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

Vic,
The thoughts I placed to deciding what I wanted or call it needed as far as LE devices in my build.
Yes I want to be able to truly slow the plane down, BUT more important in my aging mind was to make the plane "spin proof".
Spin proof is really making a plane stall resistant.
Vortex generators help with keeping the flow attached to the upper surface but from what I see there is little rhyme or reason they are placed where they are. On any particular plane I see them way up front or back about 20% of the airfoil. They are mounted helter skelter at different spacing and angles. I hear they work fine but many pilots say they can not tell any difference.

Slots, allot of work for some but no great gain. Many airplanes that came with slots, they get skinned over and the plane performs better.

Slats, they do seem to work well. There are quite a few versions that each have there own benefits and take aways. But they all offer a substantial reduction to "loss of lift"

The add on slats as used in the Mackey design work well. Personally a little more tweaking of pivot location and they will close fully under low lift conditions, "cruise". These slats came to being long before a 20YO on a computer could analyze them.

The Handly Page slats as on a Helio are an engineering marvel. I like what I have designed but I fully expect these are not optimized as to their opening and closing. More complex to build but for a few of us, they will be worth it. Again a 20YO can probably write the code and get them optimized in short order, we grown ups throw darts and build what we feel is best.

Even if any slots or slats are not optimized they will be there when they are needed.

The myth the plane needs to be at a stupid steep deck angle for LE devices to work is not necessarily true.

For one, when flaps are deployed, you can place an imaginary line from the leading edge to the trailing edge of the flap. This line is your camber line which increases your AOA of the airfoil. The deck of the fuselage may not get much steeper but geometrically the wing does.
This is what will bring the slats, or slots for that matter, "into play" at usable flight parameters.

For me, I am looking for my wing to both "save my azz" as well as the low speed performance gain they offer.

Charlie, thanks for the thoughtful post.

As I mull things over my goal is similar to yours. Priority is to save myself from being stupid.

I've never come close to stalling inadvertently near the ground, but that doesn't mean I might have a lapse sometime. These just seem like a good idea.

I get the effect flaps have on AOA. I've been playing with that idea and pouring over the old books you recommended.

Right now I'm drawing out an alternative flap arrangement--it involves using a duct that is shielded by the upper part of the wing cove when retracted, but when deployed, it looks somewhat like a double slotted flap. I'd like to know if that approach has been tried elsewhere--I haven't found anything yet.

Ideas. I love noodling and as I get closer to starting on wings I'd like to settle on a general direction.

RVBottomly said:

Charlie, thanks for the thoughtful post.

As I mull things over my goal is similar to yours. Priority is to save myself from being stupid.

I've never come close to stalling inadvertently near the ground, but that doesn't mean I might have a lapse sometime. These just seem like a good idea.

I get the effect flaps have on AOA. I've been playing with that idea and pouring over the old books you recommended.

Right now I'm drawing out an alternative flap arrangement--it involves using a duct that is shielded by the upper part of the wing cove when retracted, but when deployed, it looks somewhat like a double slotted flap. I'd like to know if that approach has been tried elsewhere--I haven't found anything yet.

Ideas. I love noodling and as I get closer to starting on wings I'd like to settle on a general direction.

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Just happened to be playing with putting one together from backcountry/sq/Mackey type today.


Sent from my iPhone using SuperCub.Org mobile app

Rev 3 wings are very different than Rev 2. Very cool. There are a handful under construction up here and I'm excited to see what they can do. Experimental STOL airplanes are gaining momentum. Fun stuff!

How about a LE slot in the factory flaps? Our at least several insertable ducts in the LE between nose ribs. Maybe it's been done.

Gary

The nice thing about an EX build is you do not need to be locked down to the original 20% flap chord dimension. There is 9" of room between the rear spar to the original flap just begging to be utilized. Now granted many feel that flaps should just be 25% chord but even still that would be about a 16" flap chord. Still allot or room left.

A Fowler flap with a fixed LE slot would work fine in that space. The DC-9 used these and there is a fair bit of documentation online for these.
The Mackey slotted flap looks interesting but where Vic is working in wood I would build the LE to be a true airfoil rather that a single surface.

My Rev 2 ailerons are 17-3/8" deep. The Rev 3 ailerons in Mike's shop are 24" deep and have less span. Maybe Mike will measure the flap depth and span. The structure of the new wing is hell for stout, not like mine was lacking. The new revision appears to be well thought out. I envy the overhead flap handle and direct drive push rod concept but haven't seen one set up yet.

stewartb said:

My Rev 2 ailerons are 17-3/8" deep. The Rev 3 ailerons in Mike's shop are 24" deep and have less span. Maybe Mike will measure the flap depth and span. The structure of the new wing is hell for stout, not like mine was lacking. The new revision appears to be well thought out. I envy the overhead flap handle and direct drive push rod concept but haven't seen one set up yet.

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I bet those work sweet.

I'm told they work well. With as many Rev 3 wings as there are in AK I'd say the confidence level is high. I'm still happy as heck with my Rev 2 wings but find the innovation exciting.

With the way BCSC beefed up the structure in the wing they must expect a lot of stress from the flaps and ailerons. Or maybe its to control stress ON the flaps and ailerons. I know nothing about the consequences of increasing chord of control surfaces but I'm a pretty good observer and the structural members are hard to miss.

BC12D-4-85 said:

How about a LE slot in the factory flaps? Our at least several insertable ducts in the LE between nose ribs. Maybe it's been done.

Gary

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That is sort of what I was talking about. I cut out some shapes this morning because I don't have CAD stuff. Around the 42 second is close to what I was thinking. The "slat" is drawn out on the flap pattern. Nothing is set in stone--just a try at visualizing.

Vic, That's a good way to visualize the mechanics of making the system work. Part of your visualization should be at what angle of deflection does the air flow start to separate from the flap? As the angle of attack increases the flow of air starts to separate from the upper surface starting at the trailing edge working forward. That initial angle is when you want the slot to begin opening. This will provide an accelerated flow over the upper surface sticking the flow back down. Then with this first slot open you will be able to move the flap further down until the flow again starts to separate. It is this new angle of deflection where you will want your second slot to start opening.

I've found through testing that the flap on a Cub will deflect down at least 56 degrees with just one slot without any airflow separation at the trailing edge. So unless you want the flaps to deflect more than 56* you will not need the second slot.

Start at 2:14 Notice how the air flow separates from the trailing edge forward. A flap is just a small wing and a leading edge slat on the flap is just another small wing. They all react the same effecting the flow on the surface behind them.

Thanks Sky. I'm not sure I'd need more than 56 degrees. I should look more closely at the flaps you have.

As much as I like the idea of Keller flaps, they seem more complicated than I really want.

Guys, the quest for the lowest possible speed is getting out of hand. Your starting to talk nano-knots here when the average pilot can't come close to getting the performance out of the airplane.Once you can achieve a 100' take off or in that range why do you need to spend a bunch of money or time getting say a 10% reduction. How many of you are going to fly into a 500' strip. VGs make the airplane almost stall proof and slots/slats make it virtually stall proof. I like the Kellen flaps as it allows you a steep approach compared with slats. I built two Cubs a couple years ago one with the Dakota Cub slotted wing and the other a round tip stock wing with VGs. We have flown the airplanes together a couple of times and here is what I observed. The DC wing with the long flaps would not stall and it was at a ridiculous angle of attack at 28mph ground speed. In three point attitude it would fly around 35mph. The round wing Cub would fly around 35with full flaps and about 40 in three point attitude. So final approach speed is about the same in both. Cruise speed in the DC wing airplane with 31"s, a 220hp Lycon O-360 and a MT9 Constant speed prop is 110mph at 10gph. The round wing with an O-320 195hp with a 2 blade MT prop and 8.50 tires is 125mph on 8.5 gph.
Anyway it's a fun exercise comparing all the options but unless you are going to operate out of extremely short strips even a stock Supercub is adequate.

pittsdriver said:

Guys, the quest for the lowest possible speed is getting out of hand. Your starting to talk nano-knots here when the average pilot can't come close to getting the performance out of the airplane.Once you can achieve a 100' take off or in that range why do you need to spend a bunch of money or time getting say a 10% reduction. ..

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because helicopters are not allowed for hunting, but fixed wing planes are... at least up here....

pittsdriver said:

Guys, the quest for the lowest possible speed is getting out of hand.

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Some of us do not agree with that. For me I have a 150' one direction field in mind that I want to frequent. I consider that a valid goal to work for. This will be ski operations as well.
I am also not a kid anymore and want a margin to work with when things might not be optimum.

Charlie, I think that he is talking about people who think 500 feet is short.

When you can reliably land in <200' a lot of places open up that other planes can't access. And my own 500' patch is in between thickets of trees, so 500' isn't always 500'.

When my pro Supercub driver friends can come and go at full gross from 300' in the mountains this hobby pilot needs an equipment advantage to keep up. I could quit my job to fly every day to achieve that proficiency level but then I couldn't afford to fly.

Landing at 24-25 mph is fun, and the combo of slats and Keller flaps allow doing it in a very useful attitude. If I want to raise the nose and slow it down more and drop it on? The TK-1s allow that, too.

If money was not a factor, I would be building my cub another set of wings, just to try to be able to fly a little slower. A few mph less are always welcome for me.

pittsdriver said:

The round wing with an O-320 195hp with a 2 blade MT prop and 8.50 tires is 125mph on 8.5 gph.

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Where do I find one of those engines?!

I appreciate the observations, pittsdriver. 500 foot strips probably would not be my norm, but 700 foot strips at 8000+/- density altitude are likely and nearby. I'm probably the least experienced of the bunch here, and I'm very cautious. All these things we are discussing are "padding" for a semi-old, semi-adventurous guy.

If you can do 700 foot strips at 8000 ft da, 500 foot strips down low will be easy peasy.

But it's not the taking off short part that is hard, it's the landing short part, that requires a bunch of skill.

If you are serious about wanting to go in and out of a 700 foot strip at 8000 da you definitely want a big wing cub with lots of horsepower.

Does nitrous work well at high altitude? ;-)

Then there's the issue of IAS vs TAS at altitude. At one time I think I was taught it was a rule of thumb ~2% increase per thousand feet. Lift off or land at a reasonable AOA and IAS of 45 at sea level, and at 8000' same IAS but actual airspeed or ground speed with no wind is about 52. Faster means takes more time and distance to do things or something like that. See below. That's where big wings and power help.

Rules of Thumb: https://www.mountainflying.com/Pages/mountain-flying/rule_of_thumb.html

Gary

Good reminder, Gary. Before I get too ambitious, I'll need to practice on some of our 1600 foot airstrips, like Soldier Bar ID (85U).

On a cool morning.

We can stall the heck out of the plane at high AOA all day with enhancements but if it can't be landed w/o damage or rotated the same what's the point? Any lift device that improves performance without extreme AOA is a bonus.

Gary

RVBottomly,

You might find this valuable in the backcountry. I keep one in the SQ2 and the 185. All you need is sea level takeoff performance numbers for the plane at gross weight. And then you can input all the data about the conditions where you are (or where you wish to go) and get the takeoff performance for that aircraft.

https://www.sportys.com/pilotshop/takeoff-performance-computer.html

pittsdriver said:

They are heavy, roll rate is less than a Javron square tip wing and angle of attack. The customer insisted that i use the Dakota Cub wings so that's what I used. The customer is always right.

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You are comparing apples to oranges. The Dakota Cub slotted wing is certified to part 23 standards to 2300 lbs on the Super 18 and STC'd on the PA18. The Javron wing is experimental with a long aileron with a lot of that aileron outboard of the bellcrank. Probably a great wing but I doubt it would pass the certification process. My personal opinioon would be the new Carbon Cub ailerons on a stock Super Cub wing.

BC12D-4-85 said:

We can stall the heck out of the plane at high AOA all day with enhancements but if it can't be landed w/o damage or rotated the same what's the point? Any lift device that improves performance without extreme AOA is a bonus.

Gary

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For landing considerations only, Might be best to try and mimic ground effect vehicles. You very seldom see any kind of slotted flaps on those. One of the reasons I thought it more effective to eliminate any slots and deflect as much air towards the ground as possible. Seems to me any slight loss of lift by elemenating the slots on a flap would more than be made up for by capturing under the wing in ground effect as much air as possible and smoothly deflected downwards.

Yes that's a consideration...the elimination of slots. Best to test before and after a slot is installed. The info below seem to support that, but some claim the data in the book is often wrong and I can't argue one way or the other.

Have a look at Figure 134 on page 229 under High Lift devices in Abbott and Doenhoff Theory of Wing Sections 1959 (https://aeroknowledge77.files.wordp...tions-including-a-summary-of-airfoil-data.pdf)

Note the Clmax using 45* flap deflections for the various configurations and the degree of angle use to determine the values. Unless in a Storch, Helio Courier, or similar long gear most planes at 12+* AOA would have a hard time using the full effect of the devices when in ground contact. The plane has to comply with the takeoff or landing zone, but after takeoff or before landing high AOA can be used.

See the previous pages for designs of double-slotted flaps. The Airframes flaps work at a low AOA.

Gary

stewartb said:

Bare feet on a cold floor but I shot this clip for you anyway. Keller's flaps on Backcountry's flap hangars.


The ducted leading edge Rev 3 style would be a lot easier to imitate.

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Thanks for the videos, Stewart. I really appreciate seeing those things move.

Now if I can find a picture of the Rev 3 wing. All I've been able to find is tantalizingly low on detail.

Vic

Actually the Javron wing structure was designed by the same guy who designed the Carbon Cub wing. The ailerons are stock size but it has an extra two feet on the flap just like the Dakota Cub wing.The Dakota wing was pretty much the same with a two foot longer flap and stock size ailerons. Both have the aileron and flap bellcranks and control arms for ailerons and flaps in the exact same place. Javron's wing is also 2300lb. I have flow my friend's Javeron and it is right between the round tip and Dakota wing as far as roll rate.

Yes, Doug Keller designed the Javron wing. The thing that struck me was the amount of Aileron's outboard of the bellcrank. Having spent a lot of time with Mark Erickson at Dakota Cub and learning what failed when tested to Part 23 standards on the Wiffle Tree on the DC wing I would like to see the Javron wing tested that way. I bet it is plenty strong but that aileron and what I learned about the stock Aileron's on the Super Cub through part 23 certification make me wonder.