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Right thrust and 3D - 8/20/2008 9:15:44 PM   
Ernie Misner


 

Posts: 3166
Joined: 7/5/2002
From: Tacoma, WA, USA
Status: offline 		Greetings, just curious as to what others are doing with right thrust or .... lack of on their profiles.

Chatting with a friend confirmed what I'd been thinking, that adding right thrust works against you when inverted, especially high alpha inverted as in harriers.

Don't think I like that!

Thanks,

Ernie
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RE: Right thrust and 3D - 8/21/2008 1:36:39 AM   
Gringo Flyer



Posts: 2249
Joined: 1/16/2004
From: Formosa, ARGENTINA
Status: offline 		I have used the tethrite thrust plates from OMP on 2 profiles and they seem to be just the trick.

I dont understand why right thrust would make a difference with the plane inverted as opposed to upright. The thrust is being changed horizontally not vertically.


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RE: Right thrust and 3D - 8/21/2008 2:01:12 AM   
RC MANIAC119


 

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quote:

ORIGINAL: Ernie Misner

Greetings, just curious as to what others are doing with right thrust or .... lack of on their profiles.

adding right thrust works against you when inverted, especially high alpha inverted as in harriers.

Ernie



Adding Right thrust is almost MANDATORY, on most Profiles. It zero's out your up lines and cuts down on your rudder input, so I don't understand why you feel it works against you. Left or Right....Upright or Inverted, a straight line is a straight line.....Right??

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RE: Right thrust and 3D - 8/21/2008 3:03:54 AM   
XJet


 

Posts: 3724
Joined: 3/31/2003
From: Tokoroa, NEW ZEALAND
Status: offline 		Right thrust *does* work the wrong way when you're inverted and with most profiles you're faced with either just learning to apply the appropriate amount of (usually) left rudder when inverted or ditch the right-thrust and learn to apply left/right as appropriate.

Since a really good 3D flight will see the model flying inverted for about half the flight I'm starting to switch to zero side-thrust and just using the rudder all the time. It becomes second-nature after a while.

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RE: Right thrust and 3D - 8/21/2008 4:44:50 AM   
j.duncker



Posts: 1263
Joined: 6/22/2004
From: Where I park the RV, AK, USA
Status: offline 		I like to set the side thrust so I don't need rudder in the hang.

However I learned on a Limbo Dancer that needed lots of rudder input in the hang so can fly the rudder stick without having to think about it too much.

I suspect that learning on something that needs lots of correctional input might be of benefit in the long run. It is also like banging your head on the wall great when you stop doing it and get something trimmed out.

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RE: Right thrust and 3D - 8/21/2008 9:17:32 PM   
Ernie Misner


 

Posts: 3166
Joined: 7/5/2002
From: Tacoma, WA, USA
Status: offline 		Hey guys thanks for the input!

Why does it work against you when inverted? Because when inverted and at high alpha angles of attack, the right side of the prop circle is still getting more bite or pitch as compared to the left side of the prop arc and STILL wanting to pull the plane to your left just as upright.... only NOW (if you installed right thrust) being inverted the right thrust has become left thrust and the plane is also being pulled to the left. A double whammy when inverted and you've shot yourself in the foot. Ouch!

Edit: ... try it for yourself ... pay attention to all the fightin' you have to do to maintain an inverted harrier with right thrust, then remove the right thrust and see how much more enjoyable it is.

Thanks,

Ernie

< Message edited by Ernie Misner -- 8/21/2008 9:26:17 PM >

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RE: Right thrust and 3D - 8/22/2008 2:14:39 AM   
RC MANIAC119


 

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Status: offline 		DUDE.........there ain't no fighting the Hover....I FLY A MOJO!!!

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RE: Right thrust and 3D - 8/22/2008 6:07:17 AM   
John Wells



Posts: 821
Joined: 12/11/2001
From: Overland Park, KS, USA
Status: offline 		I've become used to adding rudder when doing inverted harriers, but I still think left KE suffers with right thrust.

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RE: Right thrust and 3D - 8/22/2008 9:31:12 PM   
Ernie Misner


 

Posts: 3166
Joined: 7/5/2002
From: Tacoma, WA, USA
Status: offline 		When inverted, right thrust becomes....... left thrust! (but the prop is still spinning the same direction)

Ernie

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RE: Right thrust and 3D - 8/25/2008 3:23:47 PM   
AFSalmon



Posts: 3854
Joined: 5/24/2002
From: Beavercreek, OH,
Status: offline 		I hate to dissappoint you guys but you are not correct with regards to right thrust. Contrary to popular opinions around the RC forums right thrust is not required for engine torque or even P-factor.....which most folks do not fully understand. The only reason you need right thrust is due to the spiralling slipstream caused by the rotating propeller. Becuase most a/c have the vertical stab and rudder above the fuselage versus below, right thrust is required to compensate for more air pressure on the left side of the vertical than the right side. Many factors do come into play like airspeed and prop rpm, as well as angle of attack. Upright or inverted makes no difference whatsoever. There is no perfect solution other than to learn to compensate with the rudder yourself at different speeds and attitudes. 2 1/2 degrees of right thrust is a very good compromise for most prop job planes.



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< Message edited by AFSalmon -- 8/25/2008 5:36:25 PM >

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RE: Right thrust and 3D - 8/25/2008 5:37:39 PM   
AFSalmon



Posts: 3854
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From: Beavercreek, OH,
Status: offline 		Here is a fantastic article written on P-factor, slipstream, and engine torque. There will be a quiz this Friday! haha

http://www.qmfc.org/school/asym.htm


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RE: Right thrust and 3D - 8/25/2008 11:00:50 PM   
3D_Junkie


 

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From: League City, TX, USA
Status: offline 		So what's your suggestion for the OMP 92" hybrid. I did not include right thrust when installing the motor mount. Should I plan on adding washers under the motor mounts or leave it the way it is.

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RE: Right thrust and 3D - 8/26/2008 1:08:44 AM   
AFSalmon



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quote:

ORIGINAL: 3D_Junkie

So what's your suggestion for the OMP 92" hybrid. I did not include right thrust when installing the motor mount. Should I plan on adding washers under the motor mounts or leave it the way it is.


You can certainly add the right thrust with washers under the left side mounts or the more elegant way is to program right rudder with throttle. The more experienced pattern flyers will do this and tailor the curve to the aircraft and setup.

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RE: Right thrust and 3D - 8/30/2008 3:28:38 PM   
JustErik


 

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quote:

ORIGINAL: AFSalmon
You can certainly add the right thrust with washers under the left side mounts or the more elegant way is to program right rudder with throttle. The more experienced pattern flyers will do this and tailor the curve to the aircraft and setup.


I'm not an experienced pattern flyer, but this is exactly what I started doing about 6 months ago. Took out right-thrust and programmed in a rudder mix. It makes mounting the engine a bit easier and helps prevent (or at least minimize) the crushed-wood syndrome caused by the washers. After a little tweaking of the mix, I can't tell any difference in how the plane responds compared to the when it had right-thrust.

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RE: Right thrust and 3D - 8/31/2008 7:23:42 AM   
Ernie Misner


 

Posts: 3166
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From: Tacoma, WA, USA
Status: offline 		Eric, do you have the mix set up so that it kicks in at higher throttle settings, or?

Thanks,

Ernie

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RE: Right thrust and 3D - 8/31/2008 7:28:05 AM   
Ernie Misner


 

Posts: 3166
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