Page 2 of 4 FirstFirst 1234 LastLast
Results 41 to 80 of 144

Thread: Catto Vs Borer floatplane

  1. #41
    40m's Avatar
    Join Date
    Dec 2013
    Location
    Shoreham, VT
    Posts
    498
    Post Thanks / Like
    Quote Originally Posted by stewartb View Post
    This discussion is like herding cats. I'll leave y'all to it. Have a nice day.
    Some just don't like being corralled.

    From Genesis: "And God promised men that good and obedient wives would be
    found in all corners of the earth."

    Then he made the earth round... and He laughed and laughed and laughed!

  2. #42
    cubpilot2's Avatar
    Join Date
    May 2003
    Location
    Anchorage Alaska
    Posts
    810
    Post Thanks / Like
    For what it is worth:
    I was visiting with a fellow last summer at Lake Hood who was doing some flight testing with his 180+ HP cub. He does various testing for STC purposes so his cub was in a temporary "experimental" category for these tests. He was currently on floats so I was quizzing him about various changes such as props. He said that he had run a Catto prop on this cub for awhile but wound up removing it. It was not that it didn't perform good, but that he got tired of having the engine "kick back" during startup which it did not do with the big metal MaCulley prop. He said that the flywheel effect of the big Mac prevented this. He had to replace two starters do to extensive damage. The other dis-like was that when shutting down; the engine "slammed" to a halt. With the Mac and its flywheel effect shutdown was more normal.
    Ed
    Likes skywagon8a, cubnut liked this post

  3. #43
    180Marty's Avatar
    Join Date
    May 2004
    Location
    Paullina, Ia
    Posts
    2,080
    Post Thanks / Like
    From the Catto website------Catto Propellers are a fully encapsulated composite propeller protecting it from all the elements. A laminated wood core is CNC machined for precision and quality control, followed by glass/carbon fiber composite for structural integrity.
    Thanks 40m, skywagon8a thanked for this post

  4. #44
    180Marty's Avatar
    Join Date
    May 2004
    Location
    Paullina, Ia
    Posts
    2,080
    Post Thanks / Like
    The other dis-like was that when shutting down; the engine "slammed" to a halt. With the Mac and its flywheel effect shutdown was more normal.
    Time will tell if that is like a sudden stop but my 180 Cessna with MT has been shut down many times and still seems to run okay. When I shut my 150 hp PA12 down the Sensenich prop usually backs up against compression so that seems kind of abrupt too.
    Likes pzinck liked this post

  5. #45
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    11,104
    Post Thanks / Like
    Quote Originally Posted by cubpilot2 View Post
    The other dis-like was that when shutting down; the engine "slammed" to a halt. With the Mac and its flywheel effect shutdown was more normal.
    My Whirlwind hollow carbon blades on an IO-360 stops quickly also. But I would not call it "slammed" to a halt. Quick but smooth, yes. I attribute this to the electronic ignition. Mixture is pulled at idle with no O-360 shake. The lightweight blades and lack of flywheel effect is apparent.
    N1PA

  6. #46

    Join Date
    Sep 2012
    Location
    Bettles AK & Arizona
    Posts
    289
    Post Thanks / Like
    Quote Originally Posted by cubpilot2 View Post
    For what it is worth:
    I was visiting with a fellow last summer at Lake Hood who was doing some flight testing with his 180+ HP cub. He does various testing for STC purposes so his cub was in a temporary "experimental" category for these tests. He was currently on floats so I was quizzing him about various changes such as props. He said that he had run a Catto prop on this cub for awhile but wound up removing it. It was not that it didn't perform good, but that he got tired of having the engine "kick back" during startup which it did not do with the big metal MaCulley prop. He said that the flywheel effect of the big Mac prevented this. He had to replace two starters do to extensive damage. The other dis-like was that when shutting down; the engine "slammed" to a halt. With the Mac and its flywheel effect shutdown was more normal.

    I have had to change a couple of starters on Carbon Cubs because the engine kicked back at starting. The lighter of the skytech starters breaks pretty easy. Never had more than a shear pin break with metal props.

  7. #47
    PerryB's Avatar
    Join Date
    Aug 2007
    Location
    Chico, CA
    Posts
    2,030
    Post Thanks / Like
    In the case of kickback, I have to wonder how many aircraft are being inadvertently started on both mags (assuming only ONE impulse). I've seen at least a couple of Bendix type switches that should've had the right mag shunt, that didn't. I've also seen a LOT of people hop in a plane with individual switches and flip them both on prior to starting.
    Thanks Steve Pierce thanked for this post

  8. #48

    Join Date
    Sep 2012
    Location
    Bettles AK & Arizona
    Posts
    289
    Post Thanks / Like
    Quote Originally Posted by PerryB View Post
    In the case of kickback, I have to wonder how many aircraft are being inadvertently started on both mags (assuming only ONE impulse). I've seen at least a couple of Bendix type switches that should've had the right mag shunt, that didn't. I've also seen a LOT of people hop in a plane with individual switches and flip them both on prior to starting.
    all the Cessnas that I work on have impulse couplings in both bags. Since they start with a key, they are both going to fire. I can't recall seeing anything in Pipers POH that suggests you start on one mag? Only one mag has an impulse on the 0-360s I work on in Pipers, however. As for the Carbon cubs, they have electronic ignition and both plugs are hot.

  9. #49
    Eddie Foy's Avatar
    Join Date
    Dec 2014
    Location
    South Florida
    Posts
    3,710
    Post Thanks / Like
    Quote Originally Posted by Den View Post
    Since they start with a key, they are both going to fire. As for the Carbon cubs, they have electronic ignition and both plugs are hot.
    ??????
    "Put out my hand and touched the face of God!"

  10. #50
    PerryB's Avatar
    Join Date
    Aug 2007
    Location
    Chico, CA
    Posts
    2,030
    Post Thanks / Like
    The key switch (which I referred to as Bendix type) has a ground while cranking terminal specifically for shunting out a non-impulse mag while cranking, so its not just automatically firing on both while cranking. If you have impulses in both mags then you leave the ground shunt out. In the case of individual switches you should only start on the impulse, otherwise you have one side trying to fire at +25° and a kickback is likely. The impulse side fires at zero.

    I'd bet you a nickle the electronic systems have a start/retard mode, but I'm talking mags here. You kind of made my point for me. A lot of people don't know about only starting on the impulse. If the aircraft has duals all the better, but I know most Lyc's don't.
    Last edited by PerryB; 04-01-2017 at 11:58 AM.
    Likes skywagon8a liked this post

  11. #51
    Steve Pierce's Avatar
    Join Date
    Mar 2002
    Location
    Graham, TX
    Posts
    20,721
    Post Thanks / Like
    Quote Originally Posted by Den View Post
    Since they start with a key, they are both going to fire.

    There is a cut out in the key switch that cuts out the non-impulse magneto when starting.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  12. #52
    Eddie Foy's Avatar
    Join Date
    Dec 2014
    Location
    South Florida
    Posts
    3,710
    Post Thanks / Like
    Electronic ignition doesn't have static timing.

    I started my Cub on both for a year before I knew not to. It's not in the POH or the Lycoming book.
    "Put out my hand and touched the face of God!"
    Likes Todd long liked this post

  13. #53
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    11,104
    Post Thanks / Like
    Quote Originally Posted by Den View Post
    I have had to change a couple of starters on Carbon Cubs because the engine kicked back at starting. The lighter of the skytech starters breaks pretty easy. Never had more than a shear pin break with metal props.
    Quote Originally Posted by Den View Post
    As for the Carbon cubs, they have electronic ignition and both plugs are hot.
    Den,
    Is there a possibility that the electronic ignition is not retarding the spark during the starting phase? Or that the timing is set incorrectly and that the retard position is still too far advanced? Electronic ignitions should not kick back during starting.
    N1PA

  14. #54

    Join Date
    Dec 2006
    Location
    Meanwhile,...
    Posts
    5,405
    Post Thanks / Like
    Quote Originally Posted by Eddie Foy View Post
    Electronic ignition doesn't have static timing.

    I started my Cub on both for a year before I knew not to. It's not in the POH or the Lycoming book.
    Eddie that's one of those if we tell ya things... you just have to glean such knowledge by osmosis!
    Remember, These are the Good old Days!

  15. #55
    Eddie Foy's Avatar
    Join Date
    Dec 2014
    Location
    South Florida
    Posts
    3,710
    Post Thanks / Like
    Quote Originally Posted by OLDCROWE View Post
    Eddie that's one of those if we tell ya things... you just have to glean such knowledge by osmosis!
    This whole Cub journey has had a lot of osmosis.
    "Put out my hand and touched the face of God!"
    Likes WanaBNACub, DENNY liked this post

  16. #56
    hotrod180's Avatar
    Join Date
    May 2008
    Location
    Port Townsend, WA
    Posts
    3,514
    Post Thanks / Like
    Quote Originally Posted by Den View Post
    all the Cessnas that I work on have impulse couplings in both bags. Since they start with a key, they are both going to fire. ....
    Generally speaking, in my experience Lycomings have one impulse coupling (usually on the LH mag) and Continentals have two.
    Cessna Skywagon-- accept no substitute!

  17. #57

    Join Date
    Sep 2012
    Location
    Bettles AK & Arizona
    Posts
    289
    Post Thanks / Like
    Quote Originally Posted by skywagon8a View Post
    Den,
    Is there a possibility that the electronic ignition is not retarding the spark during the starting phase? Or that the timing is set incorrectly and that the retard position is still too far advanced? Electronic ignitions should not kick back during starting.

    I don't know how the electronic retards the spark for starting. There is no way to control it as far as I can tell. Just a hall-effect sensor.

    As far as the Cessnas. All the 172S that I have seen have identical mags on both sides. We have 125 of them at least; 20-25 in Mesa alone. The Seminoles have O-360 L2A and they use 4 different mags. PITA to stock 4 different mags for one airplane and all the rest use only one mag.


    If there isn't an impulse coupling on the non-retarded mag, why will it try to fire during starting? I have never seen an L2A kick back even with both mag switches turned on.
    Likes pfm liked this post

  18. #58
    PerryB's Avatar
    Join Date
    Aug 2007
    Location
    Chico, CA
    Posts
    2,030
    Post Thanks / Like
    The impulse coupler does two things. Retards the timing and produces a hotter spark at low speed
    That being said, a healthy mag will produce plenty of spark to fire an engine without an impulse. I had my left mag (the only impulse on mine) throw a fit a couple years ago. Since I have the Bendix switch with a ground shunt, I had to pull the P lead off the right mag to get it to start, which it did quite readily.
    Likes skywagon8a liked this post

  19. #59
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    11,104
    Post Thanks / Like
    Quote Originally Posted by Den View Post
    I don't know how the electronic retards the spark for starting. There is no way to control it as far as I can tell. Just a hall-effect sensor.
    My only electronic ignition experience in airplanes is with the P-mag. The P-mags are timed to top dead center. After that they automatically vary the timing as appropriate for the condition. Perhaps the system in the planes which you are working on was not timed correctly upon initial installation? One of the big advantages of electronic ignitions is to provide a more automotive like start without kickback.
    N1PA

  20. #60
    CamTom12's Avatar
    Join Date
    Jul 2015
    Location
    Huntsville, AL
    Posts
    782
    Post Thanks / Like
    Quote Originally Posted by Den View Post
    I don't know how the electronic retards the spark for starting. There is no way to control it as far as I can tell. Just a hall-effect sensor.
    There's a couple of ways to do it, sense the starter being engaged and retard timing, sense very low RPM and retard timing, etc.

  21. #61
    Smith PA12's Avatar
    Join Date
    Oct 2015
    Posts
    60
    Post Thanks / Like
    I have a Smith PA 12. Ew 1385#, 31's, Atlee3" extended, 0-360, currently running a Mac A200-8244 prop, looking to go to a Catto 8638. With the Mac I cruise at 2350rmp and 103mph. Anyone out there with same configuation that might know what I should expect with a Catto 8638 for cruise and TO?
    RCW
    Fort St John BC
    Thanks Bill.Brine thanked for this post

  22. #62
    Bill Rusk's Avatar
    Join Date
    Jan 2003
    Location
    Sandpoint, Idaho
    Posts
    5,421
    Post Thanks / Like
    I have a PA-18 (Javron Experimental) Ew 1052, 31's, 3" extended, 0-360, currently running a Cato 84-43. With the Cato I cruise at 2350rpm and right at 100mph

    Hope this helps

    Bill
    Very Blessed.
    Thanks cubamigo thanked for this post

  23. #63
    mvivion's Avatar
    Join Date
    Jun 2003
    Location
    Bozeman,MT
    Posts
    11,447
    Post Thanks / Like
    Quote Originally Posted by Den View Post
    As far as the Cessnas. All the 172S that I have seen have identical mags on both sides. We have 125 of them at least; 20-25 in Mesa alone. The Seminoles have O-360 L2A and they use 4 different mags. PITA to stock 4 different mags for one airplane and all the rest use only one mag.
    Lycoming provides accessories as spec'd by the aircraft manufacturer. Cessna apparently decided to make life simpler on these aircraft.

    Nonetheless, the long time convention on Lycoming engines was for one impulse coupling, on the left mag. If I'm hand propping any Lycoming, it's left mag only to start......if it has two impulse couplings, no big deal. Hand propping is the most critical time to have the impulse "right".

    MTV
    Last edited by mvivion; 04-17-2017 at 08:10 AM.

  24. #64
    JimParker256's Avatar
    Join Date
    Aug 2015
    Location
    Farmersville, TX
    Posts
    462
    Post Thanks / Like
    Quote Originally Posted by Smith PA12 View Post
    I have a Smith PA 12. Ew 1385#, 31's, Atlee3" extended, 0-360, currently running a Mac A200-8244 prop, looking to go to a Catto 8638. With the Mac I cruise at 2350rmp and 103mph. Anyone out there with same configuation that might know what I should expect with a Catto 8638 for cruise and TO?
    Cruise Airspeed calculation based on 100% prop efficiency (slightly optimistic):

    Prop pitch (in inches) X RPM X 60 (min per hour) / 12 (inches per foot) / 5280 (ft per mile) = Speed (in MPH)

    38" X 2350 RPM X 60 / 12 / 5280 = 84.5 mph
    38" X 2550 RPM X 60 / 12 / 5280 = 91.8 mph
    38" X 2700 RPM X 60 / 12 / 5280 = 97.3 mph

    (By the way, those same calculations indicate that your tach may be reporting a bit on the low side, since it would take 2472 RPM to get 103 mph out of a 44" prop. And that's at 100% efficiency, which is a wee bit optimistic...)

    Takeoff distances and climb rates are much more challenging to calculate, and well beyond my simple skills...
    Jim Parker
    2007 Rans S-6ES

  25. #65

    Join Date
    Jun 2008
    Location
    sioux lookout
    Posts
    546
    Post Thanks / Like
    Quote Originally Posted by Smith PA12 View Post
    I have a Smith PA 12. Ew 1385#, 31's, Atlee3" extended, 0-360, currently running a Mac A200-8244 prop, looking to go to a Catto 8638. With the Mac I cruise at 2350rmp and 103mph. Anyone out there with same configuation that might know what I should expect with a Catto 8638 for cruise and TO?
    my TCOW pa-12 on bush wheels with the catto 86/38 and 2475 rpm cruise was 95-97mph with the 86/40 same rpm 105-108 mph

  26. #66
    Smith PA12's Avatar
    Join Date
    Oct 2015
    Posts
    60
    Post Thanks / Like
    Cub12, did you see much difference in TO run. I would assume you spooled up to 2600+rpm much sooner with the 38. What is your empty weight on you 12?
    RCW
    Fort St John BC

  27. #67

    Join Date
    Jun 2008
    Location
    sioux lookout
    Posts
    546
    Post Thanks / Like
    I never ran a Mac on mine so i can't compare, the T/O run diff on wheels wasn't much between the 38 and 40, that said 95% of my flying was heavy on floats so i stuck with the 38 but i think the 40 would have been fine. my ew on wheels was mid 1200's( i can't remember exactly as i sold the plane last year) with the 38 climbing at 2600-2650 rpm at 75 mph i had a fairly steep deck angle and had to throttle back almost immediately upon starting to leval off to not over speed the engine
    Likes roxiedog13 liked this post

  28. #68

    Join Date
    Mar 2018
    Posts
    60
    Post Thanks / Like
    Quote Originally Posted by JimParker256 View Post
    Cruise Airspeed calculation based on 100% prop efficiency (slightly optimistic):

    Prop pitch (in inches) X RPM X 60 (min per hour) / 12 (inches per foot) / 5280 (ft per mile) = Speed (in MPH)

    38" X 2350 RPM X 60 / 12 / 5280 = 84.5 mph
    38" X 2550 RPM X 60 / 12 / 5280 = 91.8 mph
    38" X 2700 RPM X 60 / 12 / 5280 = 97.3 mph

    (By the way, those same calculations indicate that your tach may be reporting a bit on the low side, since it would take 2472 RPM to get 103 mph out of a 44" prop. And that's at 100% efficiency, which is a wee bit optimistic...)

    Takeoff distances and climb rates are much more challenging to calculate, and well beyond my simple skills...
    This is why I questioned if the catto pitch numbers were inches or degrees, many are reporting speeds that are beyond 100% efficiency if the numbers quoted are in inches. Apparently there are a lot of broken tachs ,
    props are not pitched like the number indicates or something is wrong with the math. I do believe the math is right other variables somehow are sneaking into the equation.
    Likes Gordon Misch liked this post

  29. #69
    Farmboy's Avatar
    Join Date
    Jan 2016
    Location
    Glens Falls, NY
    Posts
    2,628
    Post Thanks / Like
    I don’t have a dog in this race, and so this may just muddy the waters.

    The one time I was able to speak to Craig Catto directly because Nicole wasn’t in the office to stop it, I learned a few things.
    ~ Catto builds different props in the same size, and so unless you call them with the serial numbers of different props, comparing two props of the same size and pitch can mislead you. Same diameter, same pitch, different chord/blade design, but labeled the same.
    ~ Props labeled as one thing can be slightly different. I pulled a 7638 off a plane to test on mine, and inside the hub was the signature of a fellow at Catto, signing off the prop as a 7637.

    Props have a lot of black art in their designs, so I believe the only truths are directly from the guy that makes it, and/or your exact results of the specific prop mounted on your specific engine mounted in your specific airframe.


    Sent from my iPad using SuperCub.Org

  30. #70

    Join Date
    Mar 2018
    Posts
    60
    Post Thanks / Like
    Quote Originally Posted by Smith PA12 View Post
    I have a Smith PA 12. Ew 1385#, 31's, Atlee3" extended, 0-360, currently running a Mac A200-8244 prop, looking to go to a Catto 8638. With the Mac I cruise at 2350rmp and 103mph. Anyone out there with same configuation that might know what I should expect with a Catto 8638 for cruise and TO?
    The Mac with 44 inches of pitch should not be able to go faster than 98.23 , the Catto with 38 inches 84.83 . You are indicating 103 for the 44, something is not right as no prop is 100% efficient let alone 105% . If the error remains you would expect to see 98 with the Catto at the same RPM.

    Errors could come from inaccurate air speed, tachometer, pitch is not what manufacturer says.

    At the end of the day you would expect the Catto to be slower in cruise BUT get out of the hole better and climb better. I will save almost 20lb of weight and provide more efficient cooling .

  31. #71
    PerryB's Avatar
    Join Date
    Aug 2007
    Location
    Chico, CA
    Posts
    2,030
    Post Thanks / Like
    I've never run the numbers on theoretical pitch before, but it's interesting. Based on the numbers alone, my 82-42 Mac is cruising at 98% efficiency and the 82-39 Catto is defying physics. Any fairly modern fixed-pitch prop has a significant amount of twist/washout down its blade, along with a large variation in cross-sectional blade area. The theoretical pitch is an average number. I think the big difference is simply in how the mfgr. chooses to establish this number. Do they measure pitch at 50% span (diam), median blade area, or something else? I don't know. I CAN tell you that the two props mentioned above perform almost identically in rate of climb, and cruise speed vs. RPM, despite there being a 3" difference in claimed/theoretical pitch.

  32. #72
    cubdriver2's Avatar
    Join Date
    Apr 2003
    Location
    upstate NY
    Posts
    10,587
    Post Thanks / Like
    Quote Originally Posted by Farmboy View Post
    I don’t have a dog in this race, and so this may just muddy the waters.

    The one time I was able to speak to Craig Catto directly because Nicole wasn’t in the office to stop it, I learned a few things.
    ~ Catto builds different props in the same size, and so unless you call them with the serial numbers of different props, comparing two props of the same size and pitch can mislead you. Same diameter, same pitch, different chord/blade design, but labeled the same.
    ~ Props labeled as one thing can be slightly different. I pulled a 7638 off a plane to test on mine, and inside the hub was the signature of a fellow at Catto, signing off the prop as a 7637.

    Props have a lot of black art in their designs, so I believe the only truths are directly from the guy that makes it, and/or your exact results of the specific prop mounted on your specific engine mounted in your specific airframe.


    Sent from my iPad using SuperCub.Org
    Not just Catto. If you buy a Mac or Sen prop for a small Continental they all start as the same blade for each model and then are cut and manually twisted to the pitch up want. What says they are all pitched the same the full length of the blade each time?

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

  33. #73

    Join Date
    Dec 2014
    Posts
    87
    Post Thanks / Like
    Quote Originally Posted by roxiedog13 View Post
    The Mac with 44 inches of pitch should not be able to go faster than 98.23 , the Catto with 38 inches 84.83 . You are indicating 103 for the 44, something is not right as no prop is 100% efficient let alone 105% . If the error remains you would expect to see 98 with the Catto at the same RPM.

    Errors could come from inaccurate air speed, tachometer, pitch is not what manufacturer says.

    At the end of the day you would expect the Catto to be slower in cruise BUT get out of the hole better and climb better. I will save almost 20lb of weight and provide more efficient cooling .
    360 on 35's with 8638, high 80's at 2350.

  34. #74
    cruiser's Avatar
    Join Date
    May 2002
    Location
    South Glens Falls, NY
    Posts
    1,492
    Post Thanks / Like
    Quote Originally Posted by cubdriver2 View Post
    Not just Catto. If you buy a Mac or Sen prop for a small Continental they all start as the same blade for each model and then are cut and manually twisted to the pitch up want. What says they are all pitched the same the full length of the blade each time?

    Glenn
    The design spec under their TSO.

  35. #75

    Join Date
    Mar 2018
    Posts
    60
    Post Thanks / Like
    Quote Originally Posted by hunt/trapak88 View Post
    360 on 35's with 8638, high 80's at 2350.
    Max speed with a 38 pitch is 84.8MPH at 100% efficiency. If you are showing high 80's something is wrong. The pitch is more, the tach is wrong, the airspeed indicator is wrong or induced errors.

    Think of propeller pitch as cogs on a pedal bike. At a given pedal crank revolution the bike moves forward a fixed distance based on the number of cogs on the front ring and the back ring. There are two ways to make the bike go faster, speed up the pedal speed(RPM) , or change the gearing rings with different cogs , more or less ( same as increasing the pitch or decreasing) .

    For a a bike the cogs and pedal cadence produce a speed/distance that is fixed , a propellers pitch and rpm are identical . If a propellers produces a cruise higher than the advertised pitch then something in the chain( excuse the pun) is wrong. It has more pitch( like the bike more cogs) than advertised or the measuring device is wrong.

    I think part of the issue is how pitch is measured. Better designs that are more efficient can get closer to 100% but overall every one of them are not . They can be a little less but not more than 100 percent. More than 100% means simply that something is not accurate, to realistically compare propellers that needs to be figured out .
    Thanks Redwagon thanked for this post
    Likes skywagon8a liked this post

  36. #76
    cubdriver2's Avatar
    Join Date
    Apr 2003
    Location
    upstate NY
    Posts
    10,587
    Post Thanks / Like
    Quote Originally Posted by cruiser View Post
    The design spec under their TSO.
    Yup, as best they can by hand.

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

  37. #77

    Join Date
    Dec 2014
    Posts
    87
    Post Thanks / Like
    Quote Originally Posted by roxiedog13 View Post
    Max speed with a 38 pitch is 84.8MPH at 100% efficiency. If you are showing high 80's something is wrong. The pitch is more, the tach is wrong, the airspeed indicator is wrong or induced errors.

    Think of propeller pitch as cogs on a pedal bike. At a given pedal crank revolution the bike moves forward a fixed distance based on the number of cogs on the front ring and the back ring. There are two ways to make the bike go faster, speed up the pedal speed(RPM) , or change the gearing rings with different cogs , more or less ( same as increasing the pitch or decreasing) .

    For a a bike the cogs and pedal cadence produce a speed/distance that is fixed , a propellers pitch and rpm are identical . If a propellers produces a cruise higher than the advertised pitch then something in the chain( excuse the pun) is wrong. It has more pitch( like the bike more cogs) than advertised or the measuring device is wrong.

    I think part of the issue is how pitch is measured. Better designs that are more efficient can get closer to 100% but overall every one of them are not . They can be a little less but not more than 100 percent. More than 100% means simply that something is not accurate, to realistically compare propellers that needs to be figured out .

    no offense but your calculations mean nothing to me. Punching in a few constants does not mean each aircraft is the same. I think it's safe to say Multiple ppl with 8638 will attest high 80's cruise at 2350-2400 in a 'standard' cub. Your telling me my gps is wrong in a nocwind configuration? Have you even flown a catto? Is your cub the exact same as mine? I have more incidence in my wing...does hat make it faster or slower...?? How are the wings rigged?? The tach is not wrong, checked. I don't even look at my ASI. I am going off a garmin 495 gps. Maybe I should call garmin and tell them their sh*t is messed up..?? You keep punching in 'desk engineering' stuff and I'll go off real world numbers. Good day.
    Last edited by hunt/trapak88; 03-27-2018 at 10:31 AM.

  38. #78

    Join Date
    Nov 2003
    Location
    Thun Field, Washington
    Posts
    793
    Post Thanks / Like
    Delete. Shouldn't have wasted my time.
    Last edited by Carey Gray; 03-27-2018 at 12:08 PM.

  39. #79

    Join Date
    Mar 2018
    Posts
    60
    Post Thanks / Like
    Quote Originally Posted by hunt/trapak88 View Post
    no offense but your calculations mean nothing to me. Punching in a few constants does not mean each aircraft is the same. I think it's safe to say Murillo ppl with 8638 will attest high 80's cruise at 2350-2400 in a 'standard' cub. Your telling me my gps is wrong in a nocwind configuration? Have you even flown a catto? Is your cub the exact same as mine? I have more incidence in my wing...does hat make it faster or slower...?? How are the wings rigged?? The tach is not wrong, checked. I don't even look at my ASI. I am going off a garmin 495 gps. Maybe I should call garmin and tell them their sh*t is messed up..?? You keep punching in 'desk engineering' stuff and I'll go off real world numbers. Good day.
    Problem is you are taking it personally instead of getting to the root of WHY you are showing higher speed than is possible. Comparing props means all variables have to be understood. As with the bike analogy you cannot stretch gears, it is just not possible .
    If you are going 88mph with a fixed pitch prop of at 2350 your pitch is actually 40 or if pitch is actually 38 then rpm is 2450 . A more efficient prop will get closer to 100% but not be more .

    What needs to happen for members to make proper informed comparison is accurate information. It would appear that since you consider your variables "perfect" then it is obvious that the Catto propeller is actually closer to 40 pitch by design.
    Likes skywagon8a liked this post

  40. #80

    Join Date
    Dec 2014
    Posts
    87
    Post Thanks / Like
    Now my question is how do get rid of the emails when you keep responding your ridiculous engineer method?

Similar Threads

  1. Catto composite prop survey on Catto website: take it
    By slowjunk in forum Cafe Supercub
    Replies: 6
    Last Post: 05-09-2015, 02:00 PM
  2. CATTO PROPS
    By 96chevtruck in forum Experimental Cubs
    Replies: 6
    Last Post: 08-27-2009, 08:29 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
  •