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Thread: J3 Speed mods ?

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    J3 Speed mods ?

    Yep. Seriously. In the quest for a new toy and after considering a champ, pretty much decided a j3 would fit the bill. If the champ has anything over the cub to me, its cruise speed. Interested in any aerodynamic improvements anyone has made to one. I know there are stc's to make it a pa-11, but if i get one, it will be a nice one and wouldn't want to hack it up so reversable mods would be of particular interest. A 10 mph gain would be significant. Pa-11 or -18 wing struts ? Wheel fairings ? Stream lined bungee covers ?
    Anyone with a cub that will outrun a champ with same engine ?

  2. #2
    cubdriver2's Avatar
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    Buy an ASI in kilometers per hour

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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    take some length off the end of each wing, more power and a cruise prop

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    I'm very much interested in clipped wings. Never been in one and looking for one to check out. Would like to see how much of a brick they are power off and what kind of landing speeds are required.hear a lot of good things otherwise.would be likely to go that route with experimental or one already done, but I wouldn't cut up a good stock j3.
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    You need a Walter turbine and a bunch of extra fuel tanks. Cheaper to keep the Cub stock and get a Mooney 201 for traveling.

    The PA11 struts don't help much. I have them, and see no difference. They add 6 lbs. i also have really super wheel pants for the Decathlon - cannot tell the difference, even at 120 kts.

    Cub on x-c - 4.1 gal/70 statute miles. Mooney on x-c - 9.5 gal/160 nm. You do the math?
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    cubdriver2's Avatar
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    Dan's J3 that I used to fly with a 85 stroker would do 90 mph at 2450, has a cruise prop 7246?

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

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    Mine will easily do that. The J4 does 100 at that power setting, and it is a stock 85.

    Any airplane is a bit faster at full power. Maybe that is his answer - cheaper than modifying the thing. Doesn’t seem to hurt the engines.

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    Making a wing shorter means more power needed. Square the wing tip off means more lift with less power = more speed for the power you have.
    DENNY
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    BC12D-4-85's Avatar
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    exposed engine cylinders = drag PA-11 cowl = less

    what's the rush with a J-3? enjoy the sights, smells, and early design from much simpler times

    Gary
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    skywagon8a's Avatar
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    J-3? & Speed?

    You need more of these.


    This is the only Aeronca that will be passed by a J-3.
    N1PA

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    I have a J-3 with the Flo-Trol “Splates” which makes for a flat wing tip that almost no-one likes. It has a C-90 and Sensenich 76” prop, cruises 85 mph - so not a lot of speed benefit. There’s another thread with a debate about the “splates”


    Sent from my iPhone using SuperCub.Org mobile app
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    Margaret Thatcher

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    mvivion's Avatar
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    J-3 and “Speed Mods” = Oxymoron.

    MTV
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    G44's Avatar
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    Get a Taylorcraft if you want more speed.
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    I have flown several Continental A-65 powered J-3s and owned a stock A-65 powered PA-11 for many years. As an "apples to apples" comparison and with the same W72CK-42 prop on both types, Piper got an extra 7-8 MPH TAS from the PA-11 at the same 2150 RPM power setting. I can't give you a breakdown for the speed attributed to the individual modifications [pressure cowling, more raked windshield, lower and downward canted thrust line, and more streamlined struts and landing gear bungee covers]. Unless you change the fuselage structure for the full conversion, you're left with the strut and bungee cover mods. They alone won't add up to 7-8 mph.

    Propellers do make a difference, though. When our airplane had the A-65 on it, a change to a W72CK-44 "cruise" prop from the "standard" 42 inch pitch added 4-5 MPH at the same RPM. There was a noticeable and negative difference in takeoff acceleration and climb performance, however. After installing the C90 on the airplane, we installed the original W76CK-40 propeller. We tested the installation of a metal 76AK-2-44 and got un unexpected full 10 MPH speed advantage at the same RPM. You do lose 14 pounds of useful load with a metal propeller. With fixed pitch props, there's always a compromise.
    Last edited by Waldo M; 05-20-2019 at 10:31 AM.
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    Quote Originally Posted by Waldo M View Post
    I have flown several Continental A-65 powered J-3s and owned a stock A-65 powered PA-11 for many years. As an "apples to apples" comparison and with the same W72CK-42 prop on both types, Piper got an extra 7-8 MPH TAS from the PA-11 at the same 2150 RPM power setting. I can't give you a breakdown for the speed attributed to the individual modifications [pressure cowling, more raked windshield, lower and downward canted thrust line, and more streamlined struts and landing gear bungee covers]. Unless you change the fuselage structure for the full conversion, you're left with the strut and bungee cover mods. They alone won't add up to 7-8 mph.
    Was thinking of asking if anyone had done this. Someone had mentioned earlier doing 90 mph with a stroker 85 in a j3. about what i would expect from a pa-11 with the same setup so it looks like theres not a huge aerodynamic advantage to the 11. Looking at the champ, i dont think its aerodynamically superior, its just ugly so the earth repels it into the air. No offense to champ drivers, i may well become one.

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    No - the ten mph advantage that Champs and PA-11s have is due to all the mods mentioned above - pressure cowl and sloped windshield are probably 3/4 of it. I bet the struts and bungee covers give 2 mph total. You could lower the angle of incidence - or buy a PA-12. They are faster. Those changes are significant.

    Yeah, with a Stroker I can easily cruise at 90, but it is wasteful. Take your 65, ram the throttle to full, and I bet she stabilizes at 90.

    If you want speed, a Champ or Taylorcraft with enclosed cowl is the inexpensive way. Or run full throttle. Probably won't hurt that bulletproof engine. Max structural is 91 or so . . .
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    I have noticed a new shape of windshield on some Champs lately. It is flatter and has a little bit more rake than the original "bubble" type windshield installed on Champs. It looks like it uses the original mounting. I'd like to hear from "before and after" Champ owners if the later windshield gives a little extra speed.

    I'm a Cub guy myself, but acknowledge that a Champ is faster, easier to get in and out of, and has much more room on the inside. It is also has a more forgiving landing gear and is hence easier to land. The main gear is placed a bit further forward on the fuselage than a Cub, so the tail is heavier to lift.

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    You are probably thinking of the Citabria windshield, which I understand is commonly used as a replacement in Champs. I put one on my 7GC, but it replaced a previous Citabria windshield so I don't know any speed difference. Big savings in price though.

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    mvivion's Avatar
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    Atlee Dodge claimedthat His STC to convert the J-3 to a PA-11 windshield (which also requires installation of wing tank and removal of nose tank) and installation of the 11 cowl would increase speed of the airplane by 7 to 10 mph. I did this conversion to a 90 hp J-3 and he was pretty close. Put a J-3 in flight attitude and check the orientation of the windshield.

    But, the OP said he’s not interested in converting to an 11.

    MTV

  20. #20
    Cub junkie's Avatar
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    The champ bubble windshields are about three times more money that the 7ECA w/s. Probably why you see more of them on champs. Unless you are going for period correct then its definitely a cheaper way to go. As far as going "fast" in any of these subject airplanes I never saw much advantage going 90 over 75. My dads fleet of 7ECA pipeline patrollers were 90 mph airplanes with no wheel pants and 800x6 tires.

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    Jerry Burr's Avatar
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    Put some closed cell foam in the bungie covers. Streamlined of course. This part will start a firestorm so I'm not going to look back after I do the post. Get up to altitude and trim slightly nose up. Then take your thumb and apply light forward pressure to the stick. Hold it for as long as you want to go a little faster. I have done it for days at a time and it worked for me. It may take practice as I have had people flying my cub who simply could not make it work. Jerry B. Thermals can upset the balance. Be patient.
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    BC12D-4-85's Avatar
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    I used to cut a piece of sponge foam water pipe insulation in half lengthwise. Under the soft covers put half in front and half in back. Refasten. Metal covers may be even better.

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    So Mike - did your PA-11 have any kind of small tank in the insrument area, or was it just wing tank to carb, via shutoff and gascolator?

    And Jerry - that seemed to get me almost 5 mph on my coast-to-coast flights, even without foam around the bungees. Been a long time ago . . .

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    Quote Originally Posted by Jerry Burr View Post
    Put some closed cell foam in the bungie covers. Streamlined of course. This part will start a firestorm so I'm not going to look back after I do the post. Get up to altitude and trim slightly nose up. Then take your thumb and apply light forward pressure to the stick. Hold it for as long as you want to go a little faster. I have done it for days at a time and it worked for me. It may take practice as I have had people flying my cub who simply could not make it work. Jerry B. Thermals can upset the balance. Be patient.
    that's interesting. Any ideas on how or why that works ? Wonder if it has anything to do with how the air is flowing through the elevator gap. Anyone ever notice a speed change for better or worse after installing a gap seal ? Then again maybe the stick push is making it go the way i used to push against the steering wheel to get my old truck up hills.

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    In all seriousness, I don't doubt it works. In smooth air, if i use a slight dive to pick up speed in my cherokee, it will maintain an extra 7-8 mph until it's disturbed. Got 0 of the 10 mph the poh claims for adding wheel pants.

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    By a Taylorcraft instead !
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    RVBottomly's Avatar
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    Quote Originally Posted by Jerry Burr View Post
    Put some closed cell foam in the bungie covers. Streamlined of course. This part will start a firestorm so I'm not going to look back after I do the post. Get up to altitude and trim slightly nose up. Then take your thumb and apply light forward pressure to the stick. Hold it for as long as you want to go a little faster. I have done it for days at a time and it worked for me. It may take practice as I have had people flying my cub who simply could not make it work. Jerry B. Thermals can upset the balance. Be patient.
    Just speculating, but it sounds like trim slightly up means stabilizer leading edge slightly down. If you push forward on the stick a little the whole stabilizer/elevator configuration looks more like an airfoil. I wonder if moving cg more aft increases the effect.

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    [QUOTE=bob turner;747783]So Mike - did your PA-11 have any kind of small tank in the insrument area, or was it just wing tank to carb, via shutoff and gascolator?

    From the start of production in April, 1947 until early in 1948, PA-11s had the wing tank to carb via shutoff and gascolator system. There were problems with fuel unporting from the single pick-up at the aft inboard bottom of the tank when in a long, nosedown glide with less than 5 gallons in the tank. This resulted in an AD that required a header tank to be plumbed into the system, installed forward of the instruments. The fuel line supplying the header comes from the bottom of the fuel level sight gauge and the line for the outflow tees into the main supply line just upstream of the on/off valve.

    Airplanes built from early 1948 had the header tank installed on the production line. All the PA-11s out there should have the header tank already installed.
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  29. #29
    mvivion's Avatar
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    Quote Originally Posted by bob turner View Post
    So Mike - did your PA-11 have any kind of small tank in the insrument area, or was it just wing tank to carb, via shutoff and gascolator?

    And Jerry - that seemed to get me almost 5 mph on my coast-to-coast flights, even without foam around the bungees. Been a long time ago . . .
    Bob,

    the fuel system was converted to a PA-11 system, with header tank.

    MTV

  30. #30
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    [QUOTE=Brandsman;747698]I have a J-3 with the Flo-Trol “Splates” which makes for a flat wing tip that almost no-one likes. It has a C-90 and Sensenich 76” prop, cruises 85 mph - so not a lot of speed benefit. There’s another thread with a debate about the “splates”

    We used to build "splates" own our banner Cubs. A DER told me they were as effective as any droop tip, an experienced Cub Ag operator told me to spend my money on horsepower. I'd go with the foam bungee mods and call it a day. Open cowl Cubs have the least cylinder maintenance problems of all.

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    My first S-7 had a J-3 type cowl, with the Subaru conversion heads and oil pan out in the breeze. I never had any cooling problems (1300 hours). My second and current S-7S has everything tucked up inside. In retrospect, the first flew a lot like a J-3, while my second flies like my T- Craft. Faster, using less fuel. Amazing how much drag that J3 type cowl had!

    Can't wait to try Jerry's crusie trim trick...
    ..

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    [UOTE=skywagon8a;747696]J-3? & Speed?
    My Father, Tony Schwamm used to give float ratings in Juneau area in the later 1930's in an Aeronca C-3. They actually flew on floats with the 2 cylinder, 36 HP engine! Gastineau Flying club trainer back in the day. I donated a C-3 engine to the Alaska Aviation Museum for display at Lake Hood.
    John Schwamm

    You need more of these.


    This is the only Aeronca that will be passed by a J-3. [/QUOTE]

  33. #33
    cubdriver2's Avatar
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    J3s came from the factory with installed speed mods, close the door and go 2mph faster. But why would anyone want to do that, or go that fast?

    Glenn
    Last edited by cubdriver2; 05-21-2019 at 09:53 AM.
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  34. #34
    skywagon8a's Avatar
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    Quote Originally Posted by john schwamm View Post
    My Father, Tony Schwamm used to give float ratings in Juneau area in the later 1930's in an Aeronca C-3. They actually flew on floats with the 2 cylinder, 36 HP engine! Gastineau Flying club trainer back in the day. I donated a C-3 engine to the Alaska Aviation Museum for display at Lake Hood.
    John Schwamm
    Is this it?



    Was this before your time John?

    pixUS003Alaska001.jpg

    There is a nice picture of your parents on page 110 of "Alaska Bush Pilots in the Float Country" with more pictures of the Savoia. Also another picture of the C-3 on page 97.

    Sorry for the segway Another Cubber. John, stirred some of my memory.
    N1PA
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    Skywagon,
    You got it all right! That was the C-3 my Dad gave float ratings in back before my time. Before he went to Alaska in the late 30's he had a flying school in LA, flew in several Howard Hughes movies, Hell's Angels, Wings, etc. in WWI biplanes.
    The Savoia Marchetti was his, quite a story. The Italians flew them from Italy to the Worlds Fair in Chicago, left two of them in NJ not flyable back to Italy. My Dad bought them and built one out of the two, shipped it from NJ through the Panama canal on a ship to LA. Flew it from LA to Alaska. Was wrecked in a taku wind when tied up in Juneau, Dad was in the hospital with pneumonia. Was to be Alaska Airways for flights around SE and Seattle, but never was to be. Dad had the Petersburg Air Service where we lived, WWII came along and he took his Waco into the war until the Navy had their own planes for coastal patrol. He was commanding officer of Navy base just north of Sitka, I was born there in the Pioneer's Home in 1943. After the war we moved to Anchorage in 1949 where Dad became the first Director of Aviation for the Territory of Alaska, built many airports all over, travelled to most of them when I was a kid with him. Then Director of Anchorage International when we became a State.
    Flying was in my blood, so always had airplanes in my life.
    Thanks very much for posting those pictures.
    John
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    John,
    your fathers WACO, was it the YKS-S, NC16512 ?
    It belongs to a friend here in Germany and
    is for sale.
    Together with my UKC we did many air shows here in Europe until I sold my UKC last year.

  37. #37

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    Quote Originally Posted by wacodriver View Post
    John,
    your fathers WACO, was it the YKS-S, NC16512 ?
    It belongs to a friend here in Germany and
    is for sale.
    Together with my UKC we did many air shows here in Europe until I sold my UKC last year.
    Wacodriver,
    Yes, that is one that he bought new, had more than one over the years, on floats in Petersburg, Alaska. I knew of it there, it was in Anchorage for years on floats at Lake Hood seaplane base, yellow and green at the time. There are pictures of it in the Alaska Wings, aviation in southeast Alaska, and Alaska Bush Pilots book. He had a Petersburg Shrimp logo with Petersburg Air Service on the side. Was a darker red/maroon back in the day originally. He took that Waco into the Navy until they got the Kingfishers to Alaska for coastal patrol.
    Thanks for the update. I should own it for nostalgia, but have too many airplanes now.
    John
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  38. #38

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    I snuck in an hour flight between rain squalls since my last post here, (sure is handy flying out of your own place) and tried the "trim up and hold forward" trick. Glass smooth air, perfect test conditions, and could see no gain in speed. BUT, I don't have a moving stab, but a large and very effective electric Ray Allen trim tab, so maybe that changes things, probably. I'll play with it some more, I tried a little up, then quite a bit up, and neither increased cruise while holding zero ROC. I was also very light, without my winter time ski flying survival gear, or my summertime camping gear, or even my e bike, just my tie downs. So, when loaded more normally I'll try it again, worth trying and it makes sense to me.

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    20190521_145427 (002).jpg
    Quote Originally Posted by john schwamm View Post
    Wacodriver,
    Yes, that is one that he bought new, had more than one over the years, on floats in Petersburg, Alaska. I knew of it there, it was in Anchorage for years on floats at Lake Hood seaplane base, yellow and green at the time. There are pictures of it in the Alaska Wings, aviation in southeast Alaska, and Alaska Bush Pilots book. He had a Petersburg Shrimp logo with Petersburg Air Service on the side. Was a darker red/maroon back in the day originally. He took that Waco into the Navy until they got the Kingfishers to Alaska for coastal patrol.
    Thanks for the update. I should own it for nostalgia, but have too many airplanes now.
    John
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    skywagon8a's Avatar
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    We had a Waco YKC on EDO 4000s here for a while. What a nice flying airplane.
    N1PA

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