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McCauley 7140 vs. 7440

Composite Prop

Sorry, I don't remember the static or climb rpm. SL standard day, after several minutes WOT it will stabilize around 2850 rpm. I'll try to see if I can find the other information for you.

Jim
 
>SL standard day, after several minutes WOT..... <

Wow, you must live way north of me. The dISA has been running about 34 to 39 degrees F around here lately. Send some of that cold weather down this way...... :)
JimC
 
Composite Prop

Nope, North East Texas. The testing was done last winter and I just remember the flat out rpm. And it's only supposed to be 100 for the rest of the week.

Jim
 
Jim, We're only supposed to be above 100 for two days this week, so we're better off than ya'll are. Want me to get a big fan and point it in your direction?
JimC
 
Re: Composite Prop

X18 said:
Sorry, I don't remember the static or climb rpm. SL standard day, after several minutes WOT it will stabilize around 2850 rpm. I'll try to see if I can find the other information for you.

Jim

Thanks for the info Jim. Don't go to a lot of trouble to check the static or climb. I checked with Sensenich and the lead time is a little longer than I want to wait.

I'm thinking of getting a 1B90CM7440. If I'm not happy with it I can have it cut and re-pitched in the future if I want to. It's easier to make 'em shorter than to make 'em longer!

Thanks again,
Clyde
 
Finally tried a McCauley 7440. As JimC predicted it does not pull the plane on the step as well as the 7140.

However... strange as it may seem, it climbs better. 7440 climbs about 50 to 100 ft/min faster than the 7140.

I must admit that tests were not conducted under perfectly controlled conditions, but the numbers seem to consistently favour the 7440 from a climb perspective.

7440 RPMs are about 50-100 less than the 7140. The 7440 prop also seems smoother.

I'm thinking that a 7438 would be optimal.

Any thoughts on this?
 
Generally an old rule of thumb is that if you increase the diameter 1" you reduce the pitch 1". The result should give you slightly better acceleration and climb performance due to the larger diameter of the prop blast. The engine likely will seem smoother due to the better flywheel action. A long slow turning prop will give more thrust thus better performance on slower Cub type airplanes. On higher speed planes the long prop will generate more drag. Generally the prop diameter is restricted by ground clearance requirements, which is why a float plane is able to use a longer prop. Years ago I experimented with several different props on a 150 hp 7GCB on floats. The original prop was a 7456. The cruise was about 103 mph. I settled on a 8046 prop. I know this doesn't follow the rule of thumb. The cruise remained the same while the take off time was reduced by 1/3 and the rate of climb was increased by about 1/3. It also ran a lot smoother. I also ran this prop on wheels (8.50 x6) with excellent performance.
 
I currently use the 75-35 1a90 on my 0-200.I think the 75-38 may be the best combo.

Bill
 
McCaully 7140 vs 7440

Hi guys I have a pa-11 with a c90-8 have a 7144 and a 7440 the 7144 seemed to get off better on wheels and floats but the 7440 was better on skis, did some upgrades and now run the 7440 all the time and turn about 2475 on t/o but have to throttle to about 1/2 throttle in level flight, may not be quite legal but it's a lot more fun. also have the 25x11x4 Goodyear tire so prop clearance is no problem.
 
Re: McCaully 7140 vs 7440

Douten said:
Hi guys I have a pa-11 with a c90-8 have a 7144 and a 7440 the 7144 seemed to get off better on wheels and floats but the 7440 was better on skis...

Strange that the 7144 outperforms the 7440. What RPMs are you getting with each prop?

I know of a C90 J3 on EDO 1320s with a 7146 that seems to outperform everything in sight. Could be an exceptionally light airframe ... I'm not really sure why it does so well.
 
Can't really remember but seems like about 2375 with both, but was reading my cub club newsletter and they were talking about having a 65 intake spider on instead of the 75-0-200 and low and behold I had the 65. since then have changed intake, carburetors, and done a few more mods and it really woke up a smart airplane. Love the 7440 so much I haven't even tried the 7144 for a couple of years now but feel like I could use more prop now. turning 2475 -2500 on climb out and have to throttle back to about 1/2 in level flight. getting off in about 150'-170' when light. we'll see if I can finally beat the T-crafts in Greenville this fall. pretty hard when you give them a 40-50 pound pilot advantage and they are some great seaplane pilots.
 
It's a McCauley, I have a local seaplane with a sensenich on a 95 hp super cub but have not tried his prop yet and don't know that pitch. I tried a sensenich 7443 against my 7144 and it was about 2-3 seconds longer off the water when on floats. also measured my McCauley against a older one and the prop width in different places were not the same. don't understand why.
 
About a year ago, in a post about 7535 performance, throughout most of the post I typoed '7545' instead of '7535'. Saying

"No, I'm not saying that I would prefer to run the 7535. There are five classes of overspeed (Categories Ia, Ib, IIa, IIb, and III). Running an O-200, you can easily reach a IIb overspeed with the 7545 (I was careful not to exceed IIa, which has the same inspection requirements as Ib). You can probably reach IIb with a C90 as well. A IIb overspeed would require that you replace the rod bolts and nuts, among a number of other unpleasant and potentially more expensive consequences. I've run a 7441, liked it, think a 7440 would do better than the 41, and that a 39 might be better still (I'm not in a hurry to get anywhere in a cub). Any flatter, and you run a severe risk of hurting the engine. I run a 7142 on a daily basis and think that on an O-200 (and probably a 90) it is a great compromise prop that won't lead a prudent pilot to hurt the engine. Being careless with the 7545 could lead to the need for an overhaul or worse within a very short period of time. That said, the 7545 performance is quite impressive, including a 55 mph climb at full rated rpm (2750 rpm) on a 95 degree day -- the 7545 just comes with a potentially exorbitant penalty".

Needless to say, I meant to say, "7535" instead of "7545". Nobody commented, so I figure all of you knew what I meant, but I thought I'd take this opportunity to correct it anyway.

BTW, my 7441 has been repitched to 7440, and I'm looking forward to comparing it against my 7142, but FedEx has been bouncing the package back and forth between Portland and Everett for two weeks now (was supposed to have come to a small town near Memphis). FedEx says it is being mis-scanned (15 scans so far between Portland and Everett), but they also say they can't do anything to stop the bouncing or redirect it toward Memphis.
Oops & Arrgh,
JimC
 
Douten, I'm curious about the 95hp SuperCub. Did you do it by STC or 337 ? Though Continental allowed the C90 to develop 95 hp during takeoff, Piper prohibited it; limiting the maximum power to 90.
JimC
 
Piper called it a PA18-95.
SCowners_manual.jpg
 
Interesting.
The PA-18 Type Certificate (T.C.D.S) 1A2 limits the engine to a maximum of 90 hp, so it isn't allowed to produce 95hp without a 337 or STC.

Reference, T.C.D.S. 1A2, Page 2, Line 1
Engine Limits For all operations, 2475 r.p.m. (90 hp.)

The use of the term PA-18-95 must have been a marketing ploy, since the type certificate didn't allow the engine to actually develop that horsepower under any circumstance.
JimC
 
P.S. Much the same is true for the J3 and PA-11,

where for the J3, T.C.D.S. A-691 Item 311. C. (10) limits the power of the C-90 to 90 hp on takeoff and 80 hp for all other operations.

And for the PA-11, T.C.D.S. A-691 Item 311. D. (5) limits the power of the C-90 to 90 hp on all operations
JimC
 
P.S. Much the same is true for the J3 and PA-11,

where for the J3, T.C.D.S. A-691 Item 311. C. (10) limits the power of the C-90 to 90 hp on takeoff and 80 hp for all other operations.

And for the PA-11, T.C.D.S. A-691 Item 311. D. (5) limits the power of the C-90 to 90 hp on all operations
JimC
P.P.S. Airplanes is strange creatures, and their paperwork is even stranger.
 
maybe you misunderstood my comment I don't own the pa18-95, I have a pa-11, I noticed the other day that I turn 2475 on a steep climb then I throttle back to about 1/2 in level flight cruise about 85 indicated.
 
Sorry to bring up this old thread. I came across a 7535 prop in good condition. It's for a pa11. It sounds like it should be a fun prop for short field/climb performance. My only problem is my pa11 has a c85. Will that be to much prop for stock 85? Also is $1400 a decent price I cant seem to bring up any comparisons. Thanks
 
Sideslip,
That is a great prop for you, those are scarce as hens teeth, if its got good width out at the tips, $1400 is a very fair price, have heard of them bringing up in $2-500 if minty. A buddy just told me he is getting a new one with 38" pitch for his 90hp PA11, said the quoted him $3300 bucks , so your less than half price! The longer prop will generally get your tail up faster, push you up otta ground effect better, pull you onto the step faster, generally climb out
Better, usually longer disk is smoother, and your approach will be slower with both props windmilling when one is longer with less pitch.
Used to run a 74/40 on my 90 Cub and it worked good around 8 secs on 1320s, got a 75/38 and got 7 secs all the time. Great skiplane prop as well, been years but 82 mph cruise at 2300 seams to ring a bell, better grab it if its in good shape!
Have no idea on legality of it on your application.......
 
Sideslip, As Turbo Beaver said Grab the prop if its not junk, I used that pitch on my pa-11 90 for take off comp. in Greenville, ( Yes Glenn I remember the little girl beating me, I will never live it down ). The prop should do good with the 85 and great if you do the 0200 conversion down the road. I use a 7438 with my Amphibs that works great, last summer I ran my 7144 when going to LockHaven cruised about 85 on the Amphibs but had to be careful as it doesn't perform as good.
 
Douten did you notice a difference from the 7144-7535? I'm currently running a 7140 and it seems to do pretty good(2300 rpm at TO with a c85), but after playing around with a friend who has j3 with a c90 (kicked my ass if you ask me). I guess I'm just asking you guys with experience with these props if it would be more of a parallel move, or is it going to my smile even bigger?
 
Sideslip prepare yourself for a grin from ear to ear, however dont compare an 85hp engine to a 90hp engine , one is basically a hotter version of a 65,
The other is really a different animal, when the Greenville fly in first started and there were alot more"little floatplanes" compeating, there were quite a few J3s and PA11 / 85hp that got "egg in their face" going against 7CCM Champs with 90hp engines , not the same story if the he cubs had a ninety.......... they would usually have the champs by a second, all things being equal............ you needed 7 secs or less ,to be at the banquet later that nite!
 
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When I was competing in the mid and late 70's at Greenville with my 39 J-3, no one ever beat it. It was powered with a stroked 83 swinging a sensenich 76AK2-38 (74" ag. prop for the 85). It would turn that prop 2575 tied down and 2625 going onto the step. That was good; but remember that the 85 has to turn up handy to 2700 to reach a real 85 HP., and even this one didn't do that! That cub on 1320's from the back seat, would consistently make 5 to 6 sec. takeoffs, and even Kathy Hodgekins PA-11 ( Which was very stiff competition) couldn't quite beat it. My point being; I never had a float plane with too much horsepower; but I've seen plenty that should do better than they are doing; usually not the right prop for takeoff; you can't have it both ways. Fun topic.
 
Nice pics Douten.Don't think Glenn ever beat that girl either;-)

Sideslip a J-3 with a 90 will kick everyone's ass if flown correctly and $1400 is a great price for a Mac 75/35 if it is any good.

Bill

Everyone except the guy who posted before me!
 
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