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Thread: Prototype Help

  1. #11
    femmpaws's Avatar
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    Quote Originally Posted by hiflyer View Post
    I haven't cut the block or created any ribs at this point.
    Reduction of the wing span was to increase wing loading, the Ercoupe wing is very light and does cause some stability upset in bumpy air.

    If I recall thye RV's also use the 23012

    I am not opposed to looking at other options, but do plan on maintaining the anti stall/spin of the Ercoupe
    I'm not sure what airfoil Richard used on his RVs I know he told me at one time too. I also remember he talked about using another airfoil at one time years back (something like 30 years ago)

    To keep it anti-stall/anti-spin I would look at any of Ribletts airfoils that have max thickness 25%. Harry says a 15% thick is just about ideal for lift and drag... You just have to decide what camber line you want to use... The high the arc of the camber line the more lift the wing will make also when the lift goes up so does the drag.

    Part of that stability issues in bumpy air is the airfoil and the other is the control stop settings (READ lack of control surface throw, that also makes for lack of control authority when it's really needed) that they imposed to get their anti stall/spin-ness for the Ercoupe.

    Part of me wanted to ask you if you still drove a Model T or Model A??? If not why not? After all they work. The 23012 came out about the same time as the Model A.... Yes better cars have come along over the years as have airfoils so why not use them?

    I have no qualms of using any Riblett airfoil if it fits my needs... The man has the guts to put his name on his airfoils. Can that be said of any of the airfoils that NACA or NASA have put out there? Have any NASA designers put their name with any of the airfoils they say are the next best thing for GA? They almost always use group this and group that... So far everyone that has used a Riblett on their aircraft design are happy with what it does... The same can't be said for NASA airfoils.

  2. #12

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    Big Grin Riblett Wing

    Quote Originally Posted by femmpaws View Post
    What airfoil are you going to be using? Harry Riblett's 30-615 would be a very good replacement for what it had. On my project I'm using his 25-816.5 for it's stall and spin resents as well as the high lift it offers.
    Took the liberty to make a call to the phone # you added to another post and talked to Rich.
    What a refreshing conversation that was, thoroughly enjoyed the time on the phone.
    Well I was going to use the 30-A-618 but after his help and encouragement I have opted for the 25-518, won't need flaps so
    will not need the A(cusp).
    Looking forward to working on the plane again after a year in stall mode, with the help from fellow builders sharing ideas and encouragement I can start again.
    just need to get my shop heater to work now and then I can press on.
    Look forward to more visits with you in the future, thanks for taking the time to encourage and help
    regards from another Riblett fan
    rich
    Last edited by stolflite; 12-05-2011 at 07:05 PM. Reason: poor sentence structure maybe some of this may not be right either lol

  3. #13
    steve's Avatar
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    All the short wing RVs (3,4,6,7,8) use the 23012 airfoil. The RV-9 uses a John Roncz design. The RV-10 uses a Steve Smith design. Regarding stall charateristics - other than an abrupt fall of the nose with little or no warning buffet on the short wings, there's nothing to get up about. Stall recovery is conventional. The RV-9 is more benign - a tiny bit more buffet than the others and hardly any loss of altitude during recovery. The absurdly high deck angle on the 9 is the biggest indicator a stall is forthcoming. I have no stall time in the 10.

  4. #14

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    if you get a chance would like to talk
    pm would do for a start
    rich

  5. #15

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    Stall Characteristics

    Aircraft stall characteristics have little to do with 2D airfoil plots/graphs. Wings are 3D. Planform (aspect ratio and taper ratio) and twist are much larger drivers in the equation. The lists could go on and on about "great" airfoils that stall poorly (i.e. Piper Tomahawk) and poor airfoils that stall well (i.e. Cessna singles). Stall characteristics can be modified greatly with other devices, too, such as VGs, stall strips, etc.

    What's important is that the inboard end of the wing stalls first (to leave the aileron flying). Spin characteristics also have little to do with the airfoil (remember from primary training that the wing must be stalled for the airplane to spin). If you want a little stall warning, a small, properly-placed stall strip inboard will send turbulent air back to shake the horizontal a little before the stall to let you know something is about to happen. As a couple people mentioned, stall resistance/spin proof is in limiting the tail power (not allowing the airfoil to get to stall angle of attack).

    Best example of a point designed (go fast) airfoil is the T-38. It gives the pilot and GIB plenty of time to think about what they are about to do before they stall the airplane.

  6. #16

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    thanks

  7. #17

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    Riblett Airfoils on "Rea"l A/C

    Anybody intersted in a "real" aircraft currently designed with & using a Riblett airfoil should check out the Barrows Bearhawk "Patrol" (two seat version of the original 4-seat Bearhawk). In designing the Patrol Bob Barrows went with a Riblett 30-413.5 airfoil for the constant chord wing on the Patrol. The prototype has been "wrung out" by a very experienced pilot & flight instructor in basic aerobatics and has been found to not have any any "funky" characteristics. There have been several articles written on the Patrol in the general aviation press (not to mention Sport Aviation & the recent February issue of Kit Airplanes). Do a Google search to find any of the numerous websites regarding the Patrol, both the "offical" website & numerous builder websites. There are at least 4 Patrols flying now in addition to the prototype & numerous others near completion. About 250 sets of plans have been sold - I have a set & am currently in the early stages of building myself.

    Only other comment I will make is, while I will readily acknowledge I am not an aerodynamicist, I was (am?) Naval Aviator with a few thousand hours of flying experience in a variety of a/c. I will agree that in the "real world" wings are attached to a fuselage (where they can general turbulence & drag) and have to end somewhere (where the airstream can "slip" off the wingtip). However, even back in the mid-70's when we were going through ground school at Pensacola and learning, FAA regs, navigation, a/c systems & aerodynamics it was generally accepted that unless you were talking about a significantly swept wing, or a tapered wing with reduced chord or profile at the tip, you could treat wing sections as if they were 2-D. I know part of that was there were no computers that could do the calculations at that time to figure out the 3-D aeronautical world, but I'm not even sure that with the development of the Cray computers, etc. that anything has really changed (especially at the usual airspeeds GA aircraft move). Just my two-cents worth on the subject.

  8. #18
    Matt Gonitzke's Avatar
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    Quote Originally Posted by SoCal Ken;11837[snip
    However, even back in the mid-70's when we were going through ground school at Pensacola and learning, FAA regs, navigation, a/c systems & aerodynamics it was generally accepted that unless you were talking about a significantly swept wing, or a tapered wing with reduced chord or profile at the tip, you could treat wing sections as if they were 2-D. I know part of that was there were no computers that could do the calculations at that time to figure out the 3-D aeronautical world, but I'm not even sure that with the development of the Cray computers, etc. that anything has really changed (especially at the usual airspeeds GA aircraft move). Just my two-cents worth on the subject.
    That is not true. Parameters such as lift curve slope, maximum lift coefficient, etc. must be corrected for aspect ratio and other 3D wing properties when converting 2D airfoil data to 3D wing data. No supercomputer is needed, just a few sheets of paper.

  9. #19

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    Quote Originally Posted by hiflyer View Post
    Looking for help in developing a prototype.
    I have the design almost complete all parts are designed and ready to cut, shape. Need someone that is good with metelwork to help build.
    I'm shocked that this turned into a discussion on airfoil selections and NO ONE responded to the original request for someone that is good with metalwork. Good luck hiflyer and I hope you get a lot of help with your new design!

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