X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from sccrmhc12.comcast.net ([204.127.202.56] verified) by logan.com (CommuniGate Pro SMTP 4.3c5) with ESMTP id 913525 for flyrotary@lancaironline.net; Sun, 24 Apr 2005 22:05:43 -0400 Received-SPF: none receiver=logan.com; client-ip=204.127.202.56; envelope-from=kenpowell@comcast.net Received: from 204.127.205.142 (sccrwbc58.attbi.com[204.127.205.158]) by comcast.net (sccrmhc12) with SMTP id <20050425020453012004i0ope>; Mon, 25 Apr 2005 02:04:53 +0000 Received: from [68.51.45.41] by 204.127.205.142; Mon, 25 Apr 2005 02:04:51 +0000 From: kenpowell@comcast.net To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] Re: Upper Airspeed Data on Rotary-Powered Van's RV Date: Mon, 25 Apr 2005 02:04:51 +0000 Message-Id: <042520050204.27610.426C50430005D22300006BDA220588636004040A99019F020A05@comcast.net> X-Mailer: AT&T Message Center Version 1 (Dec 17 2004) X-Authenticated-Sender: a2VucG93ZWxsQGNvbWNhc3QubmV0 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="NextPart_Webmail_9m3u9jl4l_27610_1114394691_0" --NextPart_Webmail_9m3u9jl4l_27610_1114394691_0 Content-Type: text/plain Content-Transfer-Encoding: 8bit Hi Bernie, I thought that you were a Mechanical Engineer; the talents on the list never ceases to amaze me. Thanks for the additional info; this is the first time that this computer programmer has heard of Von Karmin vortices. If you ask me about these in a week or so I will probably say "huh???". But an interesting look into flutter. Ken Powell Bryant, Arkansas 501-847-4721 -------------- Original message -------------- > > > > Hi Dave (and welcome John), > I agree that this (TAS) is really strange and not intuitive. But consider the > source - Van himself!!! When I read this in RVator I had doubts but I gotta go > with John on this unless we hear from another impeccable source to the contray. > TAS it is!!!! Call Van if you need more info; I doubt any of us (do we have any > aeronautical engineers on the list? I know we have every other flavor of > engineer here!) have the knowledge to debate this with Van. > -- > Ken Powell > Bryant, Arkansas > 501-847-4721 > ------------------------------------ > > Well yes we have an engineer with an aero degree, me; but do not proclaim to be > an expert on flutter. I spoke to Ken Krueger at length on this subject. First > ,Van does not have any flutter expertise on his staff and hires his work out to > a flutter engineer here in Vero Beach. > > I would have bet it is a function of IAS because the driving forces are a > function of dynamic pressure, but the exciting force may in fact be a function > of TAS. The thing that excites flutter is the shedding of Von Karmin vortices > and you can see how there frequency would be more a function of TAS and their > strength is related to the IAS. On the other hand, it does not take a very large > hammer to destroy a surface if you hit it as its natural frequency. Now you are > basically up to speed with Ken and myself. When Ken looks at the "experts" > analysis , the exciting frequency is with TAS. Now saying this, you have to > believe that Van put a large "kitty" on the number to take care of the unbalance > surfaces and other variations among the homebuilt kits. > > Look at the speeds that Tracy Saylor turns in his RV6 and Dave Anders in his > RV4 to know that there is some degree of margin. I would test the water gingerly > with stick bumping as I increased speed at a safe altitude and be alert with an > outlet plan such as power off and climb to kill the flutter. > > I don't know, but I think it is streching it some to believe that a naturally > aspirated RV is going to exceed 200 with a reasonable fuel burn, but some of > the high time rotary RV pilots should comment on that subject. > > Bernie, 20 hours of 40 flyoff, have flown 7 days straight , tough living in S > Fla > > >> Homepage: http://www.flyrotary.com/ > >> Archive: http://lancaironline.net/lists/flyrotary/List.html --NextPart_Webmail_9m3u9jl4l_27610_1114394691_0 Content-Type: text/html Content-Transfer-Encoding: 8bit
Hi Bernie,
I thought that you were a Mechanical Engineer; the talents on the list never ceases to amaze me.  Thanks for the additional info; this is the first time that this computer programmer has heard of Von Karmin vortices.  If you ask me about these in a week or so I will probably say  "huh???".  But an interesting look into flutter.

Ken Powell
Bryant, Arkansas
501-847-4721
 
-------------- Original message --------------

>
>
>
> Hi Dave (and welcome John),
> I agree that this (TAS) is really strange and not intuitive. But consider the
> source - Van himself!!! When I read this in RVator I had doubts but I gotta go
> with John on this unless we hear from another impeccable source to the contray.
> TAS it is!!!! Call Van if you need more info; I doubt any of us (do we have any
> aeronautical engineers on the list? I know we have every other flavor of
> engineer here!) have the knowledge to debate this with Van.
> --
> Ken Powell
> Bryant, Arkansas
> 501-847-4721
> ------------------------------------
>
> Well yes we have an engineer with an aero degree, me; but do not proclaim to be
> an expert on flutter. I spoke to Ken Krueger at length on this subject. First
> ,Van does not have any flutter expertise on his staff and hires his work out to
> a flutter engineer here in Vero Beach.
>
> I would have bet it is a function of IAS because the driving forces are a
> function of dynamic pressure, but the exciting force may in fact be a function
> of TAS. The thing that excites flutter is the shedding of Von Karmin vortices
> and you can see how there frequency would be more a function of TAS and their
> strength is related to the IAS. On the other hand, it does not take a very large
> hammer to destroy a surface if you hit it as its natural frequency. Now you are
> basically up to speed with Ken and myself. When Ken looks at the "experts"
> analysis , the exciting frequency is with TAS. Now saying this, you have to
> believe that Van put a large "kitty" on the number to take care of the unbalance
> surfaces and other variations among the homebuilt kits.
>
> Look at the speeds that Tracy Saylor turns in his RV6 and Dave Anders in his
> RV4 to know that there is some degree of margin. I would test the water gingerly
> with stick bumping as I increased speed at a safe altitude and be alert with an
> outlet plan such as power off and climb to kill the flutter.
>
> I don't know, but I think it is streching it some to believe that a naturally
> aspirated RV is going to exceed 200 with a reasonable fuel burn, but some of
> the high time rotary RV pilots should comment on that subject.
>
> Bernie, 20 hours of 40 flyoff, have flown 7 days straight , tough living in S
> Fla
>
> >> Homepage: http://www.flyrotary.com/
> >> Archive: http://lancaironline.net/lists/flyrotary/List.html
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