing here but I suspect that a propeller with huge sta= tic=20 thrust might be better for the crop duster or bush plane than little pencil=20= thin=20 high speed prop from a formula one plane with little static thrust. More sta= tic=20 thrust comes from disc area just like the helicopter blades.
 
Look at an airboat prop. 4 big blades. Wide chords. Large diame= ter.=20 Works with much turbulence in the inflow. Takes a fully loaded boat off the=20 grass from a standstill, and right up to 80 MPH.  
 
 

My ideas may n= ot be=20 the complete list of information that could be recovered. Mr Lipps would k= now=20 much more. Perhaps you could get Mr Lipps to comment? Paul was it? I enjoy= ed=20 his talk at Jean this year. Thank you for that=20 effort.

 My=20 pleasure.

 

I just did a ke= y-word=20 search through our current =E2=80=9CAll Paul Lipps=E2=80=9D issue of CONTA= CT! Magazine, for=20 the word =E2=80=9Cthrust=E2=80=9D.

www.ContactMagazine.= com/backissu.html

 Here=E2=80=99s=20= one short=20 paragraph where Paul mentions static thrust. All other mentions (and formu= las)=20 of thrust are related to dynamic thrust.

 

SINGLE=20 BLADE MYTH

<= SPAN=20 style=3D"mso-arabic-font-family: Arial; mso-cyrillic-font-family: Arial; m= so-default-font-family: Arial; mso-greek-font-family: Arial; mso-hebrew-font= -family: Arial; mso-latin-font-family: Arial; mso-latinext-font-family: Aria= l">= One of the=20 myths that has been propagated in the aviation community, to the point tha= t it=20 is =E2=80=9Cgospel=E2=80=9D, is that the most efficient prop is a single b= lade; all higher=20 number of blades falling further and further short of this paragon. Did yo= u=20 ever consider that a single-blade prop, developing thrust on only one side= of=20 the plane as it revolves, would cause the engine to cone violently in its=20 mounts as it is twisted by the prop? The European=E2=80=99s latest turbo-p= rop=20 transport, the A400-M, has eight-blade=20 props!=20 The Boeing MD-900 helicopter has a five-blade rotor. A popular regional=20 turbo-prop airliner has a five-blade prop. Hasn=E2=80=99t anybody filled t= hese=20 plane-makers in on the errors of their ways? In a recent edition of Kitpla= nes,=20 the author of an article on props uttered the same fallacy. He maintained=20= that=20 multiple blades interfere with each other. When I pointed out to him that=20= at=20 200 mph and 2800 RPM, the blades on my three-blade prop follow three disti= nct=20 helical paths through the air, and each blade is 25=E2=80=9D ahead of the=20= previous=20 blade at the same point of rotation, he rather lamely explained that in st= atic=20 conditions interference occurs. STATIC? Who uses static thrust? Airplanes=20= are=20 meant to fly, not pull tree-stumps!=

 <= /FONT>I know from sev= eral=20 conversations with Paul that he cares very little about static thrust.=20

He designs high speed props for fast home builts and racing pla= nes.=20 None of them have much in the way of static thrust.

 

 <= /FONT>Propeller thru= st=20 might be useful in designing propellers.

At a gathering=20= we had=20 some time back, we had two nearly identical Corvair engines running on=20 separate test stands. They had completely different props on them, one mad= e=20 for a Pietenpol, the other for a single place Sonerai. They both spooled u= p=20 nicely to 2700 RPM. The Sonerai prop made a lot of wind for sure. The Piet= =20 prop made so much wind one couldn=E2=80=99t hardly stand or breathe behind= =20 it.

 Here=E2=80=99s=20= a shot of me,=20 behind my test rig, running the Sonerai prop at full=20 tilt.

http://www.experimental-aviation.com/Corvair/Images/WCCC/Event/Tu= ftTest.jpg

If we had thrus= t=20 measuring equipment I=E2=80=99m certain it would show us that the other en= gine/prop=20 combination was easily making 2x the static thrust I was=20 making.

Big picture, wh= at=20 does that really prove?

If you start the test with all of the ques= tions=20 answered, it is of little=20 value.

If you have a pile of props you have borro= wed,=20 trying to find one for the Pietenpol, The ones with the highest static thrus= t=20 would be the place to start. The Pietenpol is a big load to get rolling. Whe= n=20 you are lined up and add the power, is that static thrust or dynamic thrust?= =20
When the Ag Cat shudders in the top of a turn with 1,200 pounds= in=20 the hopper, do we need the little pencil thin high speed prop or the 12'=20 Hamilton standard 4 bladed with the huge static thrust?
 
Could I bolt the=20 Pietenpol prop to the Sonerai and expect 2x thrust at altitude? No way. I= =E2=80=99d=20 probably climb like crazy but max out at 110 mph.
 
Yes that is corre= ct.=20 But you know that. The sum total of all you know from years of exposure prov= ides=20 that to you. What if you didn't know that?

 

What does it te= ll us=20 about the engines? If we could measure HP we could be sure that they were=20 making the same power... but what does these static thrust measurements te= ll=20 us about HP output?

Very little. If both engine turn the same prop the same RPM, I=20 suggest that they have the same HP.

We did swap props= =20 however. My friend ran my Sonerai prop on his engine and got the same RPM. I= =20 didn=E2=80=99t put his prop on my engine however. But for me, his ability to= swing my=20 prop on his engine at the same static RPM tells me that the engines were mak= ing=20 identical power. Thrust told us nothing.

 It is hard to imagine a prop dyno= not=20 recovering thrust information.

A prop dyno as=20 opposed to a water brake? 

In this case the dyno is for measuring the= engine=20 power by having a propeller absorb the output of the engine, just as a water= =20 brake would on an engine dyno.

I=E2=80=99m hav= ing difficulty=20 seeing the need for knowing static thrust at all, that=E2=80=99s why I ask= ed the=20 question in the first place.

So if it=E2=80= =99s hard for=20 you to imagine a prop dyno not giving static thrust info, please tell me w= hat=20 one can gain from knowing this information?

  For experiencing propeller=20 stall.

 Ok... I=E2=80= =99ve seen=20 countless little red biplanes hang from their prop at airshows; certainly=20= the=20 prop is =E2=80=9Cstalled=E2=80=9D, and knowing that the engine/prop combin= ation can produce=20 thrust to counter the gross weight in order to allow the plane to hover is= =20 useful information to this small group of pilots. But how many of us reall= y=20 need that info?

Well, those props are actually not stalled at all. Props stall=20= just=20 like wings. The angle of attack is too high and the flow separates from= the=20 upper surface. Much lift (thrust in this case) is lost, and the engine is=20 unloaded to some extent, and gains RPM as the load is lost. The propeller wi= ll=20 remain stalled until power is reduced, and or aircraft speed is increased. T= he=20 angle of attack of a fixed pitch propeller is a function of relative wind=20 through the disc. So higher speed of inflow may un-stall the blade and,= or,=20 reducing propeller RPM may un-stall the blade. The slower the inflow (low st= atic=20 thrust?) and the higher the pitch, the more likely the stall may occur. It f= eels=20 like a slipping clutch and has caught many pilots cold. It is counter intuit= ive=20 to reduce power on take off and some people will just not do it, and find=20 themselves landing again with the engine howling madly.=20     
 
When you build one of those planes that can hover, you really d= o=20 need to know how much static thrust your prop will produce. It has to be som= e=20 percentage more than the full gross weight of the plane. When you see one=20 accelerate straight up out of a hover, the static thrust must be way more th= an=20 the planes weight.  

 For comparing one prop to another.=20

Yes, you can co= mpare=20 one to another for a given situation, that being making wind while not mov= ing.=20 But that does that really tell us???

Say for example= you=20 have XYZ prop installed in a plane you have countless hours in. You measur= e=20 the static thrust at 350 lbs at 2250 prop RPM.  Now you install an ABC prop that= your=20 buddy says should work better for you and you get 280 lbs at 2250... or yo= u=20 get 385 lbs at 2340 RPM.  Wh= at do=20 we now know about prop ABC? Is it better or worse than prop XYZ? Bear in  mind, we know everything there i= s to=20 already know about XYZ, but what have we learned about ABC now that we kno= w=20 what each prop produces in the matter of thrust?

 
In one case you have the same data point from the two props. In= the=20 second case only one. If the reason for the test is static thrust, the XYZ i= s=20 "better". So for accelerating from stopped on a short runway, Or a stall=20 recovery XYZ is the winner.
 
Lately for makin= g=20 movies in a side view of blade flexing in single rotor=20 installations.

Ah... yes, runn= ing a=20 prop on the ground can tell you a lot of things. That=E2=80=99s why I have= such a rig.=20

But measuring t= hrust=20 had no part of the revelations from said prop in the video.=20

Pat

There is of course no such thing as the static in static thrust= .=20 The low pressure area in front of the prop produces flow through the disc. O= ne=20 reason the larger disc (bigger diameter) produces more thrust. Larger diamet= er=20 has more mass moving through the disc. Props designed for very high speeds t= rade=20 high velocity of mass for lower velocity and greater mass.  
 
In this case the device to measure thrust was just part of the=20 engine dyno display that was proposed as a trailer installation for running=20= a=20 rotary at Sun&Fun and other venues. It was not the sole purpose of the=20 engine stand.
 

L= ynn E.=20 Hanover

 



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