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  1. #1

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    Looking for Airfoil advice

    I am working on the S2-Tracker. The root airfoil is a naca 63-420 and the tip is the naca 63-415. I have found the tip airfoil but unable to locate the Root 63-420 in a DAT file. So, I am looking for Other airfoils that I can use. All suggestions would be welcomed ...

    Thanks
    Mike

  2. #2

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    RE: Looking for Airfoil advice

    Will this work? I found it using a Google search on the airfoil number. If you go up one level on the link you will find many NACA airfoils listed.

    http://ckw.phys.ncku.edu.tw/public/pub/Notes/Languages/Fortran/Resources/www.pdas.com/sections6.htm#63-415

  3. #3

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    RE: Looking for Airfoil advice

    Thanks for the link but it doesn't show the 63-420. So what other airfoils are available for high lift?

  4. #4
    limeybob's Avatar
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    RE: Looking for Airfoil advice

    NACA 63a420 createdwith Profili-Pro
    Rename the .txt file to .dat

    limeybob
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    Laser-Design-Services
    JetMach manufacturer

  5. #5

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    RE: Looking for Airfoil advice

    Limybob,
    Thanks for the help, the file worked!!!!

    So now I am trying to decide if I should increase both root and tip chords to add square inches and lower the wing loading. The full scale has a narrow wing with the root chord at 9'11"(119") and the tip chord is 48", wingspan is 68'4" (820"). I am scaling it down to 1/10th scale giving me a root of 11.9" and the tip at 4.8" with a wingspan of 82". If I add .500 to both chords this would add 41 square inches. Will this work or would also need to increase the rear stab as well?

    When I try to "Click here to upload images and files"! , or "BETA: Multi-File Upload with Progress Bar", nothing happens. Is RCU having problems?

  6. #6
    tdstaf's Avatar
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    RE: Looking for Airfoil advice

    I would leave it. With it being 678 Sq in the plane would fly well heavy at 9.5 lbs and that would give you a wing loading of about 32oz a sq ft. If your careful you might get it down to 7.5 -8 lbs at 25-27 oz sq ft . It has a nice high aspect ratio wing which will help with lift.

    Tim
    Who says scale warbirds have to be GIANT.

  7. #7
    limeybob's Avatar
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    RE: Looking for Airfoil advice

    Yes.

    Don't forget to make sure the wing has washout.

    limeybob
    Laser-Design-Services
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  8. #8
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    RE: Looking for Airfoil advice

    If you're not OCD over ever last scale detail then a switch to the Selig 8036 and 8037 combo might be a wise choice. This pair was developed to fly well and in a friendly manner even if the wing loading is a little higher than ideal. And at 16% thick it promises to do better at model related size and airflow than the overly thick, for a model, 20% thick airfoil.
    Witty saying to be plagarized shortly.....

  9. #9

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    RE: Looking for Airfoil advice

    I played with enlarging the wing chord but decided to leave it alone. Not that OCD over the scale thing semi/stand off scale is fine with me. Thanks for the Selig 8036 and 8037 idea. I will look at that tonight!!!!

  10. #10
    Moderator BMatthews's Avatar
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    RE: Looking for Airfoil advice

    I forgot to mention the history behind this pair of airfoils. The stories I've seen suggest that they came from Top Flite contracting Michel Selig for airfoils which would fly well with their larger scale models. The resulting 8036 and 8037 are reported by many to fly well and have relatively friendly stall charactaristics when flown on models with higher wing loadings than some other options. So basically their use could well salvage a moderately overweight model's flying habits where some other historically popular choices would have handling issues.

    Note that we're talking about a LITTLE advantage here. It won't take a terminally overweight model and make it fly like a butterfly. Too heavy is still too heavy. It's just that the Selig options, if done well and with accuracy for shape, can make the marginally heavy loading situations go from dissapointing to acceptable.

    On the other hand if you can keep your Tracker's weight down to the "happy zone" for that size of model then the Selig airfoils should or will work for you just as well or slightly nicer than the "usual" NACA 2415 or similar.
    Witty saying to be plagarized shortly.....

  11. #11

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    RE: Looking for Airfoil advice

    I entered the Selig 8036/8037 into the cad program and did a comparison to the Naca 63a420/ 632-415. Based on a 12" root the Naca is 2.48"(63mm) tall and the Selig 8036 is only 1.96"(50mm) tall.

    My question then is will I have less lift with the thinner Selig 8036 airfoil? Also, I can modify the Selig to make it thicker but not sure how that would effect flight?



    Thanks
    Mike

  12. #12
    Moderator BMatthews's Avatar
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    RE: Looking for Airfoil advice

    No. The maximum achievable lift isn't a direct function of the thickness. Instead it's related to how well the air can remain stuck to the profile before it separates at the stall angle.

    Normally thicker airfoils delay the stall. But at some point up around 15 to 17% this turns back on itself and thicker isn't better from that aspect.

    Selig and his associates design their airfoils using software that predicts the flow over the shape so that pressure gradients are optimized and are as smooth as possible. This in itself aids in delaying the onset of airflow separation and stall. So if you alter the thickness from stock then it's no longer the same airfoil. Any major changes are far more likely to end up hurting than helping. So it's entirely possble, likely even, that at OUR size and speed that the Selig airfoil will outperform the NACA airfoil.

    You only need as much lift as the model weighs in any event. During normal flying the wings are generally loafing along at a small fraction of the lift they CAN produce. It's only when flying slow or during high G maneuvers like looping tightly or steep bank turns that the wing is asked to generate lift values that get up near the stall point.

    If you want to get technical on all this download and install Xfoil or XFLR5, which has Xfoil or something like it embedded, and test the Selig and NACA options for yourself at typical model size reynolds numbers.

    Keep in mind as well that if you plan on installing flaps to use for takeoff and landing that the native shape lift to drag curves won't mean much. When you angle the flaps the airfoil changes again and you need to write up the coordinates for the flap being down at various angles and run them through the software as a whole new airfoil.
    Witty saying to be plagarized shortly.....

  13. #13

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    RE: Looking for Airfoil advice

    The scale airfoil is a 63A, there is a difference. In this case, you will get more lift out of the scale airfoils, but the Selig 8036 does have a slightly mushier stall, note the flatness at high angle of attack. You might consider using about 3 degrees of washout.
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  14. #14

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    RE: Looking for Airfoil advice

    With that Cl wished for, why not just use the Clark Y? Its flat on the bottom and easy to build. If you want a higher cl than 1.3 I can name you a few, but am having a mind fart right now and would have to look the number up. Cl of 1.6 and 1.7 range depending on reynolds number that is essentially what you are building but with more undercamber than what you have postulated. I can find it for you with data for its shape, but complete mind toot right now, CY625 or something like that. Its a great biplane airfoil for highlift with a gentle roll off as I recall. It has been used on several major sailplanes(the real ones). Of course there are higher Cl airfoils as well in the Eppler 423 and Selig s1223 of greater than 2.1.

  15. #15

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    RE: Looking for Airfoil advice

    I totally understand the mind farts!!! I would be interested in looking into the other airfoils when the mind returns. Also, I will check out the Eppler 423 and Selig s1223 airfoils....

  16. #16

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    RE: Looking for Airfoil advice

    Ok, found it. FX 63-137.

    Of course a standard ol' Clark-Y with flaps generates cl of 2.2 or greater depending on reynolds number and flap used so... Easy to build as it would be moldless with its flat bottom but in flap orientation would create more drag, but that is mighty nice on landing so...

    PS. Get that spinner larger(no idea what spinner size you are thinking of already, just an FYI) You will increase thrust dramatically especially if you can cover 4 inches on a 12" or 13" propeller. Ie will go from say 7-8lbs thrust up to 9lbs thrust. IE 60 sized engine. 90 would want a 5" maybe 6" for a 14+++ inche propeller.

  17. #17
    Moderator BMatthews's Avatar
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    RE: Looking for Airfoil advice

    All this talk about the high lift airfoils! Why?

    You only need the higher lift values at landing and takeoff speeds where the lower flying speeds force the need for higher Cl values from the wing. But you can get help for that by using the scale size flaps to increase the camber. The rest of the time while flying at typical speeds and avoiding the steepest bank and yank style turns your wing will be operating at low to mid level Cl values.
    Witty saying to be plagarized shortly.....

  18. #18

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    RE: Looking for Airfoil advice

    Flaps and spoilers, yuppers. Thus, my comment up thread about simple ol' Clark-Y with flaps.

    Not to mention they are a huge help on landing. Assuming of course that you have the runway length where the extra drag on takeoff is not a problem.

    I have no idea what an S2-Tracker is, but it seemed he wanted to lift a lot of weight... The Wortmann airfoils with the cl of 1.6+ are used on the central section roots of major sailplanes. 2 reasons. 1) High lift where most of the weight is 2) High volume in the wing allowing a high section modulus for the wing root spar, or double spar setup. Well there are other reasons, but...

    If he wanted a REALLY high Cl, could name a few giving cl 3.5+, but you won't find empirical data for low Re numbers on the web.

    Got me. Just use the UiUC database in the sticky at the top of this thread. Download, peruse, ask questions on how to apply said data and move on.

    Enjoy!


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