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Thread: Pa-18 w/150hp prop choice?

  1. #1

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    Pa-18 w/150hp prop choice?

    Iíve got my first plane. Pa-18a with a 150 in it. Currently running a 80/44. Id like to go to something with a bit more off the ground performance. At 5k each it doesnít seem like a guy can test fly many props. Could someone explain to me their thoughts of the optimum pitch/length.
    so far Iíve got recommendations for 82/43 and 82/41. From guys that fly the same as I would. Heavy most the time, nothing real high altitude, short strips, hops of a 100miles would be my long hauls. Some say the 150 wonít sping the 43 like it should be. Others say the 43 will save you in a bad situation when you need power now. Then guys say the 41 is the best for short field work just loose five mph or so.
    thoughts?
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  2. #2
    skywagon8a's Avatar
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    Your current prop should be the approximate equivalent of an 82/42. If you wish more off the ground performance, you could have your current prop pitched to 43. I doubt you will see much difference between any of those three props. Save your $5k.
    N1PA

  3. #3

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    Tie the tail down and get a static RPM so you have a baseline to start with. With an 82 inch prop in general every inch change in the prop will cost you 2.5 - 3 mph at 2400 rpm depending on the plane. Static RPM change is around 35 rpm per inch if I remember correctly. Depends on what you call short strip, but if you can't get in the air then loosing 7 mph won't matter. For a new cub driver short and heavy with a 150hp I would recommend a 82/41 and good music for the ride home. Check you engine bushings you may get a few mph back if they are old and sag. On a side note prop is only one small part of takeoff performance. Don't look at you tube Knik and Valdez videos and think that is how your cub should perform.
    DENNY
    edit: Damm I missed that 80 inch part, not enough coffee yet. I would agree with the above post.
    Last edited by DENNY; 01-01-2021 at 01:15 PM.
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    Great pic for a first plane and welcome to the upgrade game lol.

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    Lol knik dick as I have heard it referenced.
    I will see about getting static checked before I spend any money on something new. Repitch sounds like a good idea too.
    short and heavy. 500’ strips is what the majority of what I use. For my hours and experience I’m staying away from under that for now.
    hypotheticly let’s say I go 80/43. How would that compare to the 82/41 for overall performance? I’m a big fan of getting it in the air. Speed once I’m there isn’t a huge deal. Came home at 125ground speed one day and came home at 45 ground speed one day so who knows on any given day up here anyway.
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  6. #6

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    Quote Originally Posted by farm_boy252 View Post
    Great pic for a first plane and welcome to the upgrade game lol.
    Lol thanks. Upgrade game for me right now is getting this plane to perform the best it can with what it has. Gonna have it measured
    to see if a thrustline would be helpful. Checking into a prop change. Gonna check my brakes and maybe upgrade tho use. But otherwise it flies great and has done all I’ve asked it to in my measly 170hrs.
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  7. #7
    55-PA18A's Avatar
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    What make and model prop? Be sure you're comparing apples to apples. Also, if your considering a different pitch prop, make sure the one you have is actually the pitch marked on the prop. Isn't always necessarily so.

    Jim
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    Quote Originally Posted by exhaust View Post
    Lol thanks. Upgrade game for me right now is getting this plane to perform the best it can with what it has. Gonna have it measured
    to see if a thrustline would be helpful. Checking into a prop change. Gonna check my brakes and maybe upgrade tho use. But otherwise it flies great and has done all I’ve asked it to in my measly 170hrs.
    I have no where near the experience of a lot of people on this site...the best performance mods for me so far have been the prop (from sensenich cruise prop to the borer 82/42) and VG's. I also had the break booster kit finally put on last annual and pretty happy with that as well. I did not want that so I could land somewhere short where you needed to hammer on the breaks to stop...just wanted better turning on the ground and to actually have breaks that would hold during a run up.

  9. #9
    hotrod180's Avatar
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    Experimental cub or factory?
    Standard prop is a 74" diameter, McCauley "borer" is 82".
    What model 80" prop is on there, & is it approved / STC'd ?
    Cessna Skywagon-- accept no substitute!

  10. #10

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    It’s a legal cub. Not sure on model of prop on it. McCauley 80/44 is all I know. I believe it is approved.
    Im gonna look into those brake boosters. My brakes were bad. I could stand on them and not get the tail to come up on landing let alone on run up. We bleed them and filled them and it was much better. My understanding now is those brakes need to be full all the time to work properly.
    vg’s came on the plane.
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  11. #11
    mvivion's Avatar
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    Quote Originally Posted by exhaust View Post
    It’s a legal cub. Not sure on model of prop on it. McCauley 80/44 is all I know. I believe it is approved.
    Im gonna look into those brake boosters. My brakes were bad. I could stand on them and not get the tail to come up on landing let alone on run up. We bleed them and filled them and it was much better. My understanding now is those brakes need to be full all the time to work properly.
    vg’s came on the plane.

    Your 80 inch prop may in fact be a cut down Borer prop. If so, it would be legal, at minimum length, I believe.

    If you're thinking brake boosters, definitely go with Steve's brake boosters: https://www.stevesaircraft.com/vbrake.php

    Steve's boosters are vented, and are as good as it gets....

    MTV

  12. #12
    skywagon8a's Avatar
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    This prop question comes up again and again.
    A "Borer" prop is a McCauley 1A175GM8241 The 82 is the diameter and the 41 is the pitch.
    I have a "seaplane" prop for a 7GCB. It is a McCauley 1A175GM8046. The exact same prop as the "Borer" except the factory shipped it 2" shorter.
    N1PA

  13. #13
    mvivion's Avatar
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    Quote Originally Posted by skywagon8a View Post
    This prop question comes up again and again.
    A "Borer" prop is a McCauley 1A175GM8241 The 82 is the diameter and the 41 is the pitch.
    I have a "seaplane" prop for a 7GCB. It is a McCauley 1A175GM8046. The exact same prop as the "Borer" except the factory shipped it 2" shorter.
    When I bought my Super Cub, it had an 80 inch McCauley prop, which we assumed was sold that length. At some point, I pulled the spinner for some reason, and discovered that it had, in fact, been a "Borer" 82 inch prop, and been cut down to 80 inches.
    Coincidentally, it also had a lightly stamped bit of information on the hub: "Propeller not airworthy".

    I'd been flying it for a while. Never did find out who stamped that hub or why, but I bought a new 82 inch McCauley the day after I discovered that "message".

    The 82 pulled quite a bit harder than the 80.

    Also, since it hasn't been mentioned here yet, it is possible to re-pitch these propellers, if the initial pitch doesn't suit you. So, you could start with a 43 pitch, and if you didn't like it, have the prop re-pitched to 41 or ?? That's assuming you have reasonable access to a prop shop, of course.

    With a 150 and an 82 inch McCauley, I'd probably start with a 42 pitch. That's what worked best on my 150 Cub.

    MTV
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    MTV thanks for that. My tips are not square. The are rounded tips so I’m thinking it has been cut down at some point. I can’t find a prop log in my paperwork.
    82/42 is kinda where I’m leaning right now. Will check out steves brake booster then. I don’t usually use my cub for 1000’ runway stuff so brakes are a good thing.

  15. #15
    PerryB's Avatar
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    I second the 82-42.

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    Steve Pierce's Avatar
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    Look at the STC for installing the McCauley prop on your airplane. It will list the minimum length. Being shorter than 82" is going to compromise your climb.
    Steve Pierce

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    Will Rogers
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  17. #17
    WWhunter's Avatar
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    Congrats on getting an 'A' model! My favorite!
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  18. #18

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    Quote Originally Posted by WWhunter View Post
    Congrats on getting an 'A' model! My favorite!
    Mine never sprayed. Came straight to alaska in ‘61. Still have the hopper frame work in the roof. Click image for larger version. 

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  19. #19

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    Quote Originally Posted by Steve Pierce View Post
    Look at the STC for installing the McCauley prop on your airplane. It will list the minimum length. Being shorter than 82" is going to compromise your climb.
    I was wondering if I’m missing out with a 80”. Annual is coming up in March or so, once I see how much that runs me I’ll use my left over budget for a prop and brake boosters.
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  20. #20
    mvivion's Avatar
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    I think that if your tips are rounded, and the prop is 80 inches, you definitely will see an increase in performance by going to an 82 inch prop.

    MTV

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    I like the sound of that. Here’s my tips. Of the prop. Click image for larger version. 

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  22. #22
    skywagon8a's Avatar
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    Quote Originally Posted by exhaust View Post
    I was wondering if I’m missing out with a 80”. Annual is coming up in March or so, once I see how much that runs me I’ll use my left over budget for a prop and brake boosters.
    Quote Originally Posted by mvivion View Post
    I think that if your tips are rounded, and the prop is 80 inches, you definitely will see an increase in performance by going to an 82 inch prop.

    MTV
    I did a test which has been reported here previously between an 80" and an 82" version of the 1A175GMxxxx prop of three different pitches on a 150 hp Cub and a 150 hp 7GCB, both on floats. Same props on both planes. All were new props. There was very little difference on take off times or rate of climb. The only performance differences were in the pitch, where there were different cruise speeds. The only difference noted in the diameters was the noise perception. Prior to running these tests both airplanes had the stock 7456 Sensenich prop.

    This does not take into consideration how many times your 80" prop may have been reworked. It could be that your 80" prop is just worn beyond the efficiency of a new one.
    N1PA
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    So with that information what I get is other than cruise speed you found no/minimal performance differences between props?
    then other guys are saying noticeable differences. Would this possibly be due to being on floats?

  24. #24
    skywagon8a's Avatar
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    Quote Originally Posted by exhaust View Post
    So with that information what I get is other than cruise speed you found no/minimal performance differences between props?
    then other guys are saying noticeable differences. Would this possibly be due to being on floats?
    It could be related to being on floats, however the only difference would be the weight and drag differences. And with those props I found the cruise speeds to be the same on wheels as on floats. The 82" prop was left on the Cub and the 80" was left on the 7GCB. The 82" just "felt" as though there was something thrashing around doing nothing. That feeling disappeared with the 80". Nothing measurable, only a feeling.
    N1PA

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    BC12D-4-85's Avatar
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    These long thin props get reworked as wear occurs. Eventually they reach minimum standards for size and shape - length, width, thickness, and airfoil. Not saying yours is worn out but they can get like that over time as metal is removed. You could have it looked at to confirm its condition. Also static rpm is a starting point but even a stock 74-50/52 prop will turn up rpms but won't out pull a Borer at the same rpm. I found an 80" prop to be less prone to tip wear than an 82. My experience with them.

    Gary

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    mvivion's Avatar
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    Oh, and if you ever have a prop repitched.....don’t watch that process.

    MTV
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    The prop deal is kind of black magic. It makes my hair hurt if I give it too much thought. Iíve seen guys with sorry props get in and out of places they shouldnít and guys with good props make a Citabria seem short. Get the best prop you can afford somewhere in the ballpark of the pitch you want then try and wear it out. I do know for sure that every LB you pull out of a cub makes that prop mysteriously pull harder
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  28. #28
    Steve Pierce's Avatar
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    Quote Originally Posted by mvivion View Post
    Oh, and if you ever have a prop repitched.....don’t watch that process.

    MTV
    Took my 8243 in and had it repitched. Told my long time prop guy not to laugh. He did, my leading edges are hammered. Repitched to 41.
    Click image for larger version. 

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    Steve Pierce

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    Will Rogers

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    BC12D-4-85's Avatar
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    See this...see this with A&P attached...see them smile and file away your prop. Then ask why it no longer performs like new. Secret: Keep from dinging up your prop with rocks, ice, and water.

    Gary
    Attached Images Attached Images  
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  30. #30
    Steve Pierce's Avatar
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    Quote Originally Posted by BC12D-4-85 View Post
    See this...see this with A&P attached...see them smile and file away your prop. Then ask why it no longer performs like new. Secret: Keep from dinging up your prop with rocks, ice, and water.

    Gary
    Easier said than done.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  31. #31

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    The only reason I'd buy a new borer, is so you can have a shelf prop flown out when you bend the new one. I agree with Skywagon that much of the performance between the three borer pitches and even a chopped 80" (which I currently use on an A model) is psychological. Given conditions at any mountain/valley strip are different every 5 minutes. So many more factors than prop performance. They will all pull a properly loaded cub (for the conditions, whether over gross or way under) off your 400-500' hunting strips all day. The problem is we convince ourselves we have to be able to land (and takeoff) from every strip at all times, and believe the prop has a lot to do with that---wrong. Give respect where its due. Easier said than done.

    I'd buy a really nice used borer and use whichever for everyday, having a spare. Take the rest of your money to the bank and be ready to pay out for the minor mistakes here and there that are $5k a pop. Destroyed tailwheels, broken cabane V fittings, bent prop, overflow swallows your ski plane, on & on.

    As for brakes, save your money some more. Bleed them, especially if you're going into a strip you know you want brakes. The originals due a fine job if maintained. If you're just dinking around in the flats you can maintain them less and still land in 200' with no brakes.

    Buy AVGAS, build time, make smart decisions. These old cubs with the majority of AK mods do a fine job for normal working class hunters/adventurers. If money is no factor, disregard!!
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  32. #32
    mvivion's Avatar
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    Quote Originally Posted by C_Bailey View Post
    The only reason I'd buy a new borer, is so you can have a shelf prop flown out when you bend the new one. I agree with Skywagon that much of the performance between the three borer pitches and even a chopped 80" (which I currently use on an A model) is psychological. Given conditions at any mountain/valley strip are different every 5 minutes. So many more factors than prop performance. They will all pull a properly loaded cub (for the conditions, whether over gross or way under) off your 400-500' hunting strips all day. The problem is we convince ourselves we have to be able to land (and takeoff) from every strip at all times, and believe the prop has a lot to do with that---wrong. Give respect where its due. Easier said than done.

    I'd buy a really nice used borer and use whichever for everyday, having a spare. Take the rest of your money to the bank and be ready to pay out for the minor mistakes here and there that are $5k a pop. Destroyed tailwheels, broken cabane V fittings, bent prop, overflow swallows your ski plane, on & on.

    As for brakes, save your money some more. Bleed them, especially if you're going into a strip you know you want brakes. The originals due a fine job if maintained. If you're just dinking around in the flats you can maintain them less and still land in 200' with no brakes.

    Buy AVGAS, build time, make smart decisions. These old cubs with the majority of AK mods do a fine job for normal working class hunters/adventurers. If money is no factor, disregard!!
    Well, now we all know that if we spend $5000 on a piece of airplane equipment, that airplane WILL perform much better......

    Otherwise, good advice.

    MTV
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  33. #33

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    Bailey thanks for that. I see a lot of truth in your post. My current prop hasn’t let me down yet and has hauled every load I’ve thrown at it and we’ve gotten airborne everytime. Just being a new pilot and having never flown different props I wouldn’t know if they make a difference or much of one.
    my cub does pretty good. I’ve never landed shorter than 350’ in a normal situation. My legs may be to short to reach the brakes very good. My stick hits the seat already. But I’ll bleed them when I put my wheels back on and see what that does for them. They won’t hold the plane past about 1800rpms on a run up before.

  34. #34

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    Non boosted Cleveland brakes stink on anything over 8.50s. I might even include 8.50s as too big to run without boosters. To me it’s a safety issue if you are landing anything off airport or confined. Heck, I want vented, boosted brakes if taxing very far in a stiff xwind. Brake fade sucks

  35. #35

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    Quote Originally Posted by KevinJ View Post
    Non boosted Cleveland brakes stink on anything over 8.50s. I might even include 8.50s as too big to run without boosters. To me it’s a safety issue if you are landing anything off airport or confined. Heck, I want vented, boosted brakes if taxing very far in a stiff xwind. Brake fade sucks
    And I’m on 31’s

  36. #36

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    Exhaust,

    Since your post was about props I'll make it short. When you get it back, bleed those brakes and make certain pads are in good order. always inspect a system end to end. a double puck brake on a 31 is more than adequate.

    Your black "A" model is great looking. In the hands of a skilled cub pilot you'd be amazed. So spend your money and time to gain the experience and be that pilot. Don't throw money at parts (at least initially). Safety is a term thrown around loosely and prioritized differently by individuals.

    I trust you're a hard-charger who wants to get after it...so take what you got and fly the snot out of it each and every day!

  37. #37

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    Bailey I’m flying as much as I can. Got the plane in July so we are still new best friends but doing what I can to learn how it works.
    my pads are all good. Just put skis on few weeks ago so got a good look at everything. I think they needed to be bled before. I’ll skip the prop for now unless a screaming deal pops up. Luckily I can run auto gas so I get double the flying time for my money!

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