• If You Are Having Trouble Logging In with Your Old Username and Password, Please use this Forgot Your Password link to get re-established.
  • Hey! Be sure to login or register!

Experimental Cub Kit with Slotted Wing 180 Hp and Big wheels any suggestions on kits

Lowleveldevil,

Slats only work at high angles of attack. I read it on the internet. It must be true. ;)
Actually, slats alone never appealed to me. The combinarion of slats and long split flaps does. I can wheel land on a calm day in the low 20 mph range. And I'm nowhere near what I'd call good in my plane. The only down side I've found is landing in unfavorable winds, but I'll figure that part out.

My favorite response to the high AOA comments is a video. https://m.facebook.com/story.php?story_fbid=278939462739118&id=255326078142483&_r
 
Last edited:
Gents &
Southern Aero

I certainly enjoy a good discussion and thank you for sharing your knowledge. There are different types of LE devices. Some, like the Boeing 737, and to a limited extent the Helio extend forward and down. These effectively change the camber of the wing and will increase the lift at lower angles of attack. My understanding of the Backcountry slats (the only ones commercially available that I know of, and hence the ones I was referring to in my posts above) is that they are fixed slats that do not "open" until the AOA reaches a certain point. I do not know what that point is. But.....my belief.....and I may be wrong.....is that they would not be deployed at the takeoff or landing deck angle for "normal" float operations and perhaps "normal" gravel bar approaches. Obviously I have seen the videos of the very high AOA landings on youtube. Based on the OP's post and questions I asked why he wanted them.

Doug Keller spent a great deal of time developing his flap because it lowers stall speed at a lower deck angle. He did not develop (though I know for a fact he looked long and hard at the concept) LE devices because he felt they would have limited benefit for normal backcountry flying applications. However, I will add that I have seen his LE slat experiments so I know he is still looking at it. LE devices that "extend and droop" add considerable complexity and weight and because of those design criteria have seen very limited application in GA. It sounds like the wing you are building may have a different type of LE slat than the Backcountry (Wayne Mackey) design.

Hey....lets be clear here....I am NOT saying LE slats or slots, or Kreuger LE flaps, etc are bad!!! I use them several days a week. It all depends on your mission and what you want the airplane to do.

But I asked, if they were necessary, based on his mission. Everything in aircraft design is a trade off, weight, complexity, cost, performance compromises, etc. LE devices have advantages and disadvantages. You just have to decide what works for you based on your knowledge of these compromises. Like all things LE devices are not free. Are you willing to pay the price? Does it fit your mission?

Hope this helps

Bill
 
Stewartb
I think the Knik wind helped a lot more than the slats or flaps in that video.:wink: The thing that is pushing me towards the slats is the reports of the wing being very stable at very slow speed (getting old does not improve your reflexes). I think having the wing nut plated as you do is the way too go. Very easy to remove if you feel it is not worth it. Do the Backcountry slats pivot down at all as they open? Could the pivot point be changed so they did?
DENNY
 
Last edited:
Not much wind in that clip.

Mackey slats pivot . The travel is limited by stops. The typical installation is slat LE flush with the bottom of the wing. Some guys have experimented with lowering the slat. I've heard mixed reviews about that. I'll probably never need anything more than what they provide me now.

Image1549037104.935862.jpg
 

Attachments

  • Image1549037104.935862.jpg
    Image1549037104.935862.jpg
    391.8 KB · Views: 245
The mackey flaps open even just as you are taxiing along... the get pushed shut when you go fast.


Sent from my iPhone using SuperCub.Org
 
And while my Cub cruises at 100 mph the slats are never fully closed. Very interesting to watch.

Anyone else ever recognize how your plane's attitude changed with the addition of VGs? How you could fly a familiar attitude and found that the airspeed was lower than it had been before VGs? The same thing is true with the slats. I have to slow the plane down to about 50 mph before I can pull flaps. At 50 I'm not wallowing around with the nose high. It's in a normal attitude and rock solid. When I do pull flaps on the nose rotates down and I counter that by lifting the nose and slowing it down, grab another notch, repeat... If I wheel land faster than about 26 mph and lower the tail it flies back off. I need more time to get more familiar with a steeper final approach at slower speeds. All I need is a motor.
 
Last edited:
Stewart.....

In this video at the 4 minute point Kevin talks about the LE slats. Are there two different Backcountry LE slat designs?




Thank you

Bill
 
Last edited:
When he's putting them through their motion they are pivoting on the hangar as shown in the photo I posted. You can see the main pivot and the smaller screw is the stop. The opening motion is very simple.

FWIW Kevin's slats were set below the wing bottom.
 
My recollection of Helio slats is that they articulate. That is, they moved on tracks of some sort that changed their position forward as they deployed. Mackey slats are simple. And they don't make the big bang when they drop out like Helios' do.
 
Bill Rusk said:
Gents &
Southern Aero

I certainly enjoy a good discussion and thank you for sharing your knowledge. There are different types of LE devices. Some, like the Boeing 737, and to a limited extent the Helio extend forward and down. These effectively change the camber of the wing and will increase the lift at lower angles of attack. My understanding of the Backcountry slats (the only ones commercially available that I know of, and hence the ones I was referring to in my posts above) is that they are fixed slats that do not "open" until the AOA reaches a certain point. I do not know what that point is. But.....my belief.....and I may be wrong.....is that they would not be deployed at the takeoff or landing deck angle for "normal" float operations and perhaps "normal" gravel bar approaches. Obviously I have seen the videos of the very high AOA landings on youtube. Based on the OP's post and questions I asked why he wanted them.

Doug Keller spent a great deal of time developing his flap because it lowers stall speed at a lower deck angle. He did not develop (though I know for a fact he looked long and hard at the concept) LE devices because he felt they would have limited benefit for normal backcountry flying applications. However, I will add that I have seen his LE slat experiments so I know he is still looking at it. LE devices that "extend and droop" add considerable complexity and weight and because of those design criteria have seen very limited application in GA. It sounds like the wing you are building may have a different type of LE slat than the Backcountry (Wayne Mackey) design.

Hey....lets be clear here....I am NOT saying LE slats or slots, or Kreuger LE flaps, etc are bad!!! I use them several days a week. It all depends on your mission and what you want the airplane to do.

But I asked, if they were necessary, based on his mission. Everything in aircraft design is a trade off, weight, complexity, cost, performance compromises, etc. LE devices have advantages and disadvantages. You just have to decide what works for you based on your knowledge of these compromises. Like all things LE devices are not free. Are you willing to pay the price? Does it fit your mission?

Hope this helps

Bill
Click to expand...

Bill, huge respect to your knowledge and experience, but deploying those gigantic flaps is what give the WING the AoA necessary for the slats to do their work. Or, more accurately, the huge WING AoA available with very normal fuselage deck angles makes the slats necessary in order to extract the available performance from the wing.

Wing and fuselage angles can be used interchangeably until you start deploying TE (and some LE) devices. Once you deploy those, the angles change with respect to each other.

Wing AoA is the angle between the chord line and the relative wind. Once the big flaps lower, the chord makes a pretty significant adjustment.

Or at least that’s what I learned from JJ McCue.
 
Thx guys I really am enjoying all your input on this subject . At the moment I’m thinking both Leading Edge Slats and the Kellor Flaps will give me what I’m after . I like the idea of building my one of a kind Cub Experimental. I am a confident experienced pilot . I know I will be pushing the envelope in some of my operations. I am a big guy 6.3 tall and 220 lbs. my next question is which kit . Jarvron , Back Country or Dakota or are there other recommendations. Remembering I am seeking a kit or nearly all the kit . I do not live near many Cub guys and will be working towards a high performance light Cub kit with minimal creature comforts.
 
stewartb said:
My recollection of Helio slats is that they articulate. That is, they moved on tracks of some sort that changed their position forward as they deployed. Mackey slats are simple. And they don't make the big bang when they drop out like Helios' do.
Click to expand...

Stewart

Yeah, the Helios are on radiused "tracks" or rollers. Aerodynamically/automatically driven with 2 on each slat. This radius motion (13 degrees) is what gives the wing the greater camber and wing area when extended. Lot of lift here as the Helio will fly at 27kts in a level attitude. As for the bang, unless a slat was sticking retracted for some reason, abrupt maneuvering or turbulence the slats shouldn't bang out. Rubber bumpers on retention arms missing? Dunno....

As for the original question............ If building on a budget, ...... I'd go with squared off wing tips, move ailerons out to tip, extend the flaps. Flaps, the more the better, would make the best addition for the least investment. 160HP with fixed pitch prop (Borer?). +3 on the gear, tires to suit. And keep it light. ....... Got more money? More HP, CS prop, LE devices......... Slots will allow you to fly at high angles of attack but do you need to for what you plan to do? Slats will give to more wing area and create that "slot" but would not be practical without a good set of flaps (flatter approaches). The Mackey type slats work great and everyone loves them and they are pretty inexpensive way to get that slatted wing. Only drawback is they don't retract to original wing area to let you get a better cruise speed ...... . Performance enhancements cost money and add weight. As said earlier, everything is a trade off. I opted to throw more time an money at it and it remains to be seen if it will be worth it!
 
My Cub is sharing the hangar with bro-in-law’s 206 until spring. I look at them together every day and I can’t decide which one is bigger. A useful hauler with better than Cub performance. Very different from a Carbon Cub. It may not appeal to everyone but I sure like it. If the Carbon Cub is on one side of the spectrum and the Rev is on the other, the Javrons and other Cub clones fit somewhere in the middle. To me identifying what’s important within that spectrum is the key to deciding which one suits you.
 
On the slats, As has been said, They make the wing more effective at producing lift even at low angles of attack (assumeing due to energizing the boundary layer). My little throw away mount was docile before them. Few mods will make a noticeable difference in the seat of the plane. They will , Even if not flown at high AOA.
 
I am not sure I would make the assumption that the LE slat produces an increase in lift at low AOA values. In fact, it is entirely possible that there is a small loss of performance due to a separation bubble behind the slat. Without wind tunnel data you are making assumptions. In addition, we do not know the AOA value that the slat opens. I certainly agree that it increases CLMax at the higher AOA values. Here is an interesting article that may give you something to think about.

Effect of Leading Edge Slats at Low Reynolds Numbers

Lance W. Traub *,† and Mashaan P. Kaula †

https://webcache.googleusercontent.com/search?q=cache:6xym9v4SrnYJ


Also page 53 in the book Airfoil Selection, Barnaby Wainfan has some info on LE devices.

Bill


 
Did I mention my slats are partially open during cruise? What would the result be, based on what we know they do in the more traditional high AOA-slats open profile? The only time I see my slats fully closed is when the plane's parked.
 
No, you did not mention that. You would "probably" have an increase in boundary airflow energy and "probably" an increase in drag. It would be fun to put all this in a wind tunnel and get the real facts. We might all end up with LE slats.

In all your panel stuff, I know it is high end, do you have an AOA indicator? It would be interesting to get some data correlating AOA and slat opening. i.e. where do they go full open. Even using just airspeed would be interesting. At what speed do they go full open?

Anyone else with Backcountry LE slats have any info?

Thanks

Bill
 
stewart, Is the relationship of the slats to the wing adjustable on your plane? Perhaps if they were a bit higher they would completely close in cruise? Though it likely wouldn't make a noticeable difference.
 
Bill Rusk said:
In all your panel stuff, I know it is high end, do you have an AOA indicator? It would be interesting to get some data correlating AOA and slat opening. i.e. where do they go full open. Even using just airspeed would be interesting. At what speed do they go full open?
Click to expand...
Tie a piece of yarn to the center of a jury strut. That should give a close estimate of the angle of attack.
 
Lowleveldevel
What is you definition of "light"? are you talking 900 lbs or 1200 lbs. The Backcountry SQ planes are not light. I think Javron will have the lightest fuselage least amount of space. If you want to travel in Canada I suspect you will want some big tanks also so add them to the mix. If you are going to be shoving a lot of camping/fishing gear and a passenger in the plane I would recommend L21 glass or metal headliner, and a belly pod. Bill did a fabric headliner, if I remember right he can add how it worked on his adventures. Go to a fly in and sit in everything you can find. Have someone take pictures, go home and look at pictures, pick the one with the biggest smile, buy that fuselage.
DENNY
 
Last edited:
Helio slats can slam out with a bang when in windy conditions. They are controlled by airspeed, come out at about 55mph, but in winds they can deploy with a bang to their stops. The are fully individual on each wing, two per wing and can come out one at a time if turning a bit as one wing is then faster than the other, etc.
Helios also have what they call interceptors that are spoilers that pop out of the top of the wing when more aileron control is input. Essentially killing the lift on the wing on one side or the other to keep the wings level is slow flight. This makes the Helio pretty much stall proof (stabliator/they call elevator is limited to prevent too nose high for stall break) and Helios descend wings level in sink mode, no wing drop.
Very safe features designed into them. I have landed them in wind with almost no forward movement, they do fly at about 27-8 mph with power.
John
 
For some fun tuft the slat leading edge and underside of the wing with yarn just behind the slats (or on wings without). Watch the airflow in an approach to stall. It might reverse and flow forward into the slot and up and around the leading edge. Makes Cessna stall horns work. Fine tune the slat position versus airflow?

Gary
 
Stewart

I've looked at those type of slats since they came out. Seems as tho they all fly with a 1/2" or so open. I often thot you could have a retaining mechanism of some sort for "cruise" flight and release them for slower/landings. The low pressure on top of the wing is keeping them open, should help "slightly" for drag reduction if retained. Tho the slats on my wing will function as the Helio and wont have the opening issue I am still going to have a retaining or lock feature for them. Biggest reasons bird strike and for operating in moderate to sever turbulence .......... .a Helio or two had an issue with this with disastrous results.

Curious to know what airfoil section the USA 35B ends up being after the slats are added........... I've never laid it out or plotted it out to see what it might be. Whatever it is, it works good!

Beer thirty?? Yes sir, just opened up a Blue Moon..........
 
You must log in or register to reply here.

Similar threads

T
Kit or ??
Replies
13
Views
3K
Tailpilot
T
L
Firewall Forward Kit PA18 180 Hp Titan
Replies
1
Views
1K
skywagon8a
skywagon8a
L
Legend Cub HP 180 hp
Replies
12
Views
11K
bob turner
B
A
Super Cub build part scratch part kit
2
Replies
34
Views
11K
Adam Gordon
A
L
Constant Speed Prop PA 18 Experimental with Titan 180 hp
Replies
20
Views
14K
stewartb
S
Back
Top