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

  1. #41
    Jerry Burr's Avatar
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    Hi Wayne. Last # that I had was. 907-346-1396. That is for Dennis. Jerry.

  2. #42
    Mark Lund's Avatar
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    Bigger leading edges?

    I see the North Star web site says that they extend their leading edges back 4" past the front spar. This is supposed to help maintain the shape of the airfoil and I suppose enhance performance. What are your thoughts about this mod? Should a person leave well enough alone?

    Mark

  3. #43
    Wayne Mackey's Avatar
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    Leading edge

    Mark , This is good question . This is something that went through the area of Alaska
    I lived in during the 70's. I have done one of these mods my self and around a few
    others. They look good, but we didn't gain a thing except weight. And labor. On the
    one I did we lost some take off perfomance. I can't say it dosn't work for some, But I
    would spend my time and money somewhere else. A while back there was a picture
    of a C.C. yellow cub on the front of a magazine that showed the top of the plane in
    flight and all the fabric between the ribs was balooned up to the shape they are
    after with the added leading edge. So when you are under a positive load it appears
    to me there isn't any need for this mod. My opinion only by what i have seen.
    Wayne

  4. #44
    SuperCub MD's Avatar
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    That is a good question. I have been told by those that used to dust with J3's that a wood spar 3 would always carry a larger load than a metal spar 3. The biggest difference aerodynamically is that the wood spar LE stops well in front of the spar, allowing the fabric to dip way down between the ribs when sitting on the ground. But maybe it also ballons up higher in high lift situations?, and this "flexable" airfoil may actually be better? The wood spar Cubs are usually a little lighter, but not enough to make a real big difference in hopper load.

    Also, maybe Wayne knows, Why did Piper keep useing the short LE outboard section on all the later J3's, PA11, and PA18. They went to the long LE on the J5, PA12/14, but it stayed short on the OB on the other models, there must be a reason. I asked this somewhere before, and no one seems to know.

  5. #45
    Wayne Mackey's Avatar
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    Leading edge

    Mark,
    I don't really know the facts about the full leading edge on a cub not going all the way
    out to the tip. It always looks odd when you do a wing exstenion. At one time I was
    told that the full leading edge was added to help support the main spar. since the
    main load is just inboard of the strut attach it may not have been needed outboard.
    I don't remember who said this so , take it with a grain of salt. Wayne

  6. #46
    PA12driver's Avatar
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    stands to reason? that the leading edge extention would give extra support to the spar/tank bay as well as there is the prop blast over that area as well?? I have heard the J3 duster dialog before and it make a lot of sense. Also I think that the flexibility of the grade A/nitrate may have allowed this, the adhesion problem with buturate/ceconite especially if the fabric doesn't get saturated caused in the 70's a lot of fabric/dope failures?

    Also Ureathane painted cubs would crack badly on the ribs just aft of the spars if you remember? (perhaps fixed now with better flex additives?

    By the way do you know how much less a std. cub wing weighs versus a dakota wing?

    Tim

  7. #47
    Wayne Mackey's Avatar
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    Leading edge

    Had a freind build an over sized exper. cub in Ak. during the 80s. It had huge flaps
    and drooping ailerons. On rotation with flaps on take off the fabric between the ribs
    would baloon up a good 1/2" above the ribs. If memery serves I think the ribs were
    about 20" apart. I know this wasn't a cub wing but the point being made is the same.
    Wayne

  8. #48
    Steve Pierce's Avatar
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    Tim, Dakota Cub http://www.dakotacub.com/ wing ribs weigh about 7 lbs more than stock Piper ribs but being made of an extrusion are stronger. They have changed their website and have some good tech articles on building wings.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  9. #49
    PA12driver's Avatar
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    Thanks Steve! I have a friend with a severly damaged wing and his concern was;, would he have to build the wing with the "old" sty ribs to balance with the other one? Awefully time consuming to repair a lot of damaged ribs.

    Tim

  10. #50
    Steve Pierce's Avatar
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    Tim, I've never weighed a cub or any other airplane that was even close to being the same weight on both main scales. The last one I weighed was about 60-70 lbs difference. Don't ask me why, I have yet to figure it out. One suggestion though. The Univair ribs can be disassembled and installed without removing all of the ribs and disassembling the whole wing. I don't know how bad the wing is but they make the repairs go alot quicker in this case.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  11. #51
    Wayne Mackey's Avatar
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    Door chanel

    Question Guy's,
    Talking about the peices of chanel that covers the tubing around the door frame
    on a supercub. Has any one come up with a good methed of getting a good coating
    of paint under. If it is prepainted it gets burned when tacking on the chanel
    Wayne

  12. #52
    Steve Pierce's Avatar
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    Tom Hegy put lightening holes in his Experimental PA-12. There was a good article in the Cub Club Clues w/pictures.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  13. #53

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    Wayne or any one
    If after we install all of the STOL mods to the wing and we get it flying 20% slower than stock, does the tail surfaces have enough area to still control the SC in slow flight, or should we increase the tail area? I have just began building a PA12 and would like to make a few of the mods to the wings.
    Eddie

  14. #54
    Wayne Mackey's Avatar
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    Tail feathers

    Eddie,
    The SC tail should be good for what you want. The only time we have come up
    short is with a nose heavy airplane with large flaps and droop ailerons. These
    flaps and ailerons cause a big pitching moment with the power off. But this is a
    good Question, the slower you fly the less affect your controls will have. Wayne

  15. #55
    Guest
    Thanks Wayne, I have another question for you. I have been doing some studies on wing slots myself and I understand the theory of the slot, but I haven't found anything on the size of the slot. What is the ratio of the lower wing slot gap to the top? I understand the top needs to be smaller to give it a venture effect and energize the boundry layer, but I haven't found any figures on it. Also would it be desirable to have a gap between the flap and the wing when it is in the down position to help prevent the flap from stalling?

  16. #56

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    Sorry Wayne I forgot to sign my post above.
    Thanks Eddie

  17. #57
    PA12driver's Avatar
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    Eddie, Wayne,

    Good posts great information and questions, I have the same question? gap between the flap and trailing edge of wing when the flap is down? The PA12 has a much larger "flap gap" (now gap seal from the factory??) I would like to hear the explanation for this difference?

    Thanks

    Tim

  18. #58
    Wayne Mackey's Avatar
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    Flaps slats

    Eddie Tim,
    On a 18 there is a trailing edge peace of alum. that turns the air down over the top
    of the flap. Jerry Burr has done quite a bit of testing here and I've done a lot of
    studying of his vidio's. I beleave this is important area in controling not only the air
    on top of the flap but the air forward of the flap on top of the wing. Maybe we can
    get a little input from Jerry. He has these peaces of alum. the full length of his wings
    and we all know there is nothing on his cub that dosn't carry it's weight.
    As for the slats the inlet and outlet sizes are 4 to1 or 3 to1. This can very quite a
    lot and still work. I my self am closer to 2 to 1 but can only do this because of the
    way they move. If they were fixed in position cruise would be 65 to 70 mph. Not
    practictal. Wayne
    Thanks Jonnyo thanked for this post

  19. #59

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    Thanks again Wayne. I didn't realize that the slot created that much drag in the fixed position.
    Eddie

  20. #60
    Wayne Mackey's Avatar
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    Slat

    Eddie,
    That speed was refiring to my slat and when it is fully open. With the fixed
    slats and normal opening I only lost 8 to 10 mph. That was still with my slat and it
    is larger than most. I don't know the numbers on the other slats out there. The way
    I build and use the slat has changed over the years and now lose only 2 or3 mph.
    we have three 18 type out there that cruise from 95 to 105 depending on HP.
    They all have long gear big tires and long wings. The fastest has gear that is 14"
    longer than standard and 30" tires. Wayne

  21. #61
    Guest
    Barnes McCormick's text, Aerodynamics, Aeronautics, and Flight Mechanics, has information on slots, slats, leading edge flaps, and Kruger leading edge flaps on pages 113-120.

    Slots can provide a CL increment on the order of 0.1-0.2
    Slats can provide a CL increment on the order of 0.9
    Leading edge flaps and Kruger leading edge flaps can also add an increment of about 0.9.
    A Kruger leading edge flap combined with a split trailing edge flap can give a total CLmax on the order of 3.0, which is about 0.3-0.4 higher than the leading edge devices acting alone.

    JimC

  22. #62
    Cubus Maximus's Avatar
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    In the, "for what it's worth" department...

    I flew in Dakota Cub's slotted wing Cub.

    2 people
    160 hp
    Borer 41
    EDO 2000 Floats
    Slotted Wing

    Cruise was 95 mph

    (of course we all know how accurate a Cub's airpeed indicator is - but it moved right out)

    Brad

  23. #63
    Steve Pierce's Avatar
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    Jim C, What is the definition of CL?
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  24. #64
    Wayne Mackey's Avatar
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    Stol devises

    Jim C,
    I have read every book and artical I could get my hands on and have learned a lot.
    Everything tested that I read about worked with higher wing loadings than a light cub
    and at air speeds above what we are doing. I know this will muddy the water for
    some but through testing we found some new laws that work quite different at the
    speeds and weight we are dealing with. When you get below 20 mph you can no
    longer compress air through a slot / slat very well. The whole mass of air will back
    up and go around the out side of the slat. This is all done at very high angle of attack
    and with high power as you plow ahead. you will get a lot of lift with the eng.
    pointing up fighting the lift and drag of the wing. Wayne
    Thanks Jonnyo thanked for this post

  25. #65
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    Steve P , I know you probably alreay know cl=coefficient of lift and were probably wanting a more in depth explanation. This site puts it all in terms someone as aerodynamicly challenged as me can get! probably too basic but maybe someone can benifit from it? Rob
    http://www.planemath.com/activities/...irfoils24.html

  26. #66
    Rob's Avatar
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    Yea... looking back at it again that mighta been a little too basic ...sorry , Rob

  27. #67
    Guest
    Steve, CL is a proportionality factor, the coefficient of lift. It is equal to the lift divided by the product of the dynamic pressure and the reference area..

  28. #68
    Guest
    Wayne wrote:
    > I have read every book and artical I could get my hands on and have learned a lot. <

    I wish I could say the same. I'm eaten alive with ignorance.

    > Everything tested that I read about worked with higher wing loadings than a light cub and at air speeds above what we are doing.<

    You might try the Journal of Experimental Biology. It deals a lot with lower wing loadings and airspeeds than most of the aeronautical journals. And the Journal of Vertebrate Paleontology deals some with animals about the size, wing loading, and speed of our planes. I work mostly on the aerodynamics, flight mechanics, and flapping kinematics of a couple of late-Cretaceous azhdarchid pterodactyls, one of which is about the size of a Cub, though a bit lighter.

    > I know this will muddy the water for some but through testing we found some new laws that work quite different at the speeds and weight we are dealing with. When you get below 20 mph you can no longer compress air through a slot / slat very well.<

    I agree. Air is usually treated as essentially incompressible below speeds of about Mach 0.4. And low Reynolds number flight performance is quite a bit different than flight performance at higher Reynolds numbers too.

    > The whole mass of air will back up and go around the out side of the slat.<

    This is to be expected, as the stagnation point shifts down and aftward at high aoa.

    > This is all done at very high angle of attack and with high power as you plow ahead. you will get a lot of lift with the eng. pointing up fighting the lift and drag of the wing. Wayne<

    I agree re drag. But with the engine pointing up, isn't the downward component of the engine thrust helping some with the lift?

    I've always been much impressed with what you and Jerry know about slow flight in small aircraft. My slow flight studies are more oriented toward flapping wings and unsteady flows.
    All the best,
    JimC

  29. #69
    Wayne Mackey's Avatar
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    Up thrust

    Jim C,
    Sorry for the miss understanding, you are correct. The point I was trying to make
    was that with the eng. pulling up in the front and the wing producing lift and drag
    up and back the weight is being divided between the eng. thrust and the wing.
    Therefor your wing has a lower weight per sq. ft. when under power. Of the
    three 18 type I spoke of the one that is the heavest has the most hp. and fly's the
    slowest under power.
    By your thoughts I don't beleave any one could say you are ignorant. And I don't
    in any way think I have it all together. I just like to play with what I love SLOW
    FLIGHT! Thanks for your input. Wayne

  30. #70
    Wayne Mackey's Avatar
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    Books

    By the way the books I was talking about were only in the airfoil, slot, slat, or flap
    department. I have by no means read every thing avalable. Wayne

  31. #71

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    Wayne
    I would be interested in some of your favorite books on this subject. Could you list a few of them.

    Eddie

  32. #72
    Jerry Burr's Avatar
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    Books.

    Hi Eddie. Never fear. You have not been forgotten. Wayne has most of his books stored here. And he has read all of mine also. I was digging through boxes, and discovered a lot of my old test data. So I got sidelined trying to figure a way to get some of this stuff posted. I'm working on your request also. Please bear with me. Jerry.

  33. #73
    Guest
    Jerry, if you would like to place any of your data on a page or pages on either of my two websites, you'd be more than welcome to do so.

    www.tailwindfairings.com
    www.cunninghameng.com

    All the best,
    Jim Cunningham
    Cunningham Engineering Assoc.

  34. #74

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    Thanks Jerry
    Please dont go to a lot of trouble. I enjoy reading about our hobby but haven't been able to find very many good text books on the engineering of the wings and STOL devices.
    Eddie

  35. #75
    Wayne Mackey's Avatar
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    books and articals

    Hi eddie'
    Sorry it's been so long in reply on your note. I have been really busy trying to get
    a cub out of the shop that got behind. To many add ons, but it flew away yesterday.
    Turned out to be a real good performer. On the books as jerry said all of my things
    are stored away. But you can get quite a lot out of library's. I have picked out a
    particular plane like the Custer Channel Wing CCW 5 and found some really good info.
    I,m new with a comp. but I have found a lot with the search mode. I have also
    barowed a lot of books and read what I was interested in and gave them back.
    There are many stol devices that really work well but very few that can be put on
    a cub type aircraft dew to weight and structure. Over the years that I have been
    playing with this I have tried to pick out all the things I like on different airplanes and
    incorperate them into a single plane. I'm shore I will get to old to do it all, But will
    have fun. There will allways be something else. Wayne

  36. #76

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    Thanks again Wayne
    Glad you got the cub flying.
    Eddie

  37. #77

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    Gurney flaps.

    Wayne or Jerry,

    Do you guys have any experience with Gurney flaps? There is an article in "Custom Planes", May 2002 about a slow flying Cub with these high lift devices. It is a 3/4" stip of metal mounted in a downward position on the trailing edge of the wing, outward from the ailerons.

    This Cub also has 3/4" tall VGs instead of the normal 1/4".

    Hans

  38. #78
    Jerry Burr's Avatar
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    Flaps.

    Hi Hans. Talked to people who have used them, they are used mostly for banner towing. Where they want to spend most of the day at 40-45 mph. Can you post the ariticle? Jerry.l

  39. #79
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    experimental cubs

    Have you seen the latest issue of Northern Pilot, pretty interesting stuff! Company called Performance Air is putting out a supercub kit dubbed the Copycat Cub. Kit is all inclusive, less engine, prop, n covering materials!It got pretty high praise from the folks at NP. I was intrigued by there use of coil spring suspension in place of the hydro-bungee system on cert. cubs.Sure looks alot cleaner n aerodynamic. Any opinions, better, worse,safety, ? Curious because my newly built cub sits left wing low.New landing gear legs n struts nbungees. Only measurment that is diff. is the hydrosorb assemlys themselves, any insight as to why? they were measured with no weight load n 1 is 5/16 longer!

  40. #80
    RedEye's Avatar
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    experimental cubs

    Nothern Pilot never did get into any #s as far price of the kits n PerformanceAir didn't list a web site, sure be interesting to see what theyre asking. I built my cub from scratch,started with only my paperwork n my engine! Have all receipts n invoices, would be interesting to compare price! This also adds another factor to the question to "buy new topcub, rebuilt SC or now build experimental cub?" If money is no object its pretty simple, but for most of it is, " make house payment or buy fuel for cub" !!

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