Inboard flaps

Spdcrazy

Spdcrazy

Non-Member
Homer Alaska
Is the leading edge cuff stc the only way to achieve the flaps coming all the way to the fuselage? Would the extra couple inches inboard alone be worth the work to do if there is a way to do it legally?

of course I want to build them out further when I square off the wings but... so maybe I should work to get that extra bit out of the inboard section?
 
Spdcrazy said:
Is the leading edge cuff stc the only way to achieve the flaps coming all the way to the fuselage? Would the extra couple inches inboard alone be worth the work to do if there is a way to do it legally?

of course I want to build them out further when I square off the wings but... so maybe I should work to get that extra bit out of the inboard section?
Click to expand...

I called XWinds about the inboard extension. Since I was not interested in the cuff, they said once you own the STC you can do the flap mod without doing the cuff. I added the inboard extension when I did the super Pacer stretched STC. I have 92 inches of flap. That made a difference. I instantly slow the plane down and have a very nice nose down attitude. While I would do the extension on a stock Pacer flap I don't know the effect. I can't remember what a stock Pacer flat length is. 52 inches" adding 4 inches maybe be significant.

Who's STC are you using for the wing tip mod?
 
Stephen said:
I called XWinds about the inboard extension. Since I was not interested in the cuff, they said once you own the STC you can do the flap mod without doing the cuff. I added the inboard extension when I did the super Pacer stretched STC. I have 92 inches of flap. That made a difference. I instantly slow the plane down and have a very nice nose down attitude. While I would do the extension on a stock Pacer flap I don't know the effect. I can't remember what a stock Pacer flat length is. 52 inches" adding 4 inches maybe be significant.

Who's STC are you using for the wing tip mod?
Click to expand...
That is the way a lot of folks do it on Super Cubs as well.
 
I am doing the Stewart’s tip.

I’ll call about the crosswind kit. Will they sell the stc without the parts I wonder? And could/would the fence be helpful without the cuff but with vgs? I think I recall someone saying it didn’t slip well when the fence was added, and boy do I love a good slip.
 
Spdcrazy said:
I am doing the Stewart’s tip.

I’ll call about the crosswind kit. Will they sell the stc without the parts I wonder? And could/would the fence be helpful without the cuff but with vgs? I think I recall someone saying it didn’t slip well when the fence was added, and boy do I love a good slip.
Click to expand...

That's a good point about a fence. I agree, I like to be able to slip my plane. Post what you find out. I probably should buy the STC. It's just that I've got so many stcs on my plane and a pile of drawings for the stcs one would spend weeks to figure how one STC interchanges with another. When combining STC's, I usually can strengthen the plane beyond the original plane. My plane has been inspected by the FAA and multiple IA's, it always gets good reviews.
 
Charlie is out of town until tomorrow. I’ll learn up a bit and see what happens.

all of this started from the idea of carbon fiber root fairings. Randy asked if I was moving my flaps inboard. Sure, why not, add another mod to the giant project! Maybe.
 
I’ve looked at this a couple times for my tripacer but thought the angle of the fuselage where the full flap would intersect is poroblamic. That being said the amount of air bypassed could be significant although that air might be needed for rudder effectiveness at slow speed high angle of attack situations. Lots going on back there.


I think a molded cuff that slips on latterly say out of some sexy carbon fiber, lock the flaps at a full 40 and slide cuf inboard until it contacts fuselage and cherry rivet in place. Might need a rub plate or an extra layer of fabric in the fuse attached in such a way as to not have an edg to catch...

Rocket
 
CF is good for some things but not others flat plates will vibrate and blow out holes faster then you cans say, what was that? Also, get out the scale, if the CF is not saving you 25% then it’s not worth it. I did a lot of advanced composets in another life. Started with all molded carbon model airplanes and finished developing repairs for that 37/777. Cool stuff but not fun to work with, the good resins are deadly and sanding trimming fitting is um... itchy.

sure is easy and fast to lay up a one off with polyester resin though. Make first part out of glass then make the carbon one once you get an idea what you want.

Rocket
 
The root fairings save a little over one pound I am told. For the cost, could be worth it.

I just spoke to a buddy that is well versed in the pacer and this is what he had to say about moving the flaps inboard on a factory length pacer fuselage.

“DO NOT close the gap. Causes a big air burble over the horizontal and elevator and again you have no attachment of air and therefore you have no control. Your tail feathers go into a huge death wobble shaking flutter. Been proven time and again. LEAVE the gap as it is. Piper engineers did a perfect job on this one bro.”
 
Spdcrazy said:
The root fairings save a little over one pound I am told. For the cost, could be worth it.

I just spoke to a buddy that is well versed in the pacer and this is what he had to say about moving the flaps inboard on a factory length pacer fuselage.

“DO NOT close the gap. Causes a big air burble over the horizontal and elevator and again you have no attachment of air and therefore you have no control. Your tail feathers go into a huge death wobble shaking flutter. Been proven time and again. LEAVE the gap as it is. Piper engineers did a perfect job on this one bro.”
Click to expand...

Wow! I've not noticed any problems closing the gap inboard with my flaps. I do full flap hard slips, all types of stalls. I've never had death wobble shaking flutter. Piper engineering was good but, far from perfect.
 
Stephen said:
Wow! I've not noticed any problems closing the gap inboard with my flaps. I do full flap hard slips, all types of stalls. I've never had death wobble shaking flutter. Piper engineering was good but, far from perfect.
Click to expand...

is your fuselage not stretched?
 
Bender has the inboard flaps and I noticed no issue with them on his Pacer. Flies really nice and he gets it in most of the same places we put our Super Cubs. Didn't notice any Death wobble or lose of pitch control. It is the one Steve and Brian Pankonin replaced the fuselage on a few years ago that is cream and light blue that I post pictures of from time to time. I have flown a lot of Super Cubs with and without flaps inboard to the fuselage. On some the stick will dance a little when you are really slow but i have only noticed it on a few and always had full pitch control. I get it on some of the Super Cubs (10 total) that I have installed Performance STOL flaps on but not all. Again, always have pitch control. Personally I want all the flap area I can get especially on a Pacer.
 
Last edited:
Steve Pierce said:
Bender has the inboard flaps and I noticed no issue with them on his Pacer. Flies really nice and he gets it in most of the same places we put our Super Cubs. Didn't notice any Death wobble or lose of pitch control. It is the one Steve and Brian Pankonin replaced the fuselage on a few years ago that is cream and light blue that I post pictures of from time to time. I have flown a lot of Super Cubs with and without flaps inboard to the fuselage. On some the stick will dance a little when you are really slow but i have only noticed it on a few and always had full pitch control. I get it on some of the Super Cubs (10 total) that I have installed Performance STOL flaps on but not all. Again, always have pitch control. Personally I want all the flap area I can get especially on a Pacer.
Click to expand...

Does Bender have VG's.??.. Our 180 Pacer does with the inboard flaps and it does not shake.. Makes me wonder if the ones that shake don't have VG's installed..?

Brian.
 
That was my thinking as well steve. I will have the Pa18 tail anyways so that should help with any lack of authority I would expect. Wish I didn’t have to make a decision on these fairing first. I’d build a set of longer flaps and give it a whirl!
 
I have the full crosswind STOL kit on my plane (I don't have the aileron gap seals right now), as well a the droop tip that add an extra rib (some don't). I have about 800 hours in PA-22's and PA22/20 of every flavor. I can and do land regularly in 375ft. With taller gear, larger tires, or beating up my tailwheel, I could cut that down a little. I fly my plane as close to the edge of the envelope as any and closer than most. The plane slips great. It slips as well or better than a stock short wing. Excellent controllability right through stall. No "death" anything.
My plane came to me in this configuration and I love it. If I was to build another plane I would do VGs, gap seals, and extended flaps. I think that would yield the most improvement for the easiest modifications.
 
Marc Davis said:
I have the full crosswind STOL kit on my plane (I don't have the aileron gap seals right now), as well a the droop tip that add an extra rib (some don't). I have about 800 hours in PA-22's and PA22/20 of every flavor. I can and do land regularly in 375ft. With taller gear, larger tires, or beating up my tailwheel, I could cut that down a little. I fly my plane as close to the edge of the envelope as any and closer than most. The plane slips great. It slips as well or better than a stock short wing. Excellent controllability right through stall. No "death" anything.
My plane came to me in this configuration and I love it. If I was to build another plane I would do VGs, gap seals, and extended flaps. I think that would yield the most improvement for the easiest modifications.
Click to expand...
Marc, I'm just ignorant and hoping you can explain it to me. I've gone to the Crosswinds STOL site and find their explanations enticing, but a bit short on pictures to help me understand what they're selling with respect to the wingtips, specifically. I don't want to offend, but their website is a bit dated. Do you know where I can get more information on the wingtip mod and STC? What is involved to install? What is in parts package and paperwork for these wingtips. I know something about aerodynamics and these wingtips are very interesting to me and I'd like to know more about the installation and what they sell you in the kit. I am so ready to buy it if I knew more about it. Thanks.
-Subsonic
 
As I understand it, the Crosswind STOL kit consists of a leading edge cuff, stall fences, aileron and flaps gap seals, and flaps extended inboard. The wing tips for the PA-22 were not part of the STC or if they were, not many were installed. Most people installed Fergison tips because they extend the wing. These days there are better option from Sullivan and Svenn's. Both extend the wing and increase wing area. The droop tip is an older design with arguable benefits. There is an extensive thread on this sight about the available wing tip options. Field Guide to Shortwing Wingtip STC's

The Crosswind STOL kit is trying to reduce stall speed and maintain controllability at low air speeds.
The leading edge cuff adds a sort of a cup shape (camper) to the bottom of the wing which reduces stall speed.
Because of wing washout (twist), stalls start at root of the wing. Stall fences help to delay the propagation of the stall from the root to the tip. This means the area of the wing with the ailerons in it stalls last, helping with low speed controllability.
VG do both of these things and are a lot less invasive to install.

With the longer wing, the roll rate is slowed. Aileron gap seals are supposed to help with this. I'm hoping to make some before and after measurements on my plane at some point.

The extended flaps and flap gap seals help with stall speed. There are better ways of doing that with other types of flaps, like fowler flaps, but they are not available for or planes.
 
I think Mac is correct. Increase flap, add VG's, increase wing area with Sullivan or Svenn tips, add aileron gap seals and go to PA 18 stabilizer/elevator. Then reduce weight and up HP and get big prop. Now you've got a Cub killer.
 
I've also heard rumor's that adding a gap seal to the elevator makes a marked improvement to the elevator authority.
 
Marc Davis said:
I've also heard rumor's that adding a gap seal to the elevator makes a marked improvement to the elevator authority.
Click to expand...
I thought so, that rubber Cub Crafters sells is simple to install as well.

I will post some pictures of the Crosswind STOL tips. I maintain a pretty radical PA12 that Charlie rebuilt several years ago.
 
I'm not sure I could get used to those angulated and chopped off tail feathers on my plane.
 
That thing makes you want to take your hand off the throttle so you can use two hands to flare.
DSCF3879.webp
 
Okay...I’m doing the full Crosswind stol to my Pacer. The position of those VG’s is something else to ask about....the VG’s on that are way further forward.....in that my plan was....was...to use the micro-VG template that came with the VG kit to locate the line....Mark that line before installing the leading edge cuff..
So why install them there?...there isn’t anything in the instructions that came with the kit about VG placement.

Also...the crosswind stol kit fence locates on top of a rib...on a Pacer there isn’t a rib near the outboard end of the flap..

Also...I’m not extending the flap in board... if I had a do over..I’d install a Univair rib on the end of the wing to mount the Crosswind stol wing tip...

And those wing tips aren’t exactly concentric. Ignore the predrilled holes...get the wing tips positioned....if the holes line up great...odds are they won’t.

I used the pre drill holes on the top of the wing tip. Then set the position and drilled the bottom screw holes.. if I had tried to use one Dakota Cub...wouldn’t have line up.

Another thing I’m going to try.....disassembling the stall fences. Install the aluminum angle to the wing. Then rivet the stall fence..to the aluminum angle that is now secured to the rib profile...and do it carefully...don’t over squeeze the rivets. Both fences I received did not match the rib contour...I built one to match...riveted it together.. came out just like Charlie’s part...didn’t match the rib profile...dented the leading edge...


Sent from my iPad using Tapatalk Pro
 
As you probably know, the STOL kit and the VGs are two different STCs. There are some rules of thumb about how far back from the LE that VG's should be installed. To my eye they are too far forward on the pics Steve just posted. I doubt any testing has been done by the crosswind STOL guys or the VG vendor for this combo, so you are kind on your own for placement.

My gut says the inboard extended flaps are one of the more effective parts of the STC, but I have no real evidence. The super-cub guys are sure keen on the idea. Surprisingly I really don't see any fabric wear where the flaps touch the fuselage. It just scuffs the paint.

I don't think the location of the fences is critical. I would just pick the rib nearest to the recommended location.

My fences do not match the wing contour well. On mine there is a gap between the wing and the fence.
 
As to the gap between the flap and fuselage as it pertains to the Bearhawk. There was a discussion about this involving Budd Davisson who’s an aeronautical engineer and publishes allot of aviation related articles. On the Bearhawk both the designer and Budd were on the same page...keep the gap.... that it was critical for low speed rudder effectiveness. Want to say during a slip...but I can’t be sure if I remember that correctly.

To bad I can’t put VG’s on the vertical stabilizer to improve rudder effectiveness like it does on a Cessna.

I’ll reach out to Budd and ask about the VG placement with that cuff installed.


Sent from my iPad using Tapatalk Pro
 
The Micro VG's are different between Cubs and Pacers... The Cub VG is smaller (shorter) and farther forward on the wing... The Pacer VG is bigger (longer) and farther back on the wing... On our Cuffed wing of the Pacer we used the micro placement tool for the Pacers and put them at that location... Dad also made his own fence that matched the wing contour and a little shorter in height..

Brian
 
I am pretty sure Jerry Burr has the VGs on his cuffed wing on his Cub. He is the one who got Micro to look into VGs on our type aircraft and did all the flight testing. He can probably has some insight to their placement on the cuff.

I have never run out of rudder on a Short Wing Piper, way more effective than my Super Cub. Not sure VGs up the vertical would be a benefit. One thing I have learned about engineers and engineering, there is theory and there is real world. Sometimes they are the same but sometimes they are not.
 
Steve Pierce said:
I am pretty sure Jerry Burr has the VGs on his cuffed wing on his Cub. He is the one who got Micro to look into VGs on our type aircraft and did all the flight testing. He can probably has some insight to their placement on the cuff.

I have never run out of rudder on a Short Wing Piper, way more effective than my Super Cub. Not sure VGs up the vertical would be a benefit. One thing I have learned about engineers and engineering, there is theory and there is real world. Sometimes they are the same but sometimes they are not.
Click to expand...

Jerry has VG's on both the top and bottom of his cuff. I don't remember about vertical fin. He also has flaps inboard. He lands in 30 feet. His plane in a 100 hp J3.

Btw, he just finished rebuilding a basket case SC for his wife. It's beautiful.
 
We had a long discussion under the wing at Oshkosh a few years ago about the VGs under the wing, automatic transmission fluid etc. ;) I always enjoy visiting with Jerry and I hope to see Becky's Super Cub this next year. Jerry and I have conversed about it a few times and glad to hear they got it flying.
 
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