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Thread: Yamaha Evaluates Slotted Flaps In MotoGP Testing

  1. #1
    Steve Pierce's Avatar
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    Yamaha Evaluates Slotted Flaps In MotoGP Testing

    Very interesting use of split flaps and a good history on their use and the theory behind them.
    https://www.cycleworld.com/yamaha-ev...motogp-testing
    Last edited by Steve Pierce; 02-17-2019 at 09:00 AM.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
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    fobjob's Avatar
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    In theory, the leak of high pressure air in front of the double slotted flap should encourage air molecules to not change direction 90 degrees and exit out the wingtip (40 mph, normally, with factory flaps) and exit out under the trailing edge of the flap....this could be quantitized by measuring the “drop” airspeed before and after the slotted flap addition...
    Has anyone experimented with fences on the underside outboard end of flaps to prevent excess air spillage?


    In theory, theory and practice are the same. In practice, they aren’t....

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    BC12D-4-85's Avatar
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    Quote Originally Posted by fobjob View Post
    Has anyone experimented with fences on the underside outboard end of flaps to prevent excess air spillage?
    Yes both outboard and inboard 7GCBC and PA-18A. Helps. Tried end plates with top and bottom extensions like plates on duster wing ends and single bottom. If installed on one flap the planes rolled away from the modified flap when extended=more lift. Made of lexan they were invisible.

    Edit: On one application (the Cub) I used rivet nuts and screws to hold the plates and the second plain temporary velcro. Now there's Dual-lock tapes which hold even better: https://www.3m.com/3M/en_US/company-...94857497&rt=r3

    The Citabria already had Crosswinds STOL kit with the inboard flap gap sealed with a metal plate so the outboard end was fenced as an experiment.

    Gary
    Last edited by BC12D-4-85; 02-18-2019 at 05:21 PM.
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    courierguy's Avatar
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    I stumbled upon this old thread, looking for something else. I say stumbled, because a couple weeks ago I actively searched on the subject, and came up empty.

    I too have had this in my head for a while now, my Rans S-7S happens to have enough room between the flap and aileron for a flap end plate. AND, the outboard end of the flap is also flat, so easy peasy to slap a plate on there. What say you, BC12D-4-85: extend both top and bottom or just go bottom? 2 or 3 inches, somewhere in there, sounds about right. Good tip on that super Velcro like material.

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    BC12D-4-85's Avatar
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    Experiment. Add one full end plate outboard and see how the plane reacts and if it rolls away any from the wing with the plate when the flaps are deflected due to more lift. Mine extended 1" beyond the top-rear-bottom off the flap. Not sure what's best as far as dimension. Then cut off the top of the plate and see if anything changes. If there's room add one on the inboard end but if the flap is close to the fuselage it may not offer much improvement. Crosswinds STOL just adds a plate that extends sideways to fill the fuselage gap on the 7GCBC. I did this same experiment on a 7GCBC and PA-18A. Worked on both to my satisfaction.

    On the PA-18A I also put polycarbonate sealer plates on the upper flap and aileron hinge openings (slotted to clear the brackets and pushrod) to contain lower high pressure air. Then to finish the job I extended the PA-18 flap cove top seal out over the ailerons to reduce airflow up through that gap. I had good control to 28 GPS and a soft stall. Taped the elevator gaps as well. The wings had VG's and Hendricks Hot Tips but with the wing the same length as stock Piper.

    Made a mistake and sold N1189C to buy a PA-12-180 but that's another story.

    Gary
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    skywagon8a's Avatar
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    Quote Originally Posted by fobjob View Post
    Has anyone experimented with fences on the underside outboard end of flaps to prevent excess air spillage?

    In theory, theory and practice are the same. In practice, they aren’t....
    Quote Originally Posted by BC12D-4-85 View Post
    Yes both outboard and inboard 7GCBC and PA-18A. Helps. Tried end plates with top and bottom extensions like plates on duster wing ends and single bottom. If installed on one flap the planes rolled away from the modified flap when extended=more lift. Made of lexan they were invisible.

    Gary
    Quote Originally Posted by courierguy View Post
    I stumbled upon this old thread, looking for something else. I say stumbled, because a couple weeks ago I actively searched on the subject, and came up empty.

    I too have had this in my head for a while now, my Rans S-7S happens to have enough room between the flap and aileron for a flap end plate. AND, the outboard end of the flap is also flat, so easy peasy to slap a plate on there. What say you, BC12D-4-85: extend both top and bottom or just go bottom? 2 or 3 inches, somewhere in there, sounds about right. Good tip on that super Velcro like material.
    I tried this on my 185. Added rivnuts to the outboard rib of one flap to which an aluminum fence was screwed. The fence protruded 2" above and 2" below the flap. Unlike Gary's results, mine did absolutely nothing. I was expecting perhaps a little more lift at stall which would have been indicated by rolling away from that flap. Nothing, not even a hint.
    N1PA
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    Tim's Avatar
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    Guy I know did this, said it made a little differenceClick image for larger version. 

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    Sent from my Pixel 2 using SuperCub.Org mobile app

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    courierguy's Avatar
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    Just like my tip fences, added because nut plates in the wing tip were already there from building the wings and needing a way to attach to a rotator, trying some out on my flaps, with their flat ends, would be so easy (and cheap) I will probably do so. I like the idea of using Lexan, as I have some scraps already. But then again, the fact that others have already gone down this path, and the idea has not taken off so to speak, makes me doubt the concept a bit.

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    BC12D-4-85's Avatar
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    Adding end plates should be no different that extending the flap a short distance to the fuselage, or sealing any gap with a extension plate like Crosswinds does for Champs. Some like that mod others don't. Has anyone tried one flap extended in and flown to note any change? I doubt it, but?

    To test I slowed the plane and let go of all controls including the rudder, then slowly deflected the flaps. Did that before adding the plates in case there was any asymmetric flap deflection or lift. The plane's got to be self coordinated or it'll mask any change.

    Pete recently did extensive testing with end plating his Cub wing. I gather it was a minimal change and wasn't worth the effort.

    End plating the Citabria's flaps made the most difference - most roll away from the plated end. It was repeatable and both ends were individually tried. I ended up with just a lower extension of about 2" in that case. But the Citabria has a minimal flap to wing cove gap and it's not formed in a smooth curve like Cubs and Cessna's. In fact they closed that gap with a lower seal like some STC's for Cessna's. Rate of climb and speed were their priority. I removed that lower seal before the end plate experiment and went back to stock when selling.

    Experiment and let's learn something.

    GAry
    Last edited by BC12D-4-85; 09-24-2020 at 11:42 AM.
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    skywagon8a's Avatar
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    Quote Originally Posted by BC12D-4-85 View Post
    ..But the Citabria has a minimal flap to wing cove gap and it's not formed in a smooth curve like Cubs and Cessna's. In fact they closed that gap with a lower seal like some STC's for Cessna's. Rate of climb and speed were their priority. I removed that lower seal before the end plate experiment and went back to stock when selling.

    Experiment and let's learn something.

    GAry
    Back in the days when closing the flap gaps on the Cessnas was all the rage, a friend who was a test pilot for Cessna told me a story. The marketing department wanted a model year change on the 206. They asked that the flap gap be smoothed over so they could promote a "new" improvement. So, he did the flight tests. The results were the cruise speed increased by about the width of the radial line on the airspeed indicator or maybe 1 mph. The stall speed also increased by the same amount. The bottom line, it was only a marketing spiel.

    Why did the stall speed increase??? Because as I've stated elsewhere here, the airflow from the bottom of the wing up through the flap/wing slot was no longer aerodynamically clean.
    N1PA

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    BC12D-4-85's Avatar
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    I'll climb out on a limb and suggest the larger and smoother the flap to wing cove flow the less the effect of end plating. Air is more likely to flow through the gap than outboard and around the ends (?) particularly at deflections optimized for lift not drag. I noted that any rolling effect happened at initial flap deflection and then stabilized with more down flaps. Also, the longer the flap outboard on the wing the greater the arm effect if lift is improved any by end plating.

    Gary

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    courierguy's Avatar
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    On a whim, and after reading your suggestion BC12, I took off one of my '57 Dodge inspired end plates, just one, and went flying for a bit over 2 hours this morning. After making a half dozen upslope landings, with partial and then full flaps on the S-7, along with a fair bit of throttle, really hanging it up there right to the absolute edge of a total and complete stall right before touchdown, I could tell zero difference! No roll off to either side....so this tells me that though they look cool, they are worthless. The aero placebo effect had me thinking they helped just a bit the last few months, but it is quite doubtful.

    My next move will be to take the remaining one off, flip it around so it now protrudes down, and using the same attach points put it back on and go fly.

    I have the Lexan for my end plate flap experiment, just need to order some rivnuts, but want to finalize, or not, this wing tip thing first.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  13. #13
    BC12D-4-85's Avatar
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    Great info and experiment! Congrats on taking the time to learn something. It's good to get the existing platform figured out before adding to the configuration. I guess if there was a wind tunnel available and lots of instruments and science someone would write up a report and cash their paycheck.

    I see more plain end wings now than 40 years ago when droopers and extensions were popular in Alaska. When I redid my PA-11 I tested speeds before and after the squared wings and droop tips (Ferguson-Cub Crafters) were restored to the factory bow. I regained aileron control and a little cruise speed but the stalls were the about the same.

    As I mentioned try the flap ends. Add the flaps slowly and see if it rolls some. If not then there's likely no benefit. How about some closer pics of your wing tips and flap ends when you can take some? '57 Dodge eh? Kept them in a straight line on the highway like the old Cadillacs.

    Gary

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