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Thread: Performance STOL flap testing

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    WanaBNACub's Avatar
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    Performance STOL flap testing

    When I made the decision to put the PSTOL flaps on I told our engineers that I wanted to do a little unscientific testing to try and see exactly what the real world performance differences are between the Performance STOL, double slotted, Fowler type flap system and the stock flaps. We have heard lots of people that are running them talk about the differences they had experienced. No one we have talked to has regretted the decision to put them on, but I have learned that "some" pilots exaggerate numbers from time to time. They made up a simple inclinometer to hang across the tubes over the back seat and I put a gopro on it to show the exact deck angle in 5 degree increments. In level flight I "zeroed" it by lining up that longer center mark with the pendulum. I also put a gopro on the airspeed indicator to show the touchdown speed. I had put 5 landings on the flaps after we installed them and then 10 landings for the video test. Since this video I have gotten used to flying them more and could improve on those numbers quite a bit. Power on stall speed went from about 30mph at 1600 rpms down to 21mph at 1600. I have had the touchdown speed as slow as 25 now with no wind.

    Last edited by WanaBNACub; 12-17-2018 at 12:30 PM.
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    flyrite's Avatar
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    Just to DANG COOL....Few mod’s make a seat of the pants difference, Lower’d the nose as well as the stall speed. Like you said, When you get comfortable operating at the slower speeds I’m sure you will get even more out of them. Great way to demonstrate the improvement.
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    I can't wait. I am encouraging my Super Cub buddies. I may even do the installation for free.

    Are you using GPS speeds, or just airspeed indicator? We can fly a stock Cub at zero indicated.
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    BC12D-4-85's Avatar
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    One thing significant is the effect on wing lift and pressure distribution with flap retraction at the end (~5:54). Flaps up tail drops now. Not like most Cubs I've owned with stock flaps.

    Gary
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    WanaBNACub's Avatar
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    Quote Originally Posted by bob turner View Post
    Are you using GPS speeds, or just airspeed indicator? We can fly a stock Cub at zero indicated.
    My indicated and gps speeds were almost identical. With a helicopter airspeed it has been very accurate down to at least 20mph.
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    BC12D-4-85's Avatar
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    I changed a PA-18A enough to get stall in no wind level flight near gross to 28 GPS. Four corner trial to correct for any wind - none noted. But I was staring at the clouds with full 50* flaps as the C/P moved forward. No way to land the plane in that attitude on 25" tires.

    Now with these venetian blind flaps the C/P moves aft with deflection and I assume the runway is quite visible at low landing speeds. Excellent!

    Gary
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    spinner2's Avatar
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    Nicely done Cory. You’re enjoying your new job.

    I am envious of that cool sea level air.

    I’d call a 4 mph reduction in touchdown speed (at least 10%) as significant. That will really cut down the landing roll. And the flatter attitude is fantastic.

    How about takeoff performance. Are you seeing an improvement then?
    "Fast is fine, but accuracy is everything." Wyatt Earp

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    Quote Originally Posted by BC12D-4-85 View Post
    I changed a PA-18A enough to get stall in no wind level flight near gross to 28 GPS. Four corner trial to correct for any wind - none noted. But I was staring at the clouds with full 50* flaps as the C/P moved forward. No way to land the plane in that attitude on 25" tires.

    Now with these venetian blind flaps the C/P moves aft with deflection and I assume the runway is quite visible at low landing speeds. Excellent!

    Gary
    Yes, the visibility is definitely the most valuable improvement. You should be able to come in at 28-30 at a flat to maybe 5 degree nose up attitude in a wheel landing and have perfect visibility. My deck angle sitting still or taxiing is around 16 degrees on 35's for a reference.

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    Quote Originally Posted by spinner2 View Post
    Nicely done Cory. You’re enjoying your new job.

    I am envious of that cool sea level air.

    I’d call a 4 mph reduction in touchdown speed (at least 10%) as significant. That will really cut down the landing roll. And the flatter attitude is fantastic.

    How about takeoff performance. Are you seeing an improvement then?
    Yes I am. I love Airframes and the job fits me perfectly! Great company. Takeoff performance is also significantly better. I would guess right around the same improvement. I wish we would have marked off the runway and measured distances for takeoff and landings both. As soon as I pop the flaps at about 30mph I am in the air in ground effect and that tail is up. It comes off the ground much flatter as well.

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    It’s more fun to test them in the front seat than in front of the computer.

    I hope to keep testing them until I can get somewhere close to this level of proficiency. Look at the deck angle. Impressive!

    https://m.facebook.com/story.php?sto...078142483&_rdr
    Last edited by stewartb; 12-16-2018 at 12:00 PM.
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    WanaBNACub's Avatar
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    Quote Originally Posted by stewartb View Post
    It’s more fun to test them in the front seat than in front of the computer.

    I hope to keep testing them until I can get somewhere close to this level of proficiency. Look at the deck angle. Impressive!

    https://m.facebook.com/story.php?sto...078142483&_rdr
    I totally agree. And I am very jealous of those long flaps you guys have. It’s incredible what they can do and stay almost flat!

  12. #12
    www.SkupTech.com mike mcs repair's Avatar
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    Speaking of long flaps. I know of the -12 STC. but what about on an -18? Is there an STC? Seen them on a few. One I got done as a field approval (which is not the right way). Is there an STC for -18??? Well the Dakota wings come with them...


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    WanaBNACub's Avatar
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    The only current legal long flap for an 18 that I know of is the Dakota wing and several field approvals as well.
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    I thought we were talking about double slotted Fowler flaps that are STCd?

    Sure, a stock Super Cub can be flown at 25 indicated and less than that ground speed. Deck angle is 45 degrees, and it is still going up. Did it today. Not close to the ground.

    But a stock Super Cub stalls around 40 in the 3-point attitude. It would not surprise me at all to see 25 mph with Fowler flaps as a 3- point stall speed.

    I cannot believe Husky didn't go that route.
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    If you leave power on 1700 RPM a well rigged cub will fly at 36-37 in ground effect but it is not quite 3 point attitude. The tailwheel is 1-1 1/2 ft below 31 inch bushwheels with 3 inch gear. As bob pointed out the deck angle is pretty severe and that in turn makes spot landings harder. The new flaps not only help the deck angle but also slow the plane down. They will become the next thing on the list behind a Borer prop and bushwheels.
    DENNY
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    They've been the next big thing for several years!

    Has anyone fitted these flaps to a Carbon Cub wing yet? When deciding on my exp Cub direction Keller flaps were a big consideration. Mitch at CC told me it couldn't be done but I don't recall why. I'd think where there's a will, there's a way. Anyone done it?

    The big sell for myself was what long Pstol flaps do for a Cub with slats. No more nose to the sky attitude. It was the game changer. I knew I wanted the flaps. I didn't know the flaps would facilitate the slats.
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  17. #17

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    A guy I know of in Washington has Keller flaps on his Carbon Cub. I'm sure Cubcrafters has his info.
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    Did not know the CC had slats. One of my dreams is to fly the Dakota slotted wing - slats would be even better, but it seems to me that things get complicated quickly with movable slats.

    Surely someone is doing slots and Fowler flaps?
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    After watching that video it took me thirty minutes to wipe all the drool off of my computer. I bet these flaps would help with viability on my cub that has the thrust-line kit on it which makes it harder to see over the nose.

    Eddy
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  20. #20
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by bob turner View Post
    - slats would be even better, but it seems to me that things get complicated quickly with movable slats.

    Surely someone is doing slots and Fowler flaps?
    Only installed one set, but it was rather simple. Lay strait edges under wing, set slays on straight edge and drill holes to screw on. We went extra mile and installed nut plates then. But most are just pk screwed into wing. Then open them 1 “ and drill and install a stop bushing.



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    flyrite's Avatar
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    Once you know the ratio of gap to the Venturi that you want, as well as if you want the Slat L.E. Flush or lower than the wings , Like Mike said , Just a matter of putting them on square and making sure where your mounts are can carry The loads. Then you’ll forever be a believer in them being one of the single best add on mods you can do!

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    Olibuilt's Avatar
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    What approximate degree those flaps are aiming for?? 80 degrees, like the bottom drawing, look like a lot...







    Click image for larger version. 

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    Cuzoom is also not shy on degrees...














    How much is too much ?????

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    Performance STOL Flaps safe on nose heavy amphibious Cub?

    Greetings,

    We have a CC/PA18-180. Half it's hours are spent on amphibs, the other half on skis or 35". The latter is driving the desire for these flaps, but the former drives this question....

    Has anyone had trouble with an already nose heavy Cub, on amphibious floats, with these flaps? Neither Wip, nor Airframes, will attest to anything along these lines.

    Thanks, and Merry Christmas!

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    Quote Originally Posted by Olibuilt View Post
    What approximate degree those flaps are aiming for??

    How much is too much ?????
    I guess that depends on how long the flaps are. My initial target measured at the aft surface was 70*. My current ratchet has 4 notches at 15-30-45-55. My preference is 45* but I may learn to like 55* in some conditions. To pull my handle to 70* would take considerable effort. I doubt it would be worth doing but I may try it. I need to cut a new ratchet arch. Might as well cut two or three and play with different notches.

    What does the STC allow for max flaps?
    Last edited by stewartb; 12-17-2018 at 08:06 PM.
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    I think most amphib Cubs are out of the forward CG envelope without ballast. They seem to fly ok. I personally did not care for the CC 180 Cub. Way too heavy.

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    Quote Originally Posted by stewartb View Post
    I guess that depends on how long the flaps are. My initial target measured at the aft surface was 70*. My current ratchet has 4 notches at 15-30-45-55. My preference is 45* but I may learn to like 55* in some conditions. To pull my handle to 70* would take considerable effort. I doubt it would be worth doing but I may try it. I need to cut a new ratchet arch. Might as well cut two or three and play with different notches.

    What does the STC allow for max flaps?
    The STC states 52 degrees for max. I know of lots of experimental cubs running way more than that. You just have to watch for it blanking out the tail if you go too extreme. I have only heard of a few instances of that so far though.
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    I'm not sure more is more. At least in my plane, but there are lots of variables. It's all fun.
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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by WanaBNACub View Post
    .. You just have to watch for it blanking out the tail if you go too extreme.
    which has lead me to think before..... if a split(funneled through) design works so good for a flap, WHY NOT a split design rudder and/or elevator...

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    RVBottomly's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    which has lead me to think before..... if a split(funneled through) design works so good for a flap, WHY NOT a split design rudder and/or elevator...
    I've been thinking the same thing....It's probably a dangerous habit, but fun.

    Seems like it would be effective with an airfoil shaped stabilizer and the proper curve leading into the elevator.

    But I get hung up on making it effective in two directions.
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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by RVBottomly View Post
    I.

    But I get hung up on making it effective in two directions.
    Not the SAME SLOT for both directions, adjacent?


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    BC12D-4-85's Avatar
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    Seal the elevator and rudder gaps first and test. I have some and they help.

    http://store.cubcrafters.com/Foam-Ga...18_p_1298.html

    https://www.aircraftspruce.com/catal...?clickkey=6978

    Gary
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    Quote Originally Posted by RVBottomly View Post
    I've been thinking the same thing....It's probably a dangerous habit, but fun.

    Seems like it would be effective with an airfoil shaped stabilizer and the proper curve leading into the elevator.

    But I get hung up on making it effective in two directions.
    I believe Doug Keller produced an airfoil stabilizer in an attempt to solve a tail buffet some early flap customers were experiencing. I don’t know whatever became of the stabilizers or the buffet. I haven’t heard anything about that for a few years.

    And with a quick search? Here you go. Read post #16 in particular.
    http://www.supercub.org/forum/showth...tal-stabilizer
    Last edited by stewartb; 12-18-2018 at 08:13 AM. Reason: spellen

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    Steve Pierce's Avatar
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    I have gotten a little stick shake when slow on one of the 3 sets I have installed so far. Not as much as I have felt on the Dakota wing with the long flap. Not a big deal but you just feel it a little. The installation instructions say 50.5 degrees +/- 4 degrees. The bottom of the wing is somewhat concave so it is a bit subjective. I use a long straight edge between the leading edge and false spar and zero my digital level on that. I have been getting between 55 and 60 degrees but then when you put a simulated wind load on the flap you get within the spec. The last one I did I was flying the approach at 38 IAS and 35 on the GPS without much wind At all and it was solid. I would really like to try on my Super Cub because I am pretty intimate with it but it is just not in my budget. One thing I did notice was when doing stalls and when it breaks you are way nose down staring at the ground. It breaks straight but it is a lot different than a stock flap in the stall. I just finished my third install with a fourth set waiting. I have tweaked the installation procedure and will post about the way I have been doing it with a lot of pictures when I get some time.








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    Quote Originally Posted by Sonshine View Post
    Greetings,

    We have a CC/PA18-180. Half it's hours are spent on amphibs, the other half on skis or 35". The latter is driving the desire for these flaps, but the former drives this question....

    Has anyone had trouble with an already nose heavy Cub, on amphibious floats, with these flaps? Neither Wip, nor Airframes, will attest to anything along these lines.

    Thanks, and Merry Christmas!
    First of all, is this a CC-18-180, or a PA-18, according to the airworthiness certificate? The difference being that these flaps aren’t approved on the CC-18-180, which was certificated by Cub Crafters, not by Piper.

    Second, all amphibious float equipped airplanes tend to be forward CG, unless ballast has been added aft. Personally, I wouldn’t add permanent ballast aft.....”install” some survival gear back aft. Now your “ballast” at least may serve additional function.

    The CC-18-180s I have flown were both heavy and forward CG, even on wheels.

    MTV
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  35. #35

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    Quote Originally Posted by Sonshine View Post

    Has anyone had trouble with an already nose heavy Cub, on amphibious floats, with these flaps? Neither Wip, nor Airframes, will attest to anything along these lines.

    Thanks, and Merry Christmas!
    What trouble would you anticipate? My Cub is nose heavy/forward CG. Even before I figured out that I needed to add aft weight to calm the plane in cruise? Slow flight with these flaps was a joy. Unless you get critically slow you'll have enough elevator authority to round out and you can always limit your flaps to less than full when on floats. I doubt you will, though. On a standard Supercub with standard wings I always figured the best place for PStol flaps would be on floats.

  36. #36
    txpacer's Avatar
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    I've got a few hours on my flaps, and I like them. Mine went on during a major rebuild so I can't do a direct comparison, but the claimed 4-5 mph reduction feels about right. I've been getting some buffet while slow, probably from the flaps going all the way to the fuselage. Nothing major, just noticeable.

    Now I'm playing around with different takeoff techniques. So far, I like accelerating three-point then popping the flaps without getting the tail up first. It just jumps off the ground. Thrustline seems to compliment these flaps well.
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  37. #37
    WanaBNACub's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    which has lead me to think before..... if a split(funneled through) design works so good for a flap, WHY NOT a split design rudder and/or elevator...
    That would be interesting!
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  38. #38

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    Did Airframes get the airfoil tail design with the flap purchase or did Doug hold on to that? I’m surprised there isn’t more chatter about it.

  39. #39
    WanaBNACub's Avatar
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    Quote Originally Posted by stewartb View Post
    Did Airframes get the airfoil tail design with the flap purchase or did Doug hold on to that? I’m surprised there isn’t more chatter about it.
    No, Doug Keller still holds that
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  40. #40
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    I think these flaps are great! I have the 8 1/2 ft Doug Keller flaps on my Experimental Cub with his airfoil tail. Zero buffet with full power-on stalls with 31 in. ABW, Micro VG's and extended wings. Touch down speeds on the GPS with no wind and light on the fuel at 5000 to 6000 ft. elevation has been around 27 MPH full stall landings around 40 degrees F. Bringing it in with a little bit of power on the approach to touch down. At full flaps they are about 80 degrees down and they blow back about 5 degrees in flight. Be cautious, when making these improvements to slow down our airplanes to make them fly slower, you also lose aileron and rudder effectiveness at slow speeds. It's a lot of fun to go out and fly these airplanes in a no wind conditions, but as the wind picks up I carry a little more speed for controllability. When a gust of wind hits you and drops a wing, you still have control.
    Last edited by mountainflier; 12-20-2018 at 02:09 PM.
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