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Author Topic: Prop Chart for Glo Engines  (Read 2032 times)

Offline Mike Griffin

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Prop Chart for Glo Engines
« on: April 17, 2018, 08:33:22 PM »
Is there a good chart showing the best prop size for the size engine you will be using for Control Line Flying? Most everything I have been able to find is for RC flying. 

Thank you
Mike

Offline Brett Buck

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Re: Prop Chart for Glo Engines
« Reply #1 on: April 17, 2018, 09:43:29 PM »
Is there a good chart showing the best prop size for the size engine you will be using for Control Line Flying? Most everything I have been able to find is for RC flying. 

     There are, but as long as you just look at size, it's not going to be correct. You have a McCoy 19 Redhead, and a OS-20FP .both are ~20s, one wants an 8-6, and other wants a 9-4 or 10-4. Fox 40 Large Case VS 40VF, same thing.

    For a chart, what do you put in for a the "40" box - 10-7 to 12.25-3.75? You see the problem.

     For a particular engine, you either make an educated guess and experiment from there, or you find someone else who has done the same.

     Brett

Offline Mike Griffin

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Re: Prop Chart for Glo Engines
« Reply #2 on: April 18, 2018, 08:44:27 AM »
     There are, but as long as you just look at size, it's not going to be correct. You have a McCoy 19 Redhead, and a OS-20FP .both are ~20s, one wants an 8-6, and other wants a 9-4 or 10-4. Fox 40 Large Case VS 40VF, same thing.

    For a chart, what do you put in for a the "40" box - 10-7 to 12.25-3.75? You see the problem.

     For a particular engine, you either make an educated guess and experiment from there, or you find someone else who has done the same.

     Brett

Hi Brett

Thank you and I kind of had a sneaking suspicion that might be the case.  I know there are variables that come into play.   All the charts I have ever seen seem to be just a "close" guide.   I appreciate your help and I do have a healthy supply of props i can experiment with.  Thank you again.

Mike

Offline Chris Fretz

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Re: Prop Chart for Glo Engines
« Reply #3 on: April 18, 2018, 08:51:30 AM »
Maybe someone could make one that is engine specific by popular control line engines.
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Offline Mike Haverly

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Re: Prop Chart for Glo Engines
« Reply #4 on: April 18, 2018, 09:26:35 AM »
Maybe someone could make one that is engine specific by popular control line engines.

Chris, please read and understand what Brett just wrote.  There is no "go to".  Some things work on some set-ups and some don't.
Mike

Offline Scott Richlen

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Re: Prop Chart for Glo Engines
« Reply #5 on: April 18, 2018, 11:17:02 AM »
So that TopFlite nylon 10-6 I've been saving for all these years.....? ;D

Offline Steve Helmick

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Re: Prop Chart for Glo Engines
« Reply #6 on: April 18, 2018, 11:45:38 AM »
Old nylon props should be sawed in half and trashcanned or used for collector's items. I well recall Chris Gomez flipping a NOS nylon prop; it backfired and threw a blade. We were real happy that the engine didn't start and then throw the blade. Just say "NO!". 

We probably remember the old Top Flite prop chart. Even then, it said that the chart was only a starting point. In general, I'd say that the diameters shown on the chart were about right, but these days you'll want to start with around 4" pitch for "snarly port" engines...if they are stock cylinder timing. With "stunt reworked" R/C engines, the tuner should give some propeller recommendations, but as always, those are just starting points. LOTS of performance comes from the propeller...right or wrong, good or bad.  y1 Steve
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Offline Brett Buck

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Re: Prop Chart for Glo Engines
« Reply #7 on: April 18, 2018, 12:16:13 PM »
Maybe someone could make one that is engine specific by popular control line engines.


  Maybe, but we have already been doing what you really need to know, essentially, publishing various complete setups with all the necessary details. Even for a particular engine, it depends on a lot of other factors. I have extensively run two different systems on the 40VF, the original first-generation system that uses a 12-3.25 Bolly 2-blade depitched from a 12-6, and Paul Walker's, which uses a 11.3-4.25 which uses a cut-down 11.75-4.25 Bolly. Never mind that neither of these props are easily available today, but the rest of the system and the way it operates is completely different.

   Change the venturi by .005, and you might want a different prop or a completely different everything else. My system runs significantly differently if it uses Powermaster RO-Jett 10%, Powermaster "Air" 10%, and won't run properly at all on Powermaster GMA 10%, to the point that I adjust the percentage of each fuel type to get the run I want. If I go to Tucson, I run Powermaster YS 20/20, along with .35" of additional pitch.

   So you have to specify all the relevant parts. There have been multiple examples of that, including the SN article that delineated most of the current competitive systems in exquisite detail.   If you haven't seen your chosen combination, then it's probably because not enough people with the right kind of knowledge have used it and come up with something they know will work.

 I ran a os35FP iron-liner engine in the ST46 era, but I didn't run it enough to determine if it was as good as you could do, or whether it was repeatable from engine to engine, so I would never post my notes on it. This is the case with most of the vintage and erzatz engines people come up with, like (for example purposes only) a Brat 28. It runs OK, but as far as I know, no one with the necessary knowledge has ever attempted to develop a system for it. Maybe it's the best stunt engine ever and will make us all forget about the PA75, but we will never know that unless people with the necessary knowledge spend a lot of time working on it. And no, you CANNOT make a fair evaluation of 6 different engines in an afternoon (since there is a moderately well-known engine reviewer who does/did exactly that). It takes months or years of careful work.

  BTW, in case this seems like a modern development, even when such things were published in the 50's-60's, when all engines were attempts to recreate the Fox 35, it still wasn't right or very useful and had similar problems. If you look in the "35" slot you would see "9x5-10x6", and if anyone thinks those provide equivalent performance on, say, a Nobler, then you need to go out and try it and find out for yourself. Similarly, a Y&O 10x6 and a Top Flite 10x6 were hardly equivalent, either.

    Generally, you run 4" of pitch or so on modern engines, and 6"ish on vintage and "retro" engines, with correspondingly different launch RPM.

     Brett


 p.s. another factor is the fact that in the good old days, the engines varied so much from example to example that you couldn't realistically come up with one system that someone else could reliably repeat - meaning that publishing the setup didn't make any difference, or at best only gave you a notion what to do with *your* particular engine. Most of the current modern engines are also dead-nuts repeatable from copy to copy, and if you set up your engine the way David does, it's probably going to run the same way.

Online Fredvon4

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Re: Prop Chart for Glo Engines
« Reply #8 on: April 18, 2018, 01:44:43 PM »
Mike I came back to this to find Brett already note my thoughts

Here  we have pretty much what you seek and I have been exploiting it for years now

Just about any engine and plane combination is discussed on line
Fuel, tank, prop, venturi, etc

For my sport flying   this site and a few others have saved me a lot of experimenting....BUT then ---I am NOT trying to eek out Max performance,,,,,just a great starting point--- and if good enough for my goofing off...DONE

I would note that I try hard to use the Engine original manual for the proper range of props paying attention to THEIR recommended break in size and fuels...that I compare to on line recommendations

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Offline Mike Griffin

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Re: Prop Chart for Glo Engines
« Reply #9 on: April 18, 2018, 03:25:14 PM »
I appreciate all of the good information.  Over the years I have pretty much done what Brett suggested to find a combination I liked but I really do not fly that much anymore and have forgotten a lot of what I used to know.  There is wealth of knowledge to be found on here just by asking.  I was trying to find a good combination for the IMITATION i just finished which will be powered by one of Randy Smith's LA ,46.  I called Randy to ask him what prop he has found that works well with that engine and he told me the  11 x 4.5 Cyclone Prop from Thunder Tiger worked well with that engine.  That is what I am going to start with.

Since I have always been pretty much of a sport flyer, I have never invested in the high end PA type engines (Ro Jett or PA).  I fly a lot of OS LA.46, Super Tigre .51, Super Tigre 46  the OS series of .20, .35 and .40 (Lou Woolard) 

Thanks again for the input guys.

Mike

Offline Tim Wescott

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Re: Prop Chart for Glo Engines
« Reply #10 on: April 18, 2018, 03:50:24 PM »
What Brett said.  The only thing that I can add is that if you're running an OS LA-series engine (and, I suspect, equivalent Schnuerle-ported engines), the heavier the plane, the smaller the prop you want to run -- and you'll want to experiment with venturi size and possibly fuel to get the run correct for the specific prop that you chose.  Go to a different prop, and expect to dink around with the venturi setup before things are right.
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Offline RandySmith

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Re: Prop Chart for Glo Engines
« Reply #11 on: April 18, 2018, 04:58:07 PM »

  " Maybe, but we have already been doing what you really need to know, essentially, publishing various complete setups with all the necessary details. Even for a particular engine, it depends on a lot of other factors. I have extensively run two different systems on the 40VF, the original first-generation system that uses a 12-3.25 Bolly 2-blade depitched from a 12-6, and Paul Walker's, which uses a 11.3-4.25 which uses a cut-down 11.75-4.25 Bolly. Never mind that neither of these props are easily available today, but the rest of the system and the way it operates is completely different.  "

OH  not anymore, I have the  props in stock, the  2  we make  are the  Old  BOLLY  12.2 x 4.2  and the 12.25 x 2.25, these also are where the  11 3/4 x 4 1/4  came from, as well  as the  11.5 x 4.25,  ALL of these  actually pitch out at  3.8 pitch on the outer  part of the  props, and you will notice many of these have a  built in  "indent"  where  you cut to trim them to  11 3/4 in

Randy

Offline Phil Spillman

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Re: Prop Chart for Glo Engines
« Reply #12 on: April 18, 2018, 08:21:15 PM »
Hi You All! Today I lived the dream expressed heretofore! I had removed my ill fated G 21 ST .40 from my Brodak FW 190 and replaced it with an ST G21 .46. My initial thought was to mount a Rev Up 11 X 5 prop which I did and flew it 4 disappointing times! It ran OK but not with the authority I had expected for this finally beautiful low wind day! For my final flight/pattern I switched to an old Top Flite 11 X 6 Maple prop, filled my tank with my usual 10 11:11 fuel and cranked her up! Immediately I noticed improved authority and that great throaty Tigre Sound! The pattern was much more to my liking and the plane felt much better. I believe I should have been using 7.5 11:11 fuel since the stick humidity hasn't arrived as yet but I have moved my learning curve a bit down the line!

Half if not more of the fun of this sport is experimentation and today proved my point!

Phil Spillman
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Offline Brett Buck

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Re: Prop Chart for Glo Engines
« Reply #13 on: April 18, 2018, 08:37:12 PM »
<snip>

.... replaced it with an ST G21 .46. My initial thought was to mount a Rev Up 11 X 5 prop which I did and flew it 4 disappointing times! It ran OK but not with the authority I had expected for this finally beautiful low wind day! For my final flight/pattern I switched to an old Top Flite 11 X 6 Maple prop, filled my tank with my usual 10 11:11 fuel and cranked her up! Immediately I noticed improved authority and that great throaty Tigre Sound! The pattern was much more to my liking and the plane felt much better.

     Very strong ST46s with the larger end of the usual venturi range will be OK with an 11-5 on small airplanes, but other than that, you will end up having to run it too hard. In this case, a 12-5 might have worked better (same pitch but more efficient). Stock venturi (.159) or equivalent, you can probably forget 5" of pitch under most conditions, and as you found, 6" pitch is probably a good starting point unless you really know what you are doing. A decent engine will easily handle a 12-6.

    Brett

Offline Scott Richlen

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Re: Prop Chart for Glo Engines
« Reply #14 on: April 19, 2018, 06:03:39 AM »
Mike:

I have found that the Xoar 12-4 works great on a LA-46.

Offline Chris Fretz

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Re: Prop Chart for Glo Engines
« Reply #15 on: April 19, 2018, 07:33:14 AM »
Mike:

I have found that the Xoar 12-4 works great on a LA-46.
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Re: Prop Chart for Glo Engines
« Reply #16 on: April 19, 2018, 08:21:17 AM »
Listen to Brett on the St46 ... he is on the money... I will only make one caveat, and that is his advice is especially true for the wood vintage props you are using. In my experience, Revups of the day pitched light, so 5 pitch was really not enough when it was really 4.5 to 4.75 on the working area of the blade, then there is the thin wood flex. Now with a modern carbon prop pitched a accurately 5.25 to 5.5 and even 6 is fine on a strong st46... at least for me it always was, at sea level over here.

Offline Phil Spillman

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Re: Prop Chart for Glo Engines
« Reply #17 on: April 19, 2018, 08:59:22 AM »
Many Thanks for all of your comments and support! I'll try the 12" props since I have not as yet, in my aging memory, ever used one except on Tigre .60's!

Phil Spillman   
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Offline George Albo

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Re: Prop Chart for Glo Engines
« Reply #18 on: April 19, 2018, 11:05:05 AM »
As already stated in this thread, "Standard" prop sizes are just a starting point. I'm posting copies of my charts so you can get a baseline to start from.
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Offline Brett Buck

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Re: Prop Chart for Glo Engines
« Reply #19 on: April 19, 2018, 11:08:10 AM »
As already stated in this thread, "Standard" prop sizes are just a starting point. I'm posting copies of my charts so you can get a baseline to start from.

     This is about *prop nuts* and crankshaft thread definitions, not about propellor selection - which is a very useful chart.

     Brett

  p.s. the second and third charts were not posted when I did, these are the sort of thing that we were talking about above. The "starting prop" size is not correct for modern stunt engines, and just like the venturi chart that goes around, it gives a reference which people take as a truth. Then they starting trying to figure out why their engine doesn't work with standard size and very frequently come to the conclusion that it's not the prop or venturi that is wrong - since it's on a chart - but something else with the engine, so they start trying to "fix" it. When "fixed", they wind up with 46LAs with less power than a Fox 35.
« Last Edit: April 19, 2018, 11:36:39 AM by Brett Buck »

Offline Scott Richlen

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Re: Prop Chart for Glo Engines
« Reply #20 on: April 19, 2018, 11:29:28 AM »
Quote
Is that Mustang a kit Scott?

Yes, this is the Tom Morris kit of the Pat Johnston design P-51B (he designed this for Tom Dixon.)  With Pat's permission, Tom Morris made a limited run of kits for our club to do as a club build a couple of years ago.  I believe that 3 are completed and another 5 are in various stages of completion.

It is a very good flyer!

I don't know if Tom has anymore of these, but I'm sure that Pat would be willing to cut you a kit of it.

Pat has a full-fuselage version of this and I liked the profile so much, I had him cut me a kit of the full-fuselage version.  The kit is really nice!

Offline George Albo

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Re: Prop Chart for Glo Engines
« Reply #21 on: April 19, 2018, 02:24:54 PM »
     This is about *prop nuts* and crankshaft thread definitions, not about propellor selection - which is a very useful chart.

     Brett

  p.s. the second and third charts were not posted when I did, these are the sort of thing that we were talking about above. The "starting prop" size is not correct for modern stunt engines, and just like the venturi chart that goes around, it gives a reference which people take as a truth. Then they starting trying to figure out why their engine doesn't work with standard size and very frequently come to the conclusion that it's not the prop or venturi that is wrong - since it's on a chart - but something else with the engine, so they start trying to "fix" it. When "fixed", they wind up with 46LAs with less power than a Fox 35.
.  The second upload. I couldn't find a delete file function.  That one was intended to uploaded last. It was in my directory next to prop size selection so up it went
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