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Thread: Catto Vs Borer floatplane

  1. #81
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    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.
    Not to throw gasoline on the fire, but almost all of those issues you bring up would cause the airplane to fly slower than the maximum theoretical speed of the prop. Since the only source of thrust on a single-engine airplane is the prop, there is zero possibility of the plane actually being able to "outfly the prop" unless the airplane is in a slight descent or dive. That's simple physics. But varying angles of incidence for the wing/tail, varying the CG, tachometer errors, ASI errors – all of those can impact the airspeed in flight, but NONE of them can make your plane fly faster than the prop is capable of pulling the plane through the air...

    Personally, I'm leaning towards a belief that the prop is pitched somewhat differently than the numbers would indicate. As someone else pointed out, Catto designs his props with a variable camber and angle of incidence, with the intent to maximize the efficiency at each station along the blade's radius. The numbers do mean something when comparing within the Catto prop spectrum, but may not be a valid as a direct comparison to other prop manufacturers.

    Congratulations on having a propeller that seems to be very well suited to your airplane!
    Jim Parker
    2007 Rans S-6ES

  2. #82

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    Quote Originally Posted by JimParker256 View Post
    Not to throw gasoline on the fire, but almost all of those issues you bring up would cause the airplane to fly slower than the maximum theoretical speed of the prop. Since the only source of thrust on a single-engine airplane is the prop, there is zero possibility of the plane actually being able to "outfly the prop" unless the airplane is in a slight descent or dive. That's simple physics. But varying angles of incidence for the wing/tail, varying the CG, tachometer errors, ASI errors – all of those can impact the airspeed in flight, but NONE of them can make your plane fly faster than the prop is capable of pulling the plane through the air...

    Personally, I'm leaning towards a belief that the prop is pitched somewhat differently than the numbers would indicate. As someone else pointed out, Catto designs his props with a variable camber and angle of incidence, with the intent to maximize the efficiency at each station along the blade's radius. The numbers do mean something when comparing within the Catto prop spectrum, but may not be a valid as a direct comparison to other prop manufacturers.

    Congratulations on having a propeller that seems to be very well suited to your airplane!
    That the part these guys don't get. You cannot outfly the prop . If a propeller outflys the prop, the pitch is more than advertised . Is it possible the Catto flexes a little for full power and then flattens slightly for cruise ? In this case the flexing would account for the higher pitch in cruise and thus it's a little faster . Life is not magical, if the numbers don't add up there is a reason .

    A friend with a prop shop had a 84 37 Catto on a O-320 it pulled 2200 static and under-performed compared to a Borer 82 42 so he had to reimburse his customer , has the 84 37 on the shelf . I will actually get to try this myself later this year
    I expect it will likely perform well on my engine which has a little more HP. Catto is a terrific option if you want great climb, it won't outrun a shorter higher pitched borer though, many have both and use the Borer for cruise.

    BTW, everyone is not posting speeds that indicate they outrun the prop , their cruise numbers are more consistent with the stupid math funny enough .Go figure.

  3. #83

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    Quote Originally Posted by hunt/trapak88 View Post
    Now my question is how do get rid of the emails when you keep responding your ridiculous engineer method?
    How about trying to come up with a reasonable answer rather than just saying, " that's the way it is." Come up with a flexing blade variable pitch hypothesis or other reasonable answer otherwise you are not trying to figure out the reality. The simple math is not ridiculous it is actually dead simple kindergarten level . A prop cannot go faster than the numbers otherwise something else is at play, it obviously is here , you are the one that needs to come to terms with that .

    I'm not saying your are wrong, you seem to take this personal, that was never the intention . The catto is a great prop for experimental s for many reasons, and for cubs it makes a wonderful climb prop. As good as it is however, it is not magic , other props do better in their respective areas , great there are choices .

  4. #84

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    You said 2x the numbers I posted are impossible due to your math. Are you saying I don't know how to read a gps? I'm not gonna bicker and banter. The price of tea in china means more to me. This started with me asking about how props pull. Not if my cruise speeds were correct or not. Everyone else that has a 38 catto at 86" must be wrong too. The cruise numbers on the ONLY person who posted a pull test AND cruise numbers, matched my cruise exactly when I had a 8436 on a 320 cub. Thank you to those who posted valuable info

  5. #85
    C-FIJK's Avatar
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    So with this said would a 84-36 be the best option for a stock 150 hp on a exp pa 12 ?

    Thanks

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    Quote Originally Posted by hunt/trapak88 View Post
    You said 2x the numbers I posted are impossible due to your math. Are you saying I don't know how to read a gps? I'm not gonna bicker and banter. The price of tea in china means more to me. This started with me asking about how props pull. Not if my cruise speeds were correct or not. Everyone else that has a 38 catto at 86" must be wrong too. The cruise numbers on the ONLY person who posted a pull test AND cruise numbers, matched my cruise exactly when I had a 8436 on a 320 cub. Thank you to those who posted valuable info
    The topic is Catto vs Borer Floatplane . I'm seriously considering replacing my Borer with a Catto as an option . If I'm going to spend a load of money on a new prop I would like to think I am spending my money wisely so I look at the options very carefully to ensure the value is there , I'm sure others are interested too.

    I'm sorry you are taking issue with me asking why your 38 inch prop does more than a 38" prop should. I was never saying you are falsifying the information , just trying to get to the bottom of what variables overall in the design of the Catto deviate from what we understand in terms of propeller pitch as it relates to speed and climb performance, in order to make a educated , scientific comparison, ultimately an informed decision .

    Your prop is 84" with 38" pitch as we understand the physics and the way props work then at 2350 Rpm IT ABSOLUTELY cannot go faster than 84.84MPH , in fact with slip it WILL be less. To go high 80's as you say is the case then your prop will have to be pitched 40-42 another absolute fact.

    I'm interested in learning what are the variables that are different so I can make a appropriate informed decision . Thanks to the many others that I have corresponded with , I do have a better understanding and good feel for what is going on, their approach seems to be more in line with mine and their feedback substantiated with logic , more importantly in a adult like manner .

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    I had a friend put a 84 37 on a stock O-320 he managed 2150 static went back to his 82 43 borer . For sure go with 84 36 if anything , do your homework first , you money.

    Can you actually use a Catto? Are you in the owner maintenance category ? Lastly, what are you using now?

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    This is posed as more of a question for consideration than a statement. The fixed propellers I'm familiar with have a variable pitch depending on station from the hub. The metal props may have staged pitch changes (three or ?) versus a continuous change, a visible product of the mechanical bending process after manufacture. Want a different pitch at 75% radius or the tip? Prop shops try to deliver with a bending tool.

    But they may also have variable airfoils "blended" along their length and a continuous change in pitch if made from wood or non-metal composites. Machines form the blades by milling and whatever so they can be whatever shape the designer wants.

    The question: So even if the prop is spec'd as a pitch in inches at a station (typically 75%?) there is a portion of the prop blades toward the center hub that often has a greater pitch or maybe different airfoil from what I've seen. Could that inboard portion add to airspeed over what formulas that use the 75% portion pitch say is capable of producing?

    Gary

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    Quote Originally Posted by BC12D-4-85 View Post
    This is posed as more of a question for consideration than a statement. The fixed propellers I'm familiar with have a variable pitch depending on station from the hub. The metal props may have staged pitch changes (three or ?) versus a continuous change, a visible product of the mechanical bending process after manufacture. Want a different pitch at 75% radius or the tip? Prop shops try to deliver with a bending tool.

    But they may also have variable airfoils "blended" along their length and a continuous change in pitch if made from wood or non-metal composites. Machines form the blades by milling and whatever so they can be whatever shape the designer wants.

    The question: So even if the prop is spec'd as a pitch in inches at a station (typically 75%?) there is a portion of the prop blades toward the center hub that often has a greater pitch or maybe different airfoil from what I've seen. Could that inboard portion add to airspeed over what formulas that use the 75% portion pitch say is capable of producing?

    Gary
    Attachment 36019
    The diagram above clearly shows how variable and blended most aircraft propellers are from the root to the tip. It's quite obvious that pitch can be variable, question is, how do different designs distribute and how do they determine this number for their published performance specifications .

    Well, I couldn't resist, so I called a friend in the business for 50 years, this is what he told me how the process is done with a Mccauley .

    The technician explained to me that for the Borer they actually perform a 6-7 station pitch distribution process for the Mccauley propellers. They go by a guide that is supplied by the manufacturer, the pitch given as degrees at each station . In a nut shell the Borer prop is twisted so that each station is precisely the pitch in inches it is supposed to be . Essentially the prop is a constant pitch distributed along the blade at various stations . To me this indicates the certified propellers are likely more honest in terms of true pitch , who knows what others do.

    My Borer is 45 pitch at 2400 RPM I cruise around 95MPH, theoretical speed 100% efficiency would be 102.6MPH. I'm running about 93% which is typical for most considering slip and drag. In my case if I were to report a speed higher than 103MPH then I have a greater pitch than is indicated or other variables such as inaccurate instruments or recording errors have been introduced. ALL propellers should run less than the theortical speed if the pitch indicated is accurate throughout the blade length , impossible to outrun the bade.

    This is why comparing props of equal length and pitch is not always apples to apples. One manufacturer is more honest to the pitch others probably using a blended average of their own design .

    45inches means a prop moves 45 inches in one revolution , if the number is honest that is . The only way around this is variable pitch of some kind be that hydraulic or torsional .
    Last edited by roxiedog13; 03-28-2018 at 01:20 PM.

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    BC12D-4-85's Avatar
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    roxiedog13 thanks for the reply and info. My question was posed to see if it's possible for a prop...composite Catto in this example and discussion...to exceed the theory of advance based solely upon a pitch value. Like are there other factors in design that would allow the plane to go faster than the specified station pitch theory allows? If so that may account for what's being debated. Maybe Catto or Whirlwind or ? would know? If yes then that's info. If no then maybe the pitch info is incorrect or the fixed prop's changing pitch in flight as you mention. Not a big deal but it is worth asking.

    Gary

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    PerryB's Avatar
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    Quote Originally Posted by C-FIJK View Post
    So with this said would a 84-36 be the best option for a stock 150 hp on a exp pa 12 ?

    Thanks
    Either 84 - 36 or 82 - 39. I have the 82-39 and it's perfect on a 150 hp.
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    Quote Originally Posted by PerryB View Post
    Either 84 - 36 or 82 - 39. I have the 82-39 and it's perfect on a 150 hp.
    PerryB you mind if i ask what cruise you’re seeing and what rpm also is it stock 150 and a cub? Thanks Greg

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    Quote Originally Posted by roxiedog13 View Post
    Attachment 36019
    The diagram above clearly shows how variable and blended most aircraft propellers are from the root to the tip. It's quite obvious that pitch can be variable, question is, how do different designs distribute and how do they determine this number for their published performance specifications .

    Well, I couldn't resist, so I called a friend in the business for 50 years, this is what he told me how the process is done with a Mccauley .

    The technician explained to me that for the Borer they actually perform a 6-7 station pitch distribution process for the Mccauley propellers. They go by a guide that is supplied by the manufacturer, the pitch given as degrees at each station . In a nut shell the Borer prop is twisted so that each station is precisely the pitch in inches it is supposed to be . Essentially the prop is a constant pitch distributed along the blade at various stations . To me this indicates the certified propellers are likely more honest in terms of true pitch , who knows what others do.

    My Borer is 45 pitch at 2400 RPM I cruise around 95MPH, theoretical speed 100% efficiency would be 102.6MPH. I'm running about 93% which is typical for most considering slip and drag. In my case if I were to report a speed higher than 103MPH then I have a greater pitch than is indicated or other variables such as inaccurate instruments or recording errors have been introduced. ALL propellers should run less than the theortical speed if the pitch indicated is accurate throughout the blade length , impossible to outrun the bade.

    This is why comparing props of equal length and pitch is not always apples to apples. One manufacturer is more honest to the pitch others probably using a blended average of their own design .

    45inches means a prop moves 45 inches in one revolution , if the number is honest that is . The only way around this is variable pitch of some kind be that hydraulic or torsional .
    here he goes again with his engineer talk/calculations.

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    There are many of us who truly appreciate first hand seat of the pants knowledge. And when it is more than one individual reporting, it starts to solidify our choices.

    For the sake of keeping the noise to a minimum and pirep information to a maximum I here-by vote we add a zero to the end of the numbers on all Catto props discussed in this thread, and a "-" to all numbers on the Macs .

    As such everyone will know which propellors are being discussed, and at which pitch (as each respective manufacturer presents them). Therefore no one will have to worry about weather the prop is measured in inches, degrees, at what station, or any of that. Because it will be obvious that a 820x390 could not be inches or degrees, and it really shouldn't matter. After all, these props are of complete different composition, and could be theoretically pitched identical, and still not perform the same. Who cares how they derived the number? let's just stick to the meat of which performs better in what application please.

    Take care, Rob
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    Quote Originally Posted by GCyr View Post
    PerryB you mind if i ask what cruise you’re seeing and what rpm also is it stock 150 and a cub? Thanks Greg
    I have a PA-12 with all the typical mods (-18 flaps, tail, gear+3", 31ABW & VGs) and a 150/320. The only motor mods are the FAD hotrod muffler/tailpipe and I bumped the timing a couple degrees to burn 100LL better. It's pretty light @1100 EW so its a good performer. That groundwork being laid, with the 82-39 it cruises 92-93 @ 2400-2425 and climbs 1000FPM on a cool morning @ sea level, or nearly - my home field is at a whopping 135 ft. I'm very happy with this prop. If you really wanted something to grunt off the ground the 84-36 would likely be the better prop, but I imagine whatever % improvement you see in TO would be paid back in cruise. Mine hops right off the ground so I'm really happy with the balance. In the beginning I almost went with the longer/flatter prop, but now I think I'm happier that I didn't.

    FWIW I've checked the tach twice in the last few years and it's spot-on. So's the ASI, so the numbers are solid. Maybe I don't want to know if the VSI is accurate......
    Last edited by PerryB; 03-29-2018 at 10:24 AM.
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    Quote Originally Posted by PerryB View Post
    I have a PA-12 with all the typical mods (-18 flaps, tail, gear+3", 31ABW & VGs) and a 150/320. The only motor mods are the FAD hotrod muffler/tailpipe and I bumped the timing a couple degrees to burn 100LL better. It's pretty light @1100 EW so its a good performer. That groundwork being laid, with the 82-39 it cruises 92-93 @ 2400-2425 and climbs 1100FPM on a cool morning @ sea level, or nearly - my home field is at a whopping 135 ft. I'm very happy with this prop. If you really wanted something to grunt off the ground the 84-36 would likely be the better prop, but I imagine whatever % improvement you see in TO would be paid back in cruise. Mine hops right off the ground so I'm really happy with the balance. In the beginning I almost went with the longer/flatter prop, but now I think I'm happier that I didn't.

    FWIW I've checked the tach twice in the last few years and it's spot-on. So's the ASI, so the numbers are solid. Maybe I don't want to know if the VSI is accurate......
    92 mph cruise means your effective pitch at 2450 is closer to 40. 1100 FPM climb is impressive . My Cessna 172 is 1625lb, the Borer 82 45 pulls this off the water extremely well , even with the Sportsman
    STOL, droop tips, VG's and gap seals it's not going to climb like that , have no idea what my maximum climb is actually, I do cruise at 95 though . Has no issue pulling my 200lb carcus and another two 230lb
    friends out of the hole when needed , a moose or the timber to build a new camp .

    My engine is a little stronger than yours, have the 160HP version ported polished , powerflow exhaust and P-mags . I static ( before port and polished) the Borer 2450, 2800 WOT . With the new ported
    cylinders will probably have another 10hp will have to pitch the Borer at least another two inches .

    I am going to try a Catto 84 37, will be interesting to see how it stacks up . It's likely going to be too light for my setup, I expect my C of G to be too far aft . I'll know in a couple months, cannot try before then
    unfortunately . If it pulls out of the hole better and can increase cruise, it's going to be hard to turn that down. Maybe I could add the forth buddy , just a little thinner one.

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    Don't listen to this...you prop isn't pitched what you think it is. I'm not saying it isn't, but he seems to say every catto is pitched incorrectly. I'm speaking for myself, but wasn't this about performance and comparisons? Not that your prop isn't pitched ehatbit says? You have a nose dragging 172? And a borer prop....2 completely diff things than a cub and a catto. Like I asked before have you even ran a catto? So who are you to say it isn't pitch what it says. I guess all those props are pitched wrong as that state

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    Quote Originally Posted by roxiedog13 View Post
    92 mph cruise means your effective pitch at 2450 is closer to 40. 1100 FPM climb is impressive . My Cessna 172 is 1625lb, the Borer 82 45 pulls this off the water extremely well , even with the Sportsman
    STOL, droop tips, VG's and gap seals it's not going to climb like that , have no idea what my maximum climb is actually, I do cruise at 95 though . Has no issue pulling my 200lb carcus and another two 230lb
    friends out of the hole when needed , a moose or the timber to build a new camp .

    My engine is a little stronger than yours, have the 160HP version ported polished , powerflow exhaust and P-mags . I static ( before port and polished) the Borer 2450, 2800 WOT . With the new ported
    cylinders will probably have another 10hp will have to pitch the Borer at least another two inches .

    I am going to try a Catto 84 37, will be interesting to see how it stacks up . It's likely going to be too light for my setup, I expect my C of G to be too far aft . I'll know in a couple months, cannot try before then
    unfortunately . If it pulls out of the hole better and can increase cruise, it's going to be hard to turn that down. Maybe I could add the forth buddy , just a little thinner one.
    After playing with it again this morning I went and revised my ROC to 1000. That is light and on a perfect morning. I'm still impressed.
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    Quote Originally Posted by roxiedog13 View Post
    Attachment 36019
    The diagram above clearly shows how variable and blended most aircraft propellers are from the root to the tip. It's quite obvious that pitch can be variable, question is, how do different designs distribute and how do they determine this number for their published performance specifications . Well, I couldn't resist, so I called a friend in the business for 50 years, this is what he told me how the process is done with a Mccauley . The technician explained to me that for the Borer they actually perform a 6-7 station pitch distribution process for the Mccauley propellers. They go by a guide that is supplied by the manufacturer, the pitch given as degrees at each station .....
    This is why comparing props of equal length and pitch is not always apples to apples. One manufacturer is more honest to the pitch others probably using a blended average of their own design .....
    BTW A friend of mine had a prop repitched.
    At his request, the prop shop not only repitched it as ordered but marked each measuring station along the blades, and wrote down that the pitch was at that station.

    Not quite the same thing, but if you check the C180 TCDS you'll find that it approves various props for each model 180.
    Along with the model / size prop, it also specifies the min/max pitch stops.
    I noticed one day that some of the different props have different mins/maxs specified at different stations--
    even when they're the same manufacturer and length.
    Cessna Skywagon-- accept no substitute!

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    Quote Originally Posted by PerryB View Post
    After playing with it again this morning I went and revised my ROC to 1000. That is light and on a perfect morning. I'm still impressed.
    It's gonna vary day to day though, as you well know. Some days I'll get 800 and others I'll get 1100. And I can't say what was different for sure. Sometimes I think there is a vertical component to whatever breeze might exist? 8242 prop. Perry, when I get this darn engine fixed I gotta come visit you - it would be real interesting to compare the performance of our two planes - though mine is heavier - -
    Gordon

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    Quote Originally Posted by hunt/trapak88 View Post
    Don't listen to this...you prop isn't pitched what you think it is. I'm not saying it isn't, but he seems to say every catto is pitched incorrectly. I'm speaking for myself, but wasn't this about performance and comparisons? Not that your prop isn't pitched ehatbit says? You have a nose dragging 172? And a borer prop....2 completely diff things than a cub and a catto. Like I asked before have you even ran a catto? So who are you to say it isn't pitch what it says. I guess all those props are pitched wrong as that state
    While you continue to believe a prop can outrun itself in some sort of magic , others will look to the reality of what is actually going on . it's as simple as 1+1=2 , the physics of propellers is that simple . When 1=1=2.1
    then I would like to know why.

    Give Craig a call and ask him how a 38" pitch prop can go faster than is theoretically possible . Maybe he will simply enlighten you with some simple solutions which I guarantee is not magic, nor has he beaten the laws of physics . The average pitch of the blade is going to be more than what it is stamped or the blade has a twisting component and the assigned static pitch is likely more. Just guessing , I'm not sure .


    I get that you are a catto fan boy and want to believe there is magic. If that's your solution , go for it . I tend to take a more open-minded and logical approach without the need to insult .

    "Who's to say the pitch isn't what he says? " Anyone with a grain of common sense . He could measure at one station and come up with a pitch number, which would be accurate for that section. The average of the other areas probably have more pitch that are effective for different RPM ranges. One thing is clear, the way he measures and designates is different than what others do .


    You are also ignoring the one most valuable point and that is that I am not saying a 84 38 as supplied does not go faster than its pitch designation . I am saying however that if it does, then the numbering is not honest in the way other props are pitched, or some other dynamic twisting is happening . That said, there are plenty on these threads that have reported speeds more in line, or closer to normals in which the aircraft flys at a cruise speed less than you are suggesting . Maybe they are flying a draggy 172 I suppose .


    There is a reason for variable pitch constant speed props were invented . Simply because no company has EVER been able to beat the laws of physics. If they did, every last aircraft on the planet would be using the same technology.

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    Quote Originally Posted by Gordon Misch View Post
    It's gonna vary day to day though, as you well know. Some days I'll get 800 and others I'll get 1100. And I can't say what was different for sure. Sometimes I think there is a vertical component to whatever breeze might exist? 8242 prop. Perry, when I get this darn engine fixed I gotta come visit you - it would be real interesting to compare the performance of our two planes - though mine is heavier - -
    One day flying over a Fjord I had a ROC showing over 2000fpm, engine was at idle , was in a Taylorcraft . This was not thermal, it was more mechanical , this particular Fjord well know for these events . You can bet there is a vertical component some days. I used to hang glide a number of years. Many evenings the winds would come off the ocean and up the slopes, the breeze nearly imperceptible . I've climbed 2000 feet many evenings with this "magic" lift as it was nicknamed , made for a fun sleigh ride for 45 minutes .

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    Quote Originally Posted by Gordon Misch View Post
    It's gonna vary day to day though, as you well know. Some days I'll get 800 and others I'll get 1100. And I can't say what was different for sure. Sometimes I think there is a vertical component to whatever breeze might exist? 8242 prop. Perry, when I get this darn engine fixed I gotta come visit you - it would be real interesting to compare the performance of our two planes - though mine is heavier - -
    I'd like to do that. I've been following your engine thread because I'm wanting to make mine a 160 at overhaul, along with a little porting. From what I understand, Lycon motors with 8.5 and porting generally crank out about 170hp @ 2700. I want one! My engine is so old (how old is it?), it's so old it doesn't even have a dash number. Straight up O-320, period. I have 1850 hr since major and has excellent leakdown numbers and minimal oil use so knock on wood, but I'm getting myself mentally prepared. Kind of like a beloved dog that's getting old, you know the day is coming.
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    Quote Originally Posted by PerryB View Post
    I'd like to do that. I've been following your engine thread because I'm wanting to make mine a 160 at overhaul, along with a little porting. From what I understand, Lycon motors with 8.5 and porting generally crank out about 170hp @ 2700. I want one! My engine is so old (how old is it?), it's so old it doesn't even have a dash number. Straight up O-320, period. I have 1850 hr since major and has excellent leakdown numbers and minimal oil use so knock on wood, but I'm getting myself mentally prepared. Kind of like a beloved dog that's getting old, you know the day is coming.
    You'll want to ask plenty of questions, I'd start with Lycon. The older engines have a narrow deck case, the cylinders are different as I understand. The rest I have no idea , there are differences with crank bearings and so on, needs to be considered before you commit . 170HP might be doable , considering your tired 150HP is probably only making 140hp with standard muffler, it would be quite the jump in power to weigh ratio without any penalities . Wouldn't hurt to consider the O-360 , depending on the O-320 rebuild cost it might be a viable option . The little extra weight offset with the Catto 86" prop , would make a great combination. Fuel economy usually about the same if distance ,speed and fuel burn considered , the option also exists to run lower RPM for better economy .

  25. #105
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    Sorry, but I just don't have any interest in a 360. I've bought a lot of expensive parts to keep it light and keep the CG aft.
    Last edited by PerryB; 03-30-2018 at 11:56 AM.

  26. #106

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    Quote Originally Posted by roxiedog13 View Post
    While you continue to believe a prop can outrun itself in some sort of magic , others will look to the reality of what is actually going on . it's as simple as 1+1=2 , the physics of propellers is that simple . When 1=1=2.1
    then I would like to know why.

    Give Craig a call and ask him how a 38" pitch prop can go faster than is theoretically possible . Maybe he will simply enlighten you with some simple solutions which I guarantee is not magic, nor has he beaten the laws of physics . The average pitch of the blade is going to be more than what it is stamped or the blade has a twisting component and the assigned static pitch is likely more. Just guessing , I'm not sure .


    I get that you are a catto fan boy and want to believe there is magic. If that's your solution , go for it . I tend to take a more open-minded and logical approach without the need to insult .

    "Who's to say the pitch isn't what he says? " Anyone with a grain of common sense . He could measure at one station and come up with a pitch number, which would be accurate for that section. The average of the other areas probably have more pitch that are effective for different RPM ranges. One thing is clear, the way he measures and designates is different than what others do .


    You are also ignoring the one most valuable point and that is that I am not saying a 84 38 as supplied does not go faster than its pitch designation . I am saying however that if it does, then the numbering is not honest in the way other props are pitched, or some other dynamic twisting is happening . That said, there are plenty on these threads that have reported speeds more in line, or closer to normals in which the aircraft flys at a cruise speed less than you are suggesting . Maybe they are flying a draggy 172 I suppose .


    There is a reason for variable pitch constant speed props were invented . Simply because no company has EVER been able to beat the laws of physics. If they did, every last aircraft on the planet would be using the same technology.

    Your properly worded phrases and lack of everything in a department that you don't even have the same type of aircraft as everyone else discussing the topic has turned comical. These numbers and constants you punch into your Texas Instruments calculator...what are they? What do they mean? Are there variables? Where did they come? Do you even know? Obviously not, you had to call Macauley.... Are they only good for a metal prop, that flexes differently as it turning? And back to the diff airplanes...? You don't even have the same aircraft as the other asking and your throwing out opinions and 'theorys'. So....you've never flown the prop being discussed, you don't have the same aircraft make, I mean dude you got a 172...we are talking cub like aircrafts. All you got is a few numbers you punch in and then tell people theirnpeops are not pitched what they say they are....?? Cubs here...Cubs...not 172's.....will all attest that a 8436 on 320 will cruise mid-high 80's at 2400-/450. At 8638 on a 360 in a CUB type airplane will cruise high 80's low 90's at 2350-2400. Fact. But like I stated earlier, all those thousands of props are pitched incorrectly. You didn't even know if they were pitch in degrees or inches....I'm done now and will leave the bs to you and the like
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  27. #107
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    Show me a screw, which when threaded into a matching nut, will go farther than its threads take it. Roxidog is merely saying that doesn't happen.
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  28. #108
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    Perry, I think when overhaul time comes around, upgrade cost wouldn't be much of an issue. The cost to upgrade if you already have a wide deck engine is basically cylinders and STCs. If you have a low-compression narrow deck case, then perhaps an exchange engine would make sense. Right now, for me, it looks like about a $6.5k cost increment to upgrade. About 5k+ of that is cylinders.
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  29. #109

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    Sure, a 1/4'-20 bolt and a 1/2"-20 bolt both have 20 threads per inch and would move the same distance per revolution, but props are not bolts. If a 41" and an 82" pitch prop were pitched at the same angle, the 82" is going to pull quite a bit more air than the 41" prop. A Catto may be pitched at the same angle as a Borer, but having a different blade and wider cord, it'll pull more air. I think roxiedog's math is correct, but it doesn't matter. Props are not mechanical. I'm not sure that Catto props being a little steeper than labeled means Craig Catto is being dishonest, which is sort of being implied. I could bitch about my 84/37 Catto and my 82/42 Borer turning pretty close to the same RPM. I've chosen to get over it. With all due respect, I'd suggest that roxiedog do the same. Life is a lot less comfortable when your underwear is knotted up.
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  30. #110
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    As Will Rogers allegedly said: "There are three kinds of men: Those who learn by reading; those who learn by observation; and those who have to pee on the electric fence for themselves."

    Personally, I like to learn the theory, terminology, and the physics behind how things work, so I guess that's a combination of "reading" and "observation" for me. That way, when an observation appears anomalous, I can recognize it, and eliminate certain theories as to why that anomaly is occurring. Makes my troubleshooting and issue resolution MUCH simpler if I don't have to waste time pursuing possibilities that absolutely cannot exist in the natural world.

    But I absolutely support anyone's freedom to choose that third category as their primary learning mode...

    To that end, I'm bowing out.

    Have a great day!
    Jim Parker
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  31. #111

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    I probably will be going back to my borer prop when I go back to floats, it really changed my weight and balance when carrying a heavy load.
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  32. #112
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    being dishonest, which is sort of being implied.
    I didn't take it that way, but that's just me. I took "honest" to mean "objectively correct". I didn't interpret it as bashing in any way, though I agree that it could be seen that way. But like I said, that's just me-----
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    Quote Originally Posted by Carey Gray View Post
    Sure, a 1/4'-20 bolt and a 1/2"-20 bolt both have 20 threads per inch and would move the same distance per revolution, but props are not bolts. If a 41" and an 82" pitch prop were pitched at the same angle, the 82" is going to pull quite a bit more air than the 41" prop. A Catto may be pitched at the same angle as a Borer, but having a different blade and wider cord, it'll pull more air. I think roxiedog's math is correct, but it doesn't matter. Props are not mechanical. I'm not sure that Catto props being a little steeper than labeled means Craig Catto is being dishonest, which is sort of being implied. I could bitch about my 84/37 Catto and my 82/42 Borer turning pretty close to the same RPM. I've chosen to get over it. With all due respect, I'd suggest that roxiedog do the same. Life is a lot less comfortable when your underwear is knotted up.
    How is it that I have a issue, are you kidding me ? I'm the one simply asking questions and making adult suggestions, others are insulting and attacking. I wonder why ? I'm merely trying to compare these propellers , as the thread title reads . In order to compare properly it is necessary to get as close to a apples to apples comparison as possible . When I realized someone is saying their prop out-flies the pitch, a red flag goes up immediately . Why, because it is impossible . One prop may be more efficient than the next, at the same pitch , neither can go faster.

    I tried to get to the bottom of this disparity , instead of adult conversation and a rational approach I get personal attacks and insults . Obviously, getting nowhere with this sixth grade schoolyard debate I decided to call Catto myself . The reality is that they measure pitch at the outboard part of the propeller, 75% of the way out , the inboard portion has a greater pitch different than what is stamped on the propeller . You have to add 3"-4" of pitch to their numbers to get the equivalent number on a propeller that does it the old fashioned way .

    Now that I know the truth, myself, and others that want to do a fair and honest comparison can now do just that . For example to compare to my Borer 82 45 Catto suggested the 82 42 for takeoff and cruise. If I want more climb I go to a longer prop reduce the pitch , you loose the speed. Simple physics.

    No magic just logic and common sense . I was correct from the beginning . A 38" pitch prop at 2350 will not go 90MPH, the 3"-4" that you have to add will get you there though, the prop is really 41-42" pitch effectively . What you get stamped on the Borer is the pitch in inches as it is stamped "honestly."

    Entertaining watching those trying to defend the "magic" though . I'm not a fanboy , Instead I take a open minded logical approach in discussion.

    BTW your 84/37 is more or less a 42 pitch , just like the Borer you mention.
    Last edited by roxiedog13; 04-04-2018 at 03:10 PM.
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  34. #114
    BC12D-4-85's Avatar
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    I suggested this was possible in Post #88 re inner pitch and perhaps change in airfoil (or both). Good it's been explored and maybe explained. Whatever works and apparently they work well.

    Gary
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    Quote Originally Posted by BC12D-4-85 View Post
    I suggested this was possible in Post #88 re inner pitch and perhaps change in airfoil (or both). Good it's been explored and maybe explained. Whatever works and apparently they work well.

    Gary
    They seem to make a great product no doubt , there are many out there for experimental that do work well for the intended purpose . The longer flatter prop combination for slower aircraft like the cub on tundra and floats does an incredible job. Nice to have the option where the certified props do not fill this gap , especially at a lower price point . I've also tried warp drive and aeromatic , both worked very well for the intended purpose .


    I considered the 84 38 myself even knowing now that it is really closer to a 42 pitch it will still not do what I expect . Their 82-45( closer to 48") will be on the table however as an option .
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  36. #116

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    I've decided against getting into a battle of wits with an unarmed man.

  37. #117
    Gordon Misch's Avatar
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    Quote Originally Posted by Carey Gray View Post
    I've decided against getting into a battle of wits with an unarmed man.
    Huh? C'mon Carey, the guy's just trying to reconcile the numbers. See ya at Curtis and Cougar Mtn fly-ins - - -
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  38. #118

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    Gordon, Has anyone looked at a prop and how the angle changes at different stations?
    "I refuse to get in a battle of wits with an unarmed man" Danny Partridge, The Partridge Family, a long time ago.
    I've been waiting to use that line for years. Now, you want to take that away from me. I may never forgive you, but I might.
    Whatever happens online, to me, is not to be taken too seriously.
    Don't want to risk getting my shorts in a knot.
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  39. #119
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    Haha! Somewhere I read of a political argument being a battle wits between unarmed combatants. Love the line but never remember to use it when the time could be right!!

    The angle HAS to change at different stations, including for a uniform "true" pitch because the distance those stations travel circumferentially increases farther out on the blade. So the angle is going to be something like the arcsin of the pitch divided by the circumference at a particular station. Something like that, it's late for this geezer - - -
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  40. #120
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    Here's my take on this can - can't from a geometric pitch screw vs realized airspeed discussion. As airspeed increases the portion of the fixed pitch propeller that's efficient and provides thrust moves inward towards the hub. A flat prop's tip pitch, if known and used to calculate cruise airspeed via math, would say that speed can't happen. At the typical 75% station it maybe can't happen either depending on prop design. But inboard of that....if the pitch and airfoil allow...some thrust can be available in cruise to create speed.

    Thrust changes with the prop design and airspeed. Some props have a broader range of efficiency and thrust vs airspeed than others. Isn't that what's been observed here?

    Catto mentioned the "effective" pitch is greater than they provide. That supports what I suggest.

    Gary

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