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Re: Airfoil Question

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  • Dan Leech
    To all that replied, thank you !! I am still trying to digest all of the information that I received. One thing I realize is that I didn’t give enough
    Message 1 of 16 , Mar 1, 2010
      To all that replied, thank you !! I am still trying to digest all of the information that I received. One thing I realize is that I didn’t give enough information as to the WHY of the project, so if I may, here goes…
       
      I am the VP of the local EAA Chapter. We have a good bunch of guys, but lacking motivation. We have about 8 currently building projects, with the remainder just talking about it. Seems like pancake breakfasts and who’s turn is it to bring the donuts are the main concerns.
       
      A few years back I downloaded and printed out the plans for Mike Sandlin’s Goat, brought them to a meeting and presented them as a possible chapter project. At first there was more interest than I expected, but the discussion turned to liability, and it went down hill from there, to the point that the project was rejected. Every attempt to discuss a chapter project seems to go the same direction.
       
      Now, as a victim of the economy, I lost my job of 25 years, I have some spare time… LOL. I was browsing my set of Flying and Glider Manuals, and the Penguin Practice Plane caught my eye. I thought that this might be a project that wouldn’t raise liability concerns since it will never leave the ground. And it might be fun to play with. So, the first step is to take the information presented in the article and draw the plane into a CAD format (also helps to keep my CAD skills sharp). Once I am finished with the plane As-Is, I want to make some improvements using more modern methods and materials.
       
      One item I’m just not sure about is the airfoil. There are no ordinates in the article, and no particular airfoil is mentioned. The airfoil represented seems to be a bit thin, looks like it could be much less than 10% thick. I thought I would ask what some others thought on the subject.
       
      The finished plane would mirror the basic dimensions from the article. I might widen the fuselage a bit, 18” seems a tad narrow. I would like to convert the wood fuselage to aluminum tube and gusset construction along with the tailfeathers, and change the wings to a ladder type aluminum tube structure. But that is all still to be determined.
       
      So, I’m not crazy… LOL. The idea of building a flightless bird has merit, maybe just an exercise in futility, but it gives me something to do while I wait for spring to finish my A-Plane project.
       
      Thanks for all the input…
      Slow And Steady
      Dan LeechAlliance, Ohio
    • rexnstudio@aol.com
      hey Dan, Sounds like a worthwhile project. Done in aluminum it would go together quick and you could teach / learn the disciplines of a/c construction as you
      Message 2 of 16 , Mar 1, 2010
        hey Dan,
        Sounds like a worthwhile project. Done in aluminum it would go together quick and you could teach / learn the disciplines of a/c construction as you went. My opinion on the airfoil choice would be build a bunch of symmetrical ribs from light ply or foam, and incorporate them into a wing plan that offers just enough control in the roll axis to accomplish the "penguin mission".
         
        Thought you'd have that A-plane done by now..... oh I know, you're waiting on me to finish my glider first.
        Rex



        -----Original Message-----
        From: Dan Leech <danl239@...>
        To: Airchairgroup@yahoogroups.com
        Sent: Mon, Mar 1, 2010 10:26 am
        Subject: [Airchairgroup] Re: Airfoil Question

         
        To all that replied, thank you !! I am still trying to digest all of the information that I received. One thing I realize is that I didn’t give enough information as to the WHY of the project, so if I may, here goes…
         
        I am the VP of the local EAA Chapter. We have a good bunch of guys, but lacking motivation. We have about 8 currently building projects, with the remainder just talking about it. Seems like pancake breakfasts and who’s turn is it to bring the donuts are the main concerns.
         
        A few years back I downloaded and printed out the plans for Mike Sandlin’s Goat, brought them to a meeting and presented them as a possible chapter project. At first there was more interest than I expected, but the discussion turned to liability, and it went down hill from there, to the point that the project was rejected. Every attempt to discuss a chapter project seems to go the same direction.
         
        Now, as a victim of the economy, I lost my job of 25 years, I have some spare time… LOL. I was browsing my set of Flying and Glider Manuals, and the Penguin Practice Plane caught my eye. I thought that this might be a project that wouldn’t raise liability concerns since it will never leave the ground. And it might be fun to play with. So, the first step is to take the information presented in the article and draw the plane into a CAD format (also helps to keep my CAD skills sharp). Once I am finished with the plane As-Is, I want to make some improvements using more modern methods and materials.
         
        One item I’m just not sure about is the airfoil. There are no ordinates in the article, and no particular airfoil is mentioned. The airfoil represented seems to be a bit thin, looks like it could be much less than 10% thick. I thought I would ask what some others thought on the subject.
         
        The finished plane would mirror the basic dimensions from the article. I might widen the fuselage a bit, 18” seems a tad narrow. I would like to convert the wood fuselage to aluminum tube and gusset construction along with the tailfeathers, and change the wings to a ladder type aluminum tube structure. But that is all still to be determined.
         
        So, I’m not crazy… LOL. The idea of building a flightless bird has merit, maybe just an exercise in futility, but it gives me something to do while I wait for spring to finish my A-Plane project.
         
        Thanks for all the input…
        Slow And Steady
        Dan LeechAlliance, Ohio

      • Doug i
        ... Since you don t have to worry about glide ratio or sink rate or stall characteristics or any of that stuff it seems to me that you would want a high lift
        Message 3 of 16 , Mar 19, 2010
          --- In Airchairgroup@yahoogroups.com, Dan Leech <danl239@...> wrote:
          >
          > I am playing with the idea of building a Penguin practice plane, just for fun. I am working on updating the version in the EAA Flying And Glider Manual. Don't want to fly just get the thing light on it's single wheel. I'm looking at a 17'-6" span with a 36" chord. What would be a good airfoil that would give the max lift at extremely slow speed?
          >

          Since you don't have to worry about glide ratio or sink rate
          or stall characteristics or any of that stuff it seems to me
          that you would want a high lift airfoil (to minimize wing area)
          and a simple one to minimize complexity in construction. You
          don't have any reason to care about lift to drag ratio, unless
          you're going to harness people to tow it along the ground.

          Perhaps you should consider a flat plate with a high angle
          of attack.
        • LR
          Flat plate has lousy max lift. Curved plate would be much better, but hard to do structurally, though perhaps you could use a lot of wires. Profili claims that
          Message 4 of 16 , Mar 19, 2010
            Flat plate has lousy max lift. Curved plate would be much better, but hard to do structurally, though perhaps you could use a lot of wires.

            Profili claims that if you take a 43018 or the FZX airfoil I mentioned earlier, keep the top, and slice off the bottom flat with only a very small leading edge radius, you will get a lot of lift. In fact, the flattened fzx might make an excellent airchair airfoil down to about a Cl of 0.6, when it starts to get draggy. The flattened 43018 would be good down to a CL 0f 0.7. You could probably add more lift with flaps.
            --- In Airchairgroup@yahoogroups.com, "Doug i" <doug_in_gbmd@...> wrote:
            snip
            >
            > Since you don't have to worry about glide ratio or sink rate
            > or stall characteristics or any of that stuff it seems to me
            > that you would want a high lift airfoil (to minimize wing area)
            > and a simple one to minimize complexity in construction. You
            > don't have any reason to care about lift to drag ratio, unless
            > you're going to harness people to tow it along the ground.
            >
            > Perhaps you should consider a flat plate with a high angle
            > of attack.
            >
          • rexnstudio@aol.com
            what about cutting down a pair of pranged up second-hand wings... or using just one panel from a wreck.... and build on that. seeing as it is for an EAA
            Message 5 of 16 , Mar 20, 2010
              what about cutting down a pair of pranged up second-hand wings... or using just one panel from a wreck.... and build on that.
               
              seeing as it is for an EAA chapter, its a shame that you cant make a wing out of pancakes, but I digress.
               
              rex



              -----Original Message-----
              From: LR <lincolnr@...>
              To: Airchairgroup@yahoogroups.com
              Sent: Fri, Mar 19, 2010 11:49 pm
              Subject: [Airchairgroup] Re: Airfoil Question

               
              Flat plate has lousy max lift. Curved plate would be much better, but hard to do structurally, though perhaps you could use a lot of wires.

              Profili claims that if you take a 43018 or the FZX airfoil I mentioned earlier, keep the top, and slice off the bottom flat with only a very small leading edge radius, you will get a lot of lift. In fact, the flattened fzx might make an excellent airchair airfoil down to about a Cl of 0.6, when it starts to get draggy. The flattened 43018 would be good down to a CL 0f 0.7. You could probably add more lift with flaps.
              --- In Airchairgroup@ yahoogroups. com, "Doug i" <doug_in_gbmd@ ...> wrote:
              snip
              >
              > Since you don't have to worry about glide ratio or sink rate
              > or stall characteristics or any of that stuff it seems to me
              > that you would want a high lift airfoil (to minimize wing area)
              > and a simple one to minimize complexity in construction. You
              > don't have any reason to care about lift to drag ratio, unless
              > you're going to harness people to tow it along the ground.
              >
              > Perhaps you should consider a flat plate with a high angle
              > of attack.
              >

            • rexnstudio@aol.com
              yea whatever ... From: gypsyinvader To: Airchairgroup@yahoogroups.com Sent: Sat, Mar 20, 2010 5:26 pm Subject: [Airchairgroup] Re:
              Message 6 of 16 , Mar 20, 2010
                yea whatever



                -----Original Message-----
                From: gypsyinvader <garrywarber@...>
                To: Airchairgroup@yahoogroups.com
                Sent: Sat, Mar 20, 2010 5:26 pm
                Subject: [Airchairgroup] Re: Airfoil Question

                 

                t-rex,

                Hey... dint I get a pungent notice on humor around here??
                Garry

                We need more flying vids of "airchairp" to watch, us armchairp flyers...
                :-)

                seeing as it is for an EAA chapter, its a shame that you cant make a
                wing out of pancakes, but I digress.
                rex

              • LR
                Second hand wings sound like a good idea to me. How about from a two place ultralight that someone forgot to turn into an ELSA, or whatever they call it,
                Message 7 of 16 , Mar 20, 2010
                  Second hand wings sound like a good idea to me. How about from a two place ultralight that someone forgot to turn into an ELSA, or whatever they call it, before the deadline.

                  As for the pancakes, just make them with extra fiber, less butter, and saturate with epoxy when they're done.
                  --- In Airchairgroup@yahoogroups.com, rexnstudio@... wrote:
                  >
                  >
                  > what about cutting down a pair of pranged up second-hand wings... or using just one panel from a wreck.... and build on that.
                  >
                  > seeing as it is for an EAA chapter, its a shame that you cant make a wing out of pancakes, but I digress.
                  >
                  > rex
                  >
                  snip
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