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Re: Prop Thrust Angle (Read 6994 times)
Reply #4 - Jul 16th, 2017 at 9:14pm

LASTWOODSMAN   Offline
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I am also looking forward to that missing section ...
LWM
 

OH, I HAVE SLIPPED THE SURLY BONDS OF EARTH ... UP, UP THE LONG DELIRIOUS BURNING BLUE ... SUNWARD I'VE CLIMBED AND JOINED THE TUMBLING MIRTH OF SUN-SPLIT CLOUDS ...
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Reply #3 - May 11th, 2012 at 8:28pm

Sky9pilot   Online
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C.L. Chennault wrote on May 11th, 2012 at 8:14pm:
It seems that I have lost a big section from this and will have to write it in later.  Cry  Thats why post 1 and 2 do not pickup and leave off correctly. There is a section missing. 
Sorry about that.



Come on Boss....where's the missing parts?????   Cheesy Grin Wink Glad to see I'm not the only one who has this problem.... Roll Eyes Embarrassed Lips Sealed Grin Wink

Look forward to reading that missing section.... Cool

Tom
 

If God is your Co-pilot...switch seats...
Your attitude will determine your altitude!- John Maxwell
And ye shall know the truth, and the truth shall set you free. Jn 8:32
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Reply #2 - May 11th, 2012 at 8:14pm

C.L. Chennault   Offline
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It seems that I have lost a big section from this and will have to write it in later.  Cry  Thats why post 1 and 2 do not pickup and leave off correctly. There is a section missing. 
Sorry about that.
 

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Reply #1 - Feb 2nd, 2012 at 7:03pm

C.L. Chennault   Offline
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  Transversely, more turns produce more power, more speed, and whatever thrust angle you have, right or wrong, will come more into play.  If your angle is wrong, it will hit the ground harder and faster. We don't want that. We want to add power and speed AFTER we have control. If you feel like you have a decent handle on it at 50 winds, try 75. Then 100. More power will make the effect of prop thrust angle more prominent. As the power goes up, you will want to fine tune your angle. You need to start slow so that you are in the ballpark before you fine tune. Then it's just a matter of how high and how big YOU decide the circle is.

  The ideal setup is a plane that glides in a perfect circle, and prop thrust pulls it in the same exact circle. To do that, you have to match wing warp, rudder deflection,  and prop thrust. That gives you the most bang for your rubber powered buck. For now, prop thrust is way more consistent to control and adjust. Just remember not to fight your plane. If it likes to go left, go with it. You will see that when you glide. Watch your plane carefully, it will tell you which direction it wants to fly.  

  Just to be fair, I will explain the down side to my technique. If your plane runs out of power BEFORE it lands, it will follow its normal glide path. If your plane glides in a straight line, that's cool. If it goes into straight line glide path mode, 500 feet above the earth, it's not so cool. You might be amazed and dismayed at how far your plane might fly away if it catches just the right air current. That is why folks warp the wings or deflect the rudder a tiny bit. Normally, I don't let my planes go that high, but you might. There is a certain feeling that comes with "Hang Time". The best thing to increase flight time is altitude. I don't like chasing them or getting them out of trees. Even when I do fly outdoors, I like to keep them low and close to me. If your shooting for the heavens, or the record books, you will need every trick in the book. First, we need to get you in the air and be able to fly consistently. That's why I like to steer with prop thrust angle.  

  Remember the rule of 3 degrees down, and 2 degrees right? That's a starting point. YOU will have to adjust YOUR plane for the prop, motor, and wing combo that YOU have. If you get the prop thrust angle just perfect, she will fly pretty much in the gentle circle that you choose. Have fun. Start slow. Work your way up.

  A word about rubber motors. Kit rubber is not always as good as it could be. You can buy good rubber from several places. It's cheap and 10 times better. We are not going into detail on this article, but in a nutshell, rubber motor has three basic power levels. A tightly wound motor has the power phase, cruise phase, and glide phase. It is based on how tightly you wind your motor. Watch this video and you will see the power phase take her to the ceiling pretty quick.  Then it seems to level off and fly. Then it comes back to earth.
  Those are the three phases. In the beginning, you will want to use the lowest end of the cruise phase. Too many turns and she will crash into the rafters. Again, start slow and work your way up.
http://www.youtube.com/watch?v=u5ykVSAkqRE&list=UUXs3LpqZUfFLUiJq483A_aw&index=1...

  What you saw was a motor wound up just barely into the power phase. That motor will easily tale another 200 or 300 turns, but it would have to fly outside. The flight pattern would be the same, but since there are more turns in the power phase, [wound tighter] it would climb much higher before winding down enough to be in cruise mode. For your first few flights, trim your prop thrust angle for cruise. The power phase will take care of itself.

  That's enough for now. I hope this will help. Now, go have some fun.              
« Last Edit: Feb 5th, 2012 at 10:47am by C.L. Chennault »  

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Nov 27th, 2011 at 8:57pm

C.L. Chennault   Offline
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How I Set Prop Thrust Angle.

By Eric McAuley


  Most folks like to have their plane fly in slow, sweet circles. The reason for this, I think, is to see it better and not have to chase it across the county. It is also very handy for indoor flying to keep it off the walls and ceiling.  

  There are three main ways to achieve a circle. One way is to deliberately warp a wing. This is called "washout" or "washin" depending on which way you warp it. The Wright bros. plane was controlled this way. Using a system of cables and such, they had the ability to cause "wing warp" and that made one wing produce more lift than the other. This caused the plane to "bank", { one wing rises higher than the other} thus turning the plane.  

  Another way is to deflect the rudder. This works because air passing the rudder pushes more on one side than the other. Much like a weather vane, or the flute of an arrow. Another good example is when you hold your flattened hand out the window of the car while moving down the road.
 
  Both of those ways are valid and have merit.  You may need to use one or both, in some cases. Try them, if you wish. They may work fine for you, as they work well for many people. The biggest trick is to find what works for you.  

  The way I prefer to make my planes turn is with prop thrust angle. There are other ways, perhaps better ways, but this works for me because it is simple and consistent. You must set the prop at a slight angle to the center line of the airplane anyway. If you are careful, you can use that angle to turn the plane.     

  When your plane is balanced, and gliding, you will most likely notice it has a tendency to fly to one side or the other. That's fine, don't worry about it. Go with it. There are several possible reasons that it does that.  
Could be that:
One wing is shorter than the other. {I have done that.}
One wing is heavier than the other. {Done that too}
Accidentally built in washout.  {Yep}
Air current you are not aware of. {lots of things I am not aware of}
Rudder might not be dead on straight.  {many times}

  For whatever reason, if it's not too severe, its fine.  You can correct it with prop thrust angle. Try as I might, I have yet to build a perfect airplane. These flaws will cause your plane to have a natural tendency to turn one way or the other. It's normal. It's nearly impossible to eliminate completely. Instead of pulling your hair out over it, use it to turn your plane.    

  Here's how it works. As a prop turns, it tries to rotate the plane in the opposite direction. This is called rotational torque. The only thing that stops your plane from flipping over, is the lift provided by the wings. On a plane with a large wing and a small underpowered prop, the problem is not so drastic. On a plane with a small wing and a large, powerful prop, the problem is much more severe.  Don't worry about whether your prop is big or small. The principle is the same and it still works.    

  If you want to see this in real life, hang your plane from a single string by the tail so that the nose is pointed straight down. Wind it up and see what happens as it hangs there. The prop will go one way and the plane the other. With no air going over the wings, it has nothing to counteract the prop torque. Try it once, it's fun.  Cool
  Some folks call this the P-Factor. When the plane is moving, the factor is less and the wings lift counteracts it, but not totally. You can use the remaining P-Factor to turn your plane.

  If you build your plane and mount the prop straight and true on the nose, it will try to turn up and to the left under power. It will keep doing that until it is upside down or hits the ground. Or both. If you mount your prop with 3 degrees down thrust and 2 degrees right thrust, [measured as if you were sitting in the cockpit, facing forward.] it stands a better chance of level flight. The reason for this is that the prop thrust is now pulling and twisting the plane in the opposite direction of the spinning prop. {In a nutshell} We use down thrust because both wings are trying to pull up do to lift. We use right thrust because the plane is trying to bank left, against the prop torque. For the purpose of turning, we will concern ourselves with the right thrust. We will talk about down thrust later. More right thrust equals less left bank.      

  Lets put this into practice. Lets assume that your plane is balanced and the glide is pretty much stable. Set your prop at 3 degrees down and 2 degrees right. Put just a few turns on that rubber motor and try it.{50 or so} Did the flight change?

  If not, try more winds on the motor. Prop torque gets stronger with more turns. The tighter the rubber motor, the faster the prop wants to turn, and thus, more prop torque. And hopefully, a longer stable flight.

  At some point, the prop starts actually pulling the plane and not just riding along. {freewheeling} You will kn
« Last Edit: May 11th, 2012 at 8:01pm by C.L. Chennault »  

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