Original Posted By: "cdlwingnut"
Builders,I received an email from a Corvair builder, Chuck Callahan, that I had met severaltimes at Corvair Colleges. He has decided to not build any aircraft, so hehas put his Corvair engine project on Barnstormers - http://www.barnstormers.com/ad_detail.php?ID=1223914He asked that I make it known on this forum, so I am doing so. His pricing is onhis spec sheet. I have no other advice but to say that I met Chuck, and he seemedlike a good guy when we spoke. I hate to see anybody leave aviation, butI also would like to see another Corvair engine built, and not languish in agarage. If any of you have an interest in getting a head start on your Corvairengine, contact him via Barnstormers.--------Semper Fi,Terry HandAthens, GARead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Ragwing Ultra-Piet
Pietenpol-List: Ragwing Ultra-Piet
Pietenpol-List: Re: Riblett to Spar Fit
Original Posted By: "Brent Wilson"
though not officially a pietenpol i have decided to start on an ultra-piet ribstockordered and on the way now to build a jig and get the clock started on thebuild.are there any other ragwing builders/owners hereRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Riblett to Spar Fit
though not officially a pietenpol i have decided to start on an ultra-piet ribstockordered and on the way now to build a jig and get the clock started on thebuild.are there any other ragwing builders/owners hereRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Riblett to Spar Fit
Pietenpol-List: Re: Ragwing Ultra-Piet
Original Posted By: "taildrags"
Terry, Brent-I am an engineer, so I can get carried away with numbers and formulas, but usuallywhen that happens people just quietly walk away and leave me muttering tomyself, so it's OK if you do too ;o) When we talk about a spar being "strong",we have to define what kind of strength we're talking about. I'll be over-simplifyinghere, but when it comes to beams (like our wing spars), there is bendingstrength and there is shear strength. We are interested in bending strengthso let's look at our Air Camper wing to see what's what.Structurally, there are three elements to our wing. Simplifying, of course. Thecentersection is one element, the section of the wing outboard from the cabanesto the lift strut attach points is another, and the part outboard of thelift strut attach points is a third. Of those three, the centersection is themost lightly loaded and the easiest to analyze structurally because it is supportedand restrained at both ends by the four cabane uprights. The next section,from the cabanes out to the lift strut attach points, is more heavily loadedthan the centersection but it, too, is restrained at both ends (by the cabanesat one end and by the lift struts at the other). The outboard-most sectionof wing is the part that has to work the hardest because it is only supportedat the lift strut end and the other end is cantilevered out into thin air.That part of the wing is what needs the most strength in bending, because that'swhat it has to work hardest at.The heavies that Terry flies have wings that are completely cantilevered out fromthe fuselage, so when you are at maximum takeoff weight with full fuel, pax,and baggage and you pull that baby into climb attitude on takeoff, the wingsbend gracefully in an upward sweep out at the tips as they do their hardest work.In a spectacular example of this taken to the extreme, check out the 787Dreamliner's wingtips bending upward about 25 feet at the tips (during testing,of course), here:https://www.wired.com/2010/03/boeing-78 ... x-test/The bending stress is at its maximum at the wing roots of a cantilevered wing,diminishing as you go out spanwise to the tips, where it is zero. So, in theory,we can save weight by tapering the wing spars to follow the profile of thediminishing stress as we go out to the tips, but that adds complexity to thespar construction, and if we also taper the wing chordwise like the heavies are,it means every rib is different from its neighbor and everything is harderto make. So, we build our wing Hershey bar-style with a constant chord and constantspar size for simplicity and ease of construction. Consequently, the wingcentersection is very much overbuilt, the section from the cabanes to thelift struts is still plenty overbuilt, and the outboard section is probably justabout right but progressively more and more overbuilt as you go from the liftstrut attach points out to the wing tips where the bending stress is (theoretically)zero.Bottom line, we analyze the forces in an Air Camper wing where the bending stressis the highest: on the outboard section, where the lift struts attach. Inboardof that, the spars are restrained from deflecting in bending and outboardof that, they are not.Now for the math. Feel free to leave the room quietly ;o)The bending stress in a beam (which our wing spars are) is calculated by knowingtwo things: the moment (which is the product of the lift force on the wing timesthe distance where it acts on the wing), divided by the section modulus.Forget about two of those things for a minute because we are looking for themaximum "strength" of our wing and we know the properties of the wood (or metal)that the spar is made of so we know its maximum allowable stress, and we alsoknow the lift forces on the wing because we are designing it for a certainmaximum gross weight, G-force, and safety factor. That just leaves the sectionmodulus, which is a property of the beam section. It's different for a tube,a rod, an I-beam, a C-section, rectangle, square, bar, whatever. In the caseof a typical rectangular-section wood beam, the section modulus is equal tothe width (thickness) times the height (spar depth) squared, divided by six.As H. Ross Perot used to say during his talks, "stay with me now..." ;o)The amount of stress that the wood in our spar is able to take without failingis essentially constant and is a property of the wood. So, the larger we canget the section modulus of our spar to be, the "stronger" it is (the more bendingstress it can take, which means higher Gs or a higher gross weight, or both).So, lets look at the section modulus. We have two things we can work withto determine it: the thickness and the height. If we double the thickness,we also double the section modulus but if we double the HEIGHT, we increase thesection modulus by a factor of FOUR because the height gets squared in the equation(2x2 = 4). Since we're trying to build our spars as light as we can,why make the spars twice as thick to double the section modulus (but double theweight), when we can do the same thing by simply increasing the spar depth byabout 2 and the weight only goes up by about 40% instead of 100%? In resistingbending force on the spars, you get more bang for the buck by going tallerrather than fatter.So (and this has nothing to do with where you slept last night), your example ofa spar that is 1" thick and 5" tall means that its section modulus is about4.17 but if we make it 3 times that tall, 15", its section modulus skyrocketsto 37.5 and the spar isnt 3 times stronger, its 9 times stronger in bending thanthe 5" tall one. There's that squaring effect at play.But wait, because there are many reasons why it would be impractical to actuallybuild something like that due to buckling from "slenderness" and fiber shearin the web, twisting, and other things. However, the point is that in a wingspar that is subjected to bending loads, depth is everything. I'm not certainof the Riblett airfoil nomenclature, but if the 612 has 12% thickness and thewing chord is 60", the airfoil would be about 7.2" tall at its maximum thicknessso maybe 7" at the main spar. (Terry, how tall are the metal J-3 spars?)For a 1" thick rectangular Riblett 612 spar, the section modulus might be 8.17.The stock unrouted 1 thick Piet spar is 4-3/4" tall so it might have a sectionmodulus of 3.76 and the deeper 612 spar, if it's a rectangular shape likethe Piet's, is then theoretically competent to take more than twice the bendingstress than the stock Piet spar, so maybe (to temper what Wese said aboutthe Air Camper wing spar), maybe the 2-G Piet becomes a 4-G "Super Piet" ;o)All of this is theoretical and none of the above should be taken as a rigorousanalysis of either spar, or of the wing, or anything other than a general discussionto point out that calculated design can sometimes beat eyeball engineering.On the other hand, many things that are exquisitely designed, cannot readilybe constructed on the floor of a wooden barn using hand tools. Thus we havethe timeless and understated technical elegance of the Pietenpol Air Camper,which does what it does very well and without a lot of analysis or re-engineering.If you choose to depart from Mr. Pietenpols design, take your time analyzingwhat you do.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 power, 72x36 Culver propRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Ragwing Ultra-Piet
Terry, Brent-I am an engineer, so I can get carried away with numbers and formulas, but usuallywhen that happens people just quietly walk away and leave me muttering tomyself, so it's OK if you do too ;o) When we talk about a spar being "strong",we have to define what kind of strength we're talking about. I'll be over-simplifyinghere, but when it comes to beams (like our wing spars), there is bendingstrength and there is shear strength. We are interested in bending strengthso let's look at our Air Camper wing to see what's what.Structurally, there are three elements to our wing. Simplifying, of course. Thecentersection is one element, the section of the wing outboard from the cabanesto the lift strut attach points is another, and the part outboard of thelift strut attach points is a third. Of those three, the centersection is themost lightly loaded and the easiest to analyze structurally because it is supportedand restrained at both ends by the four cabane uprights. The next section,from the cabanes out to the lift strut attach points, is more heavily loadedthan the centersection but it, too, is restrained at both ends (by the cabanesat one end and by the lift struts at the other). The outboard-most sectionof wing is the part that has to work the hardest because it is only supportedat the lift strut end and the other end is cantilevered out into thin air.That part of the wing is what needs the most strength in bending, because that'swhat it has to work hardest at.The heavies that Terry flies have wings that are completely cantilevered out fromthe fuselage, so when you are at maximum takeoff weight with full fuel, pax,and baggage and you pull that baby into climb attitude on takeoff, the wingsbend gracefully in an upward sweep out at the tips as they do their hardest work.In a spectacular example of this taken to the extreme, check out the 787Dreamliner's wingtips bending upward about 25 feet at the tips (during testing,of course), here:https://www.wired.com/2010/03/boeing-78 ... x-test/The bending stress is at its maximum at the wing roots of a cantilevered wing,diminishing as you go out spanwise to the tips, where it is zero. So, in theory,we can save weight by tapering the wing spars to follow the profile of thediminishing stress as we go out to the tips, but that adds complexity to thespar construction, and if we also taper the wing chordwise like the heavies are,it means every rib is different from its neighbor and everything is harderto make. So, we build our wing Hershey bar-style with a constant chord and constantspar size for simplicity and ease of construction. Consequently, the wingcentersection is very much overbuilt, the section from the cabanes to thelift struts is still plenty overbuilt, and the outboard section is probably justabout right but progressively more and more overbuilt as you go from the liftstrut attach points out to the wing tips where the bending stress is (theoretically)zero.Bottom line, we analyze the forces in an Air Camper wing where the bending stressis the highest: on the outboard section, where the lift struts attach. Inboardof that, the spars are restrained from deflecting in bending and outboardof that, they are not.Now for the math. Feel free to leave the room quietly ;o)The bending stress in a beam (which our wing spars are) is calculated by knowingtwo things: the moment (which is the product of the lift force on the wing timesthe distance where it acts on the wing), divided by the section modulus.Forget about two of those things for a minute because we are looking for themaximum "strength" of our wing and we know the properties of the wood (or metal)that the spar is made of so we know its maximum allowable stress, and we alsoknow the lift forces on the wing because we are designing it for a certainmaximum gross weight, G-force, and safety factor. That just leaves the sectionmodulus, which is a property of the beam section. It's different for a tube,a rod, an I-beam, a C-section, rectangle, square, bar, whatever. In the caseof a typical rectangular-section wood beam, the section modulus is equal tothe width (thickness) times the height (spar depth) squared, divided by six.As H. Ross Perot used to say during his talks, "stay with me now..." ;o)The amount of stress that the wood in our spar is able to take without failingis essentially constant and is a property of the wood. So, the larger we canget the section modulus of our spar to be, the "stronger" it is (the more bendingstress it can take, which means higher Gs or a higher gross weight, or both).So, lets look at the section modulus. We have two things we can work withto determine it: the thickness and the height. If we double the thickness,we also double the section modulus but if we double the HEIGHT, we increase thesection modulus by a factor of FOUR because the height gets squared in the equation(2x2 = 4). Since we're trying to build our spars as light as we can,why make the spars twice as thick to double the section modulus (but double theweight), when we can do the same thing by simply increasing the spar depth byabout 2 and the weight only goes up by about 40% instead of 100%? In resistingbending force on the spars, you get more bang for the buck by going tallerrather than fatter.So (and this has nothing to do with where you slept last night), your example ofa spar that is 1" thick and 5" tall means that its section modulus is about4.17 but if we make it 3 times that tall, 15", its section modulus skyrocketsto 37.5 and the spar isnt 3 times stronger, its 9 times stronger in bending thanthe 5" tall one. There's that squaring effect at play.But wait, because there are many reasons why it would be impractical to actuallybuild something like that due to buckling from "slenderness" and fiber shearin the web, twisting, and other things. However, the point is that in a wingspar that is subjected to bending loads, depth is everything. I'm not certainof the Riblett airfoil nomenclature, but if the 612 has 12% thickness and thewing chord is 60", the airfoil would be about 7.2" tall at its maximum thicknessso maybe 7" at the main spar. (Terry, how tall are the metal J-3 spars?)For a 1" thick rectangular Riblett 612 spar, the section modulus might be 8.17.The stock unrouted 1 thick Piet spar is 4-3/4" tall so it might have a sectionmodulus of 3.76 and the deeper 612 spar, if it's a rectangular shape likethe Piet's, is then theoretically competent to take more than twice the bendingstress than the stock Piet spar, so maybe (to temper what Wese said aboutthe Air Camper wing spar), maybe the 2-G Piet becomes a 4-G "Super Piet" ;o)All of this is theoretical and none of the above should be taken as a rigorousanalysis of either spar, or of the wing, or anything other than a general discussionto point out that calculated design can sometimes beat eyeball engineering.On the other hand, many things that are exquisitely designed, cannot readilybe constructed on the floor of a wooden barn using hand tools. Thus we havethe timeless and understated technical elegance of the Pietenpol Air Camper,which does what it does very well and without a lot of analysis or re-engineering.If you choose to depart from Mr. Pietenpols design, take your time analyzingwhat you do.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 power, 72x36 Culver propRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Ragwing Ultra-Piet
Pietenpol-List: Re: Riblett to Spar Fit
Original Posted By: "jarheadpilot82"
Not building one, but I do have a set of plans! Very nice airplane, but when Istudied the plans it seemed like just as much work to build one as to build afull-size Air Camper.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 power, 72x36 Culver propRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Riblett to Spar Fit
Not building one, but I do have a set of plans! Very nice airplane, but when Istudied the plans it seemed like just as much work to build one as to build afull-size Air Camper.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 power, 72x36 Culver propRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Riblett to Spar Fit
Pietenpol-List: Re: Ragwing Ultra-Piet
Original Posted By: "cdlwingnut"
I haven't posted up in a while but was able to get out to Utah last fall and geta weeks worth of work in on the new prop. By far this is the largest prop mydad and I have ever built. Needless to say the blank was almost 80 pounds butis much lighter now. Since I still have a lot of finish work to do on it, I haven'tyet weighed it so have no idea what the final prop will weigh.If anyone has ever done a copper leading edge, please let me know details. I'dlove to wrap the leading edge to give it a good durable finish and look correctfor the period.--------I own a Teenie Two, remnants of an Avid, a KR2, hang glider and paraglider as wellas my 1997 Pietenpol Air Camper. I'm also scratch building a Sonerai IIL.As a CFII/MEI I love sharing the gift of flight with just about anyone that willfly with me.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ttachments: http://forums.matronics.com//files/0209 ... ___Subject: Pietenpol-List: Re: Ragwing Ultra-Piet
I haven't posted up in a while but was able to get out to Utah last fall and geta weeks worth of work in on the new prop. By far this is the largest prop mydad and I have ever built. Needless to say the blank was almost 80 pounds butis much lighter now. Since I still have a lot of finish work to do on it, I haven'tyet weighed it so have no idea what the final prop will weigh.If anyone has ever done a copper leading edge, please let me know details. I'dlove to wrap the leading edge to give it a good durable finish and look correctfor the period.--------I own a Teenie Two, remnants of an Avid, a KR2, hang glider and paraglider as wellas my 1997 Pietenpol Air Camper. I'm also scratch building a Sonerai IIL.As a CFII/MEI I love sharing the gift of flight with just about anyone that willfly with me.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ttachments: http://forums.matronics.com//files/0209 ... ___Subject: Pietenpol-List: Re: Ragwing Ultra-Piet
Pietenpol-List: Re: Ragwing Ultra-Piet
Original Posted By: "taildrags"
First, kudos for wanting to give instruction in the piet. I think it would be greatfor any pilot to get time anything with the little wheel in the back whereit belongs and esp. in the piet. as far as earning a pilot certificate in one getting a sport certificat i don'tsee a problem but the private certificat requires 3 hours of flying on instrumentsas well as using navigaton equipment and for the checkride you need an aircraftcapable of being flown by reference to instruments. So for the privatecertificate you will probably need to use something else for part of the trainingand the check ride.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Ragwing Ultra-Piet
First, kudos for wanting to give instruction in the piet. I think it would be greatfor any pilot to get time anything with the little wheel in the back whereit belongs and esp. in the piet. as far as earning a pilot certificate in one getting a sport certificat i don'tsee a problem but the private certificat requires 3 hours of flying on instrumentsas well as using navigaton equipment and for the checkride you need an aircraftcapable of being flown by reference to instruments. So for the privatecertificate you will probably need to use something else for part of the trainingand the check ride.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Ragwing Ultra-Piet
Pietenpol-List: Re: Ragwing Ultra-Piet
Original Posted By: "cdlwingnut"
When I first started working with T-88 I would apply it meticulously and try toclamp it very tightly. After breaking a couple of test joints and working withit more, as well as reading the instructions, I found that the joints shouldn'tbe clamped to hairline invisible and that a little squeeze-out is a goodindication that the joint got filled. Now I'm generous with it and judiciouswith the clamping. It looks awful when you get squeeze-out but you can wipe offthe excess before it hardens, or scrape it off once it cures, or just leaveit alone if it's not unsightly. It doesn't quite cure to invisible, but it alsoisn't a big contrast between varnished wood. Since I'm not a cabinet maker,I like to see the glue joints ;o)Everything that I have read about T-88 is that it adheres to itself quite well,so if after curing you have a gap that you don't like, you should be able tofill it with some more T-88 buttered into the gap. Of course you don't want tobe bridging wide gaps with epoxy if they really just need to be cut out andre-made with a tighter gap, but T-88 is a good gap filling epoxy.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 power, 72x36 Culver propRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Ragwing Ultra-Piet
When I first started working with T-88 I would apply it meticulously and try toclamp it very tightly. After breaking a couple of test joints and working withit more, as well as reading the instructions, I found that the joints shouldn'tbe clamped to hairline invisible and that a little squeeze-out is a goodindication that the joint got filled. Now I'm generous with it and judiciouswith the clamping. It looks awful when you get squeeze-out but you can wipe offthe excess before it hardens, or scrape it off once it cures, or just leaveit alone if it's not unsightly. It doesn't quite cure to invisible, but it alsoisn't a big contrast between varnished wood. Since I'm not a cabinet maker,I like to see the glue joints ;o)Everything that I have read about T-88 is that it adheres to itself quite well,so if after curing you have a gap that you don't like, you should be able tofill it with some more T-88 buttered into the gap. Of course you don't want tobe bridging wide gaps with epoxy if they really just need to be cut out andre-made with a tighter gap, but T-88 is a good gap filling epoxy.--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 power, 72x36 Culver propRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Ragwing Ultra-Piet
Pietenpol-List: Re: Ragwing Ultra-Piet
Original Posted By: "taildrags"
little report on how I am doing, I have the rib jig built and awaiting the arrivalof the 1/4 by 1/4 sticks it takes to built the ribs. I have one half of thefuselage in the jig and have started glueing.I'm looking forward to making my first rib on Monday.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Ragwing Ultra-Piet
little report on how I am doing, I have the rib jig built and awaiting the arrivalof the 1/4 by 1/4 sticks it takes to built the ribs. I have one half of thefuselage in the jig and have started glueing.I'm looking forward to making my first rib on Monday.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Ragwing Ultra-Piet
Pietenpol-List: Re: Ragwing Ultra-Piet
Original Posted By: "cdlwingnut"
cdlwingnut-I know that the Ragwing was designed around a 28-35 HP engine, but what do youhave in mind to power yours with? The Valley Engineering "Big Twin" is way tooheavy and too much power. The two-strokes will work, but are you thinking ofa two-stroke or something like the 1/2 VW? And by the way, where are you located?--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 power, 72x36 Culver propRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Ragwing Ultra-Piet
cdlwingnut-I know that the Ragwing was designed around a 28-35 HP engine, but what do youhave in mind to power yours with? The Valley Engineering "Big Twin" is way tooheavy and too much power. The two-strokes will work, but are you thinking ofa two-stroke or something like the 1/2 VW? And by the way, where are you located?--------Oscar ZunigaMedford, ORAir Camper NX41CC "Scout"A75 power, 72x36 Culver propRead this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: Ragwing Ultra-Piet
The engine I have is a rotax 503, with is at the upper limit of the 28-48hp butthere are a couple of little piets flying with this engine already.oh and i am located in Iowa so a trip to Brodhead may be in the summer plans thisyear. though by ground trasportation or a borrowed airplane.Read this topic online here:http://forums.matronics.com/viewtopic.p ... #467193end of file rakesh