Original Posted By: "Jack Phillips"
Recently there have been a couple of questions raised regarding the suitabilityof VW engines in Pietenpol aircraft. Following is an article written by Pietenpolbuilder Brian Kenney, and published in the BPA newsletter in 1996. Foodfor thought.Why a VW "Beetle" engine is not a good choice in a Pietenpol!A Volkswagen "Bug" engine and its derivatives can produce enough horsepowerto fly a Pietenpol Air Camper. This alone is not enough of a reason to selectit as a Pietenpol engine. This is why:The efficiency of a propeller (irrespective of how well it is designed)is a functionof the difference between the speed of the airplane and the speed of thepropeller wash. As the speed of the prop wash approaches the speed of the airplane,the propeller approaches 100% of theoretical efficiency. At the same time,thrust is caused by the propeller throwing air backwards. The faster the air,the more the thrust. As the air speed approaches the speed of the airplanethe thrust goes to zero! At zero forward speed the thrust is maximum.Put these two together and you see you can't have both at once. If the airplaneis not moving it has a lot of thrust, its efficiency is zero--it is doing nowork. As the airplane accelerates, the work (force times distance) and the efficiencyincreases but the thrust decreases. In the case of a zero drag airplanethe airplane can accelerate until it reaches the thrust speed. There is zerothrust and the propeller is approaching 100% efficiency.Since most aircraft don't have zero drag (especially Pietenpols!), the airplanecomes to equilibrium somewhere between the two extremes. In the case of a Pietwith a large propeller and a slow turning engine, it is when the propeller isat about 75% efficiency. You can not get better than that unless you clean upthe drag.One variable you can adjust in a propeller, that has an effect on efficiency, isthe propeller diameter. The bigger the propeller the more air it can push backwards.Therefore for a given propeller wash speed there is more thrust. Oranother way to look at it; for a required thrust, a bigger propeller needs lesswash speed. Therefore, if you remember about efficiency, there is more efficiencybecause for a given thrust the velocity of the propeller wash is less.Diameter also effects pitch. The larger the diameter, the less pitch you need (theair can move slower). This effects the speed range of the aircraft. A largepropeller is like having a car with one low gear. A small propeller is likehaving one high gear. If you have a slow airplane, a low gear can work fine, ina fast airplane, it won't work because the engine will not produce any powerto get going (fast airplanes always have surplus horsepower).The relationship for best propeller efficiency has been determined to be that thepropeller tip speed should be approximately 2.3 times the aircraft speed atcruise. This you can't achieve. The diameter is too large or the rpm is too slow.The bigger the diameter and the slower the engine the better. This is whyWorld War One aircraft perform so well (best propeller efficiency) on low power- 1400 rpm engines turning 80" propellers.. Because our engine choices requiremore revs to produce power, we have to compromise and lose efficiency. A Pietwith a 72" propeller, 2300 max. rpm and 65 horsepower is the typical compromisewith a Continental engine, but a Model "A" with 55 horsepower will do aboutthe same.Unfortunately, to retain reliability, Model "A's" are usually built to produce50 horsepower - or a bit less.The Corvair engine is another compromise. They have a loss of efficiency due tothe small diameter propeller and accelerate poorly (due to the tall gear effect)but produces good power.So how does this relate to a VW engine?In order to use a Volkswagen engine, it has to really rev (over 3300 rpm) to producesufficient power. This requires a small propeller to keep the tip speedsdown. It therefore has poor efficiency, or a too "tall" gear. If you pitch itso you can take off, you won't fly faster than about 50 mph. If you pitch itfor cruise you will need a 6000 ft strip for take-off! The Corvair works becauseit has surplus horsepower and can afford to waste some. The VW can't affordthe wasted horsepower.The only approach with a VW that will work is the one that Pazmany used on hisPL-4. It uses a reduction belt. You then need a starter, and alternator, wiringetc. You also need to think about cooling. At 60 mph there is not much ramair. The Corvair requires a blower to get proper cooling. If you go this routeyou have two projects instead of one! In Pazmany's configuration, the installationprobably weighs enough to allow an acceptable C.G. If not, this is yoursecond major problem. If you solve these problems, get used to an engine revvinglike crazy, making much noise, as you cruise along.Aircraft are a compromise. In a slow airplane you must use a large displacement,slow turning engine if you want to keep it simple!How about a diesel?Someone in the 1970's put a Mercedes diesel in a Pietenpol. They brought it toOshkosh and created a lot of interest. The problem was it didn't have enough power.The engine was replaced with something else and it flew OK. The limitationwith diesel engines is their power-to-weight ratio. They tend to be heavyfor the power they produce. The VW diesel engine is not that heavy, but I don'tthink that it will produce enough power. You need about 50 hp to fly an AirCamper - a bit less to fly the Sky Scout. You need this type of power at no morethan about 2500 rpm. This is why a VW beetle engine is no good - because youhave to rev it too high to obtain the needed power.The other factors to consider in the over-all weight of a VW Diesel, is that youwill probably need a gear reduction unit, and if you use a gear reduction unit,you will also need a starter. Water in the cooling system weighs 10 lbs. agallon etc. I am sure you will be over 250 lbs. when you are finished.Fuel is also an issue. You could use Jet A, but how will you get that big hosenozzle in your Pietenpol filler tube?I am not trying to discourage anyone from developing a new airplane design. Justthink about it long and hard before you try it.I think building an airplane it enough of a project. Building an engine is anothercomplete project. I know someone who has been putting an auto engine in aflying airplane and is now in his fifth year in doing so!Read this topic online here:http://forums.matronics.com/viewtopic.p ... __________
Pietenpol-List: VW engines in Pietenpols
Pietenpol-List: Re: VW engines in Pietenpols
Original Posted By: "jarheadpilot82"
Hi Bill,thank you for your article, it is very educative
Let me ask you a question:There are several variants of VW engine. The smallest is obviously too small topower a Piet, but then we also have the bigger VWs, which have more power. Iam talking about VW with 2500ccm, which produces 85hp. What would happen if Iinstalled a larger propeller on it (170cm) - it would decrease the rpm, the powerwill be lower but torque will increase. Am I right?Would that be a sufficient solution?You know, the advantage of the VW which is connected directly with the propeller- so no reduction drive- is that you don't need to cool down the engine so much,you don't need an electric starter. So I can save let's say 15kg in weightand coolants, liquids.Because this VW is lighter, it would need to be moved slightly forward, but I thinkthat not more than 5cm.So if my ideas are not totaly wrong, it looks like this 2500ccm (2,5litre) VW wouldbe sufficient for a decent flight with a passenger in a Pietenpol.And now I stabbed the wasp's nest 
--------My production of WW1 propellers, trophies and constructions:Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: VW engines in Pietenpols
Hi Bill,thank you for your article, it is very educative
Let me ask you a question:There are several variants of VW engine. The smallest is obviously too small topower a Piet, but then we also have the bigger VWs, which have more power. Iam talking about VW with 2500ccm, which produces 85hp. What would happen if Iinstalled a larger propeller on it (170cm) - it would decrease the rpm, the powerwill be lower but torque will increase. Am I right?Would that be a sufficient solution?You know, the advantage of the VW which is connected directly with the propeller- so no reduction drive- is that you don't need to cool down the engine so much,you don't need an electric starter. So I can save let's say 15kg in weightand coolants, liquids.Because this VW is lighter, it would need to be moved slightly forward, but I thinkthat not more than 5cm.So if my ideas are not totaly wrong, it looks like this 2500ccm (2,5litre) VW wouldbe sufficient for a decent flight with a passenger in a Pietenpol.And now I stabbed the wasp's nest --------My production of WW1 propellers, trophies and constructions:Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: VW engines in PietenpolsRe: Pietenpol-List: Re: VW engines in Pietenpols
Original Posted By: "Cuy, Michael D. (GRC-RXD0)[Vantage Partners, LLC]"
Subject: Re: Pietenpol-List: Re: VW engines in PietenpolsHi Vasek,Just an other word about the VW. When I begun the project few years ago, Iwas thinking like you: "I want and I am going to fly with a VW", but now Ihave an A65 on the nose.The reasons are lots, but technicaly you can not run a VW at 3000 rpm witha big prop; it do not work, you need to reduce the rpm with a reductindrive to keep the big prop, and you have to modify lots of things in theengine too. You can search what in the net.There are VW engins flying, but not in so dragged planes, about conversionof the engine, you can read this article toohttp://www.eaa.org/experimenter/articles/2010- ... plants.asp visitthose builders and see what they do with the engins to make them fly safe;lots of job an very expensive at all.Look this thred about engines on the piet:http://forums.matronics.com/viewtopic.p ... ines&start RegardsMario Giacummo2014-02-25 11:00 GMT-02:00 Vasek :>> Hi Bill,>> thank you for your article, it is very educative>> Let me ask you a question:>> There are several variants of VW engine. The smallest is obviously too> small to power a Piet, but then we also have the bigger VWs, which have> more power. I am talking about VW with 2500ccm, which produces 85hp. What> would happen if I installed a larger propeller on it (170cm) - it would> decrease the rpm, the power will be lower but torque will increase. Am I> right?>> Would that be a sufficient solution?>> You know, the advantage of the VW which is connected directly with the> propeller - so no reduction drive- is that you don't need to cool down the> engine so much, you don't need an electric starter. So I can save let's say> 15kg in weight and coolants, liquids.>> Because this VW is lighter, it would need to be moved slightly forward,> but I think that not more than 5cm.>> So if my ideas are not totaly wrong, it looks like this 2500ccm (2,5litre)> VW would be sufficient for a decent flight with a passenger in a Pietenpol.>> And now I stabbed the wasp's nest>> >> --------> My production of WW1 propellers, trophies and constructions:> =88=BC>>> Read this topic online here:>> http://forums.matronics.com/viewtopic.p ... __________
Subject: Re: Pietenpol-List: Re: VW engines in PietenpolsHi Vasek,Just an other word about the VW. When I begun the project few years ago, Iwas thinking like you: "I want and I am going to fly with a VW", but now Ihave an A65 on the nose.The reasons are lots, but technicaly you can not run a VW at 3000 rpm witha big prop; it do not work, you need to reduce the rpm with a reductindrive to keep the big prop, and you have to modify lots of things in theengine too. You can search what in the net.There are VW engins flying, but not in so dragged planes, about conversionof the engine, you can read this article toohttp://www.eaa.org/experimenter/articles/2010- ... plants.asp visitthose builders and see what they do with the engins to make them fly safe;lots of job an very expensive at all.Look this thred about engines on the piet:http://forums.matronics.com/viewtopic.p ... ines&start RegardsMario Giacummo2014-02-25 11:00 GMT-02:00 Vasek :>> Hi Bill,>> thank you for your article, it is very educative
>> Let me ask you a question:>> There are several variants of VW engine. The smallest is obviously too> small to power a Piet, but then we also have the bigger VWs, which have> more power. I am talking about VW with 2500ccm, which produces 85hp. What> would happen if I installed a larger propeller on it (170cm) - it would> decrease the rpm, the power will be lower but torque will increase. Am I> right?>> Would that be a sufficient solution?>> You know, the advantage of the VW which is connected directly with the> propeller - so no reduction drive- is that you don't need to cool down the> engine so much, you don't need an electric starter. So I can save let's say> 15kg in weight and coolants, liquids.>> Because this VW is lighter, it would need to be moved slightly forward,> but I think that not more than 5cm.>> So if my ideas are not totaly wrong, it looks like this 2500ccm (2,5litre)> VW would be sufficient for a decent flight with a passenger in a Pietenpol.>> And now I stabbed the wasp's nest>> >> --------> My production of WW1 propellers, trophies and constructions:> =88=BC>>> Read this topic online here:>> http://forums.matronics.com/viewtopic.p ... __________Pietenpol-List: Re: VW engines in Pietenpols
Original Posted By: "Vasek"
I ALWAYS wanted a Ford powered Piet. BUT, probably a lot like a lot of Piet buildersand buyers, I didn't have much experience with ANY airplane engine. Idecided I had enough stuff to learn owning and operating my first light civilplane that the added difficulty of a non standard engine wasn't a great idea.So I also opted for the non electric A65. REALLY HAPPY I did.However, it being the experimental it is, I just might still build a Ford A andput it up front. But when it comes to flying it to Brodhead or something, I'llput the A65 back on. Can't imagine it would take more than a day once theconversion is complete.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: VW engines in Pietenpols
I ALWAYS wanted a Ford powered Piet. BUT, probably a lot like a lot of Piet buildersand buyers, I didn't have much experience with ANY airplane engine. Idecided I had enough stuff to learn owning and operating my first light civilplane that the added difficulty of a non standard engine wasn't a great idea.So I also opted for the non electric A65. REALLY HAPPY I did.However, it being the experimental it is, I just might still build a Ford A andput it up front. But when it comes to flying it to Brodhead or something, I'llput the A65 back on. Can't imagine it would take more than a day once theconversion is complete.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: VW engines in Pietenpols
Re: Pietenpol-List: Re: VW engines in Pietenpols
Original Posted By: Gary Boothe
Thank you for the link.Today I talked to a friend aircraft constructor and he could not believe that thePietenpol would not fly will with the VW 2.5litre 85hp engine. ...So now we have two different opinions. What is the conclusion?--------My production of WW1 propellers, trophies and constructions:Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Re: Pietenpol-List: Re: VW engines in Pietenpols
Thank you for the link.Today I talked to a friend aircraft constructor and he could not believe that thePietenpol would not fly will with the VW 2.5litre 85hp engine. ...So now we have two different opinions. What is the conclusion?--------My production of WW1 propellers, trophies and constructions:Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Re: Pietenpol-List: Re: VW engines in Pietenpols
Original Posted By: Kip and Beth Gardner
Has your friend ever seen a VW Piet? Neither have I.GaryNX308MBSent from my iPhone> On Feb 25, 2014, at 6:30 AM, "Vasek" wrote:> > > Thank you for the link.> > Today I talked to a friend aircraft constructor and he could not believe thatthe Pietenpol would not fly will with the VW 2.5litre 85hp engine. > > ...> > So now we have two different opinions. What is the conclusion?> > --------> My production of WW1 propellers, trophies and constructions:> > > > > > Read this topic online here:> > http://forums.matronics.com/viewtopic.p ... 322#419322> > > > > > > > > > ________________________________________________________________________________
Has your friend ever seen a VW Piet? Neither have I.GaryNX308MBSent from my iPhone> On Feb 25, 2014, at 6:30 AM, "Vasek" wrote:> > > Thank you for the link.> > Today I talked to a friend aircraft constructor and he could not believe thatthe Pietenpol would not fly will with the VW 2.5litre 85hp engine. > > ...> > So now we have two different opinions. What is the conclusion?> > --------> My production of WW1 propellers, trophies and constructions:> > > > > > Read this topic online here:> > http://forums.matronics.com/viewtopic.p ... 322#419322> > > > > > > > > > ________________________________________________________________________________
Re: Pietenpol-List: Re: VW engines in Pietenpols
Original Posted By: "Dick N"
Does your friend have any experience with building a Pietenpol? If not, his opinion is exactly that, his opinion, it may or may not be informed. There are many more than "two" opinions on this, there is an entire history of people working with this design, and the overwhelming experience of those who have tried it is that, yes, you can make a VW engine work, but the time, expense and headaches would be better devoted to something that will actually perform well on the airplane. There are many good engine choices available, no matter where in the world you live - look around and find something suitable instead of putting a lot of energy into making something marginal work.Just my 'opinion' - still planning on using a WW Corvair conversion & hopefully restarting my project with the help of a new partner this Spring.Kip GardnerOn Feb 25, 2014, at 9:30 AM, Vasek wrote:>> Thank you for the link.>> Today I talked to a friend aircraft constructor and he could not > believe that the Pietenpol would not fly will with the VW 2.5litre > 85hp engine.>> ...>> So now we have two different opinions. What is the conclusion?>> --------> My production of WW1 propellers, trophies and constructions:> >>> Read this topic online here:>> http://forums.matronics.com/viewtopic.p ... __________
Does your friend have any experience with building a Pietenpol? If not, his opinion is exactly that, his opinion, it may or may not be informed. There are many more than "two" opinions on this, there is an entire history of people working with this design, and the overwhelming experience of those who have tried it is that, yes, you can make a VW engine work, but the time, expense and headaches would be better devoted to something that will actually perform well on the airplane. There are many good engine choices available, no matter where in the world you live - look around and find something suitable instead of putting a lot of energy into making something marginal work.Just my 'opinion' - still planning on using a WW Corvair conversion & hopefully restarting my project with the help of a new partner this Spring.Kip GardnerOn Feb 25, 2014, at 9:30 AM, Vasek wrote:>> Thank you for the link.>> Today I talked to a friend aircraft constructor and he could not > believe that the Pietenpol would not fly will with the VW 2.5litre > 85hp engine.>> ...>> So now we have two different opinions. What is the conclusion?>> --------> My production of WW1 propellers, trophies and constructions:> >>> Read this topic online here:>> http://forums.matronics.com/viewtopic.p ... __________
Re: Pietenpol-List: Air-Ground Communications
Original Posted By: "John Franklin"
JohnDon't throw the old license away, It doesn't expire. You don't need it any more in the U.S. But if you fly into Canada you are supposed to have it. I have been into Canada many times and have never been asked for it but, who knows.Dick N.----- Original Message -----
JohnDon't throw the old license away, It doesn't expire. You don't need it any more in the U.S. But if you fly into Canada you are supposed to have it. I have been into Canada many times and have never been asked for it but, who knows.Dick N.----- Original Message -----
Pietenpol-List: Re: VW engines in Pietenpols
Original Posted By: "AircamperN11MS"
Hey, I have an idea. How about the scale find its way to Frazeur Lake for the Pietgathering. We could have a pull off. Perhaps send it t to Chris Tracy.--------Scott LiefeldFlying N11MS since March 1972Steel TubeC-85-12Wire WheelsBrodhead in 1996Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: VW engines in Pietenpols
Hey, I have an idea. How about the scale find its way to Frazeur Lake for the Pietgathering. We could have a pull off. Perhaps send it t to Chris Tracy.--------Scott LiefeldFlying N11MS since March 1972Steel TubeC-85-12Wire WheelsBrodhead in 1996Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: VW engines in Pietenpols
Pietenpol-List: Re: VW engines in Pietenpols
Original Posted By: "aerocarjake"
>From the link "Pietenpol Airfoil - smoothed and points added for XFOIL analysis" at http://www.airminded.net/piet/piet.html :1.0 0.0033245110.983333333 0.0073710690.966666667 0.0114194370.95 0.0154668480.933333333 0.0195115970.916666667 0.0235518720.9 0.0275853750.883333333 0.0316089820.866666667 0.0356183030.85 0.039607110.833333333 0.0435667450.816666667 0.0474861950.8 0.0513536030.783333333 0.0551594530.766666667 0.0588994550.75 0.0625740570.733333333 0.0661847170.716666667 0.0697305170.7 0.073207740.683333333 0.0766103230.666666667 0.0799264470.65 0.0831313770.633333333 0.0861844720.616666667 0.0890437450.6 0.0916889650.583333333 0.094134570.566666667 0.0964178450.55 0.098578320.533333333 0.1006421130.516666667 0.1026166480.5 0.1044895130.483333333 0.1062321180.466666667 0.1078117750.45 0.1092040150.433333333 0.1103979920.416666667 0.1113945680.4 0.1122023480.383333333 0.1128318470.366666667 0.11328840.35 0.1135661720.333333333 0.1136423250.316666667 0.1134723830.3 0.1130037430.283333333 0.1122244920.266666667 0.1111810080.25 0.109938560.233333333 0.1085525020.216666667 0.1070554880.2 0.1054347020.191666667 0.1045529520.183333333 0.1035994950.175 0.102553550.166666667 0.1013973480.158333333 0.1001143120.15 0.0986778120.141666667 0.0970416820.133333333 0.0951478570.125 0.092955020.116666667 0.090480150.108333333 0.0877854580.1 0.0848894830.091666667 0.0817250820.0875 0.0800177420.083333333 0.0782239430.079166667 0.076349580.075 0.0744041580.070833333 0.0723976130.066666667 0.0703371380.0625 0.0682250070.058333333 0.0660587120.054166667 0.0638320230.05 0.0615361520.045833333 0.0591612270.041666667 0.0566981570.0375 0.0541401070.033333333 0.0514831920.029166667 0.0487261370.025 0.0458685750.020833333 0.0429072970.016666667 0.0398295130.0125 0.0365984170.008453424 0.0332132430.006115179 0.0310349720.004966654 0.0298471720.003854819 0.0285651830.002820217 0.0271686670.00191922 0.02564710.001196105 0.024009830.000651377 0.0222820950.000262064 0.0204860153.60383E-05 0.0186361022.92697E-05 0.0167564570.000328321 0.014898650.001009116 0.0131441770.002084945 0.0115815410.003495569 0.0102755280.005132964 0.0092493030.006876884 0.008483730.008624848 0.0079302120.011904731 0.0072386280.014817507 0.0068402070.017452715 0.0065731680.020833333 0.006301510.025 0.0060227230.029166667 0.005771890.033333333 0.0055318570.0375 0.00529410.041666667 0.0050534880.045833333 0.0048059940.05 0.0045476070.054166667 0.0042742980.058333333 0.003982980.0625 0.0036726440.066666667 0.003345570.070833333 0.0030085420.075 0.0026729570.079166667 0.0023526710.083333333 0.0020611220.0875 0.0018083890.091666667 0.0015983860.1 0.0012861210.108333333 0.001045990.116666667 0.0008121140.125 0.0005995120.133333333 0.000460950.141666667 0.0004211120.15 0.0004705110.158333333 0.0005914140.166666667 0.0007728770.175 0.001014350.183333333 0.001319060.191666667 0.0016864230.2 0.0021092380.216666667 0.0030755710.233333333 0.0041324530.25 0.0052205420.266666667 0.006302880.283333333 0.0073534880.3 0.0083378530.316666667 0.0091957050.333333333 0.0098686940.35 0.0103409930.366666667 0.0106308580.383333333 0.0107646450.4 0.0107644260.416666667 0.0106455920.433333333 0.0104188310.45 0.0100925070.466666667 0.0096721330.483333333 0.0091574530.5 0.0085416630.516666667 0.0078200730.533333333 0.0070056250.55 0.0061391170.566666667 0.0052774380.583333333 0.0044708910.6 0.0037495570.616666667 0.0031250170.633333333 0.0025974650.65 0.0021629940.666666667 0.0018179070.683333333 0.0015586030.7 0.0013780840.716666667 0.0012623670.733333333 0.0011907670.75 0.0011408260.766666667 0.0010950450.783333333 0.0010441490.8 0.0009850830.816666667 0.0009178290.833333333 0.0008434010.85 0.0007630250.866666667 0.0006778960.883333333 0.0005891570.9 0.0004979440.916666667 0.0004054510.933333333 0.0003130070.95 0.0002222590.966666667 0.0001356130.983333333 5.75147E-051.0 0.00000027--------Bill FrankRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: VW engines in Pietenpols
>From the link "Pietenpol Airfoil - smoothed and points added for XFOIL analysis" at http://www.airminded.net/piet/piet.html :1.0 0.0033245110.983333333 0.0073710690.966666667 0.0114194370.95 0.0154668480.933333333 0.0195115970.916666667 0.0235518720.9 0.0275853750.883333333 0.0316089820.866666667 0.0356183030.85 0.039607110.833333333 0.0435667450.816666667 0.0474861950.8 0.0513536030.783333333 0.0551594530.766666667 0.0588994550.75 0.0625740570.733333333 0.0661847170.716666667 0.0697305170.7 0.073207740.683333333 0.0766103230.666666667 0.0799264470.65 0.0831313770.633333333 0.0861844720.616666667 0.0890437450.6 0.0916889650.583333333 0.094134570.566666667 0.0964178450.55 0.098578320.533333333 0.1006421130.516666667 0.1026166480.5 0.1044895130.483333333 0.1062321180.466666667 0.1078117750.45 0.1092040150.433333333 0.1103979920.416666667 0.1113945680.4 0.1122023480.383333333 0.1128318470.366666667 0.11328840.35 0.1135661720.333333333 0.1136423250.316666667 0.1134723830.3 0.1130037430.283333333 0.1122244920.266666667 0.1111810080.25 0.109938560.233333333 0.1085525020.216666667 0.1070554880.2 0.1054347020.191666667 0.1045529520.183333333 0.1035994950.175 0.102553550.166666667 0.1013973480.158333333 0.1001143120.15 0.0986778120.141666667 0.0970416820.133333333 0.0951478570.125 0.092955020.116666667 0.090480150.108333333 0.0877854580.1 0.0848894830.091666667 0.0817250820.0875 0.0800177420.083333333 0.0782239430.079166667 0.076349580.075 0.0744041580.070833333 0.0723976130.066666667 0.0703371380.0625 0.0682250070.058333333 0.0660587120.054166667 0.0638320230.05 0.0615361520.045833333 0.0591612270.041666667 0.0566981570.0375 0.0541401070.033333333 0.0514831920.029166667 0.0487261370.025 0.0458685750.020833333 0.0429072970.016666667 0.0398295130.0125 0.0365984170.008453424 0.0332132430.006115179 0.0310349720.004966654 0.0298471720.003854819 0.0285651830.002820217 0.0271686670.00191922 0.02564710.001196105 0.024009830.000651377 0.0222820950.000262064 0.0204860153.60383E-05 0.0186361022.92697E-05 0.0167564570.000328321 0.014898650.001009116 0.0131441770.002084945 0.0115815410.003495569 0.0102755280.005132964 0.0092493030.006876884 0.008483730.008624848 0.0079302120.011904731 0.0072386280.014817507 0.0068402070.017452715 0.0065731680.020833333 0.006301510.025 0.0060227230.029166667 0.005771890.033333333 0.0055318570.0375 0.00529410.041666667 0.0050534880.045833333 0.0048059940.05 0.0045476070.054166667 0.0042742980.058333333 0.003982980.0625 0.0036726440.066666667 0.003345570.070833333 0.0030085420.075 0.0026729570.079166667 0.0023526710.083333333 0.0020611220.0875 0.0018083890.091666667 0.0015983860.1 0.0012861210.108333333 0.001045990.116666667 0.0008121140.125 0.0005995120.133333333 0.000460950.141666667 0.0004211120.15 0.0004705110.158333333 0.0005914140.166666667 0.0007728770.175 0.001014350.183333333 0.001319060.191666667 0.0016864230.2 0.0021092380.216666667 0.0030755710.233333333 0.0041324530.25 0.0052205420.266666667 0.006302880.283333333 0.0073534880.3 0.0083378530.316666667 0.0091957050.333333333 0.0098686940.35 0.0103409930.366666667 0.0106308580.383333333 0.0107646450.4 0.0107644260.416666667 0.0106455920.433333333 0.0104188310.45 0.0100925070.466666667 0.0096721330.483333333 0.0091574530.5 0.0085416630.516666667 0.0078200730.533333333 0.0070056250.55 0.0061391170.566666667 0.0052774380.583333333 0.0044708910.6 0.0037495570.616666667 0.0031250170.633333333 0.0025974650.65 0.0021629940.666666667 0.0018179070.683333333 0.0015586030.7 0.0013780840.716666667 0.0012623670.733333333 0.0011907670.75 0.0011408260.766666667 0.0010950450.783333333 0.0010441490.8 0.0009850830.816666667 0.0009178290.833333333 0.0008434010.85 0.0007630250.866666667 0.0006778960.883333333 0.0005891570.9 0.0004979440.916666667 0.0004054510.933333333 0.0003130070.95 0.0002222590.966666667 0.0001356130.983333333 5.75147E-051.0 0.00000027--------Bill FrankRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: VW engines in Pietenpols
Original Posted By: "TOM STINEMETZE"
Thanks for the link Terry - good read....--------Jake Schultz - curator,Newport Way Air Museum (OK, it's just my home)Read this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Thu, 27 Feb 2014 01:02:08 -0600
Thanks for the link Terry - good read....--------Jake Schultz - curator,Newport Way Air Museum (OK, it's just my home)Read this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Thu, 27 Feb 2014 01:02:08 -0600
Pietenpol-List: Re: Speed
Original Posted By: Keith
Dan -The question about the effects of the fabric sagging behind the sharp line of theleading edge sheeting is fraught with complications - it might hurt, it mighthelp, it might be of no consequence.Supporting the assertion it will hurt:The sudden discontinuity in contour will trip the boundary layer into turbulentflow, increasing the drag.It might also cause a sudden loss of lift at the stall. (The mechanism for howthe latter could occur may seem mysterious in light of the discussion in the nextsection, but it has been known to occur - mostly on airfoils designed forextensive laminar flow, which the FC-10 definitely is not).Supporting the assertion it will help: As for the drag issue, the back face of the spar on an Air Camper built to Pietenpolplans is at about 13% of chord, well forward of where we would expect thenatural transition to turbulent flow on a smooth FC-10 airfoil. But let's behonest, now, "Air Camper, thy middle name is Drag." Will the increase in dragfrom an early transition at 13% really cause a *significant* percentage increasein total drag? Um, no, so let's not worry about it, OK?At very low Reynolds number (Rn) it's actually hard to prevent laminar flow, buta laminar boundary layer tends to lose energy the farther back it goes, so whenit encounters the increasing pressure gradient past the peak of the uppersurface curvature it's "too tired" to follow the curvature and the flow jumpsoff the surface, killing the lift and creating a huge drag rise. The model airplanepeople actually put turbulator spars and even spanwise wires suspended justabove the surface on little posts to force the air into turbulent flow soit can follow the contour - the drag from the turbulence is far less than thedrag from laminar flow separating completely from the surface. As for lift, theturbulent flow keeping the boundary layer attached will increase the angle ofattack before the stall (i.e. lower the stall speed) and may contribute to thestall spreading slowly from the trailing edge forward (i.e. help prevent asudden drop off).Especially during the critical phases of taking off and landing, the Rn for anAir Camper is low enough that fixing the transition at the back edge of the sparmay help in the manner described above.Supporting the assertion it will not have any significant effects:The 2D section drag of the FC-10 might be significantly increased, but as notedabove the significance will probably be rendered insignificant relative to themonstrous total drag from all causes. As for the lift, who knows without doing testing?Steve Wittman had a method for evaluating the positive and negative effects ofchanging the design of a wing: Build one half of a new wing and put it on theairplane without changing the other half, then go flying.When you recover your Air Camper, you could start with just one wing and removethe support under the leading edge sheeting before recovering, then go flying.You should, of course, be hyper attentive while gradually approaching the stall,ready to recover instantly in case either wing drops early. Since your AirCamper stalls gently, I suspect that testing will reveal no significant change,so you can proceed to making the other wing have the better appearance.--------Bill FrankRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Thu, 27 Feb 2014 09:36:08 +0000
Dan -The question about the effects of the fabric sagging behind the sharp line of theleading edge sheeting is fraught with complications - it might hurt, it mighthelp, it might be of no consequence.Supporting the assertion it will hurt:The sudden discontinuity in contour will trip the boundary layer into turbulentflow, increasing the drag.It might also cause a sudden loss of lift at the stall. (The mechanism for howthe latter could occur may seem mysterious in light of the discussion in the nextsection, but it has been known to occur - mostly on airfoils designed forextensive laminar flow, which the FC-10 definitely is not).Supporting the assertion it will help: As for the drag issue, the back face of the spar on an Air Camper built to Pietenpolplans is at about 13% of chord, well forward of where we would expect thenatural transition to turbulent flow on a smooth FC-10 airfoil. But let's behonest, now, "Air Camper, thy middle name is Drag." Will the increase in dragfrom an early transition at 13% really cause a *significant* percentage increasein total drag? Um, no, so let's not worry about it, OK?At very low Reynolds number (Rn) it's actually hard to prevent laminar flow, buta laminar boundary layer tends to lose energy the farther back it goes, so whenit encounters the increasing pressure gradient past the peak of the uppersurface curvature it's "too tired" to follow the curvature and the flow jumpsoff the surface, killing the lift and creating a huge drag rise. The model airplanepeople actually put turbulator spars and even spanwise wires suspended justabove the surface on little posts to force the air into turbulent flow soit can follow the contour - the drag from the turbulence is far less than thedrag from laminar flow separating completely from the surface. As for lift, theturbulent flow keeping the boundary layer attached will increase the angle ofattack before the stall (i.e. lower the stall speed) and may contribute to thestall spreading slowly from the trailing edge forward (i.e. help prevent asudden drop off).Especially during the critical phases of taking off and landing, the Rn for anAir Camper is low enough that fixing the transition at the back edge of the sparmay help in the manner described above.Supporting the assertion it will not have any significant effects:The 2D section drag of the FC-10 might be significantly increased, but as notedabove the significance will probably be rendered insignificant relative to themonstrous total drag from all causes. As for the lift, who knows without doing testing?Steve Wittman had a method for evaluating the positive and negative effects ofchanging the design of a wing: Build one half of a new wing and put it on theairplane without changing the other half, then go flying.When you recover your Air Camper, you could start with just one wing and removethe support under the leading edge sheeting before recovering, then go flying.You should, of course, be hyper attentive while gradually approaching the stall,ready to recover instantly in case either wing drops early. Since your AirCamper stalls gently, I suspect that testing will reveal no significant change,so you can proceed to making the other wing have the better appearance.--------Bill FrankRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Thu, 27 Feb 2014 09:36:08 +0000