Experimental Cubs & Extreme Stol Devices, Flaps,slats,sl

Coyote Ugly, to what effect would you put them on bottom? Google "turbulator", the glider folks use a tape strip with 60 degree angles (works like VGs) to reduce separation at key areas. If you wanted to maintain the airflow ahead of the flaps that would be interesting to try. Our cub wings have a gap seal on top of the wing that, as SpainCub noted, directs airflow over the flap when deployed to keep it attached. At higher angles of attack I don't think there is an issue with air staying in contact with the underside of the wing. One thing I thought of trying is using turbulator tape on the flap's top or just ahead of the gap seal on top of the wing.

I was thinking more air going through the gap, and trying to keep it attached. Wondered if anyone had tried it.

Hello Pops

Love the new red bird, but you don't need no flaps to make that thing land short ;-)!!!!

Ok, so for a cub, what you get is a plain flap, so all you are doing when you pull on the flap lever is increasing the camber of the airfoil (like all flaps)... Piper's design was not intended to perform like a slotted flap albeit, what you got was some extra airflow over the flap, and that hit the tail and made it shake, thus the flap gap was born, to reduce that turbulent airflow that hit the tail.

On a given cub, test the with or without the flap gap, and you should see very similar performance for the same bird... (albeit you are making it more draggy with out it, and it could be a desired attribute for STOL but you get the hakes and it is not too comfortable)

Moving on, what I have been considering is building a slotted flap... here is the tested numbers vs normal flaps.




As you can see, a plain flap gives you two things, better Cl at a given alpha (AoA) and retarding airflow separation.


I came across this interesting graph, I am posting it for argument sake ( I have not verified these numbers but it looks fairly close)...

I believe you are shooting for a blown flap, but you will need a jet for that...
A true slotted flap would keep performance at cruising while getting you ~80% increase in Cl_max at a lower alpha (AoA) IMHO, but you would need a new wing for that, not something you can easily bolt on, that is what I am working on... some progress but I made the error and effort in working on Carbon and that is $$$ and Slow...

Hi, I thought I follow up and plug Keller´s work on this thread... he is doing some amazing work an a Cub Like Application...



Here you can see some serious amount of engineering and ingenuity both at work, not to mention the resources to put this together, this is an amazing piece of machine... I would bet this thing can lost down at less than 300 ft/pm (or close to 25mph) in an off engine situation... not sure how it would perform on bush flying situation at its design limits... high AoA and speeds close to 25mp/h IAS (or lower)... (probably CAS if you had a circular anemometer) but I think there would be little response to the controls.

Would love to see his operations and pick his brain!

I like to spoiler the best, and I think this is a good way to get us mortals to an approach of the flying capabilities of this wing, albeit use it only on the flaps.

Neato!

Spain. I am wondering why you think there would be "...little response to the controls..." in this regime.?? Did you experience this or hear Doug Keller mention it?

In my experience in Cubs like this...the slat provides enough flow to the ailerons that they are effective at very, very slow speeds. (However, some of the drooped aileron/"flaperon" slatted Cubs have poor roll authority at very slow speeds).

Would you expand on your statement "...I like to spoiler the best..."? Thanks. DAVE

Is this Keller's brain child, I would like to see more pictures of the total aircraft as I see a lot of unique equipment on the aircraft. Any video of aircraft flying?
Thanks Kay

SpainCub said:

Hi, I thought I follow up and plug Keller´s work on this thread... he is doing some amazing work an a Cub Like Application...

Here you can see some serious amount of engineering and ingenuity both at work, not to mention the resources to put this together, this is an amazing piece of machine... I would bet this thing can lost down at less than 300 ft/pm (or close to 25mph) in an off engine situation... not sure how it would perform on bush flying situation at its design limits... high AoA and speeds close to 25mp/h IAS (or lower)... (probably CAS if you had a circular anemometer) but I think there would be little response to the controls.

Would love to see his operations and pick his brain!

I like to spoiler the best, and I think this is a good way to get us mortals to an approach of the flying capabilities of this wing, albeit use it only on the flaps.

Click to expand...

Do you know any more about Keller´s use of the spoiler?
Are the slats pivoted or pop in/out?
Do they experience any tail issues (shakes etc)?
I'm sure they are attempting to keep things close but would really like more pics too.

THANK YOU

frank

Guys, I have no info on Mr. Keller's work other than what I can see and extrapolating with observations from what I have been experimenting with.

Dave, my comment is a general belief that you either get more wing area as you fly slower, but regardless, the reaction time from input to response is so slow that I can "ASSUME" that this is the expected performance of this plane. Flown a Swallow (open cockpit beauty from the early era of flight) at near those speeds (no laps) and you see what I mean, that of get on the water on a sailboat and see what I mean in both mediums... water and air.... SLOW.

I meant to say slotted flaps... don´t know hoy I typed that ... sorry no coffee yet at that time.... zzzZ

Dave, It looks as though Doug Keller used a variation of Otto Koppens wing design on the Helio. The ailerons have less span and more chord along with what looks like a small spoiler above the aileron.

Great stuff, a little complicated for the average home builder.

This is an experimental wing I have been developing since several years for the DoubleEnder Project.
I retained the services of an aerodynamic company to help come up with the design, Doug Keller did the engineering, and Eric Lewis and Pete Anderson built it. Some things worked and others didn't. I'll post an update on the DoubleEnder progress when I have more time. We have come up with quite a few other neat things too. There are more pictures of the wing in my gallery.

http://www.supercub.org/photopost/showgallery.php?cat=500&ppuser=1739

Alec

Hey Alec, thanks for the follow up, looking forward to hearing more about your progress and telling us more about those

neat things

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Alec, can you give us just a quick rundown of "...some worked and others didn't..." ??!!

Very Cool fusion of ideas, Alec and Doug! Would love to hear how it feels to fly.....with the big vertical surface, airfoil horizontal tail, thick wing, and spoiler dump to retain roll control with all that flap.......

KenyaCub: That wing on the DoubleEnder is one of the best looking STOL wings I have seen on a G.A. airplane! I think that anyone that is interested in STOL airplanes, would really like to hear some of the details on how this wing performs! Nice work! Some really nice pictures of the DoubleEnder in the member galleries, on and in some tight places, if you have not seen them!

Alec/Doug - Congratulations on breaking the mold and defiantly thinking out of the box!
When you can, we are very excited to hear more!
Do you have any tail shake? Is the low end tail stability a non issue? Slow speed engine out stability?
Spoilers do all you hoped? Yaw?
Speeds, weights and goals?
... your persistence is overwhelming!

Thank you for sharing!

Thanks for all the comments. I have posted a full update on the DoubleEnder here:

http://www.supercub.org/forum/showthread.php?45763-DoubleEnder-Update-2013

and its new website here:

http://www.bushplanedesign.com

Dale, I made a set when I built a set of 2plus2 wing panels for my exp supercub because I had no dogs . I. Did not install them because Wag-Aero didn't. Have much info on how to install them had second thoughts anyway do to the fact. My cub has to stay outside. And could imagine the problems with. Water etc.

Hi everyone - I am not an expert on anything and maybe the following is a well known fact for all. Many years ago, I read about a Robertson STOL upgrade for a V35b Bonanza where they fitted it with full span flaps, roll control being done solely by nearly full span spoilerons just ahead & above the flaps. When the flaps are extended, the spoiler on the opposite side of the roll is allowed to move down, effectively closing the gap above the flap. The author of the article said at the time that this was so effective that, should he ever consider to roll the aircraft, he'll do it with flaps down. The closest link I could still find to this mod was: h tee tee pee w w w bonanza.org/MagazinePDF/2005/06/062005.pdf (sorry, I'm not allowed to post the actual link it seems) where it mentions this aircraft about halfway down. I think this might explain it in more detail: h tee tee pee w w w aopa.org/News-and-Video/All-News/2013/November/Pilot/Airframe-Rethinking-roll-control.aspx (sorry once again, it seems as a new member I'm not allowed to post the actual link at the time) Whilst I'm at it, is there any place that I could find the actual profile, template or coordinates for the full span Horton cuff? Also, could anyone please inform me whether this would have the same effect on the more modern laminar type of airfoils like i.e. the new AS5048 used on light bottom wing aircraft like i.e. the Rand Robinson KRII? (Yes, I realize that this is a Super Cub forum, but I find this discussion extremely interesting) If not, would it have the same desirable effect on the original RAF48 airfoil that this aircraft was designed for? Should I ever build something like this again, I would like to build this cuff into the airfoil profile right from the onset. This is what I'm once again intending to build, only this time a more STOL version of it: h tee tee pee w w w avcom.co.za/phpBB3/viewtopic.php?f=1&t=129963 Please allow me one more question: Why are the flaps so small on the Robin DR series of aircraft? Does the wing profile not allow for bigger, more effective flaps? Cheers all & happy flying, Henni.

Henni---I own a 1977 V35B with the Robertson STOL. One of two ever made. It works very well.

Wow, Thank you for the answer - never expected an actual user to comment. If one searches for spoilerons for roll control on google, all one finds is negative feedback. However, the article I've read seems to indicate like you that this actually works very well if used correctly. So then, there is no excuse for not going for full span flaps with only spoilerons for roll control. Wonder why Doug did not go for this option. Can you tell me, if your flaps are deployed & your spoilerons in the neutral position, are both resting flat against the flaps? If not, what would you estimate the opening above the flaps in the neutral position or do they just stay put in the default position when you lower the flaps? Also, do you experience any deadband in roll control during the initial spoileron movement? Apologies if any mistakes as English not my native language. I'm based in South Africa. Keep well all, Henni

I see the folks at Back Country Cubs have updated their site with some new info on the LSA they are working on. www.supercub.com This is the one that should be both the fastest AND slowest thing out there, it should have if all goes according to plan, the largest spread between landing speed and cruise. When I commented on the spring gear, they said that of course cub style gear will also be available, but they went with this spring gear because they really want to show off it's hoped for high speed, and that is pretty clean, real clean, compared to cub gear. Another interesting point about the choice of gear was that the AOA will not be the super high one and consequent slam down of other slat equipped birds, more of a normal AOA and at such ridiculous low speeds monster tough gear may not be warranted. Mostly a drag/speed thing though.

delete

Spring gear on a cub......

Hi Palhal, Would please be so kind as to inform me, if your flaps are deployed & your spoilerons in the neutral position, are both spoilerons resting flat against the flaps or do they just stay put in the default position with an equal opening above both flaps? Also, do you experience any deadband in roll control during the initial spoileron movement? Kind regards, Henni

Henni----With full flaps and level wings there is a big gap. As soon as you put aileron into it the opposite side goes down and touches the flap. There is no deadband during the initial spoileron movement. The spoileron moves the wing just like a stock aileron type wing. You wouldn't know you are flying with spoilerons. The spoilerons are 4 1/2" X 94 3/4" When the spoileron is down there is still a gap from the inboard spoileron edge to the fuselage. I was told that this would not work on a Cub wing because there is not enough air movement. The spoileron needs to be placed at the front spar area.--Palhal

courierguy said:

I see the folks at Back Country Cubs have updated their site with some new info on the LSA they are working on. www.supercub.com This is the one that should be both the fastest AND slowest thing out there, it should have if all goes according to plan, the largest spread between landing speed and cruise. When I commented on the spring gear, they said that of course cub style gear will also be available, but they went with this spring gear because they really want to show off it's hoped for high speed, and that is pretty clean, real clean, compared to cub gear. Another interesting point about the choice of gear was that the AOA will not be the super high one and consequent slam down of other slat equipped birds, more of a normal AOA and at such ridiculous low speeds monster tough gear may not be warranted. Mostly a drag/speed thing though.

Click to expand...

Glad they are coming out with an LSA version, but I still I don't understand the design goal and how they will reach that from the pictures provided. Getting flight at Re 2000000 and bellow at their level of wing loading will be a challenge. Also to maintain the high level of Cl with those slats + slatted flaps requires energy that will well prove difficult to achieve in real world flying. What really boggles me is their choice to go carbon skins trough the wing? And if going that route, why not take advantage of designing a carbon wing to minimise weight? They could have done away with the spars and making the ribs and skin the wing structure... just saying...

Hi Palhal, thank you for your detailed answer my friend. Kind regards,Henni

cub12 said:

lowrider, I don't think slats will help you on floats as you can't land at steep nose up attitude that's why i opted to use a cuff on the outer 8 feet of my wing. one thing i found with the cuff was that i needed to increase the angle between my wing and floats about 1/2 degree.

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The advantages of slats are not limited to short high angle of attack landings. Most accidents happen on the turn to final or the first turn after take off. Landing on rivers with floats often involves some very tight maneuvering when you are low and slow. A strong up draft coming off a wall of trees, can momentarily change your. " relative " angle of attack 5 or more degrees. If you are coming in just below the stall angle of your wing and you hit this up draft, your wing will momentarily stall. NASA technical papers show that cuffs on Cub airfoils give very slight increases in lift coefficient but --stall at lower angles of attack. The simple explanation is that at high angles of attack the air (separation point moves aft ) has a harder time getting around the sharper leading edge and will seperate (stall). VG's can allow the wing to fly at a few degrees higher angle of attack to the RELATIVE wind. Slats might allow the wing to not stall for more than 10 degrees above the airfoils normal stall angle.

On take off, a cub trying to get up on step is above the stall angle during some of the acceleration. Especially, if you are rocking the aircraft for and aft. Having the wing stalled adds to the total drag. A slatted wing would not be stalled. In gusty situations, having a wing stalled makes dealing with a wing dropping even harder.

Slated Flap

SpainCub said:

I like the idea of full flap and spoilers... sounds like an interesting design. Now I also understand your questions about airfoils....
BTW, I never commented on the amount of air, I was referring to the video in the sense that a good laminar headwind just ads to what the triple prop is blowing and the tail, also it does reduce some of the induced turbulence from the high AoA.


I was considering also a slated flap could be a good design on a cub. It would gibe you higher Cl than a regular flap, and at the same AoA would be higher than a Slatted wing...
I am still waiting to see if I can ever run some CFD on this design and see where the Cl vs Drag, and how CP moves through AoA envelop. I would also like to see how the Riblett behaves compared to the 34-B Airfoil in a 3D wing model, normal, Slat, Slot, and slated flaps. I thought about the change in cord, but I have not come up with any real benefit to the flight characteristics of a cub, maybe I am missing something? (I know about wing loading and Cl and shorter TO roll, but what else?)

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Thank you for your commentary SpainCub.

Regarding a SLATED flap. The website for the Double Ender says that they tried a slated flap but it did not produce ENOUGH drag.
The one they have stuck with is a 2 surface flap with each surface having nearly the same chord; not a slated flap. They also say that they couldn't get the plane to slow down with the slated flap. I assume, maybe incorrectly, that they mean with a power setting that they need for pitch (airflow over the tail). Best L/D or Lift to Drag ratio may not be ultimately what they needed. It would be very interesting to hear their reasoning behind this. This would point to the maxim that: optimization of one thing can be detrimental to the whole picture.

I going ahead with a drooped aileron which hopefully will add some low speed lift and maybe some more near stall control...we'll see when I get it flying.