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  • PA1195
    replied
    Hi Dick. I read this first in 1975 and maybe once since so did reread thanks to your thoughtful comments. I'm not an engineer and my landing goal would be to land as slowly and short as possible with a low AOA for best forward visibility. My takeoff goal would be to minimize the takeoff distance. Obstacle clearance requires balancing lift vs drag at a given thrust over a critical distance. Therefore that Vx might require a longer takeoff to achieve the ROC required to top the tree. For Vy retract flaps to minimize drag.

    I've never flow a flapped 23012 plane but have flown others (Beaver, various Cubs, Citabrias, and Cessnas - mainly C-185). Flaps are a tool to use when needed and I've yet to wish I hadn't deployed them. But yes for speed vs power the plain Taylorcraft wing is probably best providing the landing gear isn't the limiting drag - like floats or large 31" Tundra tires for example.

    The stall can be tamed with VG's in my experience to the point of flying nose high with nothing but clouds for view. Washout softens the stall but at some expense of overall lift. That's a personal choice.

    My dislike of the airfoil is that it takes more AOA to create lift over even the common Cessna 2412 (and especially with Sportsman Cuff,) Bellanca's 4412, and Cub's USA-35B mod. Run a C/L plot of 23012 vs the others and compare. It's sometimes a minimal difference but present. Taylorcraft set the wing incidence at 3.8* to minimize L/D in cruise and add lift. Others are set at about half that value (+-2*). They made the wing area large to reduce the loading per unit.

    As weight increases over the original designs 1100-1200# more lift is needed to achieve the same T/O and landing performance (opinion). Yes more power and better prop helps acceleration and climb but comes at a price in balancing CG and increased fuel capacity needed to feed a mission profile. Flaps and L/E devices can be a useful tool in that situation and that's what happened when other manufacturers adopted the airfoil. They wanted both speed and lift and flaps helped them achieve that goal I believe.

    Gary

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  • astjp2
    replied
    Originally posted by otrcman View Post
    Gary,

    Looking at TR-664, it appears that the drag increase at low angles of attack and flaps zero sort of offsets any gain on the low speed end with flap deflected. That, in conjunction with the rather abrupt stall makes the 23012 appear to be a dead end street to me. Perhaps using spoilers to put more weight on wheels so braking effectiveness is improved during landing roll would shorten landing distance just as well as reduced touchdown speed with flaps.

    Dick
    Washout reduces the abrupt stall to a nice flutter

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  • otrcman
    replied
    Gary,

    Looking at TR-664, it appears that the drag increase at low angles of attack and flaps zero sort of offsets any gain on the low speed end with flap deflected. That, in conjunction with the rather abrupt stall makes the 23012 appear to be a dead end street to me. Perhaps using spoilers to put more weight on wheels so braking effectiveness is improved during landing roll would shorten landing distance just as well as reduced touchdown speed with flaps.

    Dick

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  • PA1195
    replied
    Here's some 23012 flap designs: https://ntrs.nasa.gov/archive/nasa/c...9930091739.pdf

    Gary

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  • PA1195
    replied
    Hey Dr. Tim try to get the dimension from the Tern. It's local and I know the pilot Gordon Clark wouldn't mind. I have more pics of the setup but lost your e-mail. Personal it to me and I'll send them.

    I also wonder if the current TCDS holder of the Tern has prints? http://www.interstateaircraft.com/Contact.html

    I assume the upper rear jury strut bracket shown in #10 fastens to the back of the rear spar. From that I can measure the wing hinge back and down distance minus assumed rib depth. On the flap then chord, thickness, hinge location from the LE/TE and distance below.

    Alternatively the pics of the Taylorcraft hinges in #10 show that mod to the aileron hinges. If we assume they took an aileron hinge - mod it - then did the same to an aileron to match the dropped hinge point you'd have most of what needed to CAD the relative positions. Build the brackets and cove area with a built-in upper lip plus any torque transfer compression tubes between the spars like Piper.

    As far as aileron cove design the Cubs (J-3>PA-18) use a similar design to the Taylorcraft. However the Cruisers PA-12>14 uses a sloped up cove like the Tern with a changed Frieze aileron with sharp LE that drops below the wing I guess to tame adverse yaw. When flaps were installed on the PA-18 the sloped cove was used in front of the flaps.

    Gary

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  • Jim Herpst
    replied
    Also the original RV series. RV 4,RV3 RV6 RV8 all use the airfoil. In fact Richard apparently was amazed as a teenager flying both a Cub and A Taylorcraft off the family farm how much faster the Taylorcraft was!......

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  • astjp2
    replied
    For a home built, I can build my own brackets. Just need to figure out where to put the hinge pins. Even if I get a location of the pin from the trailing edge of the flap and the amount it sits below it, I can lay it out in cad. What is interesting is how the pre and post war airplanes aileron coves changed but they both had the leading edges of the ailerons tip up above the wings to counter adverse yaw. This is just an idea for my home built that I am thinking about finishing someday. I have a tandem fuselage and engine mount already on the gear, I would just need to build tail feathers and wings. I am thinking that 80 gallons of gas and an o-200 would give 10 hours of range and 900 miles. 450 out and back. Or an o-320 with a turbo sink could stay at 17.9 for 8 hours would be one hell of a short field long range airplane.

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  • PA1195
    replied
    Click image for larger version  Name:	IMG_0939.jpeg Views:	1 Size:	92.1 KB ID:	182564
    Lowered rear spar and Gurneys. Cub gear to add a frosting.

    Gary
    Last edited by PA1195; 05-06-2019, 03:27.

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  • PA1195
    replied
    Yes Tim I can but I suspect the angles and dangles would not be appreciably better than the Taylorcraft hinge design I linked above. It's far simpler to modify the hinge on an aileron and move the hinge line and torque supports down on the aileron brackets to meet the second pic above. Adding a Piper upper gap fairing is critical versus any Taylorcraft design without. Implementation of deflection could be via an aileron bellcrank and intensive cabling, or a simple cross-fuselage tube connected to the end of the flaps. Flap torsion under air load is a consideration outboard of that. Then simply run a cable to an overhead lever that pulls an eccentric on the cross tube to deflect the flaps. Retraction is via appropriate springs. My theory so far.

    Slips gets us down but unlike flaps at no increased lift only drag. Then we correct the slip and speed can increase. I have many thousands of hours in flapped planes and never had to slip...just lower flaps and establish a stabilized landing configuration to the ground. And takeoffs are shortened.

    Gurney flaps might help too at far lower expense and effort.

    Gary
    Last edited by PA1195; 05-06-2019, 03:24.

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  • astjp2
    replied
    Hey Gary, any chance you can grab some measurements of the arctic tern flap mounts? Something like length behind the spar and the amount it hangs below the flap? Also the flap length? I don't have access to any here and I am playing with a homebuilt project that flaps may be beneficial to.

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  • PA1195
    replied
    I have no experience with them Tim so have no opinion. Below are pics of Taylorcraft's hinge line setup (2nd pic). Basically ailerons with aileron hinges with outboard bottom extensions and supports that create a larger rollback arc that opens a forward slot. On Pre-War wings there's no similar open rear cove to the aileron but it appears Taylorcraft added one to the flap bay to direct air through the slot. Depending on seal at the top between the flap and wing I'd want one like Piper added to the Cubs (PA-14/18) to direct flow aft some over the leading edge. There's NACA/NASA studies on how to optimize that flow and gap on 23012 airfoils.

    Arctic Tern uses a different approach to hinge line and flaps (first pic). It's airfoil design is available in Abott and Doenhoff's Theory of Wing Sections flap design p. 212 2-H I believe. The hinge is more aft on the flap which swings down and back perhaps more than the Taylorcraft design.

    Either would be better than nothing as 4-5 mph lower stall and a nose down attitude at the same or increased C/L with drag as needed would be a fun tool.

    Gary



    Click image for larger version  Name:	IMG_2445.jpg Views:	1 Size:	128.4 KB ID:	182560







    Click image for larger version  Name:	image_10503.jpg Views:	1 Size:	161.1 KB ID:	182559
    Last edited by PA1195; 05-06-2019, 14:26.

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  • astjp2
    replied
    So Gary, do you not like the F-21 flaps?

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  • PA1195
    replied
    Originally posted by otrcman View Post
    Gary,

    I wasn't aware that Cessna had experimented with 23000 series airfoils, and especially that the played with VG's and slots. Can you send me a reference ?

    Thanks, Dick
    Hi Dick nice to meet you. If you look here/linked above ( https://m-selig.ae.illinois.edu/ads/aircraft.html) under Cessna aircraft you'll see several with variations on the 23000 series. It appears the wing thicknesss and typically taper was a blended variation from root to tip. Not surprising if spar and wing support was needed at the fuselage juncture and wash at the tip (how much?) took care of the spanwise flow separation.

    The 23012 is quite similar to their traditional 2412 - comparative plots are available here > http://airfoiltools.com You can overlay both airfoils and compare parameters at various Reynolds Numbers.

    As far as a Caravan there are several locally used for Part 135 ops and I drive by almost daily. The LE enhancements I've seen have been VG's of various size and spacing (depends on if it has a rubber booted or wet weep wing) and a LE generator forward of the aileron and flap junction (https://support.cessna.com/custsupt/...df?as_id=33995).

    They used Gurney flaps on a portion of the outboard flaps (one traditional and sometimes by model one adjacent that's scalloped) plus a dedicated slot forward of the Gurney flapped portion behind the wing spoilers. There's no LE slot and I wasn't clear above about that. Edit: They also add VG's to the upper rear of the horizontal stabilizer to help flow behind and I assume adequate nose down authority from the elevator. I've read they can loose same during icing conditions.

    I still believe a Taylorcraft with a properly designed flap like Interstate Arctic tern used would be an asset. http://www.interstateaircraft.com

    Gary
    Last edited by PA1195; 05-05-2019, 22:47.

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  • otrcman
    replied
    Gary,

    I wasn't aware that Cessna had experimented with 23000 series airfoils, and especially that the played with VG's and slots. Can you send me a reference ?

    Thanks, Dick

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  • PA1195
    replied
    Cessna did lots of mods to keep their variable thickness 23000 series stall speed under 61 knots. Leading edge enhancements that includes a variety of VG's and a couple types of trailing edge Gurney flaps and dedicated slot.

    For the Taylorcraft VG's are available and quick install Gurney flaps might be interesting. There's studies that support their installation on that airfoil. http://www.dept.aoe.vt.edu/~mason/Ma...A2007-4175.pdf

    Gary

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