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Catto update.and ??

Gary, maybe he could download that accelerator app you had... that looks pretty cool to me!!
John

Here's what we discussed on the Taylorcraft Forum. It's a potential means to capture and analyze acceleration data obtained with either Android or I-Phones that have imbedded G-sensors. They use that for sensing phone position and other diagnostic and display stuff. It may have potential for testing props and other power alterations. JimC mentioned it and I looked it up but am no expert...but interested.

"Briefly my wife consented to download an acceleration app from Apple to her I-Phone. Three axis X-Y-Z planes with + and - G values ref to phone position. Start run and stop run plots a stream of 3-axis data. Others offer plotting software to export and plot the results. Will cost me a dinner for two her choice.

https://itunes.apple.com/us/app/acce...499629589?mt=8
https://developer.apple.com/documentation/coremotion/getting_raw_accelerometer_events

JimC have you experimented with this tech? It's like ...why is this news? I would have thought the builders and modders would have figured a way to apply this to their alterations by now and discussed it.


Gary"
 
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Here's what preceded the suggestion by Jim C for an accelerometer. Time stamped it might add to the readily available Butt Dyno Method of prop testing. In my experience some props go flat early as far as pull during takeoff and climb. Pitch (fixed or variable) can help bracket the optimum performance window I believe. It's more noticeable on low power engines due to the extended takeoff and climb. Yes power increases as rpms rise but probably not with a jump like I've seen on my Taylorcraft.

"The critical point for me about power and props is on floats when going from a step-plow to planing and then accelerating to takeoff speed. There's lots of water drag to overcome unlike on wheels. I'd have to guess that's 15-40 mph but so far never tried a GPS to pin that down better. It would take an onboard camera looking at or integrating the GPS' speed/time readout and plane's attitude out the windshield.

Taxiing slightly nose up, then the bow rise to plowing under power followed by nose down as the floats climb up to a planing attitude just like a boat. Light that's a quick event but heavy it can take several long seconds if it ever happens. Sometimes weight reduction is the only way to get on step.

On skis takeoff distance can be measured via tracks in the snow. That would be another way to compare propeller and power performance especially if the snow were deep.

With the right diameter and pitch the "air traction" can be felt especially with puny power from these small Continentals. The plane suddenly accelerates at some forward speed after power application. When that surge happens during takeoff can be adjusted via propeller pitch at a fixed prop diameter, and probably between propellers of the same diameter and pitch configuration between manufacturers (the prop's airfoils, shape, and chord vary).

Doing a static pull at 0 forward speed is a crude way to determine performance with my high drag criteria."

Gary
 
Gary,
Some darn good suggestions there! Our assessment of composite blades is there must certainly be ALOT more flexing in them than an Aluminum blade. And you should notice more of an RPM increase as your rolling from static
thru rotation, Most guys see Less rpm with their Catto over their Borer static. But usually report similar rpm by lift
off. Often notice slightly higher numbers in climb out.....
And regardless of what the tach is reading static, if you can turn it up (or over) redline when wideopen in level flight; you are close to being pitched correctly for your outfit! The fact that almost all the top dogs winning T/O contest in late years using composite props, speaks for
Itself! Back 30 years ago when lots of folks were just finding out in lower 48, about Roger Borers prop. They all
thought they had " gone to heaven" and a common discribtion was they had found "another 20hp".
If your an old 82/42 Borer man, try the big Catto 84/36
It will be an eyeopener for sure. Watch this thread when Larry gets his bolted on. Bet the old Borer gets stood in the corner as a "spare prop"........
 
One theory of fixed pitch props is they experience increased AOA as rpms increase, and decreased AOA when forward speed and airflow increase. Blades are twisted and airfoil shaped by design to maintain AOA and improve thrust across its span while keeping vibes and bending acceptable. Lots of black magic goes on there.

https://www.youtube.com/watch?v=R7hyrD9-R4A

For fixed pitch metal props on floatplanes the change in AOA and resulting thrust can often be heard as the plane goes from idle to planing. At first there's lots of noisy popping sounds while getting on the step as static rpm is reached. I assume the blades are partially stalled or at least inefficient due to AOA. As speed and airflow increase (providing the plane can get on step due to load and power) AOA decreases as the video implies and thrust improves with resulting acceleration. The prop sound smooths out and the plane might eventually takeoff.

However too flat a pitch can result in decreased thrust at some airspeed. It's a compromise we experience with a fixed pitch prop. I like to see redline at WFO as well.

What composites do in the same situation I don't know. Performance reports indicate their magic works, but sometimes how and why isn't as important as the results. Experimenting with acceleration measurements might offer some clues if the data can be plotted versus stage of flight.

Gary
 
Good stuff there Gary.......
In summary maybe we should just call a Catto prop,
"Pure Magic" on a Cub?
 
Here's what we discussed on the Taylorcraft Forum. It's a potential means to capture and analyze acceleration data obtained with either Android or I-Phones that have imbedded G-sensors. They use that for sensing phone position and other diagnostic and display stuff. It may have potential for testing props and other power alterations. JimC mentioned it and I looked it up but am no expert...but interested.

"Briefly my wife consented to download an acceleration app from Apple to her I-Phone. Three axis X-Y-Z planes with + and - G values ref to phone position. Start run and stop run plots a stream of 3-axis data. Others offer plotting software to export and plot the results. Will cost me a dinner for two her choice.

https://itunes.apple.com/us/app/acce...499629589?mt=8
https://developer.apple.com/documentation/coremotion/getting_raw_accelerometer_events

JimC have you experimented with this tech? It's like ...why is this news? I would have thought the builders and modders would have figured a way to apply this to their alterations by now and discussed it.


Gary"

not that i have time or extra brainpower at the moment.... but I write IOS apps, what would the ideal app look like & track?? doubt there's a big enough market to make it worth writing..(or for apple to approve it after I spend time writing it!!)
 
not that i have time or extra brainpower at the moment.... but I write IOS apps, what would the ideal app look like & track?? doubt there's a big enough market to make it worth writing..(or for apple to approve it after I spend time writing it!!)

I'm not a programmer or engineer, but I wonder if acceleration data collected during takeoff can be formatted to describe the performance of one propeller configuration. And if desired, over another during a similar event? Same conditions for each test plus gross weight as light anything can elevate quickly.

It can be demonstrated already via time for takeoff or ground distance travelled like Valdez. But what might be interesting is where in that event does each prop's efficiency max out and acceleration change. Like a race...some start slow then speed up versus others that start fast then slow down? At some point it's potentially a tied race.

Beyond that there's the rate of climb after takeoff. Does one prop's thrust and advance rate maintain or increase once airborne while comparatively the other's work is almost over? That's what happens with a fixed pitch...it's a design choice. Manufacturers offer a range of pitch and diameter to fit the need with fixed pitch props.

I don't know if it's worthwhile over what's already done. Compare these factors> takeoff time - distance - capture acceleration versus time and plot extracted from a source like a phone or ? - then rate of climb at target airspeed. Note which prop performed the best where desired.

JimC mentioned in the Taylorcraft Forum that race cars use this tech but he didn't elaborate how and then what. I'll leave it for discussion.

Gary
 
Personally I think it would be extremely hard to get good data without sophisticated software, numerous sensors, and a lot of time(experience).
They have sold G meters for street cars for years before the iPhone was invented, and while the phone is now way more powerful, you’re dealing with air, not pavement.
Traction on the ground can allow sensors to see extremely small changes in acceleration rates, rotating wheel load, and just about any force applied onto the vehicle or road.
When dealing with air, you might be better off to start with fluid dynamics of water, and then divide it down by 784 times to see the effect on air.

In regards to composite props, a couple of notes I’ve not seen mentioned. One is composite builds allow for designs they can not achieve with metal, due to issues with harmonics, vibration and fatigue. So guys can get real creative to address different aspect of the flight realm. The blade diameters and profiles are such we’ve never seen before in metal props. Simply awesome stuff.

The other is I believe a composite prop ideally suited for your application should flex (twist, flatten, etc) under heavy load!such as takeoff and climb, and then “unload” in cruise, increasing pitch to allow for more bite. One example was a Catto prop I tested, and while it was too much prop for my power output, after leveling off into cruise attitude and letting the speed build up to its stabilised pace, approximately 30-40 seconds later the rpm would drop slightly and the airplane would pick up 3-5 mph. I attribute this to the ability of the layup to flex, or twist under load.
Also, props that are cut down to resize to your engine are not an ideal profile. If it’s not designed for your power, airframe and application, than it’s a compromise.

I have stated this before, and as before, it’s just my opinion. And that is I believe Catto, through lots of trial and error, has been able to find blade profiles that works extremely well on a few engine and airframe combos. I don’t believe it’s as straightforward as a math formula, because as many owners will tell you, it often takes 2-3 props to find the right one from them. And that’s on a 320 or 360. Ask them to prop a different horsepower, and their method of deciding which prop to use is “how fast do you want to go at what rpm?” Instead is basing a selection on power and drag, they use the simple formula of a screw turning through the air. Without slippage, the blade travels forward with every rotation the number of its pitch. Multiple by rpm and you get speed. They just work backwards, assuming your aircraft has plenty of horsepower and no drag. Therefore it’s easier to make it work on high hp applications. And impossible to work on small hp applications. Add that to the fact that they keep no database of what prop ended up working best on Buckys Backyard Bomber running a 428CJ motor, and now they don’t even have a baseline to build on, other then someone’s memory.

I could go on but I’m severely digressing from the original response. And that is, pretty hard to measure quantifiably.

Want to find the best prop for an application? Buy or borrow a composite ground adjustable prop of the appropriate diameter. Dial it in on your airplane, and then either buy your own, or order a composite prop to that spec.


Sent from my iPhone using SuperCub.Org
 
Nothing like deep snow to test a prop. Same for floats. Time or distance easy to measure.

In these parts a Catto is like a cat that draws the ramp dogs. Maybe that will eventually change.

Gary
 
If anyone is curious: My new Catto 84/36 was delayed in shipping from California due, I suppose, to a backlog of orders at the factory. When it was finally shipped by Fed Ex it ended up being delayed at Customs in Ottawa (on the other side of the country!) since I had neglected to designate a customs broker. I believe it's now on the way to me and hopefully it arrives in the next week. Looking forward to seeing and testing it.
 
If anyone is curious: My new Catto 84/36 was delayed in shipping from California due, I suppose, to a backlog of orders at the factory. When it was finally shipped by Fed Ex it ended up being delayed at Customs in Ottawa (on the other side of the country!) since I had neglected to designate a customs broker. I believe it's now on the way to me and hopefully it arrives in the next week. Looking forward to seeing and testing it.
Hang in there olde boy, its worth waiting for. Bet you really appreaciate it as soon as you try it!
E

Sent from my LM-X210 using SuperCub.Org mobile app
 
It arrived yesterday! Beautiful!
Now I just need some time and reasonable weather to do the swap. My hangar is un-heated and it's still around zero (F) here.
I can't imagine a scenario in which I would want to return this new prop. By all accounts on this forum, it will perform as well or better than my old Borer, and my primary motivation was to save a bunch of weight out front. With just six weeks left in the prime ski-flying season here, and my damned "retirement" job getting in the way, I may not be able to do any useful comparison testing.
 
Some numbers:

"Borer" 82/42

Prop 34.0 lbs
Hardware 1.5 lbs (bolts, washers, "skull cap" spinner)
________
Total 35.5 lbs

Catto 84/36

Prop 14.6 lbs
Hardware 4.5 lbs (nuts, bolts, washers, crush plate, spinner flange, carbon fibre spinner)
_________
Total 19.1 lbs

35.5 lbs
- 19.1 lbs
________

Weight saving 16.4 lbs

(subject to new W&B calculation, I should be able to remove 6 lbs of ballast from the tail. On that assumption, the net weight saving in my case is around 22.4 lbs)


Larry
 
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I'm looking forward to hearing some comparison numbers of the 84/36 vs the 82/42. Static, ROC, cruise speed vs. RPM etc. Do you have a 150 or 160?
 
160.

Sorry to disappoint, Perry, but I've already swapped propellers. The weather has been warm enough to work in my un-heated hangar, but the light is too flat to go flying, so I changed it over today. So any results I might provide will be strictly subjective, seat-of-the-pants stuff. I did have good intentions, but …..

DSCN0396.jpg
Before: Borer 82/42

DSCN0397.jpg
After: Catto 84/36

My only complaint is that the shiny, new Catto makes the rest of the 'plane look a little shabby!
 

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Well I'm really interested in how it climbs and how the cruise is affected, if any. I don't know where your CG is now, but I'd fly it without pulling any tail weight to begin with. I think you'll be really happy with the pitch feel.
 
160.

Sorry to disappoint, Perry, but I've already swapped propellers. The weather has been warm enough to work in my un-heated hangar, but the light is too flat to go flying, so I changed it over today. So any results I might provide will be strictly subjective, seat-of-the-pants stuff. I did have good intentions, but …..

View attachment 42451
Before: Borer 82/42

View attachment 42452
After: Catto 84/36

My only complaint is that the shiny, new Catto makes the rest of the 'plane look a little shabby!
Nice problem to have Larry! Looks great! Wait till you see how it will sustain in the climb out. Regardless of what you see static, as soon as you get up and level out push the throttle wide open and see what it will turn it holding your altitude flat. If your engine will spool it up to Redline or just over: You got it all![emoji106] Good Luck
E


Sent from my LM-X210 using SuperCub.Org mobile app
 
I finally got a chance to fly the new Catto prop this afternoon!

1) At idle, it was pulling harder. On the very slight uphill grade from my hangar, at about 800 rpm, I had to stand on the brakes to prevent it from creeping ahead.

2) It is definitely smoother than the old Borer.

3) At full throttle I could only get to about 2600 rpm (indicated - my tach has not been checked for a while).

My oil cooler is about two-thirds covered and yet, at minus 15C (+5F), the oil temperature barely got off the peg (130F more or less). The oil pressure was up around 95 PSI. I imagine there was some power loss there.

I thought I'd try flying it without removing the six pounds of lead in the tail. I couldn't get enough nose-down trim, so the weight is coming out tomorrow.

Landed off airport on the snow of the arctic ocean. Conditions here are almost ideal. I just need a bit more tension in the bungees, another job for tomorrow.

So with the other adjustments that need to be made I wasn't able, yet, to give that prop a thorough test.

I hope to be ski-flying for about another month, while the rest of your are getting your floats on!
 
I finally got a chance to fly the new Catto prop this afternoon!

1) At idle, it was pulling harder. On the very slight uphill grade from my hangar, at about 800 rpm, I had to stand on the brakes to prevent it from creeping ahead.

2) It is definitely smoother than the old Borer.

3) At full throttle I could only get to about 2600 rpm (indicated - my tach has not been checked for a while).

My oil cooler is about two-thirds covered and yet, at minus 15C (+5F), the oil temperature barely got off the peg (130F more or less). The oil pressure was up around 95 PSI. I imagine there was some power loss there.

I thought I'd try flying it without removing the six pounds of lead in the tail. I couldn't get enough nose-down trim, so the weight is coming out tomorrow.

Landed off airport on the snow of the arctic ocean. Conditions here are almost ideal. I just need a bit more tension in the bungees, another job for tomorrow.

So with the other adjustments that need to be made I wasn't able, yet, to give that prop a thorough test.

I hope to be ski-flying for about another month, while the rest of your are getting your floats on!
Larry,
Your comments echos what most others, that are firmilar with the Catto prop notice! As soon as you get warmer conditions you can get a better feel for "faster spool up" and the advantages moving more air by the tail, can have trying to lift it loaded
aft. Keep us all posted on your experiences with it in comparison to the Borer.[emoji5]

Sent from my LM-X210 using SuperCub.Org mobile app
 
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