Daydreaming About Flaps

RVBottomly · May 1, 2018

I found this on the Rans website regarding teleflex for flaps.

It comes from the discussion of the S-21 Outbound. Scroll down to 3/29/17 entry:

https://www.rans.com/21-outbound-progress-page-2

I notice that flap deployment is in a pull configuration on a bellcrank. I remember the telexflex "Xtreme" cables can handle an 8" bend radius.

courierguy · May 1, 2018

I was almost going to say RANS was using them (tele cables) on the new 21, but wasn't sure and was too lazy to find out, good catch! And, that picture shows how simple the retaining bracket is for the housing, I'm sure there is some engineering out there saying it is plenty strong for the anticipated loads.

Using them for ALL flight controls works also, but not as light a feel as cables I'm guessing? Flaps don't matter near as much for primary controls as far as a delicate touch/small break out force.

Cubus Maximus · May 1, 2018

This early 90's Cub Crafters test mule had oversized hydraulic flaps that were infinitely adjustable (and dumpable). Worked pretty good!

Flap release / dump button (red) was on the control stick.

RVBottomly · May 1, 2018

Cubus Maximus said:
This early 90's Cub Crafters test mule had oversized hydraulic flaps that were infinitely adjustable (and dumpable). Worked pretty good!

Thanks for reminding me of that. I love playing with hydraulics, but I always wondered about the weight compared to cables and pulleys.

KelvinG · May 1, 2018

RVBottomly said:
I found this on the Rans website regarding teleflex for flaps.

View attachment 36802

It comes from the discussion of the S-21 Outbound. Scroll down to 3/29/17 entry:

https://www.rans.com/21-outbound-progress-page-2

I notice that flap deployment is in a pull configuration on a bellcrank. I remember the telexflex "Xtreme" cables can handle an 8" bend radius.

The teleflex 60X cable is rated for 250lbs pull. And from 250lbs down to 150lbs push depending on length of travel, (1" to 5"). I would need to know what kind of force the Keller flaps are producing before going this route.

All the talk of addition deployment forces being generated by Keller flaps makes that number critical in my mind. The RANS is a smaller lighter plane which means (I assume) lighter deployment forces.

Nice idea though! Does anyone have real numbers in regards to the Keller flaps? Seeing how you can get Keller flaps in various lengths it would be a psi per square foot number.

Sent from my SM-P900 using Tapatalk

stewartb · May 2, 2018

Backcountry's about two weeks from flying the new Rev 3 wing. Maybe the long Keller flap pressure thing becomes unimportant to anyone other than those of us with "old iron?"

Things sure change fast. Lead, follow, or get out of the way!

RVBottomly · May 2, 2018

stewartb said:
Backcountry's about two weeks from flying the new Rev 3 wing. Maybe the long Keller flap pressure thing becomes unimportant to anyone other than those of us with "old iron?"

Things sure change fast. Lead, follow, or get out of the way!

Heh. Looks like by the time I start building wings on my project, I'll have yet another design to consider. I'm intrigued--haven't heard about the Rev 3.

stewartb · Jun 14, 2018

I guess it’s okay to share a photo now that Rev 3 flight videos are showing up on Facebook. Cool new flap design. Controlled by an overhead lever and push rods. No more return springs. It appears to perform well in the videos. The ailerons are shorter in span and deeper in chord similar to Mackey’s SQ-12 wing. Back Country Supercubs continues to innovate. Bravo!

Sent from my iPad using SuperCub.Org mobile app

RVBottomly · Jun 14, 2018

That is very interesting.

I like apparent simplicity of the mechanism.

eskimo77 · Jun 14, 2018

Where on Facebook are these flight videos of the Rev3? Thanks, Joel.

stewartb · Jun 14, 2018

On Kevin Quinn's Big Tire Pilots page.

tempdoug · Jun 14, 2018

skywagon8a · Jun 15, 2018

stewartb said:
View attachment 37599

tempdoug said:

I don't mean to sound so contrarian but they should pay attention to the gap between the leading edge of that new flap and the trailing edge of the wing. That gap should not be there with the flaps up. When the flaps are down there should be smooth flow behind the wing and over the leading edge of the flap's slat. Perhaps they are going to add a fairing like the PA-18 uses? The shape of the trailing edge of the wing has a great deal of influence on how the air flows over the flap.

I have wondered myself how a slot would work built into the flap such as this. It will be interesting to learn what their flight testing determines.

Farmboy · Aug 12, 2018

RVBottomly said:
I found this on the Rans website regarding teleflex for flaps.

View attachment 36802

It comes from the discussion of the S-21 Outbound. Scroll down to 3/29/17 entry:

https://www.rans.com/21-outbound-progress-page-2

I notice that flap deployment is in a pull configuration on a bellcrank. I remember the telexflex "Xtreme" cables can handle an 8" bend radius.

Old thread, but a little additional info on Teleflex Xtreme - certain boat mfg's used them almost exclusively in their models, while typical marine distributors did not stock any of the Xtreme's. The difference to the std teleflex is the Xtreme cable has many more small "wires" forming the cable, where the non-Xtreme cable has fewer, larger, "wires" forming the cable. This allows the Xtreme cable to bend smaller radius's, but I would not recommend using it in a 8-9" bend radius. The big benefit was smoothness of the cable in it's action, and less resistance from small S-curve type routing in the engine bays or stringers. Highly recommend them.

CharlieN · Aug 12, 2018

One thing I like with the Telexflex "Xtreme" cables is the reduced friction compared with most other push-pull cables. I run with a foot throttle in my boats and the added sensitivity is greatly appreciated.

stewartb · Nov 7, 2018

Update on my own flaps. My flap handle was set up like a Cessna. Thumb button to pull, thumb button to release. The ability of the ratchet to engage the respective notches was inconsistent, and that was a problem. The solution? The full loop control cable is gone. I used a dual spring with a yoke at both bell cranks (original unequal arm type) in both wings. The flap ratchet is back to standard Cub. Pull up with no thumb button, thumb button required to retract. The flaps work much better now. They sag a couple of degrees in the tiedown but that sag disappears with airspeed. I use flap-aileron locks so no issue when parked outdoors. My flaps are easier to deploy and I have MUCH better control of the positions at the lever. My left flap has had a persistent degree or two sag when retracted and that’s gone. The plane flies better in cruise and control to landings is much better. Flap handle pressure is manageable. The spring pressure on the ground is higher than stock Cub but in flight I don’t have any problems with it. All the comments about speed and flap pressure are correct, although overstated, but at any rate I’m not having any problem with mine, but I’m not a small guy. The gear effect of flaps rotating the nose down is absolutely linear. That was demontrated best when my flap ratchet wouldn’t stay engaged. That made for some interesting landings. All better now.

scaleram · Feb 20, 2019

Slotted flap deployment force

KelvinG said:
Using teleflex cables is an interesting idea. It would really simplify moving a flap handle from the floor to overhead. Thinking about it beings a couples of questions to mind.

Any idea of the force required to deploy flaps? That would dictate the size \ weight of push-pull cable required.

Why push-pull cables? They have load limits in 100s of pounds. Plain pull cables(i.e. brake cables) are rated in 1000s of pounds, are lighter than push-pull cables and would still get rid of the Y splice and flexing pulley issues.

Sent from my SM-P900 using SuperCub.Org mobile app

I can tell you that the force to actuate the Keller flaps is huge compared to my old stock flaps. This is on a one-off Cub/Cruiser hybrid that I built. The Airframes Alaska supplied manual says to not deploy full flaps over 70MPH. I decided to not deploy any flaps above 65. I have three detents in the flap ratchet pawl. The last detent will extend the flaps to the maximum angle. The position of my flap handle is not ideal and it requires that to get full deployment the handle ends up behind the pilot. The force required to get the last notch makes it almost impossible to get. I even tried slowing the airplane to 45 and the force is still extremely high.

Since my airplane is experimental, The didn't supply the doublers required by the STC. I was and still concerned that this should be a necessity on all kits. There is a huge load on the flap hangers with these flaps.

Testing that I did with the second notch did produce significantly lower stall speed and deck angle. The manual states max deployment angle of 50 degrees on the second section. With the second notch I get 30 degrees and that is where I did my testing.

BTW: Bill Rusk is right about what I call a point of diminishing returns when you install slat and slotted flaps. Consider where each is designed to work. The flaps are designed to work at lower angles, whereas the slats work at higher angles.

skywagon8a · Feb 20, 2019

scaleram said:
BTW: Bill Rusk is right about what I call a point of diminishing returns when you install slat and slotted flaps. Consider where each is designed to work. The flaps are designed to work at lower angles, whereas the slats work at higher angles.

The double slotted flaps would be my first choice. However as they slow your plane way down the angle of attack will increase to the point where leading edge slats will begin to become a benefit. This even though the pitch attitude is fairly level. Tie a piece of yarn on your jury strut and notice what happens as you slow down.

stewartb · Feb 20, 2019

scaleram said:
BTW: Bill Rusk is right about what I call a point of diminishing returns when you install slat and slotted flaps. Consider where each is designed to work. The flaps are designed to work at lower angles, whereas the slats work at higher angles.

Do you have time with the slat-split flap combination? The combination is incredible for slow flight in a useful attitude. How slow are you able to wheel land?

scaleram · Feb 20, 2019

stewartb said:
Do you have time with the slat-split flap combination? The combination is incredible for slow flight in a useful attitude. How slow are you able to wheel land?

I don't. I look at it as a point of diminishing returns. The split flaps add about 12 pounds over the stock version. The slats add about 10. That means that with both, you would be adding close to 25 pounds to the airplane for maybe another 1 or 2 MPH decrease in landing speed. Additionally, I'm more interested in the deck angle because I operate on floats a good bit of time. If I carry power into a wheel landing, I'm indicating about 23. That's on wheels. I haven't flown it on floats with the flaps.

PS: I don't have vortex generators. I do have scars on my hands to prove that I have used them. That's next.

stewartb · Feb 20, 2019

I haven't flown floats for 10 years and haven't wanted to until I flew my Rev. Slats and split flaps and lots of horsepower would take me places my other floatplanes couldn't dream of going. To each their own. What slats weigh they more than make up for.

KelvinG · Feb 20, 2019

stewartb said:
I haven't flown floats for 10 yearsand haven't wanted to intil I flew my Rev. Slats and split flaps and lots of horsepower would take me places my other floatplanes couldn't dream of going. To each teir own. What slats weigh they more than make up for.

I'm still putting my retirement project together. But that makes me hopeful I'm heading in the right direction!

Thanks

Sent from my Pixel 3 using Tapatalk

CamTom12 · Feb 20, 2019

scaleram said:
I don't. I look at it as a point of diminishing returns. The split flaps add about 12 pounds over the stock version. The slats add about 10. That means that with both, you would be adding close to 25 pounds to the airplane for maybe another 1 or 2 MPH decrease in landing speed. Additionally, I'm more interested in the deck angle because I operate on floats a good bit of time. If I carry power into a wheel landing, I'm indicating about 23. That's on wheels. I haven't flown it on floats with the flaps.

PS: I don't have vortex generators. I do have scars on my hands to prove that I have used them. That's next.

There’s a really common misunderstanding that airplane deck angle always equals wing Angle of Attack.

Once you deploy flaps, the wing AoA and fuselage angle change with respect to each other.

It’s possible (and pretty common) to have very high wing AoAs with advanced flaps, like the double slotted flaps and pretty reasonable fuselage pitch angles. Slats would work at those higher WING AoAs (and much lower fuselage pitch attitudes) to help the wing continue flying.

If you don’t believe me or any of the guys routinely flying slat/slotted flap combos, go do a test: go fly your plane at a constant airspeed in the white arc and different flap settings and note your FUSELAGE pitch angle for each.

This is a surprisingly common misunderstanding.

VGs and slats do the same thing, but in different ways. VGs create a vortex over the wing. As the vortex travels aft, it spreads out vertically and traps some of the high energy, free stream air above the boundary layer and pulls it down. This re-energizes the boundary layer and helps it stay attached to the wing longer at higher wing AoAs. Slats accelerate the air traveling over the leading edge, giving it higher energy and helping it stay attached to the wing longer at higher wing AoAs. If you believe in one, you believe in both. But adding the extra weight and the cruise drag penalty of the slats is another decision that needs to be weighed.

Also, words have meanings. A split flap is different than a slotted or double slotted flap.

stewartb · Feb 20, 2019

stewartb · Feb 20, 2019

KelvinG said:
I'm still putting my retirement project together. But that makes me hopeful I'm heading in the right direction!

Thanks

Sent from my Pixel 3 using Tapatalk

You have good reason to remain energized!

mike mcs repair · Feb 20, 2019

stewartb said:
I haven't flown floats for 10 years and haven't wanted to until I flew my Rev. Slats and split flaps and lots of horsepower would take me places my other floatplanes couldn't dream of going. To each their own. What slats weigh they more than make up for.

maybe those float fitting you didn't order & want will be put to use?? amphibs??? does your new to you hanger fit you in on them?

skywagon8a · Feb 21, 2019

scaleram said:
I don't. I look at it as a point of diminishing returns. The split flaps add about 12 pounds over the stock version. The slats add about 10. That means that with both, you would be adding close to 25 pounds to the airplane for maybe another 1 or 2 MPH decrease in landing speed. Additionally, I'm more interested in the deck angle because I operate on floats a good bit of time. If I carry power into a wheel landing, I'm indicating about 23. That's on wheels. I haven't flown it on floats with the flaps.

PS: I don't have vortex generators. I do have scars on my hands to prove that I have used them. That's next.

I agree with you. My Cub has extended squared off wings with 110" long otherwise stock flaps and a smooth wing leading edge extended skin on floats. It routinely operates comfortably in and out of a 1000 foot long pond with 30 foot tall trees on each end. It can clear the trees on take off by the 2/3 mark. It would be able to operate in a no obstacle 600 foot pond. Why add weight and drag for the possibility of losing cruise speed? There are a couple of PA-12s here on wheels which have difficulty keeping up. It has demonstrated 28 mph on the gps with no wind before landing tail low in the water. Slats alone would only raise the nose more, landing water rudders first (not a good idea). It's the forward section of the floats which are stressed for landing loads.

stewartb · Feb 21, 2019

I wonder how your opinions would change if you had some time in a Cub with slats and improved flaps? At least you’d have a basis for your opinion. That would be refreshing. If you don’t want them? No big deal.

Steve Pierce · Feb 21, 2019

scaleram said:
I can tell you that the force to actuate the Keller flaps is huge compared to my old stock flaps. This is on a one-off Cub/Cruiser hybrid that I built. The Airframes Alaska supplied manual says to not deploy full flaps over 70MPH. I decided to not deploy any flaps above 65. I have three detents in the flap ratchet pawl. The last detent will extend the flaps to the maximum angle. The position of my flap handle is not ideal and it requires that to get full deployment the handle ends up behind the pilot. The force required to get the last notch makes it almost impossible to get. I even tried slowing the airplane to 45 and the force is still extremely high.

Since my airplane is experimental, The didn't supply the doublers required by the STC. I was and still concerned that this should be a necessity on all kits. There is a huge load on the flap hangers with these flaps.

Testing that I did with the second notch did produce significantly lower stall speed and deck angle. The manual states max deployment angle of 50 degrees on the second section. With the second notch I get 30 degrees and that is where I did my testing.

BTW: Bill Rusk is right about what I call a point of diminishing returns when you install slat and slotted flaps. Consider where each is designed to work. The flaps are designed to work at lower angles, whereas the slats work at higher angles.

How long are your flaps. I have installed 5 sets of the certified flaps and have seen no difference in the effort needed for deploying them.

KevinJ · Feb 21, 2019

Steve Pierce said:
I have installed 5 sets of the certified flaps and have seen no difference in the effort needed for deploying them.

Five more sets and you might have this install deal figured out

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