Results 1 to 35 of 35

Thread: Cruise performance

  1. #1

    Join Date
    May 2014
    Posts
    520
    Post Thanks / Like

    Cruise performance

    I recall an old thread that discussed cruise performance of cubs - speed penalties for different mods etc.
    I regularly fly with a friend with a bone stock cub, 1500+ hr 150 hp, only mods are a 82/42 borer and 29"s.
    if were both cruising at 2450 (both using digital tachs) hes got about 8 mph on me.

    Im flying a recently rebuilt cub, rigged to spec, 70 lbs lighter, 160 hp (port/polish lycon), 82/43, 3" ex gear (uncovered), bags over my hydrosorbs, 31", bby bushwheel. 2450 im about 87mph 1500 msl 70*.
    I would have figured turning a 43 pitch prop at the same rpm (and burning alot more fuel) would even things out. Guess not.

    Anyone have data on common mods and associated speed penalty?

  2. #2
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    8,987
    Post Thanks / Like
    What is your loaded CG when compared to his while flying together? The plane with the further aft CG will have less drag.
    N1PA

  3. #3
    SJ's Avatar
    Join Date
    Jan 2002
    Location
    Kansas City, USA
    Posts
    14,375
    Post Thanks / Like
    Things that have made a difference in my limited experience:
    1. Tire size can make a huge difference
    2. Uncovered gear
    3. larger tailwheel
    4. Two many gopros

    sj
    "Often Mistaken, but Never in Doubt"
    ------------------------------------------

  4. #4
    sjohnson's Avatar
    Join Date
    May 2002
    Location
    Boise, ID
    Posts
    649
    Post Thanks / Like
    Data point
    160 hp, 82/43, 31" Bushwheels, standard covered gear, Scott tailwheel, 2450 rpm, 2000 AGL: 94 mph TAS

  5. #5
    Farmboy's Avatar
    Join Date
    Jan 2016
    Location
    Glens Falls, NY
    Posts
    2,001
    Post Thanks / Like
    Reminds me of this.

    https://youtu.be/ftq8jTQ8ANE

    Round tubes are not aerodynamic.
    Thanks aviationinfo thanked for this post

  6. #6

    Join Date
    Dec 2006
    Location
    Meanwhile,...
    Posts
    4,928
    Post Thanks / Like
    SJ time for a new bumper sticker: "Super Cubs make a Harleys look streamlined!"
    Last edited by OLDCROWE; 11-28-2016 at 03:38 PM.
    Remember, These are the Good old Days!
    Likes pfm liked this post

  7. #7

    Join Date
    Feb 2002
    Location
    don
    Posts
    666
    Post Thanks / Like
    Can,t stand less than 100mph in an airplane. Aren,t those 35,s just wonderful. If you got to have em, recalibrate to kilometers/hour.

  8. #8

    Join Date
    Sep 2003
    Posts
    6,580
    Post Thanks / Like
    1950 manufacture: flaps, 160 engine, cruise prop, 8:00x6+Clevelands, radio and xpdr, no other mods - 115 mph at 7.5 gph. It has since received several bush- style mods and now cruises around 97. It is still a wonderful airplane, but I liked it better before the bush mods.
    Likes pzinck liked this post

  9. #9

    Join Date
    Dec 2006
    Location
    Meanwhile,...
    Posts
    4,928
    Post Thanks / Like
    Quote Originally Posted by bob turner View Post
    1950 manufacture: flaps, 160 engine, cruise prop, 8:00x6+Clevelands, radio and xpdr, no other mods - 115 mph at 7.5 gph. It has since received several bush- style mods and now cruises around 97. It is still a wonderful airplane, but I liked it better before the bush mods.
    The real reason we hang all that stuff on our Super Cubs is so we can justify a Skywagon for trips!
    Remember, These are the Good old Days!
    Likes pzinck liked this post

  10. #10
    mvivion's Avatar
    Join Date
    Jun 2003
    Location
    Bozeman,MT
    Posts
    10,312
    Post Thanks / Like
    In my experience, there is often significant differences in cruise speed (and other performance parameters) between similarly equipped cubs. Some I was never able to explain.

    These are old airframes and many have been tweaked, rigging can be all over the place, angle of incidence of the wings can vary a bit, etc, etc.

    Theyre all a little different. So be it.

    MTV
    Likes pzinck, pfm liked this post

  11. #11
    Tim's Avatar
    Join Date
    Feb 2002
    Location
    Petersburgh, NY
    Posts
    3,463
    Post Thanks / Like
    Anyone have any idea how much difference it would make taking the dihedral out of a cub wing. I'm sure it would make it a little faster and fly slower, but how much?

  12. #12

    Join Date
    May 2014
    Posts
    520
    Post Thanks / Like
    Prior to cubs, spent alot of time in a Maule. Often switched back and forth between 8:50"s and 31"s.
    about 8 kt difference but what i noticed was the wing AOA at level cruise and the different elevator position.
    31"s created so much drag under the plane that to compensate, you were trimmed back to a higher AOA at level flight.
    Im sure that flight attitude cost a couple knots along with aerodynamic drag of tires.

    Re Cub, Considering covering gear and installing original bungee covers if I could gain a few knots...

  13. #13

    Join Date
    Jan 2007
    Posts
    1,572
    Post Thanks / Like
    You should fly faster and slower if you take some of the twist out of the wing. Dihedral should effect stability more than speed, The slower you want to fly the more stability you will want.
    DENNY

  14. #14

    Join Date
    May 2010
    Location
    On a rock in the North Atlantic, aka Britain!
    Posts
    15
    Post Thanks / Like
    1960, 160hp, 74/56 cruise prop, 8.50's,1125lbs, 2450 108mph, 8.1 us/gph (30lph) then I fitted 31's and bbw and saved a load of weight with electrical refit and other mods inc sutton exhaust under seat battery etc, weight saved roughly equalled added weight of ABW's . still with 74/56. 102mph @2450 8.1gph (30lph).
    This summer I fitted the Sutton CS MT prop and now as follows:- 1144lbs, 31's inc bbw, lightweight elec, u/s battery as before. 110mph 2300/24" 8.3usg/h(31lph), 102mph 2200/23"6.7usg/h (25lph), 94mph 22/22" 5.9usg/h (22lph), all these figures are low down, approx 2000'amsl or less and have been leaned, I have a fuel flow so the flow rates are fair. It'll do more if you want to burn the fuel but it feels like the airframe max on 31's is mid-late teens flat out, definately so if I refitted the 8.50's but why would I do that!! I did the prop to increase flexibility, range and comfort, I still generally cruise at the speed I did before, circa 100mph, but now have greater range, does'nt feel like I'm thrashing the engine and have a hell of a prop to drag me out of whatever crap I found to land in!! Prop is smooth as silk and slows you down great on approach. Not for everyone but for the flying I do in the UK I'd do it again. Cheers, Ed.

  15. #15

    Join Date
    May 2017
    Location
    Vancouver
    Posts
    2
    Post Thanks / Like
    Quote Originally Posted by don d View Post
    Can,t stand less than 100mph in an airplane. Aren,t those 35,s just wonderful. If you got to have em, recalibrate to kilometers/hour.
    Yup! Same here. I was actually trained on a 35. Now I'm waiting to invest in a Icon A5. Fell in love with that sucker.

  16. #16

    Join Date
    Mar 2015
    Location
    Anchorage, Alaska Carefree, AZ
    Posts
    201
    Post Thanks / Like
    Quote Originally Posted by Oliver View Post
    I recall an old thread that discussed cruise performance of cubs - speed penalties for different mods etc.
    I regularly fly with a friend with a bone stock cub, 1500+ hr 150 hp, only mods are a 82/42 borer and 29"s.
    if were both cruising at 2450 (both using digital tachs) hes got about 8 mph on me.

    Im flying a recently rebuilt cub, rigged to spec, 70 lbs lighter, 160 hp (port/polish lycon), 82/43, 3" ex gear (uncovered), bags over my hydrosorbs, 31", bby bushwheel. 2450 im about 87mph 1500 msl 70*.
    I would have figured turning a 43 pitch prop at the same rpm (and burning alot more fuel) would even things out. Guess not.

    Anyone have data on common mods and associated speed penalty?
    Whitewings Aircraft Services, Starr Farmer at Lake Hood has done some fairings for cub extended gear, I got about 7-8 MPH increase on my Husky ( has cub extended gear and AOSS) and about 4MPH on the supercub. Also did streamlined fairings on the AOSS shocks too, both added quite a bit of speed compared to uncovered. My cub is about the same as yours, same pitch prop, 1250 lbs, 2450 is near 100MPH on 31's, now has 35's.
    Well worth the added speed gain compared to uncovered gear, and looks good too.
    John
    Likes courierguy liked this post

  17. #17

    Join Date
    May 2014
    Posts
    520
    Post Thanks / Like
    Quote Originally Posted by john schwamm View Post
    Whitewings Aircraft Services, Starr Farmer at Lake Hood has done some fairings for cub extended gear, I got about 7-8 MPH increase on my Husky ( has cub extended gear and AOSS) and about 4MPH on the supercub. Also did streamlined fairings on the AOSS shocks too, both added quite a bit of speed compared to uncovered. My cub is about the same as yours, same pitch prop, 1250 lbs, 2450 is near 100MPH on 31's, now has 35's.
    Well worth the added speed gain compared to uncovered gear, and looks good too.
    John
    Berringer had a set of gear at their trade show booth this weekend, carbon fiber gear fairings looked pretty streamlined and aerodynamic.
    something similar tailored to PA 18 gear would work well.

    IMG_2460.jpg

  18. #18
    pa11driver's Avatar
    Join Date
    Mar 2010
    Posts
    104
    Post Thanks / Like
    Quote Originally Posted by john schwamm View Post
    Whitewings Aircraft Services, Starr Farmer at Lake Hood has done some fairings for cub extended gear, I got about 7-8 MPH increase on my Husky ( has cub extended gear and AOSS) and about 4MPH on the supercub. Also did streamlined fairings on the AOSS shocks too, both added quite a bit of speed compared to uncovered. My cub is about the same as yours, same pitch prop, 1250 lbs, 2450 is near 100MPH on 31's, now has 35's.
    Well worth the added speed gain compared to uncovered gear, and looks good too.
    John
    would you mind sharing a few pictures of the fairings?
    Likes pzinck liked this post

  19. #19
    Farmboy's Avatar
    Join Date
    Jan 2016
    Location
    Glens Falls, NY
    Posts
    2,001
    Post Thanks / Like
    Quote Originally Posted by Oliver View Post
    Berringer had a set of gear at their trade show booth this weekend, carbon fiber gear fairings looked pretty streamlined and aerodynamic.
    something similar tailored to PA 18 gear would work well.

    IMG_2460.jpg
    I've thought that would be pretty nice. Just shrunk wrapped mine per Douten's suggestion, but not sure if there's a diffference yet.
    But a set of CF fairings might work well.


    Sent from my imitation glass cockpit using SuperCub.Org mobile app
    Likes pzinck liked this post

  20. #20

    Join Date
    Mar 2015
    Location
    Anchorage, Alaska Carefree, AZ
    Posts
    201
    Post Thanks / Like
    Quote Originally Posted by pa11driver View Post
    would you mind sharing a few pictures of the fairings?
    Shots of fairings on Husky, essentially same as cub as the Husky has extended cub gear.
    John
    Attached Images Attached Images
    Thanks pa11driver thanked for this post
    Likes Farmboy liked this post

  21. #21

    Join Date
    May 2014
    Posts
    520
    Post Thanks / Like
    Not that familiar with Oratex, but from what I gather, looks like you could cover the gear legs in place using their process
    save a lot of downtime and simplify the task.
    anyone used Oratex before? Thoughts?

  22. #22

    Join Date
    Dec 2004
    Location
    Inkom, Idaho
    Posts
    1,250
    Post Thanks / Like
    You want to fair that aft leg of the A frame, in addition to covering it. You don't want to leave that trailing edge round.

  23. #23

    Join Date
    Mar 2015
    Location
    Anchorage, Alaska Carefree, AZ
    Posts
    201
    Post Thanks / Like
    Quote Originally Posted by courierguy View Post
    You want to fair that aft leg of the A frame, in addition to covering it. You don't want to leave that trailing edge round.
    Very correct, if no tapered trailing edge a waste of time as turbulence is still there. Ideal length from front to trailing edge is 3:1 ratio, we made the AOSS fairings slightly less as they looked odd too long, but the fairings work on gear legs and AOSS if made correctly, speed addition is pretty big for these minor mods. Where else can one get about 5% or more increase in speed this easy?
    John

  24. #24
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,271
    Post Thanks / Like
    A friend (who is a member here but doesn't post frequently) just covered the gear on his -18. He said he got 3 or 4 mi/hr gain by doing so, no aft fairing, 31 tires. Just a data point - - -
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)

  25. #25

    Join Date
    Mar 2015
    Location
    Anchorage, Alaska Carefree, AZ
    Posts
    201
    Post Thanks / Like
    Quote Originally Posted by Gordon Misch View Post
    A friend (who is a member here but doesn't post frequently) just covered the gear on his -18. He said he got 3 or 4 mi/hr gain by doing so, no aft fairing, 31 tires. Just a data point - - -
    Will be faster with the correct trailing edge for sure. Read about the testing done on round balls vs bomb shaped ones, all with same diameter frontal area, huge difference in aerodynamics and speed.
    John

  26. #26
    CamTom12's Avatar
    Join Date
    Jul 2015
    Location
    Huntsville, AL
    Posts
    575
    Post Thanks / Like
    There's a difference in a linear, blunt shaped trailing edges (covered gear, no aft fairing) vs pure round cross-sections (like bare tubes).

    Here's why: https://en.m.wikipedia.org/wiki/K%C3..._vortex_street
    Likes skywagon8a liked this post

  27. #27
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,271
    Post Thanks / Like
    And this, by Shapiro, which I never get tired of watching. https://www.youtube.com/watch?v=ftq8jTQ8ANE
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)
    Likes skywagon8a, AKCRUISER, Southern Aero liked this post

  28. #28
    Farmboy's Avatar
    Join Date
    Jan 2016
    Location
    Glens Falls, NY
    Posts
    2,001
    Post Thanks / Like
    Quote Originally Posted by Gordon Misch View Post
    And this, by Shapiro, which I never get tired of watching. https://www.youtube.com/watch?v=ftq8jTQ8ANE
    Reminds me of Post #5. lol.
    Likes Gordon Misch liked this post

  29. #29
    Farmboy's Avatar
    Join Date
    Jan 2016
    Location
    Glens Falls, NY
    Posts
    2,001
    Post Thanks / Like
    Quote Originally Posted by CamTom12 View Post
    There's a difference in a linear, blunt shaped trailing edges (covered gear, no aft fairing) vs pure round cross-sections (like bare tubes).

    Here's why: https://en.m.wikipedia.org/wiki/K%C3..._vortex_street
    Interesting. Per this page, it appears that simply adding a single fin trailing edge makes a tremendous difference. I'd be curious the real difference between a full airfoil enclosure vs adding a trailing edge fin.

    Screen Shot 2017-05-10 at 7.54.17 AM.png

    Found the answer I think - the video link shows increasing speed around the tube with the fin. As speed increases, the air starts breaking off the fin's trailing edge, as shown in the screenshots:

    Screen Shot 2017-05-10 at 7.59.08 AM.png

    Screen Shot 2017-05-10 at 7.59.18 AM.png

    Screen Shot 2017-05-10 at 7.59.37 AM.png
    Likes skywagon8a liked this post

  30. #30
    CamTom12's Avatar
    Join Date
    Jul 2015
    Location
    Huntsville, AL
    Posts
    575
    Post Thanks / Like
    I actually have an experiment in mind when I mount my GY26s that's along those lines, Farmboy.

  31. #31
    Farmboy's Avatar
    Join Date
    Jan 2016
    Location
    Glens Falls, NY
    Posts
    2,001
    Post Thanks / Like
    Quote Originally Posted by CamTom12 View Post
    I actually have an experiment in mind when I mount my GY26s that's along those lines, Farmboy.
    I hope you get good results.

    I try to envision how a tailcone cupped to mount close to the tire trailing perimeter would help reduce the drag, without being in the way, adding too much weight due to the structure needed to hold it vibration free, and I don't see enough benefit. But if a simple fin would make a difference....the 3:1 ratio may be a hurtle.

    pb

  32. #32
    Charlie Longley's Avatar
    Join Date
    Jan 2008
    Location
    Arlington, WA
    Posts
    497
    Post Thanks / Like
    I have a mostly stock PA-12 with a 150. I was flying home today a Citabria formed up with a 172 behind me and went smoking by! I thought a PA-12 was relatively fast...
    Likes pfm liked this post

  33. #33
    Farmboy's Avatar
    Join Date
    Jan 2016
    Location
    Glens Falls, NY
    Posts
    2,001
    Post Thanks / Like
    Quote Originally Posted by CamTom12 View Post
    I actually have an experiment in mind when I mount my GY26s that's along those lines, Farmboy.
    Did you ever happen to test out the single fin trailing edge on your 26's?

  34. #34
    CamTom12's Avatar
    Join Date
    Jul 2015
    Location
    Huntsville, AL
    Posts
    575
    Post Thanks / Like
    No, not yet. Been swamped at work.
    Thanks Farmboy thanked for this post

  35. #35

    Join Date
    Sep 2003
    Posts
    6,580
    Post Thanks / Like
    I have a Super Decathlon with speed mods, including very long wheel pants with added thingies on the bottom to make you think there are no wheels in there. I cannot tell the difference on or off. I am sure there is a difference, but it is not 5%.
    Likes skipster liked this post

Similar Threads

  1. PA-12 Cruise Speed with 180 hp?
    By CptKelly in forum Cafe Supercub
    Replies: 16
    Last Post: 07-13-2016, 05:13 PM
  2. Cruise prop for a PA-18-95 or PA-11-90?
    By Alex Clark in forum Cafe Supercub
    Replies: 6
    Last Post: 10-23-2005, 03:33 PM
  3. PA 18A-150 Cruise performance
    By Dupre in forum Cafe Supercub
    Replies: 11
    Last Post: 11-07-2003, 01:48 PM

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •