Need CG confirmation on Yak 85"  
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All Forums >> RC Airplanes >> Giant Scale Aircraft - 3D & Aerobatic >> Quique's Aircraft Support >> Need CG confirmation on Yak 85"
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Need CG confirmation on Yak 85" - 6/4/2006 6:59:27 PM   
bart-rennes


 

Posts: 58
Joined: 5/17/2006
From: Gévezé, FRANCE
Status: offline 		Hello,

I'm from europe and have a problem to understand well the QQ documentation on CG.
So, do you take the CG (7 5/8" = 19,36cm) from the end of the wing or from start of the wing, like in the picture show below (orange or green ?).

thank you.

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< Message edited by Rezagh -- 10/23/2006 5:23:39 PM >
       Post #: 1

RE: Need CG confirmation - 6/4/2006 7:05:24 PM   
Rezagh


 

Posts: 1854
Joined: 6/10/2004
From: Rancho Santa Margarita, CA, USA
Status: offline 		Hi There,

Download the new manual at http://www.qqaircraft.com/downloads/manuals/85yakmanual.pdf
Look at page 43.

It's from trainling edge. Basically your green line but from the trailing edge(at Wing Tip). Look at the pic in the manual.

Thank you,
Reza
Quique's Aircraft Support

< Message edited by Rezagh -- 6/6/2006 3:24:30 PM >

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RE: Need CG confirmation - 6/6/2006 10:38:49 AM   
bart-rennes


 

Posts: 58
Joined: 5/17/2006
From: Gévezé, FRANCE
Status: offline 		Found the solution, thank you resa.

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RE: Need CG confirmation - 6/6/2006 10:59:37 AM   
BaldEagel



Posts: 4370
Joined: 10/12/2005
From: Wychling, Kent, UNITED KINGDOM
Status: offline 		WARNING

The C of G on the 85" is measured at the wing tip not the root its taken from the TE of the aileron forward to the LE of the wing, but at the TIP of the wing.

Mike

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RE: Need CG confirmation - 6/6/2006 3:18:10 PM   
Rezagh


 

Posts: 1854
Joined: 6/10/2004
From: Rancho Santa Margarita, CA, USA
Status: offline 		Mike,

Page 43 clearly shows where the CG is measured from. Thank you for your conern.

Reza
Quique's Aircraft Support

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RE: Need CG confirmation - 6/6/2006 5:22:38 PM   
BaldEagel



Posts: 4370
Joined: 10/12/2005
From: Wychling, Kent, UNITED KINGDOM
Status: offline 		Rezagh

Barts pic shows he is measuring from the Root not the tip, I do not think the pic in the manual or the words of explanation are clear and obviously Bart thought the same.

Mike

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RE: Need CG confirmation - 6/7/2006 8:24:52 AM   
bart-rennes


 

Posts: 58
Joined: 5/17/2006
From: Gévezé, FRANCE
Status: offline 		I found the CG, but my problem is that it is centered at the back. Very hard to center it correctly, my motor is a ZDZ50 NG, and the motor weight is more heavy than a DA50 !! I set all batteries just behind the motor...
Normally with a DA50, is it well centered by default ?

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RE: Need CG confirmation - 6/7/2006 8:30:51 AM   
BaldEagel



Posts: 4370
Joined: 10/12/2005
From: Wychling, Kent, UNITED KINGDOM
Status: offline 		Bart

Most guys with a 3lb or under motor have not had a problem with the C of G location, all the batteries are normally on the motor box, you may need to move your batteries rearwards to compensate for your heavier engine.

Mike

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RE: Need CG confirmation - 6/7/2006 8:47:55 AM   
bart-rennes


 

Posts: 58
Joined: 5/17/2006
From: Gévezé, FRANCE
Status: offline 		The problem is that it is not enough heavier on the motor !

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RE: Need CG confirmation - 6/7/2006 9:20:29 AM   
BaldEagel



Posts: 4370
Joined: 10/12/2005
From: Wychling, Kent, UNITED KINGDOM
Status: offline 		Bart

If I understand you correctly, you are saying your battery is not heavy enough to compensate for the weight of the motor, if that is the case I can only suggest you buy two larger capacity batteries, what have you got at the moment?

Mike

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RE: Need CG confirmation - 6/7/2006 3:24:28 PM   
Rezagh


 

Posts: 1854
Joined: 6/10/2004
From: Rancho Santa Margarita, CA, USA
Status: offline 		Bart,

It depends on howmuch your motor sticks out. What size stand off are you using? What's the clearance between back of your prop or spinner plate to the cowl? I'm guessing you might have the motor too close to cowl.

If you can email me more detailed info and I will be more than happy to walk you through it. Some pics also would help.

Thank you,
Reza
Quique's Aircraft Support

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RE: Need CG confirmation - 6/7/2006 3:30:54 PM   
bart-rennes


 

Posts: 58
Joined: 5/17/2006
From: Gévezé, FRANCE
Status: offline 		Thank you, i will post tomorrow when i will get my new muffler which is a little bit more heavy than the one i have now.

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RE: Need CG confirmation - 6/9/2006 12:51:40 PM   
bart-rennes


 

Posts: 58
Joined: 5/17/2006
From: Gévezé, FRANCE
Status: offline 		So i received my new muffle today and test the CG, i put all batteries and all weight i can in the motor box but i need more weight: 0.77 lb at least.
Here a photo of the motor installation with all batteries (not fixed yet).

Thank you for your support.


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RE: Need CG confirmation - 6/9/2006 1:21:31 PM   
exeter_acres



Posts: 6253
Joined: 9/22/2004
From: Johns Creek, GA, USA
Status: online 		are you measureing the CG without the prop, prop bolts and spinner?? they will make a big difference

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RE: Need CG confirmation - 6/9/2006 1:35:11 PM   
bart-rennes


 

Posts: 58
Joined: 5/17/2006
From: Gévezé, FRANCE
Status: offline 		i'm measuring the CG with everything (prop, bolts, spinner,...) the picture is for resa to see motor installation.

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RE: Need CG confirmation - 6/9/2006 1:59:23 PM   
jdavera


 

Posts: 53
Joined: 6/30/2004
From: Houston, TX, USA
Status: offline 		Hi Bart,

I had the same problem than you and I use the idea on the picture below and work for me. The picture is from a extreme flight Yak, but I did it in my Yak 85 QQ, no photo yet.



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RE: Need CG confirmation - 6/9/2006 5:06:31 PM   
BaldEagel



Posts: 4370
Joined: 10/12/2005
From: Wychling, Kent, UNITED KINGDOM
Status: offline 		Bart

make sure your prop driver is approximatly 165mm in front of the engine mounting bulkhead, this will give you the required 37mm clearance between the prop and cowl, I no its a big clearance but it seems its required for prop airflow efficiency.

Mike

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No matter what anyone says 100% is the maximum you can get.

(in reply to bart-rennes)