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CG on a MK II twinstar

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lmorgan100(at)charter.net
Guest

Posted: Wed May 16, 2012 11:29 am Post subject: CG on a MK II twinstar

Hi all, I am looking for info on the CG for a MK II Twinstar.  

My measurements were done with the bottom of the wing at 9%  

I am using a weight and balance sheet from a Kolb Firestar but I think the calculations are the same for a MK II Twinstar.  

I am coming up with a CG of 37 % with me in it, I am 175 pounds, Has anyone else had to add weight to the front to  

get the CG within limits ?  

thanks,  

Lee..  

       [quote][b]

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Eugene Zimmerman

Joined: 10 Jan 2006
Posts: 392

Posted: Wed May 16, 2012 5:20 pm Post subject: Re: CG on a MK II twinstar

Lee,



I don't have the specific info you ask for but if you are intending to fly the Mark II two up, I can tell you you do not want any extra weight up front as the elevator on the Mark II is rather underpowered for keeping the nose up at slower flight speeds with two up. If it was up to me I'd fly it as is. I can assure you it will fly just fine with your weight. If you have any doubts just make the first flight with half a tank of fuel, and you will be more than pleased with how she flies.

If it flies like the nose is light and must be held down, adjust the ailerons down a tad.



Gene

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zeprep251(at)aol.com
Guest

Posted: Thu May 17, 2012 4:50 am Post subject: CG on a MK II twinstar

Gene,

 I really believe adjusting the controls to overcome a CG problem does a terrible disservice to a normally good handling airplane.The weight and balance is the way to go.Someone will give you the info you need Lee,How about it Crystal,do you still have that info? 

     G.Aman MK3C

  

     

  

    --

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Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Thu May 17, 2012 5:17 am Post subject: Re: CG on a MK II twinstar

 	  zeprep251(at)aol.com wrote: 	
		  Gene,

 I really believe adjusting the controls to overcome a CG problem does a terrible disservice to a normally good handling airplane.The weight and balance is the way to go. Someone will give you the info you need Lee, How about it Crystal,do you still have that info? 

     G.Aman MK3C  

    -- 	




I think "adjusting the controls to overcome a CG problem" is an oversimplification when it comes to fine tuning the Kolb wing and how it works. The normal procedure is to get the CG right where it needs to be, and then fly it. If it flies like it wants to keep nosing up, you can either put a trim tab on the elevator to hold the nose down, or droop the ailerons. (or flaps) If it flies like it wants to keep nosing down, once again, you can adjust a trim tab to raise the elevators, or raise the ailerons. (or flaps) The airplane responds well to moving the center of lift aft or forwards across the wing and is the accepted way of fine tuning the aircraft for trim once the CG is correct and everything else is suitable.



That is why I modified my flap lever with 3 positions close together at the nominally up position, to fine tune how the airplane behaves in conjunction with the normal MKIII trim system.

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_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing.

Eugene Zimmerman

Joined: 10 Jan 2006
Posts: 392

Posted: Fri May 18, 2012 6:30 am Post subject: CG on a MK II twinstar

G,



How much experience do you have with a Mark II? 

I was not telling anyone how to overcome a CG "problem", since at this point a CG "problem" has not been established. Since there was no mention of any modifications made to the Kolb designed Mark II in question, my assumption is that it is highly unlikely that it has an actual CG "problem".

As a matter of list member information, an in-flight adjustable elevator trim tab is part of the Mark II's standard equipment.

Gene,

On May 17, 2012, at 8:50 AM, Gary Aman wrote:

[quote]Gene,

I really believe adjusting the controls to overcome a CG problem does a terrible disservice to a normally good handling airplane.The weight and balance is the way to go.Someone will give you the info you need Lee,How about it Crystal,do you still have that info? 

G.Aman MK3C

[b]

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zeprep251(at)aol.com
Guest

Posted: Fri May 18, 2012 1:28 pm Post subject: CG on a MK II twinstar

Gene,

 None with a Mk2,but quite a bit with the FS and Mk3.I did the same thing you did,made an assumption.He was looking for cg info and I assumed he wanted to do a weight /balance check, which I would recommend.I would not make trim changes until the CG has been established.It's possible to make an out of balance plane fly level with trim changes but it really screws up the handling,especially in rough air.No offense meant Gene.

  Gary Aman Mk3C 690hrs Jabiru2200A

    --

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cristalclear13

Joined: 19 Sep 2007
Posts: 363
Location: Southeast Georgia

Posted: Tue May 22, 2012 1:59 pm Post subject: Re: CG on a MK II twinstar

 	  lmorgan100(at)charter.net wrote: 	
		  Hi all, I am looking for info on the CG for a MK II Twinstar.  

thanks,  

Lee..  

	




Lee, 

I will go out to the airport and take a look at my W&B and email you.  Sorry for the delay, I haven't been on the forum lately.

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_________________
Cristal Waters
Kolb Mark II Twinstar Rotax 503 DCSI Sept 2007 - sold Sept 2012
Private Pilot Aug 2008
ELSA Repairman for N193Y April 2008
Rotax 2 stroke maintenance April 2009

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