Trimming for 3D??  
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Trimming for 3D?? - 7/29/2008 6:44:36 PM   
Radical Departure



Posts: 118
Joined: 7/19/2003
From: Fayetteville, AR, USA
Status: offline 		Now I'm confused, which is nothing new. Flying a Dietrich 260 50cc model. The CG as checked on the ground is dead on. In the air, the plane flies upright hands off. Inverted takes just a breath of down, but its practically hands-off. Been doing some great KE's and such. Since I wanted to fine tune it a bit, I used the standard trim chart to try and get there. The alternate method listed is to roll to KE and and use no rudder or add minimal. Well, got the crap scared out of me! Rolled right to KE, no rudder. Before I could even blink the nose dropped very fast, coupled to canopy, started to feed in some rudder but it was too late, and before I knew it the plane was going over my head behind me and closing with the ground fast. A quick release to neutral and quicker move to up elevator saved it with about 5 feet to spare. Closest I've came so far to losing it.

Here's my confusion; if its trimmed upright and inverted, should it not also fly trimmed using the alternative method? Or.. is alternative even the right word? Is it just an odd wording for setting up trim to fly a certain style? I took it to be either or, meaning whichever method used would achieve the same result. Or is that breath of down while inverted greatly magnified during KE w/o rudder? Any clues and insights are greatly appreciated!!


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Radical Departure..
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RE: Trimming for 3D?? - 7/29/2008 9:23:46 PM   
Jake Ruddy



Posts: 3105
Joined: 5/22/2005
From: Bear, DE, USA
Status: offline 		I am not sure I am following this alternate method. There isn't a plane on the planet that will fly on it's side (KE) with no rudder

I am wondering if you are referring to mixing rudder to elevator and rudder to aileron for flat turns? What you do is hit the rudder to make a turn with the rudder only. You mix in generally up el and aileron to keep the nose level and the wings level.

You should be able to fly that way using the sticks first and then you will be able to better program the mix.

I might be wrong in what you are trying to do?


If I am correct.. it's probably not worth doing that step for 3D You probably want to do those mixes in KE to mix out the coupling. You would use the top method more for IMAC so you can correct your lines without dropping or turning.


Hope this helps.

(in reply to Radical Departure)
       Post #: 2

RE: Trimming for 3D?? - 7/29/2008 9:36:23 PM   
Radical Departure



Posts: 118
Joined: 7/19/2003
From: Fayetteville, AR, USA
Status: offline 		Hey Jake,
The trim chart I was using is from 'The Ultimate RC Flight Guide'. I don't have it with me at the moment, I'll have it tomorrow and will post the verbage they use. I suspected as much regarding rudder.. maybe I mis-read it.. I do know it wasn't describing a mix.. it was trimming.. but hey, I'd never tried trimming from KE before so figured what the heck.. as the name implies.. was radical departure from controlled flight..Ha!

_____________________________

Radical Departure..
..from controlled flight

(in reply to Jake Ruddy)
       Post #: 3

RE: Trimming for 3D?? - 7/30/2008 5:02:08 PM   
Radical Departure



Posts: 118
Joined: 7/19/2003
From: Fayetteville, AR, USA
Status: offline 		This was the diagram I was looking at, note the text outlined. Think I'll just stick to standard trim charts..

Trim Diagram

(Sorry for a link instead of an image, got tired of waiting on RCU to upload a 41kb image)



_____________________________

Radical Departure..
..from controlled flight

(in reply to Radical Departure)
       Post #: 4

RE: Trimming for 3D?? - 7/31/2008 5:44:59 PM   
outssider


 

Posts: 1121
Joined: 1/18/2002
Status: offline 		did you notice in the diagrams that it implies that the plane is going to drop in every case !

(in reply to Radical Departure)
       Post #: 5

RE: Trimming for 3D?? - 7/31/2008 6:42:24 PM   
Radical Departure



Posts: 118
Joined: 7/19/2003
From: Fayetteville, AR, USA
Status: offline 		Oh yes, that part wasn't lost on me. What I was unprepared for was how fast it dropped! It went from 2 mistakes high to almost ground level almost before I realised what was happening. Won't be doing that again. I am still curious why one would want to use this method of obtaining CG vs. the 'traditional' method. It would seem that if balanced that way, it would be way off the traditional way. i.e. since my nose dropped so fast, any weight added to the tail to counter would make it tail heavy to the point of being unstable in normal flight.

_____________________________

Radical Departure..
..from controlled flight

(in reply to outssider)
       Post #: 6

RE: Trimming for 3D?? - 8/2/2008 2:30:29 AM   
cloudancer03


 

Posts: 869
Joined: 1/1/2003
From: west hurley, NY, USA
Status: online 		I found that in kn flight the nose will want to drop anyway but as was said its the rate at it falls and if its headed for the ground fast you a very nose heavy plane.for 3D I try to make the planes just a wee bit tail heavy.it makes alpha and other types of manuvers easier as you are nearly always trying to stall the wing..

(in reply to Radical Departure)
       Post #: 7

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