Team RCU - Don Szczur Ask your questions directly to Don Szczur, proffesional pattern pilot

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Old 12-12-2005, 01:08 PM
  #1
BobbyRichardson
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Default CG

How do you know when your CG is just right for IMAC? Is there a manuver that you fly to show it correct?
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Old 12-12-2005, 08:21 PM
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Don Szczur
 
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Default RE: CG

My personal technique, I move it forward if the plane is pitch sensitive. I notice this like during a rolling circle where its really hard to keep the plane from gaining and loosing altitude. Its really sensitive with elevator inputs, and less expo or less elevator throw does not help. Its like you are chasing it and can't keep up. The other way to see is if the airplane just looks like its flying with the tail down, dragging the tail, so to speak.

I have not flown a plane yet that had the CG too far forward. I just move it foward until the stuff above feels better, normally by shifting the batteries forward.

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Old 12-17-2005, 05:53 AM
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stek79
 
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Default RE: CG

Hello Don!!!

Another question about... CG, of course

I find an old post of yours in old rcu site, in which you state your focus CG, and that you put 22% (!!!) downline mix. This % made me thinking alot... [X(] obviously this must be translated in actual surface throw, which you state being about 1/16 of inch. Ok...

The question: with that forward CG, your downlines are ok due to the mix... but the uplines? How can they be straight with such a positive incidence (due to level flight trim I mean). You fix them with down thrust? If so... don't thrust plays a role on low speed on the top of the upline? But in the beginning...

Every time I think about your willingness about sharing your setups, I feel really lucky to be able to read such good infos, since most of the top "guns" don't like to share too much their ideas... A HUGE THANKS DON!!!
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Old 12-18-2005, 12:18 AM
  #4
Don Szczur
 
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Default RE: CG

Hello!

The down mix is offset so it just comes in during the last two clicks of throttle. Its also decoupled from the trim so idle adjustments will not change the mix value.

Yes, I do normally run additoinal down thrust, at least on the Focus. The Brio has about the right amount. Uplines are very locked in at differing speeds.

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Old 12-18-2005, 01:21 PM
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stek79
 
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Default RE: CG

Ok Don... I will try all of that when my pattern plane will be finished, which will happen by some months... For now, really thank you, again.

If you were more near, I would send you a bottle of red Italian wine!

Happy holiday Don!
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Old 05-20-2006, 09:44 AM
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Default RE: CG

hi don !!
im having handling problems with my aircraft
i was wanting to know what is the best position for the C/G when hovering please ??
i've moved it to where the plane is almost too tail heavy , it seems to be ok but
im still having handling problems ,, the plane (modeltech twister) once i get in to a hover
it wants to keep torque rolling on me despite how much aileron i feed in to the plane
im using an APC 12-4 PROP do you think that the prop is too big or should i be using a smaller
diameter prop with more pitch ?[:@]
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Old 05-23-2006, 12:15 AM
  #7
Don Szczur
 
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Default RE: CG

CG has less of an impact during hover. Rear CG makes it hover more easily but less stable on other conventional maneuvers. I normally discount the impact of CG with respect to Torque Rolls. Less prop will provide less air flow on the ailerons. So you want to use a larger diameter prop. Remember you are fighting the torque of the engine so you need large aileron throw to overcome the prop rotation. Often times rudder as well, as in high positive and negative alpha flight. You will note that as you back the plane down in a torque roll it will stop spinning and may actually start to rotate to the right. Any case best of luck with your practicing.

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