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Thread: Supercub Thrust Line

  1. #41
    Jerry Burr's Avatar
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    Trim

    94 Super. You tweak (bend) the vertical stabilizer to center the ball at your preferred cruise speed. Above and below that speed it will not be centered. Jerry.

  2. #42
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  3. #43

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    Thanks. I should note that it does it at 2450 as well. Didn't mean to imply I fly around at full throttle. Has anyone put washers under the mount/engine to shim it slightly the left? "Tuning" the vertical stab sounds the easiest,

  4. #44
    Gordon Misch's Avatar
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    That negative thrust angle bugs the heck out of me to look at! Seems all backward. However, here's one possible advantage I'd be interested to hear others' thoughts on.

    What has been experienced in terms of pitch response to power changes with the engine set to an increased thrust angle? I'm thinking that if the a/c were set up with a greater thrust angle it would pitch upward more for a given power increase than it would with a lesser thrust angle.

    That would increase the stick work, and one of the nice things about cubs is their pitch balance in slow flight. So maybe one factor in the original engineering decision for thrust angle could have been to reduce the pitch response resulting from power changes, thus reducing pilot effort? In my 12, adding power in slow flight with full flaps requires a considerable increase in forward stick or trim. I would think that increasing the thrust angle would exaggerate that response?

    So I wonder if a little bit of performance enhancement might also result in a trickier-to-fly a/c? I'd be very interested to learn what flight testing has shown in this regard. Also, since I'm in the middle of a major rebuild on my 12, I'd be very interested to learn whether this will be STC'd for 12's.

    Gordon

  5. #45
    Crash's Avatar
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    Washers

    Quote Originally Posted by 94SUPER18
    Thanks. I should note that it does it at 2450 as well. Didn't mean to imply I fly around at full throttle. Has anyone put washers under the mount/engine to shim it slightly the left? "Tuning" the vertical stab sounds the easiest,
    94SUPER18: Placing thrustline adjustment shims (washers) under the left or right engine mount blocks (thrust line left or right adjustment) works to get the plane to fly straight. I know of several planes that have this adjustment. You can only "tweak" the fin so much and get results. A trim tab on the rubber stciks out like a sore thumb. This is a good alternative. Crash

  6. #46

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    wing wash?

    A lot of talk about rudder trim tabs and tweaking the vert stab and shimming the engine mount .....Rigging the plane includes setting the individual wing wash-in/wash-out ..Haven't heard much about that here. Very interesting topic......Red Jonson

  7. #47

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  8. #48
    cubdrvr's Avatar
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    You had too much fuel Digg........
    "Sometimes a Cigar is just a Cigar"

  9. #49
    StewartB
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    I think we all see other pilots perform a maneuver, or perform a short take-off, and attribute the performance to the plane. I'm as guilty as anyone. I hope Mark's mod is absolutely the best thing since sliced bread, and I hope he's successful on the business side of things, too. But, the most important mod in any plane is still a good pilot. And for the most part, you can't go out and buy that mod.

    I consider myself a skilled pilot. I have friends that are gifted pilots. There's a difference. They have natural abilities that I have to work to aquire. And still, they're better. I can buy a mod to narrow the gap. At least until they buy the same mod.

    Good luck Mark. This is exciting stuff. I hope your investment realizes a return.
    SB

  10. #50

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    That's note worthy. Kind a gives us stock cub guys a second wind. Your dad probably said to you at one time in your life "you don't need all that fangled dohickys" and then he goes and proves it. Nothen worse. How much more do tundra's weigh than 8.00 4's. Is that the 100 lbs. difference. But it does prove that weight is very relative to performance.

  11. #51
    WIflier's Avatar
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    Dig,
    Did ya try switchen Supercubs ya know the kids ain't always the best .

    Si

  12. #52

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  13. #53
    Steve Pierce's Avatar
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    Si, he wont let me fly it
    You should have been a nicer kid.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  14. #54
    R. JOHNSON's Avatar
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    The rudder trim set up that Steves Aircraft sells for the shortwings looks like a nice set up, but I don't think the STC covers a PA-18 but if you're exp. it might be the way to go.

  15. #55
    Jerry Burr's Avatar
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    Thrust Line

    Hi Geezer. I think everyone passed by your post. But I also think you missed a page. The thrustline mod simply adjusts the thrustline to zero plus or minus a tad. Just reread the info and I think you can relax. Jerry.

  16. #56

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    I have a question. If a Husky has a zero degree thrust line can I use a husky engine mount on an experimental cub project? Is the firewall bolt pattern the same?
    Mike

  17. #57
    Steve Pierce's Avatar
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    The Husky mount is for a Dynafocal mount O-360 and is a little longer. It doesn't swing like a SC. I don't believe a Husky mount will bolt up to a Super Cub.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  18. #58

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    PA18 thrustline

    So far there has not been any mention of cost for the motor mount lugs, extensions for the lower cowling, and stc paperwork. Anybody know how much?

  19. #59
    Crash's Avatar
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    Quote Originally Posted by diggler
    Im looking forward to your performance testing results. My dad flew in yesterday to visit with his stock 1975 Super Cub. Its exactly as it came from the factory with 800X4 tires except hes on his 3rd 160 hp engine and uses a 7455 prop. We had a take off/climb contest against my cub with borer prop, vgs, tundra tire etc cub . He could take off shorter, out climb me and out run me. The 75 cub is around 100 lbs lighter than mine. Only thing I could do is land shorter. Maybe I need thrust line modification so I can compete with a stock cub.
    Maybe you should ask him for some flying lessons Crash

  20. #60

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    I have flown the cub with the centerline thrust mod. I was impressed with the speed increase. I am not able to comment on the other performance features as I have not flown a cub a lot in the last few years. However I see a couple of questions about visibility. To me it was not a problem at all. The cub I was driving had big tires and extended gear.
    The question I am curious about is the cyl head and oil temp. I would guess that there would be a decrease in both because of the increased area between the bottom of the cowl and firewall, and the increased airspeed. I would like to know if anyone has done a before and after check on the temperatures. Thanks

  21. #61
    SJ's Avatar
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    Diggler,

    Do you and your dad weigh the same?

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

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  23. #63

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    How much does the cruise speed increase? Has anyone done a real test with a GPS to determine the increased speed? It would be nice if someone could fly the same cub before the mod in four cardinal directions and average the ground speed and then compare to the same test after the mod. I have heard that the take off distance is reduced 30%. I don't want to sound like a non-believer, but has anyone done any real testing to determine if this is true. I don't believe it, but I really want to.

    I am doing the mod to my airplane during the current rebuild, unfortunately I am also doing other mods like a 90" propeller and LEE so I will not know where my performance gains if any come from. I hope to be flying in a few weeks, it should be interesting.

  24. #64

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    I believe from what I have experienced it will be between 7-10 mph. I am calculating this from memory. I used gps and airspeed indications

  25. #65
    S2D's Avatar
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    Quote Originally Posted by Steve Pierce
    The Husky mount is for a Dynafocal mount O-360 and is a little longer. It doesn't swing like a SC. I don't believe a Husky mount will bolt up to a Super Cub.
    I've got a conical one off an 87 model. maybe I'll check it.

  26. #66

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    Wow! 7-10 MPH!

    That would be awsome! Now I can put the slats on with the zero thrust line mod and keep my current cruise speed.

  27. #67
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    Call Mark. If I am not mistaken they flew the plane before and after on a four point grid and came up with 7-10 miles an hour increase.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
    Thanks Beaverpilot thanked for this post

  28. #68
    AkPA/18's Avatar
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    We had the parts shipped up and were ready to install them in two AC for the Valdez show. Up until two days before the STC was issued the FAA had indicated it should be no problem for the parts to be installed at the repair station in Big Lake or by the Company--ThrustLine Products of Alaska--with an IA sign off. Now the FAA is saying these parts cannot be installed without a PMA which we are hoping to receive. This is the short version. End result is we have parts-an issued STC--and a delay to get them installed. The parts can be used for Exp. To answer the pricing question. The price will be $1800 for the STC paperwork and kit. The kit by itself will be $1750. STC and kit can be returned for a complete refund if not satisfied. We are trying as hard as we can to get this STC installed so that some numbers can be posted for you to determine if this is something you might be interested in. About the cruise increase---Actual test flight data showed 4.5 and 5 percent increase on the 160 cub and 8 percent on the 180 Penn Yan cub.

    If you have any questions please feel free to email me. If you need a reply over the phone include your info. I am to busy to take these phone calls as they come in but I have been returning calls as soon as possible. Thanks for the understanding during our start up. Sorry for the delay.

    E-mail Address(es):
    akcub@mtaonline.net

    Mark
    http://thrustline.com/

    Takeoffs are optional--Landings are mandatory

  29. #69
    S2D's Avatar
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    Quote Originally Posted by Michael Tracy
    I have a question. If a Husky has a zero degree thrust line can I use a husky engine mount on an experimental cub project? Is the firewall bolt pattern the same?
    Mike
    Bolt pattern is quite a bit wider. (about 8"). Wouldn't be worth it anyway. for the price of a husky mount, you could probably buy the STC or just modify a cub mount to give you the same results. (experimentally)

  30. #70
    S2D's Avatar
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    Quote Originally Posted by AkPA/18
    We had the parts shipped up and were ready to install them in two AC for the Valdez show. Up until two days before the STC was issued the FAA had indicated it should be no problem for the parts to be installed at the repair station in Big Lake or by the Company--ThrustLine Products of Alaska--with an IA sign off. Now the FAA is saying these parts cannot be installed without a PMA which we are hoping to receive. This is the short version. End result is we have parts-an issued STC--and a delay to get them installed.

    E-mail Address(es):
    akcub@mtaonline.net

    Mark
    Do you own one of those aircraft? If so, why can't you install them under the "owner produced parts" rule? They are your parts, your aircraft, your STC and your design. FAA-PMA is for resale of parts.

  31. #71

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    Quote Originally Posted by S2D
    Quote Originally Posted by Michael Tracy
    I have a question. If a Husky has a zero degree thrust line can I use a husky engine mount on an experimental cub project? Is the firewall bolt pattern the same?
    Mike
    Bolt pattern is quite a bit wider. (about 8"). Wouldn't be worth it anyway. for the price of a husky mount, you could probably buy the STC or just modify a cub mount to give you the same results. (experimentally)
    It was just an idea. If I choose to use a zero degree thrust line I would rather have a mount made that way to start. If there isn't one available I may make one. Thanks for the information on the husky.
    mike

  32. #72
    dave's Avatar
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    If Piper decided to sacrifice performance and flight characteristics simply to improve visibility, then I would like to modify my cub to correct the thrust-line. My preference would be a engine mount that is re-designed to accomplish the new geometry. I'm sure the lugs are of sound design etc... I just don't feel comfortable bolting spacers or lugs in that area. If an engine-mount mod becomes available I will be writing a check.

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  34. #74
    dave's Avatar
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    Very informative Dig.

  35. #75

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    Just had the mod installed on my Penn Yan conversion. The replacement parts are much sturdier than what they replaced. $1800 for STC and parts and about 3 hours for installation. The plane flies much different. I am about 6'1" and I couldn't see over the cowling when taxiing (31' Airstreaks and 3" extended gear). I don't have any good objective data yet. My quick initial impressions based on very little flight time were 100mph, feels cleaner ( things happen faster, for example when you put the nose down after a climb you get to full speed faster), More thrust at low RPM settings(including taxiing). I will try to fly it more and get some more objective data soon, for now, get out the salt shaker when you read my opinions on it!

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  37. #77

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    I have no doubt that this modification is a good one, but I also agree that a change of this nature should be acomplished by alteration of the motor mount. I believe it would be safer, sturdier, and accomplish the same thing in a better way.
    My other concern is with the price. A set of stock pa18 lugs is less than $50. ea. or less than $200. a set. I know that development, engineering, and other costs with the FAA had to be eccessive. But $1800. for the set,
    $1750. w/o STC, seems pretty high to me. If Cubcrafters or some other lower 48 state cub co. were to be offering these parts for this price, I don't think I'd be the only one mentioning this. Then again, its just my opinion. And as we all know, we all have one of those!
    Rich

  38. #78
    Jerry Burr's Avatar
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    thrustline

    Propeye. I'm glad more people don't have your opinion. Or there would be a lot less people willing to invest 110K to bring you a superior product complete with a STC. If you know of a safer, sturdier or a better way, just put up your 100k and show us how to do it. Jerry.

  39. #79
    Steve Pierce's Avatar
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    Can you imagine the testing that had to go into this to get it approved by the FAA? Manufacturing and changing the design of a part that holds the engine on. Changing the angle of the engine and proving that there are no ill effects in every flight regime. My hats off to Mark and everyone involved who obviously sacrifised there time and exuberant cost to improve the flight characteristics of the planes we all truely love. How much does Cub Crafters get for a bunch of little pieces of aluminum that glue to the leading edge of your wing? From all the Super Cubs I have seen I would bet the cost return is far greater on them than the thrustline line modification.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  40. #80
    Rookie's Avatar
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    I'm with you guys, $1800 seems fair considering the engineering and testing work involved.

    One small note however, Cub Crafters doesn't make and didn't engineer the little pieces of aluminum, these guys did:
    http://www.microaero.com

    -->Aaron

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