Prop Pitch

[Gene Elliott]

Guys,
What are the results of using props of a different pitch? What are the effects of going either way with the pitch? Engine runs faster/slower? Speed affected? I'm flying a Banshee with Magnum 32 with 10/4 prop and she's really fast for me. I'd like to slow it down. Pardon my ignorance, but I would appreciate your input.

Thanks,
Gene

[Dan McEntee]

Guys,
What are the results of using props of a different pitch? What are the effects of going either way with the pitch? Engine runs faster/slower? Speed affected? I'm flying a Banshee with Magnum 32 with 10/4 prop and she's really fast for me. I'd like to slow it down. Pardon my ignorance, but I would appreciate your input.

Thanks,
Gene

   Hi Gene;
    Prop pitch, the angle of the prop blades, is what creates the thrust to pull the airplane. The pitch of the prop also affects how the engine is loaded, and a combination of pitch, needle setting and weight of the model determine if you can get into the best part of the power curve for that engine. Line length can also be used to affect speed of the model. You didn't mention the length of your lines, and that may be necessary to know. You also don't mention any RPM readings or lap times, Lap times are pretty important to know. It tells you exactly what "pretty fast" actually is. You might be able to just go down 500 RPM in engine speed, as long as you don't loose any line tension. As you fly more and gain more confidense, you may learn to like faster lap times than youthink you will. I would say the average person likes their lap speeds in the 4.9 to 5.2 seconds per lap range. Size and weight of the model dictate the speed of that the model will need to fly in order to do the pattern well. That speed will need to be consistant, but in order to "speed up" or "slow down' a stunt model to a comfortable lap time, that is usually done with line length.
   In short, on a new model, I usually start with lines longer than I think I will need. I work on getting the engine run happy and the model pulling well first, then if I think I need to speed up the model to help with line tension and such, I start shortening the lines a foot at a time and sneek up on the optimum lap time for that model.
     I hope this make sense, and I'm sure others will chime in also. To me, this is the basis for learning the pattern and learning how to trim a model is settling on a comfortable model speed and lap time for yourself.
    Fill us in on more details when you can.
  Good luck and have fun,
   Dan McEntee

[Gene Elliott]

Thanks Dan,
I'm using 60 foot lines and using a telephone pole I count off about 4 1/2 to 5 second laps. Not very scientific. I don't know nuthin' 'bout no RPM's. How would one determine the RPM's of your engine? Maybe it's a matter of I need to get used to the speed and work through the dizziness. I really like the tight lines and the pull and when doing a loop, there's no hesitation whatsoever. Really smooth. I might try some different props to see the difference.

Thanks, Gene

[Alan Hahn]

Gene,
When the trust of a prop/engine combo = the drag of the airplane, the plane stops accelerating and will fly at a constant speed. If you lower the pitch of your prop and keep the diameter the same, most likely you will slow down. The engine will speed up (rpm's increase), but probably not enough to make up the difference (it depends on prop efficiency). Another option is to keep the same pitch and increase the diameter. If the engine could keep the rpm the same as with the first smaller diameter prop, the speed would probably increase because the larger diameter prop at the same rpm would make more thrust and so the plane would accelerate until the drag increased to match the new thrust. But usually the engine can't spin the larger diameter prop as fast as the smaller one. So probably you would slow down.

Other prop methods would be to try a different manufacturer or a prop with a different width blade. How the airplane speed changes depends upon the engine and how draggy the plane is. Sorry for the imprecision. A lot of this is trial and error! (emphasis on the "error"!)

Other options would be to decrease the venturi size on the engine--like throttling back (one way would be to put the rc-throttle back on and try different throttle settings). Another way would be to go to a lower nitro fuel.

Finally one way to slow the rotation rate down (but not the airspeed) would be to put longer lines on. 5 foot longer lines would make the rotation rate slow down about 1/2 second from what you have.

[captcurt]

...snip... then if I think I need to speed up the model to help with line tension and such, I start shortening the lines a foot at a time and sneek up on the optimum lap time for that model.
    ...snip
   Dan McEntee

I think Dan meant to say if he wants to spin faster he shortens the lines....

I know Dan knows this but it didn't come across right.  Shortening the lines doesn't make the plane go faster--it just makes the rotational time shorter--the spin rate if you will.

Its like Dan says:  use the prop to get the speed of the plane sufficient to fly properly while the engine is "happy", then adjust the "spin rate" with the line length.

Heavier planes need to fly faster than lighter planes of the same design so the wing can generate enough lift.

As you lengthen the lines, the tension decreases directly.  As the speed of the plane decreases, the tension also drops but as a squared function.

In the ranges we fly, a one foot line change will make APROX 0.1 sec per lap change.

Now here is opinion based on the info you provided and observations of other Banshee (Banshi?)

The plane will fly pretty well on .015" thou braided lines out to at least 62' perhaps longer if the trim is good and the plane is light. 

If you have a 10-4 on it, you might try a 3.75 pitch if you can find one.

Else try setting the needle slightly slower before launch--try it just on the fast side of the point where it is breaking from 4 to 2 cycle. 

Finally, if all of this is a bit much--try to find an experienced CL flyer to help you

Have Fun

Curt

[Bill Gruby]

Gene;
  My turn, on this page there is a thread titled "Missing Formula" in it you will find more information on prop pitch than you will really care to know.

          "Billy G"   

[minnesotamodeler]

Ain't it the truth.

--Ray

[Gene Elliott]

I just got back from reading that other thread. It's going to increase sales of headache medicines considerably. In fact, I'm going on vacation for a week starting tomorrow to recuperate. Seriously, thanks to all. Be back in a week.

Thanks, Gene

[Dan McEntee]

Thanks Dan,
I'm using 60 foot lines and using a telephone pole I count off about 4 1/2 to 5 second laps. Not very scientific. I don't know nuthin' 'bout no RPM's. How would one determine the RPM's of your engine? Maybe it's a matter of I need to get used to the speed and work through the dizziness. I really like the tight lines and the pull and when doing a loop, there's no hesitation whatsoever. Really smooth. I might try some different props to see the difference.

Thanks, Gene

   Hi Gene;
      Sorry for the confusion. I was just assuming you were using a tachometer to set your engine speed. On engines like you are using, and most modern ABC schnuerle ported engines, I find it hard to here 200 or 300 RPM difference when setting the needle. There are several different optical tachometers available that you aim through the prop arc and it reads the engine RPM. Takes all the guess work out of it. It doesn't even matter if it is an accurate reading of engine RPM, just needs to be a consistant reading so you can get a base line reference on where to set your needle.. Once you get the chance to work with soembody and develope a routine, it will become "routine" for you and help you understand other stuff you will encounter along the way.
    Try other props from different manufactureres, even in the same pitch. You will find a difference, and the tachometer will show it to you.
   Enjoy your vacation! We'll all be waiting for you when you get back and get that Banshee in the air again.
  Type at you later,
    Dan McEntee

[phil c]

The Magnum 32 XLS I have is, for some reason, a much faster running motor than the 36XLS.  Not quite sure why.

[Dick Fowler]

The Magnum 32 XLS I have is, for some reason, a much faster running motor than the 36XLS.  Not quite sure why.

Heavier piston?

[Bradley Walker]

The Magnum 32 XLS I have is, for some reason, a much faster running motor than the 36XLS.  Not quite sure why.

Depending on the hole for the sleeve.

Bigger intake bypasses mean more RPM.

Smaller bypasses limit RPM and create grunt.

[Bill Gruby]

  Brad;
   
    How about some more info on ports, I would like to understant the new motors better? I know nothing about them.


              "Billy G" 

[Shultzie]

Bill, first off let me say that last time I checked I was a fully emancipated adult and as such entitled to make comments without obtaining permission from you. Like me, you're just another pretty face on this forum and I don't believe you have been elected "hall monitor" yet. It was a weak attempt to provide some levity... if you don't like it I suggest you scroll down to the next post.

Rapid Richard...oooooooooooooooooooooooooooooooooooooooooooooooooweeeeeeee! EZ!just breeeeeeeeeeeeeeeeeath!.....Chill....maybe take a Pill? "Toy Airplanes should be fun?" 

[Bill Gruby]

Dick Fowler and "Shultzie"


    Would both of you please accept my apologie. My comment was totally out of line, of course you are a fully emancipated adult and as such completely within your rights to speak your mind , Dick. I am not by any means setting myself up as hall monitor here, thats "Bill Littles' job. At this point in time my mind is completely off the wall.We just welcomed #2 son home two weeks ago from Afghanistan and I am waiting for a connecting flight to Kansas City to see #1 son off to Iraq tomorrow morning. Life at this point is not good.
    AGAIN please accept my apology for my statement, it was out of context for me. If you look back at the reply you will see that I have edited it out. I do not wish to rile anyone because of my thoughts at this time, theey are not really where they should be at this time. Thank-you.

             "Bill Gruby"

[Shultzie]

Dick Fowler and "Shultzie"


    Would both of you please accept my apologie. My comment was totally out of line, of course you are a fully emancipated adult and as such completely within your rights to speak your mind , Dick. I am not by any means setting myself up as hall monitor here, thats "Bill Littles' job. At this point in time my mind is completely off the wall.We just welcomed #2 son home two weeks ago from Afghanistan and I am waiting for a connecting flight to Kansas City to see #1 son off to Iraq tomorrow morning. Life at this point is not good.
    AGAIN please accept my apology for my statement, it was out of context for me. If you look back at the reply you will see that I have edited it out. I do not wish to rile anyone because of my thoughts at this time, theey are not really where they should be at this time. Thank-you.

             "Bill Gruby"

BILL "OUR BROTHA' "G"MAN....I can assure you that 99.99999 of us on this board...know that in NO WAY HAVE U EVER SET YOURSELF UP AS A "HALL MONITOR" KNOW THAT  IT IS AND HAS NEVER BEEN....IN YOUR NATURE!

The many languages of our world, often falls short.....when it comes to communicating our true feelings and understandings and miss understandings are a fact of being.
With that....Bill! U owe me no appolos.
"LOVE ME---LOVE MY TOY AIRPLANES!" takes on an huge dose of understanding at times. As you know I am no stranger to  the pot from time to time...and have ended up in exile over "posilutely-absotively' nuttin!
May we all go...and SIN NO MO'!