Pietenpol-List: tube drag

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Pietenpol-List: tube drag

Post by matronics »

Original Posted By: "Christian Bobka"
I was working in the garage and was thinking about the cost ofstreamlined struts and wondered what would be the horsepower penaltyfor going with round struts. So after about an hour looking throughmy Fluid Dynamics book, of which I haven't looked at in 10 years, Icalculated the drag. My assumptions were 100mph at standard pressureand temperature (half the battle was figuring out the density of air)of a 1" diameter tube and got about 0.15 horsepower per foot oflength. The coefficient of drag for a eliptical tube, which is closeto a streamlined tube, was about 1/3 of that.The sort-of Pietenpol-like aircraft that I'm working on has 25' oftube and would take almost 4 HP to push a round tube through the air.The streamlined tube would save about 2 or 3 horsepower.Just thought y'all would be interested and please don't hold me to thecalculations.Robert HainesMurphysboro, Illinois________________________________________________________________________________
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Re: Pietenpol-List: tube drag

Post by matronics »

Original Posted By: "Robert Haines"
Typical '20s era aircraft used a round tube with a piece of wood cut in awedge shape with the small side of the wedge triangle routed out to fit thetube. then a sock of fabric was made, turned inside out, slid over thepainted tube and varnished wood, shrunk, doped and painted and the assemblywas good to go. I even think the Spirit of St Louis was done this way. Itseems to be the inspiration for Mr. Pietenpol.That is the way I will do mine someday.Chris Bobka----- Original Message -----
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Pietenpol-List: tube drag

Post by matronics »

Original Posted By: Matt Dralle
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Pietenpol-List: tube drag

Post by matronics »

Original Posted By: "Robert Haines"
"Robert Haines" wrote:>I was working in the garage and was thinking about the cost>of streamlined struts>The streamlined tube would save about 2 or 3 horsepower.I did the same sort of thinking. Streamline tubing is expensive, and is more difficult than round tubing to fit at the ends. So... you wanna cheat? There is another alternative, but it isn't "real Pietenpol"... it's something the ultralight guys use. Slip-on plastic streamline tube fairing; see it at http://streamline.8k.comOne guy I know got a boost of 7-10 MPH after installing these on his Challenger. It is a lot more affordable than steel streamline tubing, simpler and easier to install than the taped-shaped-wood "old timey" method.Oscar ZunigaMedford, Oregonmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________
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Re: Pietenpol-List: tube drag

Post by matronics »

Original Posted By: "Warren D. Shoun"
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Re: Pietenpol-List: tube drag

Post by matronics »

Original Posted By: "Warren D. Shoun"
Your URL http://www.sky-tek/struts.htmlis missing ".com" so it should read http://www.sky-tek.com/struts.html towork.Cy Galley, TC - Chair, Emergency Aircraft Repair, OshkoshEditor, EAA Safety Programscgalley(at)qcbc.org or experimenter(at)eaa.orghttp://www.eaa.org for latest flying rulesAlways looking for articles for the Experimenter----- Original Message -----
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Re: Pietenpol-List: tube drag

Post by matronics »

Original Posted By: "Warren D. Shoun"
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Re: Pietenpol-List: tube drag

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Original Posted By: "John Hofmann"
Subject: Re: Pietenpol-List: tube dragIn a message dated 11/18/01 7:11:02 PM Pacific Standard Time, robertsjunk(at)hotmail.com writes:> I was working in the garage and was thinking about the cost of> streamlined struts and wondered what would be the horsepower penalty> for going with round struts. So after about an hour looking through> my Fluid Dynamics book, of which I haven't looked at in 10 years, I> calculated the drag. My assumptions were 100mph at standard pressure> and temperature (half the battle was figuring out the density of air)> of a 1" diameter tube and got about 0.15 horsepower per foot of> length. The coefficient of drag for a eliptical tube, which is close> to a streamlined tube, was about 1/3 of that.> > The sort-of Pietenpol-like aircraft that I'm working on has 25' of> tube and would take almost 4 HP to push a round tube through the air.> The streamlined tube would save about 2 or 3 horsepower.> > Just thought y'all would be interested and please don't hold me to the> calculations.> > Robert Haines> Murphysboro, Illinois> > > Robert,I used 1 1/4 dia x .049 wall round tubing and skip welded a steel V shaped trailing edge to it. 102 hours on the ship now without jury struts; works great. I got this idea from a Buckeye Pietenpol Newsletter years ago. Doug Bryant________________________________________________________________________________
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Re: Pietenpol-List: tube drag

Post by matronics »

Original Posted By: "Robert Haines"
For those not familiar: There was an AD issued a few years back requiringinspection/modification/replacement of Piper lift struts with cut threadstrut forks to the new rolled thread type of strut fork to a sealed strutand a bunch of mumbo jumbo. Consequently there are a ton of old lift strutsunusable in the massive Piper fleet but great for the Piet builder. Just cutoff the ends and voila, one has a perfect lift strut. J3, J4, J5, PA12, PA18struts will work the best. Remember these are junk in the Piper line so theyshould be available for next to nothing. I always seem to find someone witha pair of these around the hanger just collecting dust.I posted a link here for a pdf version of the AD if anyone cares. Justgetting my website back up for business and going to make a hopefullywelcome announcement to this list later in the day.http://www.johnnyskyrocket.com/liftstru ... 1_05.pdfmy $0.02-john-________________________________________________________________________________
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Re: Pietenpol-List: tube drag

Post by matronics »

Original Posted By: "John Hofmann"
John,Thats exactly how I got mine. Go into any of the old hangers that have roofrafters and look up. or in a back room somewhere. These are one of thosethings that when people take them off, they never throw away. They alwaysstash them somewhere.The Piet struts are very much shorter that the Piper etc. struts and when Icut off my ends , they were still black and oilly inside.walt----- Original Message -----
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Re: Pietenpol-List: tube drag

Post by matronics »

Original Posted By:> "John Hofmann"
Excellent Walt!I want to emphasize these are plentiful. I know I will feel more at easeloading a piece of proven steel in tension more than I would loading thatsame piece in aluminum. That is just my preference of course. This is justone way to save the builders, time, cost and piece mind. Even the bent onescan often be used, depending on the location of the dent or bend.TakeCare,-john->> John,> Thats exactly how I got mine. Go into any of the old hangers that haveroof> rafters and look up. or in a back room somewhere. These are one of those> things that when people take them off, they never throw away. They always> stash them somewhere.> The Piet struts are very much shorter that the Piper etc. struts and whenI> cut off my ends , they were still black and oilly inside.> walt> ----- Original Message -----
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Re: tube drag

Post by matronics »

Original Posted By: "Bill Church"
Subject: Re: tube drag In a message dated 11/18/01 7:11:02 PM Pacific Standard Time, robertsjunk(at)hotmail.comwrites: > I was working in the garage and was thinking about the cost of streamlined strutsand wondered what would be the horsepower penalty for going with round struts.So after about an hour looking through my Fluid Dynamics book, of whichI haven't looked at in 10 years, I calculated the drag. My assumptions were100mph at standard pressure and temperature (half the battle was figuring outthe density of air) of a 1" diameter tube and got about 0.15 horsepower perfoot of length. The coefficient of drag for a eliptical tube, which is close to a streamlined tube, was about 1/3 of that. The sort-of Pietenpol-like aircraftthat I'm working on has 25' of tube and would take almost 4 HP to push around tube through the air. The streamlined tube would save about 2 or 3 horsepower.Just thought y'all would be interested and please don't hold me to thecalculations. Robert Haines > Murphysboro, Illinois Robert, I used 1 1/4 dia x .049 wall round tubing and skip welded a steel V shapedtrailing edge to it. 102 hours on the ship now without jury struts; worksgreat. I got this idea from a Buckeye Pietenpol Newsletter years ago. Doug Bryant--------Chris TracySacramento, CAWestCoastPiet.comRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________
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> Re: tube drag

Post by matronics »

Original Posted By: "Bill Church"
> Subject: Re: tube drag>> In a message dated 11/18/01 7:11:02 PM Pacific Standard Time,> robertsjunk(at)hotmail.com writes:>> > I was working in the garage and was thinking about the cost of> streamlined struts and wondered what would be the horsepower penalty for> going with round struts. So after about an hour looking through my Fluid> Dynamics book, of which I haven't looked at in 10 years, I calculated the> drag. My assumptions were 100mph at standard pressure and temperature (half> the battle was figuring out the density of air) of a 1" diameter tube and> got about 0.15 horsepower per foot of length. The coefficient of drag for a> eliptical tube, which is close to a streamlined tube, was about 1/3 of> that. The sort-of Pietenpol-like aircraft that I'm working on has 25' of> tube and would take almost 4 HP to push a round tube through the air. The> streamlined tube would save about 2 or 3 horsepower. Just thought y'all> would be interested and please don't hold me to the calculations.>> Robert Haines > Murphysboro, Illinois>>> Robert, I used 1 1/4 dia x .049 wall round tubing and skip welded a steel V> shaped trailing edge to it. 102 hours on the ship now without jury struts;> works great. I got this idea from a Buckeye Pietenpol Newsletter years ago.>> Doug Bryant>> --------> Chris Tracy> Sacramento, CA> WestCoastPiet.com>>> Read this topic online here:>> http://forums.matronics.com/viewtopic.p ... 210841>>-- Ken Chambers512-796-1798________________________________________________________________________________
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